Abstract
Purpose: To evaluate tooth preparation for full veneer cast restorations performed by final year dental students in Sudan. Materials and Methods: 117 stone dies from two different dental institutions were collected and evaluated. Polyvinylsilioxane impression material was used to produce two impressive replicas of which one was sectioned in faciolingual plane and the other in mesiodistal plane. Occlusal clearance was measured using a digital caliper. Amount of axial preparation was also measured. Impression silhouettes that were produced using an overhead projector were used to measure convergence angle. Working casts were examined for smoothness and evenness of the preparations, existence or absence of additional features of retention and the finishing line were evaluated for its position and continuity. All obtained data were statistically analyzed by using T-test, ANO-VA, and Pearson Chi square tests. P-values ≤ 0.05 were considered as statistically significant. Results: Average taper of the examined preparations was 39.98?, with 44.1? in the faciolingual, and 35.8? in the mesiodistal dimensions. Preparations for full coverage restorations were over prepared. 38.5% of the total number of preparations were found to have finishing lines in the sub and supra gingival positions. 19.66% were unable to maintain continuity of the finishing line all around the preparation. All preparations were generally smooth with no sharp angles, and 1.7% of the preparations had additional retentive features. Conclusion: Within the limitations of this study, it could be concluded that the convergence angle and finishing line preparations were less than adequate in a sizeable proportion of the preparations examined.
Highlights
Proper tooth preparation is fundamental for accomplishing successful fixed partial denture work
The aim of this study is to evaluate the quality of tooth preparation for full veneer casting restorations performed by dental students in their final school year in Sudan
The present study investigated 17 teeth (14.5%) that were prepared to construct crowns while the remaining 100 teeth (85.5%) were prepared as abutments for fifty five fixed partial dentures (FPD)
Summary
Proper tooth preparation is fundamental for accomplishing successful fixed partial denture work. Tooth preparation designs are governed by biological, mechanical and aesthetic principles. Strict clinical guidelines are emphasized in dental literature, but little information is available on how well these guidelines are followed [1]. Goodacre et al reviewed guidelines for scientific preparation and suggested nine scientific principles to guide the preparation [2]. It was suggested that 10 ̊ - 20 ̊ as an ideal total occlusal convergence angle. The minimal occluso-cervical dimension for 10 ̊ - 20 ̊ occlusal convergence is suggested to be 3 mm for incisors and premolars, and 4 mm for molars. Despite strict clinical guidelines set for tooth preparation, laboratory technicians are still facing challenges in this respect. Error in tooth preparation was set as a second laboratory challenge directly after inadequate impression [3]. It could be that these skills are difficult to learn or there is a lack of credit hours in teaching this
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