Maxillary anterior gingiva and dentoalveolar changes after en-masse retraction between thick and thin gingival biotypes

Abstract

This study compared the changes of gingiva and alveolar bone parameters, including cortical and cancellous bones between thick and thin gingival biotypes after en-masse retraction. Thirty-two adult subjects (mean age, 20.6 years) with maxillary anterior teeth protrusion and proclination were studied and divided into 2 equal groups: thick gingival biotype (TKB) and thin gingival biotype (TNB). Maxillary anterior teeth were retracted using nickel-titanium coil springs at 150 g of force bilaterally for 4 months. Lateral cephalograms, study models, and cone-beam computed tomography scans were taken before retraction and 3 months after 4 months of retraction. Nonparametric tests compared the changes within the groups at these periods and between the groups. The gingiva gained thickness and length (P<0.01) on the labial and palatal sides. The gingival thickness gained more on the palatal side (P<0.01), whereas the length gained equally in both groups. Labial alveolar bone showed increased thickness and height (P<0.01) as opposed to the palatal alveolar bone that presented with loss of thickness and height (P<0.01). The height loss occurred more in TNB (P<0.01). Labial cortical bone increased in thickness and height (P<0.01), whereas palatal cortical bone thinned (P<0.01) at levels in which no cancellous bone was present at the crestal level for TKB and the crestal and midroot levels for TNB. TKB showed slower incisor movement and less retroclination than the TNB (P<0.01) with minimal incisor extrusion. Favorable gingiva and labial bone responses after en-masse retraction were found in both gingival biotypes, whereas more palatal alveolar bone height loss was presented in TNB. Cortical bone thickness decreased when cancellous bone was absent.