Pull-out bond strength of fiber post luted with two types of resin luting cements using different light curing units.

AIMS: The aim of this study was to evaluate the pull-out bond strength of fiber post when cemented with a self-adhesive dual-cured resin luting cement and a conventional light-cured resin luting cement. In addition, the influence of a light-emitting diode (LED) and halogen (QTH) curing lights on the pull-out bond strength was assessed. MATERIALS AND METHODS: A total of 40 extracted human teeth were selected. Post-space preparation of 10 mm was done and two types of resin cement i.e. RelyX Unicem (RXU) and variolink esthetic LC (VLE) were used for cementation of a translucent RelyX fiber post. Light activation for 60 s was done with LED and QTH curing units. The pull-out test was performed parallel to the long axis of the tooth and the post at a crosshead speed of 1 mm/min using a universal testing machine. The load required to dislodge each post was recorded in Newton (N). Statistical analysis was done and a value of P < 0.05 was considered statistically significant. RESULTS: The RXU showed a mean (SD) pull-out bond strength of 203.5N (47.1) and 207.3N (31.3) when light activated with LED and QTH curing lights, respectively. For VLE, the mean pull-out bond strength was 78.9N (21.5) and 87.7N (30.7), when light activated with LED and QTH curing lights, respectively. Moreover, LED and QTH curing lights did not influence the pull-out bond strength for both the test materials. CONCLUSION: It is concluded that a dual-cured resin luting cement should be used for the cementation of fiber post. Further research is required to understand the light transmission of translucent fiber posts.

Systematic review with meta-analysis: placebo rates in induction and maintenance trials of Crohn's disease.

BACKGROUND: Minimising placebo response is essential for drug development. AIM: To conduct a meta-analysis to determine placebo response and remission rates in trials and identify the factors affecting these rates. METHODS: MEDLINE, EMBASE and CENTRAL were searched from inception to April 2014 for placebo-controlled trials of pharmacological interventions for Crohn's disease. Placebo response and remission rates for induction and maintenance trials were pooled by random-effects and mixed-effects meta-regression models to evaluate effects of study-level characteristics on these rates. RESULTS: In 100 studies containing 67 induction and 40 maintenance phases and 7638 participants, pooled placebo remission and response rates for induction trials were 18% [95% confidence interval (CI) 16-21%] and 28% (95% CI 24-32%), respectively. Corresponding values for maintenance trials were 32% (95% CI 25-39%) and 26% (95% CI 19-35%), respectively. For remission, trials enrolling patients with more severe disease activity, longer disease duration and more study centres were associated with lower placebo rates, whereas more study visits and longer study duration was associated with higher placebo rates. For response, findings were opposite such that trials enrolling patients with less severe disease activity and longer study duration were associated with lower placebo rates. Placebo rates varied by drug class and route of administration, with the highest placebo response rates observed for biologics. CONCLUSIONS: Placebo rates vary according to whether trials are designed for induction or maintenance and the factors influencing them differ for the endpoints of remission and response. These findings have important implications for clinical trial design in Crohn's disease.