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

Purpose: 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.

Materials and methods: 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.

Results: 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.

Conclusions: The inclusion of an FRC framework significantly enhanced the fracture strength of the FDPs. While the aging protocol did not alter the strength, failures predominantly occurred in the 3D-printed resin superstructure at the connectors. The highest rate of fractures occurred in the premolar connector.