Fracture Resistance of Posterior Tooth-Supported Cantilever Fixed Dental Prostheses of Different Zirconia Generations and Framework Thicknesses: An In Vitro Study.

The rehabilitation of free-end situations is a frequent indication in prosthetic dentistry. Cantilever fixed dental prostheses (cFDPs) made of 1st and 2nd generation zirconia are one treatment option. Due to a unique gradient technology, combinations of different zirconium dioxide generations are thus feasible in one restoration. However, data about these materials are rare. The purpose of this study was therefore to investigate the fracture resistance and fracture modes of tooth-supported cFDPs fabricated from different zirconia materials (gradient technology) and different framework thicknesses. A total of 40 cFDPs were fabricated using the CAD/CAM approach and belonged to five test groups. The different groups differed in the yttria content, the proportion of the tetragonal/cubic phases, or in wall thickness (0.7 mm or 1 mm). After completion, the cFDPs were subjected to thermal cycling and chewing simulation (1.2 × 106 load cycles, 108 N load). Afterwards, cFDPs were statically loaded until fracture in a universal testing machine. A non-parametric ANOVA was compiled to determine the possible effects of group membership on fracture resistance. In addition, post-hoc Tukey tests were used for bivariate comparisons. The mean fracture loads under axial load application ranged from 288 to 577 N. ANOVA detected a significant impact of the used material on the fracture resistances (p < 0.001). Therefore, the use of cFDPs fabricated by gradient technology zirconia may not be unreservedly recommended for clinical use, whereas cFPDs made from 3Y-TZP exhibit fracture resistance above possible masticatory loads in the posterior region.

Fracture behavior of cantilever fixed dental prostheses fabricated from different zirconia generations.

OBJECTIVE: The aim of this study was to compare the fracture behavior of cantilever fixed dental prostheses (FDPs) fabricated from 3Y-TZP, 4Y-TZP, or 5Y-TZP zirconia. METHOD AND MATERIALS: Posterior cantilever FDPs (three groups, each n = 16) were digitally designed and milled. After sintering, eight specimens/group were stored in demineralized water for 72 hours; eight specimens/group were subjected to accelerated aging using chewing simulation with thermal cycling (1,200,000 × 50 N; 2 × 3,000 × 5°C/55°C; H2O, 2 minutes/cycle) and finally stored in demineralized water for 24 hours. The cantilever FDPs were then statically loaded to failure to determine fracture load. Phase transformation towards the monoclinic phase was controlled with x-ray diffractometry. RESULTS: One failure was identified after accelerated aging in the 5Y-TZP group. Fracture load decreased with increasing yttria content and decreasing bending strength. Accelerated aging using chewing simulation with thermal cycling caused a significant decline in fracture load. All FDPs failed in the area of the prepared tooth and in proximity to the cantilever, where the largest bending moment occurred. The yttria content had no influence on the type of fracture. With increasing yttria content, the relation between deformation and fracture load decreased only slightly. On the surface of FDPs that had been subjected to chewing simulation, no phase transformation towards the monoclinic phase (eg, low temperature degradation) was detected. CONCLUSION: Within the limitations of a laboratory study, the data indicate that 3Y-, 4Y-, and 5Y-TZP may be employed as material for the fabrication of permanent posterior cantilever FDPs. However, more data are necessary to finally advocate the application of 5-Y-TZP. (Quintessence Int 2022;53:414-422; doi: 10.3290/j.qi.b2793243).

Clinical evaluation of zirconia cantilevered single-retainer resin-bonded fixed dental prostheses replacing missing canines and posterior teeth.

OBJECTIVES: This clinical study evaluated the outcome and survival rate of resin-bonded fixed dental prostheses (RBFDPs) made of 3Y-TZP zirconia ceramic with a single-retainer design in the replacement of missing canines, premolars and molars. METHODS: Twenty-one patients that were provided with twenty-seven cantilevered zirconia ceramic RBFDPs replacing maxillary or mandibular missing canines or posterior teeth were recruited from the patients' database at the University of Kiel, Germany. The preparation of the abutment teeth was minimal and limited to the enamel and consisted of a retainer wing and an occlusal rest on the abutment tooth. The restorations were observed over up to 12 years. RESULTS: The patient age ranged from 16 to 72 years old with a mean age of 34 ± 21 years and 57% were females and 43% were males. The restorations were observed for a mean period of 53 ± 39 months with a minimum of 13 months and a maximum of 151 months of observation. No debonding for any of the restorations was detected, which amounts up to a survival rate of 100%. The development of treatable cervical caries on one abutment tooth of an elderly patient without extending to the retainer wing was the only recorded complication. CONCLUSIONS: Zirconia ceramic single-retainer RBFDPs provide an esthetic, functional and minimally invasive treatment alternative to replace missing canines, premolar and molars with promising results due to excellent clinical outcome resulting from a survival rate of 100% and a success rate of 96.3% over a mean observation time of 53 ± 39 months. CLINICAL SIGNIFICANCE: Zirconia ceramic single-retainer RBFDPs might be a valid minimally-invasive option for replacing missing canines and missing teeth in the posterior area especially for young patients, in whom implants are contraindicated and conventional fixed dental prostheses are too invasive.

Ten-year outcome of zirconia ceramic cantilever resin-bonded fixed dental prostheses and the influence of the reasons for missing incisors.

OBJECTIVES: This clinical study evaluated the long-term outcome and survival rate of all-ceramic cantilever resin-bonded fixed dental prostheses (RBFDPs) made of zirconia-ceramic with a single-retainer design to replace missing incisors. In addition, whether the reason for missing incisors has an influence on the longevity of RBFDPs was analyzed. MATERIALS AND METHODS: One hundred and eight zirconia ceramic cantilever RBFDPs were provided for 87 patients. Seventy-five RBFDPs replaced maxillary incisors and 33 mandibular incisors. The restorations were subsequently categorized into 3 groups according to the reasons for missing teeth (congenitally missing, trauma and other reasons). The patients were followed up annually, and the restorations were assessed for function and aesthetics. The mean observation time of the RBFDPs was 92.2±33months. RESULTS: Six debondings and 1 loss of restoration were recorded. The lost restoration was removed at the patient's request after a small chip occurred on the mesial edge of the pontic. Three of the 6 observed debondings were caused by traumatic incidents. All debonded RBFDPs were rebonded successfully with no further complications. Zirconia ceramic RBFDPs yielded a 10-year survival rate of 98.2% and a success rate of 92.0%. CONCLUSIONS: Anterior zirconia ceramic cantilever RBFDPs provided excellent clinical longevity. The reasons for missing incisors did not influence the longevity of the cantilever RBFDPs.

Fifteen-year survival of anterior all-ceramic cantilever resin-bonded fixed dental prostheses.

PURPOSE: The aim of this follow-up study was to report the long-term outcome of all-ceramic cantilever resin-bonded fixed dental prostheses (RBFDPs). MATERIALS AND METHODS: In 16 patients (mean age of 33.3±17.5years) 22 RBFDPs made from a glass-infiltrated alumina ceramic (In-Ceram) were inserted with a phosphate monomer containing luting agent after air-abrasion of the retainer wings. The abutment preparation included a shallow groove on the cingulum and a small proximal box. The restorations replacing 16 maxillary and 6 mandibular incisors were followed over a mean observation time of 188.7 months. RESULTS: No restoration debonded. Two RBFDPs fractured and were lost 48 and 214 months after insertion, respectively. The 10-year and 15-year survival rates were both 95.4% and dropped to 81.8% after 18 years. CONCLUSION: Anterior all-ceramic cantilever RBFDPs exhibited an excellent clinical longevity.