Upper Lip Asymmetry During Smiling: An Analysis Using Three-Dimensional Images

Is a symmetrical face really attractive?

Facial symmetry plays an important role in facial attractiveness and is one of the major criteria used to determine attractiveness in humans. In craniomaxillofacial surgery, facial symmetry is one of the main considerations. The aim of this study was to determine anthropometric measurements quantitatively and investigate the relationship between facial symmetry and attractiveness in a local Malay population. The study included 30 photographed Malay individuals and 100 photograph assessors, all aged between 18 and 26 years. The assessors indicated their preferences regarding the more attractive face on original and manipulated (symmetrical face) photographs. None of the photographed subjects had a perfectly symmetrical face (asymmetry index (AI) of 0%); 33.3% of the photographed subjects had an AI in the range of 1.6-2.0%. The majority of assessors chose the manipulated symmetrical face as the most attractive (manipulated photograph selected in 91.2% of cases). As facial symmetry is considered a critical factor in attractiveness, it is beneficial to consider balance and symmetry prior to facial reconstruction. The AI values found in this study may be useful as guidance to determine the normal minimum balance of facial symmetry. No AI values indicating perfect symmetry were observed for the unedited facial anthropometric measurements. However, the projection of a perfectly symmetrical face does influence the perception of facial attractiveness.

Effect of Orthognathic Surgery on Movement of the Cheilion

The cheilion (Ch), corner of the mouth, is the soft-tissue landmark where the upper and lower lips intersect. Orthognathic surgery can modify Ch position, which can affect facial esthetics. The aims were to evaluate Ch movements resulting from Le Fort I maxillary advancement with maxillary impaction or downgrafting, and with mandibular advancement or setback, and to investigate relationships between surgical movements and Ch movements. The 45 patients had undergone bilateral sagittal split ramus osteotomy with Le Fort I advancement surgery. They were divided into 4 groups according to surgical movement direction. Preoperative and postoperative photographs were calibrated. Standardized methods were used to identify and measure preoperative and postoperative Ch positions. Significant correlations were detected between extent of maxillary downgrafting and inferior movement of the Ch in group 1 (r=0.988, P=0.001) and group 3 (r=0.915, P=0.001). Also, significant correlations were detected between extent of mandibular advancement and anterior movement of the Ch in group 3 (r=0.561, P=0.046) and group 4 (r=0.661, P=0.005). The findings indicate that, in patients who undergo bilateral sagittal split ramus osteotomy/Le Fort I surgeries, mandibular advancement moves Ch anteriorly and maxillary downgrafting moves Ch inferiorly.

Post-surgery Rehabilitative Intervention Based on Imitation Therapy and Mouth-Hand Motor Synergies Provides Better Outcomes in Smile Production in Children and Adults With Long Term Facial Paralysis

Rehabilitation after free gracilis muscle transfer (smile surgery, SS) is crucial for a functional recovery of the smiling skill, mitigating social and psychological problems resulting from facial paralysis. We compared two post-SS rehabilitation treatments: the traditional based on teeth clenching exercises and the FIT-SAT (facial imitation and synergistic activity treatment). FIT-SAT, based on observation/imitation therapy and on hand-mouth motor synergies would facilitate neuronal activity in the facial motor cortex avoiding unwanted contractions of the jaw, implementing muscle control. We measured the smile symmetry on 30 patients, half of whom after SS underwent traditional treatment (control group, CG meanage = 20 ± 9) while the other half FIT-SAT (experimental group, EG meanage= 21 ± 14). We compared pictures of participants while holding two postures: maximum and gentle smile. The former corresponds to the maximal muscle contraction, whereas the latter is strongly linked to the control of muscle strength during voluntary movements. No differences were observed between the two groups in the maximum smile, whereas in the gentle smile the EG obtained a better symmetry than the CG. These results support the efficacy of FIT-SAT in modulating the smile allowing patients to adapt their smile to the various social contexts, aspect which is crucial during reciprocal interactions.

Landmark movement trajectory: A simple reference to understand the dominant muscle contraction in a dynamic smile expression

Insight into the roles of perioral muscles play in smiling is essential to the relevant esthetic and reconstructive treatment. This study analyzed specific landmarks' movement trajectories to understand the dominant muscle activity in smiling. Sixty volunteers (aged 18-45 years) were included, and standardized frontal view images were obtained by three-dimensional photogrammetry. Each image sequence frame was referenced and superimposed onto the neutral image. Six surface landmarks were digitized on each frame to form the entire movement trajectories from resting to maximal smile. The perioral muscles were divided into different groups according to the inserting position of muscular fibers and the contracting direction. The movement paths of landmarks were analyzed to find the major muscle groups involved. The dominant muscle groups throughout smiling were successfully identified by landmark trajectory analysis in all 60 volunteers. Zygomaticus major was the dominant force for the beginning of most smiles. Apart from the zygomaticus major, other perioral muscles played a dominant role throughout smile expression, including levator anguli oris, buccinator and risorius, depressor anguli oris, and the upward muscle group of the upper lip were all identified. Besides, a notable high percentage of smiles presented a mixed pattern, indicating the cooperation of several muscle groups during smiling. Landmark movement trajectory provides a simple reference to understand the dominant perioral muscles in smiling. It can help surgeons get more information for the dynamic treatment of smiles.

Evaluation of facial asymmetry by stereophotogrammetry in individuals with unilateral maxillary impacted canine

PURPOSE

The aim of this study is to compare the symmetry of the facial and dentoalveolar structures of patients with unilateral impacted maxillary canine teeth with a control group of individuals without impacted teeth using three-dimensional face scans.

METHODS

The study included 28 patients (10 females, 18 males) with unilateral impacted maxillary canine teeth and 28 patients (15 females, 13 males) without any impacted maxillary canine between 12 and 25 years of age. The 3dMDface™ (3dMD Inc., Atlanta, GA, USA) imaging system was used to obtain 3D face images. 3dMD Vultus® (3dMD Inc., Atlanta, GA, USA) software was used for the measurements.

RESULTS

According to the study findings, there were differences in linear measurements and volume measurements between the right and left sides of the face in patients with an impacted canine. However, these differences were not statistically significant. In patients with an impacted canine, surface differences between the right and left halves of the face were not found to be statistically different from the control group.

CONCLUSION

There was no difference in the amount of facial asymmetry between patients with unilateral maxillary impacted canine and patients with normal tooth alignment in the control group.

Recognition of the Asymmetrical Smile: A Comparison of Orthodontists, Oral and Maxillofacial Surgeons, and Laypersons

PURPOSE

Studies have shown that an asymmetrical smile is a relatively common problem. Yet, many patients are unaware of having this condition. Because having an asymmetrical smile can affect the final esthetic result of orthodontic therapy or orthognathic surgery, such patients need to be aware of the problem. The purpose of this study was to determine what amount of smile asymmetry is clinically evident to orthodontists, oral and maxillofacial surgeons (OMSs), and the lay public.

MATERIALS AND METHODS

A total of 56 OMSs, 117 orthodontists, and 123 laypersons participated in the study. They were asked to view a randomly arranged series of computer-generated male and female facial photographs with the smile symmetrical or altered in 0.5-mm increments from 1 to 4 mm and to indicate whether the person had an asymmetrical smile.

RESULTS

The OMSs and orthodontists were able to recognize relatively smaller amounts of asymmetry than the laypersons (2 mm vs 3 to 3.5 mm).

CONCLUSIONS

Although the clinicians performed better than the laypersons, both groups were able to recognize relatively small amounts of asymmetry. Because such a condition is generally not correctable and can affect the esthetic result, patients undergoing orthodontic therapy or orthognathic surgery need to be made aware of the situation before treatment.