Correlation between gender and soft tissue characteristics of face among south Indian population of various skeletal malocclusion

Every face is unique and this variation also exists between genders. This forms the basis of sexual dimorphism. The aim of this study was to determine the correlation between gender and soft tissue of face among the south Indian population. The study sample comprised 30 lateral cephalograms collected between the time period of June 2019 - March 2020, which were divided into 3 groups. FACAD software was used for the analysis of lateral cephalograms to obtain six variables, namely: glabella area (G-G 1 ), subnasal area (A-Sn), Upper lip thickness (J-Ls), Lower lip thickness (I-Li), Labiomental sulcus thickness (B-Sm), Chin area (Pg-Pg 1 ). The obtained results were tabulated and statistically analysed using SPSS software version 23. One-way ANOVA and post hoc tests were performed between the skeletal malocclusions. Independent t-test was done to compare the variables between the two genders. The obtained results show a mean increase in all the variables of Class II except Lower lip thickness, which was maximum in Class I skeletal malocclusion. The results of One-way ANOVA, however, was statistically insigni(cid:977)icant. Hence, soft tissue characteristics can provide vital information on sexual dimorphism and also aid in the diagnosis of various malocclusions in orthodontics.


INTRODUCTION
Face is the esthetic and appealing part of the body. The irst thing a person recalls from memory is the face of another person (Perović and Blažej, 2018). Variations in the skeleton can easily be re lected by variations in the soft tissue surrounding it, due to its proximity. Dentoskeletal structures and the facial soft tissue thickness together constitute the facial pro ile.
Skeletal malocclusions are the discrepancies of the skeletal structures of the face due to genetic, environmental conditions or both. It can be due to the prognathism of a speci ic jaw or retrognathism of the opposing jaw or a combination of both. Based on this combination, they can be classi ied as Class I, Class II and Class III (Ardani et al., 2018;Mahendran, 2017).
Apart from adding to the esthetic appeal to the face, the soft tissue also effectively compensates for the skeletal defects, hence masking it in minor discrepancies. The soft tissue is also affected by the position of the tooth and its inclinations. Lateral cephalogram is a supplemental aid that can be used to analyse hard and soft tissue structures 2dimensionally (Al-Jame et al., 2006;Al-Azemi et al., 2008). A well taken lateral cephalogram usually records both these structures adequately, enabling the examiner to visualize the soft tissue characteristics with ease.
There is a difference in the morphology of male and female hard and soft tissue structures. This is referred to as sexual dimorphism. Females are believed to retain most of their prepubertal traits, whereas male undergoes enormous changes in terms of soft tissue characteristics as well (Hsiao et al., 2010). Hence, the purpose of this study was to compare the correlation between gender and soft tissue characteristics of various skeletal malocclusions of the south Indian population.

MATERIALS AND METHODS
The retrospective study consisted of 30 lateral cephalograms, collected between the time period of June 2019 -March 2020. These lateral cephalograms were divided into 3 groups, namely, Group A -Class I skeletal pattern Group B -Class II skeletal pattern Group C -Class III skeletal pattern Each group contained 10 radiographs, pertaining to their skeletal relationship. The data was collected from the Saveetha Institute of Medical and Technical Sciences (SIMATS) university database. Ethical approval was obtained from the institutional review board. FACAD software was used for the analysis of the lateral cephalograms. Points were plotted using this software to obtain linear measurements. The plotted points were veri ied and approved by the other authors. The following variables were taken into consideration, Linear measurements of all the aforementioned variables were obtained. The obtained results were subjected to statistical analysis using SPSS software version 23. One way ANOVA, post hoc and Bonferroni tests were performed to compare the variables between malocclusion. Independent T-test was done between genders to compare the soft tissue characteristics of the face.

RESULTS AND DISCUSSION
The descriptive statistics showing the mean and standard deviation of the variables within the malocclusion is depicted in (Table 1). Class II skeletal group showed the maximum thickness of all the soft tissue variables, except Lower lip thickness (I-Li), which is shown to be thickest in Class I skeletal groups. Class III skeletal pattern exhibited the least thickness of soft tissue characteristics of the face.
The mean and standard deviation of variables between gender is shown in (Table 2). Males showed increased thickness of all the variables except soft tissue gonion and pogonion thickness, which were thicker in females.
The results for One way ANOVA is shown in (Table 3). When comparing the groups between each other, the results were insigni icant.
(Tables 4, 5 and 6) show the results for the independent t-test, which are statistically insigni icant.
Previously, our team had conducted numerous clinical trials (Samantha, 2017;Kamisetty, 2015) , in vitro studies (Krishnan et al., 2015;Rubika et al., 2015), Finite element studies (Sivamurthy and Sundari, 2016;Krishnan et al., 2018) and a couple of prospective studies (Kumar et al., 2011;Felicita et al., 2012); Over the past 5 years. Now we are focusing on this retrospective study, done with the data obtained from our vast database. The idea for this study stemmed from the current interest in our community on the soft tissue paradigm shift (Dinesh, 2013;Felicita, 2017a;Felicita and Felicita, 2018).
Orthodontic treatment has always been directed towards the treatment of the face, rather than the skeleton (Viswanath, 2015;Felicita, 2017b). Although skeletal tissues are also considered important, the inal outlook of the soft tissue dictates the success/failure of the treatment (Albarakati, 2011). This study was aimed at providing a standard for male and female soft tissue characteristics, as it will aid in the diagnosis and effective treatment planning (Vikram, 2017;Jain, 2014). The soft tissue in conjecture with the hard tissue norms are helpful in establishing ideal facial esthetics and occlusion (Kamak and Celikoglu, 2012).
The inding of our retrospective study shows that the thickness of glabella, subnasale, upper lip, labiomental sulcus and chin are maximum in Class II skeletal pattern, followed by Class I skeletal pattern. Lower lip thickness, however, is thickest in Class I skeletal pattern, followed by Class II skeletal pattern. Class III showed the least thickness of all the variables. This is in accordance to the results       (Perović and Blažej, 2018). When comparing genders, the thickness of gonion and pogonion is more in females compared to males. This is in agreement with the studies conducted in the north Indian population (Saxena et al., 2012). The results, when subjected to One way ANOVA and independent t tests to compare the variables among the other groups and between the gender, yielded statistically insigni icant results.
Radiographs can be a valuable aid in the diagnosis of malocclusion. It is easily accessible and can be transferred over the internet. OPGs and CBCT also aid in the ease of implant placements and planning for any sort of implants. They are vital in ruling out individual tooth anomalies as well that might hinder orthodontic tooth movement.
Lateral cephalograms have become a routine in the daily orthodontic practice. Many skeletal discrepancies are precisely diagnosed using lateral cephalometric analysis. The analysis of vertebrae and sella turcica dimensions have also been shown to have diagnostic relevance. Similarly, angular photogrammetric analysis has also been shown to produce reliable results in aiding the diagnosis of soft tissue deviations. This study could also be used as one such adjunct to the growing arsenal of diagnostic aids (Scribante, 2017).
Kamalpreet et al., in his study, has made use of MRI and CBCT to evaluate the soft tissue characteristics of the northeast Indian population (Kaur et al., 2017). Atashi et al. have also reported changes in the thickness of soft tissue characters in males and females (Atashi and Kachooei, 2008). They have cited these differences to be due to differences in their body mass index (BMI). Aggarwal et al., in his study, has recommended the use of the soft tissue characteristics and variations in orthodontic treatment planning as they seemed to have signi icant clinical implications (Aggarwal and Singla, 2016).
Soft tissue variations can be attributed to a variety of in luencing factors, out of which gender is one such cause. The role of hormones such as testosterone in men which facilitates collagen formation, causing thicker soft tissue and estrogen in women, which decreases collagen formation due to the activity of hyaluronic acid, causing a reduction in the soft tissue thickness, is noteworthy (Al-Mashhadany et al., 2017) . Furthermore, improving knowledge on the sexual dimorphism that exists between both the genders in terms of their soft tissue characteristics can aid one to formulate an effective treatment plan, that caters to the patient's optimum requirements and establish a standard protocol of treatment.

CONCLUSIONS
Within the limits of the study, it was concluded that establishment of a norm for soft tissue characteristics was the need of the hour as it can still provide vital clues in providing quality orthodontic therapy to the patients, by keeping the soft tissue structures ahead of the priority list.