[Effect of orthodontic tooth movement on keratinized gingival width]

The relationship between the orthodontic tooth movement and the change of keratinized gingival width was analyzed by measuring the keratinized gingival width and position of the teeth before and after 28 orthodontic treatments.

The photos were matched to the model and the width of the keratinized gingival was obtained by measuring the length of the crown, and the keratinized gingiva. The pre- and post-treatment models were overlapped on rapidform 2006 and the change of tooth position before and after orthodontic movement could be accurately measured, and the relationship between tooth intrusion and extrusion, retraction and forward movement, torque variation and keratinized gingival width was statistically investigated.

Analysis of the correlation between data before and after treatments for 213 teeth in 28 patients revealed a strong correlation between changes in tooth torque angle and changes in keratinized gingiva width (r=-0.47, P<0.001). In the multi-level linear regression analysis, the correlation between them was verified (regression coefficient<0, P<0.001), and there was no significant correlation between the intrusion and retraction of the teeth and the change of the width of keratinized gingiva (P>0.05). Regression coefficient was negatively relative to the reference incisor between the teeth for the canines and premolars (canine regression coefficient=-0.35, premolar regression coefficient=-0.38, P<0.05). Therefore, the study found that there was a strong negative correlation between the changes in tooth torque angle and width of keratinized gingival (r=-0.41, P<0.001), that is, an increase in positive torque led to the reduction of width of keratinized gingiva, and on the contrary the increase of negative torque would cause the width of keratinized gingiva increase. There was no significant correlation between the intrusion and extrusion of the teeth for the width of keratinized gingiva. The sensitivity of different teeth for the width of keratinized gingiva differed, with incisor compared with canines and premolars that were more prone to keratinized gingiva width changes.

Tooth movement during orthodontics affected the width of the keratinized gingiva width, and the increase in positive torque was more likely to cause a reduction in the width of keratinized gingiva. There was no significant correlation between the intrusion and retraction of the teeth and the change in the width of keratinized gingiva. Incisors were more prone to changes in the width of keratinized gingiva relative to the cuspids and premolars during tooth movement. In the orthodontic process, it is possible to predict the effect of changes in the position of the teeth on the keratinized gingiva width, and attention shoud be to the changes in the keratinized gingiva width.