The aims of this retrospective clinical study were to compare the longevities of direct posterior amalgam restorations (AMs) and resin composite restorations (RCs) that were subjected to occlusal stresses and to investigate variables predictive of their outcome. A total of 269 AMs and RCs filled in Class I and II cavities of posterior teeth were evaluated with Kaplan-Meier survival estimator and multivariate Cox proportional hazard model. Seventy-one retreated restorations were reviewed from dental records. The other 198 restorations still in use were evaluated according to modified US Public Health Service (USPHS) criteria by two investigators. The longevity of RCs was significantly lower than that of AMs (AM = 8.7 years and RC = 5.0 years, p<0.05), especially in molars. The prognostic variables, such as age, restorative material, tooth type, operator group, diagnosis, cavity classification, and gender, affected the longevity of the restorations (multivariate Cox regression analysis, p<0.05). However, among the restorations working in oral cavities, their clinical performance evaluated with modified USPHS criteria showed no statistical difference between both restoratives. In contrast to the short longevity of RCs relative to AMs, the clinical performance of RCs working in oral cavities was observed to be not different from that of AMs. This suggests that once a RC starts to fail, it happens in a rapid progression. As posterior esthetic restorations, RCs must be observed carefully with periodic follow-ups for early detection and timely repair of failures.
Objectives: This clinical study evaluated the effect of light activation on the whitening efficacy and safety of in-office bleaching system containing 15% hydrogen peroxide gel. Materials and Methods: Thirty-three volunteers were randomly treated with (n = 17, experimental group) or without light activation (n = 16, control group), using Zoom2 white gel (15% H2O2, Discus Dental) for a total treatment time of 45 min. Visual and instrumental color measurements were obtained using Vitapan Classical shade guide and Shadepilot (DeguDent) at screening test, after bleaching, and 1 month and 3 month after bleaching. Data were analyzed using t-test, repeated measure ANOVA, and chi-squared test. Results: Zoom2 white gel produced significant shade changes in both experimental and control group when pre-treatment shade was compared with that after bleaching. However, shade difference between two groups was not statistically significant (p > 0.05). Tooth shade relapse was not detected at 3 months after bleaching. The incidence of transient tooth sensitivity was 39.4%, with being no differences between two groups. Conclusions: The application of light activation with Zoom2 white gel system neither achieved additional whitening effects nor showed more detrimental influences. [J Kor Acad Cons Dent 2011;36(4)
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