Clinical and radiological performance and complications of zirconia implant bridges up to 12 years on function

72X1I ePOSTER CLINICAL RESEARCH – PROSTHETICS

Background: Due to its high biocompatibility, low bacterial surface adhesion, high flexural strength, absence of mucosal discoloration, toughness, and esthetic properties, zirconium oxide has gained popularity and its properties have led to the introduction of zirconia-based restorations in the fabrication of fixed implant-supported prostheses. Despite the broad clinical application of zirconia implant bridges scientific evidence is limited due to the lack of long-term data.

Aim/Hypothesis: To retrospectively evaluate clinical and radiological outcomes of screw-retained zirconia implant bridges (ZrPIB) up to 12 years. To investigate for any difference of screw-retention at implant and abutment level. To assess long-term reliability of moderately rough oxidized surface implant.

Materials and Methods: A retrospective chart review of partially and fully edentulous consecutive implant patients, male and female, aged ≥ 18 years, treated with implant supported screw retained fixed dental prostheses in three private dental clinics (AP, GF, GS) between December 2004 and June 2017 was conducted according to strict inclusion and exclusion criteria. One clinician for each center performed all the surgical and prosthetic procedures, and three dental laboratories, qualified in CAD/CAM technology designed and manufactured the screw retained porcelain fused to zirconia implant prosthesis. Outcomes were implant and prosthetic survival rates, prosthetic success rate, mechanical and biologic complications, marginal bone level (MBL) change, soft tissue condition. Effects of bridge type and level, implant type and connection, and follow up on MBL were tested (P < 0.05) through a Generalized Linear Effects Model (GLMM).

Results: Ninety-eight patients, 59 (60.2%) female and 39 (39.8%) male, in most cases (86.4%) between 50 and 80 years old (mean 60.7 ± 11.7, median 62 ± 1.1, minimum 21 maximum 84), accounting for a total of 337 implants and 111 bridges were eligible to be included and investigated. No zirconia fractures were reported. Two implants and 2 ZrPIBs failed, yielding to a cumulative implant and prosthetic survival rate of 99.4% and 98.2%. Chipping was the most common complications (13.5%), accounting for a cumulative prosthetic success of 91.9% over an observation time of ≥ 10y (40 ZrPIBs, 36%), 5 to 9y (38, 34.2%), 2 to 4y (33, 22.8%). MBL change was -0.18 ± 0.59 mm. Thirteen implants experienced peri-implantitis (3.8%), 9 mucositis (2.7%). Low significance of implant level vs abutment level bridges (P = 0.013) was found, with higher MBL observed in ZrPIBs delivered at implant level (P = 0.013). Successful soft tissue parameters and patient satisfaction were reported.

Conclusions and Clinical Implications: Within the limitations of this retrospective study, ZrPIBs are a reliable treatment option for partial and complete edentulism long-term. Stable bone levels and low peri-implantitis rate confirm positive performance of moderately-rough oxidized-surface implants supporting screw retained ZrPIBs. Screw-retention at implant level is not detrimental to bone and soft tissue integration. Zirconia fracture and porcelain chipping might be limited with well-managed laboratory and clinical protocols.

Keywords: CAD/CAM, zirconia, complete-arch, screw-retained, dental implants