Abdallah S Nouh¹*, HM Abdel Majeed² and Essam Mohamed Nassef Selim²

¹Nuclear and Radiological Regulatory Authority, (NRRA), Nasr City, Cairo, Egypt
²Department of Orthodontics, Faculty of Oral and Dental Medicine, Future University, Cairo, Egypt

*Corresponding Author: Abdallah S Nouh, Atomic Energy Authority, Nuclear and Radiological Regulatory Authority, (NRRA), Nasr City, Cairo, Egypt.

Received: June 14, 2021; Published: June 29, 2021

Abstract

Introduction: Smile is a significant facial expression that affects the apparent facial attractiveness of a person and is used as an efficient mean for societal communication. This study is to evaluate the smile parameter variations between Class I and Class III male and female subjects. It invests the gender-related changes in the soft tissue for orthodontic diagnostic and proper treatment plans to reach the maximum patient satisfaction.

Materials and Methods: This study was carried out on 60 male and female adults patients aged between 18 and 30 years before orthodontic treatment. Two frontal digital photographs were taken for each subject, one at rest and the other in the posed smile position. Photographs were uploaded on Photoshop software for standardization and then uploaded on the Digital Smile Design software (DSD) where the actual incisogingival height of the central incisor was used for automatic calibration.

Results: The maxillary incisor display was statistically significantly greater for skeletal Class I subjects for both female and male compared to Class III. On the other hand, the percentage of non-consonant and flat smile arcs for skeletal Class III was found to be significantly higher than those in Class I subjects. Skeletal Class III subjects show significantly longer chin height, shorter upper lip length, shorter lower facial height, and less inter-commissural distance than Class I subjects.

Conclusion: Class III for both female and male subjects tended to have wider smile widths, less gingival display, longer chin heights, shorter lower vertical dimensions and a higher percentage of non-consonant and flat smile arcs than normal Class I subjects which should be taken into consideration in planning and designing the mechanics during comprehensive orthodontic treatment of these subjects.

Keywords: Class III; Class I; Gender; Esthetics; Smile

Introduction

  Smile schemes a diversity of positive feeling such as pleasures, support, and humor. An esthetical pleasant smile can enhance the self-confidence in societal conditions. Thus, it may not be amazing that a major reason that younger children and their parents look for orthodontic concern is to decrease banter [1]. There have been huge discussions regarding the significance of the smile with respect to the dentofacial features, the community and psychological benefits of enhancing smile esthetics [2].

  Esthetics plays a significant function in mitigating orthodontic treatment during childhood and adulthood [3]. Facial look is an essential factor in the insight of facial aesthetics, and the attractiveness of the face influences the perception of the smile character. In this situation, facial look should be taken into consideration in the orthodontic treatment plans. Additionally, the need to have a beauty, young and healthy look increases in culture, which allows esthetic consideration to be more significant in treatment planning. Therefore, smile esthetics became the main spotlight of patients searching orthodontic treatment [4].

  Several authors [5-7] conducted a study on the effect of maxillary incisors, lower lip, and gingival display relationship on smile attractiveness in female and male adults. They illustrated that the esthetic smile needs the interactions of different factors. Improving these factors is essential for orthodontists as smile attractiveness is the factor that many patients use to evaluate the achievement of orthodontic treatment. Thus, the complex relations among smile components associated with occlusal functions must be considered to get ideal useful and esthetic result. Lima., et al. [8] and Pithon., et al. [9] studied the influence of facial pattern in smile attractiveness for both female and male adults. They investigated that the conception of an ideal smile depends on tooth morphology, color, relative relations between teeth, lips, and gingival. Godinho., et al. [10] studied the role of facial parameters to the attractiveness of the smiling face in male and female patients. They found that the malocclusions affect the insight of attractiveness, intelligence, personality, and behaviors. Olsen and Inglehart [11] showed that persons with a regular occlusion are more attractive, intelligent, pleasant and extroverted; anterior crossbites cause negative insights, and people with numerous diastemas seem as the least reliable and pleasant. Another study of the influence of teeth arrangement on personality investigated that people with perfect smile are elegant and more suitable for jobs [12].

  Since patients became more care about the esthetics of their smile, orthodontists have to be interested in the soft tissue structure. It would be careful to assess the components of a smile prior to treatment to decide the needed action and to be in touch with the patient and parents [13,14].

Aim of the Study

  The aim of the present study is to assess the smile parameter variations among Class I and Class III male and female subjects, investigating the gender-related changes in the soft tissue for orthodontic diagnostic and proper treatment plans to meet the smile requirements for each gender.

Materials and Methods

  The current study was performed on 60 skeletal Class III and Class I male and female subjects with average vertical facial patterns selected from the Orthodontic Department, Faculty of Oral and Dental Medicine, Future University, Egypt. In a previous study by Kakadiya., et al. [15] the response within skeletal Class I and III groups was normally distributed true difference between the study groups was 1.42.

  Sample size calculation indicated that for a study with a power of 80% and an α error of 0.05, the lowest predictable sample size was 9 cases per group for a total of 18 cases. 60 male and female adults were included in the present study, according to the skeletal discrepancy whether mandibular excess or maxillary deficiency, divided into two groups which included 30 for each group. Subjects included in the study had an average age of 18 ‑ 30 years in order to minimize the effects of growth on facial appearance as reported by Leonardi., et al. [16] whereas those with congenitally missing, malformed or extracted teeth, having fixed bridges or crowns visible on smiling, extreme dental attrition, lip irregularity or history of lip surgery and facial asymmetries were excluded from the study. Two frontal photographs at rest and subjects’ commissure‑to‑commissure posed smile were taken by a Canon G11 camera set on a tripod from a fixed distance of 1.5m where the camera was focused on the mouth showing from the nose to the chin. The camera lens was adjusted to be parallel to the floor by adjusting the mounthead of the tripod guided by the leveling indicator that is built in the tripod. Photographs were taken for each patient in the natural head position. The head was held in an upright posture and eyes were focused on a point in the distance at eye level such that the visual axis was horizontal. For measuring smile variables the DSD software program was used. Standardization was mandatory to avoid any magnification errors where the incisogingival height of the right and left maxillary central incisors, lateral incisor and the canine were clinically measured (actual height) for each case using a vernier caliper to the nearest 0.1 mm found to be the same (Figure 1 and 2). Photographs were uploaded on Photoshop software for standardization and a reading for the incisogingival height of the right maxillary central incisor was done where a ratio of 7:5, as reported by Nouh AS., et al. [17] provides the most accurate image guided by the actual clinical height of the central incisor. The new standardized photos were uploaded on the digital smile system (DSD) software to be calibrated to measure all linear variables in to the nearest 0.1 mm. The actual incisogingival height in millimeters was used for automatic calibration by the digital smile system DSS where twelve smile components were evaluated at rest and on smiling. These smile components are defined in table 1.

Figure 1: Incisogingival height of the maxillary incisors.

Figure 2: Measuring incisor height using digital smile design (DSD).

Table 1: Brief definition of the studied smile characteristics.

  Numerical data were illustrated for normality by checking the distribution of data and through tests of normality (Kolmogorov-Smirnov and Shapiro-Wilk tests). All data illustrated normal (parametric) distribution excluding the gingival display which showed nonnormal (nonparametric) distribution. Data are presented as means, standard deviation (SD), mean difference and 95% confidence interval (95% CI) for the difference values. For parametric data, Student’s t test was used to compare between the two Classes. For nonparametric data, Mann-Whitney U test was used to compare between men of both Classes. The frequencies, percentages (%) and results of Fisher’s exact test for comparison between smile arcs of Class I and Class III men on smiling are represented. The significance level was set at P ≤ 0.05. Statistical analysis was performed with IBM SPSS Statistics for Windows, version 23.0. Armonk, New York: IBM Corp.

Results

  All measurements were repeated for 10 frontal photographs by the main observer and another observer. There was good to very good inter-observer reliability (agreement) regarding all measurements of Class I cases with Cronbach’s alpha values ranging from 0.608 to 0.812. Similarly with Class III cases; there was good to very good inter-observer reliability (agreement) regarding all measurements with Cronbach’s alpha values ranging from 0.611 to 0.812 (Table 2).

Table 2: Results of Cronbach's alpha reliability coefficient and intra-class correlation coefficient (ICC) for inter-observer reliability.

  The resulting data of the measured components for both males and females at rest are given in table 3. In Class I subjects, the upper lip length, lower lip thickness and the lower facial height were found to be statistically insignificant for both genders.

Table 3: Mean, standard deviation (SD), 95% confidence interval (95% CI) and results of student’s test for comparison of soft tissue measurements between class I females and males at rest.
*: Significant at P ≤ 0.05.

  The lower lip length and intercommisure distance were significantly longer in females than males. On the other hand, males showed statistically significant longer chin heights than females.

  The comparison between smile components for both male and female adults on smiling is investigated in table 4 and 5. The results show that the maxillary incisor display, the buccal corridor, the gingival display and the smile width were all statistically significantly higher in females than males. No significant difference in smile arcs between both genders.

Table 4: Mean, standard deviation (SD), 95% confidence interval (95% CI), results of student’s test and Mann-Whitney U test for comparison of soft tissue measurements between class I females and males on smiling.
*: Significant at P ≤ 0.05, †: Mann-Whitney U test.

Table 5: Comparison of frequencies, percentages (%) and results of Fisher’s Exact test of smile arcs between Class I females and males.
*: Significant at P ≤ 0.05.

  The comparison between smile components for both male and female adults at rest is illustrated in table 6. In Class III subjects, the upper lip length, intercommissure width and the lower facial height were all found to be statistically significantly higher in males than females. The upper, lower lip thickness and chin height was found to be statistically insignificant.

Table 6: Mean, standard deviation (SD), 95% Confidence Interval (95% CI) and results of student’s test for comparison of soft tissue measurements between Class III females and males at rest.
*: Significant at P ≤ 0.05.

  The results of the measured components for both males and females on smiling are given in table 7 and 8. The maxillary incisor display and smile widths showed statistically significantly higher results in Class III females than class III males. While, the buccal corridor, gingival display and smile arcs showed no statistically significant difference among class III females and class III males.

Table 7: Mean, standard deviation (SD), 95% Confidence Interval (95% CI), results of student’s test and Mann-Whitney U test for comparison of soft tissue measurements between Class III females and males on smiling.
*: Significant at P ≤ 0.05, †: Mann-Whitney U test.

Table 8: Frequencies, percentages (%) and results of Fisher’s Exact test for comparison between smile arcs of Class III females and males.
*: Significant at P ≤ 0.05.

Discussion

  In this study, Class III females showed significantly shorter lower facial height, less intercommisure width and shorter upper lip length compared to Class I females. However, significantly wider smile width and less gingival display were seen for Class III females on smiling which could be due to the influence of the shorter lower facial height and the vertical position of the maxilla seen in Class III female subjects.

  Although the lower facial height was less in Class III females, the chin height was found to be significantly longer compared to Class I females which could be attributed to the morphological mandibular pattern of skeletal Class III subjects. On the other hand, insignificant difference was found for the buccal corridor, maxillary incisor display, and smile arc consonance between females of both skeletal groups.

  Females of both skeletal patterns showed greater maxillary incisor display and smile width than males. This was in agreement with Jeelani., et al. [18] who stated that maxillary incisor display was more significant in females than males. On the other hand, Class III males showed significantly upper lip length, inter-commissural distance than Class III females which was in accordance with Stephanie and Jonas [19]. On the other hand, it disagrees with Kakadiya., et al. [15] who reported that females had significantly wider intercommissure width than males.

  Class I females showed greater gingival display and longer lower lip length than Class I males which came in contrast to Tjan., et al. [20] and Peck., et al. [21] who stated that males had higher soft tissue values than females. The intercommissure width was significantly wider for Class I females compared to Class I male subjects which came in contrast to Sachdeva., et al. [22] who illustrated that the intercommisure width was significantly wider in males.

  The mean buccal corridor for Class I females was significantly larger than that for Class I males, which does not agree with the results of Sachdeva., et al. [22] who showed insignificant difference for buccal corridors between both genders. The chin height showed insignificant gender difference for skeletal Class III subjects. However, it was significantly longer for Class I males compared to Class I females which came in contrast to Farhad., et al. [23] who reported that chin height was more significant in females than males.

  The percentage of consonant smile arcs was insignificantly different between both males and females for both skeletal groups which were not in agreement with the studies described by Sabri., et al. [24] and Câmara [13] who proved that smile arcs were more consonant in females than males.

Conclusion

• At rest, the lower lip length and intercommisure distance were significantly longer in females of Class I than males. Additionally, males showed statistically significant longer chin heights than females. On the other hand, in Class III subjects, the upper lip length, intercommissure width and the lower facial height were all found to be statistically significantly higher in males than females.
• On smiling, in the maxillary incisor display, the buccal corridor, the gingival display and the smile width were all statistically significantly higher in females of Class I than males. On the other hand, the maxillary incisor display and smile widths showed statistically significantly higher results in Class III females than Class III males.

References

1. Toth EK., et al. “Relationships between soft tissues in a posed smile and vertical cephalometric skeletal measurements”. American Journal of Orthodontics and Dentofacial Orthopedics 150 (2016): 378-385.
2. Simões D., et al. “Does the vertical position of maxillary central incisors in men influence smile esthetics perception?” American Journal of Orthodontics and Dentofacial Orthopedics 156 (2019): 485-492.
3. Wedrychowska-Szulc B and Syryńska M. “Patient and parent motivation for orthodontic treatment-a questionnaire study”. European Journal of Orthodontics 32 (2010): 447-452.
4. Springer NC., et al. “Smile esthetics from the layperson's perspective”. American Journal of Orthodontics and Dentofacial Orthopedics 139 (2011): 91-101.
5. Tosun H and Kaya B. “Effect of maxillary incisors, lower lip, and gingival display relationship on smile attractiveness”. American Journal of Orthodontics and Dentofacial Orthopedics 157 (2020): 340-347.
6. Batwa W., et al. “Effect of occlusal plane on smile attractiveness”. The Angle Orthodontist 82 (2012): 218-223.
7. Sharma PK and Sharma P. “Dental smile esthetics: the assessment and creation of the ideal smile”. Seminars in Orthodontics 18 (2012): 193-201.
8. Lima AP., et al. “Influence of facial pattern in smile attractiveness regarding gingival exposure assessed by dentists and laypersons”. American Journal of Orthodontics and Dentofacial Orthopedics 155 (2019): 224-233.
9. Pithon MM., et al. “Perception of laypersons and dental professionals and students as regards the aesthetic impact of gingival plastic surgery”. European Journal of Orthodontics 36 (2014): 173-178.
10. Godinho J., et al. “Contribution of facial components to the attractiveness of the smiling face in male and female patients: A cross-sectional correlation study”. American Journal of Orthodontics and Dentofacial Orthopedics 157 (2020): 98-104.
11. Olsen JA and Inglehart MR. “Malocclusions and perceptions of attractiveness, intelligence, and personality, and behavioral intentions”. American Journal of Orthodontics and Dentofacial Orthopedics 140 (2011): 669-679.
12. Pithon MM., et al. “Do dental esthetics have any influence on finding a job?” American Journal of Orthodontics and Dentofacial Orthopedics 146 (2014): 423-429.
13. Câmara CA. “Aesthetics in Orthodontics: Six horizontal smile lines”. Dental Press Journal of Orthodontics 15 (2010): 118-131.
14. Ackerman MB and Ackerman JL. “Smile analysis and design in the digital era”. Journal of Clinical Orthodontics 36 (2002): 221-236.
15. Kakadiya J., et al. “An evaluation of smile in different malocclusion of local population–A pilot study”. IOSR Journal of Dental and Medical Sciences 14 (2015): 25-32.
16. Leonardi R., et al. “Soft tissue changes following the extraction of premolars in nongrowing patients with bimaxillary protrusion. A systematic review”. The Angle Orthodontist 80 (2010): 211-216.
17. Nouh AS., et al. “Evaluation of smile characteristics of skeletal Class III compared to skeletal Class I female adults”. Journal of Orthodontic Science (2021).
18. Jeelani W., et al. “Age and sex-related variations in facial soft tissue thickness in a sample of Pakistani children”. Australian Journal of Forensic Sciences 49 (2017): 45-58.
19. Stephanie D and Jonas CJr. “Incisor display during speech and smile: Age and gender correlations”. Angle Orthodontist 86 (2016): 631-637.
20. Tjan AH., et al. “Some esthetic factors in a smile”. Journal of Prosthetic Dentistry 51 (1984): 24-28.
21. Peck S., et al. “The gingival smile line”. The Angle Orthodontist 62 (1992): 91-100.
22. Sachdeva K., et al. “Esthetic and Smile Characteristics at Rest and during Smiling”. Journal of Indian Orthodontic Society: SAGE Journals 46 (2012): 17-25.
23. Farhad BN., et al. “Influence of chin height on perceived attractiveness in the orthognathic patient, layperson, and clinician”. Angle Orthodontist 82 (2012): 88-95.
24. Sabri R., et al. “Tooth transposition: a review and clinical considerations for treatment”. World Journal of Orthodontics 9 (2008): 303-318.

Citation

Citation: Abdallah S Nouh., et al. “Gender Differences in Smiling: Class III and Class I Malocclusions”. Acta Scientific Dental Sciences 5.7 (2021): 120-127.

Copyright

Copyright: © 2021 Abdallah S Nouh., et al.. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.