Do bulk-fill resins decrease the restorative time in posterior teeth? A systematic review and meta-analysis of in vitro studies.

The aim of the present study was to compare the restorative time for filling cavities in posterior teeth using bulk-fill and conventional resin composites through a systematic review and meta-analysis. A search for clinical trials and laboratory studies was performed in PubMed/MEDLINE, Scopus, the Latin American and Caribbean Health Sciences Literature database, the Brazilian Library in Dentistry, Cochrane Library, Clinical Trials, and ReBEC (Registro Brasileiro de Ensaios Clínicos) databases without publication year or language restriction. Two reviewers identified eligible studies according to the inclusion criteria: bulk-fill compared to conventional resin in class I or II, and the restorative time as an outcome. A meta-analysis of the restorative time mean difference between composites was performed (inverse variance method, random effects model; Z-test, P ≤ .05). From the 662 eligible studies, 133 were selected for full-text analysis; three were included in the systematic review and in the meta-analysis. Overall, the restorative time was lower when bulk-fill was used (P = .0007, Z = 3.37), as the subgroup full-body bulk-fill (P < .00001, Z = 21.00). There was no difference in restorative time between flowable bulk-fill and conventional resins (P = .08, Z = 1.76). Moderate-to-substantial heterogeneity was detected. Full-body bulk-fill composites decrease the restorative time in posterior teeth compared to conventional resins. Full-body bulk-fill resins require a shorter restorative time to perform restorations in posterior teeth than conventional resins, but the same is not valid for flowable bulk-fill resin composites.

Do adhesive systems influence the color match of resin composites?

BACKGROUND: This in vitro study evaluated the influence of adhesive systems on the color match of a resin composite with different translucencies. METHODS: Sixty disk-shaped specimens were made with A2 and opaque A2 (OA2) shades of nanohybrid resin composite Z250 XT. Specimens of each shade (n = 30) were randomly reassigned to 3 subgroups according to adhesive system: a 2-step etch-and-rinse adhesive (Adper Single Bond Plus), a 2-step self-etch system (Clearfil SE Bond) and a universal adhesive (Scotchbond Universal Adhesive). The bonding agents were applied to resin composite specimens following the manufacturers' recommendations. Additionally, 5 disk samples of each adhesive system were prepared. Colorimetric evaluation (CIE L*a*b* system) was performed immediately after polishing the sample and application of the adhesive systems. Color changes (ΔE and ΔE00) were calculated between 2 measurements. Color coordinates L*, a* and b* of the adhesive disks were also assessed. The data obtained were analyzed using ANOVA and Tukey's post hoc test (α = 0.05). RESULTS: The application of Scotchbond Universal Adhesive to the resin composite A2 shade resulted in the highest color change (p<0.01; ΔE = 3.1 ± 0.7 and ΔE00 = 1.8 ± 0.4). However, no significant difference was observed among adhesive systems when applied to the resin composite OA2 shade (p>0.05). Scotchbond Universal Adhesive revealed augmented yellowing and greening in comparison with other experimental groups. CONCLUSIONS: The universal adhesive tested resulted in higher visually perceptible color changes when using a more translucent resin composite shade, but this was clinically acceptable.

Does air particle abrasion affect the flexural strength and phase transformation of Y-TZP? A systematic review and meta-analysis.

OBJECTIVES: A systematic review was conducted to assess the effects of air-particle abrasion procedures on the mechanical strength and phase transformation of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). DATA: This report followed the PRISMA Statement. From 1013 eligible studies, 78 were selected for full-text analysis, from which 37 were excluded. The 41 remaining papers were included for the systematic review; hand-searching yielded three papers. The review comprised a total of 44 studies; 21 were included in the meta-analysis. SOURCES: Searches were performed with no publication year limit through November 2015 in PubMed/MEDLINE, Web of Science (Core Collection) and Scopus databases. STUDY SELECTION: In vitro studies evaluating the effect of air-particle abrasion protocols on the mechanical strength and/or phase transformation of Y-TZP zirconia specimens, immediately or after aging. For the meta-analysis, flexural strength data of air-particle abrasion vs. control (nonabraded) were globally and subgroup analyzed. Subgroup analyses assessed blasting parameters (particle size, pressure, or time duration) and the effect of aging. Statistical analyses were conducted using RevMan 5.1 (Cochrane Collaboration, Copenhagen, Denmark). Comparisons were performed with random-effect models at a 5% significance level. Phase transformation data were included only in the systematic review, as insufficient data were available for meta-analysis. CONCLUSIONS: Airborne-particle abrasion improved flexural strength of Y-TZP, regardless of abrasion parameters and the presence or lack of aging (p≤0.05). Phase transformation tended to be increased by air abrasion immediately or with up to 2h of aging. However, after aging for 12h or more, the abraded Y-TZP showed less monoclinic content than the control.

Starch tubing: an alternative method to build up microshear bond test specimens.

PURPOSE: To evaluate an alternative device using starch tubes to build up resin composite specimens for microshear bond tests. MATERIALS AND METHODS: Twenty human molars were selected and sectioned mesiodistally to obtain two sections. The teeth were randomly divided into 4 groups (n = 10) according to the adhesive system - a two-step etch-and-rinse adhesive (Adper Single Bond) and a two-step self-etching adhesive (Clearfil SE Bond) - and the type of tube, starch or polyethylene. The tubes were evaluated under a stereomicroscope at 25X magnification to observe the variation in internal diameter. The resin composite was bonded to flat enamel surfaces using one of the adhesive systems and tube types. After 24 h storage in distilled water, the microshear bond strength (µSBS) was determined and the fracture pattern was analyzed under a stereomicroscope (400X magnification). The microshear bond strength values were subjected to two-way ANOVA. The chi-square test was used to compare pre-test failures and fracture patterns between the groups (p < 0.05). RESULTS: The type of tube, the adhesive system, and their interaction did not influence the bond strength values (p = 0.062, p = 0.122, and p = 0.301, respectively). No significant differences were observed for pre-test failures or fracture patterns (p = 0.320 and p = 0.561, respectively). CONCLUSION: Using starch tubes is an alternative to build up composite resin specimens for microshear bond strength testing with the two tested adhesive systems.

Influence of aging treatments on microtensile bond strength of adhesive systems to primary dentin.

PURPOSE: The purpose of this study was to evaluate the in vitro influence of aging treatments on the microtensile bond strength of 2-step total-etch and self-etch adhesive systems to primary dentin. METHODS: Class I cavities (4 mm x 4 mm x 2 mm) were prepared in 80 extracted human primary molars divided into 8 groups (N=5) per adhesive system: (1) Single Bond (SI); and (2) Clearfil SE Bond (SE). Restored teeth were exposed to individual and combined aging treatments: (1) thermal (2,000 x at 5-55 degrees C; T); (2) mechanical load (100,000 x 80 N; M); (3) pH (mineralizing/demineralizing solutions; pH); and (4) control (24-hour water storage; C). Beam-shaped microtensile specimens were prepared (0.8 mm2 cross-sectional area) and loaded at a crosshead speed of 1.0 mm/minute in a universal testing machine. Fracture modes were examined by scanning electron microscope. RESULTS: Means (MPa) and standard deviations (+/-) were: (1) SI-T=24.17 (+/-1.99); (2) SI-M=25.64 (+/-9.75); (3) Si-pH=23.43 (+/-4.19); (4) SI-C=33.81 (+/-2.45); (5) SI-TM=18.60 (+/-3.57); (6) SI-TpH=23.90 (+/-4.28); (7) SI-MpH=20.96 (+/-4.06); (8) SI-TMpH=20.94 (+/-3.15); (9) SE-T=24.08 (+/-4.52); (10) SE-M=18.30 (+/-14.12); (11) SE-pH=19.22 (+/-8.93); (12) SE-C=37.80 (+/-7.28); (13) SE-TM=22.89 (+/-11.74); (14) SE-TpH=27.87 (+/-12.77); (15) SE-MpH=18.87 (+/-10.95); and (16) SE-TMpH=22.55 (+/-3.05). Both adhesive systems presented similar dentin bond strength (P>.05) which were significantly reduced when combined aging treatments were applied or when pH cycling (pH) was done. CONCLUSION(S): Combined aging treatments and also pH cycling alone influenced negatively adhesive bond strengths.