Influence of additional reinforcement of fixed long-term temporary restorations on fracture load

Abstract

Purpose: In implant dentistry, temporary restorations (TR) might often be required for up to one year. The aim of this in vitro study was to evaluate the long-time performance of four-unit TRs in the posterior region based on different materials and reinforcement methods.

Methods: One hundred and forty four TRs were manufactured on 16 models simulating an oral situation of two missing posterior teeth. With a computer-aided-design/computer-aided-manufacturing (CAD/CAM) workflow, a TR was fabricated (CAD; Telio CAD), which served as a template for other subgroups. With a vacuum-formed template, unreinforced and reinforced TRs [glass fibres (g; EverStick); polyethylenefibres (p; Ribbond original) and TRs with increased connector area (c; 27.5–35 mm²) ] were manufactured. Two different composite materials were used (C1: Luxatemp,C2: Protemp). Altogether, 16 subgroups with 8 specimens each were tested. After temporary luting (Temp Bond NE) and artificialaging [1600 thermo-cycles (5–55 °C), 240,000 chewing-cycles (50 N) ], all specimens were tested until fracture in a universal testing machine.

Results: After artificial aging, mean fracture loads (N) were: (C1) 201.2 ± 109.7, (C1c) 1033.0 ± 173.1, (C1p) 90.0 ± 40.0, (C1g) 75.9 ± 25.9, (C2) 108.6 ± 58.6, (C2c) 1363.3 ± 148.6, (C2p) 104.7 ± 54.7, (C2g) 50.0 ± 0.0 and (CAD) 232.5 ±19.1. The one-factor ANOVA analysis showed significant differences for the factors temporary material (p < 0.047), reinforcement (p < 0.0001) and artificial-aging (p < 0.0001).

Conclusions: The study indicated that both CAD/CAM TRs and TRs with increased connector areas are suitable for long-term use of one year. No enhancement of fracture load was observed for fibre-reinforced TRs except for the fact that fractured TRs were not totally separated.