Fracture Load Comparison of a New Fiber-Reinforced Composite and Zirconia in All-on-4 Prostheses: An In Vitro Study

To compare the fracture load of two framework materials-zirconia and a new fiber reinforced composite (FRC Trilor)-for full-arch, implant-supported rehabilitations using various cross-sections.

A cobalt-chromium metal model simulating the All-on 4 concept and including two anterior straight and two posterior 45-degree, multiunit digital implant analogs was manufactured. Four straight multiunit abutments were screwed onto the implant analogs. The metallic model was scanned, and 18 frameworks were fabricated, with 9 made of zirconia and 9 made of FRC Trilor. The frameworks were then divided into six groups (n = 3). Group division was based on the material type (zirconia or FRC Trilor) and framework cross-section: 3.5 × 6 mm2, 5.5 × 6 mm2, or 7.5 × 6 mm2. All specimens underwent thermocycling in two baths, were cemented to the abutments of the metal model, and were subjected to a load-to-failure bending test at three different points using a universal testing machine (crosshead speed: 1 mm/minute) until complete fracture occurred. Descriptive statistics were used to present quantitative variables as means ± SDs. To compare two means, Student t test or Mann-Whitney test was used, and ANOVA test was used for three means.

The FRC Trilor group with a 7.5 × 6 mm2 cross-section exhibited the highest load-to- failure values (ranging from 1,020 N to 2,994 N), while the zirconia group with a 3.5 × 6 mm2 cross-section recorded the lowest values (ranging from 212 N to 1,287 N). The material type and framework cross-section significantly affected the mean load-to-fracture values (P < .05). Regardless of the framework cross-section, the FRC Trilor group exhibited higher fracture loads than the zirconia group. In both materials, fracture load values increased with larger framework cross-sectional areas, with the highest values observed at the interimplant midpoint.

FRC Trilor demonstrated a fracture load that makes it a suitable alternative to zirconia for All-on-4 implant prosthetic frameworks.