| ObjectiveTo explore the forehead features of skeletal class I malocclusion population of Guangxi region with good facial harmony and its relationship with the position of the upper incisors,and to establish a prediction model for the ideal position of the upper incisor.To preliminarily verify its applicability in orthognathic patients,in order to provide reference for orthognathic preoperative planning of maxillary positioning.Methods(1)Profile photographs and lateral cephalograms of female patients of Guangxi medical university hospital of stomatology with skeletal class I relationship and good facial harmony were included and overlapped according to the upper 2/3 facial silhouette.The distance between the forehaed landmarks and upper incisors,including the distance between Glabella point,Superion point,the forehead facial axis(FFA)point and the perpendicular line passing the facial axis point of upper incisors(FA perp),and the forehead features,including forehead height,forehead depth and forehead inclination of the patients were measured respectively.An goal anterior limited line(GALL)model of the upper incisors based on forehead features was built.(2)Postoperative photographs and lateral radiographs of orthoganathic patients of Guangxi medical university hospital of stomatology were included to measure the distance between upper incisor FA perp and GALL and classic cephalometric indicators(SNA,A-N perp,maxillary length);Profile images were made into silhouettes,and 30 evaluators used Visual analog scale(VAS)scale to evaluate the silhouettes.According to the VAS score,patients were divided into high(first 1/3),medium(middle 1/3)and low score(last 1/3)groups,and the differences in the four indicators mentioned above among the groups were compared.At the same time,Z-score was used to standardize the above four indicators,and the degree of deviation between each indicator and its reference value was compared.(3)Patients with skeletal III malocclusion undergoing two-jaw surgery were enrolled with computed tomography before surgery and more than 3 months after surgery.In Proplan CMF 3.0,preoperative bone segments were moved and matched with the postoperative bone,and postoperative prediction images were generated based on preoperative soft tissue images.The differences in nasal cavity,left/right nasal parafasal,upper lip,lower lip,mental region,nasolabial angle,upper lip height and upper lip width between the actual and predicted soft tissue were compared.At the same time,the correlation between the above indicators and the sagittal,horizontal and vertical movement of the maxilla were calculated.(4)One male and one female with skeletal III malocclusion were included,and the patient’s profiles,cephalograms,computed tomography,and three-dimensional(3D)face scan 1 week before surgery were collected.The operation and jaw localization were simulated in Pro Plan CMF 3.0,and the upper incisor was positioned on GALL,and the mandible was matched with the maxilla based on 1-3mm overjet and overbite.Soft tissue 3D predictive image was generated as an experimental group(GALL group).Control groups were set at a 2 mm interval anterior or posterior the GALL to generate a series of soft tissue 3D predictive images.The 3D predictive images obtained were ranked according to facial attractiveness by 30 orthodontic doctors and 30 laypeople.Results(1)A total of 86 samples were included.Mean forehead height was 49.87±5.60mm,mean forehead depth was 20.49±5.01mm,and mean forehead inclination was 14.73±4.24°.Regression analysis showed that the statistically significant correlation between forehead inclination and the distance between upper incisor FA perp and superion point and between upper incisor FA perp and FFA point(P<0.0001),forehead height and the distance between upper incisor FA perp and glabella point(P=0.0039)and forehead depth and the distance between upper incisor FA perp and superion point(P<0.0014)were detected.Pearson correlation analysis showed the strong correlation between forehead inclination and the distance between upper incisor FA perp and superion point(R~2=0.6387),followed by forehead inclination and the distance between upper incisor FA perp and FFA point(R~2=0.3459)and the R~2of the others were less than 0.2.The linear regression model was applied to construct a prediction model based on the distance between the forehead inclination and the distance between upper incisor FA perp and superion point.(2)A total of 72 samples,consisting of 30 males and 42 females,were included.There were no statistically significant differences in SNA,maxillary length,A-N perp among high,medium and low VAS groups,and GALL in high VAS group had statistically significant differences with medium VAS group and low VAS group(P<0.05).The Z-score of GALL in high,medium and low VAS groups was 0.07,-0.63 and 0.60,respectively.The order of Z-score in VAS high group were GALL(0.07),A-N perp(-0.13),SNA(-0.59)and maxillary length(-0.78).The order of Z-score in VAS medium group were A-N perp(0.24),SNA(-0.32),GALL(-0.63)and maxillary length(-0.66).The order of Z-core in VAS low group were A-N perp(0.01),SNA(-0.42),GALL(0.60)and A-N perp(-0.63).(3)A total of 16 samples,consisting of 10 males and 6 females,were included.The prediction accuracy of Proplan CMF 3.0 showed the best in the upper lip region(0.74±0.27mm),followed by the lower lip region(0.95±0.49mm),and the relatively large errors were left parnasal(2.52±3.45mm),right parnasal(1.38±0.96mm)and chin(1.23±0.52mm).The error in upper lip height(P<0.05)was significantly different between predicted and actual postoperative soft tissue.The three-dimensional movement of the maxilla was not statistically correlated with the prediction accuracy of most areas of the face,except for the sagittal movement of the maxillary and the left parnasal area(P<0.05).The horizontal movement of maxilla was correlated with the prediction error of upper lip height and width(P<0.05).(4)For female volunteer,the frequency of choosing GALL+2mm group as the best facial attraction was the highest among orthodontists and the laypeople(Orthodontists:11/30;Laypeople:9/30),followed by GALL group(Orthodontists:9/30;Laypeople:7/30).The frequency of choosing GALL+2mm group and GALL+4mm group as the best facial attractiveness was the highest in male group(11/30),while the frequency of choosing GALL group was the highest in female group(11/30),followed by GALL+2mm group(9/30).For male volunteer,the orthodontists chose GALL+2mm group as the best facial attractiveness with highest frequency(15/30),followed by GALL group(6/30),while the laypeople chose GALL group with the highest frequency(9/30),followed by GAll+4mm(7/30).The male group chose GALL+2mm group with the highest frequency(12/30),followed by GALL+4mm group(6/30),while the female group chose GALL group with the highest frequency(10/30),followed by GALL+2mm group(9/30).There was no statistically significant difference between orthodontist and laypeople and between genders in choosing the best facial attractiveness of male and female volunteers(P<0.05).Totally,regardless of male and female volunteers,the GALL+2mm group was rated as the best facial attraction with the highest frequency(male volunteer:21/60;female volunteer:20/60),followed by the GALL group(male volunteer:15/60;female volunteer:16/60)and the GALL+4mm group(male volunteer:11/60;female volunteer:14/60).Conclusions(1)There was a good correlation between forehead inclination and the distance between FA and superion in Guangxi population.A GALL model suitable for Guangxi population based on forehead inclination was constructed.(2)This model could be used as a reference for the preoperative planning of sagittal orientation of maxilla in orthognathic surgery.When upper incisors were positioned between GALL and GALL+4mm,acceptable facial effect could be obtained.It was suggested that both Chinese male and female orthognathic patients could consider GALL+2mm as a reference for sagittal localization of the maxilla. |
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