Search

Statement of Problem: The trueness and precision of intraoral scanners (IOSs) and the effect of intracoronal restorations have been reported. However, studies addressing the accuracy of IOSs in reproducing different complete coverage onlay preparation designs are lacking., Purpose: The purpose of this in vitro study was to evaluate the influence of complete coverage onlay preparation design and intraoral scanning devices on the accuracy of digital scans in terms of trueness and precision., Material and Methods: Three preparation designs on the mandibular first molar were considered: a traditional preparation design with isthmus reduction (IST), a traditional preparation design without isthmus reduction (wIST), and simplified nonretentive preparation (nRET). Digital scans of epoxy resin mandibular arch reference models of the preparations (containing second premolar, first molar, and second molar) were obtained by using 3 IOSs (iTero Element 2 [ELE], TRIOS 3 [TRI], and Primescan [PRI]) (n=10). Trueness (μm) and precision (μm) were analyzed by superimposing the digital scan on the digital reference models obtained with a high-accuracy industrial scanner (ATOS Core 80) in a tridimensional metrology software program. Accuracy was quantified by the absolute deviation (μm). Local and overall mean positive and negative deviations for trueness were also obtained. Data were analyzed by using the Kruskal-Wallis and Dunn tests with a statistical software program (α=.05)., Results: The nonretentive preparation groups obtained higher trueness (3.8 μm) and precision (2.7 μm) than the IST and wIST groups (trueness=7.5 to 6.3 μm, precision=5.5 to 4.6 μm). Trueness values were lower with ELE×IST (16 μm), followed by ELE×wIST (13 μm), and PRI×IST (7.8 μm). In general, no difference was found between PRI and TRI scanners (6.3 to 5.9 μm), with lower performance for ELE (13 μm). Positive deviations were higher on the proximal box of the IST and wIST preparation and on the occlusal box of the IST group. Negative deviation was higher on the ELE×IST occlusal box., Conclusions: Different intraoral scanners and preparation designs influenced the accuracy of digital scans. A more complex preparation such as IST and wIST showed higher deviation. The iTero Element 2 scanner exhibited higher deviation for both trueness and precision., (Copyright © 2022 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objectives:  This article evaluated the effect of substrates rigidities on the post-fatigue fracture resistance of adhesively cemented simplified restorations in lithium disilicate glass ceramic., Methods:  Precrystalized computer-aided design/computer-aided manufacturing ceramic blocks were processed into disc-shaped specimens ( n  = 10, Ø  = 10 mm), mimicking a simplified restoration at two thicknesses (0.5 and 1.0 mm). Thereafter, the discs were cemented onto different base substrates (dentin analogue [control], dentin analogue with a central core build-up of resin composite [RC], or glass ionomer cement [GIC]). The specimens were subjected to mechanical cycling in a chewing simulator (100 N, 1 × 10 6 cycles, 4 Hz) and then subjected to thermocycling aging (10,000 cycles, 5/37/55°C, 30 seconds). After the fatigue protocol, the specimens were loaded until failure (N) in a universal testing machine. Finite element analysis calculated the first principal stress at the center of the adhesive interface., Results:  The results showed that "restoration thickness," "type of substrate," and their interaction were statistically significant (one-way analysis of variance; p  < 0.001). Regardless the restoration thickness a higher fracture load was observed for specimens cemented to dentin analogue. Among the base materials, RC build-up presented the highest fracture load and lower stress magnitude for both restoration thicknesses in comparison with GIC build-up. The 0.5-mm restoration showed higher stress peak and lower fracture load when submitted to the compressive test., Conclusion:  More flexible base material reduces the fracture load and increases the stress magnitude of adhesively cemented lithium disilicate restorations regardless the ceramic thickness. Therefore, more rigid substrates are suggested to be used to prevent restoration mechanical failures., Competing Interests: The authors declare no conflict of interest., (The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/).)

Objective: To compare 2 different resin composites and 2 adhesive systems used in a new restorative protocol (partial restoration) to treat non-carious cervical lesions associated with gingival recession type 1 (RT1)., Material and Methods: Eighty combined defects (CDs) were treated with a partial restoration and periodontal plastic surgery for root coverage. The CDs were randomly assigned to one of the following groups: NP + TE (n = 20), nanofilled composite and 2-step total-etch adhesive system; NP + UA (n = 20), nanofilled composite and universal adhesive system; MH + TE (n = 20), microhybrid composite and 2-step total-etch adhesive; MH + UA (n = 20), microhybrid composite and universal adhesive. Restorations were assessed using the United States Public Health Service (USPHS) criteria at 1 week (baseline) and 6, 12, and 24 months. Survival rate, periodontal parameters, dentin hypersensitivity (DH), and aesthetics were also evaluated., Results: After 24 months, only the MH + TE group did not lose any restoration, with no significant differences between groups. For surface roughness parameter, MH presented 83.3% of the restorations scoring Bravo, whereas NP presented 48.5% of the restorations scoring Bravo. All groups presented restorations with marginal discoloration. All periodontal parameters behaved similarly, regardless of the restorative material. All groups presented significant reductions of dentin hypersensitivity and improved aesthetic perceptions (p < 0.05)., Conclusion: Both resin composites and adhesives tested can be combined for partial restorations to treat CDs., Clinical Relevance: This new restorative-surgical protocol to treat CDs presents satisfactory outcomes. The partial restorations can be successfully executed with both combinations of adhesives and resin composites evaluated in this investigation. TRN : ClinicalTrial.gov: NCT03215615; registration date July 12, 2017., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

This study evaluated the effect of resin cement coating with high and low viscosities on the flexural fatigue strength of machined lithium disilicate glass-ceramic. Discs (IPS e.max CAD; Ivoclar Vivadent) were prepared and divided according to the surface condition (machining [M]-CEREC inLab; and polishing [P]-laboratory procedures), resin cement coating (with or without), and cement viscosity (high [H] and low [L]). The ceramic bonding surface was etched/primed by a one-step primer application followed by resin cement application (Variolink N base + high or low viscosity catalyst; Ivoclar Vivadent). Biaxial flexural fatigue strength was evaluated on a piston-on-three-ball set by the step-test method (n = 15) (initial stress: 60 MPa; incremental steps: 20 MPa; 10,000 cycles/step, at 20 Hz). Weibull statistics were used for fatigue data. Contact angle, topographic, and fractographic analysis were also performed. Machining produced statistically lower contact angle than polishing and a significant detrimental effect on the fatigue behavior (σ 0 M = 247.2 [246.9-268.3]; σ 0 P = 337.4 [297.8-382.4]). Machined groups followed by resin cement coating (σ 0 MH = 297.9 [276.0-321.5]; σ 0 Ml = 301.2 [277.1-327.4]) behaved similarly to the polished and coated groups (σ 0 PH = 342.0 [308.9-378.5]; σ 0 PL = 357.3 [324.7-393.1]), irrespective of the cement viscosity. Therefore, cement coating has able to revert the detrimental effects of the machining on the fatigue strength of lithium disilicate glass-ceramic. High and low viscosity cements behaved similarly in the improvement of CAD-CAM lithium disilicate fatigue strength., (© 2022 Wiley Periodicals LLC.)

Statement of Problem: Various strategies have been proposed to reduce the cement space of foundation restorations for endodontically treated teeth. However, they may add more operative steps, or the dentist must keep different sizes of drills and posts in stock. A 2-piece universal adjustable post system has been developed to overcome this problem, but whether the system has acceptable fatigue survival performance is unclear., Purpose: The purpose of this in vitro study was to evaluate the fatigue survival and stress distribution of endodontically treated teeth without a ferrule and restored with different glass fiber post strategies versus a recently introduced universal 2-piece fiber post system., Material and Methods: Bovine incisor roots were randomly assigned to 3 groups as per the post used (n=13): adapted glass fiber post with post space preparation of the same size, composite resin-custom glass fiber post (CTM), and universal 2-piece glass fiber-reinforced composite resin post (UNI). The posts were adhesively luted, the composite resin core was added, and a composite resin crown was produced with computer-aided design and computer-aided manufacturing (CAD-CAM), and then adhesively luted to each core. A fatigue test was performed with the stepwise stress method (10 000 cycles/step; 20 Hz; load=100 N to 750 N; step=50 N) until fracture, and the failure mode analyzed. The stress distribution was evaluated by finite element analysis with the maximum principal stress criteria by following the parameters of the in vitro test. The solids were considered homogeneous, linear, and isotropic, except for the glass fiber post (orthotropic), and a load of 450 N at 30 degrees was applied. The fatigue failure load and the number of cycles for failure were analyzed with Kaplan-Meier and Mantel-Cox (log rank test) (α=.05). The finite element analysis results were analyzed with colorimetric graphs., Results: The highest fatigue failure load and the number of cycles for failure were found in the UNI system, whereas the lowest results were found in the CTM group. All groups exhibited repairable failures. The finite element analysis showed the lowest stress in root dentin in the UNI system. The CTM system had the largest stress regions at the dentin and dentin-core interface., Conclusions: The use of a 2-piece universal glass fiber post system resulted in more fatigue behavior compared with composite resin-custom glass fiber posts., (Copyright © 2021 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Introduction: Deep margin elevation (DME) is an emerging technique attempting to minimize the need for surgical procedures (i.e., crown lengthening [CL]), deliver indirect restorations in one clinical session and reduce overall treatment time. The present study evaluated the impact of DME upon periodontal measurements based exclusively on human studies., Methods: A literature search was performed by two independent reviewers in several databases including PubMed, EMBASE, and Cochrane Central up to March 2022. This review searched for randomized human trials, cohort (prospective/ retrospective) and/or case series studies using DME, reporting periodontal (i.e. marginal bone levels [MBL], probing depths [PD], bleeding on probing [BoP], recession [REC], clinical attachment level [CAL]), and the type of approach (non-surgical or surgical) with at least ⟩3 months of post-operative outcomes., Results: None of the included studies reported MBL, REC or CAL, and thus, results were limited to PD and BoP. BoP was increased when the distance between restorative margin and alveolar bone was approximately ⟨2mm. Non-surgical and surgical DME approaches led to different outcomes in PD (0.26±0.77mm vs -0.39±0.85mm) and BoP (31.50% vs -22.33%)., Conclusions: Limited findings of the present systematic review can be drawn and thus, the impact of DME upon the periodontium remains inconclusive., (Copyright© 2023 Dennis Barber Ltd.)

Objectives: The aim of this study was to compare the effect of three different access cavities on the tissue removal, deflection, fracture resistance, and stress distribution of extracted maxillary central incisors., Materials and Methods: Forty human maxillary central incisors were randomly assigned in four experimental group (n = 10) including conservative access cavity "CAC," traditional access cavity "TAC," invasive access cavity "IAC," and without access cavity (control group). Cone-beam computed tomography "CBCT" scans were used to evaluate the tissue removal during the different access cavities. All specimens were restored with composite resin (Admira Fusion, Voco, Cuxhaven, Germany) and embedded in acrylic resin blocks after simulating the periodontal ligament using red wax, then the specimens were submitted to the deflection test applying a load of 250 N and to the load-to-fracture test after artificial aging in a mechanical cycling machine (150 N, 5 × 10 6 cycles, 10 Hz). Lastly, stress distribution was assessed by three-dimensional finite element analysis (3D-FEA), simulating the specimens restoration by two types of composite resins of low and high elastic modulus (8 and 18 GPa respectively) after the access cavities. The data were submitted to Shapiro-Wilk and KS normality tests. Then, they were analyzed by one-way ANOVA and Tukey tests with a significance level (α ≤ 0.05)., Results: CBCT scans showed a significant difference of worn tissues in CAC and TAC when compared to the IAC (P < 0.0001). In deflection test, CAC showed lower deformation values than the TAC and IAC. Load-to-fracture test presented no significant difference among the three experimental groups (P = 0.6901). 3D-FEA showed that the more conservative the access cavity, the higher the stress magnitude., Conclusions: CAC promote less worn tissue; however, this does not improve the stress distribution or fracture resistance of endodontically treated maxillary incisors., Clinical Relevance: Clinicians should reconsider the pros and cons of the conservative access cavity., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Objectives: This study evaluated the effect of deep margin elevation (DME) and restorative materials (leucite-reinforced glass-ceramics [C] vs. indirect resin composite [R]) on the fatigue behavior and stress distribution of maxillary molars with 2-mm deep proximal margins restored with MOD inlay., Methods: Fifty-two extracted human third molars were randomly assigned into four groups (n = 13): C; DME + C; R; and DME + R. Inlays were fabricated in CAD-CAM and bonded to all teeth. The fatigue behavior was assessed with the stepwise stress test (10,000 cycles/step; step = 50 N; 20 Hz; initial load = 200 N). Fatigue failure loads and the number of cycles were analyzed with 2-way ANOVA and Tukey's test (p < 0.05) and Kaplan-Meier survival plots. The stress distribution was assessed with finite element analysis. The models were considered isotropic, linear, and homogeneous, and presented bonded contacts. A tripod axial load (400 N) was applied to the occlusal surface. The stress distribution was analyzed with the maximum principal stress criterion., Results: For fatigue, there was no difference for DME factor (p > 0.05). For the material factor, the load and number of cycles for failure were statistically higher in the R groups (p < 0.05). The finite element analysis showed that resin composite inlays concentrated more stress in the tooth structure, while ceramic inlays concentrated more stress in the restoration. Non-reparable failures were more frequent in the resin composite inlays groups., Conclusions: DME was not negative for fatigue and biomechanical behaviors. Resin composite inlays were more resistant to the fatigue test, although the failure mode was more aggressive., Clinical Significance: DME does not impair mechanical behavior. Resin composite inlays failed at higher loads but with a more aggressive failure mode., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Objectives: To make an in vitro assessment of fracture resistance of weakened and non-weakened teeth receiving intraradicular reinforcement using Rebilda bundled glass fiber-reinforced composite posts (GT), Rebilda conventional glass fiber posts (RP), or both systems combined (GT + RP)., Materials and Methods: Eighty sound bovine incisors were prepared and divided randomly into eight groups as follows: (a) nWnR: without simulating weakness, and without intraradicular reinforcement; (b) WnR: simulating weakness, but without intraradicular reinforcement; (c) nWGT: without simulating weakness, but with GT; (d) WGT: simulating weakness, and with GT; (e) nWRP: without simulating weakness, but with RP; (f) WRP: simulating weakness, and with RP; (g) nWGTRP: without simulating weakness, but with GT + RP; (h) WGTRP: simulating weakness, and with GT + RP. The specimens were subjected to the load-to-fracture test using the DL-2000MF universal testing machine. The finite element method assessed the mechanical behavior and stress distribution in endodontically treated teeth., Results: The groups nWGTRP and WGTRP presented the best results in the load-to-fracture test, with the former being better than the latter, but with no statistically significant difference (P > 0.05). However, there was a significant difference between these and the other groups (P < 0.05), except for nWRP. Stress distribution inside the canal wall was different among the groups, with promising mechanical behavior for nWGTRP and nWRP., Conclusions: The Rebilda conventional fiber post (RP), combined with the Rebilda bundled glass fiber-reinforced composite post (GT) improves the resistance and stress distribution of immature teeth., Clinical Relevance: Longitudinal fracture is less frequent in teeth restored with GT and RP posts., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Evidence regarding the effect of the onlay preparation design for different CAD/CAM restorative materials considering the preservation of cusps is lacking. Molars were 3D-modeled in four preparation designs for onlay restoration: traditional design with functional cusp coverage (TFC), non-retentive design with functional cusp coverage (NFC), traditional design with non-functional cusp coverage (TNFC) and non-retentive design with non-functional cusp coverage (NNFC). The restorations were simulated with two CAD/CAM restorative materials: LD-lithium disilicate (IPS e.max CAD) and RC-resin composite (GrandioBloc). A 100 N axial load was applied to the occlusal surface, simulating the centric contact point. Von Mises (VM) and maximum principal (Pmax) stress were evaluated for restorations, cement layer and dental substrate. The non-retentive preparation design reduced the stress concentration in the tooth structure in comparison to the conventional retentive design. For LD onlays, the stress distribution on the restoration intaglio surface showed that the preparation design, as well as the prepared cusp, influenced the stress magnitude. The non-retentive preparation design provided better load distribution in both restorative materials and more advantageous for molar structure. The resin composite restoration on thenon-functional cusp is recommended when the functional cusp is preserved in order to associate conservative dentistry and low-stress magnitude.

Prefabricated glass fiber-reinforced composite posts have been widely used because of their esthetic properties and favorable biomechanical behavior; however, because they are prefabricated, they may not adapt to the anatomy of all root canals. This case report describes a procedure for restoring teeth with a custom, 1-piece, fiber-reinforced composite post and core fabricated using computer-aided design/computer-aided manufacturing (CAD/CAM). The excellent adaptation of this custom endodontic post enables the use of a thinner, homogenous cement layer; in addition, it eliminates the need to construct a composite resin core build-up. Although more clinical and in vitro studies are needed to better define the appropriate clinical protocols and assess various materials, CAD/CAM technology allows post and core restorations to be manufactured in a predictable and simplified way., Competing Interests: The authors report no conflict of interest pertaining to any of the products or companies discussed in this article.

The aim of this study was to evaluate the effect of biologically oriented preparation technique on the stress concentration of endodontically treated upper central incisors restored with zirconia crown (yttria-stabilized zirconia polycrystalline ceramic) through finite element analysis (FEA). Four models of maxillary central incisors containing enamel, dentin, periodontal ligament, cortical and medullary bone were created in CAD. Each model received a polymeric core-build up with nanofilled dental resin composite. The evaluated models were SM-preparation in shoulder 90°; CM-chamfer preparation; BOPT-biologically oriented preparation technique and BOPTB-BOPT preparation 1 mm below the cement-enamel junction. All models received zirconia crowns (5Y-TZP), fiberglass post and 1 mm ferrule. The models were imported into the analysis software with parameters for mechanical structural testing using the maximum principal stress and the tensile strength as the analysis criteria. Then, load of 150 N was applied at the cingulum with 45° slope to the long axis of the tooth, with the fixed base for each model. The type of marginal preparation affected the stresses concentration in endodontically treated teeth and in the zirconia crown margin. Considering the stress magnitude only, BOPT is a viable option for anterior monolithic zirconia crowns; however, with the highest stress magnitude at the restoration margin.

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., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The loss of dental structure caused by endodontic treatment is responsible for a decrease in tooth resistance, which increases susceptibility to fracture. Therefore, it is important that minimally invasive treatments be performed to preserve the dental structure and increase the resistance to fracture of endodontically treated posterior teeth. To evaluate under axial loads, using the finite element method, the stress distribution in endodontically treated molars restored with both transfixed or vertical glass fiber posts (GFP) and resin composite. An endodontically treated molar 3D-model was analyzed using finite element analyses under four different conditions, class II resin composite (G1, control model), vertical glass fiber post (G2), transfixed glass fiber posts (G3) and vertical and transfixed glass fiber posts (G4). Ideal contacts were considered between restoration/resin composite and resin composite/tooth. An axial load (300 N) was applied to the occlusal surface. The resulting tensile stresses were calculated for the enamel and dentin tissue from five different viewports (occlusal, buccal, palatal, mesial and distal views). According to the stress maps, similar stress trends were observed, regardless of the glass fiber post treatment. In addition, for the G1 model (without GFP), a high-stress magnitude can be noticed in the proximal faces of enamel (7.7 to 14 MPa) and dentin (2.1 to 3.3 MPa) tissue. The use of transfixed glass fiber post is not indicated to reduce the stresses, under axial loads, in both enamel and dentin tissue in endodontically treated molar with a class II cavity.

This study evaluated the polymerization shrinkage stress of three tooth preparation designs for indirect ceramic overlay by finite element analysis: isthmus preparation (IST); without isthmus preparation (wIST); and non-retentive preparation (nRET). The models were created based in prepared dental typodonts and were digitally impressed with an intraoral scanner. The interfaces in all models were considered perfectly bonded and all materials were considered homogeneous, linear, and isotropic. The polymerization shrinkage of the cement layer (100 µm) was simulated and evaluated by maximum principal stress criteria. The stress peaks followed this sequence: restoration = IST (13.4 MPa) > wIST (9.3 MPa) > nRET (9 MPa); cement layer = IST (16.9 MPa) > wIST (12.6 MPa) > nRET (10-7.5 MPa); and teeth = IST (10.7 MPa) > wIST (10.5 MPa) > (9 MPa). For the cement layer, the non-retentive preparation (nRET) had the lowest shrinkage stress from all the groups, obtaining a more homogeneous stress distribution on the cement surface. Regarding the abutment teeth, the IST generated a higher shrinkage stress area on the dental structure, concentrating higher stress magnitude at the axiopulpar and axiogingival angles. Non-retentive preparation seems to reduce polymerization shrinkage stress.

This study evaluated the effect of the combination of three different onlay preparation designs and two restorative materials on the stress distribution, using 3D-finite element analysis. Six models of first lower molars were created according to three preparation designs: non-retentive (nRET), traditional with occlusal isthmus reduction (IST), and traditional without occlusal isthmus reduction (wIST); and according to two restorative materials: lithium-disilicate (LD) and nanoceramic resin (NR). A 600 N axial load was applied at the central fossa. All solids were considered isotropic, homogeneous, and linearly elastic. A static linear analysis was performed, and the Maximum Principal Stress (MPS) criteria were used to evaluate the results and compare the stress in MPa on the restoration, cement layer, and tooth structure (enamel and dentin). A novel statistical approach was used for quantitative analysis of the finite element analysis results. On restoration and cement layer, nRET showed a more homogeneous stress distribution, while the highest stress peaks were calculated for LD onlays (restoration: 69-110; cement layer: 10.2-13.3). On the tooth structure, the material had more influence, with better results for LD (27-38). It can be concluded that nRET design showed the best mechanical behavior compared to IST and wIST, with LD being more advantageous for tooth structure and NR for the restoration and cement layer.

Statement of Problem: Chairside computer-aided design and computer-aided manufacturing (CAD-CAM) materials that do not require any firing steps are a promising option to expedite restoration production; however, little information is available to determine the most suitable material for each clinical situation., Purpose: The purpose of this in vitro study was to evaluate the effect of simulated toothbrushing on surface gloss, roughness, and wear of chairside CAD-CAM materials., Material and Methods: Disk-shaped specimens (n=15) were prepared of the following materials: ENA-VITA Enamic; LAV-Lava Ultimate; EMP-IPS Empress CAD; CER-Cerasmart; GRA-Grandio blocs. Gloss (Gloss Unit-GU) and surface roughness (Ra-μm) were evaluated before and after simulated toothbrushing (100 000 strokes). Wear (μm) was assessed by contact profilometry. Additional analyses of microhardness by scanning electron microscopy were also performed. Data were analyzed with 2-way repeated measures ANOVA test for roughness and gloss, and 1-way ANOVA for wear (α=.05). To estimate the correlation between Ra and GU, the Pearson correlation was calculated., Results: Before brushing, CER showed the lowest Ra (P<.001), and GRA the lowest GU values. After brushing, the feldspathic ceramic-based materials (ENA and EMP) presented the highest gloss, whereas the ceramic group (EMP) showed the lowest Ra. Before and after brushing, GRA showed the lowest GU values. Higher wear values were found for the composite resin groups (CER>GRA), with the exception of LAVA, which was similar to ENA, and EMP showing improved wear resistance. A strong negative correlation (-0.925) between GU and Ra values was detected (P<.001)., Conclusions: The materials containing a glass phase (ENA and EMP) presented higher wear resistance, higher gloss, and lower roughness after brushing than the other materials tested. The correlation test showed that the higher the surface roughness, the lower the gloss., (Copyright © 2020 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Background: This study evaluated the effect of interim restorative materials (acrylic resin (AR), resin composite (RC) or polyetheretherketone (PEEK) for dental computer-aided design/computer-aided manufacturing (CAD/CAM)) on the stress distribution of a posterior three-unit fixed partial denture., Methods: The abutment teeth (first molar and first premolar) were modeled using the BioCAD protocol containing 1.5 mm of axial reduction and converging axial walls. A static structural analysis was performed in the computer-aided engineering software, and the Maximum Principal Stress criterion was used to analyze the prosthesis and the cement layers of both abutment teeth. The materials were considered isotropic, linearly elastic, homogeneous and with bonded contacts. An axial load (600 N) was applied to the occlusal surface of the second premolar., Results: Regardless of the restorative material, the region of the prosthetic connectors showed the highest tensile stress magnitude. The highest stress peak was observed with the use of RC (129 MPa) compared to PEEK and AR. For the cement layers, RC showed the lowest values in the occlusal region (7 MPa) and the highest values for the cervical margin (14 MPa) compared to PEEK (21 and 12 MPa) and AR (21 and 13 MPa)., Conclusions: Different interim restorative materials for posterior fixed partial dentures present different biomechanical behavior. The use of resin composite can attenuate the stress magnitude on the cement layer, and the use of acrylic resin can attenuate the stress magnitude on the connector region.

Statement of Problem: Manufacturers of the recently introduced nanofilled bis-acryl composite resins no longer recommend polishing to produce interim restorations; however, whether this advice is appropriate is unclear., Purpose: The purpose of this in vitro study was to evaluate the effect of the type of interim resin material, polishing procedure, and artificial staining on surface roughness, gloss, and color., Material and Methods: Disk-shaped specimens were prepared from 1 unfilled acrylic resin (Duralay) and 3 bis-acryl composite resins (Structur 3-nanofilled, Systemp C&B-microhybrid, Proviplast-microhybrid). The specimens of each material were assigned to 2 subgroups (n=15): polished and unpolished. Surface roughness (Ra-μm), gloss (UB), and color (ΔE) were analyzed at baseline and after 14 days of artificial staining. Roughness and gloss data were separately analyzed by 3-way ANOVA and color by 2-way ANOVA, followed by the post hoc Tukey test (α=.05)., Results: The baseline roughness of all materials was significantly reduced by the polishing procedure, whereas the baseline gloss was increased (P<.001). Only the unpolished Proviplast had a significant increase in Ra values after aging. Structur 3 had higher gloss than Systemp C&B and Proviplast. The acrylic resin had the lowest color change after staining., Conclusions: The polishing procedure produced smother and glossier surfaces for all the materials tested. The nanofilled bis-acryl composite resin material had higher gloss than the microhybrid bis-acryls tested, but it was not different from the acrylic resin. The 14 days of artificial staining did not promote significant changes in Ra or gloss values, except for Ra in the unpolished Proviplast subgroup, indicating excellent performance of the materials. The acrylic resin had the highest color stability., (Copyright © 2020 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the influence of different post-endodontic techniques on the fatigue survival and biomechanical behavior of crowned restored central incisors., Methods: The crowns of 69 bovine incisors were cut, and the roots were treated endodontically and assigned randomly into three groups (n=23): resin composite buildup (BUP), glass fiber post-retained resin composite buildup (GFP), and cast post-and-core (CPC). They received full crown preparation with 2 mm ferrule, and a leucite-reinforced ceramic crown was cemented adhesively. Three specimens from each group were tested monotonically. The remaining specimens were subjected to the stepwise stress fatigue test until fracture or suspension after 1.5 x 10⁶ cycles in a chewing simulator. The load and step at which each specimen failed were analyzed by Kaplan-Meier and Mantel-Cox (log-rank test) statistics, followed by multiple pairwise comparisons, at 5% significance level. The three groups tested (BUP, GFP, and CPC) were 3D modeled (Rhinoceros 4.0) and the maximum principal stress (MPa) criteria were used to calculate the results using FEA., Results: There was no statistical difference between the treatments regarding the load or the number of cycles (Mantel-Cox log-rank test for trend, X²= 0.015, df=1, P= 0.901, X²=3.171, df=1, P= 0.995). Crown cracks were the predominant failure mode, and oblique root fractures were only observed in groups GFP and CPC. In endodontically treated incisors with a 2-mm ferrule, the post-endodontic treatment had no significant effect on fatigue survival. Non-restorable fractures only occurred in teeth restored with posts., Clinical Significance: Although the clinical significance of laboratory studies has some limitations, this study suggests that composite buildups without posts may be an option for restoring endodontically treated incisors with 2 mm ferrule height., Competing Interests: The authors deny any possible conflict of interest. This work was supported by São Paulo Research Foundation under Grant No 2017/23059-1 and the company Ivoclar Vivadent., (Copyright©American Journal of Dentistry.)

Microscopy has been widely used to complement the data of studies related to dentin bonding; however, different specimen preparation methods may influence the analysis. Aiming to contribute to the reported scenario, this study evaluated the effect of two specimen-sectioning methods (cleavage and diamond disk cut) on the quality of the scanning electron microscopy (SEM) images. Four crowns of human molars were selected and had an area of approximately 6 mm 2 of dentin exposed. They were then divided into two groups according to the universal adhesive application: total and self-etching modes. Then, composite blocks were built up and the specimens were stored in deionized water to allow the postcuring. The specimens were further divided according to the sectioning method: cleavage or diamond disk cut. Four specimens were obtained from each tooth. They were desiccated, placed on aluminum stubs, sputter-coated with gold, and observed in a scanning electron microscope, with ×2000 of magnification. The quality of the SEM images were evaluated by two calibrated examiners and classified into four scores (1-4). Mann-Whitney test (p < .05) showed that the diamond disk provided significantly higher scores than cleavage, whereas no significant difference was observed when comparing the total-etching and self-etching modes of application. The diamond disk cut method is preferable to the cleavage method to ensure the quality of the SEM analysis in studies involving the resin-dentin interface., (© 2020 Wiley Periodicals, Inc.)

Background: Carious lesions and dental fractures cause weakening in the dental structure. In these situations, endodontic treatment and prosthetic rehabilitation using an intraradicular post are indicated. However, the postspace preparation of the root canal further weakens the dental remnant, especially if there is no ferrule present. This study aimed to evaluate the stress distribution in endodontically treated upper premolars treated with different rehabilitation approaches., Materials and Methods: An endodontically treated first upper premolar was modeled for finite element analysis. Three different approaches were carried out on this model: rehabilitation with fiberglass post (FCP), endocrown (ECW), or buildup. The models were exported in STEP format to the analysis software (ANSYS 17.2, ANSYS Inc., Houston, TX, USA). The solids were considered isotropic, homogeneous, and linearly elastic. A mechanical, structural static analysis was used as the criterion of maximum principal stress to show regions under tensile stress to evaluate the stress distribution in the restoration, cementation line, and root. A load of 400 N (90°) was applied to the lingual triangular ridge. The values of maximum principal stress in MPa were evaluated through colorimetric graphs., Results: Similar stress concentration was observed for all groups. However, the ECW group presented higher values in the restoration/cement interface and root dentin., Conclusions: All the treatment modalities had favorable mechanical behavior to support the masticatory loads; nevertheless, the ECW group presented a higher risk of detachment failure., Competing Interests: There are no conflicts of interest.

Circomics was coined to describe the combination of rolling circle amplification (RCA), restriction fragment length polymorphism (RFLP) and pyro-sequencing to investigate the genome structures of small circular DNAs. A batch procedure is described using 61 plant samples from Asia, South America and Central America which revealed 83 contig sequences of geminiviral DNA components and 4 contig sequences of DNA satellites. The usefulness of this approach is validated for the Brazilian begomoviruses, and the sequence fidelity is determined by comparing the results with those of conventional cloning and sequencing of Bolivian begomoviruses reported recently. Therefore, circomics has been proven to be a major step forward to economize costs and labor and to characterize reliably geminiviral genomes in their population structure of the quasispecies., (Copyright © 2012 Elsevier Inc. All rights reserved.)