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© 2021 Wiley Periodicals LLC.Objective: To evaluate the effect of surface treatments on optical, colorimetric, and surface characteristics of lithium disilicate glass–ceramic. Materials and Methods: Specimens (n = 5, IPS e.max CAD) were randomly allocated to the following treatments: mirror-polished: SiC papers; as-cut: mimicking CAD-CAM milling; ground: 90-120 μm-grit diamond bur; ground polished: ground, finished (46-30 μm-grit diamond bur), polished (diamond cups, brush and diamond paste); ground glazed: ground, glazed; ground polished glazed: association of methods. CIELAB color coordinates were obtained by a spectrophotometer. CIEDE2000 color differences (ΔE00) and the translucency parameter (TP00) were calculated. Light transmittance was assessed with a colorimeter. Surface characteristics (topography and roughness) were analyzed. Statistical differences for each condition and outcome were detected using one-way ANOVA with Tukey's post-hoc test (α = 0.05). Results: TP00 data show statistical reduction after grinding (p < 0.05), which was only restored with polishing (solely or with glazing). ΔE00 shows that grinding results in perceptible variations in color (above 0.81), which were restored after all post-processing protocols (exception to only glaze application in contact with a black background). Light transmittance data corroborated such performance. Polishing and glazing reduced roughness and improved surface topography. Conclusion: Grinding statistically increased roughness, reduced translucency, light transmittance through the ceramic, and resulted on color differences. On contrary, polishing (followed or not by glazing) reduced roughness and enhanced ceramic translucency and light transmittance. Glaze also reduced roughness, but it still presented reduced translucency. The positioning (facing up or down) of the ceramic treated surface influenced the considered outcomes. Clinical Significance: Grinding with diamond burs results in a deleterious impact to the optical, colorimetric and surface characteristics of lithium disilicate ceramic. Thus, polishing (followed or not by glazing) is recommended for optical and topographical enhancements when lithium disilicate monolithic restorations require occlusal adjustments.

Objectives To evaluate different direct restoration techniques on various cavity designs in anterior endodontically treated teeth (ETT). Materials and methods Ninety upper central incisors (n = 90) were selected, endodontically treated, and divided into three groups (n = 30) accordingly to the cavity design: minimal endodontic cavity access (group A), endodontic access + mesial class III cavity (group B), and endodontic access + two class III cavities (group C). Three subgroups (n = 10) were then created accordingly to the restoration technique: nano hybrid composite restoration (subgroup a), glass fiber post + dual-cure luting cement (subgroup b), and bundled glass fiber + dual-cure luting cement (subgroup c). Samples underwent micro-CT scan, chewing simulation, and a second micro-CT scan. 3D quantification (mm3) of interfacial gap progression was performed; then, samples underwent fracture resistance test. Data were statistically analyzed setting significance at p < 0.05. Results Groups A and B showed significantly lower interfacial gap progression compared with group C. Subgroup b performed significantly better compared with subgroups a and c. Improved fracture strength was reported for group C compared with group A, while both subgroups b and c performed better than subgroup a. Conclusions Cavity design significantly influenced interfacial gap progression and fracture resistance. Fiber posts significantly lowered gap progression and improved fracture resistance while bundled fibers only increased fracture resistance. A significant reduction of non-repairable fractures was recorded when fibers were applied. Clinical relevance A minimally invasive approach, conserving marginal crests, should be applied whenever possible. Inserting a fiber post is indicated when restoring anterior ETT, in order to reduce gap progression, improve fracture resistance, and avoid catastrophic failures.

Objective This study aimed to assess the characteristics of different designs of systematic reviews (SRs) registered in the International Prospective Register of Systematic Reviews (PROSPERO) about COVID‐19. Methods The search was performed in the PROSPERO database using the strategy proposed by the database and considered only human studies. The last date of the search was April 27, 2020. Full text of all records was accessed, and data were extracted by a single researcher, which was further double‐checked by another researcher. A descriptive analysis was performed considering record characteristics using tables. Results We included 564 records from which the vast majority were registered as SRs (n = 513, 91%). In general, we found poor reporting and missing or confusing information, since 84% of the records (n = 474) did not report the full search that would be adopted, 16% (n = 90) did not report clearly the databases that would be used, and 49.1% (n = 277) did not report the number of primary outcomes. The main focus of most of the records involved clinical, epidemiological, complication, and laboratory characteristics (n = 173, 30.7%) or the treatment of COVID‐19 (n = 138, 24.5%). Conclusion A large number of SRs about COVID‐19 have been conducted, and many of the assessed records were poorly reported and would be difficult to replicate. Besides, collected data points to an epidemic of redundant reviews on COVID‐19.

Objectives To evaluate the effect of different artificial aging methods on the bond strength of a resin composite associated with a universal adhesive (Scotchbond Universal) used under two etching approaches (self-etch [SE] or etch-and-rinse [ER]) to enamel and dentin substrates. Materials and Methods A total of 96 noncarious human third molars were prepared and randomly divided according to three factors (n = 6): substrate (enamel and dentin), adhesive approach (SE and ER), and aging method (water storage for 24 hours, 6 months, or 1 year; subjected to 10,000, 20,000, or 30,000 thermal cycles; and sodium hypochlorite [NaOCl] storage for 1 or 5 hours). Statistical Analysis Microshear bond strength tests were conducted, and the collected data (MPa) were subjected to three-way analysis of variance (ANOVA) with post hoc Bonferroni tests (p < 0.05) and Weibull analysis. The failure pattern was also evaluated. Results Three-way ANOVA revealed that the factors “substrate” (p = 0.00) and “aging method” (p = 0.00) had a significant effect on the bond strength, but the factor “adhesive approach” did not (p = 0.84). The bond strength in the enamel group for the SE approach was negatively affected under 20,000 and 30,000 thermal cycles. Weibull presented the highest m in the NaOCl storage for the 5 hours group to enamel using the SE and to dentin using ER approaches. Adhesive/mixed failures were predominant for all groups. Conclusion Thermocycling aging (20,000 and 30,000 cycles) significantly reduced the bond strength to enamel using the SE approach. On the contrary, storage with the NaOCl method proved to increase bond strength under the evaluated conditions.

This study aimed to assess root canal irrigants' effect on the bond strength between endodontic sealers and root canal dentin, through a systematic review. The study protocol is available online (h...

OBJECTIVE This study aimed to evaluate whether a master and PhD thesis in Brazilian graduate programs in dentistry can be based on a systematic review (SR). METHODS In this cross-sectional study, we surveyed the coordinators of Brazilian graduate programs in dentistry using a self-administered questionnaire including questions about whether an SR meets requirements for approval of a master or PhD thesis, instructions regarding how to use an SR as the method for a master or PhD thesis, and reasons and barriers that SRs were not recognized as acceptable for a master or PhD thesis. The responses were analyzed descriptively, and tables and graphs were created to summarize the data. RESULTS Among 101 graduate programs invited to participate in the study, 38 (37.6%) returned the questionnaire. Over three-quarters of surveyed programs (n = 30, 78.1%) answered that SRs, in whole or in part, meet the criteria for a master or PhD thesis. Likewise, most programs answered that a master or PhD thesis could be exclusively based on an SR (n = 28, 73.7%). The same number of programs pointed out that one possible reason for not recognizing SRs as a master or PhD thesis is either the lack of SR expertise among committee members (n = 28, 73.7%) or the lack of adequate training of candidates in SR methodology (n = 26, 68.4%). CONCLUSIONS SRs are well accepted as a master or PhD thesis by Brazilian graduate programs in dentistry. Educational initiatives should be encouraged to promote understanding of SR methodology and increase acceptance among graduate programs worldwide.

This study assessed the fatigue performance (biaxial flexure fatigue strength), surface characteristics (topography and roughness) and structural stability (t-m phase transformation) of a Y-TZP ceramic subjected to air-abrasion using new powders (7% and 20% silica-coated aluminum oxide particles) in comparison to commercially available powders. Disc-shaped specimens were manufactured (ISO 6872–2015) and randomly allocated into four groups considering the air-abrasion materials: SiC: commercially available silica-coated aluminum oxide; AlOx: commercially available aluminum oxide; 7%Si and 20%Si: experimentally produced materials consisting of 7% and 20% silica-coated AlOx, respectively. Air-abrasion was executed by a blinded researcher (1 cm distance from the tip to the specimen surface, under 2.8 bar pressure for 10 s). The fatigue tests (n = 15) were performed by the staircase method under a piston-on-three-balls assembly. Topography and roughness assessments (n = 30) of abraded samples and fractography of failed discs were performed. The highest fatigue strength (MPa) was observed for 7%Si (887.20 ± 50.54) and SiC (878.16 ± 29.81), while the lowest fatigue strength for 20%Si (773.89 ± 46.44) and AlOx (796.70 ± 46.48). Topography analysis depicted similar surface morphology for all conditions. However, roughness (μm) was only statistically different between 7%Si (Ra = 0.30 ± 0.09; Rz = 2.31 ± 0.63) and SiC (Ra = 0.26 ± 0.04; Rz = 1.99 ± 0.34). Monoclinic phase grains appeared on Y-TZP surface in a similar content (≈11–12%) for the protocols. Fractography showed all failures starting on air-abraded surface/sub-surface defects from the tensile side. In terms of roughness, phase transformation and fatigue, the new 7% silica-coated aluminum oxide presented similar behavior to the commercially available powder. Increasing silica-coating concentration to 20% did not lead to a gentle air-abrasion protocol.

Purpose To evaluate the substrate masking ability of different ceramic systems used for complete crowns and assess the influence of their association with an opaque resin-based luting agent (OLA). Methods Eleven ceramic groups were tested (n = 10). Bilayer groups were: ZrPc — zirconia + porcelain; CAD-onHT — zirconia + high translucent lithium disilitace; CAD-onLT — zirconia + low translucent lithium disilicate; LDPc — high opaque lithium disilicate + porcelain. Monolithic groups were: TZ — high translucent zirconia; TLS — translucent, zirconia-reinforced lithium silicate; HTLS — high translucent, zirconia-reinforced lithium silicate; LTLD — low translucent lithium disilicate; HTLD — high translucent lithium disilitace; LGC — leucite-reinforced glass ceramic; FC — feldsphatic ceramic. The substrates adopted were resin composites shaded A1 (control), A3.5 and C4; coppery and silvery metals. Color differences (ΔE00) and translucency parameter (TP00) were assessed with the CIEDE2000 formula. ΔE00 was obtained assessing the ceramic influence only and in association with OLA. Results Zirconia groups presented lower ΔE00 and TP00. CAD-on structures associated to OLA led to the lower ΔE00 when tested over metals. ΔE00 for LDPc were similar to zirconia when associated to OLA. Monolithic groups presented significant higher ΔE00 and TP00 compared to bilayers, with ΔE00 below the acceptability threshold only when associated to OLA over substrate shade A3.5. Conclusions Ceramic type and the white-opaque resin-based luting agent presented a significant effect on the substrate masking ability. All the discolored substrates tested are adequately masked with veneered zirconia or with LDPc (preferably associated to OLA). The CAD-on technique associated with OLA improved the masking ability over metallic substrates.

To evaluate the fatigue failure load (FFL), number of cycles for failure (CFF) and survival probabilities of lithium-disilicate (LD) monolithic crowns manufactured by two processing techniques (pressing vs. CAD/CAM) adhesively cemented to a dentin-analogue material, considering two surface treatments (conventional vs. simplified). Surface characteristics (topography, roughness and fractal dimensions) were also assessed. Forty (40) monolithic crowns were manufactured considering two specific processing techniques for each ceramic system: LDCAD – CAD/CAM lithium-disilicate (IPS e.max CAD, Ivoclar Vivadent); LDPRESS – pressed lithium-disilicate (IPS e.max Press, Ivoclar Vivadent). The crowns were adhesively cemented (Multilink Automix System, Ivoclar Vivadent) onto dentin analogue preparations considering two distinct protocols of surface treatments (conventional – hydrofluoric acid etching + silane application [HF+Sil] or simplified – etching with one-step primer (Monobond Etch&Prime, Ivoclar Vivadent) [EP]). The cemented assembly was stored in distilled water at 37 °C for 3 days and fatigue tests were run (step-stress approach: load ranging from 400 to 2000 N, step-size of 100 N, 15,000 cycles/step, 20 Hz). Fractography, surface topography, roughness, and fractal dimension analyses were performed. LDPRESS[EP] group depicted higher FFL, CFF and survival probabilities in comparison to LDCAD groups, regardless of the conditioning method. A tendency of higher Weibull modulus (mechanical reliability) was observed when using [EP] for both LDPRESS and LDCAD. SEM and AFM analysis showed very distinct initial surface patterns for the distinct processing techniques considered (LDCAD with higher fractal dimension and lower roughness than LDPRESS), and both surface treatments distinctly affected these surface characteristics. All failures were radial cracks originating at the ceramic-cement interface. Pressed lithium-disilicate monolithic crowns showed better fatigue performance in comparison to CAD/CAM milled crowns, especially when they were treated with self-etching ceramic primer. The surface treatment with self-etching primer led to similar fatigue performance when compared to hydrofluoric acid plus silane application for the same processing technique, but it tended to provide higher mechanical reliability.

This study aimed to evaluate the effects of various polishing systems associated or not to finishing with diamond burs of lower-grit size on the topography, roughness, and fatigue behavior of a ground yttrium-stabilized tetragonal polycrystalline zirconia (Y-TZP). Disc specimens of Y-TZP (Zenostar T, Ivoclar-Vivadent) were produced (diameter = 15 mm, thickness = 1.2 ± 0.2 mm; ISO 6872-2015) and randomly allocated into 8 groups: [Ctrl] as-sintered; [Gr] ground with coarse diamond bur; [Gr+Eve] grinding + polishing with EveDiacera (2-step polishing system); [Gr+Fin+Eve] grinding + finishing + polishing with EveDiacera; [Gr+Kg] grinding + polishing with Kg Viking (2-step polishing system); [Gr+Fin+Kg] grinding + finishing + polishing with Kg Viking; [Gr+Op] grinding + polishing with Optrafine (3-step polishing system); and [Gr+Fin+Op] grinding + finishing + polishing with Optrafine. Next, surface topography, roughness, phase transformation, fatigue strength (staircase method), and fractography analyses were performed. Grinding changed the surface topography and generated higher roughness (Ra in μm) (1.214); the subsequent finishing/polishing procedures were able to reduce the roughness (0.326–0.839); however, it remained higher than the control [ctrl] group (0.221). All samples subjected to surface treatment presented an increase in m-phase content (8.04–17.46%). In terms of fatigue strength (in MPa), the grinding group (677.36) and polishing/finishing groups (641.66–707.20) presented higher fatigue strength than the control [ctrl] group (592.48). Finishing before polishing had no effect on fatigue strength (645.37–707.20). Grinding altered the Y-TZP surface features and increased their fatigue strength by phase transformation mechanism, while the finishing/polishing procedures promoted surface smoothening, while maintaining high fatigue strengths. Finishing as an additional step before polishing had no effect on roughness reduction and fatigue strength improvements; thus, the finishing procedure might be unnecessary.

Objective: To evaluate the fatigue failure load, number of cycles until failure, and survival probability of adhesively cemented materials with different microstructures (glass-, hybrid- and resin-ceramic) used to manufacture CAD/CAM monolithic restorations. Methods: Disc-shaped specimens (n = 15; Ø = 10 mm; thickness = 1.0 mm) were produced from CAD/CAM blocks as follows: feldspathic (FEL); leucite (LEU); lithium disilicate (LD); zirconia-reinforced lithium silicate (ZRLS); polymer-infiltrated ceramic network (PICN); and resin nanoceramic (RNC). Adhesive cementation was performed onto epoxy discs (dentin analogue- Ø = 10 mm; thickness = 2.5 mm). The cemented assemblies were subjected to fatigue testing using a step–stress approach (400 N–2200 N; step-size of 200 N; 10,000 cycles per step; 1.4 Hz). Fatigue data were analyzed using Kaplan–Meier and Mantel–Cox (log-rank) tests (p < 0.05) and Weibull statistical analysis. Fractographic analysis was also performed. Results: All RNC specimens survived the fatigue test (100% probability of survival at 2200 N; 100,000 cycles) and presented occlusal deformation in response to loading, while all other tested materials failed in distinct loading steps with radial cracks starting from the bonding surface. LD (1146.7 N; 47,333) and ZRLS (1013.3 N; 40,666) materials obtained the highest fatigue failure loads and cycles until failure, meanwhile all PICN specimens failed during the first step (0% probability of survival at 400 N; 10,000). FEL had similar Weibull modulus to LD and ZRLS and higher than LEU for both load and number of cycles outcomes. Significance: The microstructure of adhesively cemented glass-, hybrid- and resin-ceramic CAD/CAM restorative materials influence their response during fatigue testing, which aids in suggesting the best clinical indications.

Made available in DSpace on 2019-10-06T16:12:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-03-01 The aim of this study was to evaluate the effect of sequential usage (milling order) of CAD/CAM diamond burs on the surface roughness, topography and fatigue performance of a lithium disilicate glass-ceramic. Seventy-two (72) ceramic discs (Ø= 13.5 mm; thickness= 1.2 mm; IPS e.max CAD) were milled using four pairs of burs and allocated into three groups (n = 24) according to the milling sequence: 1 through 6 (1−6), 7 through 12 (7−12), and 13 through 18 (13−18). The burs were evaluated under SEM at the different milling stages to depict any degradation generated by the milling sequence. Fatigue performance was assessed by a stepwise approach (initial strength of 20 MPa for 5000 cycles; incremental steps of 20 MPa for 20,000 cycles each until fracture; frequency of 20 Hz) using the ISO 6872:2015 recommendation for piston-on-three-balls biaxial flexure strength tests. Surface roughness, topography analysis and fractography of the failed discs were also performed. Survival analysis (Kaplan-Meier and Mantel-Cox post hoc test) showed that the milling sequence had no effect on the fatigue strength (190 – 201 MPa) or the number of cycles until fracture (174,958 – 180,087 cycles). Ceramic topography and roughness (Ra, Rz and RSm parameters) were similar among the groups, even though SEM analysis depicted CAD/CAM diamond burs degraded over time. Fractography evidenced all failures starting from surface defects introduced by milling at the samples’ tensile side. The sequential usage of CAD/CAM diamond burs (milling order) does not affect the lithium disilicate surface roughness, topography or fatigue performance. MSciD and PhD Post-Graduate Program in Restorative Dentistry (Prosthodontics Unit) São Paulo State University (Unesp) Institute of Science and Technology, São José dos Campos MSciD and PhD Post-Graduate Program in Oral Science (Prosthodontics Units) Faculty of Dentistry Federal University of Santa Maria (UFSM) MSciD Graduate Program in Dentistry Meridional Faculty-IMED MSciD and PhD Post-Graduate Program in Restorative Dentistry (Prosthodontics Unit) São Paulo State University (Unesp) Institute of Science and Technology, São José dos Campos

This study evaluated the fatigue failure load, number of cycles for failure and survival probability of 2nd and 3rd generation yttrium-stabilized zirconia (YSZ) adhesively cemented to a dentin analogue substrate. Disc-shaped specimens (n = 10; O = 10 mm; thickness = 1.0 mm) were produced from four 2nd generation YSZs (Lava Plus, 3M ESPE; Vita In-Ceram YZ-HT, VITA Zahnfabrik; Zirlux FC, Ivoclar Vivadent; Katana ML-HT, Kuraray) and two 3rd generation YSZs (Katana UTML and Katana STML, Kuraray). Each YSZ disc was adhesively cemented (Multilink Automix System) onto its dentin analogue pair (epoxy resin, O = 10 mm; thickness = 2.5 mm). Fatigue tests were conducted through step-stress approach (load ranging from 400 to 2600 N; step-size of 200 N; 20,000 cycles per step, 20 Hz) and the obtained data were analyzed using Kaplan Meier and Mantel-Cox tests. Surface topography and phase transformation (m-, t-, and c-phases) inspections after particle air-abrasion of the YSZs were performed, as well as fractographic analysis of the failed specimens. Second-generation zirconia materials presented higher fatigue failure load, number of cycles for failure, and survival probability than 3rd generation. Similar topographical characteristics of the YSZs could be noted. Phase transformation (t- to m-phase) after YSZ air-abrasion was only observed for 2nd generation materials. All failures started from the surface/sub-surface defects located at the cementation interface. 2nd generation zirconia presented higher load-bearing capacity under cyclic loading than 3rd generation materials.

The purpose of this study was to investigate whether different surface treatments, executed before and after the sintering process, affect the surface characteristics (roughness and morphology) and shear bond strength of computer-aided design–computer-aided manufacturing (CAD–CAM) milled zirconia luted with self-adhesive resin cement onto human dentin. Sixty-four rectangular zirconia slabs (6 × 8.5 × 2.3 mm thickness) were prepared using the CAD–CAM system and randomly distributed into two groups according to the moment of treatment, before and after sintering, and four subgroups according to the surface treatment (n = 8): C (untreated; control), AO (aluminum oxide air abrasion), GB (glass beads air abrasion), and HA (etching with hydrofluoric acid). The samples were evaluated using a confocal laser microscope to assess the surface roughness and morphology. For the shear bond strength test, the milled zirconia was cemented onto dentin slabs using self-adhesive resin cement and submitted to the test in a universal testing machine. Data were submitted to a two-way ANOVA and Tukey test (p

The aim of this study was to characterize the flexural strength and elastic modulus of CAD/CAM resin composite material and to evaluate the influence of different surface treatments and storage conditions on the fatigue behavior of bonded composite crowns. Bars (flexural strength, n= 30; elastic modulus, n= 5) (1.2 × 4 × 12 mm) were produced for three-point bending test and CAD/CAM milled crowns (n= 5) (thickness= 1 mm) adhesively cemented to an epoxy resin substrate for fatigue tests. Bars and crowns were randomly allocated into two “surface treatments”: no surface treatment (CTRL) and air-abrasion with 110 μm Al2O3 particles (AlOx); while the crowns were also subdivided into “aging condition” (baseline - storage for 24 h to 7 days, and aging – storage for 150 days + 25,000 thermal cycles). The three-point bending test was performed according to ISO 6872 and the luted crowns were subjected to step-stress fatigue test (initial load of 200 N; step-size of 50 N; 10,000 cycles per step; 20 Hz). Complementary analysis by Stereomicroscopy and Field Emission Scanning Electron Microscopy (FE-SEM) were performed. The flexural strength and fatigue data were submitted to statistical tests (α= 0.05). The results showed that air-abrasion reduces the flexural strength and the characteristic strength of the resin composite, without modifying its elastic modulus or its structural reliability (Weibull Modulus). Air-abrasion did not influence the fatigue behavior of the cemented crowns. Notwithstanding, a decrease in the survival rate was observed after 445,000 cycles (2,400 N) when subjected to aging at both the CTRL or AlOx conditions. FE-SEM micrographs of the crowns showed that alumina particle air-abrasion treatment can modify the topography of its treated inner surface. Therefore, air-abrasion with alumina powder introduces defects onto the surface of the CAD/CAM resin composite material, decreasing the flexural strength, but without changing its elastic modulus and reliability. Adhesive cementation onto an epoxy resin substrate prevented an influence of the introduced defects on the fatigue performance of the resin composite restoration. Nevertheless, the fatigue behavior may be damaged by aging regimen.

This study evaluated the effect of distinct surface treatments on the fatigue behavior (biaxial flexural fatigue testing) and surface characteristics (topography and roughness) of a 5% mol yttria partially stabilized zirconia ceramic (5Y-PSZ). Disc-shaped specimens of 5Y-PSZ (IPS e.max ZirCAD MT Multi) were manufactured (ISO 6872–2015) and allocated into six groups (n = 15) considering the following surface treatments: Ctrl – no-treatment; GLZ – low-fusing porcelain glaze application; SNF – 5 nm SiO2 nanofilm; AlOx – aluminum oxide particle air-abrasion; SiC – silica-coated aluminum oxide particles (silica-coating); and 7%Si – 7% silica-coated aluminum oxide particles (silica-coating). The biaxial flexural fatigue tests were performed by the step-stress method (20Hz for 10,000 cycles) with a step increment of 50N starting at 100N and proceeding until failure detection. The samples were tested with the treated surface facing down (tensile stress side). Topography, fractography, roughness, and phase content assessments of treated specimens were performed. GLZ group presented the highest fatigue behavior, while AlOx presented the lowest performance, and was only similar to SiC and 7%Si. Ctrl and SNF presented intermediary fatigue behavior, and were also similar to SiC and 7%Si. GLZ promoted a rougher surface, Ctrl and SNF had the lowest roughness, while the air-abrasion groups presented intermediary roughness. No m-phase content was detected (only t and c phases were detected). In conclusion, the application of a thin-layer of low-fusing porcelain glaze, the deposition of silica nanofilms and the air-abrasion with silica-coated alumina particles had no detrimental effect on the fatigue behavior of the 5Y-PSZ, while the air-abrasion with alumina particles damaged the fatigue outcomes.

Statement of problem Severely discolored substrates have been shown to limit the use of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic blocks because they provide insufficient color masking. Purpose The purpose of the in vitro study was to evaluate the effect of a layer of high-value opaque composite resin over discolored substrates to determine its masking ability with CAD-CAM ceramics. Material and methods Six ceramic groups (n=10) were tested. A bilayer group of zirconia and porcelain served as the control. The CAD-CAM monolithic groups were translucent zirconia, zirconia-reinforced lithium silicate, lithium disilicate, leucite-reinforced glass-ceramic, and feldspathic ceramic. Five substrates were used: A1 (used as reference), A3.5, C4, and coppery and silvery metals. The substrates were separated as nonlayered or layered (with flowable or restorative opaque composite resins). The tested luting agents were white, opaque, and A1. Color differences (ΔE00) were assessed with the CIEDE2000 formula. A 2-way ANOVA (α=.05) was used to detect significant differences in ΔE00 among the groups for each substrate. The results were compared with acceptability (1.77) and perceptibility (0.81) thresholds. Results The flowable composite resin layer associated with A1 luting agent ensured ΔE00 lesser the than perceptibility thresholdwith the use of CAD-CAM monolithic ceramics, with the lowest values for zirconia-reinforced lithium silicate in substrates A3.5 (0.53) and C4 (0.32) and for leucite-reinforced glass-ceramic for coppery (0.49) and silvery (0.81) substrates (P Conclusions The application of a flowable opaque composite resin and the use of a shaded luting agent ensure masking with CAD-CAM monolithic ceramics.

Made available in DSpace on 2021-06-25T10:53:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul This study evaluated the influence of distinct substrates on the mechanical fatigue behavior of adhesively cemented simplified restorations made of glass, polycrystalline or polymer infiltrated-ceramics. CAD/CAM ceramic blocks (feldspathic – FEL; lithium disilicate – LD; yttria-stabilized zirconia – YZ; and polymer-infiltrated ceramic network – PICN) were shaped into discs (n = 15, Ø = 10 mm; thickness = 1.0 mm), mimicking a simplified monolithic restoration. After, they were adhesively cemented onto different foundation substrates (epoxy resin – ER; or Ni–Cr metal alloy – MA) of the same shape (Ø = 10 mm; thickness = 2.0 mm). The assemblies were subjected to fatigue testing using a step-stress approach (200N-2800 N; step-size of 200 N; 10,000 cycles per step; 20 Hz) upon the occurrence of a radial crack or fracture. The data was submitted to two-way ANOVA (α = 0.05) to analyze differences considering ‘ceramic material’ and ‘type of substrate’ as factors. In addition, a survival analysis (Kaplan Meier with Mantel-Cox log-rank post-hoc tests; α = 0.05) was conducted to obtain the survival probability during the steps in the fatigue test. Fractographic and finite element (FEA) analyzes were also conducted. The factors ‘ceramic material’, ‘type of substrate’ and the interaction between both were verified to be statistically significant (p < .001). All evaluated ceramics presented higher fatigue failure load (FFL), cycles for failure (CFF) and survival probabilities when cemented to the metallic alloy substrate. Among the restorative materials, YZ and LD restorations presented the best fatigue behavior when adhesively cemented onto the metallic alloy substrate, while FEL obtained the lowest FFL and CFF for both substrates. The LD, PICN and YZ restorations showed similar fatigue performance considering the epoxy resin substrate. A more rigid foundation substrate improves the fatigue performance of adhesively cemented glass, polycrystalline and polymer infiltrated-ceramic simplified restorations. PhD Post-Graduate Program in Oral Science (Prosthodontic Unit) Faculty of Odontology Federal University of Santa Maria Department of Dental Materials and Prosthodontics Institute of Science and Technology ICT/SJC São Paulo State University – UNESP, São José dos Campos Department of Dental Materials Science Academic Centre for Dentistry Amsterdam (ACTA) Universiteit van Amsterdam and Vrije Universiteit Department of Dental Materials and Prosthodontics Institute of Science and Technology ICT/SJC São Paulo State University – UNESP, São José dos Campos CAPES: 001 Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul: 18/2551-0000520-7

This scoping review study aimed to map the evidence about solvents' use for gutta-percha dissolution and removal during endodontic retreatments. The study protocol followed the Joanna Briggs Institute guidelines, available online (https://osf.io/5vy8n/). Reporting was based on PRISMA Extension for Scoping Reviews. We selected dentistry studies that considered the effectiveness of solvents in gutta-percha dissolution in endodontic retreatments and compared their performance to the use of instrumentation techniques without solvents. The search and study screening were performed in PubMed and Scopus databases by two independent researchers. A descriptive analysis considered the study design, method/technique used for obturation, method/technique used for instrumentation during retreatment, solvent solutions tested, exposure time, and main findings. A total of 41 studies were included. Despite that, most studies suggested that solvents' use may complicate root canal cleanliness, regardless of the type of instrumentation used, and facilitate the presence of gutta-percha remnants in the root surface. Thus, the use of solvents should be avoided and its use should only be considered if the previous working length was not possible to access without it. Despite that, high heterogeneity was observed, further studies are still encouraged comparing the performance and effects of different solvents in different clinical scenarios.

Statement of problem The best protocol to restore endodontically treated teeth is still unclear, with many factors to be considered, including the selection and necessity of a post, the type of coronal restoration, the amount of remaining coronal structure, and the type of luting agent. Purpose The purpose of this systematic review was to assess the restorative preferences for endodontically treated teeth between dentists and dental students. Material and methods Survey studies, written in English, of dentists and dental students, which evaluated the use of intracanal posts and other restorative options for endodontically treated teeth, were selected. Searches were performed in the PubMed and SCOPUS databases without time restriction. Screening and data extraction were performed by 2 researchers independently. A standardized outline was used to extract the data (questions related to the theme and the response rate of each question on the survey), and the risk of bias was assessed. Descriptive analysis was performed of the collected information. Results Twenty-five articles were included. Most dentists who answered the surveys reported the time since graduation as 1 to 20 years (40%), and 44% were specialists. The most reported choices concerning the type of posts used were prefabricated posts (45.8%), cast metal posts (16.7%), and both posts (16.7%). The cast metal posts were cited more frequently in surveys published between 1994 and 2010, whereas prefabricated posts, both metal and glass fiber ones, were cited between 2006 and 2019. The preferred luting agent for intracanal posts was resin-based (47%). These choices seem to have been influenced by time and by the level of postgraduate training. Conclusions Restorative preferences related to posts have changed over time, from the use of cast posts to prefabricated ones or the use of both posts and seem to be influenced by experience and postgraduate training.

The aim of the study was to evaluate the effect of a ceramic primer and its increased passive application on the fatigue performance of adhesively cemented lithium disilicate simplified restorations. Ceramic discs (Ø = 10 mm; thickness = 1.0 mm) were submitted to an in-lab simulation of CAD/CAM milling and allocated into 8 groups (n = 15), considering 2 factors: “surface treatment”– PRIMER, only coupling agent application (Monobond N); HF5+PRIMER, 5% hydrofluoric acid and coupling agent; E&P 20s + 40s and E&P 20s+5min, ceramic etching/priming (Monobond Etch & Prime, E&P) for 20 s of active application followed by 40 s or 5 min of passive application, respectively; and “aging condition”– baseline, storage for 24 h to 5 days; aged, storage for 90 days +12,000 thermal cycles. Adhesive cementation (Multilink N) was performed onto epoxy discs (Ø = 10 mm; thickness = 2 mm) and the cemented assemblies were subjected to step-stress fatigue tests (initial load of 200 N; step-size of 50 N; 10,000 cycles per step; 20 Hz). The results showed that the groups had similar fatigue performance in the baseline condition (except for E&P 20s+5min: 940.0 N; 123,000 cycles > PRIMER: 786.7 N; 92,333 cycles). When aged, the PRIMER group presented the worst fatigue performance (480.8 N; 31,154 cycles) compared to the other groups (810.0–840.0 N; 97,000–103,000 cycles). In addition, only the PRIMER treatment showed unstable fatigue performance (baseline > aged). Therefore, ceramic surface treatment promoting micromechanical interlocking and chemical bonds is mandatory for stable fatigue performance of adhesively cemented lithium disilicate restorations. The one-step ceramic primer/conditioner promoted similar fatigue performance to the 5% hydrofluoric acid + coupling agent, but increased E&P etching time did not improve the fatigue behavior.

The aim of this study was to assess the stress/strain in dental implant/abutments with alternative materials, in implants with different microgeometry, through finite element analysis (FEA). Three-dimensional models were created to simulate the clinical situation of replacement of a maxillary central incisor with implants, in a type III bone, with a provisional single crown, loaded with 100 N in a perpendicular direction. The FEA parameters studied were: implant materials-titanium, porous titanium, titanium-zirconia, zirconia, reinforced fiberglass composite (RFC), and polyetheretherketone (PEEK); and abutment materials-titanium, zirconia, RFC, and PEEK; implant macrogeometry-tapered of trapezoidal threads (TTT) and cylindrical of triangular threads (CTT) (ø4.3 mm × 11 mm). Microstrain, von Mises, shear, and maximum and minimum principal stresses in the structures and in peri-implant bone were compared. There was increased stress and strain in peri-implant bone tissue caused by implants of materials with lower elastic modulus (mainly for PEEK and RFC). They also presented higher concentration of stresses in the implant itself (especially RFC). Zirconia implants led to lower stress and strains in peri-implant bone tissue. Less rigid abutments (RFC and PEEK) associated with titanium implants led to higher stress in the implant and in peri-implant bone tissue. The TTT macrogeometry showed a higher stress concentration in the implant and peri-implant bone tissue. The stress/strain in peri-implant bone tissue and implant structures were affected by the material used, where reduced values were caused by stiffer materials. Lower stress/strain values were obtained with cylindrical implants of triangular treads.

Background The aims of this study were to assess whether the previous registration of a systematic review (SR) is associated with the improvement of the quality of the report of SRs and whether SR registration reduced outcome reporting bias. Methods We performed a search in PubMed for SRs in dentistry indexed in 2017. Data related to SR registration and reporting characteristics were extracted. We analyzed if the reporting of 21 characteristics of included SRs was associated with the prospective registration of protocols or reporting of a previously established protocol. The association between prospective registering of protocols, reporting of funding and number of included studies versus outcome reporting bias was tested via multivariable logistic regression. Results We included 495 SRs. One hundred and 62 (32.7%) SRs reported registering the SR protocol or working from a previously established protocol. Thirteen reporting characteristics were described statistically significant in SRs registered versus SRs that were not. Publication bias assessment and Report the number of participants showed the highest effects favoring the register (RR 1.59, CI 95% 1.19–2.12; RR 1.58, CI 95% 1.31–1.92 respectively). Moreover, Registration was not significantly linked with the articles’ reporting statistical significance (OR 0.96, CI 95% 0.49–1.90). Conclusion There is a positive influence of previously registering a protocol in the final report quality of SRs in dentistry. However, we did not observe an association between protocol registration and reduction in outcome reporting bias.

Considering the long time spent in low frequency cyclic fatigue tests, this study aimed to evaluate the influence of loading frequency (2 Hz and 20 Hz) on the flexural fatigue strength (FFS) and on the time and number of cycles to failure of a leucite-reinforced glass-ceramic. Disc-shaped specimens were produced using leucite-reinforced glass-ceramic CAD/CAM blocks (IPS Empress CAD), according to ISO 6872/2015. Two fatigue tests were performed. The FFS (n = 17) was determined by staircase approach at a lifetime of 500,000 cycles, for 2 Hz (control - chewing frequency estimative) and 20 Hz (accelerated approach). To determine the time and the number of cycles to failure in flexural fatigue, discs (n = 20) were submitted to a cyclic loading ranging from 10 MPa to 99 MPa (60% of the monotonic strength), until a maximum of 500,000 cycles. Means, standard deviation and confidence intervals (CI) at 95% for FFS were calculated, whereas statistical differences were detected based on maximum likelihood estimations and overlapping of 95% CIs. Kaplan Meier (α = 0.05) and log rank post-hoc tests were used to analyze the time (in minutes) and the number of cycles to failure in the lifetime test. FFS did not differ significantly between 2 Hz (mean: 78 MPa; 95% CI: 69-88 MPa) and 20 Hz (mean: 84 MPa; 95% CI: 78-90 MPa). Regarding the lifetime test, there was no difference (p = 0.3) in the time to failure for 2 Hz (mean: 13 min; 95% CI: 6-20 min) and 20 Hz (mean: 69 min; 95% CI: 9-128 min). However, the group tested with 20 Hz survived a significantly (p 0.01) higher number of cycles (mean: 82,247 cycles; 95% CI: 11,450-153,044) than the group tested with 2 Hz (mean: 1588 cycles; 95% CI: 779-2397). Therefore, in leucite-reinforced glass-ceramic fatigue strength tests, limited to a lifetime of 500,000 cycles, the use of loading frequencies up to 20 Hz did not influence the FFS estimations when compared to 2 Hz (chewing frequency estimative), and may be an alternative to accelerate data collection in this type of mechanical test. However, in lifetime tests, the use of higher loading frequencies, as 20 Hz, did not save time, since a higher number of cycles was necessary to promote the failure, when compared to 2 Hz.

Statement of problem An intraradicular retainer formed by multiple independent glass fiber filaments was developed aiming to allow better adaptation in flattened root canals; however, the performance of the new posts is unclear. Purpose The purpose of this in vitro study was to compare the bond strength (BS) and adhesive interface quality achieved in flattened root canals restored with conventional glass fiber posts (CFPs) and multifilament glass fiber posts (MFPs). Material and methods The distal roots of mandibular molars with long oval root canals were endodontically treated, and the obturation material was removed and assigned to 2 groups (n=11) according to the type of retainer used: CFP (WhitePostDC#0.5; FGM) or MFP (CometTail#4; Synca). The posts were cemented with self-adhesive resin cement. The specimens were sectioned (2 slices per third). The most cervical slice in each third was used to evaluate the BS, while the adhesive interface in the apical slices was analyzed by scanning electron microscopy. BS data were analyzed by using a multilevel generalized linear model, and adhesive interface SEM data were analyzed by using a multilevel ordinal logistic regression model (α=.05). Results Multilevel regression showed a statistically significant difference for the “type of retainer” factor (P=.001; CFP 2.61 ±1.30>MFP 1.59 ±1.54). No statistically significant differences were found for the “root thirds” factor (P=.346) or for the interaction of both factors (P=.114). The failure pattern was predominantly mixed or adhesive for CFP and adhesive to dentin for MFP. A better adaptation of the restorative material was observed in the cervical third for CFP and in the apical third for MFP (P Conclusions MFP resulted in lower BS values than CFP, with a higher prevalence of adhesive failures to dentin and better adaptation of the adhesive interface in the apical third.

Statement of problem Data comparing the fatigue performance of adhesively luted glass or polycrystalline ceramic systems for computer-aided design and computer-aided manufacturing (CAD-CAM) are scarce. Purpose The purpose of this in vitro study was to evaluate and compare the fatigue performance of monolithic crowns manufactured from glass or polycrystalline CAD-CAM ceramic systems adhesively luted to a dentin analog. Materials and Methods Fifty-four pairs of standardized preparations of dentin analog (NEMA Grade G10) and simplified ceramic crowns of 1.5-mm thickness were obtained with 3 ceramic materials: lithium disilicate (LD) glass-ceramic (IPS e.max CAD); zirconia-reinforced lithium silicate (ZLS) glass-ceramic (Vita Suprinity); and translucent yttrium fully stabilized polycrystalline zirconia (Trans YZ) (Prettau Anterior). The simplified crowns (n=15) were adhesively cemented onto the preparations and subjected to step-stress fatigue test (initial load of 400 N, 20 Hz, 10 000 cycles, followed by 100-N increment steps until failure). Collected data (fatigue failure load [FFL] and cycles for failure [CFF]) were submitted to survival analysis with the Kaplan-Meier and Mantel-Cox post hoc tests (α=.05) and to Weibull analysis (Weibull modulus and its respective 95% confidence interval). Failed crowns were submitted to fractography analysis. The surface characteristics of the internal surface (roughness, fractal dimension) of additional crowns were accessed, and the occlusal cement thickness obtained in each luted system was measured. Results Trans YZ crowns presented the highest values of FFL, CFF, and survival rates, followed by ZLS and LD (mean FFL: 1740 N>1187 N>987 N; mean CFF: 149 000>92 613>73 667). Weibull modulus and cement thickness were similar for all tested materials. LD presented the roughest internal surface, followed by ZLS (mean Ra: 226 nm>169 nm>93 nm). The LD and ZLS internal surfaces also showed higher fractal dimension, pointing to a more complex surface topography (mean fractal dimension: 2.242=2.238>2.147). Conclusions CAD-CAM monolithic crowns of Trans YZ show the best fatigue performance. In addition, ZLS crowns also showed better performance than LD crowns.

To evaluate the effect of different glass-ceramic surface treatments and aging on the fatigue failure load of a lithium disilicate glass-ceramic adhesively cemented to a dentin analogue material.One hundred and twenty (120) disc-shaped lithium disilicate specimens (Ø=10mm, thickness=1.5mm) were produced and randomly allocated (n=20) into 6 groups, considering 2 study factors: "surface treatment" in 3 levels (SIL-silane application only; HF5+SIL-5% hydrofluoric acid etching and silane application; MEP-etching with an one-step ceramic primer), and "storage" in 2 levels (baseline-storage for 7 days; aging-storage for 90 days+12,000 thermal cycles). Ceramic discs were adhesively cemented to discs of a dentin analogue material (Ø=10mm, thickness=2.0mm) following the manufacturers' instructions. The fatigue failure load was determined by the staircase approach (250,000 cycles; 20Hz; initial load=1050N [∼70% of mean load-to-failure]; step size=52.5N [5% of initial load]). Micro-morphologic, fractographic, and atomic force microscope analysis were also performed. Fatigue failure load data were evaluated by one-way ANOVA, Bonferroni and t-tests for independent samples.HF5+SIL presented higher fatigue failure load in both conditions (baseline and aging); MEP presented intermediary mean values, while the SIL group presented the worst performance. All groups had a statistically significant decrease in the fatigue performance after aging.Hydrofluoric acid followed by silane application showed the best fatigue performance for an adhesively-cemented lithium disilicate ceramic. Aging negatively influenced the fatigue performance for all tested groups.

Made available in DSpace on 2018-12-11T17:15:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01 This study aimed to evaluate the effect of etching time and hydrofluoric acid (HF) concentration on the fatigue failure load and surface characteristics of zirconia-reinforced lithium silicate glass (ZLS) ceramic cemented to a dentin-like, fiber reinforced epoxy resin. Ceramic (Suprinity, VITA) (1.0 mm thick) and epoxy resin (2.5 mm thick) discs (10 mm diameter) were produced. The bonding surface of the ceramic samples was nonetched (control group), or etched for 30, 60 or 90 s by 5% or 10% HF. The epoxy resin discs were etched by 10% HF for 30 s followed by the application of an adhesive material (Single Bond Universal, 3M ESPE). Pairs of ceramic/epoxy resin discs were cemented with a dual cure resin cement. The fatigue failure load was determined by the staircase method (500,000 cycles at 20 Hz; initial load = 925 N; step size = 45 N). In 10% HF the etching time was shown to influence the fatigue failure load, which increased as the etching time increased (30 s < 60 s < 90 s), and in 5% HF the fatigue failure load was not shown to be affected by the etching time; the lowest fatigue failure loads were produced in the control group without ceramic etching followed by 10% HF acid etching for 30 s. Topography analysis showed variations based on the etching protocols. All fractures (radial cracks) were shown to originate from defects at the ceramic surface on the cementing interface. For fatigue loading improvements of ZLS ceramic, 10% HF acid etching for 90 s and silanization of the ceramic surface is recommended. PhD Post-Graduate Program in Restorative Dentistry (Prosthodontics Units) Univ. Estadual Paulista (UNESP) Institute of Science and Technology at Sao Jose dos Campos PhD Post-Graduate Program in Oral Science (Prosthodontic Units) Faculty of Odontology Federal University of Santa Maria, R. Floriano Peixoto, 1184 MSciD Graduate Program School of Dentistry Meridional Faculty - IMED PhD Post-Graduate Program in Restorative Dentistry (Prosthodontics Units) Univ. Estadual Paulista (UNESP) Institute of Science and Technology at Sao Jose dos Campos

This study aimed to evaluate and compare the effect of different surface post-processing treatments (polishing, heat treatment, glazing, polishing + heat treatment and polishing + glazing) on the superficial characteristics (micromorphology and roughness), phase transformation and fatigue strength of a Y-TZP ceramic ground with diamond bur. Discs of Y-TZP ceramic were manufactured (ISO:6872-2015; final dimensions of 15mm in diameter and 1.2 ± 0.2mm in thickness) and randomly allocated according to the surface condition: Ctrl - as-sintered; Gr - ground with coarse diamond bur; Gr+HT - ground and subjected to the heat treatment; Gr+Pol - ground and polished; Gr+Pol+HT - ground, polished and heat treated; Gr+Gl - ground and glazed; Gr+Pol+Gl - ground, polished and glazed. The following analyses were performed: roughness (n = 25), surface topography (n = 2), phase transformation (n = 2) and fatigue strength by staircase method (n = 20). All treatments influenced to some extent the surface characteristics of Y-TZP, being that polishing reduced the surface roughness, the m-phase content and improved the fatigue strength; glazing led to the lowest roughness values (Ra and Rz), although it showed the worst fatigue strength; heat treatment showed limited effect on surface roughness, led to complete reversion of the existing m-phase content to t-phase, without enhancing fatigue performance. Thus, a polishing protocol after clinic adjustment (grinding) of monolithic restorations based on polycrystalline zirconia material is mandatory for surface characteristics and fatigue performance improvements.

This study evaluated the effect of contamination with saliva or blood and different cleansing agents on the microtensile bond strength (μTBS) and in situ degree of conversion (DC in situ) of composite-adhesive interface. Sixty-six bovine incisors were ground flat to expose dentin and were randomly assigned to eleven groups (n = 6), according to the contaminant and the cleansing agent. A positive control (without contamination or cleansing agent) was determined. A multimode adhesive in the self-etching form was applied before contamination with blood or saliva. Then, the groups received different cleansing protocols that generated two negative controls (contaminated with saliva or blood and only air dried) and eight experimental groups, washed with water (H2O), ascorbic acid (AscAc10%), hydrogen peroxide 3% (H2O23%) and chlorhexidine 2% (CLX2%). Specimens were restored with composite resin and prepared for μTBS. After 24 h, restored teeth were sectioned and the sticks subjected to the μTBS test (in a universal testing machine at 0.5 mm/min speed). Degree of conversion within the hybrid layer (DC in situ) was evaluated by micro-Raman spectroscopy. Data were analysed using a two-way analysis of variance (ANOVA) and Tukey's test (p 0.05), blood influenced negatively (p = 0.025). However, CLX2% was able to re-establish the values of μTBS and DC in situ (p = 1.0). Weibull regression analysis of μTBS data confirmed the prior mentioned performance. Saliva and cleansing agents did not influence μTBS and DC in situ values, while blood caused them to be significantly decreased. CLX2% was able to reverse the negative effects of blood contamination. In this way, in case of composite-adhesive interface contamination with blood, CLX2% washing was able to reverse the μTBS and DC in situ values.

Made available in DSpace on 2021-06-25T11:02:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-09-01 The aim of this study was to evaluate the effect of in-lab simulation procedures performed on a lithium disilicate ceramic luted to a dentin-analogue material regarding the fatigue performance and topographic changes. Lithium disilicate ceramic (IPS e.max CAD) discs (Ø = 13.5 mm and 1.5 mm of thickness) were produced in different ways: milled in a CAD/CAM system (CAD/CAM – control group); mirror-polished (POL group); produced in-lab and ground with #60 silicon carbide paper (SiC group); with #60 wood sandpaper (WS group); with a fine diamond bur (DB group); or with a CAD/CAM bur adapted in a handpiece with a custom mandrel (MANDREL group). The ceramic discs were adhesively luted (Multilink N) onto dentin analogue discs (Ø = 12 mm and 2 mm of thickness) and fatigue testing (n = 19 discs) was performed by step-stress methodology (initial load of 200 N; step-size of 50 N; 10,000 cycles per step; 20 Hz). Surface roughness and contact angle analysis were also performed. According to Kaplan-Meier and post-hoc Mantel-Cox (log-rank), distinct fabrication methods affected the fatigue performance of bonded glass-ceramic discs (p< 0.001). The CAD/CAM group presented the lowest fatigue failure loads (1250 N) and number of cycles for failure (185,000), while the POL groups obtained the highest results (1752 N; 284,444 cycles). The in-lab groups had intermediate values (1355 – 1526 N; 206,052 – 238,684 cycles). Polished specimens presented the lowest roughness values (Ra = 0.041 μm), while the SiC (1.604 μm), WS (1.701 μm), and MANDREL (1.867 μm) groups showed statistically similar roughness values to the CAD/CAM group (1.738 μm). Despite differences before etching, the contact angle was similar among the milled and simulated groups after etching, except for the polished group. Even with some topographic similarities, the tested in-lab simulation methods were not able to mimic the milled specimens in terms of fatigue findings, leading to distinct magnitude of overestimations of the results. MSciD and PhD Graduate Programs in Oral Science – Prosthodontic Units Faculty of Odontology Federal University of Santa Maria Department of Dental Materials and Prosthodontics Institute of Science and Technology ICT/SJC São Paulo State University – UNESP, São José dos Campos Department of Dental Materials and Prosthodontics Institute of Science and Technology ICT/SJC São Paulo State University – UNESP, São José dos Campos

The present study analyzed the fatigue performance of prefabricated fiber reinforced composite posts (FRC post) with different diameters by means of two different fatigue testing methods. A total of 69 FRC double-tapered posts, presenting 20 mm in length associated with different coronal diameters (1.4, 1.6, 2.0 mm) were embedded with acrylic resin in PVC cylinders, maintaining 6 mm free from the coronal part of the post. The posts of each diameter were submitted to step stress testing (inclination: 45°; initial load: 20 N; step-size: 10 N; cycles per step: 18,000; frequency: 5 Hz) (n = 5) or staircase testing (inclination: 45°; initial load: 60% of the monotonic load-to-fracture reported on existing literature; increment: 10% of the monotonic load-to-fracture reported on existing literature; cycles: 18,000; frequency: 5 Hz) (n = 18). The statistical differences were determined for Kaplan-Meier and Mantel-Cox (Log-Rank) tests for step stress testing and based on confidence interval overlapping for staircase testing. All the failures were analyzed in a stereomicroscope (10 × magnification) after the tests, and representative samples were analyzed by scanning electron microscope (500 × and 1000 × magnification). The FRC post with the wider diameter had greater fatigue failure load in step stress testing (DT1.4–56 N

Objective This study sought to describe the clinical and laboratory procedures and to discuss aspects involved in obtaining satisfactory esthetics on substrates presenting different colors. Clinical considerations This case report describes the clinical and laboratory procedures for obtaining an optimal esthetic result using different ceramic framework materials veneered with feldspathic ceramic over substrates of different colors. Zirconia frameworks were used for darkened substrates and were reinforced with lithium disilicate for substrates with minimal discoloration. The same feldspathic veneering ceramic was applied to provide similar translucency and color for favorable esthetics. Conclusions The materials explored in the present case report presented favorable aesthetic results in masking darkened substrates. Clinical significance Clinicians should consider the condition and color of the substrate when selecting the restorative material for masking such a condition.

Introduction The aim of this study was to identify through a scoping review whether root canal irrigants influence the mechanical properties of endodontically treated teeth, and which properties could be affected. The protocol of this study, available online ( https://osf.io/yc9nb/ ), followed the Joana Briggs Institute guidelines. Reporting was based on PRISMA Extension for Scoping Reviews. Methods We selected studies written in English that evaluated the effect of at least one irrigant on the mechanical properties of endodontically treated teeth. The search and study screening were performed in PubMed and Scopus databases by 2 independent researchers. A descriptive analysis was performed to consider the study design, the characteristics of the irrigants, and the properties tested. Results The initial search yielded 608 citations, of which 66 were included. On the basis of the collected data, the most commonly used solutions were 17% EDTA, 2.5% or 5% sodium hypochlorite, and 2% chlorhexidine, and the most common tested properties were hardness and strength. Alterations in the modulus of elasticity, stress and strain concentration during preparation, and roughness were also assessed. Conclusions The majority of studies corroborated a negative effect of all solutions on the mechanical properties of endodontically treated teeth. Furthermore, increases in the concentration of the solution and in the time of exposure were found to intensify deleterious effects. However, disinfection of the canal is also a crucial factor in endodontic success. Thus, clinicians should consider these factors to mitigate the effects without interfering with antibacterial properties, customizing the choice of the solution to the case in hand.

This study investigated the effect of zirconia surface treatment (air-abrasion with aluminum oxide or tribochemical silica coating) and aging on the fatigue behavior of thin monolithic Y-TZP (yttria-stabilized tetragonal zirconia polycrystal) restorations cemented with 2 types of resin cements, containing or not containing MDP, to a dentin-like substrate. Y-TZP ceramic (Zenostar T, diameter (O) 10 mm, 0.7 mm thick) and dentin-like discs (O 10 mm, 2.8 mm thick) were assigned into eight groups according to three factors: ‘zirconia surface treatment’ (aluminum oxide particles air-abrasion ‘AO’; or tribochemical silica coating via silica-coated aluminum trioxide particles air-abrasion + silanization ‘SC’); ‘MDP-containing resin cement’ (with: Panavia F2.0, ‘MDP’; or without: Multilink Automix, ‘nMDP’); and ‘aging’ (baseline; or aged - 'AG':12,000 thermal cycles + 60 days water storage). Y-TZP intaglio surface was conditioned and dentin-like substrate was etched with hydrofluoric acid prior to bonding. Aging was performed in half of the specimens before the fatigue testing (Staircase, 20 Hz; 250,000 cycles). Fractographic and topographic characteristics were analyzed by stereomicroscope and SEM. Prior to aging, no significant difference was found between the two surface treatments, irrespective to the cement. Samples bonded with resin cement containing MDP had a significant reduction in their fatigue failure load when Y-TZP was air-abraded with aluminum oxide particles and subjected to aging (MDP-AO = 2050.71A; MDP-AO/AG = 1756.67B). Other studied conditions were not affected by aging. Topographic images revealed a rougher surface for aluminum oxide air-abrasion. Fractography supports all failures as a radial crack starting at the Y-TZP intaglio surface. Bonded thin simplified Y-TZP restorations had a high load-bearing capacity, regardless of the studied factors. The MDP-containing resin cement applied on aluminum oxide air-abraded zirconia surface was not enough to maintain the fatigue performance after aging, while higher stability to aging was achieved by treating with the tribochemical silica coating method. When using MDP-free resin cement, the surface treatment and the aging did not impact the fatigue performance.

This study compared the fatigue performance and the stress distribution of endodontically treated molars restored with endocrowns obtained with lithium disilicate glass-ceramic or a polymer-infiltrated ceramic network, both processed by CAD-CAM, and direct composite restorations. Forty-eight human mandibular molars were randomly assigned into 03 groups (n = 16) and restored with endocrowns (LD – lithium disilicate glass-ceramic or PICN – polymer-infiltrated ceramic network) or with direct composite restorations. Fatigue testing followed a step-stress approach (initial maximum load of 200 N and 5000 cycles, incremental step load of 200N and 10,000 cycles/step, being the specimens loaded until failure or to a maximum of 135,000 cycles at 2800 N). The fatigue failure load and number of cycles until failure were recorded and statistically analyzed. Fractographic and finite element (FEA) analyzes were conducted as well. There were no differences in fatigue failure load, number of cycles until fracture and mean survival probabilities among groups. However, indirect endocrowns had higher mechanical structural reliability, and LD restorations lasted more time before start to failing. FEA showed that the stress concentration in tooth tissues was higher for the resin composite, followed by PICN and LD in a decreasing order. Almost all fractures were restricted to the restorative material (without tooth involvement), and origins were identified at occlusal surface. The type of restoration did not influence the fatigue failure load, number of cycles until fracture and mean survival probabilities of the restorative strategies. Despite that, the mechanical structural reliability of endocrowns, especially those made of lithium disilicate, was higher and lasted more time before start to failing.

Made available in DSpace on 2019-08-28T18:55:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2019 This study evaluated the effect of the CAD/CAM burs experience (newer vs older as consequence of the milling sequence) on fatigue failure load (FFL), number of cycles for failure (CFF), and survival rates of lithium disilicate glass-ceramic simplified restorations adhesively cemented to a dentin analogue substrate. Three sets of CAD/CAM burs were used to mill disc-shaped ceramic specimens (1 bur set - 18 milled discs with 10 mm diameter and 1.5 mm thickness), considering the bur experience as a result of the milling sequence to compose the study groups: G1-6 - discs obtained from the 1st to 6th milling of each bur set; G7-12 - specimens from the 7th to 12th milling; G13-18 - discs from the 13th to 18th. Discs of dentin analogue (G10, 10 mm diameter and 2.0 mm thickness) were made to serve as substrate (base material) and randomly assigned into pairs with the respective ceramic discs. Then, the ceramic discs were adhesively cemented onto the dentin analogue substrate, composing a three-layer specimen that mimics a monolithic restoration of a posterior tooth. Specimens were tested under stepwise fatigue approach: frequency = 20 Hz, 5000 cycles at maximum load of 400 N to accommodate the testing assembly, followed by incremental steps of 200 N with initial load ranging from 10 to 1000 N, to a maximum of 20,000 cycles/each step, until the occurrence of failure (radial crack). FFL and CFF were recorded at the end of the testing and subjected to statistical analysis. Supplementary roughness analysis of the milled surface was performed (n = 18) using a contact profilometer. Residual stress after milling and acid etching were accessed via X-ray Diffractometry analysis. FFL and CFF were not affected by increase on bur experience (no statistical differences among groups), despite that, it affected both Ra and Rz parameters (G1-6 had the smoothest surface). The residual stress concentration was negligible (milling did not induce residual stress concentration). It is concluded that the fatigue behavior of adhesively cemented lithium-disilicate glass-ceramic restorations was not influenced by CAD/CAM bur experience (newer vs older as consequence of the milling sequence), and so the residual stress concentration induced by milling was negligible. [de Andrade, Guilherme Schmitt; Diniz, Vandeberg; Datte, Carlos Eduardo; Bottino, Marco Antonio; de Melo, Renata Marques] Sao Paulo State Univ Unesp, Inst Sci & Technol, Dept Dent Mat & Prosthodont, Sao Jose Dos Campos, Brazil [Venturini, Andressa Bonin; Valandro, Luiz Felipe] Fed Univ Santa Maria UFSM, Fac Odontol, Prosthodont Unit, Oral Sci, Floriano Peixoto 1184, BR-97015372 Santa Maria, RS, Brazil [Rocha Pereira, Gabriel Kalil] Merid Fac IMED, Sch Dent, Passo Fundo, RS, Brazil [Amaral, Marina] Universidade de Taubaté (Unitau) , Dept Dent Prosthet Dent [Bastos Campos, Tiago Moreira] Aeronaut Technol Inst ITA, Dept Phys, Sao Jose Dos Campos, Brazil

The effect of root canal preparation technique on microcrack initiation is a controversial issue. This systematic review aimed to assess the role of root canal preparation techniques with different kinematics (manual, rotary, reciprocating, adaptive, self-adjusting file) on microcrack initiation. In vitro and in situ studies comparing the influence of at least two different root canal preparation techniques on the initiation of dentin microcracks were searched in PubMed/MEDLINE and SCOPUS up to June 5, 2018 without language and period restriction. Two authors independently reviewed all identified titles and abstracts for eligibility. Tables were generated to summarize the included studies, and the included studies were assessed for bias. Fifty-four (n=54) articles met the eligibility criteria. The results were classified according to the method used for microcrack evaluation, and most studies that used micro-computed tomography showed no formation of new cracks after root canal preparation. In general, the instrumentation techniques induced microcrack formation when the methods were destructive, irrespective of kinematics. In relation to the apex region, when the preparation working length was set as the root canal length subtracted of 1 mm, the risk of microcrack initiation reduces. The majority of the included studies had low risk of bias for all assessed domains. Our results seem to indicate that the various root canal preparation techniques considered in this study will not cause damage to the dental structure when adequately employed and the proper methodology is applied. Resumo O efeito da técnica de preparo do canal radicular na iniciação e/ou propagação de microfissuras dentinárias é um tema controverso. Essa revisão sistemática teve como objetivo avaliar o papel das técnicas de preparo do canal radicular com diferentes cinemáticas (manual, rotatória, reciprocante, adaptativa e self-adjusting file) na iniciação e/ou propagação de microfissuras dentinárias. Estudos in vitro e in situ comparando a influência de pelo menos duas técnicas diferentes de preparo do canal radicular foram identificados no PubMed/MEDLINE e SCOPUS até 05 de junho de 2018 sem restrição de idioma e tempo. Dois autores revisaram de maneira independente todos títulos e resumos para elegibilidade dos estudos. Tabelas foram criadas para sumarizar os estudos incluídos e os estudos foram avaliados quanto ao risco de viés. Cinquenta e quatro (54) estudos enquadraram-se nos critérios de elegibilidade. Os resultados foram classificados de acordo com o método utilizado para avaliação das microfissuras. A maioria dos estudos que utilizaram micro-tomografia não demonstraram formação de novas microfissuras após preparo do canal radicular. Em geral, técnicas de instrumentação induziram formação de microfissuras quando os métodos de avaliação foram destrutivos, independente da cinemática. Em relação a região do ápice, quando comprimento de trabalho foi definido como o comprimento do canal menos 1 mm, o risco de indução de microfissuras é reduzido. A maioria dos estudos incluídos apresentaram baixo risco de viés para todos os domínios apresentados. Nossos resultados parecem indicar que as diferentes técnicas de preparo do canal radicular não causam danos a estrutura dental quando adequadamente utilizadas e a metodologia adequada é utilizada.

This study evaluated and compared the effects of two glaze application methods (brush and spray) on the fatigue strength and surface characteristics (topography and roughness) of a translucent yttrium stabilized partially tetragonal zirconia polycrystal ceramic (Y-TZP) prior to and after grinding. Disc-shaped specimens of translucent Y-TZP (Vita YZ-HT; Vita-Zahnfabrik) were processed (ISO 6872–2015) and randomly allocated into 6 groups, according to the surface treatments performed on the tensile surface: Ctrl – as-sintered (no treatment); Gr – grinding with a diamond bur (181 μm-grit; #3101G); Br – glaze obtained from a powder–liquid mix and applied by brush (Vita Akzent; Vita Zahnfabrik); Sp – glaze application via spray (Vita Akzent Plus; Vita Zahnfabrik); Gr + Br and Gr + Sp – association of grinding + respective glaze method. Analyses of surface roughness (Ra and Rz), fatigue strength (staircase method), surface topography and fractography were carried out. The as-sintered condition had the smoothest surface, while grinding led to the rougher and more heterogeneous topography. Both glaze application methods showed a potential for topography evenness (smoothening effect), while the glaze spray method led to thinner layers of material, showing a limitation in reducing the roughness compared to the brush method. No deleterious effect on fatigue strength of the Y-TZP could be observed, as the glaze-spray application on the as-sintered surface showed the highest values. Fractography depicted two distinct fracture origin regions: from defects in the surface/sub-surface region for the Ctrl and Gr groups; and at the zirconia-glaze layer interface for Br, Sp, Gr + Br and Gr + Sp. The clinical relevance of this work is that the tested glaze application methods did not damage the fatigue strength of the tested Y-TZP.

Purpose To characterize the effect of two processing techniques (pressing and CAD/CAM — Computer Aided Design/Computer Aided Machining) of lithium-disilicate (LD) based crowns on the microstructure, topography, roughness, fractal dimension, internal and marginal adaptation. Methods One-hundred identical preparations for monolithic crowns were made with dentin analogue material (G10 epoxy resin). One of the preparations was scanned and a monolithic crown in lithium-disilicate was planned in the CAD system. Fifty crowns were milled in a wax pattern and subjected to pressing (IPS e.max Press), while 50 crowns were machined at CAD/CAM (IPS e.max CAD) and posteriorly crystallized. Internal and marginal adaptation were assessed via replica technique at four manufacturing moments (Milled wax pattern; LDPRESS; Milled LDCAD; Crystallized LDCAD) and considering 5 regions (margin, cervico-axial angle, axial wall, axial-occlusal angle and occlusal wall). Complementary analysis considering microstructure and topography, roughness and fractal dimension were performed in Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Results The processing technique resulted in different ceramic microstructure, topography, roughness and fractal dimension, whereas CAD/CAM lead to smoother, more homogeneous but more complex topography features (higher fractal dimension) in comparison to the pressing technique (P Conclusions CAD/CAM and the pressing techniques for manufacturing LD crowns lead to completely different ceramic surface characteristics and affect crown adaptation at the margin and at occluso-axial angle.

To compare the effect of different surface treatments (pre-treatments and bonding agents) on the bond strength between glass-fiber post and composite resin, and the topographic alterations of the treated post surface.Thirty-six glass-fiber blocks (12mm×10mm×8mm) were specifically manufactured for this study and randomly assigned into 12 groups considering two factors: 'pre-treatments' (-cleaning with 70% alcohol; air-abrasion with silica-coated aluminum oxide particles; 35% hydrogen peroxide) and type of 'bonding agent' (no bonding agent; application of Monobond Plus; RelyX Ceramic Primer; Single Bond Universal). After that, 6 cylindrical templates (1mm high×1mm Ø) were fixed on each block, filled with composite resin (n=18) and light-cured. Specimens were stored under 37°C for 24h and microshear tests (wire loop Ø=0.2mm) were performed. Topographic, roughness and failure analyses were also performed.Different surface pre-treatments led to different topographic and roughness alterations; a higher surface alteration was noted after silica particles air-abrasion, while a slight surface alteration in the hydrogen peroxide group and a smooth pattern were observed in the cleaning group. The factors 'pre-treatments' (p0.05), 'bonding agent' (p0.05) and their interaction (p0.05) influenced the bond strength. Silica coating, apart from bonding agent application, or Single Bond Universal application without pre-treatment promoted the highest bond values. The main failure type was adhesive at the resin-post interface.In terms of pre-treatments, silica coating promotes the best bonding performance, but pre-treatments can be dispensable when applying Single Bond Universal.

Objective This study aimed to evaluate the epidemiological and reporting characteristics of systematic reviews (SRs) in dentistry indexed within PubMed during the year 2017. Methods We searched for SRs in dentistry indexed within PubMed in 2017. Study selection was undertaken by two reviewers independently. Data related to epidemiological and reporting characteristics were extracted by one of three reviewers. A descriptive analysis of the data was performed. Characteristics of SRs were analyzed considering all SRs included and subgrouped by dental specialties. In addition, we explored if the reporting of 24 characteristics of treatment/therapeutic SRs was associated with the self-reported use of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement calculating the risk ratio (RR) with a 95% confidence interval for each characteristic. Results 495 articles fulfilled the eligibility criteria. The main specialty considered was Oral Surgery numbering 75 articles. Brazil presented the highest contribution with 117 SRs (23.6%). The reporting quality was variable. Items such as, use of the term “systematic review”, or “meta-analysis” in the title or abstract was well reported. In contrast, the study risk of bias/quality assessment method was not reported in 40.5% of SRs. In addition, only four reporting characteristics were described more often in those SR that reported using the PRISMA Statement. Conclusion A large number of SRs were published in dentistry in 2017 and the reporting and epidemiological characteristics varied among dental specialties. There is a mandatory need to improve the quality of reporting and conduct of SRs in dentistry. Clinical significance Poor reporting and conduction of SRs could generate SRs with imprecise and biased results.

The present study evaluated the fatigue behavior of monolithic translucent zirconia polycrystals (TZ) and lithium disilicate glass-ceramic (LD) bonded to different substrates. Disc-shaped specimens of ceramic materials TZ and LD were bonded to three substrates with different elastic modulus (E) (fiber-reinforced composite (FRC) – softest material, E = 14.9 GPa; titanium alloy (Ti) – intermediary properties, E = 115 GPa; and zirconia (Yz) – stiffest material, E = 210 GPa). The surfaces were treated and bonded with resin cement (disc-disc set-up). Fatigue testing followed a step-stress approach (initial maximum load = 200 N for 5000 cycles, incremental step load = 200 N for 10,000 cycles/step). The fatigue failure load and number of cycles until failure were recorded and statistically analyzed. Fractographic and finite element (FEA) analyzes were conducted as well. TZ ceramic depicted higher fatigue failure load, number of cycles until failure, and survival probabilities than LD, irrespective of the substrate. Moreover, TZ and LD presented better fatigue behaviors when bonded to substrates Ti and Yz in comparison to FRC. FEA revealed lower tensile stresses at restorative material when bonded to stiffer substrates. Fractography showed that the fracture origin started at bottom surface of restorative material (except for TZ bonded to Yz, in which crack initiated at load contact point). Translucent zirconia polycrystals present superior mechanical behavior than lithium disilicate glass-ceramic. The substrate type influences the mechanical performance of monolithic dental ceramics (stiffer substrates lead to better fatigue behavior).

Aim: This study aimed to evaluate how meta-analyses are conducted and reported in dentistry. Methods: We conducted a search to identify dentistry-related Systematic Reviews (SRs) indexed in PubMed in 2017 (from January 01 until December 31) and published in the English language. We included only SRs reporting at least one meta-analysis. The study selection followed the 4-phase flow set forth in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement (PRISMA), and it was independently conducted by two researchers. Data extraction was performed by one of three reviewers, and data related to conducting and reporting of the meta-analysis were collected. Descriptive data analysis was performed summarizing frequencies for categorical items or median and interquartile range for continuous data. Results: We included 214 SRs with meta-analyses. Most of the studies reported in the title that a meta-analysis was conducted. We identified three critical flaws in the included studies: Ninety (90) meta-analyses (43.1%) did not specify the primary outcome; most of the meta-analyses reported that a measure of statistical heterogeneity was used to justify the use of a fixed-effect or random-effects meta-analysis model (n=114, 58.5%); and a great part did not assess publication bias (n=106, 49.5%). Conclusion: We identified deficiencies in the reporting and conduct of meta-analysis in dentistry, suggesting that there is room for improvement. Educational approaches are necessary to improve the quality of such analyses and to avoid biased and imprecise results.

This study evaluated the effect of different protocols of low-temperature degradation simulation on the mechanical behavior (structural reliability and flexural strength), the surface topography (roughness), and phase transformation of a Y-TZP ceramic. Disc-shaped specimens (1.2 mm×12 mm, Lava Frame, 3M ESPE, Seefeld, Germany) were manufactured according to ISO:6872-2008 and divided (n=30) according to the aging protocol executed: “Ctrl” – as-sintered – without any treatment; “Dist Water” – stored at distilled water at 37 °C for 365 days; “MC” mechanical cycling into two steps: First – 200 N, 2.2 Hz for 2.000.000 cycles, Second – 450 N, 10 Hz for 1.000.000 cycles; “Aut” – steam autoclave at 134 °C, 2 bar (200 kPa) for 20 h; “Aut+MC”– Aut and MC methods. Roughness analysis (μm) showed, for Ra parameter, higher statistically significant values for Ctrl 0.68 (0.27), while for Rz parameter, the highest values were observed for Ctrl 4.43(1.53) and Aut 2.24 (0.62). Surface topography analysis showed that none aging method promoted surface alterations when compared to control group. Phase transformation analysis showed that all aging methods promoted an increase in m-phase content (Ctrl: 0.94%, Dist Water: 20.73%, MC: 9.47%, Aut: 53.33% and Aut+MC: 61.91%). Weibull Analysis showed higher statistical characteristic strength values for Aut (1033.36 MPa) and Dist Water (1053.76 MPa). No aging method promoted deleterious impact either on the biaxial flexural strengths or on the structural reliabilities (Weibull moduli). Also, none of the aging methods promoted reduction of Y-TZP mechanical properties; thus the development of new methodologies and the association between mechanical stimuli and hydrothermal degradation should be considered to better understand the mechanism of low-temperature degradation.

Considering the interest of the research community in the fatigue behavior of all-ceramic restorations and the time consumed in low-frequency cyclic fatigue tests, this study aimed to investigate the influence of the loading frequency on the zirconia fatigue strength. The biaxial flexural fatigue strength of Y-TZP discs was determined by the staircase approach after 500,000 cycles. The investigated frequencies were 2 Hz (control-simulation of the chewing activity; n=20), 10 Hz (n=20), 20 Hz (n=20), and 40 Hz (n=21). The fatigue strength data were analyzed using one-way ANOVA and post-hoc Tukey׳s test (α=0.05). Pearson coefficient (r) was calculated to assess the existence of a correlation between fatigue strength and loading frequency. X-ray diffraction analysis was used to determine the relative amount of monoclinic phase under each fatigue test condition. The fatigue strength was significantly higher for 40 Hz group (630.7±62.1 MPa) and did not differ among the groups 2 Hz (550.3±89.7 MPa), 10 Hz (574.0±47 MPa) and 20 Hz (605.1±30.7 MPa). Pearson correlation coefficient indicated a significantly moderate correlation (r=0.57) between fatigue strength and loading frequency. The percentage of monoclinic phase was similar among the groups. Therefore, the use of loading frequencies up to 20 Hz seems a good alternative to expedite the cycling strength fatigue tests in polycrystalline ceramics without significantly changing the fatigue behavior showed by zirconia in tests employing the frequency of the masticatory cycle.

This study evaluated the distinct conditioning effect of the intaglio surface of bonded fully-stabilized zirconia (FSZ) simplified restorations on the mechanical fatigue behavior of the set prior to and after aging. Ceramic disc shaped specimens (O= 10 mm and 1 mm thick) were randomly allocated into 14 groups considering: “surface treatments” (Ctrl: no-treatment; PM: universal primer; GLZ: low-fusing porcelain glaze; SNF: 5 nm SiO2 nanofilm deposition; AlOx: air-abrasion with aluminum oxide; SiC: air-abrasion with silica-coated aluminum oxide; 7%Si: air-abrasion with 7% silica-coated aluminum oxide); and “aging” (baseline: 24 h at 37 °C in water; or aged: 90 days at 37 °C in water + 12,000 thermal cycles). The discs were treated, luted with resin cement onto the dentin analog, subjected to aging or not, and then tested under a step-stress fatigue test at 20 Hz, 10,000 cycles/step, step-size of 100N starting at 200N, and proceeding until failure detection. Fractographic, topographic, surface roughness, contact angle, and atomic force microscopy analyzes were performed. The surface treatments at baseline led to statistically similar fatigue failure loads (953N–1313N), except for GLZ (1313N), which was significantly higher than 7%Si (953 N). Meanwhile, Ctrl had 40% pre-test failures (debonding) after aging, and therefore the worst fatigue performance (notable decrease in fatigue results), while all the other groups presented superior and statistically similar fatigue behavior (973–1271N). In fact, when considering baseline Vs aging conditions, stable fatigue results could only be noted when using surface treatments. In conclusion, internal surface treatments of FSZ ceramic restorations are mandatory for fatigue behavior stability after aging the restorative set, while non-treatment induced unstable results.

This study aimed to evaluate the influence of loading frequency on the fatigue mechanical behavior of adhesively cemented polymer-infiltrated ceramic-network (PICN) and lithium disilicate (LD) simplified monolithic restorations. Thirty (30) disc-shaped specimens (O = 10 mm; thickness = 1.0 mm) of each ceramic material (PICN – Enamic, Vita Zahnfabrik or LD – IPS e.max CAD, Ivoclar Vivadent) were produced and adhesively cemented onto dentin analogue discs made of fiber and epoxy resin material (O = 10 mm; thickness = 2.0 mm). PICN and LD cemented assemblies were randomly allocated into 2 groups (n = 15) according to the loading frequency used for the fatigue testing (20 Hz or 2 Hz), composing the PICN_20, PICN_2, LD_20 and LD_2 testing groups. Fatigue tests were run using the step-stress approach (initial load = 200 N; step-size = 100 N; 10,000 cycles per step) and the collected data (fatigue failure load – FFL and number of cycles for failure – CFF) were analyzed by survival tests (Kaplan Meier and Mantel-Cox) and Weibull analysis. Fractographic analysis of failed specimens were also performed. No statistically significant differences were detected in relation to FFL and CFF between the groups within the same ceramic material (PICN_20: 1127 N/102,667 cycles = PICN_2: 1120 N/102,000 cycles; LD_20: 980 N/88,000 cycles = LD_2: 900 N/80,000 cycles). All failures were radial cracks in the cementation surface. Therefore, the use of a 20 Hz loading frequency shows to be a viable alternative to accelerate cyclic fatigue tests without affecting the fatigue mechanical behavior and the failure pattern of simplified restorations made of lithium disilicate glass ceramic or polymer infiltrated ceramic network bonded to the dentin analogue.

This study aims to evaluate the effect of distinct surface treatments (grinding, polishing and glaze) of the occlusal surface of fully-stabilized zirconia (FSZ) simplified restorations bonded onto epoxy resin on the fatigue behavior of the restorations. Disc shaped specimens of FSZ (IPS e.max Zircad MT Multi) were produced (O = 10 mm and 0.8 mm in thickness) and randomly allocated into 5 groups, considering the factor ‘surface treatment’ of the occlusal surface: Ctrl – as-sintered; Gr – ground with coarse diamond bur; Gr + Pol– grinding + polishing with two-step polishing system; Gr + Gl – grinding + glaze application; Gr + Pol + Gl – grinding + polishing + glaze application. Next, the FSZ intaglio surface was air-abraded with 45 μm aluminum oxide powder for 10 s at 15 mm of distance under 2 bar pressure and the discs were adhesively cemented (Multilink Automix) onto its dentin analogue pair (O = 10 mm; thickness = 2.7 mm). Finally, the step-stress fatigue test was executed (load ranging from 200 to 1300 N; step-size of 100N; 10,000 cycles per step, 20 Hz). In addition, surface topography, roughness, phase transformation and fractography analyses were performed. Grinding altered the topographical pattern introducing defects into the material surface and increasing roughness. Polishing and glaze application led to a smoothening effect, reducing surface defects and statistically decreasing roughness. However, the effect on roughness of polishing and glaze was statistically similar. No phase transformation was observed, thus only cubic and tetragonal phases were detected. No surface treatment had a deleterious effect regarding the fatigue failure load, number of cycles for failure and survival rates. All failures (cracks) started on the bonding surface. Thus, polishing and glaze are indicated to reduce surface roughness, despite not leading to differences in terms of fatigue performance.

This study aimed to evaluate the effect of shading procedures on the fatigue performance and optical properties of an yttria-stabilized tetragonal zirconia polycrystal ceramic (4Y-TZP – stabilized by 4 mol% Y2O3). Disc-shaped specimens were produced at pre-sintered stage and randomly allocated into 5 groups (n=15) considering the shading technique: Ctrl (no pigmentation); Brush 1× and Brush 3× (brushing on 1 or 3 applications, respectively); Immer 2min and Immer 4min (immersion for 2 or 4 min, respectively). Following each pigment application, the specimens were dried in accordance with the manufacturers’ guidelines (15 min in a stove at 70 °C) and sintered in a specific furnace. Biaxial flexural fatigue test followed a step-stress approach (initial strength: 200 MPa; step-size: 25 MPa; 10.000 cycles/step; frequency: 20 Hz). Optical measurements were conducted in a spectrophotometer following the CIEDE2000 parameters. Roughness, topography, crystalline grain size, crystalline phase content and fractography analysis were also performed. The flexural fatigue strength (FFS) and the number of cycles to fracture (CFF) were statistically affected by pigmentation techniques (mean FFS in MPa/mean CFF): Ctrl (446.7/105,619) > Brush 1 × (436.7/102,854) ≥ Brush 3 × (405.0/89,962) ≥ Immer 2 min (395.0/85,103) ≥ Immer 4 min (383.3/81,382), although the exposure intensity (increase in number of applications or in application time) to the pigment had no effect (Brush 1 × = Brush 3 × ; Immer 2 min = Immer 4 min). Regarding optical properties, shading techniques similarly affected translucency and opalescence parameters, regardless of the exposure intensity to the pigment (Brush 1 × = Brush 3 × = Immer 2 min = Immer 4 min > Ctrl), whereas the exposure intensity to the pigment only promoted relevant alterations in the color change parameter (ΔE00) for the brushing technique (Brush 3 × > Brush 1 × ). No difference was observed in crystalline phase content, topographic pattern or roughness, although an increase in the zirconia grain size could be detected. Thus, the shading technique might affect the fatigue behavior and promote optical changes in a 4Y-TZP ceramic.