Albert O Adegbembo1, Philip A Watson, Shanin Rokni. 1. Department of Biomaterials, Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada. albert.adegbembo@utoronto.ca
Abstract
AIM: Data on the weights of amalgam restorations are lacking. The aim of this study was to determine these weights and to develop criteria to facilitate their estimation. METHODS: Four separate regression models with 4 covariates in various combinations were used to estimate the weight of amalgam restorations. Model I, based on 514 restorations from both natural and anatomical replica teeth, contained 3 covariates: the number of restored surfaces (covariate A), the type of tooth (covariate B) and whether the restoration had been removed from a natural tooth or an anatomical replica tooth (covariate C). Model II, based on 359 restorations from anatomical replicas, contained 2 covariates: A and B. Model III, based on 155 restorations from natural teeth, contained 3 covariates: covariates A and B and whether the natural teeth had been extracted in 2002 or at least 15 years previously (covariate D). In model IV, covariate D was removed from model III. RESULTS: Model I explained 72% of the variation in the weight of restorations; the partial R2 for covariates A, B and C in model I was 0.5818, 0.797 and 0.0579, respectively (p < 0.001). In model III, the weights of the restorations did not depend on covariate D (p = 0.93). The least square mean weight of amalgam restorations with 1, 2, 3, and 4 or more surfaces restored (and 95% confidence interval) was 0.31 g (0.28-0.34 g), 0.49 g (0.45-0.53 g), 0.81 g (0.76-0.86 g) and 1.38 g (1.31-1.45 g), respectively. CONCLUSION: The number of surfaces restored (covariate A) accounted for at least 80% of the variation in the weight of restorations in all models and therefore provides the best estimate for the weight of amalgam restorations.
AIM: Data on the weights of amalgam restorations are lacking. The aim of this study was to determine these weights and to develop criteria to facilitate their estimation. METHODS: Four separate regression models with 4 covariates in various combinations were used to estimate the weight of amalgam restorations. Model I, based on 514 restorations from both natural and anatomical replica teeth, contained 3 covariates: the number of restored surfaces (covariate A), the type of tooth (covariate B) and whether the restoration had been removed from a natural tooth or an anatomical replica tooth (covariate C). Model II, based on 359 restorations from anatomical replicas, contained 2 covariates: A and B. Model III, based on 155 restorations from natural teeth, contained 3 covariates: covariates A and B and whether the natural teeth had been extracted in 2002 or at least 15 years previously (covariate D). In model IV, covariate D was removed from model III. RESULTS: Model I explained 72% of the variation in the weight of restorations; the partial R2 for covariates A, B and C in model I was 0.5818, 0.797 and 0.0579, respectively (p < 0.001). In model III, the weights of the restorations did not depend on covariate D (p = 0.93). The least square mean weight of amalgam restorations with 1, 2, 3, and 4 or more surfaces restored (and 95% confidence interval) was 0.31 g (0.28-0.34 g), 0.49 g (0.45-0.53 g), 0.81 g (0.76-0.86 g) and 1.38 g (1.31-1.45 g), respectively. CONCLUSION: The number of surfaces restored (covariate A) accounted for at least 80% of the variation in the weight of restorations in all models and therefore provides the best estimate for the weight of amalgam restorations.