Available online ---KEYWORDS bleaching; carbamide peroxide; hydrogen peroxide; restorative material Abstract In recent years, there has been an increased demand for improvement in the appearance of natural teeth. The conservative technique of tooth bleaching has gained attention and acceptance from both patients and clinicians. Despite increased popularity, there is controversy surrounding the adverse effects of bleaching on dental restorative materials. This article reviews the effects of bleaching agents on major categories of dental restorative materials and provides evidence-based recommendations to the clinicians and researchers. Current literature reveal that bleaching might have a detrimental effect on restorative materials. However, because of the variability in experimental design, there is a lack of consensus concerning the bleaching effects on restorative materials. A standardized and reproducible guideline for assessment of bleaching effects on restorative materials needs to be established and verified by future studies.

No abstract

Background. Monolithic restorations made of translucent yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) have become popular over the past few decades. However, whether aging affects the color and translucency of monolithic translucent Y-TZP is unclear. Objective. The aim of this systematic review and meta-analysis of in vitro studies was to evaluate the effects of aging on the color and translucency of monolithic translucent Y-TZP ceramics. Materials and Methods. This systematic review/meta-analysis was reported according to the PRISMA statement and registered in the OSF registries (https://osf.io/5qjmu). Four databases including Medline via the PubMed, Embase, and Web of Science databases and the Cochrane Library were searched using no publication year and language limits. The last search was executed on November 20, 2020. In vitro studies comparing the translucency and/or color of monolithic translucent Y-TZP ceramics before and after simulated aging were selected. Meta-analyses were performed using Review Manager software (version 5.3, Cochrane Collaboration, Oxford, UK) with random-effects models at a significance level of 0.05. A risk-of-bias assessment was also performed for the included studies. Results. Of the 188 potentially relevant studies, 13 were included in the systematic review. The hydrothermal aging duration ranged from 1 to 100 h at relatively similar temperatures (~134°C). In the general meta-analyses, the aged Y-TZP ceramics exhibited similar translucency parameter (TP), L ∗ , and b ∗ values compared with the nonaged controls ( P = .73 , P = .49 , and P = .62 , respectively). Moreover, there was a significant difference between the aged and nonaged Y-TZP ceramics in the a ∗ value ( P = .03 ; MD = − 0.26 ; 95% CI = − 0.51   to − 0.02 ), favoring the nonaged Y-TZP ceramics. The subgroup analyses showed that the duration of aging contributed to changes in the translucency and color of the Y-TZP ceramics. Conclusions. The optical properties of monolithic translucent Y-TZP ceramics were stable after hydrothermal aging at 134°C and 0.2 MPa for ≤20 h. Moreover, clinically unacceptable changes in the translucency and color of monolithic translucent Y-TZP ceramics were found after hydrothermal aging for >20 h.

The aim of the present study was to evaluate the in vitro cytotoxicity of self-adhesive dual-cured resin cement (SADRC) polymerized beneath three different cusp inclinations of zirconia with different light curing time. A commercial SADRC (Multilink Speed) was polymerized beneath zirconia (ZrO2) with three different cusp inclinations (0°, 20°, and 30°) for 20 s or 40 s. After being stored in light-proof box for 24 h, the ZrO2-SADRC specimens were immersed in DMEM for 72 h and then we got the extract solution, cultured the human gingival fibroblasts (HGF, 8 × 103 per well) with 100% or 50% concentrations of the extract solution for 24 h, 72 h, and 120 h, respectively, and evaluated cytotoxicity of the polymerized SADRC with CCK-8 assay in optical density (OD) values, relative growth rates (RGR), and cytotoxicity grades. Statistical analysis was conducted using a two-way ANOVA followed by post hoc Student–Newman–Keuls test. The OD values varied from 0.8930 to 3.2920, the RGR varied from 33.93% to 98.68%, and the cytotoxicity grades varied from 0 to 2. There was significant difference in the OD values among the different cusp inclinations of zirconia (P < 0.001), and there was significant difference in the OD values between the different light curing times in some situations (P < 0.05). The cusp inclination of zirconia affects the in vitro cytotoxicity of SADRC. Prolonging the light curing time from 20 s to 40 s can reduce the in vitro cytotoxicity of SADRC when the cusp inclination of zirconia is smaller than 20°.

No abstract