Assessing the feasibility of a stainless-steel lingual fixed retainer on mandibular anterior dentition with orthodontic-related labiolingual alveolar bone resorption: A finite element analysis.

Objective: This study aimed to evaluate the use of a stainless-steel fixed retainer for post-orthodontic retention in patients with labiolingual alveolar bone resorption in the mandibular anterior segment.

Methods: Three mandibular anterior segment models (with or without labial or lingual alveolar bone resorption) with 0.5-mm-diameter retainers bonded to all teeth were constructed. Two occlusion schemes were simulated: a 285.3 N force applied to four mandibular incisors (incisor biting) and a 93 N force applied to the left canine (laterotrusion). The tooth displacement and stress distribution in the periodontal ligament (PDL), retainer, and composite were evaluated.

Results: Compared to no resorption, labial bone resorption significantly increased tooth displacement and PDL stress concentration in the central incisors during incisor biting, whereas lingual resorption had a greater effect on the guiding canine during laterotrusion. The retainers were susceptible to stress concentrations in the resin-uncovered area, mesial region of the lateral incisors under incisor biting, and mesial region of the guiding canine under laterotrusion. For the composite, the composite-retainer interface was prone to stress concentrations, especially in the mesial or distal extremes of the adhesive composite of the incisors.

Conclusions: A 0.5-mm-diameter stainless-steel lingual retainer bonded on all teeth is a clinically acceptable retention procedure for patients with lingual bone resorption in the lower anterior region. However, it should be used more cautiously for patients with labial bone resorption as it exposes the lower central incisors to a greater risk. Excessive stress on the retainer and composite due to the occlusion force may lead to unwanted tooth movement, necessitating closer monitoring.