Evaluation of the failure strength of different fixed reinforcement devices used after orthodontic treatment: an in vitro study

Aim: The fracture strength of 3 types of retention devices and 2 kinds of composite materials are examined and compared with laboratory tests. Material and Method: In total, 48 samples were formed in duplicate pairs with 96 lower incisor teeth. The 48 sample blocks were then randomly divided into 6 groups, with 8 samples per group. 3 different types of retainer and 2 different composite materials were used. The wires used are: Penta-one (0.0215-inch round wire), Remalloy (0.032-inch plain round wire) and Dead wire (10x28). Composite materials: Tansbond XT (3M Unitek, Monrovia, CA) and Transbond LR (3M Unitek, Monrovia, CA). The rupture strengths of the retention devices used were measured with the MTS brand (Criterion Model, USA) C42.503 universal test device. Results: There was a statistically significant difference between the groups in terms of peak tension and peak load averages (p: 0.000, p <0.05). Peak tension and peak load averages of Remalloy group were statistically higher than Penta-one and Dead wire groups (p <0.05). Peak tension and peak load averages of penta-one group were statistically significantly higher than dead wire group (p <0.05). Statistically, between peak stress and peak load levels; there was a significant difference between the wires (p: 0.000, p <0.05). There was no significant difference between the composites (p: 0.088; p> 0.05). The joint effect of wire and composite was not statistically significant (p: 0.466; p> 0.01). Conclusion: The highest breaking strength among the retainer wires was Remalloy, then Penta-one, the most unstable Dead wire. Transbond XT is more durable than Transbond LR among composites, but this difference is not significant difference. Three types of retainer tears were found sufficient in terms of fracture strength. Key Words: Strengthening, retention, retainer, relapse, recurrence, orthodontics.