Orthopedic Treatment Outcomes in Class III MalocclusionA Systematic Review
Objective: To assess the scientific evidence on the effectiveness of early orthopedic treatment in Class III subjects.
Materials and Methods: A literature survey was performed by applying the Medline database (Entrez PubMed). The survey covered the period from January 1966 to December 2005 and used the Medical Subject Headings (MeSH). The following study types that reported data on the effects of Class III treatment with orthopedic appliances (facial mask, chincup, FR-3) on intermaxillary sagittal and vertical relationships were included: randomized clinical trials (RCTs), and prospective and retrospective longitudinal controlled clinical trials (CCTs) with untreated Class III controls.
Results: The search strategy resulted in 536 articles. After selection according to criteria for inclusion and exclusion, 19 articles qualified for the final review analysis. One RCT and 18 CCTs were retrieved.
Conclusion: The quality standard of the retrieved investigations ranged from low (four studies) to medium/high (five studies). Data derived from medium/high quality research described over 75% of success of orthopedic treatment of Class III malocclusion (RME and facial mask therapy) at a follow-up observation 5 years after the end of orthopedic treatment.Abstract
INTRODUCTION
Class III malocclusion is associated with a deviation in the sagittal relationship of the maxilla and the mandible, characterized by a deficiency and/or a backward position of the maxilla, or by prognathism and/or forward position of the mandible.1 The incidence of this malocclusion in the white population has been reported to be 1% to 5%.2–4 In the Asian populations, however, the incidence ranges from 9% to 19%,5–7 and in Latin populations the incidence is approximately 5%.89
The etiology of Class III malocclusion is multifactoral because of an interaction of both hereditary and environmental factors. The contributions of the cranial base, maxilla, mandible, and temporomandibular articulation have been described in detail in the literature.10–13 Class III malocclusions associated with craniofacial disharmonies are much more difficult to treat and tend to relapse.14–16
Early treatment of Class III malocclusion has been advocated to reduce the need of treatment in the permanent dentition, when camouflage orthodontic treatment or surgery become the only options.1 A series of treatment approaches can be found in the literature regarding orthopedic treatment in Class III malocclusion.
The aim of the present study is to analyze the scientific evidence on the actual outcomes of orthopedic treatment in Class III malocclusion as derived from the existing literature on peer-reviewed orthodontic journals according to the Cochrane collaboration principles. This systematic review was undertaken to answer the following relevant questions:
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Is early orthopedic treatment of Class III malocclusion effective?
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Which treatment modality is the most effective?
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Are treatment results stable at a posttreatment observation?
MATERIALS AND METHODS
Search Strategy
The strategy for performing this systematic review was influenced mainly by the National Health Service (NHS) Centre for Reviews and Dissemination.17 To identify all the studies that examined the relationship between early orthopedic treatment and Class III malocclusion, a literature survey was done by applying the Medline database (Entrez PubMed, www.ncbi.nim.nih.gov). The survey covered the period from January 1966 to December 2005 and used the Medical Subject Heading (MeSH) terms: “malocclusion and Angle Class III,” which was crossed with MeSH terms “orthodontics, interceptive” and “orthodontics, corrective” (Table 1). In addition, a search in the Cochrane Controlled Clinical Trials Register was performed.
Selection Criteria
The inclusion and exclusion criteria are given in detail in Table 2. The following study types that reported data on the treatment effects were included: meta-analysis randomized clinical trials (RCTs) and prospective and retrospective studies with concurrent untreated control groups (CCTs). The retrieved studies had to use cephalometrics to analyze the effects of orthopedic therapy on total mandibular length, total maxillary length, and intermaxillary vertical and sagittal relationship with respect to untreated Class III controls. No restrictions were set for sample size. Laboratory studies, descriptive studies, case reports, case series, reviews, and opinion articles were excluded.
Data Collection and Analysis
According to the recommendations by Petrèn et al,18 data were collected on the following items: year of publication, sample size, study design (meta-analysis, RCT, CCT), treatment duration, observation time, success rate, side effects, and authors' conclusion. In addition, to document the methodological soundness of each article, a quality evaluation modified from the methods described by Antczak et al19 and Jadad et al20 was performed with respect to preestablished characteristics. The following characteristics were used: study design, posttreatment evaluation, sample size and previous estimate of sample size, selection description, withdrawals (dropouts), method error analysis, blinding in measurements, and adequacy of statistics. The following systematic scores were assigned to individual retrieved articles:
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Adequacy of selection description: 2 points
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Study design (RCTs: 2 points, CCTs: 1 point)
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Posttreatment evaluation (No: 0 point; Yes: 2 points)
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Description of method error analysis (2 points)
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Adequacy of statistics (nonparametric tests used when appropriate: 2 points; parametric tests used when nonparametric tests would be more appropriate: 1 point)
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Blinding in measurements (1 point).
The quality of the studies was considered as follows:
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Low: with a total score ≤5 points
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Medium: with a total score >5 and ≤7 points
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Medium/high: with a total score >7 and ≤9 points
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High: with a total score ≥10 points.
Two independent reviewers (LDT, CP) assessed the articles separately. The data were extracted from each article without blinding to the authors, and interexaminer conflicts were resolved by discussion of each article to reach a consensus. Two independent reviewers performed the quality evaluation of the articles retrieved (LF and PC) with one author (TB) acting as the coordinator.
RESULTS
The search strategy resulted in 536 articles. After selection according to the inclusion/exclusion criteria stated in Table 2, Table 3 articles qualified for the review analysis.21–39 The main reasons for exclusion were: case reports, reviews, opinion articles, studies concerning treatment in permanent dentition/adult patients, and studies about association between Class III malocclusion and malformation. Six of the studies were performed in the United States,212425303439 five in Japan,2829313337 four in Turkey,22263238 two in the UK,2327 one in Korea,35 and one in Italy.36
Study Design and Treatment Modalities
The results of the review are summarized in Tables 3 and 4. No meta-analyses were found. The 19 articles included one RCT39 and 18 retrospective CCTs.21–38
Three articles described the effects of chincup alone2729 or in association with fixed appliances.33 Seven studies utilized a facemask alone23242628323839; four articles described the orthopedic effect of a facemask in association with rapid maxillary expanders,21253039 and one in combination with fixed appliances34; one article described the effects of the facemask in combination with a Bionator III.36 Two articles analyzed the effects of the FR-3 appliance of Fränkel,2235 two of a maxillary protractor bow appliance (MPBA),3137 one of double-plate appliance (DPA),38 and one utilized a combination of an upper removable appliance in association with an extraoral traction to the mandibular dentition (EOT).23
Age of Groups
Treated Class III patients were 4 years 2 months28 to 12 years 4 months23 old, whereas the age range in untreated groups was wider, as it varied from 4 years 2 months28 to 17 years 11 months.33
Treatment Duration and Class III Skeletal Correction
Treatment duration varied between 5 years 2 months37 and 7 years 2 months,33 depending upon treatment modalities. Twelve studies declared that treatment was discontinued after the correction of Class III malocclusion. Of these studies, six studies interrupted active treatment after achieving a positive overjet,242627283137 one study after obtaining a Class I molar relationship,32 and four after achieving both goals.32343839
Success Rate
A 100% success rate was reported in five studies,2126323335 85% in one study,28 and a 76% rate in another study.34 The other articles did not declare the success rate.
Correlation Between Gender and Treatment Outcomes
Only three studies233137 analyzed the influence of gender on treatment outcomes. In two studies3137 no significant differences between genders were found, suggesting that gender had little influence on treatment effects. In one study23 values for each sex were given separately, as statistically significant differences were found, even if the composition of the groups with regard to severity of malocclusion and age was more difficult to manage. Three studies223539 combined the sexes because statistical significance was not found between them.
Correlation Between Timing and Treatment Outcomes
Only one study26 declared the skeletal age of subjects at the beginning of treatment, but omitted the method used to evaluate it. One study34 considered only subjects that attained a skeletal maturity staging Cvs4, Cvs5, or Cvs6 at a long-term observation, considering the developmental staging of the cervical vertebrae proposed by Franchi et al.40
Other studies25272830313537 considered the dental stage at the beginning of treatment, varying from primary dentition,283537 eruption stage of first molars and incisors,25273035 completed eruption of molars and incisors,3137 and eruption stage of canines and/or premolars.2530
Treatment in deciduous dentition produces greater skeletal changes than those produced in the mixed dentition stage37; moreover, when therapy begins in the early mixed dentition, it seems to induce more favorable changes in the craniofacial skeleton, compared with the same treatment started in the late mixed dentition.2530
One study compared treatment outcomes in two different chronologic age groups32 without finding any significant difference in the orthodontic and orthopedic effects.
Side Effects
Ten articles* considered the modifications in the inclination of the upper and lower incisors as a dental compensation during skeletal movement. In all these articles a retrusion and linguoversion of the mandibular incisors, a protrusion and labioversion of the maxillary incisors, or a combination of these two dental movements was found. Three articles did not report changes in the inclination of the incisors.253033 No studies performed a cost-analysis.
Stability of Treatment Outcomes
Six studies gave information about the stability of treatment,242728303334 reporting cephalometric results at a posttreatment observation.
One study30 included a later cephalometric observation at about 1 year from the end of active treatment. This study reported that relapse tendency in early treatment subjects primarily affected the maxillary region, whereas late treatment subjects exhibited a significant rebound in mandibular sagittal position.
Three studies included a cephalometric observation about 3 years from the end of active orthopedic treatment242728: two of these2428 reported a lack of significant differences between treated and control groups, suggesting that the favorable treatment effects on the maxillomandibular relationship were maintained. However, the treatment effect of increased overjet was diminished, mainly due to proclination of the mandibular incisors. Successfully treated cases demonstrated a significantly greater change in overjet during treatment, suggesting that some overcorrection may be necessary for maintenance of a successful correction. One study27 reported no statistically significant skeletal or soft-tissue differences between the groups at the end of posttreatment observation, except for the increased overjet and overbite in the chincap subjects.
Two articles3334 evaluated the posttreatment effects of an initial phase of orthopedic treatment followed by comprehensive edgewise therapy, with a follow-up observation at about 5 years from the end of orthopedic treatment. Favorable skeletal change observed post treatment was due almost entirely to the orthopedic correction: during the posttreatment period, craniofacial growth in treated subjects was similar to that of untreated class III controls. Thus, aggressive overcorrection at a skeletal level appears to be advisable and essential to the stability of the treatment outcome.34
Quality Analysis
Research quality was low in four studies,26293137 medium in 10 studies,† and medium/high in five.2427303439 The selection description was adequate in all studies. Withdrawals (dropouts) were declared only in the RCT study,39 and in this study the number of dropouts was three. Nine articles used proper statistical methods22–24253032343638; in the remaining studies the choice of a parametric test without data distribution analysis was inadequate. Thirteen studies included a method error analysis,‡ and only one article used blinding in measurements.39 No study declared the presence of ethical approval with regard to the employment of an untreated control group with a Class III malocclusion. No article declared a previous estimate of sample size.
DISCUSSION
In this systematic review, an exhaustive literature search attempted to find all randomized and controlled clinical trials with concurrent untreated controls that compared different treatment modalities for orthopedic treatment in Class III malocclusion.
RCTs have been used rarely in orthodontics, and this systematic review shows that only one RCT on the outcomes of orthopedic Class III therapy was found.39 In fact, several items required in quality reviews are applicable scarcely in orthodontics (ie, patients blinded or observer blinded to treatment). Another reason can be defined as “ethical” or “logistic” because RCT patients are not able to choose treatment, and some subjects may be designated to an untreated control group (in which the treatment is postponed after the study period), and these subjects may refuse to participate in the trial.
For these reasons both retrospective and prospective CCTs were included in this review. In most of the studies, there were serious shortcomings, such as no previous estimate of sample size, or no discussion on the possibility of type II error occurring. Problems of bias, lack of method error analysis, lack of blinding in measurements, and deficient or lack of statistical methods were other examples of drawbacks in most of the studies. Withdrawals (dropouts) were well declared in only one study.
The groups of Class III subjects analyzed in the articles retrieved for this review were considered very heterogenic with regard to age (especially in untreated control groups), to treatment modality, and to treatment duration. Cephalometric measurements performed in the 19 studies were not comparable because different studies used different cephalometric analyses (for instance, not all studies used ANB angle to evaluate the skeletal sagittal relationship). Moreover, those studies that used the same cephalometric analysis did not apply the same treatment timing, or they did not show the same treatment duration, thus rendering quantitative analysis of outcomes practically impossible and clinically useless.
With regard to the quality standard of the retrieved investigations, it ranged from low (four studies26293137) to medium/high (five studies2427303439). The only RCT39 analyzed a very specific aspect of orthopedic treatment of Class III malocclusion (use of rapid maxillary expansion [RME] in combination with a facial mask vs no use of the RME), and the reported results were in the short term. Therefore, even in the presence of data derived from medium/high quality research34 that described over 76% of success of orthopedic treatment of Class III malocclusion (RME and facial mask therapy) at a follow-up observation 5 years after the end of orthopedic treatment, high quality investigations are still needed to perform a definitive assessment of effectiveness of Class III treatment at the skeletal level. An RCT on the effects of different orthopedic treatment modalities with a long-term observation at the end craniofacial growth would be desirable.
Contributor Notes
Corresponding author: Tiziano Baccetti, DDS, PhD, Università degli Studi di Firenze, Via del Ponte di Mezzo, 46-48, 50127, Firenze, Italy (t.baccetti@odonto.unifi.it)