Relationship of Lower Lingual Arch Appliance Use and Impaction of Second Molars: A Retrospective Study.

Purpose: The purpose of this study was to determine the prevalence of permanent mandibular second molar impaction in pediatric patients treated with a lower lingual holding arch (LLHA) to maintain lower arch perimeter. Methods: In this retrospective study, 259 radiographs of nine- to 17-year-old pediatric patients were examined for permanent mandibular second molar impaction. A total of 127 patients with LLHA were compared to a control group of 132 patients who had not received LLHA. Other independent variables (sex and treatment age) were also tested for their value as predictors of impaction difficulty. For statistical analysis, the chi-square test was used. Logistic regression analysis was used to determine the statistical significance of the possible predictors of second molar impaction. Results: The mean age of the subjects was 9.2+/-1.7 (standard deviation) years old. The prevalence of permanent mandibular second molar impaction was 7.1 percent in patients with LLHA compared to 1.5 percent in the control group. The LLHA group had a likelihood of second molar impaction 6.53 times higher than controls after controlling for age. The relationship was significant with P-value of 0.021. Conclusions: The lower lingual holding arch is associated with an increased risk of second molar impaction in patients nine to 17 years old.