The Study Of Correlation Between The Smile Aesthetic Characteristics And The Related Maxillofacial Characteristics

Objectives: The present study tries to evaluate the posed smile in young women and analyze the correlation between the posed smile aesthetic characteristics and the related maxillofacial characteristics, aiming at providing guideline for better designing and prognosis of smiling in clinical practice.Methods: Standard digital facial photos including posed smile position and rest position were taken form 120 young women.Qualitatively photographic analysis to smile line and smile arc were carryed out and Digiizer immage software was employed to measure corresponding esthetics parameters including buccal corridor and smile index. moreover, the parameters of the maxillofacial characteticris and the width of the canine, premolar and molar teeth were also evaluated form the lateral cephalograms images and dental casts. The statistic comparison was carried out to analysis the individual variation and the correlation between the posed smile aesthetic characteristics and the related maxillofacial characteristics.Results: 1. Among the lateral cephalometrics and dental cast variables,the ratio of upper lip length,Stms-Stmi,ANB,FMA,Y-axis,OP-FH,U1 exposure,U1-PP,U1-SN were significan-tly correlated with smile line(P <0.05). The high smile exsits mainly in the patients with skeletal class II relationship and vertical growth pattern. 2. SNB,Y-axis,FMA,S-Go/N-Me,OP-FH,U1-SN,U1-NA,U1 exposure were signific-antly correlated with smile arc(P <0.05),flat smile arc mainly exsits in the horizontal growth pattern.3. Buccal corridor line ratio negatively correlated with FMA,Premolar width(r=-.378, P <.001;r=-.287, P <.001) and correlated positively with A-Nper(r=.315, P <0.001),Skeletal class III and horizontal growth pattern tends to display a more buccal corridor space. 4.Smile index has negative correlation with U1 exposure(r =-.390, P <. 001) and has positive correlation with the ratio of upper lip length(r =. 349, P <. 001).Conclusion: 1.Smile line is related to the mandibular position,the ratio of upper lip length,anterior vertical maxillary excess and U1 position,to treat gummy smile,we should analyze the cranial and maxillofacial mechanism and formulate reasonable treatment design. 2.Smile arc is related to FMA, OP-FH and U1 position, Hence, occlusion plane and incisor torque should be controlled precisely during orthodontic treatment to avoid flatting smile arc. 3. The buccal corridor reduction could be achieved by increasing the mandibular plane Angle, expanding upper dental arch width and moving forward maxillary. 4. It is essential to harmonize the incisor ridge and the upper lip as the close correlation between smile index and U1 exposure and the ratio of upper lip length.