Comparative Assessment of Failure Rate of Fixed Lingual Retainer in Finished Orthodontic Cases Between Two Types of Light cured Resin Composite: A Randomized Clinical Trial.

Aim: The objective of this 2-arm parallel trial was to determine rate of each failure mode (Adhesive/Cohesive) of bonded fixed lingual retainer using two light cured resin composite Transbond XT and Transbond LR. Materials and Methods: 90 patients requiring a canine to canine lingual retainer were randomly divided into two groups according to the resin used for bonding procedure TRANSBOND XT (XT) and the lingual retainer composite TRANSBOND LR (LR). Failure modes varied by tooth, with tooth 43 showing the highest adhesive failure frequency and teeth 42 (LR) and 41 (XT) showing the highest cohesive failures, suggesting tooth-specific factors may influence retainer performance. Monthly visit were carried out over 6 month follow up to assess any detachment occurring on teeth of both arches. All the data were submitted to statistical analysis. Results: XT showed more adhesive failures than LR: (72%) vs (42%). LR showed more cohesive failures than XT: (58%) vs (28%). Conclusion: Group XT showed more adhesive failures and Group LR more cohesive failures, indicating differing mechanical properties; XT had weaker interfacial adhesion, while LR showed weaker internal cohesion.