Impact of aging on the fracture strength of 3D-printed fixed implant prostheses: A comparative analysis of monolithic and bi-layer with or without fiber-reinforced composite frameworks.

Abstract

This study aims to evaluate the fracture strength of three-unit, implant-supported fixed dental prostheses (FDPs) constructed from 3D-printed resin. It compares structures with and without fiber-reinforced composite (FRC) frameworks under conditions that mimic artificial aging. Forty FDPs were fabricated and divided into two groups: monolithic (n=20) and bi-layer (n=20). The monolithic group (MG) consisted entirely of FDPs made from 3D-printed resin for permanent restorations, while the bi-layer group (BG) featured FDPs with an FRC framework veneered with the same 3D-printed resin. Each group was subdivided into two subgroups: one subjected to artificial aging (MTG, n=10; BTG, n=10), and the other served as the baseline control (n=10). All subgroups underwent a mechanical bending test, applying a single load to failure using a universal testing machine. There was a statistically significant difference in fracture strength due to the presence of the FRC framework (p<0.01). The framework became the FDP more resistant to load. The mean load to failure and standard deviations were as follows: MG 406.59N (±33.84), MTG 286.20N (±152.15), BG 1142N (±162.88), and BTG 945N (±211.52). Although no statistical differences in strength were observed between aged and nonaged subgroups, variations in failure patterns emerged, with the BG and BTG groups showing a predominance of failures compared to the MG. The inclusion of an FRC framework significantly enhanced the fracture strength of the FDPs. While the aging protocol did not alter thestrength, failures predominantly occurred in the 3D-printed resin superstructure at the connectors. The highest rate of fractures occurred in the premolar connector.