Comparison of porcelain veneer fracture in implant-supported fixed full-arch prostheses with a framework of either titanium, cobalt-chromium, or zirconia: An in vitro study.

OBJECTIVES: The aim of this study was to compare porcelain veneer strength on screw-retained implant-supported fixed full-arch prostheses with a framework of either milled titanium (Ti), cobalt-chromium (CoCr), and yttria-stabilized zirconia (Y-TZP) in an in vitro loading model. MATERIALS AND METHODS: Fifteen screw-retained maxillary implant-supported full-arch prostheses (FDP), five each of Ti, CoCr, and Y-TZP frameworks with porcelain veneers were included. All FDPs were subjected to thermocycling before loading until fracture of the veneer. The load was applied at the distal fossa of the occlusal area of the pontic replacing 24. Fracture loads were analyzed, and the fracture quality was assessed. Statistical analysis on the fracture load was performed using Kruskal-Wallis test. The statistical significance was set at p < .05. RESULTS: There was no statistical significance found between the groups regarding fracture load. The highest and lowest load was seen within the CoCr FDP, varying between 340 and 1484 N. Different types of fracture appearances were seen. The Y-TZP FDPs had a higher number of fractures locally in the loaded area while CoCr and Ti more often showed cracks in the anterior region, at a distance from the loaded area. CONCLUSIONS: Within the limitations of this study, the conclusion was that framework material may affect the fracture behavior of maxillary full-arch bridges; however, there were no differences in veneer fracture strength when frameworks of Ti, CoCr, or Y-TZP were compared.

Early Cup Loosening After Metal-on-Metal Total Joint Replacement of the Trapeziometacarpal Joint: A Retrieval Study.

PURPOSE: To investigate the possible mechanisms behind early cup loosening in a metal-on-metal trapeziometacarpal joint replacement. METHODS: The trapezia from 5 female patients were removed as part of a salvage procedure after a median of 22 months (range, 7-43 months) after implantation. Three osteoarthritic patients with symptomatic cup loosening and 2 with instability had a median age of 62 years (range, 59-65 years) at primary surgery. The trapezia with cups in situ were preserved and processed for histomorphometry. Studies with laser ablation inductively coupled plasma mass spectrometry and scanning electron microscopy with energy dispersive x-ray spectroscopy were also performed on 2 of the specimens. RESULTS: In all 5 specimens, osteolytic lesions undermined the cups and were also seen at the cup edges, completely surrounding the loose cups. Large amounts of dark particular material were seen in the periprosthetic tissues, mostly internalized by macrophages. The presence of chrome and cobalt in these regions was confirmed. Four of the 5 cups showed marked or complete loss of hydroxyapatite. CONCLUSIONS: We have found several possible explanations for the poor performance of this cup, including its cannulated design and metal-on-metal bearing. The changes seen are early and advanced, raising serious concerns about the implant and particularly the articulation. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic V.

Bone tissue response following local drug delivery of bisphosphonate through titanium oxide nanotube implants in a rabbit model.

OBJECTIVES: The objective of this study was to evaluate whether surface chemistry-controlled TiO2 nanotube structures may serve as a local drug delivery system for zoledronic acid improving implant-bone support. METHODS: Twenty-four screw-shaped Ti implants with surface chemistry-controlled TiO2 nanotube structures were prepared and divided into a zoledronic acid-formatted test and a native control group. The implants were inserted into contra-lateral femoral condyles in 12 New Zealand White rabbits. Bone support was evaluated using resonance frequency analysis (RFA) and removal torque (RTQ), as well as histometric analysis following a 3-weeks healing interval. RESULTS: Zoledronic acid-formatted TiO2 nanotube test implants showed significantly improved implant stability and osseointegration measured using RFA and RTQ compared with control (p < 0.05), and showed significantly enhanced new bone formation within the root of the threads compared with control (p < 0.05). CONCLUSIONS: TiO2 nanotube implants may prove to be a significant delivery system for drugs or biologic agents aimed at supporting local bone formation. Additional study of candidate drugs/agents, optimized dosage and release kinetics is needed prior to evaluation in clinical settings.