Comparative evaluation of different tooth taper and its influence on retention of metal crowns luted with resin cements - An in vitro study

Background: Taper of the prepared tooth is one of the most important factor for retention while luting cements are weak but a critical link for retention Aims: Compare the influence of different tapers of prepared teeth on retention of metal crowns when luted with two commercially available adhesive resin cements Materials and Method: 48 extracted human premolars were used in this study. Each tooth was mounted in a PVC ring with auto polymerizing acrylic resin. A customized device was used to standardize the tooth preparation. Teeth were divided into 3 equal groups representing taper 6º, 12º, and 30 º. Metal crowns were fabricated for each tooth. Prepared teeth were luted with either RelyX Ultimate Clicker or Multilink Automix. Specimens were subjected to ‘Crown Pull Off’ test using Universal Testing Machine Statistical analysis used: One way ANOVA with Tukey post-hoc and Independent ‘t’ test Results: Statistically significant difference was found in the mean failure stress at 6º degree taper angle compared to 30º with p value ≥ 0.003 for both the adhesive resin cements. There was no significant difference of mean of failure stress for metal crowns luted with RelyX Ultimate Clicker and Multilink Automix Conclusions: Mean failure stress was highest at taper at 6º with a steady decrease at 12º and significant decrease at 30º taper It is utmost important for clinician to prepare the tooth within the range of 12º taper. While adhesive resin cements RelyX Ultimate and Multilink Automix are equally effective in terms of retention of the crowns.