Changes on Facial Profile in the Mixed Dentition, from Natural Growth and Induced by Balters' Bionator Appliance

Objective: The purpose of this study was to evaluate the facial profile changes induced by Balters' bionator appliance in Class II division 1 patients, at mixed dentition stage. Methods: The sample consisted of 28 pre-pubertal individuals at stages 1 and 2 of skeletal maturation (CVM), which were divided in two groups. The experimental group consisted of 14 individuals (7 boys and 7 girls, initial mean age of 8y12m) which were treated with Balters' bionator appliance for 14.7 months. The effects of treatment were compared to a control group of 14 subjects (7 boys and 7 girls, initial mean age of 8y5m) with Class II malocclusion, division 1, not orthodontically treated, which were followed up for 15.4 months. The statistical analysis was performed using Student's t test, at a significance level of 5%. Results: The results showed that the Balters' bionator appliance promoted a significant increase on the mentola-bial angle, in addition to demonstrating a tendency to reduce the facial skeletal convexity, to restrict the maxillary growth and to increase the nasolabial angle and the lower anterior facial height. Conclusion: It can be concluded that the Balters' bionator appliance improved the facial profile of children treated at mixed dentition stage. Changes on facial profile in the mixed dentition, from natural growth and induced by Balters' bionator appliance. » The authors report no commercial, proprietary or financial interest in the products or companies described in this article. INTRODUCTION Achieving an esthetically pleasing face is one of the main goals of orthodontic treatment, and since the beginning of orthodontics, great researchers such as King-sley,


INTRODUCTION
Achieving an esthetically pleasing face is one of the main goals of orthodontic treatment, and since the beginning of orthodontics, great researchers such as Kingsley, 16 Case 10 and Angle 3 emphasized the importance of the interrelation between esthetics and this specialty.However, to achieve this goal, it is necessary that the orthodontist deeply understand not only the biomechanical aspects related to tooth movement, but also the continuous changes that occur during facial growth and development of natural individuals. 27he introduction of cephalostat in dentistry 9 allowed the standardization of lateral teleradiography and allowed the accomplishment of more accurate dentoskeletal and facial proile assessments.Thus, combining the results of cephalometric analysis associated to clinical and subjective examination by each professional will enable the achievement of an ideal occlusion with functional stability and facial esthetic. 1,20,26espite the various cephalometric analysis proposed in literature, initially, little emphasis was given to the analysis of the sot tissue proile, due to the inadequate concept that changes on sot tissue would accurately follow the repositioning of subjacent skeletal and dental tissues. 19urrently, it is known that due to the large variability inherent to sot tissues -such as thickness and tonicity, especially of the lips -, they can mitigate or protrude the contours of the subjacent anatomical structures.
The concept of the ideal proile has been discussed in literature 8,14,23,25 and despite of accepting variations due to diferences among races, countries, culture and time, the straight or slightly convex proile is still synonymous of beauty.As the aspect of the facial proile in patients with Class II malocclusion, division 1, with mandibular retrusion is quite convex, one of the main goals of this treatment is to improve facial aesthetics, by reducing the proile convexity. 22lass II malocclusions are characterized by an imbalance between bone bases in the anteroposterior direction, which can result in maxillary basal protrusion, maxillary dentoalveolar protrusion, mandibular deiciency, mandibular dentoalveolar retrusion or a combination of these factors. 12,15This maxillomandibular discrepancy is present in a signiicant percentage of the population, 18,30 and is considered the most frequent in orthodontics practice.In Brazil, according to an epidemiological study conducted by Silva Filho et al, 29 with 2,016 children of 07-11 years-old, both genders, Class II malocclusion showed a prevalence of 42 %, being 27 % of dental origin and 15 % considered as skeletal Class II.Thus, it explains the large number of patients with this clinical feature who seek orthodontic clinics to address the esthetic and functional problems triggered by this malocclusion.
The treatment of Class II malocclusion, division 1, with mandibular deiciency in growing patients aims the mandibular advancement, to achieve better relations between bone bases and improve the convex facial proile.Among the functional orthodontic devices intended for this purpose, Balters' bionator is highlighted.It was developed by Wilhelm Balters in the 50's. 13He believed that improper posture of the tongue, which was placed in a retruded manner, would be responsible for a disturbance in cervical region, change in respiratory function, atypical deglutition and consequent impairment of mandibular growth. 5herefore, Balters designed a device to promote an anterior mandibular positioning, enabling the tongue to occupy a normal intraoral position and, also, lip competence. 19he few data reported in the literature about possible changes on facial proile of children with Class II malocclusion, division 1, due to mandibular retrusion treated with Balters' bionator, led us to evaluate the efect of treatment with this device.

PURPOSE
The aim of this study was to provide data to assess changes in the facial proile resulting from natural growth and induced by the use of Balters' bionator device in children, before the growth peak of the pre-pubertal period, more speciically in stages 1 and 2 of skeletal maturation, observed through the analysis of cervical vertebrae.

Material
The sample used in this study was obtained from two distinct populations: Brazilian and Canadian.Individuals were divided into two groups: the experimental group treated with Balters' bionator and a control group that received no orthodontic treatment.

Experimental group
The experimental group consisted of 14 patients treated with Balters' bionator, 7 males and 7 females.The inclusion criteria used were: Class II division 1 facial pattern, associated with mandibular retrusion; Class II, Changes on facial proile in the mixed dentition, from natural growth and induced by Balters' bionator appliance original article division 1, dental relation; permanent upper and lower central and lateral incisors erupted or erupting, no mandibular crowding, 5-7 mm overjet, mixed dentition and absence of cross-sectional problems.
All patients were treated with Balters' bionator, which was based on the original design proposed by Balters 5 and adapted by Ascher, 2 having the acrylic extension of the lower arch deeper than the original, and covering the incisal and cusps of the incisors and canines, respectively (Fig 1), so that the efect of inclination of the lower incisors was decreased.
The mandibular advancement was carried out in a unique way to obtain a cusp to cusp relation with incisors and, for patients whose overjet was more accentuated, the reference was the canine relation in Class I.For these cases, the treatment was carried out in two phases: The irst phase with canine relation in Class I, and the second phase with the incisors in a cusp to cusp relation.

Control group
The control group was selected from the documentation iles of the Burlington Growth Centre, located in the Department of Orthodontics, Faculty of Dentistry, University of Toronto, Canada.This sample consisted of 14 individuals, 7 males and 7 females, randomly selected from a group of 20 individuals.Selection criteria for this group were: Class II division 1 facial pattern, associated with mandibular retrusion; Class II division 1 dental relation; upper and lower central incisors erupted, mixed dentition and no previous orthodontic treatment.
These individuals were randomly paired with patients of the same gender from the experimental group, and selected the observation times that corresponded to the age, in complete years, of the respective pair.
The descriptive data about age and time of treatment for the experimental and control groups are shown in Tables 1 and 2, respectively.

Determination of skeletal maturation
The determination of skeletal age was verified through lateral teleradiographies, using the indicators of skeletal maturation of cervical vertebrae.The bone age determination was performed by the same operator and in a blind study, i.e., without identification of the patient evaluated, which reduces the subjectivity of this evaluation.Thus, the selected individuals were located in the maturation stages 1 and 2, i.e., before the growth peak of pre-pubertal period, according to Baccetti, Franchi, McNamara; 4 O'Reilly and Yanniello. 21

METHODS
For each individual, it were obtained two lateral cephalograms, called T 1 (beginning of treatment) and T 2 (end of treatment), for the experimental group; and T 1 (beginning of the observation period) and T 2 (end of the observation period) for the control group.
Although the radiographs had been obtained by different X-ray equipments, it was not performed a correction for image magnification.The difference of  magnification percentage between samples would be 0.16 %, which would not affect the comparison of the variables displayed in radiographs obtained by different X-ray devices.This difference in image magnification corresponds to a difference in magnification between X-rays of 0.0016 cm (0.016 mm).
All radiographs were traced by hand by the same operator, the cephalometric points were digitized on a Numonics AccuGrid tablet, and evaluated through Dentofacial Planner Plus 2.01 computer sotware for obtaining cephalometric measurements.

Obtaining cephalometric measurements
The cephalometric measures used in this study are shown in Table 3 and Figure 2.

Statistical analysis
To evaluate the data, the following statistical tests were performed: » Student's t-test for the equality of means of two independent populations: To examine the hypothesis that the mean of each measure in the control group did not difer from the mean of the experimental group at baseline (Table 4).» Student's t-test for the equality of means of two populations with independent samples: To examine the hypothesis that the changes observed in a cephalometric measure between times 1 and 2 do not differ, in terms of means, in the control group and the experimental group (Table 5).

RESULTS
To compare the changes that have occurred in the measurements, with and without treatment, it was necessary to eliminate the efect of the diference in time between the measurements performed in the experimental and control groups.For this reason, the changes in the measures were annualized (Table 5).The representation of the skeletal, dental and sot tissue changes is presented in Figure 3.

A B C
Changes on facial proile in the mixed dentition, from natural growth and induced by Balters' bionator appliance original article

DISCUSSION
The present study aimed to evaluate the changes in the facial profile of pre-pubertal individuals with Class II, division 1, mandibular retrusion, treated with Balters' bionator.In order to discriminate alterations induced by treatment from those deriving from natural growth, a control group was used from the Burlington Growth Centre, Toronto, Canada, which did not receive orthodontic treatment.
The knowledge about the growth process and natural craniofacial development is essential for distinguishing changes that truly occur by means of the established treatment, from those that occur regardless of the use of orthodontic appliances.However, one  of the major methodological diiculties in clinical research, in the ield of orthodontics, is the composition of a control group orthodontically untreated with similar characteristics to the experimental group. 11In the present study, it was used a control group from Canada, so it was possible to preserve the ethics, providing orthodontic treatment to all screened patients and eliminating a common bias for clinical work which is the absence of a control group.
In order to identify the actual stage of skeletal age, indicators of cervical vertebrae skeletal maturation were used based on the lateral teleradiographs, which are already part of the routine orthodontic records and therefore do not expose patients to additional X-rays, 24 as it happens when hand and wrist radiographs are requested.In this study, all individuals were located in stages 1 or 2 of maturation, i.e. before pubertal growth peak period. 4,21he assessment of equivalency between the experimental and control groups on measures targeted at baseline (Table 4) showed great cephalometric similarities before treatment between groups, since only 2 of the 11 variables were statistically different.
Finally, it will be discussed the changes on the facial profile that occurred due to the functional orthopedic treatment (experimental group) and without interference from any device (control group).

Effects of treatment
Ater the trial period of one year, it was observed that the supplementary angle to skeletal convexity (Convex) showed a nonsigniicant reduction of 0.9 o per year in the experimental group (Fig 3), while the control group did not change (0.0 o per year), i.e.Balters' bionator provided a tendency towards improvement of facial convexity.These indings are in agreement with Melo 19 whose studies about the changes on skeletal angle of convexity (NAPg) showed an increase of 2.52 o per year in children treated with bionator.
Considering that this angle is strongly influenced by the dislocation of the jaw bones during craniofacial growth and development, the behavior of anteroposterior jaw relative to the cranial base (SNA) was evaluated.It was identified that there was a tendency towards restriction of maxillary growth, known as extraoral effect, in the treated group (-0.6 o per year), while the control group showed an increase of 0.4 o per year (Fig 3).These data confirm the findings of Brandão 7 who verified the decrease of SNA in patients treated with bionator.As for the jaw, the SNB angle showed no statistically significant change.
The balance in the relation between the upper lip and the nose is quite evident by the nasolabial angle, which is often associated with the characterization of facial esthetics.In this experiment, there was an increase of 4.3 o per year in the experimental group and 1.6 o per year in the control group (Fig 3).The data shows that there was a tendency for this angle to become more opened in the group receiving treatment and are in agreement with the findings of Silva and Dominguez-Rodriguez, 28 who observed an increase of 9.83 o per year on a sample treated with bionator.
A determinant factor in the nasolabial angle is the postural position of the upper lip, which was assessed by checking the inclination of the upper incisor (U1PP).In the treated group, it was found a decrease of 4.5 o per year, highlighting the tendency towards vertical of maxillary incisors, whereas in the control group this decrease occurred on a much smaller scale (-0.6 o per year).As for the lower incisors, they tended to proclination, with a not statistically signiicant slight increase of 1.5 mm per year in group 1 and 0.9 mm per year in group 2 (Fig 1).We also assessed the interincisal angle (U1L1), which conirmed these aforementioned indings, with an increase of 3.0° per year in the group receiving treatment and a slight increase of 0.2°per year in the untreated group.Despite of lower incisors proclination being an undesired side efect of this treatment, this may contribute to postural correction of the lower lip. 19ssessing the behavior of the supplementary angle to mentolabial (ML), it was observed a statistically signiicant decrease (p< 0.05) of 0.8 mm per year for the treated group, whereas there was a tendency to an increase of 0.1 mm per year in the control group (Fig 3).This means that there was a signiicant improvement in the mentolabial angle for the treated group.These results are in agreement with the study of Silva and Dominguez-Rodriguez, 28 who observed an increase of 6.85° in patients treated with bionator for 18 months.According to Blanchette et al, 6 the mentum/labial sulcus of Class II children, with horizontal growth pattern and not submitted to orthodontic or orthopedic treatment, deepens naturally, which can be explained by the lower lip retracted and positioned between upper and lower incisors.
Evaluating the performance of the variable LAFH, there was a non-significant increase in the treated group of 1.4 mm per year, while in the control group this increase occurred in a lower manner (0.7 mm per year), which means that there was a trend to increased lower anterior facial height, a fact also confirmed by Melo, 19 who observed an increase in skeletal lower facial third of 1.37 mm per year in children treated with bionator.
Adding up the nose to the facial proile analysis, it was observed that the position of the upper lip to the line E (UL_E) showed a negative change of 0.8 mm per year (treatment group), while the control group did not show any alteration (0.0 mm per year).Then, there was a tendency to retrusion of the upper lip, a fact conirmed by Lange et al 17 who demonstrated the existence of an upper lip retrusion of 1.0 mm per year in patients treated with Balters' bionator.Regarding the lower lip (LL_E), there was a slight tendency to protrusion of the lower lip in both groups, being higher in the group that received no treatment (0.5 mm/year).
The statistical analysis at a signiicance level of 5% could not detect diferences among most of the studied measures, except for the ML measure.It is noteworthy that, ater a certain type of treatment, it is possible to ind clinically detectable changes, but statistically insigniicant, due to some factors such as the high variability of middle and/or high standard deviation, that may interfere on the efectiveness of the test used to identify these diferences.

CONCLUSION
Considering the present study, it can be concluded that the effects produced by Balters' bionator on facial profile of children treated in the mixed dentition stage were: » Increase of mentolabial angle.» Tendency to decreased skeletal facial convexity.» Tendency to maxillary growth restriction.» Tendency to increased nasolabial angle.» Tendency to verticalization of the upper incisors.» Tendency to proclination of the lower incisors.» Tendency to retrusion of the upper lip.» Tendency to increased anterior facial height.

Table 1 -
Descriptive data of patients' ages in experimental and control groups, according to gender and treatment stage.

Table 2 -
Descriptive data of treatment period, in months, of the patients in experimental and control groups, according to gender.
Figure 1 -Side and front view of Balters' bionator.

Table 4 -
Means and standard deviations of measures at baseline for each group, Levene's test for comparison of variances and Student's t-test to compare the means of the two groups.

Table 5 -
Means and standard deviations of annualized changes of measures for each group, Levene's test results for equality of variances and Student's t-test for equality of mean changes.