Fabrication of Zirconia Abutment Crown and Clasp Under Existing Removable Partial Denture Using CAD/CAM Technology.

This clinical report describes a technique for fabricating a retrofit zirconia crown and clasp for an existing removable partial denture (RPD) using computer-aided design and computer-aided manufacturing (CAD/CAM). A 58-year-old patient developed acute pulpitis of a tooth, and the RPD clasp was broken on the tooth. A pre-preparation scan was captured using an intraoral scanner. The existing RPD was placed in the mouth, and scans of the post-preparation, antagonist arch, and interocclusal record were made. A zirconia crown was designed by superimposing the pre-preparation scan and the post-preparation scan of the abutment tooth. The design data were transferred to a 5-axis milling machine, and the crown was milled from zirconia. The crown was luted using resin cement. An intraoral scan of the crown with RPD was taken, and the RPD was removed to re-scan the proximal guide plane of the crown. The I-bar clasp was designed, and the casting pattern was built using a 3D printer. The pattern was used to cast the clasp. The clasp was set using autopolymerizing acrylic resin to the RPD. The main advantages of this efficient process are that patients can use their RPDs during fabrication of the crown of the abutment tooth. The limitations of using this technique include the cost of the intraoral scanner and the education for the dental clinicians and technicians. In this clinical report, CAD/CAM technology prevented human error, required no adjustment, and uninterrupted use of the RPD for fabricating a retrofit zirconia crown and clasp for an existing RPD.