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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.

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).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.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).Both resin composites and adhesives tested can be combined for partial restorations to treat CDs.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.

Made available in DSpace on 2022-05-01T09:31:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-03-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) 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. Department of Dental Materials and Prosthodontics Institute of Science and Technology São Paulo State University (Unesp), 777th Eng. Francisco José Longo Av., SP Post-Graduate Program in Dentistry University of Taubaté (UNITAU), 09th Rua Dos Operários St., SP Graduate Program of Oral Science Prosthodontics Unit School of Dentistry Federal University of Santa Maria (UFSM) Roraima Av, RS School of Dentistry São Francisco University (USF), 218th São Francisco de Assis Av., SP Department of Restorative Dentistry Institute of Science and Technology São Paulo State University (Unesp), 777th Eng. Francisco José Longo Av., SP Department of Dental Materials and Prosthodontics Institute of Science and Technology São Paulo State University (Unesp), 777th Eng. Francisco José Longo Av., SP Department of Restorative Dentistry Institute of Science and Technology São Paulo State University (Unesp), 777th Eng. Francisco José Longo Av., SP

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 × 106 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 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.

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

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 × 106 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.

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.

Changes in the organic matrix of composite resins have been proposed to improve their surface properties. However, polishing systems may perform differently in different materials. This study compared the effect of polishing systems on the surface roughness of four composite resins containing different resin monomers: Admira Fusion (nanohybrid containing pure ormocer), Aura Bulkfill (nanohybrid containing Bis-GMA, UDMA), Charisma Diamond (nanohybrid containing TCD-DI-HEA) and Vittra APS (nanofilled containing UDMA). Cylinders (N = 120, n = 10) were prepared from each material and the top surface of each specimen was grounded using a diamond finishing bur. Baseline measurements of surface roughness (Ra) were recorded using a contact profilometer and the specimens of each composite were divided into three subgroups according to the polishing system: one-step, two-step, three-step. Ra measurements were recorded also after polishing. Data were analyzed using three-way ANOVA and Tukey’s test (p < 0.05). The baseline roughness of all composites was significantly reduced after polishing (p < 0.001). The two-step polishing system provided the smoothest surface for Admira Fusion (0.0770 ± 0.0171) and Charisma (0.1091 ± 0.0090), whereas for Aura and Vittra no significantly differences were found for the three polishing systems tested. The surface smoothness seems to be more material dependent than step dependent, but all tested systems provided clinically acceptable results.

Made available in DSpace on 2022-05-01T08:44:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-02-01 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. Department of Restorative Dentistry Endodontics Division Institute of Science and Technology São Paulo State University (UNESP), Av. Francisco José Longo 777, São Dimas, SP Department of Dental Materials and Prosthodontics Institute of Science and Technology São Paulo State University (UNESP) Department of Restorative Dentistry Operative Dentistry Division Institute of Science and Technology São Paulo State University (UNESP) Department of Restorative Dentistry Endodontics Division Institute of Science and Technology São Paulo State University (UNESP), Av. Francisco José Longo 777, São Dimas, SP Department of Dental Materials and Prosthodontics Institute of Science and Technology São Paulo State University (UNESP) Department of Restorative Dentistry Operative Dentistry Division Institute of Science and Technology São Paulo State University (UNESP)

Made available in DSpace on 2022-04-28T19:47:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-03-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The aim of this study was to assess the resin microshear bond strength (μSBS) and the surface topography of lithium disilicate ceramic milled by CAD/CAM and to compare it with in-lab methods that simulate the topography of milled surfaces; thus, assessing the feasibility of those in-lab methods for in vitro microshear studies. The study was composed of 2 control groups (CAD/CAM group – discs were milled by a CAD/CAM system; POL – polished ceramics surface) and 4 testing groups (SiC – manual grinding simulation with #60 silicon carbide paper; WS – manual grinding with #60 wood-sandpaper; DB – grinding with a fine cylindrical diamond bur; MANDREL – grinding with a CAD/CAM bur coupled to a mandrel). After production, the ceramic samples were crystallized. Surface treatment with hydrofluoric acid (HF) and silane was performed on the bonding surface, then the starch matrices were filled by the resin cement and light-activated. The specimens (n= 45) were submitted to μSBS after 24 h of storage in water (37° C) and the failure pattern was analyzed. Topographic analysis, surface roughness, contact angle, and fractal dimension were performed. One-way ANOVA and Tukey's post-hoc tests were run for roughness, while Bonferroni’ post hoc was used for μSBS data. Fractal dimension data was qualitatively assessed. No difference was found in the μSBS between in-lab simulation methods and the milled group, while the polished group presented the lowest μSBS values. The CAD/CAM milled specimens presented the highest roughness values, while the POL the lowest ones. In regards to surface complexity, no difference was found among all simulated groups and the CAD/CAM group, with an exception for the POL group. All conditions presented an increase in surface complexity after HF etching. Therefore, the resin bond strength to lithium disilicate glass-ceramic is not influenced by the in-lab simulation method, meaning they are predictable approaches when evaluating the resin bonding to the tested ceramic; the surface polishing underestimates the bond results in ∼40%. MSciD and PhD Graduate Programs in Oral Science – Prosthodontic Units Faculty of Odontology Federal University of Santa Maria Department of Dental Materials and Prosthodontics São Paulo State University (UNESP) – Institute of Science and Technology MSciD and PhD Graduate Programs in Physics Department of Physics Federal University of Santa Maria (UFSM) Department of Dental Materials and Prosthodontics São Paulo State University (UNESP) – Institute of Science and Technology