Changes In Lip Morphology Due To Orthodontic Treatment With Four Premolars Extracted In Adult Female Patients Of Bimaxillary Protrusion:CBCT Registration Evaluation

ObjectiveThe aim of this study was to evaluate the changes in lip morphology due to orthodontic treatment with four premolars extracted in adult female patients with bimaxillary protrusion by CBCT.Materials and MethodsThirty-one adult female patients (aged23.2±3.4years, age range:19-29,) with Class Ⅰ bimaxillary protrusion were selected from Department of Orthodontic College of Stomatology, Shandong University, during the year from2009to2013. All of the patients were treated by extraction of four first premolars, and banded by Tomy OPA-K straight wire appliance (SWA) technique. Implant anchorage was used during the treatment progress to retract the upper anterior teeth to close the extraction space. The average treatment duration was23.4±2.4months. Pre-and post-treatment CBCT scans of31female adults were taken by Sirona Galileo CBCT, and The CBCT data was saved as DICOM (Digital Imaging and Communications in Medicine) format, and was constructed from Materialism’s Interactive Medical Image Control System (MIMICS, version16.0). This study includes10point parameters of lip morphology, including Cph, Ls, VBa, VBb, VBc, VBd, Ch, Lsto, Sto, Li, which was measured in the horizontal (X), sagittal (Y), vertical (Z) direction. Except Ls, Sto and Li, other point parameters was need to be measured in left and right sides. And11linear parameters, including Cph-Cph’, Is-Cph, VBa-VBa’, VBb-VBb’, VBc-VBc’, VBd-VBd’, Ch-Ch’, Is-Li, Is-Sto, Cph-LSto, Cph-Li, were measured. Linear parameters in the horizontal direction include Cph-Cph’, Is-Cph, VBa-VBa’, VBb-VBb’, VBc-VBc’, VBd-VBd’, Ch-Ch’. Linear parameters in the vertical direction include Is-Li, Is-Sto, Cph-LSto, Cph-Li. Among them, the left and right sides of Cph-LSto and Cph-Li were measured. To evaluate the measurement error of the CBCT cephalometric analysis, the method error was calculated according to Dahlberg’s formula. t-test was used to analyze pre-and post-treatment CBCT cephalograms by using SPSS software (version17.0), at the level of P<0.05. P value less than0.01showed statistically significant.Results1. In this study, the random error of identification in X, Y, Z, was0.32mm (standard deviation:0.12mm),0.30mm (standard deviation:0.14mm) and0.29mm (standard deviation:0.11mm), respectively. The random error of linear measurement was0.30mm (standard deviation:0.14mm).2. The amount of upper incisor retraction at the incisal edge was6.97±0.61mm. The horizontal changes of point parameters of lip morphology between the pre-treatment and post-treatment included:VBb, VBc, VBd, Ch moved to2.39±1.60mm,3.67±1.69mm,2.44±1.10mm和3.15±0.88mm, respectively. The sagittal changes included:Lsto, Sto, Li, Cph, Ls, VBa, VBb, VBc, VBd, Ch retracted5.11±1.10m,5.01±1.42mm,3.88±0.73mm,2.26±1.10mm,3.11±1.17mm,2.91±1.17mm,1.75±0.89mm,2.44±1.10mm and3.15±0.88mm, respectively. The point parameters including Ch, Lsto, Sto in the horizontal direction showed no statistically difference (P>0.05). Cph, Ls, VBa, VBb moved downward1.86±1.02mm,2.68±0.96mm,1.61±0.99mm,2.40±1.28mm.VBc, VBd moved upward1.98±0.85mm,1.82±0.99mm.The horizontal changes of linear parameters of lip morphology between the pre-treatment and post-treatment involved VBb-VBb’, VBc-VBc’ VBd-VBd’ and Ch-Ch’decreased3.91±1.40mm,5.51±1.29mm,3.80±1.04mm and5.67±1.34mm. In the vertical direction, Cph-Lsto, Cph-Li, Is-Li and Is-Sto decreased1.75±1.00mm,3.56±1.40mm,3.12±1.29mm and2.37±0.91mm.ConclusionFor adult female patients with bimaxillary protrusion, lip morphology was changed by applying implant anchorage to retract anterior tooth when four first premolars extracted. In the horizontal direction, the mouth width decreased, and the lip soft tissues far from the center of lip changed significantly than those near the center of lip. In the sagittal direction, lip retracted, and the lip soft tissues which were near the center of lip retracted more significantly than those far from the center of lip. In the vertical direction, the soft tissues in the level of mouth corner had no significant difference, the soft tissues of upper lip and those of lower lip changed significantly.