Labial protuberances of anterior alveolar bone in orthodontic treatment: a case report and literature review

Objective This study aims to explore the influencing factors, formation mechanisms, and treatment methods of labial protuberance in the anterior maxilla during orthodontic treatment, providing a reference for clinical practice. Method This study reports a case where the absence of upper anterior teeth 11 and 21, and the retraction tilting movement of teeth 12 and 22, resulted in labial protuberance and gingival hyperplasia. Alveolar osteoplasty and gingivoplasty were performed. The specific changes in the alveolar bone during the retraction of the anterior teeth and the characteristics of its remodeling were analyzed. Combined with relevant literature, the factors influencing the formation of labial protuberance in orthodontic patients, mechanisms, and methods for prevention and treatment were summarized. Results After periodental surgery follow-up for 6 months, the gingival color and shape of teeth 12 and 22 were good, the labial alveolar bone was normal, and the overall condition was stable. A review of the literature showed that labial protuberance is more common in adult orthodontic patients, and the distance (>4 mm) and speed of retraction of anterior teeth are related to its formation, with the main mechanism likely being differential remodeling of the alveolar bone. In adult patients, the number of active osteoblasts and osteoclasts in the alveolar bone decreases, along with a reduction in metabolic activity and overall cellular activity, which diminishes the reactivity of the alveolar bone. After treatment of anterior teeth retraction, there is insufficient labial bone resorption. Moreover, the lack of mechanical stress-mediated periodontal ligament in the interdental space leads to reduced bone remodeling stimulation in this area, resulting in thickening of the labial alveolar bone of the upper anterior teeth. The remodeling rates of cortical and trabecular bone differ, with active trabecular bone proliferation near the tooth root surface and slow cortical bone resorption near the outer surface, which ultimately results in increased bone thickness at the labial cervical region. Specific case analysis indicates that the retraction distance of the upper anterior teeth in this case was about 6 mm. The alveolar bone at the missing sites of teeth 11 and 21, lacking periodontal ligament stimulation, showed less remodeling and absorption, likely appearing as hyperplasia. The prevention of labial bone protrusion mainly involves controlling the speed and distance of retraction of anterior teeth. Smaller labial protuberances generally do not require treatment, but those affecting function and aesthetics can be addressed with periodontal alveolar osteoplasty. Conclusion After the retraction of anterior teeth in orthodontics, a prominent, hard bone protuberance on the labial side can sometimes occur, which may be due to differential remodeling efficiency in different regions of the alveolar bone. For bone protuberance that influences aesthetics or function, periodontal alveolar osteoplasty can be a reliable option.