Objective: In vitro laboratory testing of dental materials is an important precursor to clinical testing. Fracture resistance is a frequently used laboratory test, which is used to rank dental materials, let alone different techniques. A limitation of this type of testing is the absence of a periodontal ligament analogue. The objective of this study was to investigate the effect of two periodontal ligament analogues on the fracture resistance of typodont teeth. Methods: Thirty typodont teeth (Riverside Dental Manufacturers, London, UK) were randomly allocated to three groups (n=10). The teeth in Group I were covered with a 1mm thick layer of a periodontal ligament analogue, in this case a polyether impression material, (Impregum, 3M ESPE (UK) Ltd). The teeth in Group II were covered with an addition cured silicone impression material (Aquasil, Dentsply, (UK) Ltd) to simulate the periodontal ligament whilst the control teeth (Group III) were untreated. Following mounting in acrylic resin the teeth were loaded to fracture. Results: The mean (mean, s.d.) fracture resistance (N) of the restored teeth was as follows: Group I (828.80, 144.25), Group II (1455.70, 414.40) and Group III (1383.20, 377.60). Groups II and III had significantly greater mean fracture strengths than Group I (p=0.01). There was no significant difference (p=0.88) between Groups II and III. The level of static occlusal loading permitted with the analogue periodontal ligaments tested was similar to natural biting forces. Conclusion: Within the limitations of this in vitro study it is concluded that the periodontal ligament analogues tested considerably enhanced the fracture resistance of typodont teeth.

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