Alveolar bone thickness and height changes following incisor retraction treatment with microimplants:

Abstract

Objectives To evaluate alveolar bone remodeling following incisor retraction treatment with microimplants and to examine the relationship between crown/root distal movement and thickness/height changes of the alveolus. Materials and Methods A total of 24 patients (mean age, 19.29 ± 4.64 years) with bialveolar protrusion treated by incisor retraction with microimplants were included. The distances of the crown and root tip movements as well as the thickness (alveolar bone thickness [ABT]; labial, lingual, and total) and vertical level (vertical bone level [VBL]; labial and lingual) of the alveolar bone were assessed using cone-beam computed tomography images obtained before treatment (T1) and after treatment (T2). All T1 and T2 variables were compared, and further comparisons of alveolar bone changes were conducted between the two groups based on the distance of the crown (low-crown-movement and high-crown-movement groups) and root movements (low-root-movement and high-root-movement groups). To determine the correlation of the crown or root movement with the variables of alveolar bone changes, Pearson correlation coefficients were calculated. Results Significant differences were found in all VBL and ABT variables after treatment in both jaws but not in total ABT. Based on the crown and root movements, alveolar bone change significantly differed between the root-movement groups, whereas there was no significant difference between the crown-movement groups. In addition, root movement showed significant correlations with the variables. Conclusions Remarkable changes in the height and thickness of alveolar bone were found after microimplant-aided incisor retraction treatment in all groups except for total ABT. Root movement was significantly correlated with the alveolar bone changes.

Bone Remodeling during Orthodontic Movement of Lower Incisors—Narrative Review

“…In two studies, incisor retraction after premolar extraction in class I bialveolar protrusion patients induced changes in the shape of the alveolar mandibular bone [ 29 , 30 ]. Significant vertical bone loss occurred on the lingual side of teeth—2.73 mm in a study by Hung et al [ 30 ] and 3.95 mm in a study by Zhang et al [ 29 ]; the loss on the labial side was smaller but still statistically significant at 0.36 mm and 1.56 mm, respectively. In addition, the horizontal loss of lingual bone at five levels and buccal bone at crestal level was reported by Zhang [ 29 ].…”

“…The results were similar for adults patients [ 26 , 28 , 31 , 32 , 33 , 34 ]. The only “gain” in the measured variable was for buccal thickness of mandibular incisor in bimaxillary protrusion patients treated with extraction therapy [ 29 , 30 ]. The control of retraction movement (more root than crown movement) enhanced preservation on bone height and thickness [ 30 ].…”

“…The only “gain” in the measured variable was for buccal thickness of mandibular incisor in bimaxillary protrusion patients treated with extraction therapy [ 29 , 30 ]. The control of retraction movement (more root than crown movement) enhanced preservation on bone height and thickness [ 30 ]. The results of this narrative review confirm the statements from systematic review by Guo et al They concluded that alveolar bone height and thickness, especially at the cervical level, decreased during both labial and lingual movement of anterior teeth [ 38 ].…”

“…The retraction forces applied to incisors were concentrated at the alveolar crest, producing more evident alveolar bone loss at marginal and mid-root level. When the retraction occurred with more torque than tipping, the buccal thickness increased and marginal bone crest remained at higher levels compared to retroclination movement [ 30 ]. However, on the basis of a meta-analysis, bone remodeling is not stable after retraction.…”

“…The analyzed studies were also not homogenous with regard to the timing of the second CBCT. Some of them were performed after orthodontic treatment [ 23 , 25 , 28 , 29 , 30 , 31 , 32 , 34 , 37 ] and some in the period after particulate tooth movements [ 26 , 27 , 33 ], whereas others—strictly after planned movements [ 35 , 36 ]. Wainwright found in his histological research that once the cortical plate had been penetrated, the buccal surface of the root was deprived of cortical bone.…”