An In vitro study to evaluate the depth of reduction achieved by three different techniques for porcelain fused to metal crown preparation

Introduction: A near-ideal preparation lays the foundation and is required for adequate retention and resistance for fixed partial dentures. It is advisable to achieve a near-ideal preparation for the longevity of the prosthesis. Materials and Methods: Thirty maxillary left central incisors were mounted on the acrylic block. The samples were divided into groups with ten specimens: Group A-Free hand, Group B-Index, and Group C-Depth gauge. Group A was prepared using the freehand method, Group B was prepared using the putty index, and Group C was prepared using depth gauge bur. An index was prepared before and placed back on the tooth after preparation, and the gap was filled with low-viscosity elastomer. The thickness of the impression was measured at five different points under the microscope. The statistical analysis was done using one-way analysis of variance and Student's t-tests. Results: The preparations (dimensions) achieved by the freehand method were 2.02 mm, 1.70 mm, 1.11 mm, 0.90 mm, and 0.60 mm respectively at five predetermined points. Similarly, for putty index these were 1.76 mm, 1.21 mm, 0.95 mm, 1.32 mm, 0.71 mm respectively at five predetermined points. Likewise, with depth gauge bur it were 1.88 mm, 1.35 mm, 0.77 mm, 1.09 mm, 0.73 mm, respectively, at five predetermined points. There was a significant difference between the Groups (P < 0.001). Intergroup comparisons between Group A, Group B and Group C showed a significant difference. Group A showed near-ideal preparation in the palatal cervical region compared to Group B and Group C. Conclusion: The freehand technique was the least effective of the three techniques. The use of depth gauge bur had yielded the preparation near the ideal and should be considered during tooth preparation.