Zirconia resin-bonded fixed partial denture with countersunk holes: a pilot study

The purpose of this pilot study was to evaluate the reten¬tion and durability of zirconia resin-bonded fixed partial dentures (RBFPDs) with countersunk holes in the wings for replacing single anterior teeth. It was hypothesized that the countersunk holes would increase retention. Patients were selected from the dental clinic at Roseman University of Health Sciences College of Dental Medicine, South Jordan, Utah. To be included in the study, patients were missing a central or lateral incisor and had both proximal abutment teeth. The abutment teeth had to be noncarious and have no existing restorations. The RBFPDs consisted of zirconia frameworks with 1 to 3 countersunk holes in the wings and porcelain-fused-to-zirconia pontics. The final prostheses were bonded with light-curing composite resin. Patients were followed up through email, text, and in-person appointments. Of 9 RBFPDs fabricated, 5 remained bonded to the abutment teeth at 3.8, 6.5, 6.5, 6.0, and 3.8 years, for an overall survival rate of 55.6%. A total of 4 RBFPDs debonded at 11 months and 5.1, 5.8, and 6.1 years. In the pros¬thesis that debonded at 5.1 years, a wing fractured at the countersunk holes. Countersunk holes in wings did not enhance retention compared with rates previously reported in the literature for zirconia RBFPDs without countersunk holes. However, the holes appeared to make the wings more susceptible to fracture under long-term occlusal stresses. Case selection, prosthetic design, the patient's occlusal forces, wing thickness, surface area, and operator technique are factors that affect the long-term bonding of zirconia RBFPDs.