Comparison of cortical bone thickness changes in Madibular anterior region during retraction using TADS-a CBCT study

Introduction: To evaluate and compare the labial and lingual cortical bone thickness in mandibular anterior segments during en masse retraction using skeletal anchorage aided by micro implants. Methods: The study was done in-vivo on 10 subjects, with angle’s class i bi-maxillary protrusion and/or angle’s class ii div 1 protrusion patients between the age group of 18-30 years in the permanent dentition. Pre-treatment and post treatment CBCT’s were taken for all the patients. Titanium small head micro implants, were used as anchor units for en-masse retraction. Changes in cortical bone thickness were measured at cervical (s1), middle (s2) and apical (s3) regions. Results: One-way Anova test and Paired t test were performed on the given data which stated that statistically significant increase in cortical bone thickness was seen in at s1,s2&s3 on the lingual aspect with a p value of <0.001,whereas on the buccal aspect there was significant decrease only in left lateral incisors at s2 and s3 after retraction. Conclusion: This current study concluded that orthodontic retraction force causes significant change in the thickness of cortical plates ie: reduction in thickness along the direction of force and differential remodelling at s1, s2 &s 3. Decrease in lingual cortical plate thickness was seen after correction of inclination and retraction of mandibular anterior segment.