Comparative Evaluation of a Combination of Facemask-Removable Appliance and Removable Appliance Alone for Antero-Posterior Expansion in 8 - 10-Year-Old Cl III Children with Maxillary Deficiency

AUTHORS

Majid Heidarpour 1 , Saeid Sadeghian 1 , Amir Siadat 2 , Sara Siadat 3 , * , Maryam Keimasi 2

1 Department of Orthodontic Treatment and Torabinejad Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran

2 Dental Student’s Research Center, School of Dentistry, University of Isfahan, Isfahan, Iran

3 Postgraduate Student, Department of Orthodontics, School of Dentistry, Isfahan Branch, Islamic Azad University, Isfahan, Iran

How to Cite: Heidarpour M, Sadeghian S, Siadat A, Siadat S, Keimasi M. Comparative Evaluation of a Combination of Facemask-Removable Appliance and Removable Appliance Alone for Antero-Posterior Expansion in 8 - 10-Year-Old Cl III Children with Maxillary Deficiency, Iran J Ortho. 2018 ; 13(1):e8677. doi: 10.5812/ijo.8677.

ARTICLE INFORMATION

Iranian Journal of Orthodontics: 13 (1); e8677
Published Online: July 19, 2017
Article Type: Original Article
Received: October 5, 2016
Revised: October 19, 2016
Accepted: June 4, 2017
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Abstract

Objectives: The aim of this study was to evaluate and compare the effects of concomitant use of a facemask and a removable appliance and a removable appliance alone for antero-posterior expansion in Cl III children with maxillary deficiency.

Methods: In this retrospective analytical study, 21 Cl III children aged 8 - 10 years were selected using the census sampling technique. The subjects were divided into two groups based on the treatment modality. In group A, the subjects received an antero-posterior-expanding removable appliance and in group B, they received the same removable appliance concomitant with a facemask. Pre- and post-therapeutic cephalograms were analyzed and changes and angles on both images were determined. Mann-Whitney U and Wilcoxon tests were used to compare the results of the two treatment modalities and before-after results respectively (α = 0.05).

Results: Wits appraisal, overjet, ANB, U1-SN, U1-PP and A-B difference increased in both groups after treatment (P < 0.05). In the removable appliance group, overbite, SNB and inter-incisal angle decreased (P < 0.05). In the facemask group, IMPA decreased significantly (P < 0.05). Comparison of the two treatment modalities showed that changes in SNA, ANB, overbite, IMPA, U1-SN, U1-PP and inter-incisal angle were significant between the two groups (P < 0.05).

Conclusions: Use of a removable appliance alone or in combination with a facemask resulted in the forward movement of point A and protrusion of upper incisors. The removable appliance increased the anterior facial height and decreased overbite. A combination of facemask-removable appliance did not result in the backward and downward rotation of the mandible.

Keywords

Facemask Cl III Removable Appliance Maxillary Deficiency Y-Plate

Copyright © 2017, Iranian Journal of Orthodontics. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited

1. Background

The prevalence of Cl III malocclusion is different in different ethnic groups, with reports indicating prevalence rates of 1% - 5% in Caucasians and 14% in Asian population (1-3). Based on previous studies, 75% of skeletal Cl III malocclusions are due to maxillary retrognathia or mandibular prognathism and the remaining 25% have dental reasons. In this context, some researchers believe maxillary retrognathia is the most common reason for Cl III malocclusion (4, 5).

Maxillary deficiency in the antero-posterior and vertical dimensions might have a role in Cl III malocclusion (6). Despite the lower prevalence of Angle Cl III malocclusion compared to Cl II and Cl I malocclusion, decision regarding to the treatment of such patients is a challenge for orthodontists (7). A facemask connected to a maxillary splint might move the maxilla forward by inducing growth at posterior sutures of the maxilla, on the condition that it is administered at a young age (7).

A large number of studies have been undertaken to evaluate the efficacy of facemasks in patients with maxillary deficiency. In this context, a systematic review in 2014 reported the efficacy of facemasks for the treatment of maxillary deficiency in the short term (8). In addition, a large number of studies have shown the efficacy of facemasks if they are used at an appropriate time. In such studies, facemasks have been used with different appliances, including rapid palatal expansion appliances (9-13), skeletal anchorage (14-17), labiolingual appliances (10) and removable appliances with or without a posterior bite plane (13, 18). The results of these studies have shown downward and backward rotation of the mandible, retroclination of mandibular incisors, forward maxillary growth and proclination of maxillary incisors. In addition, there have been improvements in the soft tissue profile.

In addition, removable appliances with anterior or posterior expansion screw (or both), alone or in combination with facemasks, have been used in a number of studies to correct the jaw relationships in patients with Cl III malocclusion; such studies have been case reports (19) or case series (20) with no control groups and no matching of appliances and treatment biomechanics.

Various studies have evaluated sagittal changes of the jaws due to rapid expansion of the palate. Haas (21) in 1961 described the forward movement of the maxilla during rapid expansion of the palate, reporting that such a phenomenon had a positive effect on the correction of the antero-posterior relationship of the jaws in Cl III patients with maxillary deficiency. Davis and Kronman (22), Wertz (23), Sarver and Johnston (24), Basciftci and Karaman (25) reported similar findings in subsequent years. However, da Silva Filho et al. (26) did not report forward movement of the maxilla during rapid expansion of the palate; rather, they reported backward and downward rotation of the mandible in such patients.

Therefore, use of a facemask for traction and ossification of the posterior maxilla is a routine technique and valid studies have confirmed its efficacy. On the other hand, in a number of studies the effect of rapid expansion of the palate has been reported on antero-posterior changes of the jaws. In this context, no studies to date have evaluated the sagittal effects of a removable appliance for the antero-posterior expansion with a uniform appliance design. On the other hand, no studies have evaluated the effects of combining a facemask with a Y-plate splint for exerting simultaneous skeletal effects on facial growth and dental effects for gaining space for eruption of teeth. Therefore, the aim of the present study was to evaluate and compare the combined use of facemask-removable appliance and a removable appliance alone for antero-posterior expansion in 8 - 10-year-old Cl III children with maxillary deficiency. The null hypothesis in the present study stated that ‘there are no significant differences between the results of these two treatment modalities’.

2. Methods

In the present retrospective analytical study, 21 children, aged 8 - 10 years, with Cl III malocclusion due to maxillary deficiency in association with reverse overjet less than 4 mm, were selected using the census technique. The subjects had been referred to two clinics of faculty of dentistry, Isfahan University of Medical Sciences and treated by two orthodontists for Cl III malocclusion. The subjects were assigned to two groups based on the treatment modality used. The subjects were all 8 - 10 years of age when the treatment was undertaken. Group A consisted of 5 boys and 4 girls with a mean age of 9 years and 2 months and the treatment duration was 7 months. The subjects in group B consisted of 5 boys and 7 girls with a mean age of 8 years and 4 months and the treatment duration was 8.5 months. In group A, a removable appliance alone had been prescribed, with a capacity to bring about antero-posterior expansion (Figure 1). In group B, in addition to the removable appliance mentioned for group A, a facemask had been prescribed (Figure 2). Before instituting treatment, the subjects had undergone a cephalometric examination. At the end of the treatment, after achieving an overjet of 1.5 mm and a favorable treatment outcome based on the judgment made by the clinician, the patient had undergone a cephalometric examination again. To carry out the radiographic examination, the overjet had been determined clinically by measuring the distance between the incisal edges of maxillary and mandibular incisors. Both before and after treatment cephalograms of the patients were analyzed and 21 parameters including SNA, SNB, ANB, Overjet, overbite, maxilla to cranium, mandible to cranium, Wits appraisal index, anterior facial height, anterior facial height/posterior facial height, Occlusal plane/SN, Go-Gn/SN, IMPA, U1-SN, U1-PP, Co-A, Co-Gn, Inter-Incisal angle, A-B difference, and ANS-Me, were determined and analyzed. To make a distinction between the total effects (dental and skeletal) and dental effects, manual superimposition was carried out. After elimination of names from the cephalograms and coding each cephalogram, the measurements were made. The operator was blinded to the codes. In order to evaluate the general effects, the initial and final tracings of each subject were superimposed on the Ba-Na line at point CC (CC = cranial center, the point at which the Ba-Na line meets the facial axis, i.e. the pterygoid-gnathion line) (Figure 3). Local superimposition was carried out on the palatal plane at point ANS for maxilla (Figure 4) and on the mandibular plane at Gn for the mandible (Figure 5) to evaluate the dental effects (6).

Anterior - Posterior Expansion Appliance: in This Appliance, Z Hooks Distal to Upper Canines Were Considered and 2 Screws Were Used in Y-Plate
Figure 1. Anterior - Posterior Expansion Appliance: in This Appliance, Z Hooks Distal to Upper Canines Were Considered and 2 Screws Were Used in Y-Plate
Facemask Used in the Second Group with the Y-Plate Shown in the Figure 1. Two ¼ Heavy Elastic Tractions with a Total Force of 700 gr Connected Y-Plate to Facemask
Figure 2. Facemask Used in the Second Group with the Y-Plate Shown in the Figure 1. Two ¼ Heavy Elastic Tractions with a Total Force of 700 gr Connected Y-Plate to Facemask
Total Superimposition on Ba-Na at CC: 1- Upper Incisor-T 2-Lower Incisor-T 3- Upper Molar-T 4- Lower Molar-T 5- Upper Incisor-SN 6- Lower Incisor-SN 7- Upper Molar-SN 8- Lower Molar-SN
Figure 3. Total Superimposition on Ba-Na at CC: 1- Upper Incisor-T 2-Lower Incisor-T 3- Upper Molar-T 4- Lower Molar-T 5- Upper Incisor-SN 6- Lower Incisor-SN 7- Upper Molar-SN 8- Lower Molar-SN
Local Superimposition on Palatal Plane at ANS: 9- Upper Incisor-T 10- Upper Molar-T 11- Upper Incisor-SN 12- Upper Molar-SN
Figure 4. Local Superimposition on Palatal Plane at ANS: 9- Upper Incisor-T 10- Upper Molar-T 11- Upper Incisor-SN 12- Upper Molar-SN
local Superimposition on Mandibular Plane at Gn: 13- Lower Incisor-T 14- Lower Molar-T 15- Lower Incisor-SN 15- Lower Molar-SN
Figure 5. local Superimposition on Mandibular Plane at Gn: 13- Lower Incisor-T 14- Lower Molar-T 15- Lower Incisor-SN 15- Lower Molar-SN

For each superimposition, the SN plane was considered the horizontal reference before treatment. The line perpendicular to SN at point T (the uppermost point on the anterior wall of cell turcica at its junction with sella tuberculum) was considered as the vertical reference plane. Vertical and horizontal orthodontic movements of upper and lower incisors and molars were evaluated relative to the references determined on initial cephalograms (Figures 3 - 5).

Data were analyzed with SPSS 22. Mann-Whiney U test was used to compare the results achieved from the treatment modalities. Wilcoxon signed-rank test was used to compare the pre- and post-therapeutic results at α = 0.05.

3. Results

3.1. The Removable Appliance Group

Evaluation of cephalometric findings in this group showed significant increases in overjet, ANB, A-B difference and Wits appraisal index (P < 0.05). In addition, there was a significant increase and decrease in the anterior facial height and overbite, respectively (P < 0.05). The SNB and SNA decreased and increased significantly, respectively (P < 0.05). Of all the dental indices, U1-SN and U1-PP increased significantly (P < 0.01). Furthermore, the dental index of inter-incisal angle decreased significantly (P < 0.05).

Evaluation of total superimposition in this group showed that upper incisor-T and lower molar-T increased and decreased significantly, respectively (P < 0.05). In the local superimposition of the maxilla only the upper incisor-T index exhibited a significant increase (P < 0.05). In the partial superimposition of the mandible, there were significant decreases in the lower incisor-SN, lower molar-SN and lower molar-T indices (P < 0.05).

3.2. The Facemask-Removable Appliance Group

In this group, increases in overjet, ANB, Wits appraisal, A-B difference and SNA were significant (P < 0.01). Furthermore, the maxilla-to-cranium and Co-A indices exhibited significant increases (P < 0.05). Of all the dental indices, IMPA decreased significantly (P < 0.01) and U1-SN and U1-PP increased significantly (P < 0.01). Evaluation of superimpositions carried out in this group showed that in total superimpositions, the maxillary molars and incisors were displaced significantly at both horizontal and vertical dimensions and increases in upper incisor-SN, upper incisor-T, upper molar-SN and upper molar-T were significant (P < 0.05). In addition, in total superimposition lower incisor-T and lower molar-SN exhibited significant decrease (P < 0.05) and increase (P < 0.01), respectively. In this group, in local superimpositions, the upper molar-SN and upper incisor-T exhibited significant increases but lower-incisor-SN exhibited a significant decrease (P < 0.05).

3.3. Comparison of the Facemask and Removable Appliance Groups

Comparison of these two groups showed that changes in the cephalometric indices of SNA and ANB were significant (P < 0.05); changes in SNA in the removable appliance and facemask groups were 1.00 and 3.12 degrees, respectively. ANB index had increased 2.16 and 3.25 degrees in the removable appliance and facemask groups, respectively.

Of all the vertical indices, the changes in overbite were significant between the two groups (P < 0.05); in this context, in the removable appliance group overbite had decreased 1.83 mm during treatment and in the facemask group it had increased 0.55 mm. Regarding to the dental indices of the degrees of upper incisors, the increases in U1-SN and U1-PP in the removable appliance group were 12.33° and 13.55°, respectively, with 6.08° and 6.87°, respectively, in the facemask group. In addition, the change in the IMPA angle was significant between the two groups (P < 0.05); in this context, in the removable appliance group, IMPA had decreased only 1.22° but it had decreased 7.37° in the facemask group. The inter-incisal angle in the removable appliance group exhibited a change of -11.27° but in the facemask group it changed -1.08°, with a significant difference between the two groups (P < 0.01).

Evaluation of the local superimposition of the maxilla showed that the change in the upper molar-T index between the two groups was significant (P < 0.05), i.e. in the removable appliance group this index decreased 1.33 mm and in the facemask group it increased 1.00 mm.

Table 1. Comparison of Cephalometric Indices Before and After Treatment in Two Evaluated Groupsa
Chephalometric FeaturesGroup A (Removable Plate)Group B (Facemask + Removable Plate)P Value for Comparison of Group A and B
BeforeAfterBeforeAfter
SNA, °81.33 ± 3.7782.22 ± 3.3477.20 ± 3.7680.33 ± 5.710.034*
SNB, °81.28 ± 5.2680.11 ± 4.0478.12 ± 4.1478 ± 6.460.862
Overjet, mm-2.78 ± 0.912.44 ± 0.87-2.36 ± 1.472.8 ± 1.040.972
Maxilla to cranium, mm-0.47 ± 2.270.90 ± 1.35-3.23 ± 2.63-1.1 ± 2.820.508
Mandible to cranium, mm-2.72 ± 3.91-1.47 ± 3.90-6.12 ± 3.90-6 ± 4.660.754
Co-A, mm75.35 ± 4.4177 ± 5.2470.45 ± 5.5473.22 ± 5.300.808
C0-Gn, mm99.98 ± 7.61101.75 ± 6.7094.75 ± 796.38 ± 8.050.464
Occusal plane / SN, °17.22 ± 3.9917.61 ± 3.3120.29 ± 6.2520.41 ± 5.660.754
ANB, °0.05 ± 2.422.11 ± 1.83-0.91 ± 1.632.33 ± 1.770.049*
SN/Go-Gn, °33.11 ± 5.7134.22 ± 5.1436.04 ± 5.8237.12 ± 5.740.702
Overbite, mm3.37 ± 1.681.54 ± 0.961.12 ± 3.271.67 ± 1.270.034*
Wits, mm-4.96 ± 2.09-3.03 ± 2.20-5.1 ± 2.37-2.17 ± 1.470.554
A-B difference, mm0.67 ± 2.772.38 ± 2.461.40 ± 2.244.02 ± 2.620.082
Anterior facial height, mm101.68 ± 4.89104.44 ± 4.8499.72 ± 8.69101.94 ± 7.261
Posterior facial height, mm64.93 ± 6.0465.75 ± 5.1660.72 ± 7.162.75 ± 8.361
Posterior/Anterior facial height, %63.85 ± 4.4462.75 ± 3.8360.97 ± 6.8361.49 ± 5.770.310
IMPA, °90.38 ± 4.6789.16 ± 4.1293.50 ± 8.9686.12 ± 6.710.012*
U1/SN, °98.77 ± 7.27111.11 ± 6.2599.75 ± 9.56105.83 ± 9.020.006*
U1/PP, °106.66 ± 7.72120.22 ± 6.74108.54 ± 9.28115.41 ± 5.430.049*
Interincisal angle, °136.50 ± 8.39125.22 ± 4.68131.50 ± 9045130.41 ± 9.410.007*
SNA-Me, mm55.93 ± 4.1056.56 ± 2.8153.66 ± 4.0355.16 ± 3.800.702

aValues are expressed as mean ± SD.

Table 2. Comparison of Total and Local Superimposition in Two Evaluated Groupsa
Chephalometric FeaturesGroup A (Removable Plate)Group B (Facemask + Removable Plate)P Value for Comparison of Group A and B
BeforeAfterBeforeAfter
Total super imposition
Upper incisor-SN69.44 ± 5.8371.66 ± 4.0968.91 ± 6.0372.66 ± 5.240.247
Upper incisor - T47.88 ± 5.8652.11 ± 5.9444.50 ± 6.3447.75 ± 6.350.382
Upper molar - SN55.66 ± 5.2957.88 ± 4.4255.41 ± 4.4659.66 ± 4.390.345
Upper molar - T14.66 ± 3.4214.11 ± 4.6711.91 ± 4.7113.75 ± 5.780.058
Lower incisor -SN67.11 ± 5.0169.22 ± 3.4568.91 ± 6.4070.25 ± 5.490.602
Lower incisor - T51.33 ± 6.4250.33 ± 5.7647.16 ± 5.4244.50 ± 6.760.219
Lower molar - SN57.44 ± 5.9359.11 ± 4.9157.25 ± 4.2460 ± 4.430.310
Lower molar - T17.22 ± 4.0515.44 ± 4.0615.25 ± 4.0914.08 ± 5.800.508
Local superimposition of maxilla
Upper incisor-SN70 ± 6.1270.22 ± 4.8668.83 ± 7.0170.58 ± 5.120.464
Upper incisor-T48.77 ± 5.5452.11 ± 5.7344.50 ± 6.1246.50 ± 6.140.095
Upper molar - SN56.77 ± 5.3857.44 ± 4.5855.41 ± 4.3356.83 ± 5.180.345
Upper molar - T14.77 ± 3.8313.44 ± 4.4712.33 ± 4.1613.33 ± 5.140.041*
Local superimposition of mandible
lower incisor-SN67.11 ± 4.3465.33 ± 5.5268.08 ± 5.5366.66 ± 5.610.754
Lower incisor-T51.88 ± 6.6251.44 ± 5.8347 ± 5.0446.16 ± 4.541
Lower molar - SN57.88 ± 5.5355.66 ± 5.1758.16 ± 4.1558.58 ± 3.940.049*
Lower molar - T17.88 ± 3.6216.22 ± 3.9914.91 ± 4.1615.25 ± 4.090.004*

aValues are expressed as mean ± SD.

4. Discussion

The two groups included in the present study consisted of patients with Cl III malocclusion, who had undergone treatment with a Y-plate removable appliance or a Y-plate removable appliance combined with a facemask based on a treatment plan prepared by orthodontists. The aim of this study was to evaluate cephalometric changes in these patients during treatment and compare the changes between the two groups.

Evaluation of the effect of treatment on cephalometric indices in the removable appliance group showed that SNA, ANB, Wits appraisal and A-B difference had increased and the SNB index had decreased. In the facemask group, the SNA, ANB, Wits and A-B difference had increased. These findings showed that both treatment modalities had exerted positive effects on the skeletal relationship between the upper and lower jaws, resulting in a forward movement of the maxilla and an improvement in the ANB angle. However, it should be pointed out that the extent of these changes were completely different in the two groups. In the removable appliance group, the SNA angle increased only 1° but in the facemask group the changes in the SNA angle were much higher due to the application of greater forces in the forward direction by the facemask (+5.12°). An important consideration in the evaluation of the findings was the fact that in the facemask group although the SNB angle had decreased, this decrease was very small (less than 1°); however, in the removable appliance group, the SNB angle had decreased significantly (more than 1°), which might be attributed to a percentage of functional shift present in some patients treated with the removable appliance. In addition, an increase in the facial height in this group might indicate downward and backward rotation of the mandible and a decrease in the SNB angle.

The positive effects of the expansion of the maxilla on the antero-posterior position of the upper jaw have been reported in a number of previous studies, too. In this context, Habeeb et al. (27) showed that use of palatal expansion resulted in forward and downward movement of the maxilla. Some of the other studies that have shown the forward and downward movement of the maxilla during rapid expansion of the palate are studies by Haas in 1961 (21), Davis and Kronman (22), Wertz (23), Sarver and Johnston (24) and Basciftci and Karaman (25). In addition, the results of the present study in relation to the positive effects of facemask on the position of the maxilla are consistent with those of other studies on the effects of facemasks (10, 28-35).

Another cephalometric index that exhibited positive changes in both groups was the overjet. The positive changes in the overjet in removable appliance group can be explained by changes in the position of the maxilla and its forward movement and the backward movement of the mandible in this group and a significant increase in the angle of the upper incisors relative to the SN (more than 10°). In the facemask group, too, the forward movement of the maxilla and an increase in the angle of the upper incisors relative to the SN (around 6°) resulted in positive changes in the overjet. In this context, the effective length of the maxilla (which is shown by the Co-A index) had increased in the facemask group, resulting in an improvement in the position of the maxilla and upper incisors.

Evaluation of the vertical cephalometric indices determined in the present study showed that only changes in the overbite and the anterior facial height in the removable appliance group were significant; in this group, the removable appliance resulted in a decrease in overbite in the subjects evaluated. On the other hand, the anterior facial height increased significantly in the removable appliance group. There were no significant changes in other vertical indices, including ANS-Me, SN-GoGn and posterior-anterior facial height ratio. Such findings have also been reported in other studies including a study by Mergimos et al. (28).

More positive changes in SNA and ANB indices in the facemask group, compared to the removable appliance group, are attributed to the more positive effects exerted by the facemask on the position of the maxilla. In addition, overbite decreased during treatment in the removable appliance group while there were minor changes in the facemask group, which might be attributed to the rotation of the maxillary plane due to the effect of the direction of the force vector of the facemask, while in the removable appliance group only the effect of expansion was observed as decreasing of overbite. On top of that, in the facemask group, IMPA exhibited a significant decrease (almost 6 times more of that in the removable appliance group), which is attributed to the pressure exerted by the chin cup of the facemask on the lower incisors.

One of the most important differences was changes in U1-SN and U1-PP, which were higher in the removable appliance group compared to the facemask group. In the removable appliance group achieving a positive overjet, which is interpreted as a clinical success during treatment, was predominantly mediated by the forward movement of upper incisors and only a small proportion of it was achieved by the forward movement of the maxilla. However, in the facemask group the positive overjet was achieved by the forward movement of the maxilla, while the forward movement of the upper incisors occurred simultaneously due to the antero-posterior expansion. It should be pointed out that in this treatment modality the traction of the facemask is applied in association with the antero-posterior expansion to provide the space for tooth eruption.

Total superimposition revealed a significant increase in the distance between the upper incisors and vertical reference line in the removable appliance group, which is attributed to the protrusion of upper incisors due to the therapeutic interventions. In addition, the distance between the lower molars and the vertical reference of T decreased, which indicated a more posterior position of the whole mandible in such treatment.

Local superimposition showed a decrease in the distance between the lower incisors and the SN and in the distance between the lower molars and the SN in the removable appliance group, which shows extrusion of mandibular incisors and molars relative to the mandible. In fact, the mandible exhibited a backward and downward rotation, with extrusion of mandibular teeth.

Total superimposition in the facemask group revealed an increase in the distance between upper incisors and molars and the vertical and horizontal reference lines, indicating the occlusal drift of upper incisors and molars. In addition, local superimposition revealed an increase in the distance between the upper molars and SN due to their extrusion. Sung and Baik (34) also reported 2.5 - 3.5 mm of extrusion of maxillary molars in facemask therapy. Merwin et al. (36) too, reported extrusion of maxillary molars. Several studies (37-40) have reported extrusion of maxillary molars with the application of facemasks as a reason for the backward and downward rotation of the mandible. However, a study by Yuksel et al. (18) in 2001 did not reveal backward and downward rotation of the mandible despite extrusion of maxillary molars, similar to the results of the present study. It might be claimed that in the present study there was an insignificant increase in the mandibular plane due to the significant extrusion of maxillary molars. One of the interesting findings in total superimposition in relation to the mandibular teeth in the present study was a decrease in lower incisor-T index, which was attributed to a decrease in IMPA. In addition, there was a decrease in the lower incisor-SN index in the local superimposition, indicating extrusion of mandibular incisors during treatment with the facemask.

Although the results of the present study did not reveal any significant changes in the angle of the mandibular plane and overbite in the facemask group, a study by Ngan et al. (30) showed a mean decrease of 2.6 mm in overbite after protrusion of the maxilla in association with expansion. Such a difference in the results might be attributed to differences in the biomechanics of treatment between the present study and the study above. On the other hand, Chong et al. (29) did not report any significant changes in overbite, consistent with the results of the present study.

As discussed above, the total superimposition revealed a significant forward and downward movement of upper molars and incisors in the facemask group. Such movement of maxillary dentition has also been shown in studies by Baik (10), Kapust et al. (40) and Sung and Baik (34).

In addition, evaluation of superimpositions showed a significant forward movement of incisors in both groups. Such forward movement was generally 3.25 mm in the facemask group and 4.3 mm in the removable appliance group. A total of 2.00 mm of the 3.25-mm forward movement in the facemask group was due to the movement of the teeth relative to the maxilla and the rest was due to the skeletal effects of the facemask. In the removable appliance group, 3.4 mm of the 4.3-mm forward movement was due to tooth movement and the rest was due to the forward movement of the maxilla.

The results showed a 1 mm forward movement of upper molars in the facemask group, which was attributed to the dental effects of the facemask; however, in the removable appliance group there was a 1.3 mm backward movement of upper molars, which was due to their distalization. Studies by Yuksel et al. (18) and Kapust et al. (40) have shown the skeletal: dental effects ratios of 1:1 and 3:2, respectively. In the present study the skeletal: dental effects ratio was 2:3.2 in the facemask group, which shows higher dental effects compared to those of the studies above and this was attributed to the simultaneous provision of tooth eruption spaces.

One of the limitations of the present study was a lack of access to more patients and the impossibility of the evaluation of the patient compliance. It is suggested that a clinical trial will be undertaken with a larger sample size to evaluate the effects of these two treatment modalities on children with Cl III malocclusion.

4.1. Conclusion

The following changes were observed in the two groups evaluated in the present study.

Removable appliance group: The removable appliance resulted in the protrusion of upper incisors, forward movement of the maxilla and distal movement of the upper molars. In the vertical dimension, the anterior facial height increased and overbite decreased. In this group overjet was increased.

Facemask group: This appliance resulted in protrusion of upper incisors, retrusion of lower incisors, forward movement of maxilla and forward movement of upper molars. In the vertical dimension, the increase in the mandibular plane angle was not significant.

The ratios of skeletal: dental effects in the facemask and removable appliance groups were 2:3.2 and 1:3.75, respectively.

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