Evaluation of the epithelial cells of lower lip mucosa after debonding of fixed orthodontic appliances.

Background: Orthodontic appliances (ligatures, braces, wires, etc.), are one of the main sources of trauma in the oral cavity. Friction between brackets and mucosa is a kind of chronic trauma that may cause buccal mucosal proliferation and ulceration and is one of the most common complaints of patients during orthodontic treatment. The aim of this study was to evaluate the changes of the lower lip epithelial cells after the removal of orthodontic fixed appliances.

Methods: Cells of lower lip oral mucosa of 31 orthodontic patients were collected by exfoliative cytology in three times: immediately (T0), 30(T1) and 60 (T2) days after debonding. Nuclear (NA) and cytoplasmic (CA) areas, NA/CA ratio, cell morphology and cellularity of smears were evaluated using cytomorphometric and cytomorphologic methods. Friedman test followed by the Wilcoxon test was used to compare the NA, CA and NA/CA values in three different times. Cell morphology and cellularity were analyzed by the Chi-square test. All statistical tests were performed with SPSS version 20.

Results: The NA and CA values increased significantly (P<0.001) after the removal of friction and irritation of orthodontic appliances in T1 and T2 and reached their highest level in T2. The NA/CA values did not change significantly (P=0.25). Class I smears, according to Papanicolaou classification, were observed in T0, T1, and T2. Superficial epithelial cells were predominant cell types in the lower incisor region in all times without statistically significant difference in three intervals.

Conclusions: Orthodontic appliances increase keratinization of lip mucosa which is considered an adaptive reaction to the mechanical stimulus, but after removing of the appliances cellular activity rapidly increases. Keratinization is the main change observed at the end of orthodontic treatment.