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Long-term stability of Class III malocclusion nonextraction treatment
Journal of the World Federation of Orthodontists 6 (2017) 20e27
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Research
Long-term stability of Class III malocclusion nonextraction treatment Guilherme Janson, Waleska Caldas*, Daniela Gamba Garib, Camilla Fiedler Foncatti Bauru Dental School, University of São Paulo, São Paulo, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 October 2016 Received in revised form 23 January 2017 Accepted 13 February 2017
Background: The aim of this study was to evaluate the long-term stability of successful therapy of patients with Class III malocclusion at the end of facial growth. Materials and methods: The experimental group comprised 18 patients with Class III malocclusion treated without extractions with a mean age of 11.8 years (SD 2.8) at pretreatment, 15.7 years (SD 1.8) at posttreatment, and 24.1 years (SD 5.4) at follow-up. The control group comprised 22 subjects with normal occlusion observed during a comparable period. Intragroup treatment changes were analyzed with paired t tests, and intergroup posttreatment changes were compared with t tests. A multiple regression analysis was used to evaluate the influence of all variables in the amount of overjet relapse. Results: In the long-term, the experimental group demonstrated no significant change in apical base relationship. A significant decrease in overjet and overbite was observed but both remained positive. The primary factor that contributed to the overjet decrease was the mandibular growth in the posttreatment period. There were no significant intergroup differences regarding skeletal changes during the posttreatment period; however, the maxillary and mandibular incisors had significantly different behavior in the experimental as compared with the control group. Conclusions: In the long-term, nonextraction Class III malocclusion treatment demonstrated clinical stability in 88.9% of the patients. The dentoskeletal improvements obtained with treatment remained stable during the posttreatment period. The greater amount of mandibular growth after active treatment was the major variable that determined instability of Class III malocclusion treatment. Ó 2017 World Federation of Orthodontists.
Keywords: Orthodontics Malocclusion Angle Class III Long-term effect
1. Introduction Class III malocclusion incidence varies between 3% and 13% of the population, depending on the ethnic origin of the observed sample [1], and approximately one-third of orthodontic patients exhibit a Class III malocclusion [2]. Despite a low incidence in the population, it is of special interest to the orthodontist due to esthetic impairment and poor prognosis of orthopedic and/or orthodontic correction of this malocclusion. Class III malocclusions in growing patients remain one of the most challenging problems in orthodontics, with respect to diagnosis, prognosis, and treatment, especially because of the unpredictable and potentially unfavorable nature of growth in patients with this malocclusion pattern [3,4]. One of the most challenging difficulties in treating patients with Class III malocclusion is the possibility of posttreatment relapse. A significant tendency of recurrence of the Class III growth pattern All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. * Corresponding author: Bauru Dental School, University of São Paulo, Bauru, São Paulo 17012901, Brazil. E-mail address: [email protected] (W. Caldas). 2212-4438/$ e see front matter Ó 2017 World Federation of Orthodontists. http://dx.doi.org/10.1016/j.ejwf.2017.02.001
after active treatment has been widely demonstrated, especially during the pubertal growth spurt [5e7]. Skeletal changes that occur during retention may attenuate, exaggerate, or maintain the dentoskeletal relationship [8]. Conversely, data on long-term stability have been mainly derived from follow-up studies on patients with growth remaining [5,6,9,10], which do not demonstrate the overall stability after complete growth [11e13]. Previous studies have assessed long-term stability of Class III malocclusion treatment in patients who were followed until the end of active facial growth [4,12e18]. Although these studies present good methodological quality, all used only cephalometric variables to assess treatment stability. Even though these parameters are useful to the researcher, it is also important to analyze the occlusal features, which may be the reason for patients’ complaints. Additionally, more emphasis should be given to the importance of analyzing the individual growth pattern when planning treatment and retention of such patients. Therefore, the aim of this study was to evaluate the long-term stability of posttreatment results in successfully treated Class III malocclusion at the end of facial growth, both with cephalograms and study models.
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2. Materials and methods Ethical approval was obtained from the Ethics Research Committee of Bauru Dental School, University of São Paulo, Brazil. The sample size was calculated based on an alpha significance level of 5% and beta of 20% to achieve 80% of power to detect a mean different of 2.7 mm with a standard deviation of 2.7 mm in Wits appraisal change between posttreatment and follow-up stages [17]. The sample size calculation showed that a sample size of 12 patients was needed. The sample was retrospectively selected from the files of the orthodontic department at Bauru Dental School, University of São Paulo, Brazil, according to the following inclusion criteria: (1) Class III malocclusion with an overjet equal to or smaller than 0 mm; (2) nonextraction and nonsurgical comprehensive orthodontic treatment performed during active facial growth; (3) successful correction of Class III malocclusion to at least a Class I molar relationship and an overjet greater than 0 mm; and (4) long-term posttreatment data obtained after completion of facial growth. Age limits were chosen to reasonably exclude patients whose facial growth was still substantially incomplete at the follow-up stage (women younger than 18 and men younger than 21 years [19,20]). Additional criteria were the absence of agenesis, supernumerary, or lost teeth. Patients who did not present any of the listed criteria were automatically excluded from the study. Thus, the final sample included 18 patients (6 male; 12 female), with a mean age of 11.8 years (SD 2.8) at pretreatment (T1), 15.7 years (SD 1.8) at posttreatment (T2), and 24.1 years (SD 5.4) at follow-up (T3). Patients had on average a half-cusp Class III molar relationship severity at T1. Treatment consisted of a first phase of orthopedic therapy with either a facemask, chincup, or a Frankel Regulator III appliance (alone or in association, selected according to each patient’s skeletal characteristics). All patients were successfully treated at least to an overjet greater than 0 mm and a Class I molar relationship. Treatment was followed by fixed edgewise appliances, with 0.022 0.028-inch conventional brackets associated with Class III elastics. Class III elastics were used to obtain overcorrection of Class III relationship whenever possible, or at least to work as active retention during treatment with fixed appliances. Mean treatment time was 3.4 years (SD 2.5). After the active treatment period, a Hawley plate was used for retention in the maxillary arch during a mean period of 1 year (6 months all day and 6 months bedtime only), and a canine-tocanine fixed retainer was bonded in the mandibular arch and recommended to be maintained at least until completion of growth. Two patients who were clinically and cephalometrically characterized to have an important mandibular protrusion component and three patients who reported family history of mandibular prognathism were asked to use bedtime chincups delivering 200 g of force per side as active retentions until completion of facial growth. Mean follow-up period was 8.3 years (SD 5.0). The control group comprised 22 subjects (12 male; 10 female) with normal occlusion, matched regarding age and sex, and followed during a comparable period to the experimental group posttreatment period (T2-T3). This group was selected from the longitudinal growth study sample of the “Iowa Facial Growth Study” (Department of Orthodontics, College of Dentistry, University of Iowa, Iowa City, IA) obtained from the online American Association of Orthodontists Foundation Craniofacial Growth Legacy Collection [21]. 2.1. Cephalometric analysis Lateral cephalometric headfilms of the experimental group were obtained from each subject at T1, T2, and T3. Because of the long
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time between the evaluation stages, the lateral headfilms were obtained with various radiograph machines that produced different magnification factors of the images, between 6% and 10.94%. The headfilms were digitized (MICROTEK Scan Maker, Hsinchu, Taiwan, model i800), traced, and analyzed with Dolphin Imaging 11.5 software (Patterson Dental Supply, Inc., Chatsworth, CA), which corrected the image magnification factors of the images. A customized cephalometric analysis generated 24 variables, 7 angular and 17 linear, for each tracing (Table 1; Fig. 1). 2.2. Dental casts and panoramic radiograph analysis Dental study casts also were obtained of the experimental group from each subject at T1, T2, and T3. To evaluate the initial malocclusion severity and the final occlusal results of the experimental group, the peer assessment rating (PAR) index was calculated according to the American weightings suggested by DeGuzman et al. [22] on the pre- and posttreatment dental study casts of each patient by one examiner. Initial and final occlusal characteristics were ranked by scores regarding molar and premolar anteroposterior relationship, overjet, overbite, midline, crossbite, and crowding to quantify the initial malocclusion severity (PAR1), the occlusal treatment results (PAR2), and the PAR treatment changes (PAR2ePAR1) [23,24]. To assess the occlusal and radiographic results and stability of orthodontic treatment, the Objective Grading System, developed by the American Board of Orthodontics, was used [25]. This system for scoring dental casts and panoramic radiographs contains eight criteria: alignment, marginal ridges, buccolingual inclination, occlusal relationships, occlusal contacts, overjet, interproximal contacts, and root angulation. 2.3. Error of the method All cephalometric and dental cast measurements were performed by the same experienced and calibrated examiner (W.C.). A month after the first measurements, 18 radiographs and 18 study casts were randomly selected and remeasured by the same investigator. The random errors were calculated according to P 2 Dahlberg’s formula ðSe2 ¼ d =2nÞ [26], where Se2 is the error variance and d is the difference between two determinations of the same variable, and the systematic errors were evaluated with dependent t tests, at P < 0.05 [27]. 2.4. Statistical analyses Normal distribution was verified with Kolmogorov-Smirnov tests. All variables showed normal distribution. Therefore, intergroup comparability regarding ages at posttreatment and observational periods were performed with t tests. Intergroup sex distribution was compared with c2 tests. The treatment (T2-T1) and the posttreatment (T3-T2) changes were evaluated with paired t tests; t tests were used to compare the posttreatment changes (T3-T2) in the experimental group with the control group changes during a comparable period. A backward stepwise multiple linear regression analysis was performed to determine the influence of treatment time, active retention time, the initial amount of overjet (overjet T1), the amount of overjet correction (overjet T2-T1), and the posttreatment changes in all variables on the amount of overjet relapse (overjet T3-T2). Results were regarded as significant at P < 0.05. All analyses were performed with Statistica for Windows 10 software (Statsoft, Tulsa, OK).
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G. Janson et al. / Journal of the World Federation of Orthodontists 6 (2017) 20e27
Table 1 Skeletal and dental cephalometric variables Skeletal cephalometric variables Maxillary component SNA ( ) Sella nasion to nasion point A angle A-NPerp (mm) Distance from A-point to a perpendicular to Frankfurt plane, through nasion Co-A (mm) Condylion to A-point distance Mandibular component SNB ( ) Sella nasion to nasion point B angle Pg-NPerp (mm) Distance from pogonion (Pg) point to a perpendicular to Frankfurt plane, through nasion Co-Gn (mm) Condylion to gnathion distance Maxillomandibular relationship ANB ( ) Nasion point A to nasion point B angle Wits (mm) Distance between perpendicular projections of points A and B on the functional occlusal plane Vertical component FMA ( ) Frankfort plane to mandibular plane angle SNGoGn ( ) Sella nasion to gonion gnathion angle LAFH (mm) Distance from anterior nasal spine to menton Dental cephalometric variables Maxillary dentoalveolar component Mx1.PP ( ) Maxillary incisor long axis to palatal plane angle Mx1-APerp (mm) Distance between most anterior point of maxillary incisor crown and a line perpendicular to palatal plane, tangent to A point. Reading is negative if the incisal edge is posterior to A point. Mx1-PP (mm) Perpendicular distance between incisal edge of maxillary incisor and palatal plane Mx6-APerp (mm) Distance between the mesio-buccal cusp tip of the maxillary first molar and a line perpendicular to palatal plane, tangent to A point. Reading is negative if the mesio-buccal cusp tip is posterior to A point. Mx6-PP (mm) Perpendicular distance between the mesio-buccal cusp tip of the maxillary first molar and palatal plane Mandibular dentoalveolar component IMPA ( ) Mandibular incisor long axis to mandibular plane angle Md1-PgPerp (mm) Distance between the most anterior point of the mandibular incisor crown and a perpendicular to mandibular plane, tangent to Pg. Reading is negative if the incisal edge is posterior to Pg. Md1-MP (mm) Perpendicular distance between incisal edge of mandibular incisor and mandibular plane Md6-PgPerp (mm) Distance between the mesio-buccal cusp tip of the mandibular first molar and a line perpendicular to mandibular plane, tangent to Pg. Reading is negative if the mesio-buccal cusp tip is posterior to Pg. Md6-MP (mm) Perpendicular distance between the mesio-buccal cusp tip of the mandibular first molar and mandibular plane Dental relationships Overjet (mm) Distance between incisal edges of maxillary and mandibular central incisors, parallel to the functional occlusal plane Overbite (mm) Distance between incisal edges of maxillary and mandibular central incisors, perpendicular to Frankfort plane M.Rel (mm) Distance between mesial points of maxillary and mandibular first molars, parallel to Frankfort plane. Reading is negative if the mesial point of maxillary first molar is posterior to the mesial point of mandibular first molar.
2.5. Clinical stability A “clinically significant” relapse of Class III malocclusion treatment was defined as an overjet equal to 0 mm or smaller, at T3. Therefore, to establish a clinical parameter as to the probability of Class III malocclusion correction stability, the percentages of
Fig. 1. Unusual cephalometric variables: 1, Mx1.PP; 2, Mx1-APerp; 3, Mx1-PP; 4, Mx6APerp; 5, Mx6-PP; 6, Md1-PgPerp, 7, Md1-MP; 8, Md6-PgPerp; 9, Md6-MP. Please see Table 1 for definitions of abbreviations.
patients with and without a “clinically significant” relapse were calculated from the total number of studied patients. 3. Results Among the 24 variables, only 4 had a systematic error: sella nasion point A; condylion to A-point distance; A point, nasion, B point (ANB); and overjet. The range of random errors varied from 0.20 (distance between the most anterior point of the mandibular incisor crown and a perpendicular to mandibular plane, tangent to pogonion) to 1.74 mm (distance from pogonion point to a perpendicular to Frankfurt plane, through nasion). The groups were comparable regarding the ages at the different stages and observational periods, and sex distribution (Table 2). During treatment, there was significant maxillary protrusion and increase in maxillary and mandibular effective lengths, improvement in maxillomandibular relationship, and increase in linear distance from anterior nasal spine to menton (LAFH) (Table 3; Figs. 2A and 3). The maxillary incisors were significantly labially tipped and protruded and the molars had significant mesial movement and vertical development. The mandibular incisors had significant retrusion and vertical development and the molars, vertical development. There were significant increases in overjet and overbite, and improvement in molar relationship and in the occlusal status. During the posttreatment period, there were significant increases in maxillary and mandibular effective lengths (Table 4; Figs. 2B and 3). The maxillary incisors and molars experienced significant vertical development. The mandibular incisors had significant labial tipping and the molars, vertical development. There was significant decrease in overjet and overbite and worsening of the occlusal status.
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4. Discussion
Table 2 Comparability of the experimental and control groups (t and c2 tests) Stage/Period
Experimental group, n ¼ 18
Control group, n ¼ 22
Mean
SD
Mean
SD
Age T1, y Age T2, y Age T3, y Length of therapy, y Length of follow-up, y Sex, n (%)
11.8 15.7 24.1 3.9
2.8 1.8 5.4 2.5
15.2 24.7
1.3 3.3
0.353* 0.649*
8.3
5.0
9.5
3.3
0.389*
Female, 10 (45.5)
0.307y
* y
Male, 6 (33.3)
Female, 12 (66.7)
Male, 12 (54.5)
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P
t test. c2 test.
The intergroup comparison showed significant differences in maxillary and mandibular incisor behavior (Table 5). The experimental group showed lingual tipping of the maxillary incisors and the control group showed labial tipping. The mandibular incisors had analogous but opposite changes in the groups. The multiple regression analysis showed that posttreatment changes in molar relationship toward Class III and increase in mandibular length were the most important factors correlated with the amount of posttreatment overjet decrease (Table 6). Two (11.1%) of the 18 patients in the experimental group had a clinically significant relapse. Therefore, long-term clinical stability of nonextraction Class III malocclusion treatment was 88.9%.
4.1. Skeletal stability The significant increase in maxillary protrusion obtained with treatment remained stable in the posttreatment period (Tables 3e5; Figs. 2 and 3). This might be consequent to similar increase in maxillary length of the experimental group, as compared with the control group during this period (Table 5). These results corroborate with previous studies that also found stability of maxillary changes in long-term posttreatment [4,7,12,13]. The treatment procedures did not significantly improve mandibular anteroposterior position and there were also no significant changes during the posttreatment period, although mandibular length continued to significantly increase (Tables 3e5; Figs. 2 and 3). However, this increase was within the normal range (Table 5). Other studies also have demonstrated long-term stability of the mandibular anteroposterior position [13,17]. On the other hand, several studies have found relapse of the mandibular changes obtained with treatment [16,28e30]. The maxillary and mandibular behavior after Class III treatment is discussed further in the present article. Improvement in apical base relationship obtained with treatment remained stable during the posttreatment period, as also reported in previous investigations [12e15,17] (Tables 3e5; Figs. 2 and 3). This was probably consequent to stability in maxillary and mandibular anteroposterior positions. Although there was significant increase in mandibular length in the posttreatment period, it was compensated by a significant increase in maxillary length. Consequently, behavior in apical base relationship was similar to the control group (Table 5).
Table 3 Treatment changes: T2-T1 (paired t tests) Variable
Pretreatment (T1) Mean
Maxillary component SNA A-NPerp Co-A Mandibular component SNB Pg-NPerp Co-Gn Maxillomandibular relationship ANB Wits Vertical component FMA SNGoGn LAFH Maxillary dentoalveolar component Mx1.PP Mx1-Aperp Mx1-PP Mx6-APerp Mx6-PP Mandibular dentoalveolar component IMPA Md1-PgPerp Md1-MP Md6-PgPerp Md6-MP Dental relationships Overjet Overbite Molar relationship PAR *
Statistically significant at P < 0.05.
Posttreatment (T2) SD
Difference
Mean
SD
P
81.6 0.8 81.9
3.5 2.7 5.3
82.6 2.0 85.2
4.0 4.0 4.1
1.1 1.2 3.4
0.003* 0.171 0.001*
81.8 3.4 112.8
3.4 4.3 9.1
81.7 4.7 118.8
3.1 4.8 6.3
0.0 1.3 6.0
0.933 0.082 0.001*
0.2 5.6
2.1 2.3
0.9 2.7
2.2 2.2
1.1 2.9
0.001* 0.000*
24.2 30.7 60.0
5.1 6.4 4.9
23.8 30.2 63.3
4.6 6.3 5.0
0.4 0.5 3.3
0.561 0.679 0.002*
117.0 4.3 23.5 26.7 15.8
7.1 2.1 2.1 2.6 3.6
122.8 5.9 24.0 24.5 18.0
4.1 1.7 2.0 2.1 2.2
5.8 1.6 0.5 2.2 2.3
0.004* 0.013* 0.361 0.009* 0.003*
86.9 10.5 36.2 36.8 27.8
8.9 4.3 2.9 5.2 2.9
86.8 12.3 39.1 37.5 29.5
8.2 5.1 2.6 4.8 2.8
0.1 1.8 2.9 0.7 1.8
0.931 0.001* 0.000* 0.253 0.005*
0.1 0.6 3.0 32.4
1.6 0.8 1.5 11.0
2.4 1.2 1.1 3.4
0.4 0.5 0.9 4.8
2.3 0.6 2.0 29.0
0.000* 0.010* 0.000* 0.000*
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G. Janson et al. / Journal of the World Federation of Orthodontists 6 (2017) 20e27
Fig. 3. Tracings generated by Dolphin Imaging 11.5 software superimposed on the sella-nasion line at sella. Superimpositions of the mean tracings of the pretreatment (black), posttreatment (red), and long-term follow-up (green) stages.
Fig. 2. Patients’ mean tracings generated by Dolphin Imaging 11.5 software superimposed on the sella-nasion line at sella. (A) and (B) are based on superimpositions of the mean tracings to illustrate treatment and posttreatment changes. (A) Superimposition of the pretreatment (black) and posttreatment (red) stages. (B) Superimposition of the posttreatment (red) and long-term follow-up (green) stages.
the posttreatment period, with changes within the normal range (Table 5). Studies that evaluated treatment of patients presenting concave facial profile, with maxillary retrusion, demonstrated similar stability success rate to the current study [4,14,17]. In contrast, studies that involved patients with Class III malocclusion with a more significant mandibular component showed relapse of treatment outcomes in the long-term [16,28,29]. Tahmina et al. [16] reported that long-term stability was demonstrated when treated patients with Class III malocclusion tended to approach the patients with normal occlusion in terms of mandibular dimensions. Corroborating what was stated in the preceding paragraph, when comparing patients who presented relapse with patients who showed long-term stability, studies demonstrated that the relapse group had, on average, a slightly larger and more anteriorly positioned mandible before treatment than the stable group [18,29,33]. Additionally, during the posttreatment period, the length of the mandibular body and the effective mandibular length had a significantly greater increase in the patients who relapsed, as well as the anterior position of the mandible [16,30]. In the present study, although no statistically significant differences were found in posttreatment changes in mandibular length (condilion-gnation) between the experimental and control groups, this variable presented a significant inverse correlation with the decrease in overjet in the posttreatment period, when the multiple regression analysis was performed (Table 6). These results confirm the influence of mandibular growth on posttreatment stability.
4.2. Dentoalveolar stability The significant increase in LAFH during treatment may have been consequent to the mechanotherapy used, associated with normal growth [4,31,32]. However, it had no significant increase in
The maxillary incisors that were labially tipped and protruded during treatment remained stable during the posttreatment period
G. Janson et al. / Journal of the World Federation of Orthodontists 6 (2017) 20e27
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Table 4 Posttreatment changes: T3-T2 (paired t tests) Variable
Maxillary component SNA A-NPerp Co-A Mandibular component SNB Pg-NPerp Co-Gn Maxillomandibular relationship ANB Wits Vertical component FMA SNGoGn LAFH Maxillary dentoalveolar component Mx1.PP Mx1-Aperp Mx1-PP Mx6-APerp Mx6-PP Mandibular dentoalveolar component IMPA Md1-PgPerp Md1-MP Md6-PgPerp Md6-MP Dental relationships Overjet Overbite Molar relationship Objective grading system *
Posttreatment (T2)
Follow-up (T3)
Difference
P
Mean
SD
Mean
SD
82.6 2.0 85.2
4.0 4.0 4.1
82.7 2.5 87.3
3.9 3.3 5.7
0.1 0.5 2.1
0.980 0.413 0.002*
81.7 4.7 118.8
3.1 4.8 6.3
82.1 5.8 123.4
3.8 6.2 8.7
0.4 1.1 4.6
0.193 0.392 0.009*
0.9 2.7
2.2 2.2
0.6 2.7
1.9 2.4
0.3 0.0
0.223 0.990
23.8 30.2 63.3
4.6 6.3 5.0
22.9 29.5 65.2
5.1 7.0 6.0
0.9 0.7 1.9
0.190 0.061 0.052
122.8 5.9 24.0 24.5 18.0
4.1 1.7 2.0 2.1 2.2
122.6 5.8 24.9 24.3 19.5
5.4 1.7 2.3 1.6 2.5
0.2 0.1 0.9 0.2 1.5
0.819 0.610 0.023* 0.654 0.013*
86.8 12.2 39.1 37.5 29.5
8.2 5.1 2.6 4.8 2.8
89.3 12.2 39.8 37.4 30.8
9.1 5.2 3.5 5.2 3.5
2.5 0.0 0.7 0.1 1.3
0.013* 0.958 0.179 0.923 0.020*
2.4 1.2 1.1 14.8
0.4 0.5 0.9 7.3
1.7 0.7 1.8 18.7
1.0 0.8 1.4 8.9
0.7 0.5 0.7 3.8
0.004* 0.000* 0.084 0.001*
Statistically significant at P < 0.05.
(Tables 3 and 4; Figs. 2 and 3), as previously reported [12e14]. However, they had a significantly different behavior compared with normal occlusion that usually presents labial tipping of these teeth with normal growth [13] (Table 5). This may compromise the overjet in the long-term posttreatment period. The maxillary molars experienced mesialization and vertical development with treatment, probably consequent to the use of Class III elastics and growth [34,35]. Molar changes in the posttreatment period were similar to normal growth and therefore would not be a contributing factor for malocclusion relapse. The mandibular incisors were significantly retruded and extruded with treatment, probably consequent to the use of Class III elastics, and experienced significant labial tipping in the posttreatment period (Tables 3e5; Figs. 2 and 3). Class III elastics may have prevented the mandibular incisors from protruding and labially tipping during leveling and alignment in the process of decompensating the Class III malocclusion, with treatment. However, in the posttreatment period, they were significantly labially tipped, as previously reported [7,12,13]. Labial tipping is a significantly opposite change that occurs with normal growth and may be a contributing factor for overjet decrease [13] (Table 5). The mandibular molars experienced vertical development with treatment, probably consequent to normal growth [6,16]. Molar changes in the posttreatment period were similar to normal growth and therefore would not be a contributing factor for malocclusion relapse (Table 5). Overjet and overbite, which had significantly increased during treatment, significantly decreased in the posttreatment period (Tables 3 and 4; Figs. 2 and 3). These posttreatment changes were similar to normal growth (Table 5); however, both remained
positive at the long-term posttreatment stage. Molar relationship, which had significant improvement with treatment, demonstrated stability during the posttreatment period due to behavior similar to the control group (Table 5). Similar results have been previously reported [15,17,36]. According to the PAR index, the initial malocclusion severity and the treatment difficulty of the sample are considered moderate [22]. A great malocclusion severity was not expected because these patients were treated with nonextraction. More severe cases may require extraction or even orthodontic-surgical approaches [36,37]. There was significant occlusal improvement of 89.5% during treatment, which is greater than the minimum improvement of 65.0% recommended to be obtained with orthodontic treatment, showing that good treatment was provided to these patients [22]. This was also confirmed by the posttreatment Objective Grading System (OGS) of 14.8. In general, when the OGS score is greater than 30, treatment outcome is considered as failure, and when the score is less than 20 it is considered successful [25]. The discrete dentoalveolar cephalometric relapses contributed to produce a significant occlusal relapse, demonstrated by a decrease in OGS in the posttreatment period. However, the score was still less than 20 at T3 (Table 4). 4.3. Clinical stability The decrease in overjet previously mentioned demonstrates only whether the changes in these variables between T2 and T3 are mathematically significant in the experimental group and in relation to a control group. Although this parameter can be useful and understandable to the researcher, it does not show the clinician
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G. Janson et al. / Journal of the World Federation of Orthodontists 6 (2017) 20e27
Table 5 Results of t tests between changes during the long-term posttreatment period of the experimental group (T3-T2) and changes in the control group during a comparable period (t tests) Variable
Experimental group
Control group
Mean
SD
Mean
SD
1.0 2.6 3.0
0.6 0.8 3.7
0.6 1.3 3
0.290 0.638 0.258
1.1 5.5 8.7
0.6 0.9 4.0
1 3.2 5.0
0.461 0.887 0.772
1.9 1.8
0 0.7
0.9 1.6
0.373 0.201
2.7 1.5 3.8
0.4 0.5 3.4
1 1 4.4
0.471 0.605 0.267
3.5 1.3 1.6 1.8 2.3
2.6 0.5 0.8 0.8 1.9
3 0.9 1.7 1.7 2.3
0.011* 0.068 0.865 0.328 0.644
3.8 1.8 2.1 2.4 2.1
1.5 0.8 1.9 0.2 2.4
3.6 1.2 2.1 2.3 2
0.002* 0.074 0.060 0.894 0.090
0.8 0.5 1.7
0.4 0.5 0.4
0.7 1.1 0.5
0.215 0.883 0.340
Maxillary component SNA 0.1 A-NPerp 0.5 Co-A 2.1 Mandibular component SNB 0.4 Pg-NPerp 1.1 Co-Gn 4.6 Maxillomandibular relationship ANB 0.3 Wits 0.0 Vertical component FMA 0.9 SNGoGn 0.7 LAFH 1.9 Maxillary dentoalveolar component Mx1.PP 0.2 Mx1-Aperp 0.1 Mx1-PP 0.9 Mx6-APerp 0.2 Mx6-PP 1.5 Mandibular dentoalveolar component IMPA 2.5 Md1-PgPerp 0.0 Md1-MP 0.7 Md6-PgPerp 0.1 Md6-MP 1.3 Dental relationships Overjet 0.7 Overbite 0.5 Molar relationship 0.7 *
P
Statistically significant at P < 0.05.
whether the patients had a negative overjet (which is perceived by the patient and might be the reason for complaints) again at the long-term follow-up stage. It also does not represent the percentage of patients who might or might not have a negative overjet again in the long-term. For these reasons, the “clinically significant” relapse of Class III malocclusion treatment was evaluated. It was observed that only 2 (11.1%) of the 18 patients in the experimental group had a clinically significant relapse at T3. Consequently, 88.9% of the patients had a clinically significant stability of Class III malocclusion correction in the long-term. The explanation for the statistical stability of the studied variables and the high percentage of patients with significant clinical stability in the long-term, in this study, might be that individuals in the experimental group were mostly patients without an obvious mandibular involvement in the Class III discrepancy. Comparisons of follow-up variations on mandibular components between the experimental and the control groups
Table 6 Results of multiple linear regression analysis with the amount of overjet relapse in the posttreatment period (overjet T3-T2) as the dependent variable Variables
r
P
Treatment time Active retention time Overjet T1 Overjet T2-T1 Molar relationship T3-T2 Co-Gn T3-T2
0.89 0.31 0.12 0.08 0.066 0.48
0.391 0.842 0.648 0.742 0.003* 0.045*
*
Statistically significant at P < 0.05.
confirm that the patients with Class III malocclusion in the present study did not have a significant mandibular protrusion tendency; only 3 of the 18 patients reported family history of mandibular prognathism. The study performed by Ferro et al. [14], which, as in the current study, evaluated Class III comprehensive treatment stability after the end of facial growth and in which patients were also asked to use bedtime chincups when stability seemed tenuous, demonstrated very similar results, with 88.5% of patients having a positive overjet at the long-term follow-up. Other studies that evaluated treatment stability according to the change in molar relationship in addition to overjet [15] or in ANB angle [4], found smaller percentages of long-term clinical stability of 73% and 60%, respectively. However, as stated previously, neither molar relationship nor ANB angle are parameters observed by lay patients and are not common reasons for complaint. In the study conducted by Chen et al. [4], for example, even though 40% of the patients in the experimental group were classified as “unstable” based on the reduction of the ANB angle, only 10% of the patients had an edge-to-edge incisor relationship at follow-up. When orthopedic therapy is discontinued and fixed appliances installed, a bedtime chincup can be used at night. After removal of the fixed appliances, the chincup or a functional appliance should be maintained until the end of active growth [17]. Few studies reported the use of active retention after Class III treatment in growing patients [14,31,36]. Ferro et al. [14] used a bedtime chincup retention for 2 to 3 years after active treatment, and for a variable additional period (1 to 7 years) when stability seemed tenuous, as detected by reduction of the overjet in the posttreatment observation period. In the study performed by Battagel and Orton [11], a mandibular headgear was used until facial growth was presumed to be complete. Levin et al. [35] reported the use of a Function Regulator 3 of Fränkel at night for approximately 3 years after active treatment with the same appliance. All these studies showed a high percentage of stability of treatment changes. In the present study, 5 of the 18 patients were asked to use bedtime active retentions until completion of facial growth: 2 patients who were clinically and cephalometrically characterized as having an important mandibular involvement in the Class III discrepancy and 3 patients who reported family history of mandibular prognathism. Of those, the two patients who were thought to have unfavorable mandibular growth pattern remained clinically stable at long-term follow-up. Of the three patients who reported family history of mandibular prognathism, two did not comply with the use of the active retainers and correspond to the two patients who presented with significant clinical relapse. Even though one of the patients who reported family history of mandibular prognathism demonstrated long-term stability of Class III malocclusion correction after the use of active retention until completion of facial growth, we cannot imply that active retention will always overcome the genetic tendency of mandibular protrusion, especially because of the small number of individuals in this study who were asked to use active retainers. Longitudinal studies associating the facial growth pattern of the patients and their family members with the use of active retention are needed. According to the previous discussion, to achieve long-term stability of Class III malocclusion treatment, when planning treatment and retention of such patients, it is very important to analyze the individual’s growth pattern. The involvement of the maxilla and the mandible in the Class III discrepancy should be analyzed, as well as the growth pattern of close consanguineous relatives. Therefore, patients who are more likely to present excessive mandibular growth during the pubertal spurt can be identified. An active retainer and a tighter follow-up schedule to monitor the patient’s
G. Janson et al. / Journal of the World Federation of Orthodontists 6 (2017) 20e27
growth and the occlusal relationship are suggested after the end of Class III malocclusion treatment in growing patients. Furthermore, considering the difficulty of growth control, overcorrection of the dental intermaxillary discrepancy to 4 to 5 mm of overjet [28] may be necessary as an attempt to minimize the deleterious effects of posttreatment mandibular growth [13,14,28]. Because this was not a randomized controlled trial, one must bear in mind that these results apply to patients with the mentioned characteristics, treated with the described approaches. 5. Conclusions The following are the conclusions of the study: 1. The improvements in apical base relationship and in dentoalveolar relationship obtained with treatment remained stable during the posttreatment period. 2. Long-term clinical stability of Class III malocclusion treatment (overjet >0) was observed in 88.9% of the patients. 3. The amount of mandibular growth after active treatment was the major variable that determined long-term success of Class III treatment. References [1] El-Mangoury NH, Mostafa YA. Epidemiologic panorama of dental occlusion. Angle Orthod 1990;60:207e14. [2] Takada K, Petdachai S, Sakuda M. Changes in dentofacial morphology in skeletal Class III children treated by a modified maxillary protraction headgear and a chin cup: a longitudinal cephalometric appraisal. Eur J Orthod 1993;15:211e21. [3] Kim JH, Viana MA, Graber TM, Omerza FF, BeGole EA. The effectiveness of protraction face mask therapy: a meta-analysis. Am J Orthod Dentofacial Orthop 1999;115:675e85. [4] Chen L, Chen R, Yang Y, Ji G, Shen G. The effects of maxillary protraction and its long-term stabilityda clinical trial in Chinese adolescents. Eur J Orthod 2012;34:88e95. [5] Gallagher RW, Miranda F, Buschang PH. Maxillary protraction: treatment and posttreatment effects. Am J Orthod Dentofacial Orthop 1998;113:612e9. [6] Macdonald KE, Kapust AJ, Turley PK. Cephalometric changes after the correction of class III malocclusion with maxillary expansion/facemask therapy. Am J Orthod Dentofacial Orthop 1999;116:13e24. [7] Westwood PV, McNamara Jr JA, Baccetti T, Franchi L, Sarver DM. Long-term effects of Class III treatment with rapid maxillary expansion and facemask therapy followed by fixed appliances. Am J Orthod Dentofacial Orthop 2003;123:306e20. [8] Nanda RS, Nanda SK. Considerations of dentofacial growth in long-term retention and stability: is active retention needed? Am J Orthod Dentofacial Orthop 1992;101:297e302. [9] Deguchi T, Kanomi R, Ashizawa Y, Rosenstein SW. Very early face mask therapy in Class III children. Angle Orthod 1999;69:349e55. [10] Baccetti T, Franchi L, McNamara Jr JA. Treatment and posttreatment craniofacial changes after rapid maxillary expansion and facemask therapy. Am J Orthod Dentofacial Orthop 2000;118:404e13. [11] Battagel JM, Orton HS. Class III malocclusion: the post-retention findings following a non-extraction treatment approach. Eur J Orthod 1993;15:45e55. [12] Deguchi T, Kitsugi A. Stability of changes associated with chin cup treatment. Angle Orthod 1996;66:139e45. [13] Yoshida I, Ishii H, Yamaguchi N, Mizoguchi I. Maxillary protraction and chincap appliance treatment effects and long-term changes in skeletal class III patients. Angle Orthod 1999;69:543e52.
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[14] Ferro A, Nucci LP, Ferro F, Gallo C. Long-term stability of skeletal Class III patients treated with splints, Class III elastics, and chincup. Am J Orthod Dentofacial Orthop 2003;123:423e34. [15] Masucci C, Franchi L, Defraia E, Mucedero M, Cozza P, Baccetti T. Stability of rapid maxillary expansion and facemask therapy: a long-term controlled study. Am J Orthod Dentofacial Orthop 2011;140:493e500. [16] Tahmina K, Tanaka E, Tanne K. Craniofacial morphology in orthodontically treated patients of class III malocclusion with stable and unstable treatment outcomes. Am J Orthod Dentofacial Orthop 2000;117:681e90. [17] Baccetti T, Rey D, Oberti G, Stahl F, McNamara Jr JA. Long-term outcomes of Class III treatment with mandibular cervical headgear followed by fixed appliances. Angle Orthod 2009;79:828e34. [18] Wells AP, Sarver DM, Proffit WR. Long-term efficacy of reverse pull headgear therapy. Angle Orthod 2006;76:915e22. [19] Bjork A, Skieller V. Growth of the maxilla in three dimensions as revealed radiographically by the implant method. Br J Orthod 1977;4:53e64. [20] Behrents R. Growth in the aging craniofacial skeleton. Monograph 17. Craniofacial growth series. Ann Arbor: Center for Human Growth and Development, University of Michigan; 1985. [21] Battagel JM. Discriminant analysis: a model for the prediction of relapse in Class III children treated orthodontically by a non-extraction technique. Eur J Orthod 1993;15:199e209. [22] DeGuzman L, Bahiraei D, Vig KW, Vig PS, Weyant RJ, O’Brien K. The validation of the Peer Assessment Rating index for malocclusion severity and treatment difficulty. Am J Orthod Dentofacial Orthop 1995;107:172e6. [23] Chew MT, Sandham A. Effectiveness and duration of two-arch fixed appliance treatment. Aust Orthod J 2000;16:98e103. [24] Mascarenhas AK, Vig K. Comparison of orthodontic treatment outcomes in educational and private practice settings. J Dent Educ 2002;66:94e9. [25] Casko JS, Vaden JL, Kokich VG, et al. Objective grading system for dental casts and panoramic radiographs. Am J Orthod Dentofacial Orthop 1998;114:589e99. [26] Dahlberg G. Statistical methods for medical and biological students. New York: Interscience; 1940. [27] Houston WJ. The analysis of errors in orthodontic measurements. Am J Orthod 1983;83:382e90. [28] Turley PK. Orthopedic correction of Class III malocclusion: retention and phase II therapy. J Clin Orthod 1996;30:313e24. [29] Ghiz MA, Ngan P, Gunel E. Cephalometric variables to predict future success of early orthopedic Class III treatment. Am J Orthod Dentofacial Orthop 2005;127:301e6. [30] Ngan PW, Hagg U, Yiu C, Wei SH. Treatment response and long-term dentofacial adaptations to maxillary expansion and protraction. Semin Orthod 1997;3:255e64. [31] Baccetti T, McGill JS, Franchi L, McNamara Jr JA, Tollaro I. Skeletal effects of early treatment of Class III malocclusion with maxillary expansion and facemask therapy. Am J Orthod Dentofacial Orthop 1998;113:333e43. [32] Baccetti T, Franchi L, McNamara Jr JA. Cephalometric variables predicting the long-term success or failure of combined rapid maxillary expansion and facial mask therapy. Am J Orthod Dentofacial Orthop 2004;126:16e22. [33] Janson G, de Souza JE, Alves Fde A, et al. Extreme dentoalveolar compensation in the treatment of Class III malocclusion. Am J Orthod Dentofacial Orthop 2005;128:787e94. [34] Janson G, Freitas MR, Araki J, Franco EJ, Barros SE. Class III subdivision malocclusion corrected with asymmetric intermaxillary elastics. Am J Orthod Dentofacial Orthop 2010;138:221e30. [35] Levin AS, McNamara Jr JA, Franchi L, Baccetti T, Frankel C. Short-term and long-term treatment outcomes with the FR-3 appliance of Frankel. Am J Orthod Dentofacial Orthop 2008;134:513e24. [36] Janson M, Janson G, Sant’Ana E, Nakamura A, de Freitas MR. Segmental LeFort I osteotomy for treatment of a Class III malocclusion with temporomandibular disorder. J Appl Oral Sci 2008;16:302e9. [37] Akinci Cansunar H, Uysal T. Comparison of orthodontic treatment outcomes in nonextraction, 2 maxillary premolar extraction, and 4 premolar extraction protocols with the American Board of Orthodontics objective grading system. Am J Orthod Dentofacial Orthop 2014;145:595e602.
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Research
Long-term stability of Class III malocclusion nonextraction treatment Guilherme Janson, Waleska Caldas*, Daniela Gamba Garib, Camilla Fiedler Foncatti Bauru Dental School, University of São Paulo, São Paulo, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 October 2016 Received in revised form 23 January 2017 Accepted 13 February 2017
Background: The aim of this study was to evaluate the long-term stability of successful therapy of patients with Class III malocclusion at the end of facial growth. Materials and methods: The experimental group comprised 18 patients with Class III malocclusion treated without extractions with a mean age of 11.8 years (SD 2.8) at pretreatment, 15.7 years (SD 1.8) at posttreatment, and 24.1 years (SD 5.4) at follow-up. The control group comprised 22 subjects with normal occlusion observed during a comparable period. Intragroup treatment changes were analyzed with paired t tests, and intergroup posttreatment changes were compared with t tests. A multiple regression analysis was used to evaluate the influence of all variables in the amount of overjet relapse. Results: In the long-term, the experimental group demonstrated no significant change in apical base relationship. A significant decrease in overjet and overbite was observed but both remained positive. The primary factor that contributed to the overjet decrease was the mandibular growth in the posttreatment period. There were no significant intergroup differences regarding skeletal changes during the posttreatment period; however, the maxillary and mandibular incisors had significantly different behavior in the experimental as compared with the control group. Conclusions: In the long-term, nonextraction Class III malocclusion treatment demonstrated clinical stability in 88.9% of the patients. The dentoskeletal improvements obtained with treatment remained stable during the posttreatment period. The greater amount of mandibular growth after active treatment was the major variable that determined instability of Class III malocclusion treatment. Ó 2017 World Federation of Orthodontists.
Keywords: Orthodontics Malocclusion Angle Class III Long-term effect
1. Introduction Class III malocclusion incidence varies between 3% and 13% of the population, depending on the ethnic origin of the observed sample [1], and approximately one-third of orthodontic patients exhibit a Class III malocclusion [2]. Despite a low incidence in the population, it is of special interest to the orthodontist due to esthetic impairment and poor prognosis of orthopedic and/or orthodontic correction of this malocclusion. Class III malocclusions in growing patients remain one of the most challenging problems in orthodontics, with respect to diagnosis, prognosis, and treatment, especially because of the unpredictable and potentially unfavorable nature of growth in patients with this malocclusion pattern [3,4]. One of the most challenging difficulties in treating patients with Class III malocclusion is the possibility of posttreatment relapse. A significant tendency of recurrence of the Class III growth pattern All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. * Corresponding author: Bauru Dental School, University of São Paulo, Bauru, São Paulo 17012901, Brazil. E-mail address: [email protected] (W. Caldas). 2212-4438/$ e see front matter Ó 2017 World Federation of Orthodontists. http://dx.doi.org/10.1016/j.ejwf.2017.02.001
after active treatment has been widely demonstrated, especially during the pubertal growth spurt [5e7]. Skeletal changes that occur during retention may attenuate, exaggerate, or maintain the dentoskeletal relationship [8]. Conversely, data on long-term stability have been mainly derived from follow-up studies on patients with growth remaining [5,6,9,10], which do not demonstrate the overall stability after complete growth [11e13]. Previous studies have assessed long-term stability of Class III malocclusion treatment in patients who were followed until the end of active facial growth [4,12e18]. Although these studies present good methodological quality, all used only cephalometric variables to assess treatment stability. Even though these parameters are useful to the researcher, it is also important to analyze the occlusal features, which may be the reason for patients’ complaints. Additionally, more emphasis should be given to the importance of analyzing the individual growth pattern when planning treatment and retention of such patients. Therefore, the aim of this study was to evaluate the long-term stability of posttreatment results in successfully treated Class III malocclusion at the end of facial growth, both with cephalograms and study models.
G. Janson et al. / Journal of the World Federation of Orthodontists 6 (2017) 20e27
2. Materials and methods Ethical approval was obtained from the Ethics Research Committee of Bauru Dental School, University of São Paulo, Brazil. The sample size was calculated based on an alpha significance level of 5% and beta of 20% to achieve 80% of power to detect a mean different of 2.7 mm with a standard deviation of 2.7 mm in Wits appraisal change between posttreatment and follow-up stages [17]. The sample size calculation showed that a sample size of 12 patients was needed. The sample was retrospectively selected from the files of the orthodontic department at Bauru Dental School, University of São Paulo, Brazil, according to the following inclusion criteria: (1) Class III malocclusion with an overjet equal to or smaller than 0 mm; (2) nonextraction and nonsurgical comprehensive orthodontic treatment performed during active facial growth; (3) successful correction of Class III malocclusion to at least a Class I molar relationship and an overjet greater than 0 mm; and (4) long-term posttreatment data obtained after completion of facial growth. Age limits were chosen to reasonably exclude patients whose facial growth was still substantially incomplete at the follow-up stage (women younger than 18 and men younger than 21 years [19,20]). Additional criteria were the absence of agenesis, supernumerary, or lost teeth. Patients who did not present any of the listed criteria were automatically excluded from the study. Thus, the final sample included 18 patients (6 male; 12 female), with a mean age of 11.8 years (SD 2.8) at pretreatment (T1), 15.7 years (SD 1.8) at posttreatment (T2), and 24.1 years (SD 5.4) at follow-up (T3). Patients had on average a half-cusp Class III molar relationship severity at T1. Treatment consisted of a first phase of orthopedic therapy with either a facemask, chincup, or a Frankel Regulator III appliance (alone or in association, selected according to each patient’s skeletal characteristics). All patients were successfully treated at least to an overjet greater than 0 mm and a Class I molar relationship. Treatment was followed by fixed edgewise appliances, with 0.022 0.028-inch conventional brackets associated with Class III elastics. Class III elastics were used to obtain overcorrection of Class III relationship whenever possible, or at least to work as active retention during treatment with fixed appliances. Mean treatment time was 3.4 years (SD 2.5). After the active treatment period, a Hawley plate was used for retention in the maxillary arch during a mean period of 1 year (6 months all day and 6 months bedtime only), and a canine-tocanine fixed retainer was bonded in the mandibular arch and recommended to be maintained at least until completion of growth. Two patients who were clinically and cephalometrically characterized to have an important mandibular protrusion component and three patients who reported family history of mandibular prognathism were asked to use bedtime chincups delivering 200 g of force per side as active retentions until completion of facial growth. Mean follow-up period was 8.3 years (SD 5.0). The control group comprised 22 subjects (12 male; 10 female) with normal occlusion, matched regarding age and sex, and followed during a comparable period to the experimental group posttreatment period (T2-T3). This group was selected from the longitudinal growth study sample of the “Iowa Facial Growth Study” (Department of Orthodontics, College of Dentistry, University of Iowa, Iowa City, IA) obtained from the online American Association of Orthodontists Foundation Craniofacial Growth Legacy Collection [21]. 2.1. Cephalometric analysis Lateral cephalometric headfilms of the experimental group were obtained from each subject at T1, T2, and T3. Because of the long
21
time between the evaluation stages, the lateral headfilms were obtained with various radiograph machines that produced different magnification factors of the images, between 6% and 10.94%. The headfilms were digitized (MICROTEK Scan Maker, Hsinchu, Taiwan, model i800), traced, and analyzed with Dolphin Imaging 11.5 software (Patterson Dental Supply, Inc., Chatsworth, CA), which corrected the image magnification factors of the images. A customized cephalometric analysis generated 24 variables, 7 angular and 17 linear, for each tracing (Table 1; Fig. 1). 2.2. Dental casts and panoramic radiograph analysis Dental study casts also were obtained of the experimental group from each subject at T1, T2, and T3. To evaluate the initial malocclusion severity and the final occlusal results of the experimental group, the peer assessment rating (PAR) index was calculated according to the American weightings suggested by DeGuzman et al. [22] on the pre- and posttreatment dental study casts of each patient by one examiner. Initial and final occlusal characteristics were ranked by scores regarding molar and premolar anteroposterior relationship, overjet, overbite, midline, crossbite, and crowding to quantify the initial malocclusion severity (PAR1), the occlusal treatment results (PAR2), and the PAR treatment changes (PAR2ePAR1) [23,24]. To assess the occlusal and radiographic results and stability of orthodontic treatment, the Objective Grading System, developed by the American Board of Orthodontics, was used [25]. This system for scoring dental casts and panoramic radiographs contains eight criteria: alignment, marginal ridges, buccolingual inclination, occlusal relationships, occlusal contacts, overjet, interproximal contacts, and root angulation. 2.3. Error of the method All cephalometric and dental cast measurements were performed by the same experienced and calibrated examiner (W.C.). A month after the first measurements, 18 radiographs and 18 study casts were randomly selected and remeasured by the same investigator. The random errors were calculated according to P 2 Dahlberg’s formula ðSe2 ¼ d =2nÞ [26], where Se2 is the error variance and d is the difference between two determinations of the same variable, and the systematic errors were evaluated with dependent t tests, at P < 0.05 [27]. 2.4. Statistical analyses Normal distribution was verified with Kolmogorov-Smirnov tests. All variables showed normal distribution. Therefore, intergroup comparability regarding ages at posttreatment and observational periods were performed with t tests. Intergroup sex distribution was compared with c2 tests. The treatment (T2-T1) and the posttreatment (T3-T2) changes were evaluated with paired t tests; t tests were used to compare the posttreatment changes (T3-T2) in the experimental group with the control group changes during a comparable period. A backward stepwise multiple linear regression analysis was performed to determine the influence of treatment time, active retention time, the initial amount of overjet (overjet T1), the amount of overjet correction (overjet T2-T1), and the posttreatment changes in all variables on the amount of overjet relapse (overjet T3-T2). Results were regarded as significant at P < 0.05. All analyses were performed with Statistica for Windows 10 software (Statsoft, Tulsa, OK).
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G. Janson et al. / Journal of the World Federation of Orthodontists 6 (2017) 20e27
Table 1 Skeletal and dental cephalometric variables Skeletal cephalometric variables Maxillary component SNA ( ) Sella nasion to nasion point A angle A-NPerp (mm) Distance from A-point to a perpendicular to Frankfurt plane, through nasion Co-A (mm) Condylion to A-point distance Mandibular component SNB ( ) Sella nasion to nasion point B angle Pg-NPerp (mm) Distance from pogonion (Pg) point to a perpendicular to Frankfurt plane, through nasion Co-Gn (mm) Condylion to gnathion distance Maxillomandibular relationship ANB ( ) Nasion point A to nasion point B angle Wits (mm) Distance between perpendicular projections of points A and B on the functional occlusal plane Vertical component FMA ( ) Frankfort plane to mandibular plane angle SNGoGn ( ) Sella nasion to gonion gnathion angle LAFH (mm) Distance from anterior nasal spine to menton Dental cephalometric variables Maxillary dentoalveolar component Mx1.PP ( ) Maxillary incisor long axis to palatal plane angle Mx1-APerp (mm) Distance between most anterior point of maxillary incisor crown and a line perpendicular to palatal plane, tangent to A point. Reading is negative if the incisal edge is posterior to A point. Mx1-PP (mm) Perpendicular distance between incisal edge of maxillary incisor and palatal plane Mx6-APerp (mm) Distance between the mesio-buccal cusp tip of the maxillary first molar and a line perpendicular to palatal plane, tangent to A point. Reading is negative if the mesio-buccal cusp tip is posterior to A point. Mx6-PP (mm) Perpendicular distance between the mesio-buccal cusp tip of the maxillary first molar and palatal plane Mandibular dentoalveolar component IMPA ( ) Mandibular incisor long axis to mandibular plane angle Md1-PgPerp (mm) Distance between the most anterior point of the mandibular incisor crown and a perpendicular to mandibular plane, tangent to Pg. Reading is negative if the incisal edge is posterior to Pg. Md1-MP (mm) Perpendicular distance between incisal edge of mandibular incisor and mandibular plane Md6-PgPerp (mm) Distance between the mesio-buccal cusp tip of the mandibular first molar and a line perpendicular to mandibular plane, tangent to Pg. Reading is negative if the mesio-buccal cusp tip is posterior to Pg. Md6-MP (mm) Perpendicular distance between the mesio-buccal cusp tip of the mandibular first molar and mandibular plane Dental relationships Overjet (mm) Distance between incisal edges of maxillary and mandibular central incisors, parallel to the functional occlusal plane Overbite (mm) Distance between incisal edges of maxillary and mandibular central incisors, perpendicular to Frankfort plane M.Rel (mm) Distance between mesial points of maxillary and mandibular first molars, parallel to Frankfort plane. Reading is negative if the mesial point of maxillary first molar is posterior to the mesial point of mandibular first molar.
2.5. Clinical stability A “clinically significant” relapse of Class III malocclusion treatment was defined as an overjet equal to 0 mm or smaller, at T3. Therefore, to establish a clinical parameter as to the probability of Class III malocclusion correction stability, the percentages of
Fig. 1. Unusual cephalometric variables: 1, Mx1.PP; 2, Mx1-APerp; 3, Mx1-PP; 4, Mx6APerp; 5, Mx6-PP; 6, Md1-PgPerp, 7, Md1-MP; 8, Md6-PgPerp; 9, Md6-MP. Please see Table 1 for definitions of abbreviations.
patients with and without a “clinically significant” relapse were calculated from the total number of studied patients. 3. Results Among the 24 variables, only 4 had a systematic error: sella nasion point A; condylion to A-point distance; A point, nasion, B point (ANB); and overjet. The range of random errors varied from 0.20 (distance between the most anterior point of the mandibular incisor crown and a perpendicular to mandibular plane, tangent to pogonion) to 1.74 mm (distance from pogonion point to a perpendicular to Frankfurt plane, through nasion). The groups were comparable regarding the ages at the different stages and observational periods, and sex distribution (Table 2). During treatment, there was significant maxillary protrusion and increase in maxillary and mandibular effective lengths, improvement in maxillomandibular relationship, and increase in linear distance from anterior nasal spine to menton (LAFH) (Table 3; Figs. 2A and 3). The maxillary incisors were significantly labially tipped and protruded and the molars had significant mesial movement and vertical development. The mandibular incisors had significant retrusion and vertical development and the molars, vertical development. There were significant increases in overjet and overbite, and improvement in molar relationship and in the occlusal status. During the posttreatment period, there were significant increases in maxillary and mandibular effective lengths (Table 4; Figs. 2B and 3). The maxillary incisors and molars experienced significant vertical development. The mandibular incisors had significant labial tipping and the molars, vertical development. There was significant decrease in overjet and overbite and worsening of the occlusal status.
G. Janson et al. / Journal of the World Federation of Orthodontists 6 (2017) 20e27
4. Discussion
Table 2 Comparability of the experimental and control groups (t and c2 tests) Stage/Period
Experimental group, n ¼ 18
Control group, n ¼ 22
Mean
SD
Mean
SD
Age T1, y Age T2, y Age T3, y Length of therapy, y Length of follow-up, y Sex, n (%)
11.8 15.7 24.1 3.9
2.8 1.8 5.4 2.5
15.2 24.7
1.3 3.3
0.353* 0.649*
8.3
5.0
9.5
3.3
0.389*
Female, 10 (45.5)
0.307y
* y
Male, 6 (33.3)
Female, 12 (66.7)
Male, 12 (54.5)
23
P
t test. c2 test.
The intergroup comparison showed significant differences in maxillary and mandibular incisor behavior (Table 5). The experimental group showed lingual tipping of the maxillary incisors and the control group showed labial tipping. The mandibular incisors had analogous but opposite changes in the groups. The multiple regression analysis showed that posttreatment changes in molar relationship toward Class III and increase in mandibular length were the most important factors correlated with the amount of posttreatment overjet decrease (Table 6). Two (11.1%) of the 18 patients in the experimental group had a clinically significant relapse. Therefore, long-term clinical stability of nonextraction Class III malocclusion treatment was 88.9%.
4.1. Skeletal stability The significant increase in maxillary protrusion obtained with treatment remained stable in the posttreatment period (Tables 3e5; Figs. 2 and 3). This might be consequent to similar increase in maxillary length of the experimental group, as compared with the control group during this period (Table 5). These results corroborate with previous studies that also found stability of maxillary changes in long-term posttreatment [4,7,12,13]. The treatment procedures did not significantly improve mandibular anteroposterior position and there were also no significant changes during the posttreatment period, although mandibular length continued to significantly increase (Tables 3e5; Figs. 2 and 3). However, this increase was within the normal range (Table 5). Other studies also have demonstrated long-term stability of the mandibular anteroposterior position [13,17]. On the other hand, several studies have found relapse of the mandibular changes obtained with treatment [16,28e30]. The maxillary and mandibular behavior after Class III treatment is discussed further in the present article. Improvement in apical base relationship obtained with treatment remained stable during the posttreatment period, as also reported in previous investigations [12e15,17] (Tables 3e5; Figs. 2 and 3). This was probably consequent to stability in maxillary and mandibular anteroposterior positions. Although there was significant increase in mandibular length in the posttreatment period, it was compensated by a significant increase in maxillary length. Consequently, behavior in apical base relationship was similar to the control group (Table 5).
Table 3 Treatment changes: T2-T1 (paired t tests) Variable
Pretreatment (T1) Mean
Maxillary component SNA A-NPerp Co-A Mandibular component SNB Pg-NPerp Co-Gn Maxillomandibular relationship ANB Wits Vertical component FMA SNGoGn LAFH Maxillary dentoalveolar component Mx1.PP Mx1-Aperp Mx1-PP Mx6-APerp Mx6-PP Mandibular dentoalveolar component IMPA Md1-PgPerp Md1-MP Md6-PgPerp Md6-MP Dental relationships Overjet Overbite Molar relationship PAR *
Statistically significant at P < 0.05.
Posttreatment (T2) SD
Difference
Mean
SD
P
81.6 0.8 81.9
3.5 2.7 5.3
82.6 2.0 85.2
4.0 4.0 4.1
1.1 1.2 3.4
0.003* 0.171 0.001*
81.8 3.4 112.8
3.4 4.3 9.1
81.7 4.7 118.8
3.1 4.8 6.3
0.0 1.3 6.0
0.933 0.082 0.001*
0.2 5.6
2.1 2.3
0.9 2.7
2.2 2.2
1.1 2.9
0.001* 0.000*
24.2 30.7 60.0
5.1 6.4 4.9
23.8 30.2 63.3
4.6 6.3 5.0
0.4 0.5 3.3
0.561 0.679 0.002*
117.0 4.3 23.5 26.7 15.8
7.1 2.1 2.1 2.6 3.6
122.8 5.9 24.0 24.5 18.0
4.1 1.7 2.0 2.1 2.2
5.8 1.6 0.5 2.2 2.3
0.004* 0.013* 0.361 0.009* 0.003*
86.9 10.5 36.2 36.8 27.8
8.9 4.3 2.9 5.2 2.9
86.8 12.3 39.1 37.5 29.5
8.2 5.1 2.6 4.8 2.8
0.1 1.8 2.9 0.7 1.8
0.931 0.001* 0.000* 0.253 0.005*
0.1 0.6 3.0 32.4
1.6 0.8 1.5 11.0
2.4 1.2 1.1 3.4
0.4 0.5 0.9 4.8
2.3 0.6 2.0 29.0
0.000* 0.010* 0.000* 0.000*
24
G. Janson et al. / Journal of the World Federation of Orthodontists 6 (2017) 20e27
Fig. 3. Tracings generated by Dolphin Imaging 11.5 software superimposed on the sella-nasion line at sella. Superimpositions of the mean tracings of the pretreatment (black), posttreatment (red), and long-term follow-up (green) stages.
Fig. 2. Patients’ mean tracings generated by Dolphin Imaging 11.5 software superimposed on the sella-nasion line at sella. (A) and (B) are based on superimpositions of the mean tracings to illustrate treatment and posttreatment changes. (A) Superimposition of the pretreatment (black) and posttreatment (red) stages. (B) Superimposition of the posttreatment (red) and long-term follow-up (green) stages.
the posttreatment period, with changes within the normal range (Table 5). Studies that evaluated treatment of patients presenting concave facial profile, with maxillary retrusion, demonstrated similar stability success rate to the current study [4,14,17]. In contrast, studies that involved patients with Class III malocclusion with a more significant mandibular component showed relapse of treatment outcomes in the long-term [16,28,29]. Tahmina et al. [16] reported that long-term stability was demonstrated when treated patients with Class III malocclusion tended to approach the patients with normal occlusion in terms of mandibular dimensions. Corroborating what was stated in the preceding paragraph, when comparing patients who presented relapse with patients who showed long-term stability, studies demonstrated that the relapse group had, on average, a slightly larger and more anteriorly positioned mandible before treatment than the stable group [18,29,33]. Additionally, during the posttreatment period, the length of the mandibular body and the effective mandibular length had a significantly greater increase in the patients who relapsed, as well as the anterior position of the mandible [16,30]. In the present study, although no statistically significant differences were found in posttreatment changes in mandibular length (condilion-gnation) between the experimental and control groups, this variable presented a significant inverse correlation with the decrease in overjet in the posttreatment period, when the multiple regression analysis was performed (Table 6). These results confirm the influence of mandibular growth on posttreatment stability.
4.2. Dentoalveolar stability The significant increase in LAFH during treatment may have been consequent to the mechanotherapy used, associated with normal growth [4,31,32]. However, it had no significant increase in
The maxillary incisors that were labially tipped and protruded during treatment remained stable during the posttreatment period
G. Janson et al. / Journal of the World Federation of Orthodontists 6 (2017) 20e27
25
Table 4 Posttreatment changes: T3-T2 (paired t tests) Variable
Maxillary component SNA A-NPerp Co-A Mandibular component SNB Pg-NPerp Co-Gn Maxillomandibular relationship ANB Wits Vertical component FMA SNGoGn LAFH Maxillary dentoalveolar component Mx1.PP Mx1-Aperp Mx1-PP Mx6-APerp Mx6-PP Mandibular dentoalveolar component IMPA Md1-PgPerp Md1-MP Md6-PgPerp Md6-MP Dental relationships Overjet Overbite Molar relationship Objective grading system *
Posttreatment (T2)
Follow-up (T3)
Difference
P
Mean
SD
Mean
SD
82.6 2.0 85.2
4.0 4.0 4.1
82.7 2.5 87.3
3.9 3.3 5.7
0.1 0.5 2.1
0.980 0.413 0.002*
81.7 4.7 118.8
3.1 4.8 6.3
82.1 5.8 123.4
3.8 6.2 8.7
0.4 1.1 4.6
0.193 0.392 0.009*
0.9 2.7
2.2 2.2
0.6 2.7
1.9 2.4
0.3 0.0
0.223 0.990
23.8 30.2 63.3
4.6 6.3 5.0
22.9 29.5 65.2
5.1 7.0 6.0
0.9 0.7 1.9
0.190 0.061 0.052
122.8 5.9 24.0 24.5 18.0
4.1 1.7 2.0 2.1 2.2
122.6 5.8 24.9 24.3 19.5
5.4 1.7 2.3 1.6 2.5
0.2 0.1 0.9 0.2 1.5
0.819 0.610 0.023* 0.654 0.013*
86.8 12.2 39.1 37.5 29.5
8.2 5.1 2.6 4.8 2.8
89.3 12.2 39.8 37.4 30.8
9.1 5.2 3.5 5.2 3.5
2.5 0.0 0.7 0.1 1.3
0.013* 0.958 0.179 0.923 0.020*
2.4 1.2 1.1 14.8
0.4 0.5 0.9 7.3
1.7 0.7 1.8 18.7
1.0 0.8 1.4 8.9
0.7 0.5 0.7 3.8
0.004* 0.000* 0.084 0.001*
Statistically significant at P < 0.05.
(Tables 3 and 4; Figs. 2 and 3), as previously reported [12e14]. However, they had a significantly different behavior compared with normal occlusion that usually presents labial tipping of these teeth with normal growth [13] (Table 5). This may compromise the overjet in the long-term posttreatment period. The maxillary molars experienced mesialization and vertical development with treatment, probably consequent to the use of Class III elastics and growth [34,35]. Molar changes in the posttreatment period were similar to normal growth and therefore would not be a contributing factor for malocclusion relapse. The mandibular incisors were significantly retruded and extruded with treatment, probably consequent to the use of Class III elastics, and experienced significant labial tipping in the posttreatment period (Tables 3e5; Figs. 2 and 3). Class III elastics may have prevented the mandibular incisors from protruding and labially tipping during leveling and alignment in the process of decompensating the Class III malocclusion, with treatment. However, in the posttreatment period, they were significantly labially tipped, as previously reported [7,12,13]. Labial tipping is a significantly opposite change that occurs with normal growth and may be a contributing factor for overjet decrease [13] (Table 5). The mandibular molars experienced vertical development with treatment, probably consequent to normal growth [6,16]. Molar changes in the posttreatment period were similar to normal growth and therefore would not be a contributing factor for malocclusion relapse (Table 5). Overjet and overbite, which had significantly increased during treatment, significantly decreased in the posttreatment period (Tables 3 and 4; Figs. 2 and 3). These posttreatment changes were similar to normal growth (Table 5); however, both remained
positive at the long-term posttreatment stage. Molar relationship, which had significant improvement with treatment, demonstrated stability during the posttreatment period due to behavior similar to the control group (Table 5). Similar results have been previously reported [15,17,36]. According to the PAR index, the initial malocclusion severity and the treatment difficulty of the sample are considered moderate [22]. A great malocclusion severity was not expected because these patients were treated with nonextraction. More severe cases may require extraction or even orthodontic-surgical approaches [36,37]. There was significant occlusal improvement of 89.5% during treatment, which is greater than the minimum improvement of 65.0% recommended to be obtained with orthodontic treatment, showing that good treatment was provided to these patients [22]. This was also confirmed by the posttreatment Objective Grading System (OGS) of 14.8. In general, when the OGS score is greater than 30, treatment outcome is considered as failure, and when the score is less than 20 it is considered successful [25]. The discrete dentoalveolar cephalometric relapses contributed to produce a significant occlusal relapse, demonstrated by a decrease in OGS in the posttreatment period. However, the score was still less than 20 at T3 (Table 4). 4.3. Clinical stability The decrease in overjet previously mentioned demonstrates only whether the changes in these variables between T2 and T3 are mathematically significant in the experimental group and in relation to a control group. Although this parameter can be useful and understandable to the researcher, it does not show the clinician
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G. Janson et al. / Journal of the World Federation of Orthodontists 6 (2017) 20e27
Table 5 Results of t tests between changes during the long-term posttreatment period of the experimental group (T3-T2) and changes in the control group during a comparable period (t tests) Variable
Experimental group
Control group
Mean
SD
Mean
SD
1.0 2.6 3.0
0.6 0.8 3.7
0.6 1.3 3
0.290 0.638 0.258
1.1 5.5 8.7
0.6 0.9 4.0
1 3.2 5.0
0.461 0.887 0.772
1.9 1.8
0 0.7
0.9 1.6
0.373 0.201
2.7 1.5 3.8
0.4 0.5 3.4
1 1 4.4
0.471 0.605 0.267
3.5 1.3 1.6 1.8 2.3
2.6 0.5 0.8 0.8 1.9
3 0.9 1.7 1.7 2.3
0.011* 0.068 0.865 0.328 0.644
3.8 1.8 2.1 2.4 2.1
1.5 0.8 1.9 0.2 2.4
3.6 1.2 2.1 2.3 2
0.002* 0.074 0.060 0.894 0.090
0.8 0.5 1.7
0.4 0.5 0.4
0.7 1.1 0.5
0.215 0.883 0.340
Maxillary component SNA 0.1 A-NPerp 0.5 Co-A 2.1 Mandibular component SNB 0.4 Pg-NPerp 1.1 Co-Gn 4.6 Maxillomandibular relationship ANB 0.3 Wits 0.0 Vertical component FMA 0.9 SNGoGn 0.7 LAFH 1.9 Maxillary dentoalveolar component Mx1.PP 0.2 Mx1-Aperp 0.1 Mx1-PP 0.9 Mx6-APerp 0.2 Mx6-PP 1.5 Mandibular dentoalveolar component IMPA 2.5 Md1-PgPerp 0.0 Md1-MP 0.7 Md6-PgPerp 0.1 Md6-MP 1.3 Dental relationships Overjet 0.7 Overbite 0.5 Molar relationship 0.7 *
P
Statistically significant at P < 0.05.
whether the patients had a negative overjet (which is perceived by the patient and might be the reason for complaints) again at the long-term follow-up stage. It also does not represent the percentage of patients who might or might not have a negative overjet again in the long-term. For these reasons, the “clinically significant” relapse of Class III malocclusion treatment was evaluated. It was observed that only 2 (11.1%) of the 18 patients in the experimental group had a clinically significant relapse at T3. Consequently, 88.9% of the patients had a clinically significant stability of Class III malocclusion correction in the long-term. The explanation for the statistical stability of the studied variables and the high percentage of patients with significant clinical stability in the long-term, in this study, might be that individuals in the experimental group were mostly patients without an obvious mandibular involvement in the Class III discrepancy. Comparisons of follow-up variations on mandibular components between the experimental and the control groups
Table 6 Results of multiple linear regression analysis with the amount of overjet relapse in the posttreatment period (overjet T3-T2) as the dependent variable Variables
r
P
Treatment time Active retention time Overjet T1 Overjet T2-T1 Molar relationship T3-T2 Co-Gn T3-T2
0.89 0.31 0.12 0.08 0.066 0.48
0.391 0.842 0.648 0.742 0.003* 0.045*
*
Statistically significant at P < 0.05.
confirm that the patients with Class III malocclusion in the present study did not have a significant mandibular protrusion tendency; only 3 of the 18 patients reported family history of mandibular prognathism. The study performed by Ferro et al. [14], which, as in the current study, evaluated Class III comprehensive treatment stability after the end of facial growth and in which patients were also asked to use bedtime chincups when stability seemed tenuous, demonstrated very similar results, with 88.5% of patients having a positive overjet at the long-term follow-up. Other studies that evaluated treatment stability according to the change in molar relationship in addition to overjet [15] or in ANB angle [4], found smaller percentages of long-term clinical stability of 73% and 60%, respectively. However, as stated previously, neither molar relationship nor ANB angle are parameters observed by lay patients and are not common reasons for complaint. In the study conducted by Chen et al. [4], for example, even though 40% of the patients in the experimental group were classified as “unstable” based on the reduction of the ANB angle, only 10% of the patients had an edge-to-edge incisor relationship at follow-up. When orthopedic therapy is discontinued and fixed appliances installed, a bedtime chincup can be used at night. After removal of the fixed appliances, the chincup or a functional appliance should be maintained until the end of active growth [17]. Few studies reported the use of active retention after Class III treatment in growing patients [14,31,36]. Ferro et al. [14] used a bedtime chincup retention for 2 to 3 years after active treatment, and for a variable additional period (1 to 7 years) when stability seemed tenuous, as detected by reduction of the overjet in the posttreatment observation period. In the study performed by Battagel and Orton [11], a mandibular headgear was used until facial growth was presumed to be complete. Levin et al. [35] reported the use of a Function Regulator 3 of Fränkel at night for approximately 3 years after active treatment with the same appliance. All these studies showed a high percentage of stability of treatment changes. In the present study, 5 of the 18 patients were asked to use bedtime active retentions until completion of facial growth: 2 patients who were clinically and cephalometrically characterized as having an important mandibular involvement in the Class III discrepancy and 3 patients who reported family history of mandibular prognathism. Of those, the two patients who were thought to have unfavorable mandibular growth pattern remained clinically stable at long-term follow-up. Of the three patients who reported family history of mandibular prognathism, two did not comply with the use of the active retainers and correspond to the two patients who presented with significant clinical relapse. Even though one of the patients who reported family history of mandibular prognathism demonstrated long-term stability of Class III malocclusion correction after the use of active retention until completion of facial growth, we cannot imply that active retention will always overcome the genetic tendency of mandibular protrusion, especially because of the small number of individuals in this study who were asked to use active retainers. Longitudinal studies associating the facial growth pattern of the patients and their family members with the use of active retention are needed. According to the previous discussion, to achieve long-term stability of Class III malocclusion treatment, when planning treatment and retention of such patients, it is very important to analyze the individual’s growth pattern. The involvement of the maxilla and the mandible in the Class III discrepancy should be analyzed, as well as the growth pattern of close consanguineous relatives. Therefore, patients who are more likely to present excessive mandibular growth during the pubertal spurt can be identified. An active retainer and a tighter follow-up schedule to monitor the patient’s
G. Janson et al. / Journal of the World Federation of Orthodontists 6 (2017) 20e27
growth and the occlusal relationship are suggested after the end of Class III malocclusion treatment in growing patients. Furthermore, considering the difficulty of growth control, overcorrection of the dental intermaxillary discrepancy to 4 to 5 mm of overjet [28] may be necessary as an attempt to minimize the deleterious effects of posttreatment mandibular growth [13,14,28]. Because this was not a randomized controlled trial, one must bear in mind that these results apply to patients with the mentioned characteristics, treated with the described approaches. 5. Conclusions The following are the conclusions of the study: 1. The improvements in apical base relationship and in dentoalveolar relationship obtained with treatment remained stable during the posttreatment period. 2. Long-term clinical stability of Class III malocclusion treatment (overjet >0) was observed in 88.9% of the patients. 3. The amount of mandibular growth after active treatment was the major variable that determined long-term success of Class III treatment. References [1] El-Mangoury NH, Mostafa YA. Epidemiologic panorama of dental occlusion. Angle Orthod 1990;60:207e14. [2] Takada K, Petdachai S, Sakuda M. Changes in dentofacial morphology in skeletal Class III children treated by a modified maxillary protraction headgear and a chin cup: a longitudinal cephalometric appraisal. Eur J Orthod 1993;15:211e21. [3] Kim JH, Viana MA, Graber TM, Omerza FF, BeGole EA. The effectiveness of protraction face mask therapy: a meta-analysis. Am J Orthod Dentofacial Orthop 1999;115:675e85. [4] Chen L, Chen R, Yang Y, Ji G, Shen G. The effects of maxillary protraction and its long-term stabilityda clinical trial in Chinese adolescents. Eur J Orthod 2012;34:88e95. [5] Gallagher RW, Miranda F, Buschang PH. Maxillary protraction: treatment and posttreatment effects. Am J Orthod Dentofacial Orthop 1998;113:612e9. [6] Macdonald KE, Kapust AJ, Turley PK. Cephalometric changes after the correction of class III malocclusion with maxillary expansion/facemask therapy. Am J Orthod Dentofacial Orthop 1999;116:13e24. [7] Westwood PV, McNamara Jr JA, Baccetti T, Franchi L, Sarver DM. Long-term effects of Class III treatment with rapid maxillary expansion and facemask therapy followed by fixed appliances. Am J Orthod Dentofacial Orthop 2003;123:306e20. [8] Nanda RS, Nanda SK. Considerations of dentofacial growth in long-term retention and stability: is active retention needed? Am J Orthod Dentofacial Orthop 1992;101:297e302. [9] Deguchi T, Kanomi R, Ashizawa Y, Rosenstein SW. Very early face mask therapy in Class III children. Angle Orthod 1999;69:349e55. [10] Baccetti T, Franchi L, McNamara Jr JA. Treatment and posttreatment craniofacial changes after rapid maxillary expansion and facemask therapy. Am J Orthod Dentofacial Orthop 2000;118:404e13. [11] Battagel JM, Orton HS. Class III malocclusion: the post-retention findings following a non-extraction treatment approach. Eur J Orthod 1993;15:45e55. [12] Deguchi T, Kitsugi A. Stability of changes associated with chin cup treatment. Angle Orthod 1996;66:139e45. [13] Yoshida I, Ishii H, Yamaguchi N, Mizoguchi I. Maxillary protraction and chincap appliance treatment effects and long-term changes in skeletal class III patients. Angle Orthod 1999;69:543e52.
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