| Objective:This study was conducted to examine the effect of treatmentwith rapid maxillary expansion(RME) and maxillary protraction appliance onthe changes of buccal corridors, through making measurement of theirCephalometric radiographs, models and photos before and after the treatment,and analysis the relevant causes of such changes, aiming to provide referencefor more comprehensive theoretical basis for clinical treatment and helppatients gain more beautiful faces.Method:1Sample Source: Thirty patients who have finished their orthopedictreatment in the Department of Orthodontics, Hospital of Stomatology, HebeiMedical University from October2011to February2013were selected as theresearch objects, including fifteen patients treated with maxillary protractiononly and another fifteen patients treated with the combination of maxillaryprotraction and RME. The inclusion criteria included: age between8~12;anterior crossbite with maxillary hypoplasia; ANB<1°; mesio-molarrelationship; concave profile; no previous orthodontic treatment history; nooperation history; no trauma history or no systemic diseases; complete data inthe X-ray Cephalometric radiographs, research models, photos of faces, anddatum of cases; clear and recognizable relevant measurement mark points.2Sample Grouping: The fifteen patients treated with the combination ofmaxillary protraction and RME were included in Group A (7male and8female with the average age of9.2±1.5years).Another fifteen patients treated with the maxillary protraction only wereincluded in Group B (8male and7female with the average age of8.7±1.8years). Patients in Group A were treated with HAAS expander with the averageexpansion period of12.4±1.3days. The expander was activated two timeseach day and1/4circle each time. The average treatment time in Group Aand Group B was8.5±2.1months and9.1±1.9months, respectively.3Lateral Cephalograms Filming: Lateral cephalograms of the subjectsbefore and after treatment were filmed in head position and in centricocclusion, with frankfort horizontal planes parallel to the floor, slight biting incentric occlusion, naturally relaxed muscle around lip, tongue and month,calm and uniform breathing and no swallowing and all films would be shot byone same technician with CRANEX3+CEPH panoramic X-ray (Finland).4Research Model Casting: The teeth models of the subjects werecollected before and after the treatment with the Haraeus common modelingplastic in proportion used in the Department of Orthodontics. The plastermodels were cast after the plasters were completely hardened, and the modelswere trimmed with the model trimmer and preserved.5Face Photo Acquisition: The photos of faces of the subjects before andafter treatment were collected. They watched right ahead with frankforthorizontal plane parallel to the floor. photos were taken in relaxed rest positionwith closed mouth and lip, then they were guided into natural smile andsimulation smile practice with the pronunciation of English Letter E wascarried out if natural smile could not be achieved, and at last their faces wereshot by the author with the same digital camera CanonEOS40D when theposture smiles were achieved. Then the pictures were input into the computerand preserved in JPEG format.6All lateral cephalograms, research models and photos before (T1) andafter (T2) the treatment were measured and analyzed by the author. The lateralcephalograms were measured in fixed points with Winceph8.06software, andthe magnification was corrected during the measurement process. Verniercaliper (Mitutoyo) was used to measure the arch width of the (primary) canineteeth, first (primary) dentes premolars, second (primary) dentes premolars onthe model, with the accuracy to0.01mm; In the face acquisition, the buccal corridor area ratio of the posture smile face was measured with the SmileMeasure software developed by ourselves. Average values were collected afterthree times of measurement for each item.Statistical Analysis: All data was analyzed by the SPSS13.0statisticalsoftware, and the level was set P＜0.05.Results:After the orthopedic treatment, the anterior crossbite relations in bothgroups were all corrected, and the analysis data indicated that:1Descriptive results of the area ratio between buccal corridors before andafter treatment:The ratio of Group A before treatment was6.62±1.93%, and wasreduced to5.41±2.20%after treatment, so there was significant difference (P＜0.01).The ratio of Group B before treatment was5.93±1.13%, and that aftertreatment was reduced to5.26±1.26%, so there was significant difference(P<0.05).The change amount of Group A and Group B before and after thetreatment were1.22±2.10%and0.57±0.84%, respectively.so there wassignificant difference (P<0.05).2Descriptive results of arch width before and after the correction:The (primary) canine teeth of patients in Group A were30.89±3.22mmand increased to34.39±2.35mm after treatment, their first (primary) dentespremolars were34.32±1.81mm and then increased to38.62±1.55mm aftertreatment, the second (primary) dentes premolars were40.49±1.81mm andincreased to44.84±2.34mm after treatment,so there was significantdifference in all measurements(P <0.01).The second (primary) dentes premolars of patients in Group B were43.59±2.62mm and then increased to44.04±2.56mm after treatment, andthere was significant difference (P<0.05); there was no significant differencein other two measurement indexes before and after the treatment (P>0.05).The change amounts before and after the (primary) canine teeth treatment of patients in Group A and Group B were3.52±2.28mm and0.53±1.51mm,respectively. The changes of first (primary) dentes premolars before and afterthe treatment were4.30±1.27mm and0.43±0.50mm, respectively. whilethoseof second (primary) dentes premolars before and after treatment were4.34±1.73mm and0.45±0.62mm, respectively,so there was significantdifference (P＜0.01).3Descriptive results of projection measurement of soft and hard tissuesbefore and after treatment:The SNA, ANB in Group A increased after treatment (P＜0.01); theSGo/NMe decreased after treatment (P＜0.05); the FMA, LAFH, U1-NAdistance, L1-NB distance and L1-MP increased after treatment (P＜0.05),sothere was significant difference in all measurements.There was no significantdifference in other indicators before and after treatment (P>0.05).The SNA, ANB and FMA in Group B increased after treatment (P＜0.01); the SGo/NMe decreased after treatment (P＜0.05); the LAFH, U1-NAdistance, U1-SN and L1-MP increased after treatment (P＜0.05), and therewas significant difference in all measurements. There was no significantdifference in other indicators before and after treatment (P>0.05).The changes in Group A and Group B before and after the treatment were3.52±2.74mm and1.72±1.14mm, respectively, so there was significantdifference (P＜0.01), while there was no significant difference in changes ofother indicators (P>0.05).4After pearson correlation analysis, the descriptive results of correlationfactors about the changes of buccal corridors were as follows:The changes of buccal corridors are in negative correlation with thechanges of canine teeth width (r=-0.374, P<0.05), the first dentes premolars(r=-0.489，P<0.01), the second dentes premolars (r=-0.453, P<0.05), the ANB(r=-0.339, P<0.01),the L1-NB distance (r=-0.263, P<0.05) and also theL1-MP(r=-0.310, P<0.05).Conclusion:Maxillary protraction combined with rapid maxillary expansion could both make the buccal corridor area ratio smaller. The arc width, sagittalposition of the mandible, and the location mandibular anterior teeth should beconsidered in controlling the size of buccal corridors to gain charming smiles. |
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