Changes in smile morphometric indices following maxillary advancement and mandibular setback surgery in skeletal Class III patients

Objectives: The aim of this study was to evaluate the changes in smile morphometric indices following maxillary advancement and mandibular setback surgery in patients with skeletal class III malocclusion. Materials and Methods: Smile morphometric indices were measured on frontal rest and smile photographs of 15 female patients with skeletal Class III malocclusions before and three months after maxillary advancement and mandibular setback surgery. Preand post-surgery measurements were compared. Results: The amount of left and right commissural height, philtrum height, and maximum upper incisor show at rest did not change significantly three months after surgery (p>0.05). The amount of maximum upper and lower incisor show, interlabial gap, smile width and index, buccal corridor ratio, gingival display, and smile arc on the frontal smile photographs didn’t showstatistically significant difference before and after surgery (P>0.05). Conclusion: Orthognathic surgery in patients with skeletal Class III malocclusion had no significant effect on rest and smile parameters from the frontal view.


Introduction:
2][3] Smile esthetics is of prime importance; not only because of its contribution to the overall attractiveness but also for its role in improving self-concept and emotional well-being. 4Individuals with dentofacial deformities and malocclusion usually have an unpleasant smile which potentially affects their social interactions. 5herefore, it is reasonable that orthodontic treatment and orthognathic surgery can lead to improved selfconcept and decreased anxiety.Skeletal Class III malocclusions can result in dysfunction and esthetic deformities with consequent psychological problems. 6To resolve these challenges, orthognathic surgical procedures are used to improve function and esthetics.8][9] Therefore, it is important for orthodontists to be aware of changes in orofacial soft tissue and subsequently in smile esthetics following orthognathic surgery.][12][13] Tostandardize smile photographs, it has been suggested taking photographs in natural head position 14,15 or using a cephalostat.[ 16Generally, the smile examination in orthodontic treatment involves a posed smile that is repeatable and reproducible.17, 18 The aim of our study was to evaluate changes in smile morphometric indices following maxillary advancement and mandibular setback surgery in patients with skeletal ClassIII malocclusions.

Materials and Methods:
Fifteen female patients with skeletal Class III malocclusions (maximum reverse overjet: 10 mm) who were candidates of maxillary advancement and mandibular set back surgery participated in this study.Patients who required impaction or downgrafting of the maxilla were excluded from the study.(n0.89978).Frontal rest and frontal posed smile photographs were taken from each patient before and three months after bilateral sagittal split osteotomy (BSSO) for mandibular setback and Lefort I maxillary advancement.The photographs were taken by digital camera (Nikon d5500, Tokyo,Japan) in natural head positionThe mean amount of maxillary advancement was 4 mm (range: 3-5 mm) and the mean amount of mandibular setback was 7 mm (range:4-9 mm).Preand post-surgical photographs were transferred to the smile analyzer software (Manufacture and country).[19] (Figure1) To determine the magnification of images, the upper central incisor width was measured on the patient's dentition by a digital caliper (Manufacture and country)(park tool co®, USA) and it was compared with the width of upper central incisor on images.
The following indices were measured on the frontal rest photographs (Figure 2): the maximum upper incisor show, philtrum height, left commissural height, and right commissural height.The following indices were measured on the frontal pose smile photographs (Figures 3,4): the maximum upper incisor show, lower incisor show, gingival display of upper central incisors, interlabial gap, the width of the smile 20 , smile index (which is the ratio of the smile width to the interlabial gap) 20 , the distance between inner commissures, the visible width of the upper arch dentition, buccal corridor ratio 21 , smile arc (consonant or non-consonant), and the last visible tooth of the upper arch 21 .Data were analyzed using the paired t-test, Wilcoxon signed ranks and the McNemar test (α=0.05)via SPSS16 software.(SPSSInc., Chicago, IL, USA) Ehtical clearance: The research project was approved by the research ethics committee of the Mashhad University of Medical Scien, Iran.

Rest morphometric indices before and after surgery
As in shown in Table I, the amount of maximum upper incisor show, left and right commissural height, and the philtrum height at rest did not change significantly three months after surgery (P>0.05).However, all indices, except for the maximum upper incisor show, increased after surgery.(Table I The last visible maxillary tooth in most patients was the second premolar pre-and post-surgery.To determine intra-examiner and inter-examiner reliability, five patients were randomly selected and morphometric indices were re-evaluated.Strong intra-examiner and inter-examiner agreement was observed on all variables.(P<0.001,Kappa coefficient 0.82-0.93;P<0.001, Kappa coefficient 0.84-0.95respectively.)Discussion A main expectation of patients from orthodontic treatment is a beautiful appearance, which undoubtedly includes an esthetic smile.In skeletal Class III patients undergoing orthognathic surgery, major changes of soft tissue arise from the surgery, even if pre-surgical orthodontics have been performed.Evaluation of the impact of different orthodontic and surgical orthognathic procedures on the frontal view of the face is important since people see themselves in the mirror from this view.
Studies have shown higher social abilities and higher intelligence attributed to people with a pleasing smile. 22,23 [26][27][28] In most of them, soft tissue changes were evaluated on lateral cephalograms or laser scans.Lateral cephalograms are not the best imaging technique to evaluate soft tissues and super imposition may cause error in identification of anatomic landmarks. 28oreover, the lateral cephalogram requires radiation, while photographs need no radiation and are easy to take and repeatable.Claman et al. reported that an identical lens focal distance, a fixed camera position, and a constant distance from the camera to the object are required for standardized photography. 29In the current study, the camera was fixed and the distance between the lens and the subject was maintained at 2 m.Facial attractiveness and a beautiful smile are closely related together. 20A smile is considered more As shown in Table III, the smile arc of six out of eight patients (75%) with non-consonant smile arcs converted to consonant smile arcs and the smile arc of six patients out of seven with consonant smile arcs, remained consonant after orthognathic surgery.
The result of the McNemar test showed that there was no significant difference between the smile arc on the frontal smile photographs before and after surgery (P=0.125).showed that in the smiles of Class III patients in the frontal view, both the upper and lower lips moved to the inferior position after mandibular setback.They concluded soft tissue morphology shows a significant improvement after orthognathic surgery in Class III patients. 33] In our study, although the maximum upper incisor show increased and the maximum lower incisor show, gingival display and interlabial gap decreased after surgery on frontal view, these differences were not statistically significant.In addition, on frontal rest photographs the differences between measurements before and after surgery were not significant.In our study, the buccal corridor was reduced after surgery; however, this reduction was not statistically significant.Smile width and smile index were not significantly different pre-and post-surgery.
Our results show that orthognathic surgery improved the form of smile arc as the percentage of consonant smile increased and the percentage of unconsonant smile arc decreased after surgery.Limitations: Maybe our small sample size caused these insignificant differences and it would be easier to interpret the results if we only chose patients undergoing setback surgery or maxillary advancement not both at the same time.

Recommendations:
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Table 1 : Rest morphometric indices before and after surgery
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Table 3 : Distribution of consonantandnon-consonantsmile arc before and after surgery
An obvious issue that should be noted is upper incisor show during smiling.Islam et al.
measurement of smile morphometric indices could perform in other orthognathic surgeries and with greater sample size and at least six month after surgery.. Conclusion: Maxillary advancement and mandibular setback surgery in patients with skeletal Class III malocclusion has no significant effect on rest and smile parameters from the frontal view.Conflict of interest: No conflict of interest Acknowledgement: We acknowledge and thank vice chancellor for research of Mashhad University of Medical Sciences.Author's Contributions: Data gathering and idea owner of this study: FF and FH Study design: RR Data gathering: MK Data analysis and consultation: TV Writing and submitting manuscript: HS