Digital Evaluation On Preclinical Training For The Tooth Preparation Of Maxillary Anterior All-ceramic Restorations

Objective: The aim of this study was to evaluate the effects of pre-clinical systematic training on the tooth preparation of maxillary anterior all-ceramic crown restorations using a computer aided design and computer aided manufacturing(CAD/CAM)system, a design software(CEREC? SW 4.4), and an assessment software(CEREC?PrepCheck 2.0).Methods:Forty junior dental students were randomly selected for participating a two-week preclinical systematic training which contained the studies of a 3D video of tooth preparation, the standard posture of tooth preparation, the application of the CAD/CAM system and the use of dental magnifier. Each student was required to prepare two teeth before and after training, respectively. After preparation, the results of training were evaluated by inspecting the impairments of adjacent teeth visually, assessing the amount of tooth reduction using CEREC? SW4.4, measuring the axial inclinations. The rates of overlap between the experimental tooth preparations and the master mold, including the morphology and shoulder, were calculated. The distribution of undercuts, the smoothness of prepared surfaces as well as the continuity of the finish lines was also recorded using CEREC? PrepCheck 2.0.Results: It was shown that there was a significant difference in palatal AI among the pre-training group, the post-training group and the master preparation(P<0.05). The average palatal AI of the post-training group was lower than that of the pre-training group. However, it was still higher than that of the master preparation(P<0.05). The pre-training labial AI, mesial AI and the distal AI were significantly greater than post-training values(P<0.05). On the other hand, the difference between the post-training group and the master preparation was not significant(P>0.05).It was also found that there was no significant difference on the amount of tooth(both labial and incisal sides) reduction between the post-training group and the standard preparation(P>0.05). The lingual reduction after training were closer to the master preparation than the pre-training group(P<0.05). Furthermore, the labial, incisal and palatal reductions were all significantly increased after training(P<0.05).With theaccomplishment of training, the impairments of adjacent teeth as well as the generation of undercuts after preparation were significantly reduced(P<0.05).Significant improvements after training in the rate of overlap between the experimental preparation and the master preparation and that between the prepared shoulder and the pre-defined shoulder were also identified(P<0.05).Moreover, the application of dental magnifier in tooth preparation could effectively improve the continuity of finish lines and decrease the sharp edges on the prepared surfaces(P<0.05).Conclusions: Pre-clinical systematic tooth preparation training could improve the quality of tooth preparation effectively.