The European Journal of Orthodontics Advance Access originally published online on May 26, 2006
The European Journal of Orthodontics 2006 28(4):383-392; doi:10.1093/ejo/cjl008
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Evaluation of maxillary protraction and fixed appliance therapy in Class III patients
* Department of Orthodontics, Faculties of Dentistry, Ba
kent University, Turkey
** Department of Orthodontics, Faculties of Dentistry, Ankara University, Turkey
*** Growth and Development Department, Orthodontic Division, Ajman University, Al Fujirah, United Arab Emirates
Address for correspondence Professor Ufuk Toygar, Ankara Üniversitesi, Di Hekimli
i Fakültesi, Ortodonti Anabilim Dal
, 06500 Beevler-Ankara, Türkiye. E-mail: toygar{at}dentistry.ankara.edu.tr
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Summary |
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The aim of this study was to examine the dentofacial changes in Class III patients treated with fixed appliances subsequent to rapid maxillary expansion (RME) and facemask therapy. The material consisted of the cephalograms and hand-wrist films of 14 (9 girls, 5 boys) skeletal Class III and 15 (10 girls, 5 boys) untreated subjects obtained at the beginning of treatment/observation (T1), immediately after orthopaedic therapy (T2), and at the end of the observation period (T3). The mean pre-treatment/control ages were approximately 11.5 years and the observation period was 3 years (T2–T1: 1 year, T3–T2: 2 years). The cephalometric films were analysed according to the structural superimposition method of Björk. All tracings were double-digitized and the measurements were calculated by a computer program. Intragroup changes and intergroup differences were statistically analysed.
Forward movement of the maxilla (P < 0.01), backward movement and rotation of the mandible, an increase in the ANB angle (P < 0.001), lower face height and overjet (P < 0.001), a decrease of overbite, and an improvement in the sagittal lip relationship (P < 0.01) presented significant intergroup differences between T2 and T1. During the second phase of treatment (T3–T2), although not statistically significant, forward movement of the maxilla was less than in the control subjects. Overall changes during the observation period (T3–T1) revealed that correction was mainly due to favourable changes in the mandibular and dentoalveolar components of the discrepancy, while these in maxillary position were not different from the control group. The soft tissue profile improved significantly (P < 0.001) in the treatment group. Comparison with the Class I controls at the end of the observation period confirmed that some Class III characteristics still remained in the treated patients.
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Introduction |
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A Class III incisor relationship is one of the most difficult malocclusions to correct orthodontically, mainly because of the uncertainty of a satisfactory and stable outcome after growth.
There has been controversy among orthodontists regarding treatment of skeletal Class III malocclusion in growing children, since it is difficult to provide precise criteria as to whether the treatment could be completed by an orthodontic/orthopaedic approach alone or whether a subsequent surgical approach would be required after growth has ceased.
A number of clinicians consider that mandibular prognathisim has a genetic potential that cannot be altered merely by orthopaedic treatment and suggest a surgical approach (Proffit, 1986
; Kajiyama et al., 2000; McIntyre, 2004). On the other hand, successful orthopaedic treatment can prevent the problem from becoming more severe, can eliminate or reduce the need for a comprehensive surgical approach and will improve the psychosocial well being and appearance of the patient during the teenage years which are the most formative years of their lives. Regardless of treatment choice, a functional and aesthetic treatment result that is stable over the long term is the desired outcome.
Early treatment is commonly indicated for Class III malocclusions, since if left untreated they will ultimately comprise a substantial percentage of patients seeking orthognathic surgery as adults. Therapeutic regimes designed to influence facial morphology during growth include functional approaches (Fränkel and Fränkel, 1989; McNamara and Brudon, 1993), chincup therapy (Sugawara et al., 1990; Deguchi et al., 2002), extraoral traction to the mandibular dentition (Battagel and Orton, 1995), and reverse headgear or facemasks (Tanne and Sakuda, 1991; Merwin et al., 1997; Turley, 2002).
The Class III malocclusion can exhibit a variety of skeletal and dental components, including a large or protrusive mandible, retrusive maxilla, protrusive mandibular dentition, retrusive maxillary dentition and combinations of these components (Campbell, 1983; Ellis and McNamara, 1984; Guyer et al., 1986; McNamara and Brudon, 1993). Although most Class III patients have excess mandibular development, there is also some degree of maxillary deficiency. This has been reported to be sufficient to make the maxilla a significant part of the problem such that two-thirds of Class III individuals present a combination of maxillary retrusion and mandibular protrusion (Ellis and McNamara, 1984; Guyer et al., 1986).
Animal experiments have shown that sutural growth of maxilla can be stimulated by protraction forces (Nanda, 1978; Jackson et al., 1979). Therefore, maxillary protraction has been considered as the treatment of choice for the majority of subjects with a Class III malocclusion.
A number of studies have been performed documenting the initial and short-term response to maxillary expansion and protraction (Baccetti et al., 1998; Nartallo-Turley and Turley, 1998; Cha, 2003; Arman et al., 2004). A few of these have evaluated the long-term craniofacial modifications after orthopaedic correction (Shanker et al., 1996; Gallagher et al., 1998; Ngan et al., 1998; MacDonald et al., 1999; Baccetti et al., 2000; Lerpitayakun et al., 2001; Hägg et al., 2003; Westwood et al., 2003).
The aim of this study was to examine the dentofacial changes in Class III patients treated with fixed appliances following rapid maxillary expansion (RME) and maxillary protraction via facemask therapy, and to compare the treatment outcomes with an untreated control sample.
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Subjects and methods |
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The material consisted of the cephalograms and hand-wrist films of 14 subjects (9 girls, 5 boys) treated in the Department of Orthodontics, Ankara University, and 15 untreated control subjects (10 girls, 5 boys) from a previously collected longitudinal growth study. The initial radiographs (T1) were obtained before appliance insertion, the second (T2) after achieving a positive overjet and/or Class I occlusion, and the third (T3) after the removal of the fixed orthodontic appliances. The patients included in the treatment group were selected according to the following criteria:
- Skeletal Class III (ANB < 0 degrees, Wits < –2 mm), due to maxillary retrusion, or a combination of maxillary retrusion and mandibular protrusion;
- Retrusive nasomaxillary area and/or upper lip position;
- Angle Class III malocclusion with anterior crossbite;
- Normally or anteriorly directed vertical growth patterns according to S-N. MP angle (< 40 degrees) and mandibular rotation prediction criteria of Björk (Skieller et al., 1984);
- Normal or increased overbite (overbite > 1 mm);
- No congenitally missing or extracted teeth at the beginning of treatment.
The control subjects, matched according to skeletal maturation stage and chronological age, displayed Class I or Class III skeletal relationships (ANB: minimum –1.9 degrees, maximum 4.7 degrees), and normal vertical growth patterns with acceptable occlusions demonstrating no orthopaedic treatment need. The mean chronological age was approximately 11.5 years and all subjects were between PP2= and MP3cap developmental stages (Helm et al., 1971) at the beginning of the treatment/observation period. The mean chronological ages at T1, T2, and T3 and the duration of the observation periods are shown in Table 1.
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Treatment was initiated with a bonded RME appliance activated with a semi-rapid protocol (RME of 5–7 days, followed by slow maxillary expansion) until the desired expansion was achieved (
eri and Özsoy, 2004). Protraction elastics delivering a force of 400–600 g per side were attached near the maxillary canines with a downward and forward pull of 20–30 degrees to the occlusal plane. At this first orthopaedic phase of treatment, the patients were instructed to wear their facemasks at least 14 hours per day until a positive overjet was achieved (T2–T1: 1.1 years). In 11 patients the overjet was overcorrected to more than 2.5 mm. Following the maxillary protraction phase, a second phase of orthodontic treatment with edgewise appliances was used for final detailing of the occlusion (T3–T2: 1.8 years). The patients were treated without extractions and all used Class III elastics and facemasks or chincups during the fixed appliance phase. As the patients were still in their active growth period at the end of the treatment period, some of them continued to wear their chincups in addition to their intraoral appliances for retention and control of late mandibular growth.
Cephalometric analysis
The cephalometric records were obtained under standardized conditions. The cephalograms were traced and the reference points were marked (Figure 1). Horizontal (HR) and vertical reference (VR) planes were transferred from the T1 tracing to the T2 and T3 tracings according to the structural superimposition method (Björk and Skieller, 1983). The second (T2) and third (T3) films were superimposed on the first and were orientated to obtain maximal coincidence of the anatomic reference structures. These reference structures were (1) The contours of the anterior wall of sella turcica, (2) the anterior contours of the median cranial fossa, (3) the intersection of the anterior contour of sella and tuberculum sella, (4) the inner surface of the frontal bone, (5) the contours of the ciribriform plate, (6) the contours of the bilateral frontoethmoidal crests, and (7) the contour of the median border of the cerebral surfaces of the orbital roofs. Control of the superimposition was made by checking the changes of the frontoparietal suture, occipital bone, and points articulare and pterygomaxillare.
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VR was constructed perpendicular to the occlusal plane of the first tracing (OP1) from point sella (S1) of the first tracing (T1) and HR was drawn perpendicular to VR from S1. The co-ordinates of the reference landmarks were recorded using a Hipad Digitiser (Houston Instruments, Houston Texas, USA) with a resolution of 0.125 mm and with a double-digitizing procedure. The PorDios (Purpose on request Digitizer input–output system, Institute of Orthodontic Computer Science, Århus, Denmark) cephalometric analysis program was used to perform the calculations.
Statistical method
Paired t-tests were used to analyse changes within the groups and independent t-tests to compare treatment changes with the control group.
Method error
All measurement calculations (landmark identification, superimposition, and digitization) for the 15 subjects were carried out by the same investigator 1 month after the first measurements were made. Intraclass correlation coefficients were found to be within 0.92–0.99 and the method was found to yield sufficient reliability.
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Results |
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The craniofacial morphology of all subjects and the statistical evaluation of intergroup differences at T1, T2, and T3 are shown in Table 2. The changes in measurements, statistical analysis of intra- and intergroup differences from T1 to T2 are shown in Table 3, and the mean changes from T2 to T3 in Table 4. Evaluation of overall treatment/control changes (T1–T3) are presented in Table 5.
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Skeletal measurements
The midface length (Cd-A), sagittal position of point A (A-VR), effective mandibular length (Cd-Gn), mandibular prognathism (SNB), gonial angle, intermaxillary relationship [(ANB, (A-VR)-(B-VR)], and facial convexity angle (N.A.Pg) was significantly different between the groups at T1 (Table 2).
Throughout the maxillary protraction phase, the increase in lower anterior face height (ANA-Me) was more pronounced in the treatment group than in the controls (Table 3). The maxilla displaced anteriorly (SNA, A-VR), the midface length (Cd-A) increased significantly in the treatment group, and the increase in SNA angle was statistically different from the controls. The mandible was positioned backward (SNB, B-VR) significantly in the treatment group, and change in the SNB angle was statistically different from the controls (Table 3). Posterior rotation of the mandible (S-N.MP) was significant in the treatment group. The intermaxillary relationship improved significantly with a concomitant increase in the facial convexity angle in the treatment group (Table 3).
In the post-protraction period (T3–T2), an increase in SNB angle was observed in the control group which was different from the treatment group (Table 4).
During the overall observation period (T1–T3) the increase in anterior face heights (N-Me, ANS-Me) was more significant in the treatment group (Table 5). The midface length (Cd-A) increased and the maxilla moved forward (SNA, A-VR) similarly in both groups. The changes in the position (SNB, B-VR) and rotation of the mandible (S-N.MP) showed significant intergroup differences. Both the ANB angle (2.32 degrees) and modified Wits appraisal [(A-VR)-(B-VR), 2.27 mm] increased significantly in the treatment group compared with the controls (Table 5).
Final evaluation of the skeletal parameters at T3 revealed that anterior face heights, sagittal position of point A, effective mandibular length, mandibular rotation according to HR (HR.MP), gonial angle, intermaxillary relationship, and facial convexity still significantly differed from the control group (Table 2).
Dentoalveolar measurements
Significant intergroup differences for overjet and lower incisor inclination (L1.NB) were found at T1 (Table 2).
The significant outcomes of RME and maxillary protraction therapy (T1–T2) were an increase in overjet (6.11 mm) and a decrease in overbite (Table 3). The proclination of the upper incisors (U1.NA) and retrusion of the mandibular incisors (L1.NB) in the treatment group were significantly different from the controls. The decrease in the occlusal plane angle (S-N.OP) was significant in the treatment group (Table 3).
In the post-protraction phase of treatment the dentoalveolar outcomes achieved in the first phase were maintained (Table 4). The control group demonstrated significant changes, whereas no significant difference was observed in the treatment group regarding the dentoalveolar parameters during the second phase of treatment.
For the overall observation period, overjet increased (6.21 mm), and upper incisors showed significant protrusion (U1i-NA), differing from the controls (Table 5).
At the end of the observation period (T3), overbite, upper incisor inclination (U1.NA), and lower incisor inclination (L1.NB) all showed significant differences between the groups (Table 2).
Soft tissue measurements
The soft tissue convexity angle (Ns.Sn.Pgs), upper lip position from E-line (UL-E), and sagittal lip relationship (UL-VR)-(Ll-VR) all showed intergroup differences at the start of the observation period (T1; Table 2).
Soft tissue convexity increased, and the sagittal lip relationship significantly improved due to orthopaedic therapy (T1–T2) and showed significant intergroup differences (Table 3).
In the post-protraction phase (T3–T2), no statistical difference was found regarding the soft tissue changes between the treatment and control groups (Table 4).
During the overall treatment period, soft tissue total and lower face heights (Ns-Mes, Sn-Mes) and convexity (Ns.Sn.Pgs) increased more than in the control group (Table 5). The sagittal lip relationship [(UL-VR)-(LL-VR)] improved significantly in the treatment group (2.66 mm), showing difference between groups (P < 0.01).
Anterior soft tissue height, soft tissue convexity angle, sagittal upper lip position according to E-line, and sagittal lip relationship presented intergroup differences at the end of the observation period (T3; Table 2).
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Discussion |
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TopSummaryIntroductionSubjects and methodsResultsDiscussionConclusionsReferences |
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The major intent of this clinical study was to evaluate the dentofacial changes induced by RME and facemask therapy after a second phase of fixed appliance therapy by comparing the overall changes with a control group. Well-designed clinical studies using control groups in order to distinguish treatment effects from normal growth and development as well as investigations comparing the effects of different therapeutic approaches in Class III malocclusions are essential (Battagel and Orton, 1995
; Üçüncü et al., 2000; Arman et al., 2004). However, clinical trials present inevitable limitations, such as individual variations in severity of malocclusion, growth patterns, treatment protocols, patient co-operation, treatment response, and relapse potentials.
The untreated control group in the present study was closely matched for gender, chronological/skeletal age, and observation intervals. The longitudinal control material comprised subjects with acceptable occlusions and mostly skeletal Class I relationships, thus statistical differences in some of the parameters between the Class III patients and control group were noted at T1 (Table 2). Using a Class I control sample it was possible to demonstrate how much the treatment outcomes reached the normal. As reported by Shanker et al. (1996), MacDonald et al. (1999), and Westwood et al. (2003) a Class III control group can be advantageous, however, these Class III control samples were mostly cross-sectional rather than longitudinal. On the other hand, it has been demonstrated that the magnitude of increase in maxillary and mandibular growth is not significantly different between skeletal Class I and III (Deguchi et al., 2002).
The patients in the treatment group had a mean age of 11.5 years and all were at the pre-pubertal/pubertal stage of growth at T1. It has been recommended that maxillary protraction be initiated at earlier ages (Campbell, 1983; McNamara and Brudon, 1993; Baccetti et al., 1998; Lertpitayakun et al., 2001), whereas studies comparing the effects of maxillary protraction applied in different age groups report similar skeletal response in pre-pubertal and pubertal growth peak groups (Merwin et al., 1997; Yüksel et al., 2001; Turley, 2002).
Patient selection is extremely important for this treatment approach. The mandibular plane angle has been found to be an important factor in influencing the long-term success of RME therapy (Baccetti et al., 2004). Only, patients presenting with normally directed vertical growth patterns with positive overbite values were included in the present study sample.
In addition to conventional measurements, those from reference planes constructed according to the occlusal plane on the T1 tracing and transferred to the T2 and T3 tracings according to the structural superimposition method were used. The structural superimposition method should be preferred when evaluating long-term changes. Measurements that use S-N as a reference line are inherently inaccurate as these landmarks vary with growth (Arat et al., 2003).
Assessment of the results demonstrates that considerable facial changes and improvements took place after one year of RME and maxillary protraction treatment. The forward movement of the maxilla (2.11 mm) was accompanied by labial movement of the maxillary incisors, an increase in the vertical measurements and mandibular plane angle, and posterior movement of the mandible. These findings are in accordance with previous studies (Shanker et al., 1996; Merwin et al., 1997; Gallagher et al., 1998; Ngan et al., 1998; MacDonald et al., 1999; Baccetti et al., 2000; Yüksel et al., 2001; Westwood et al., 2003).
Correction of the Class III relationship in the treatment group was achieved by both skeletal and dental changes. The soft tissue profile reflected the favourable skeletal and dental changes. After the orthopaedic phase of treatment (T2) the differences between the treatment and Class I control group were reduced and the groups were more similar at this stage compared with T1 (Table 2).
In the fixed appliance phase of the treatment (T3–T2), the increases in face height and backward movement of the mandible (B-VR) were different from the control group (Table 4), where significant anterior rotation of the mandible was observed. Although the treatment and control groups did not demonstrate any statistical difference regarding the maxillary and maxillomandibular changes [A-VR, SNA, (A-VR)-(B-VR)], the mean differences in these measurements were likely to be clinically significant and forward movement of the maxilla was evident and more pronounced in the control subjects in this second phase treatment (Table 4). The reason for this statistical insignificance may be the small number of subjects in the study group. Following facemask therapy, the maxilla continued to grow forward but this growth was less than the maxillary growth of the control subjects. This change can be attributed to a return of the previously existing growth pattern. Studies evaluating post-protraction changes report similar skeletal changes in treated and untreated subjects (Shanker et al., 1996; Gallagher et al., 1998; Ngan et al., 1998; Baccetti et al., 2000; Westwood et al., 2003). MacDonald et al. (1999) demonstrated less maxillary anterior growth compared with a Class I control group but similar growth to a Class III control group during the post-protraction phase.
Overall changes during the observation period (T3–T1) reveal that orthopaedic and orthodontic intervention in leads to significant skeletal, dentoalveolar, and soft tissue improvements. The correction was mainly due to favourable changes in the mandibular and dentoalveolar components of the discrepancy, while changes in the maxillary position were non contributory. These findings are consistent with other studies presenting similar maxillary changes in treatment and control groups in the long term (MacDonald et al., 1999; Lerpitayakun et al., 2001; Westwood et al., 2003).
Comparison with untreated Class I controls at the end of the observation period confirmed that, despite that acceptable occlusion and appearance achieved, Class III characteristics still remained in the treated patients. Differences between the groups at this final stage were more pronounced compared with those at the end of the protraction phase, implying that skeletal improvements can be obtained during the orthopaedic phase of treatment, and mostly dental components can be maintained at the end of the treatment.
These results have important clinical implications. Treating patients with overcorrection at the orthopaedic phase may be worthwhile (Gallagher et al., 1998; Westwood et al., 2003). Prolonged use of a facemask or chincup together with Class III elastics can also be advisable to control the unfavourable skeletal growth pattern. A large part of the Class III correction was caused by protrusion of the upper incisors, uprighting of the lower incisors, and posterior rotation of the mandible during treatment. Changing the anchorage region of maxillary protraction using rigid skeletal anchorage via implants may be advisable to increase the maxillary skeletal effects and reduce the undesired dentoalveolar effects of facemask therapy (Singer et al., 2000; Enacar et al., 2003).
This study evaluated the immediate orthopaedic effects and post-treatment outcomes of RME and maxillary protraction therapy during a three-year period. Significant relapse potentials of skeletal and dentoalveolar variables have been reported in studies of long-term effects of maxillary protraction appliances (Gallagher et al., 1998; Ngan et al., 1998; Hägg et al., 2003). Hägg et al. (2003) reported a success rate of 67 per cent in a patient sample 8 years after active treatment with reverse headgear. Consequently, records at the time when facial growth is close to completion or complete should be evaluated for stability of these treatment changes.
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Conclusions |
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TopSummaryIntroductionSubjects and methodsResultsDiscussionConclusionsReferences |
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Class III patients and Class I control subjects presented significant differences at the beginning of the observation period.
RME plus maxillary protraction therapy produced significant dentofacial changes from T2 to T1. Forward movement of the maxilla, backward movement and rotation of the mandible, improvement of the maxillomandibular relationship, an increase in lower face height and overjet, a decrease of overbite, and improvement of the sagittal lip relationship were significantly different from the control group.
At the end of the orthopaedic therapy, the treatment and control groups were more similar compared with T1.
In the fixed appliance phase of treatment (T3–T2), increases in face height and backward movement of the mandible were different from the control group. Significant anterior rotation of the mandible was observed in the control group. Although not statistically significant, forward movement of the maxilla after facemask therapy was less than in the controls.
Changes during the overall observation period (T3–T1) indicated no significant difference between the groups regarding maxillary changes, while backward movement and rotation of the mandible was significant and different from the controls. The overjet increased, the maxillary incisors protruded, and the lip relationship improved significantly in the treatment group.
Final evaluation at T3 revealed a more orthognathic profile after treatment. However, the treated patients still presented Class III characteristics.
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Acknowledgement |
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We wish to thank Dr Ensar Baspinar (Ankara University, Faculty of Agriculture, Department of Genetics and Statistics) for managing the statistical procedures used in this study.
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References |
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