Three-dimensional CBCT Evaluation Of Mandibular Anterior Alveolar Bone Morphological After Incisor Retraction In Adult Dental Extractions Patients With Bimaxillary Protrusion

Objective:The purpose of this study was to evaluate three-dimensional (3D) dehiscence of mandibular anterior alveolar bone morphological after incisor retraction and intrusion in adult patients with bimaxillary protrusion.Methods:Twenty adult patients (12 females and 8 males; aged from18 to 23 years, mean age:20.7 years; SD:2.4 years) with bimaxillary protrusion had four first premolars extracted, and then miniscrews were placed to provide anchorage. A CT scan was performed before incisor retraction and again posttreatment. Three-dimensional (3D) reconstruction of the pre-(T1) and post-(T2) CT data was used to assess for morphological changes of the mandibular anterior alveolar. A paired t-test was used to compare changes from T1 to T2.Results:1. The amounts of mandibular incisor retraction at the incisal edge and apex were 5.03±1.34mm and 3.34±1.29mm, respectively. 2.The mandibular anterior alveolar labial and lingual thickness were reduced after incisor retraction (P<0.05). The decrement of mandibular incisor lingual cemento enamel junction(CEJ) at 3mm、6mm、9mm is 1.14±0.50mm、0.92± 0.39mm、0.71±0.30mm; The decrement of mandibular incisor labial cemento enamel junction(CEJ) at 3mm、6mm、9mm is0.85±0.58mm±0.41±0.33mm、 0.35±0.13mm. 3. The mandibular anterior alveolar labial and lingual height were reduced after incisor retraction (P<0.05).The height of labial reduced 2.82±1.10mm, The height of lingual reduced 3.42±1.80mm.Conclusions:For adult patients with bimaxillary protrusion, We should pay more attention to the change of mandibular anterior alveolar.