A proof of concept on implant-supported bilateral cantilever bridges: The T-Bridge approach.

The concept of bilateral cantilevers on a single central implant (T-design) for three-unit implant-supported fixed dental prostheses (ISFDPs) has not been explored nor tested. This technical hypothesis aimed to explore the feasibility of such an approach as a cost-effective alternative to conventional treatments. Careful considerations regarding implant diameter, length, ideal position, occlusal scheme, and bone remodeling are essential to ensure adequate support, stability, and prevention of complications. In this proof of concept, we present a preliminary case with this novel design to replace missing posterior teeth in a patient with narrow bone conditions. In addition, a series of planned investigations and preliminary results, including preclinical studies, are presented to illustrate our concept and its potential clinical implications. Clinically, after two-year follow-up, healthy and stable peri-implant tissues around the ISFDP exemplarily demonstrated excellent stability, functionality, and comfort, which is supported by acceptable fracture resistance data in vitro, suggesting indeed the practical potential and suitability. Thus, we claim that such a treatment modality has the at least theoretical potential to revolutionize implant dentistry by providing innovative and cost-effective treatment options for patients with partial ISFDPs in very specific cases. Of course, further research and evaluations are necessary to validate the clinical implications of this innovative hypothesis. Implementing the 3-on-1 T-bridge approach in partial ISFDPs could offer a promising alternative to traditional methods. If proven successful, this technique may lead to significant advancements in clinical practice, providing a less invasive cost-effective treatment option.

Impact of material combinations and removal and insertion cycles on the retention force of telescopic systems.

OBJECTIVES: A variety of dental materials are available for the fabrication of telescopic crowns. The aim was to investigate the impact of material combinations and removal and insertion cycles on their retention forces. MATERIALS AND METHODS: CAD/CAM-fabricated cobalt-chromium-molybdenum (CoCr) and zirconia (ZrO2) primary crowns were combined with polyetheretherketone (PEEK), polyetherketoneketone (PEKK), CoCr, and ZrO2 secondary crowns (four combinations included PEEK/PEKK secondary crowns in a thickness of 0.5 mm bonded to the CoCr tertiary construction), resulting in 12 different material combinations: CoCr-PEEK; CoCr-PEKK; CoCr-ZrO2; CoCr-CoCr; CoCr-PEEK 0.5; CoCr-PEKK 0.5; ZrO2-PEEK; ZrO2-PEKK; ZrO2-ZrO2, ZrO2-CoCr; ZrO2-PEEK 0.5; and ZrO2-PEKK 0.5 (n = 15 pairings per material combination). Pull-off tests were performed with a universal testing machine initially and after 500, 5000, and 10,000 removal and insertion cycles in a mastication simulator. Descriptive statistics with the Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests were computed (α = 0.05). RESULTS: The tested parameters, material combination, and removal and insertion cycles had significant impact on the retention force values (p < 0.001). An increase in removal and insertion cycles was associated with a decrease in retention forces within CoCr and ZrO2 secondary crowns, regardless of the primary crown material. In contrast, PEEK and PEKK secondary crowns presented higher retention load values after 10,000 cycles than initially. CONCLUSION: Different material combinations behaved differently after simulated removal and insertion regimens. This difference should be considered during treatment planning. CLINICAL RELEVANCE: Telescopic crown systems should be made of materials with predictable retention forces that do not deteriorate with time. The implementation of new materials and technologies facilitates reproducibility and time-saving fabrication.

Fracture load of different veneered and implant-supported 4-UNIT cantilever PEEK fixed dental prostheses.

OBJECTIVES: To determine the fracture load before and after artificial aging of implant-supported 4-unit cantilever fixed dental prostheses (FDP) with frameworks made of two differently filled polyetheretherketone (PEEK) compounds and veneered using three different techniques. METHODS: A total of 120 duplicate 4-unit FDP frameworks were produced (n = 60 milled from PEEK, 20% TiO2 filled and n = 60 pressed from PEEK, 30% TiO2 filled) and veneered using three different techniques: (i) digital veneerings, (ii) conventional resin composite veneerings and (iii) prefabricated veneers (n = 20 per subgroup). The FDPs were adhesively bonded to titanium abutments and the fracture load was measured in a universal testing machine (1 mm/min) before and after artificial aging in a mastication simulator (1,200,000 cycles, 50 N, TC: 5/55 °C, 6000 cycles). The fracture patterns were analyzed using digital microscopy. Data were analyzed using the Kolmogorov-Smirnov test, two-way ANOVA, post hoc Scheffé, Chi2-test (p < 0.05), and Weibull modulus m, as well as fracture patterns using the Ciba-Geigy table. RESULTS: Veneering technique and filler content significantly affected the fracture load (p < 0.001). Prefabricated veneers showed higher fracture load (p ≤ 0.001) whereas digital and conventional veneerings were similar (p = 0.451). PEEK with 30% filler content presented higher fracture load (p < 0.001) compared with PEEK with 20%. Aging showed no effect on fracture load (p = 0.176). Regarding fracture types, no significant differences were found among the groups (p = 0.055). CONCLUSIONS: Filler content of PEEK compound as well as veneering technique influenced fracture load while aging had no effect on fracture load. FDPs made of PEEK with 30% of filler content veneered using prefabricated veneers had the highest fracture resistance.