Comparison of retention of provisional crowns made with machine milling following the designs by Exocad and 3-Shape Dental System Softwares

Abstract

Introduction: Success in making provisional restorations considerably depends on their sufficient amount of retention. Although today the use of CAD-CAM is a common method for making these restorations, however, different presuppositions in each designing softaware for crown design and manufacture ultimately lead to different spaces between the inner surface of the restoration and the outer surface of the carved tooth which lead to different amounts of retention in the restorations. The aim of this study was to investigate and compare the amount of retention in the provisional crowns made with machine milling following the designs by Exocad and 3-Shape Dental System Softwares. Methods and Materials: In this descriptive-interventional study, 45 provisional restorations were manufactured and evaluated based on each of the defaults of softwares. For this purpose, an intact premolar tooth were first scanned as a Pre Operative Model by 3Shape Laboratory Scan. Then the tooth was carved according to standard criteria and the final restoration was designed based on the pre-app file. The files designed by the imes-icore 350i milling machine using PMMA blocks and were cemented with Temp-band. Retention amounts were measured by pulling test via applying a force of 0.5 mm / min by the Universal Testing Machine and then measuring the force required to remove the couplings. Results: In this study, the average force required for removeing the couplings in provisional restorations designed by Exocad software was 66.8±15.1 N and in provisional restorations designed by 3Shape dental system was 69.5±11.3 N. Comparison of these means showed that there was no significant difference between the amount of force required to remove the cupings in the provisional restorations designed by Exocad software and 3Shape Dental System (P = 0.335). Conclusion: The use of both Exocad and 3Shape Dental System can provide provisional restorations with suitable amount of retention for dental treatments.