En-face parameters change after orthodontic treatment of Class II malocclusion

Summary Introduction The aim was to evaluate the difference in en-face anthropometric facial parameters and proportions of patients with Class II malocclusion, before and after orthodontic treatment as well as changes in linear parameters and facial proportions and their deviation from ideal values. Material and method In this study, en-face photographs before and after the treatment of 50 Class II malocclusion patients were used. Patients were divided in two groups; first group comprised 25 patients treated with multibracket appliance with extractions, and second group included 25 patients treated without extractions, using fixed functional Herbst and multibracket appliance. On each and every photo before and after the treatment facial points and lines were drawn, and linear parameters were determined, based on those markers. Results showed change in anthropometric parameters in both groups of patients. Statistically significant difference was found for parameters in the middle and lower facial third. Facial proportions changed after the treatment in both groups and they approached ideal values and golden proportion 1:1.618 in the lower facial third. Conclusion Patients with Class II, division 1 malocclusion, deviate from an ideal set of proportions, particularly in the lower facial third. After the orthodontic treatment, anthropometric parameters in the lower facial third were approaching ideal values.


INTRODUCTION
Facial esthetics evaluation has long history of development. In the last century, one of the first ways to measure facial parameters was actually the measurement of soft tissue profile characteristics. Soft tissue profile parameters were measured on cephalograms, while enface parameters were not taken into consideration due to poor visibility on anterior and posterior x-rays of head. These x-rays are indicated for skeletal, rather than dental structures analysis, in case of facial asymmetry. However, they were not the choice for soft tissue en-face parameter measurements. Although soft tissue analyses, known and described by authors in the last century, found their use in orthodontic diagnostics, they cannot be used for determining facial beauty in broader concept [1]. In the past, several soft tissue analyses were developed for measuring facial parameters [2,3]. These out-of-date analyses have not been combined with clinical assessment and none of them was used for important facial elements evaluation. Just recently, facial balance, beauty diagnosis and treatment planning are improved with combined clinical analysis and soft tissue cephalometric analysis [4].
At this moment, cephalometric three-dimensional soft tissue analysis, that would be useful for facial beauty guidelines determination, do not exist. Orthodontic treatment that corrects dentofacial anomaly (dental, skeletal, soft tissue anomaly) does not change facial appearance, therefore the answer lies in appearance comparison (be-fore and after the treatment) [5,6]. For that reason, it is necessary to measure en-face parameters on facial photographs before and after the orthodontic treatment, in terms of precise and highly justifiable facial perception change [7,8].
Facial harmony is associated with golden proportions. However, one cannot be assured that achieving golden proportions would change facial beauty perception. Several studies confirmed proportions influence in facial attractiveness; these results need to be taken with caution in terms of orthodontic treatment only [9,10,11].
The aim of this study was to determine the difference in en-face anthropometric facial parameters and proportions in patients with Class II malocclusion, before and after orthodontic treatment. Using en-face facial photographs, deviation from ideal proportions, especially in the lower facial third was determined.

MATERIALS AND METHODS
In this study en-face photographs of 50 Class II patients before and after the treatment were used. Patients were divided in two groups; first group of 25 patients was treated with extractions using multibracket appliance - Figure 1a, and second group, 25 patients were treated with the cast splint Herbst appliance followed by multibracket appliances treatment - Figure 1b. On each and every photo before and after the treatment facial points and lines were drawn, and linear parameters were determined, based on those markers. After determining facial markers and connecting them into appropriate lengths, proportions were measured. There are ideal proportions for each of parameters, so  Horizontal thirds of the face should be equal, forehead, nose and jaw thirds should be the same length on each photo individually, their actual length is not important, but only their relationship ( Figure 2).
Upper third of the jaw third, the distance between Subnasale and stomion should be 1/3 of the total length of the jaw third, ie. distance between Subnasale -Menton ( Figure 5).
The distance Menton -lateral nose and Lateral nose -Trichion should be 1 to 1.618 ( Figure 3).
If the width of the face (distance between two points lateral cheek (lchk)) is 1, the length of the face (distance between points Trichion and Menton) should be 1.618 ( Figure 5).

RESULTS
The results are presented in Tables 1 and 2. Parameter change after the orthodontic treatment in both groups is presented in Table 1. Statistically significant difference was found for parameters of the middle and lower third (N-subN and subN-Me), in both groups. Their ratio changed and in the first group it was 0.9 while in the second group it was 0.92.
The length parameters and their ratio are presented in Table 2. Parameters Me-Ln and Tr-Me showed significant change after the treatment (Sig < 0.01). When we compare the ratio of middle and lower third of the face, it can be noted that before the therapy it was 1.1 (length N-subN was 46.77mm, length of subN-Me was 52.20 mm), while after the treatment this ratio became 0.9 (length N-subN was 43.72 mm and the length of subN-Me was 48.44 mm).
In the first group of patients, the ratio of Me-Ln and Ln-Tr length before the treatment was 1:1.36 (length Me-Ln was 61.93mm and length Ln-Tr was 84.38mm) while after the treatment this ratio was 1:1.5 (length Me-Ln was 55.71mm and length Ln-Tr was 83.76mm). In the second group of patients, the ratio of these two parameters before the treatment was 1.45 (length Me-Ln was 48.72mm and length Ln-Tr was 70.72 mm). After the treatment this ratio changed at 1.62 (length Me-Ln was 48.57mm and length Ln-Tr was 78.77 mm).

DISCUSSION
Analysis of facial parameters and their comparison with standard-average values are necessary in different fields of medicine and dentistry that are able to change facial characteristics in different ways [12,13,14]. Some of the specialties like plastic surgery, maxillofacial surgery, orthodontics and prosthodontics are able to perform these kinds of changes. Assumingly, it is important to balance the outcome of the treatment with patient`s expectations, as well their family and friends. Individual beauty assessments and variations in broader opinion about beauty concept, which is highly dependent of modern trends and fashion, are subject of investigations of various authors. [15] Therefore, orthodontists and surgeons have to be united when it comes to objective clinical goals about patient's appearance improvement [16,17].
In our research en-face parameters were measured. They indicate facial symmetry and division of the face into various proportions and regions, and compatibility with the set of ideal proportions. As it was already mentioned, beauty is very individual; it lies in the eye of observer, and it is difficult to measure and compare it. Therefore, quantitative and numeric comparison between the two groups of patients was not done [18].  Upper, middle and lower facial third should be, in case of harmonically balanced face, approximately equal (ratio 1:1). Lower facial third is divided with line that goes through the point stomion, in upper and lower part, and their ratio should be 1:2 [19].
In the group of patients who had some teeth extracted, statistically significant difference for parameters of middle and lower third was found. As mentioned earlier ratio is more important than the actual numbers. Not taking into consideration values in millimeters but change in relation between parameters we can see slight increase in vertical dimension of lower facial third after finished orthodontic treatment. The reason and explanation can be found in changing the parameters of vertical growth, and increasing vertical dimension due to the application of Class II intermaxillary elastics. However, observing these values and comparing them with the set of ideal proportions, it is noticeable that the ratio between these proportions and their closeness to ideal values did not significantly change, so that difference cannot be described as facial attractiveness change. Nevertheless, the change is visible to clinicians and in the eye of observer. Shell et al. [20] came to the same conclusion when they compared ideal proportions in Class II patients treated with activator during growth, and after the period of active growth, with multibracket appliance with or without orthognatic surgery. They compared re- lation between ideal proportions and facial attractiveness perception and found that although orthodontic treatment changed facial appearance, it is debatable to what extent that change means achievement of ideal proportions [21].
In the group of patients treated without extractions comparing the parameters of the horizontal division of the face into equal thirds, statistically significant difference was found for the parameter Tr-N. As the upper third of the face significantly change, it is important to identify and interpret newly established relationship of face division into thirds and whether it affects patient's perception in accordance with possible approach to golden proportions. In this group of patients, similar findings about changes in relationship of the lower and middle thirds of face on one side and upper facial third on the other side were found. The original ratio was reduced from 1.1 to 0.92, which was explained as slight change in vertical dimension of the lower third of the face [22].
Ratio between linear parameters in ideal proportions should be, in numerical terms, 1:1.618. Linear parameter of Me-Ln and Ln-Tr before the treatment was 1:1.36, while after the treatment that relation was 1:1.5. The ideal ratio is 1:1.618, and after the treatment the ratio came closer to this value because the parameter Me-Ln in the lower facial third changed.
Even though the parameter Tr-Me (the length of the face) significantly changed after the orthodontic treatment, the ratio between facial length and width that should be close to golden ratio of 1 to 1.618 did not change much. This ratio between the facial length (Tr-Me) and width (lchk-lchk) before treatment was 1.47 and after the treatment it was 1.45. As these values talk more about the broader aspect of enface look and can be associated with the shape of the face, it is expected that this segment will not be much changed after the treatment.
In the group of facial length parameters defined by ideal proportions, in patients treated with fixed functional appliance without extraction, statistically significant difference was observed for the parameter Ln-Tr, which was in golden proportion with the parameter Me-Ln. These two parameters had ratio 1.45 before the treatment, while after the treatment this ratio changed to 1.62 that is ideal relationship between these two parameters. Therefore, in this group of patients ideal ratio was achieved between these two parameters, one of which is directly related to the outcome of orthodontic treatment, new position of chin and Menton (the lowest point on the chin). Our results are consistent with the research of Scolozzi et al. [23] who also reached ideal ratio after completing treatment for the same parameter in the lower third of the face.
Baker et al. [24] performed study about relation between ideal facial proportions and attractiveness perception after orthodontic and surgical treatment taking into consideration facial entities that influence facial beauty concept in general. They used a questionnaire and in results reported significant improvement of facial attractiveness after the treatment, although without strong connection with ideal values. They suggested this analysis to be used only as addition to cephalometric and anthropometric analysis.
Expectedly, Class II malocclusion treatment had limited influence on en-face facial parameters, and consequently achieving ideal values. However, significant changes occurred in the soft tissue profile, so that the measurement of these parameters on the profile photographs, as shown in many studies, is an indispensable supplement to complete analysis of facial soft tissue parameters [25].

CONCLUSION
After anthropometric measurement of linear parameters and proportions, it can be concluded that patients with Class II, division 1 malocclusion, deviate from an ideal set of proportions, particularly in the lower facial third. After the orthodontic treatment, these parameters were approaching the set of ideal values, in both groups of treated patients (with and without extractions).