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

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.

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; 27.5-35mm²)] 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 artificial-aging [1600 thermo-cycles (5-55°C), 240,000 chewing-cycles (50N)], all specimens were tested until fracture in a universal testing machine.

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).

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.