Wear evaluation of dental Y-TZP opposing human enamel

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Conclusions: Within the limitations of this study, Bluephase Meter II met the manufacturer’s claim and accurately measured the power output of tested LCUs. http://dx.doi.org/10.1016/j.dental.2016.08.008 8 The influence of FRCs positioning underneath CAD/CAM composite resins C.M. Saratti 1,∗ , M. Cattani-Lorente 1 , R. Sadlaceck 2 , G.T. Rocca 1 , I. Krejci 1 1 2

University of Geneva, Switzerland University of Prague, Czech Republic

Purpose/Aim: Investigate the reinforcing and stressbreaking effects of long bidirectional E-glass fiber reinforced composites (FRCs) applied underneath CAD/CAM resin composites. Materials and methods: A total of 120 specimens (9 mm × 5 mm, 4.2 mm-thick) were prepared. Specimens were divided in four Groups (n = 30): monolithic CAD/CAM resin composite (Cerasmart, GC) (Group A, control), composite resin base (Genial Posterior, GC) in a layer of 1 mm (Group B), 2 mm

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(C) and 3 mm (D) underneath two bonded layers of bidirectional e-glass FRC (Dentapreg, ADM A.S.). Over these FRCs sheets, CAD/CAM composite resin slices of 3 mm (Group B), 2 mm (C), 1 mm (D) were bonded. In each group, half of the specimens (n = 15) (Subgroups As, Bs, Cs, Ds) were loaded to fracture in a universal testing machine. Maximum fracture loads were recorded in Newtons and data were analyzed using Weibull analysis. The other half of specimens of each group (n = 15) (Subgroups Ad, Bd, Cd, Dd) were submitted to cyclic isometric stepwise loading (5 Hz) until completion of 105,000 cycles or failure after 5000 cycles at 500 N, followed by stages of 20,000 cycles at 750 N, 1000 N, 1250 N, 1500 N and 1750 N. Results were statistically analyzed by Kaplan–Meier life survival analysis and log rank test (p = 0.05). All fractured specimens were analyzed using stereomicroscope and SEM and modes of failure were determined (vertical fracture-split, partially deviated fracture or completely deviated fracture). Results: The mean static loads (N) registered were: A – 2904.13 (159.33); B – 2716.55 (307.14); C – 2539.96 (153.17); D – 2263.17 (167.96). Statistically significant differences were found between all groups (p < 0.05). The differences in survival after fatigue between groups was statistically significant, except between Groups A and C (p = 0.86213). The mode of fracture was always catastrophic (split) in Group A (without fibers) while in Groups B and C the crack was mainly partially deviated, and in Group D it was mostly totally deviated, with few differences between fractures occurred under static or dynamic loads. In all deviated fractures, the fractographic analysis confirmed the stress-breaking effect of the FRCs layer. Conclusions: The load bearing capacity of the specimens and their fatigue resistance seemed to be more related to the thickness of the CAD/CAM resin composite under the loading sphere more than to the subjacent FRCs layer. However, the fiber reinforcement protected the resin composite substructure leading to more favorable fracture patterns. http://dx.doi.org/10.1016/j.dental.2016.08.009 9 Wear evaluation of dental Y-TZP opposing human enamel S. Passos 1,∗ , Y. Torrealba 1 , B. Linke 1 , C. Flores-Mir 1 , J.A. Nychka 2 1

University of Alberta, School of Dentistry, Edmonton, Canada 2 University of Alberta, Department of Chemical and Materials Engineering, Edmonton, Canada Purpose/Aim: The aim of this systematic review was to assess enamel wear on teeth opposing zirconia restorations by analyzing in vitro studies that quantify the wear of enamel opposing zirconia ceramics. Additionally to evaluate factors related to the wear of the natural tooth opposing zirconia ceramics. Materials and methods: Five electronic databases were searched without limitations. Terms “antagonist*”, “enamel”, “wear” and “zirconi*” were used. All titles revealed by the electronic search were screened according to the following inclusion criteria: (1) In vitro studies; (2) Use of Y-TZP ceramic;

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(3) Evaluation of the antagonist’s enamel. In addition to the inclusion criteria the following exclusion criteria were applied: (1) Veneered zirconia specimens; (2) Absence of enamel wear evaluation. Study selection: Titles and abstracts were initially screened, and those that fulfilled the inclusion criteria were selected for a full-text assessment. Studies which evaluated only the material wear were not included. The studies were analyzed with regard to the wear mimicking device and wear method, its testing parameters, ceramic preparation, finishing technique, antagonist’s enamel wear and zirconia wear. When information was unavailable or limited, authors were contacted in order to obtain missing information. Results: The database search strategy retrieved 142 potentially eligible studies. After removing the duplicate studies, 62 studies were obtained. Titles and abstracts that fulfilled the inclusion criteria were selected for a full-text assessment (25). Seven laboratory studies met the inclusion criteria. Additionally, reference lists from the finally selected studies were also screened. Conclusions: There was a large variation in relation to: wear test method quantification, applied force, lateral movement, number and frequency of cycles, number of specimens, and enamel specimen preparation. In all studies, enamel wear rates were lower against polished zirconia. Differences in the test methods did not allow for comparisons of the wear rates among the studies. Polishing the surface is recommended for a full contour zirconia restoration because polished zirconia presents favorable wear behavior opposing natural teeth. http://dx.doi.org/10.1016/j.dental.2016.08.010 10 Anti-caries potential of high-fluoride dentifrices combined or not with tricalcium-phosphate M.M.A.C. Velo ∗ , A. Shiota, A.L.H. Farha, A.C. Magalhães, D. Rios, H.M. Honório, L. Wang Bauru School of Dentistry, University of São Paulo, Brazil Purpose/Aim: Fluoridated dentifrices have been advocated as an interesting strategy to prevent the development caries, but evidence regarding high-fluoride (F) dentifrices to prevent dentin root caries is still unclear. This in vitro study evaluated the effect of dentin demineralization inhibition of high-F dentifrices (5000 ␮g F/g; Colgate Prevident® – CP and 5000 ␮g F/g + tricalcium-phosphate; Clinpro® – CL, 3M ESPE) compared with a conventional dentifrice (1450 ␮g F/g; control group Colgate Total 12® – CT). Materials and methods: This study involved root dentin (4 × 4 × 2 mm) as experimental units, which were prepared from bovine incisors. These specimens were selected by surface hardness (SH) presenting 35.28 ± 0.59 KHN. The specimens were randomly distributed (n = 15) and subjected to one of the following treatments: CT, CP and CL, during 5 min, twice a day. Daily challenges consisted in cycles of 8 h in the demineralizing and 16 h in the remineralizing solution, during 7 days at 37 ◦ C. The treatments were conducted with dentifrices/water slurries (1:3, w/w), simulating the dilution that

occurs in the oral cavity when tooth-brushing. The response variable was based on the percentage of surface hardness loss (%SHL) and cross-sectional hardness (CSH). Data of %SHL and S were subjected to one-way ANOVA followed by Tukey’s test and Kruskal–Wallis, respectively (p ≤ 0.05). Results: The data of %SHL/S were, respectively: CT = 66.79 ± 3.51A/752.11 ± 297.14*; CP = 31.43 ± 4.43B/57.65 ± 22.92**; CL = 32.01 ± 10.32B/162.91 ± 81.10**. For both analyses, high-F dentifrices combined or not with tricalcium-phosphate were able to promote reduced demineralization of dentin compared to conventional fluoridated dentifrices. Conclusions: High-F dentifrices are effective to protect dentin from demineralization. http://dx.doi.org/10.1016/j.dental.2016.08.011 11 Influence of Er:Yag laser cavity preparation on micromorphology and adhesion L.T. Trevelin ∗ , B.T.F. Silva, C.S. Azevedo, P.F. Cesar, P.M. Freitas, A.B. Matos University of São Paulo, Brazil Purpose/Aim: Er:YAG laser with varied pulse duration allows for cavity preparation by means of cold ablation. Analyzing the micromorphological features of irradiated dentin tissue is key to predict the bond strength to composites. This study evaluated the influence of different pulse durations on the adhesive interface morphology and microtensile bond strength (␮TBS) of a resin composite, when cavity preparation was performed by Er:YAG laser. Materials and methods: Forty two human freshly extracted molars were cut to expose middle dentin and then polished with #600 grit silicon carbide for 60 s to create a standardized smear layer. Afterwards, specimens were randomly assigned into 3 groups according to the cavity preparation method (n = 11): G1 (control – high speed conventional preparation); G2 (200 mJ/20 Hz/50 ␮s) and G3 (200 mJ/20 Hz/300 ␮s). The laser wavelength (2.94 ␮m) was set with cooling spray at 4A/6W. Thereafter, self-etch universal adhesive (3 M/ESPE) was applied to a flat occlusal dentin surface according to manufacturer’s instructions and a resin composite (Filtek Z350 3M/ESPE) block (5 mm-high) was built in order to produce the specimens. After 24 h storage in distilled water at 37 ◦ C, the composite/dentin sticks were prepared (1 mm2 ) and ␮TBS test was performed. In addition, nine dentin discs per group were prepared to perform the analysis of the behavior of collagen fibrils by second harmonic generation (SGH) (at 380 nm excitation) and hybrid layer formation/resin tags extension using confocal laser (at 800 nm excitation). In both analyses, fluorochrome Rhodamine B was added to the adhesive. Results: Statistical analysis was performed by ANOVA and post-hoc Tukey test (˛ = 0.05). G1 displayed statistically higher microtensile bond strength values when compared to the values obtained for the other groups (p = 0.00). Group results for ␮SBS were: G1 (51.14 ± 7.16a ); G2 (29.17 ± 7.09b ); G3 (23.53 ± 4.5b ). When irradiated groups were compared, no statistical differences were observed, indicating lower ␮TBS values regardless of the pulse duration used. All groups