Incidence and clinical risk factors associated with the development of labial protuberances after orthodontic treatment.

INTRODUCTION: Distinct, irregular, and hard, nodular labial protuberances (LPs) that were due to differential alveolar bone modeling can be noted on the labial gingival surface of the incisors after orthodontic treatment. Clinically, LPs cause patient discomfort and esthetic issues, but information on this phenomenon is limited. This study aimed to evaluate the incidence of LPs and demonstrate the etiology and clinical risk factors associated with this phenomenon. METHODS: Differential alveolar bone modeling was defined as present (+) when >/=1 distinct LPs (diameter >1 mm) developed after orthodontic treatment by comparing pretreatment and posttreatment intraoral photographs and casts of an orthodontic patient cohort treated with fixed appliances (n = 872). The incidence rate, affected sites, and their association with age, sex, and orthodontic treatment modalities were evaluated. RESULTS: The incidence rate of differential alveolar bone modeling among orthodontic patients was 3.2% (28 out of 872). The maxillary lateral incisor region was the most frequently affected site. Males (vs females) (odds ratio, 2.56 [95% confidence interval, 1.155-5.604]), adults (aged >/= 20 years) (vs teens) (12.84 [3.003-54.866]), and those who had orthodontic extraction (vs nonextraction) (11.60 [3.434-39.156]) demonstrated significantly higher odds of developing LPs after orthodontic treatment (P <0.05). CONCLUSIONS: The incidence rate of the development of notable LPs after orthodontic treatment was 3.2%. Adult males and those who undergo orthodontic extraction have a higher risk of developing LPs. Clinicians should be aware that distinct LPs may develop when large amounts of incisal retraction are planned in adults.