Restoration of crowned abutment for an existing partial denture with CAD/CAM technique

Context: When a crowned tooth which served as an abutment for a cast removable partial denture fails, refabrication of both the crown and the removable partial denture is necessitated which is an expensive treatment option. It is desirable to fabricate a new crown according to the existing cast partial denture. CAD/CAM technology is applied in this context.Objective: To compare the accuracy of fit of all ceramic crown and replicated crown fabricated using CAD/CAM technique with an existing cast partial dentureMaterials and methods: Typodont first premolar tooth was prepared to receive all ceramic crown and removable cast partial denture framework was fabricated which had an occlusal rest placed on the ceramic crown. A situation where all ceramic crown fractured with abutment tooth intact was simulated by removing the crown from the abutment. The abutment tooth with removable cast partial framework was scanned with optical scanner. Then CAD/CAM technique was used to replicate all ceramic crown which contained rest seat to receive rest for removable cast partial denture framework. The accuracy of the replicated CAD/CAM crown was measured with stereomicroscope. Statistical analysis was done using student ‘t’ test.Results: Mean measurements at the interface between crown and occlusal rest for all ceramic crown was 51.91 ± 34.48 μm and for CAD/CAM crown was 58.30 ± 24.04 μm, the interface between crown and guide plate for all ceramic crown was 18.923 ± 5.51μm and for CAD/CAM crown was 23.193 ± 5.44 μm, the interface between crown and clasp for all ceramic crown was 14.95 ± 3.13 μm and for CAD/CAM crown was 12.05 ± 2.13 μm. The gap between rest and rest seat was 221.33 μm for all ceramic crown and 232.33 μm for CAD/CAM crown. Statistical analysis was done using student ‘t’ test showed that the measurements at the interfaces for all ceramic crown and for CAD/CAM crown were statistically insignificant.Conclusions: CAD/CAM technology can be used to refabricate a ceramic crown which served as an abutment for a cast removable partial denture with measurable accuracy in the case of loss or fracture.