Detection of apoptosis in human periodontal ligament during orthodontic tooth movement

Abstract

Aim: To compare distribution of apoptotic cells in the Periodontium following Orthodontic force application, to study the apoptotic index and co-relate with different phases of tooth movement. Material and methods: 100 patients, age 12-20 years, of class II div 1 malocclusion, were randomly divided into Groups I to V, requiring first premolars extraction with fixed Mechanotherapy. After leveling, canine was retracted using closed coil spring (100 gm forces). Surgical extraction of premolar was performed on 0, 3,7,14 & 21 days. Periodontium tissue was processed and apoptosis was evaluated by TUNEL assay. Apoptotic cells were counted from 4 different fields per slide and compared with the basal group. Results: The mean Apoptotic Index increased from day 3 and peaked at day 7 for both compression and tension sides. On tension side, at days 14 & 21 apoptosis wasn’t significant indicating earlier recovery. On compression side, there is more gradual decrease in apoptosis with lowest mean values at day 21, though not same as the basal level, indicating that the periodontal tissues require more than 21 days for complete recovery. The overall difference in apoptotic rate was statistically significant for both compression and tension sides. Conclusion: Tissue response is a time-dependant normal physiological process where periodontal cells are cleared by apoptosis. The correlation coefficient value indicates the apoptotic activity increased with force on compression side & increased significantly on tension side too, signaling towards force-dependant direct relation between the two. Cells on tension side showed a more rapid rate of recovery as compared to compression side. Keywords: Periodontium, Orthodontic, Mechanotherapy, Force-dependant