Investigation of the effect of bur quality on computer aided manufacturing devices

The aim of this study is to evaluate the thickness of ceramic crowns produced after repeated processes without changing the bur with computer aided manufacturing (CAM) system and to evaluate the accuracy of diamond burs. 48 crowns were produced with the same bur until the system warning for a bur change. CEREC MC XL (Sirona Dental Systems GmbH, Bensheim, Germany) was used without changing the bur. The thickness of crowns was measured at three points (middle of occlusal face, mesiobuccal cusp and middle of the buccal face) with a digital micrometer (227-11-820, TRONIC, Torino, Italy). Crowns were divided into 4 groups according to their production order (n=12). The groups were compared in terms of their average thickness, and their deviations from the first measurement were compared. IBM SPSS Statistics 22 program was used for statistical analysis. The normal distribution of the parameters was evaluated with Skewness and Shapiro Wilks test and the parameters were not normal. The Kruskal Wallis test and Mann Whitney U test were used for the comparison of the parameters between groups. Significance was evaluated at p <0.05. There was no statistically significant difference between the groups in terms of occlusal and mesiobuccal average thickness (p> 0.05). There were statistically significant differences between the groups in terms of buccal thickness averages (p <0.05). There was no statistically significant difference between the groups in terms of deviation from the first measurement in the occlusal region (p> 0.05). There was a statistically significant difference between the groups in terms of deviation from the first measurement in the mesiobuccal region (p <0.05). There was a statistically significant difference in the amount of deviation from the first measurement in the buccal region between the groups (p <0.05). Increase in thickness was observed in buccal measurements with erosion due to usage of the bur, and deviation from the first value was observed in mesiobuccal and buccal measurements. According to our study, the first 24 crowns were produced properly.