| Objective: This study aimed to compare the smile characteristics ofpatients with different types of malocclusion, to explore that the kinds ofmalocclusion influence the smile characteristics, to provide a theoreticalbasis of clinical diagnosis and treatment for orthodontists.Methods:1The subjects were selected.Inclusion criteria: individuals at the age of18to25, the secondpermanent molar tooth had erupted, the tooth were completed (not includingthe third molars), the width of upper and lower dental arch had no obviousdeformity, anterior tooth had no defact, no abrasion, no cavities, and norepaired history. There were no supernumerary teeth, no embedded teeth.There was no obvious facial malformations, no orthodontic and orthognathictreatment history. Subjects volunteered for the investigation and signed theinformed consent.Grouping criteria: Classâ… : the molars showed classâ… occlusion,0°<ANB<5°, the anterior dental arch had lightly malocclusion; Class â…¡: themolars showed class â…¡occlusion, ANB>5°, the maxillary incisors inclined tolip (U1-SN>112°, U1-NA>28.5°), the anterior tooth had excessive overjet(OJ>3mm); Class â…¢: the molars showed class â…¢occlusion, ANB<0°,crossbie in anterior teeth.In accordance with the inclusiong creteria of Class â… ,60subjects (male30, female30, age21.3±2.5year) were selected from2000students of HebeiMedical University by doing general examination.According to the inclusion criteria of Classâ…¡ and Class â…¢,60subjects ofClass â…¡ and60samples of Class â…¢were selected respectivly from patients in orthodontic department of the Stomatology Hospital of Hebei MedicalUniversity from2011to2012.2Posed smile images were acquired.The selected180subjects sitted on the chair with the head in a naturallyrelaxed position, the Frankfort horizontal plan paralleling to the ground plane.The scale was fixed with the cale and subjects′face in the same plan.15meters in front of subjects, the digital camera was fixed by a tripod, thecamera was seted to get the subjects′s smiling videos by the samephotographer under the natural light at the same place.The vidio for AVI format file was inputed a computer. The whole dymaticprogrss of the smile was browsed fram by fram using Adobe Premiere7.0software, and the posed smile image was selected to convert into JPEG formatand was saved.3The posed smile evaluation3.1Smile qualitative assessment indicator3.1.1Smile type: According to the amout of vertical tooth and gingivaexposure, smile was divided into high smile, average smile and low smile.High smile exposes all of the clinical crowns of the maxillary anterior teethand a contigous band of gingiva tissue, average smile expose75%-100%ofthe maxillary anterior teeth, wheras low smile displys less than75%of themaxillary anterior teeth.3.1.2Smile arc: The smile arc is the relationship between a hypotheticalcurve drawn along the edges of the maxillary anterior teeth and the innercontour of the lower lip in the posed smile. It includes parallel (The curvatureof the maxillary incisal edges coincide with or parallels the border of the lowerlip in smile), flat (The the maxillary incisal edges are flat relative to thecurvature of the lower lip.), reversed (The the maxillary incisal edges arereversed relative to the curvature of the lower lip) and lower lip cover theupper anterior tooth.3.1.3Upper lip curvature: The upper lip curvature is assessed from thecentral position to the corner of the mouth in smiling. It include upware (The corners of mouth is higher than the central position), flate (The corner of themouth and the central position are at the same level) and downware (Thecorners of mouth is lower than the central position).3.1.4The relationship between the upper incisor and lower lip: It includsthat the upper incisor touchs lower lip, the upper incisor untouchs lower lip,and lower lip covers the upper incisal edges.3.1.5The amount of teeth exposured: The number of tooth can be seenwhen subjects smile.3.2Smile quantitative evaluation index3.2.1Buccal corridor rate: It is the ratio between the buccal corridor areaand smile erea. Buccal corridor area is the area between the posterior teeth andthe corner of mouth in smile. Smile erea is the area between the margin ofupper lip and that of lower lip.3.2.2Smile index: It is a comprehensive index that can reflect smilevertical-horizontal relationship. It is the ratio between the smile width andsmile height. Smile width is the distance between bilateral corners of mouth.Smile height is the distance between the upper stomion (the rock bottom ofupper lip margin) and lower stomion (the peak of lower lip margin).3.2.3Smile symmetry rate: It is the ratio between the sum distance fromthe left corner of mouth to the upper stomion and lower stomion and the sumdistance from the right corner of mouth to the upper stomion and lowerstomion.3.2.4Gingiva exposure: The vertical distance between the upper stomionand the left anterio incisor gingival margin.4The smile characteristics were evaluated in the Smile Measure softwareIn the Smile Measure software, the posed smile images were opened. Thesmile assessment indicators were calculated and the data was saved as Excelformat file.5Statistical analysis: The statistical analysis of all the data wereperfermed by spss13.0statistical program.0.05was selected as the statisticalsandard. Result:1The statistical results of the smile typeHigh smile, average smile and low smile covered respectively26.7%,58.3%and15.0%in Class â… , and60.0%,28.3%and11.7%in Class â…¡, and6.7%,18.3%and75%in Classâ…¢.The highest ratio of the smile type was average smile in Class â… , the highsmile in Class â…¡ and low smile in Class â…¢. There were statisticallysignificant difference among the three groups (P<0.05).2The statistical results of the smile arcThe ratios of parallel smile arc, flat smile arc, reversed smile arc andlower lip covering upper tooth were63.3%,23.3%,0%and13.3%respectively in Class â… ,66.7%,23.3%,0%and6.7%in Class â…¡and11.7%,13.3%,5%and70.5%in Class â…¢.The highest ratio of the smile arc both were parallel in class â… and classâ…¡, and was the lower lip covering upper tooth in class â…¢. There werestatistically significant difference (P<0.05).3The statistical results of the upper lip curvatureThe upward, straight and downward upper lip curvature covered71.7%,13.3%and15.0%respectively in classâ… ,48.3%,43.3%and8.3%in classâ…¡and6.7%,30.0%and66.7%in classâ…¢.The highest ratio of upper lip curvature both were upward in class â… andclass â…¡, and was downward in classâ…¢. There were statistically significantdifference (P<0.05).4The statistical results of the relationship between the maxillary incisorand lower lipSubjects whose maxillary incisor touch lower lip, untouch lower lip andlower lip cover the upper incisor covered20.0%,70.0%and10.0%respectively in class â… ,21.7%,71.7%and6.7%respectively in class â…¡, and18.3%,11.7%and70%in class â…¢.The ratio of the upper incisor touching lower lip was the highest in classâ… a nd classâ…¡, in class â…¢that was the lower lip covering the upper incisor, There were statistically significant difference (P<0.05).5The statistical results of the amount of teeth exposureThe amount of teeth exposure in male and female′s posed smile was8.3±1.5,8.6±1.2respectively in classâ… , that was6.5±1.5,6.9±1.3respectively in class â…¡, and8.9±1.7,9.2±1.8respectively in class â…¢. In thethree groups, there were no difference between male and female (P>0.05), nodifference between class â… and class â…¢ (P>0.05). But the amount of the teethexposure in class â…¡ was less than that in class â… and class â…¢ (P<0.05).6The statistical results of buccal corridor rateMale and female′s buccal corridor rates were5.095±1.221,5.490±0.821respectively in classâ… ,6.700±1.237,7.087±1.168respectively in classâ…¡, and5.096±1.505,3.145±1.100respectively in class â…¢. There were no differencesbetween male and female in the three groups.The buccal corridor rates of classâ… , classâ…¡ and class â…¢were5.293±1.051,6.894±1.207and3.121±1.501. There were statisticallydifference between any two groups (P<0.05).7The statistical results of smile indexMale and female smile indexes were5.925±1.010,5.857±0.8213respectively in classâ… ,5.142±0.748,5.690±0.688respectively in classâ…¡, and7.387±0.851,7.265±1.022respectively in classâ…¢. There was statisticallydifference between male and female in classâ…¡ (P<0.05).For male, the smile index was no difference between class â… and classâ…¢(P>0.05). But the smile index of classâ… and class â…¢both were greater thanthat in classâ…¡ (P<0.05).For female, the smile index were statistically significant differencebetween any group in the three groups (P<0.05).8The statistical results of smile symmetry rateMale and female′s smile symmetry rates were1.017±0.049,0.993±0.043respectively in class â… , and0.992±0.026,0.999±0.016respectively in class â…¡,and0.997±0.036,1.015±0.028respectively in class â…¢. There were nodifference between male and female in the three groups (P>0.05). The smile symmetry rates of class â… , classâ…¡ and class â…¢were1.005±0.048,0.995±0.021and1.001±0.036respectively. There were nodifference among the three group (P>0.05).9The statistical results of the amount of gingiva exposureThe gingiva exposure in male and female′s posed smile was1.503±0.957,1.694±0.886respectively in class â… ,1.574±1.296,1.996±1.100respectively inclass â…¡, and0.195±0.564,0.204±0.689respectively in classâ…¢. There wasstatistically significant difference between male and female in classâ…¡(P<0.05).For male and female, there were statistically significant differencebetween any group in the three group (P<0.05).Conclusion: The smile of patients with classâ… tend to show the averagesmile, the parallel smile arc, the upward upper lip curvature and the maxillaryanterior tooth untouching the lower lip, with class â…¡ tend to show the highsmile, the parallel smile arc, the upward upper lip curvature and the maxillaryanterior tooth untouching the lower lip; and with class â…¢ tend to show the lowsmile and the lower lip covering the upper anterior tooth.Malocclusion types may affect smile characteristics, so orthodontistshould base on the smile characteristics of malocclusion to make a targeteddiagnosis and treatment plan for malocclusion. |
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