Nanohybrid and microfilled hybrid versus conventional hybrid composite restorations: 5-year clinical wear performance.

UNLABELLED: The 5-year findings of a randomized clinical trial testing the null hypothesis that there are no differences between the clinical-wear performances of nano-, microfilled-, and conventional hybrids placed in class I and class II cavities are reported. Effects of subject-, operator-, and restoration-related variables on wear were assessed. Sixteen Tetric-C, 17 Tetric-EC, and 16 Gradia-DP restorations were placed in human molars and recalled at baseline, 6 months and at yearly intervals. The gypsum replicas at each recall were scanned (3D laser scanning), epoxy resin replicas were observed under scanning electron microscope and linear mixed models were used to study the influence of different variables on wear. The generalized vertical wear rate/month were (1.4 µm Tetric-C and Tetric-EC; 1.8 µm Gradia-DP) and volume wear rate/month were (0.017 mm(3) Tetric-EC; 0.018 mm(3) Gradia-DP, and 0.011 mm(3) Tetric-EC). Operator-cavity type interaction and surface area of restorations did significantly influence the volume wear rates (p < 0.05). The three wear patterns: fatigue cracks at heavy occlusal contact area/OCA, pitting at light OCA, and scratches/striations along the food escape pathways were evident. The three hybrids differed significantly in volume wear due to material and operator variables. CLINICAL RELEVANCE: Clinically, operators and cavity type can affect restorations' wear magnitude but do not contribute to increased functional risk of fracture or harmful effect on pulp and periodontal biocompatibility.

Three-year randomised clinical trial to evaluate the clinical performance, quantitative and qualitative wear patterns of hybrid composite restorations.

The aim of the study was to compare the clinical performance, quantitative and qualitative wear patterns of conventional hybrid (Tetric Ceram), micro-filled hybrid (Gradia Direct Posterior) and nano-hybrid (Tetric EvoCeram, TEC) posterior composite restorations in a 3-year randomised clinical trial. Sixteen Tetric Ceram, 17 TEC and 16 Gradia Direct Posterior restorations were placed in human molars and evaluated at baseline, 6, 12, 24 and 36 months of clinical service according to US Public Health Service criteria. The gypsum replicas at each recall were used for 3D laser scanning to quantify wear, and the epoxy resin replicas were observed under scanning electron microscope to study the qualitative wear patterns. After 3 years of clinical service, the three hybrid restorative materials performed clinically well in posterior cavities. Within the observation period, the nano-hybrid and micro-hybrid restorations evolved better in polishability with improved surface gloss retention than the conventional hybrid counterpart. The three hybrid composites showed enamel-like vertical wear and cavity-size dependant volume loss magnitude. Qualitatively, while the micro-filled and nano-hybrid composite restorations exhibited signs of fatigue similar to the conventional hybrid composite restorations at heavy occlusal contact area, their light occlusal contact areas showed less surface pitting after 3 years of clinical service.

Multiple testing of food contact materials: a predictive algorithm for assessing the global migration from silicone moulds.

For reasons of food safety, packaging and food contact materials must be submitted to migration tests. Testing of silicone moulds is often very laborious, since three replicate tests are required to decide about their compliancy. This paper presents a general modelling framework to predict the sample's compliance or non-compliance using results of the first two migration tests. It compares the outcomes of models with multiple continuous predictors with a class of models involving latent and dummy variables. The model's prediction ability was tested using cross and external validations, i.e. model revalidation each time a new measurement set became available. At the overall migration limit of 10 mg dm(-2), the relative uncertainty on a prediction was estimated to be ~10%. Taking the default values for α and ß equal to 0.05, the maximum value that can be predicted for sample compliance was therefore 7 mg dm(-2). Beyond this limit the risk for false compliant results increases significantly, and a third migration test should be performed. The result of this latter test defines the sample's compliance or non-compliance. Propositions for compliancy control inspired by the current dioxin control strategy are discussed.