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

Area of Science:

• Dental Materials Science
• Prosthodontics
• Biomaterials Engineering

Background:

• Zirconia resin-bonded fixed partial dentures (RBFPDs) offer a conservative approach for replacing missing anterior teeth.
• Enhancing the retention and durability of RBFPDs is crucial for long-term clinical success.
• The role of design modifications, such as countersunk holes, in RBFPD performance requires further investigation.

Purpose of the Study:

• To evaluate the retention and durability of zirconia RBFPDs with countersunk holes in the wings for single anterior tooth replacement.
• To test the hypothesis that countersunk holes would increase the retention of zirconia RBFPDs.
• To assess the long-term survival rate and identify failure modes of these RBFPDs.

Main Methods:

• A pilot study involving patients with missing single anterior teeth and suitable abutment teeth.
• Fabrication of zirconia RBFPDs with 1 to 3 countersunk holes in the wings and porcelain-fused-to-zirconia pontics.
• Bonding of prostheses using light-curing composite resin, followed by clinical follow-up for up to 6.5 years.

Main Results:

• Five out of nine (55.6%) zirconia RBFPDs remained bonded after a mean follow-up of 3.8 to 6.5 years.
• Four RBFPDs debonded between 11 months and 6.1 years.
• One debonded prosthesis showed wing fracture at the countersunk holes, suggesting increased susceptibility to fracture.

Conclusions:

• Countersunk holes in zirconia RBFPD wings did not enhance retention compared to literature values for RBFPDs without such modifications.
• The presence of countersunk holes may compromise the long-term durability by increasing susceptibility to fracture under occlusal stress.
• Optimal case selection, prosthetic design, and operator technique are critical factors influencing the long-term success of zirconia RBFPDs.