Comparison of compressive strength of crowns made by milling machine and designed by two different software

Abstract

Introduction: Temporary restorations are one of the essential components in the treatment of fixed prostheses and implants. Digital dentistry has a variety of methods for designing prosthetic treatments, including Exocad and 3Shape Dental System software. Considering that the software presuppositions for making crowns in these two softwares can eventually lead to different wall thicknesses of restorations and affect their compressive strength, the aim of this study was to investigate and compare the compressive strength of temporary restorations made by milling machine and designed by Exocad and 3Shape Dental System software. Methods and Materials: In this descriptive-interventional study, 45 temporary restorations were made and evaluated based on each of the softwares. For this purpose, an intact premolar was first scanned as a Pre Operative Model by 3Shape Laboratory Scan. The files made by the imes-icore 350i milling machine using PMMA blocks. To evaluate and compare the compressive strength, a force of 1 mm/min was applied to the central groove of the temporary cover by a process chisel with a diameter of 3 mm by the Universal Testing Machine on the samples. The amount of force displayed on the monitor during the first crack and ultimate failure was recorded. Results: In this study, in restorations made on the basis of Exocad software, the average amount of force required to create the first crack was 903.5±96 N and for the ultimate failure was 1490.4±139.3 N, and based on 3Shape Dental software System it was 1060.4±160.2 for the first crack and 1691.1±73.9 for the ultimate failure. There was a significant difference between the compressive strength of temporary restorations made based on Exocad and 3Shape Dental System software, so that the compressive strength of temporary restorations made based on 3Shape Dental System software was significantly higher than temporary restorations made based on Exocad software. Conclusion: The compressive strengths of temporary dental restorations made by both softwares are in a clinically acceptable range, but considering that the average compressive strength in the 3Shape Dental System group was slightly higher than the other group, it is possible to use the 3Shape Dental System software to increase the compressive strength of these restorations.