An evaluation and comparison of smile characteristics of female adults in high angle, medium angle and low angle skeletal types – An observational study

Introduction

In recent years, the soft tissue paradigm has reemerged in orthodontics, with an increased emphasis on the soft tissues surrounding the mouth in general and the smile in particular. Getting a gorgeous smile is always the primary goal of any cosmetic dentistry procedure. After all, the difference between an acceptable and pleasant esthetic outcome for a particular treatment is the attractiveness of the smile. ^[1]

Several studies showed smile features and their influence on attractiveness. It was found that the optimum smile was mainly by an upper lip that reaches the gingival margins, with an upward or straight curvature between the philtrum and commissures, an upper incisal line that was coincident with the border of the lower lip, small or no lateral negative space, a commissural line and frontal occlusal plane parallel to the pupillary line and dental and gingival components in harmony. ^[2]

To diagnose, plan and create a transdisciplinary, esthetically pleasing, and functional end smile new technologies ^[3], ^[4] and software ^[5], ^[6], ^[7] has been developed. Patients' contentment with their quality of life and self-esteem is largely influenced by their facial appearance and smile esthetics in particular. ^[8] The treatment's success is still largely determined by the final cosmetic outcome. For the best outcomes, dynamic dentofacial examination of the interaction between the lips, teeth and face should be documented. ^[9]

Smile design software is used to simulate the treatment outcome and can be a bridge of communication between the orthodontist and the patient. The software also helps in analyzing the proportions and esthetics of teeth, smile and face, and allows the feasibility of enhancing the certainty of concluding planned outcomes. ^[2]

According to the literature reviewed, no such study has evaluated the smile characteristics in high angle, medium angle and low angle cases to the best of our knowledge. Thus, this study was taken up to increase understanding of features of a smile in such cases and to help in diagnosis and treatment planning for maximum patient satisfaction.

Materials and Methods

The present study was done on patients registered with the Department of Orthodontics, Manubhai Patel Dental College, Hospital & O.R.I. and requiring fixed orthodontic treatment and fulfilling inclusion criteria.

Females having a full set of permanent dentition and not having received any previous orthodontic treatment were included in the study.

Females having congenitally missing, malformed, or extracted teeth, having fixed bridges or crowns visible on smiling, excessive dental attrition, lip irregularity or history of lip surgery, facial asymmetries and the patients who did not give consent were excluded from the study.

Standardization for Photographs

One frontal photograph at the females’ commissure‑to‑commissure posed smile was taken by a Canon D1500 camera set at a distance of 1.5 m where the camera was focusing on the mouth showing from the nose to the chin. The camera lens was adjusted to be parallel to the floor. The photograph was taken of each female in the natural head position.

For measuring smile variables the MeditLink software program was used. For standardization, to avoid any magnification errors where the inciso-gingival height of the right maxillary central incisor was clinically measured (actual height) for each case using a vernier caliper to the nearest 0.1 mm. Photographs were uploaded on Picasa 3 software for standardization and reading for the inciso-gingival height of the right maxillary central incisor was done where a ratio of 4:3 is found to provide the most accurate image-guided by the actual clinical height of the central incisor. In order to calibrate the new standardized pictures and measure all linear variables to the closest 0.1 mm, they were uploaded to the MeditLink program. The MedlitLink automatically calibrated the grin components based on the patient's real inciso-gingival height in millimeters when the female smiled.

The characteristics that were studied are ([Figure 1]) -

Upper lip length (distance between subnasale and stomion superius.)

Upper lip thickness (from upper lip line to labrale superioris)

Lower facial height (vertical distance between subnasale to soft tissue menton)

Lower lip thickness (distance between stomion to labrale inferius)

Lower lip length (vertical distance between stomion to sulcus inferius)

Chin height (distance from sulcus inferius to soft tissue gnathion)

Incisor display (amount of tooth exposure during smiling)

Buccal corridors (distance between distal most dentition and the commissure)

Gingival display (amount of gingival exposure during smiling)

smile width (Horizontal distance between the outer commissures of the lips on smiling)

Results

A total of 45 females were included in the study divided into 3 groups with 15 each. A descriptive analysis was done for all the groups to know mean and deviation among the parameters. ANOVA test was done for all the parameters for comparison among the groups.

[Table 1] shows the descriptive analysis among the high angle types. This table shows the mean of all the parameters for the high angle types.

[Table 2] shows the descriptive analysis among the medium angle types. This table shows the mean of all the parameters for medium angle types.

[Table 3] shows the descriptive analysis among the low angle types. This shows the mean of all the parameters for low angle types.

[Table 4] shows the results of ANOVA test among the types for upper lip length.

Here P value is 0.831522 which is more than 0.05. Hence, null hypothesis is accepted which suggests no difference angle-wise in upper lip length.

[Table 5] shows the results of ANOVA test among the types for upper lip thickness.

Here P value is 0.46364 which is more than 0.05. Hence, null hypothesis is accepted which suggests no difference angle-wise in upper lip thickness.

[Table 6] shows the results of ANOVA test among the types for lower facial height.

Here P value is 0.836234 which is more than 0.05. Hence, null hypothesis is accepted which suggests no difference angle-wise in lower facial height.

[Table 7] shows the results of ANOVA test among the types for lower lip thickness.

Here P value is 0.865775 which is more than 0.05. Hence, null hypothesis is accepted which suggests no difference angle-wise in lower lip thickness.

[Table 8] shows the results of ANOVA test among the types for lower lip length.

Here P value is 0.505242 which is more than 0.05. Hence, null hypothesis is accepted which suggests no difference angle-wise in lower lip length.

[Table 9] shows the results of ANOVA test among the types forchin height.

Here P value is 0.016198 which is more than 0.05. Hence, null hypothesis is rejected which suggests there is difference angle-wise in chin height.

[Table 10] shows the results of ANOVA test among the types for smile width.

Here P value is 0.061028 which is more than 0.05. Hence, null hypothesis is rejected which suggests there is difference angle-wise in smile width.

[Table 11] shows the results of ANOVA test among the types for incisor display.

Here P value is 0.459272 which is more than 0.05. Hence, null hypothesis is accepted which suggests no difference angle-wise in incisor display.

[Table 12] shows the results of ANOVA test among the types for buccal corridors.

Here P value is 0.205539 which is more than 0.05. Hence, null hypothesis is accepted which suggests no difference angle-wise in buccal corridors.

[Table 13] shows the results of ANOVA test among the types for gingival display.

Here P value is 0.000531 which is more than 0.05. Hence, null hypothesis is rejected which suggests there is difference angle-wise in gingival display.

Discussion

This study aimed to identify the smile characteristics of female adults with high angle, medium angle, and low angle skeletal types. Each female had a single full-face frontal photograph taken with a staged smile, which Ackerman et al. claim is the most repeatable smile.^[11]

The amount of maxillary gingival show is the primary aspect of the smile that affects esthetics, according to Mack ^[12] and Peck et al. ^[13] According to research by Hulsey ^[14] and Mackley, ^[15] an appealing smile requires the upper lip to be at the same height as the maxillary central incisors' gingival margin. Furthermore, 2.1 mm of gingival display was reported to be the optimal amount for smile esthetics by Ker et al. ^[16] The gingival display measured in this study for females with high angles was 2.26 mm, which was found to be significantly greater than the gingival displays observed for females with medium angles and low angles, which were 0.57 mm and 0.44 mm, respectively. According to Chiche and Pinault's research, ^[17] 2-3 mm of visible gingiva may be deemed esthetically acceptable, despite the fact that they noted that the ideal amount of gingiva was approximately 1 mm.

In this study, gingival display was seen to be 2.26 mm in high angle, 0.57 mm in medium angle and 0.44 mm in low angle types. According to Nouh, ^[2] the gingival display was seen to be 3.20 mm. Here, the P-value was 0.0005 showing a significant difference among the types. Thus, proving that females with high mandibular angle show more of a gingival display compared to medium and low-angle types.

In this study, upper lip length was seen to be around 16 mm in all three types of females. The P-value was seen 0.83 which was seen non-significant among the types. According to Nouh ^[2] the upper lip length was seen to be 19.72 mm; and in the study by Nabawi, ^[1] it was 23.94 mm. In this study, the values were less than in the previous studies.

In this study, upper lip thickness was seen to be 7.1 mm in high angle, 7.42 mm in medium angle and 6.70 mm in low angle types. Here, the P-value was 0.46 showing no significant difference among the types. According to Nouh ^[2] the upper lip thickness was seen to be 6.29 mm, similar to this study. Nabawi ^[1] found it to be 10.08 mm. According to Mcintyre et al. ^[18] it was around 14.56 mm which suggests patients have thicker lips. This difference may be due to the different ethnicity of the study populations.

In this study, lower facial height was seen to be 66.61 mm in high angle, 68.04 mm in medium angle and 68.39 mm in low angle types. Here, the P-value was 0.83 showing no significant difference among the types. According to Nouh ^[2] the lower facial height was seen to be 61.65 mm. Nabawi ^[1] suggested the lower facial height to be 75.41 mm in his study, which is quite high compare to this study.

In this study, lower lip length was seen to be 16.348 mm in high angle, 15.64 mm in medium angle and 16.58 mm in low angle types. Here, the P-value was 0.50 showing no significant difference among the types. According to Nouh ^[2] the lower lip length was seen to be 23.9 mm.

In this study, lower lip thickness was seen to be 9.53 mm in high angle, 9.76 mm in medium angle and 9.40 mm in low angle types. Here, the P-value was 0.86 showing no significant difference among the types. According to Nouh ^[2] the lower lip thickness was seen to be 16.20 mm. This shows that, in this study, the patients showed to have thin lips.

In this study, chin height was seen to be 34.84 mm in high angle, 27.28 mm in medium angle and 28.7 mm in low angle types. Here, the P-value was 0.01 showing a significant difference among the types. This means that females with a high mandibular angle have longer chin height compared to medium and low-angle females. According to Nouh ^[2] the chin height was seen to be 37.09 mm, which was seen to be similar to that in this study.

In this study, smile width was seen to be 63.88 mm in high angle, 63.99 mm in medium angle and 71.08 mm in low angle types. Here, the P-value was 0.061 showing a significant difference among the types. This signifies that the females with low mandibular angle have a wider smile compared to high and medium angle females. According to Nouh ^[2] the smile width was seen to be 68.68 mm. This was similar to the smile width of females with low mandibular angle in our study. Thus, it can also be said that most of the patients have a horizontal to average growth pattern. The findings of Grover et al. ^[19] and Malhotra et al. ^[20] for Class I females showed maximum smile width being 66 mm. But in the study by Nabawi ^[1] it was around 76.77 mm, which is greater than other studies.

In this study, incisor display was seen to be 10.11 mm in high angle, 9.41 mm in medium angle and 9.38 mm in low angle types. Here, the P-value was 0.49 showing no significant difference among the types. According to Nouh, ^[2] the incisor display was seen to be 9.67 mm.

In this study, buccal corridors were seen to be 7.95 mm in high angle, 7.29 mm in medium angle and 8.90 mm in low angle types. Here, the P-value was 0.20 showing no significant difference among the types. According to Nouh, ^[2] the buccal corridors was seen to be 8.99 mm. According to Nabawi,^[1] it was 7.87 mm, thus the results of this study are in accordance with the previous studies. But, Rashed and Heravi ^[21] pointed out that there were no differences in the buccal corridors among different malocclusion groups. Moreover, these results were similar to the results of McNamara et al.^[22] and Krishnan et al.^[23]

Conclusion

This concludes that;

Females with a high mandibular angle tend to have more gingival display when compared to the other two types. Even though it was within the normal limits.

Females with high mandibular angle were seen to have a longer chin when compared to the other two types.

Female with low mandibular angle tend to have broader smiles compared to the other types.

The other parameters showed similar results, thus there were no significant difference among these skeletal types.

Source of Funding

None.

Conflict of Interest

None.