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Prediction of the outcome of orthodontic treatment of Class III malocclusions—a systematic review

Piotr Fudalej, Magdalena Dragan, Barbara Wedrychowska-Szulc
DOI: http://dx.doi.org/10.1093/ejo/cjq052 190-197 First published online: 22 July 2010

Abstract

The purpose of this study was to systematically review the orthodontic literature to assess the effectiveness of a prediction of outcome of orthodontic treatment in subjects with a Class III malocclusion. A structured search of electronic databases, as well as hand searching, retrieved 232 publications concerning the topic. Following application of inclusion and exclusion criteria, 14 studies remained. Among other data, sample ethnicity, treatment method, age at the start and completion of treatment, age at follow-up, outcome measures, and identified predictors were extracted from the relevant studies. A subjective assessment of study quality was performed.

The heterogeneity of the samples and treatment methods prevented carrying out a meta-analysis. Thirty-eight different predictors of treatment outcome were identified: 35 cephalometric and three derived from analysis of study casts. Prediction models comprising three to four predictors were reported in most studies. However, only two shared more than one predictor. Gonial angle was identified most frequently—in five publications. The studies were of low or medium quality.

Due to the large variety of predictors and differences among developed prediction models, the existence of a universal predictor of outcome of treatment of Class III malocclusions is questionable.

Introduction

Treatment of children with a Class III malocclusion represents a challenge in orthodontics because unsuccessful outcome of orthodontic/orthopaedic therapy is relatively frequent (Westwood et al., 2003; Baik, 2007). Despite elimination of the reverse overjet and achievement of an acceptable dental arch relationship during early intervention, relapse is observed irrespective of the treatment modality (Franchi et al., 1997; Tahmina et al., 2000) and at different ages (Battagel, 1993; Franchi et al., 1997). Deterioration of occlusion was found in Class III patients of different ethnicity (Ngan et al., 1997; Westwood et al., 2003) and the incidence of relapse has been reported to be almost 50 per cent (Franchi et al., 1997).

The ability of early classification to either an orthodontic or surgery group would allow efficient triage according to patient treatment need. Subjects, who could be successfully treated with orthodontic/orthopaedic appliances, could receive treatment during childhood or adolescence, while the treatment plan of individuals who eventually would need orthognathic surgery could be modified accordingly. Battagel (1993) was one of the first investigators who recognized a need for a model of prediction of long-term outcome of orthodontic treatment of a Class III malocclusion. She employed discriminant function analysis to identify predictors of relapse in a group of children treated with cervical headgear applied to the mandibular dentition. Battagel (1993) developed a four-variable discriminant model, capable of predicting relapse with high accuracy. Franchi et al. (1997) published a study in which a three-variable predictive model was established. However, the predictors identified by Battagel (1993) and Franchi et al. (1997) differed substantially. Several other studies (Tahmina et al., 2000; Zentner and Doll, 2001; Zentner et al., 2001) dealing with identification of predictors of the results of Class III treatment have been published. Tahmina et al. (2000) examined a sample of Asians treated with a chincup, whereas subjects treated with various methods were evaluated in two, possibly related, studies by Zentner and Doll (2001) and Zentner et al. (2001). The predictive variables identified by those authors mostly differed. Although various modalities, treatment timing, or ethnicity might have affected the findings of the above-mentioned studies, the variety of prediction models established raises doubts as to whether identification of reliable predictors is possible. Therefore, the objective of this study was to systematically review the orthodontic literature to assess the possibility of the reliable prediction of orthodontic treatment outcome in subjects with a Class III malocclusion.

Material and methods

Search strategy

PubMed, Embase, Cochrane Central Register of Controlled Trials, and Lilacs were searched to the first week of October 2008 using the strategy presented in Table 1. Based on the data from titles and abstracts of the retrieved studies, the following were included: growing patients, subjects treated orthodontically/orthopaedically and articles in English, Polish, Russian, or Spanish. The exclusion criteria were a pseudo-Class III, adults, patients treated surgically, untreated subjects, case or case series reports, review and summary articles, and an observation time shorter than 3 years.

View this table:
Table 1

Search strategy and number of studies found.

Search termNumber of studies
PubMedEmbaseCochrane CentralLilacs
#1 (Malocclusion Angle Class III) OR ((Class III) AND (Angle OR malocclusion OR bite)) OR prognathism4706403165108
#2 Predict* OR Prognosis OR Long-term OR (long term)1 428 228851 97437 3849882
#3 Surg* OR Osteotomy OR Setback1 749 1952 315 96040454 210
#1 AND #2 NOT #321212531

Consensus concerning inclusion/exclusion was undertaken by two authors (PF and MD). The reference lists of these articles were perused and references to related articles were followed-up. Additionally, two orthodontic journals that publish online ahead of print, the European Journal of Orthodontics and Angle Orthodontist, were hand searched to identify such articles.

Data extraction and quality assessment

The following data were extracted from each study: sample size, gender proportion, ethnicity, treatment method, age at the beginning and completion of treatment, age at follow-up, outcome measures, type of outcome at follow-up, proportion of successful/(uncertain)/relapsed cases, type of statistical analysis used to identify predictors of treatment outcome, and identified predictors (Table 2). The heterogeneity of the samples and treatment methods made it impossible to carry out a meta-analysis.

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Table 2

Characteristics of studies included in this review.

StudySample size, gender, and ethnicityTreatment method, extractions (yes, no, nd)Age at treatment start, completion, and follow-upLength of treatment and follow-upVariable(s) used to evaluate outcomeType of outcome at follow-upSuccess/(uncertain)/relapse rate (%)StatisticsPredictors of success/relapse
Baccetti et al. (2004)42 (20 M, 22 F), CaucasiansRME + FM; no8.6, 9.6, 15.01.0, 5.4OJ < 0 mm, Class III molars -> relapseSuccess, relapse71.4/28.6DFAMandibular ramus length (Co–Goi), Ba–T–SBL angle, and MP/SBL angle
Battagel (1993)34 (21 M, 13 F), Caucasians?Mn CHG; no12.4, nd, 20.0nd, 5.6OJ, OB > 0 mm -> success; OJ, OB < 0 mm -> relapse; OJ, OB = 0 mm -> uncertainSuccess, uncertain, relapse35.3/26.5/38.2DFAU1/PP angle, Labrale superior to soft tissue nasion, Labrale inferior to Sella vertical, number of anterior teeth in crossbite*
Ferro et al. (2003)52 (22 M, 30 F), CaucasiansSplints + elastics + CC (SEC III); nd9.0, 13.0, 22.04.0, 9.0OJ < or = 0 mm -> relapseSuccess, relapse88.5/11.5t-testWits, ANB, SNB, and OB at the end of tx
Franchi et al. (1997)45 (22 M, 23 F), Caucasians?FA; nd5.6, nd, 15.8nd, 6.6Angle Class, anterior crossbite (concomitant molar and canine Class III and anterior crossbite of at least 1 incisor -> relapse)Success, relapse51.1/48.9DFAAxis of condylar process to SBL angle (CondAx–SBL), mandibular plane to palatal plane (MP/PP), and mandibular intermolar width
Ghiz et al. (2005)64 (29 M, 35 F), 53% Caucasians, 47% AsiansFM; nd9.2, nd, ndnd, ndOJ > 1 mm and angle Class I -> successSuccess, relapse68.8/31.2Regression analysisPosition of the condyle with reference to the cranial base (Co–GD), mandibular ramus length (Co–Goi), total mandibular length (Co–Pg), and gonial angle (Ar–Goi–Me)
Ko et al. (2004)40 (18 M, 22 F), Asians?CC + fixed; Mixed8.2, 11.1, 17.61.9, 6.5Good facial profile, OJ and OB > 0 mm, Class I molars and canines without severe facial and dental asymmetry -> successSuccess, relapse52.5/47.5t-testL1/OcclPl, upper gonial angle, AB/OcclPl, AB/MP, ANB, APDI, Wits, Articular angle (S–Ar–Go), gonial angle, facial convexity, AB/facial plane, and L1/A–Pog
Moon et al. (2005)45 (16 M, 29 F), AsiansCC; nd8.6, 11.7, 17.43.1, 5.7OJ > 2mm, OB > 1.5 mm -> success; OJ, OB < 0 mm -> relapse; intermediate values of OJ and OB -> uncertainSuccess, uncertain, relapse37.8/28.9/33.3DFAAB/MP angle; A to N-perp distance
Ngan and Wei (2004)40 (21 M, 19 F), 38% Caucasians, 62% AsiansRME +FM; no8.9, 9.8, 13.00.9, minimum 3 yearsOJ > 1 mm -> successSuccess, relapse50.0/50.0t-testGrowth treatment response vector established based on initial, post-treatment, and follow-up cephalograms
Schuster et al. (2003)88 (39 M, 49 F), CaucasiansVarious; nd9.8, nd, 17.4nd, ndNeed for surgery at the end of observation periodSuccess, relapse73.9/26.1Regression analysis, DFAWits, palatal plane to SN angle (PP/SN), and individualized inclination of the lower incisors
Tahmina et al. (2000)56 (23 M, 33 F), Asians?CC + FIXED; nd9.3, 12.1, 18.42.8, 6.3Occlusal status at the end of treatment after pubertal growthSuccess, relapse53.6/46.4DFAGonial angle; N–A–Pog angle; RP/SN angle
Wells et al. (2006)41 (not declared), CaucasiansRME + FM; ndnd, nd, ndnd, minimum 5 yearsOJ > 0 mm -> successSuccess, relapse75.6/24.4DFAVertical position of PNS and Go, OB, Mn length
Yoshida et al. (2006)32 (0 M, 32 F), AsiansCC + FM + fixed; nd10.2, 11.6, 17.01.4, 5.4OJ, Angle classification (favourable responses to the orthopaedic appliances during the first phase of treatment, and optimal molar and canine relationships with a normal OJ and OB maintained long term -> success)Success, relapse50.0/50.0DFA; Regression analysisANS–Me and gonial angle
Zentner and Doll (2001)104 (nd), CaucasiansVarious; nd11.7, nd, 16.8nd, ndchange of PAR Index during treatmentGreatly improved, improved, worse/no different46.8/40.7/12.5Correlation analysisLow value of apical base relationship index (particularly resulting from undersized maxilla)
Zentner et al. (2001)80 (nd), Caucasians?Various; nd10.9, nd, 16.0nd, ndChange of PAR Index during treatmentGreatly improved, improved, worse/no different50.0/37.5/12.5Regression analysisTwo models: (1) apical base relationship and gonial angle; (2) apical base relationship, midfacial length/mandibular length ratio (Co–A to Co–Gn %), net sum of ‘maxillary difference’ (defined as difference between measured maxillary length and individual standard) and ‘mandibular difference’ (defined as difference between measured mandibular length and individual standard)
  • M, males; F, females; nd, not declared; PAR, Peer Assessment Rating; DFA, discriminant function analysis; RME, rapid maxillary expansion; FM, facemask; CHG, cervical headgear; CC, chincup; FA, functional appliance; fixed, fixed appliance; OJ, overjet; OB, overbite; APDI, anteroposterior dysplasia indicator; RP, mandibular ramus plane; and ?, likely.

  • *Prediction model unsuitable for children who required extractions.

According to the Centre for Reviews and Dissemination (2009), flaws in the design or conduct of a study can result in bias, and in some cases this can have as much influence on the observed effects as that of treatment. Evaluation of methodological quality gives an indication of the strength of evidence provided by the study. However, no single approach to assessing methodological soundness is appropriate to all systematic reviews. The best approach should be determined by contextual, pragmatic, and methodological considerations (Centre for Reviews and Dissemination, 2009). According to those guidelines, the subjective assessment of quality of investigations included in this systematic review comprised evaluation of description of selection process (including information as to whether the sample consisted of consecutively treated patients), sample size estimation and adequacy of outcome measures, method error estimation, statistical analysis, and validation. The criteria of quality score assignment are presented in Table 3. The quality of the studies was considered as follows: high—total score >9 points, medium/high—total score >7 and ≤9 points, medium—total score >5 and ≤7 points, and low—total score ≤5 points.

View this table:
Table 3

Assessment of quality of studies included in the review.

StudyA. Description of selection processB. Previous estimate of sample sizeC. Consecutive casesD. Choice of outcome measureE. Analysis of method errorF. Statistical analysisG. ValidationJudged quality standardQuality score
Points assignedMax points
0, 1, or 20 or 10 or 10, 1, or 20, 1, or 20 or 10, 1, or 20 to 11
Baccetti et al. (2004)20011105Low
Battagel (1993)10022117Medium
Ferro et al. (2003)10012105Low
Franchi et al. (1997)20012106Medium
Ghiz et al. (2005)10012105Low
Ko et al. (2004)10020104Low
Moon et al. (2005)10020104Low
Ngan and Wei (2004)10011104Low
Schuster et al. (2003)20012106Medium
Tahmina et al. (2000)10010103Low
Wells et al. (2006)10011104Low
Yoshida et al. (2006)10012105Low
Zentner and Doll (2001)10010103Low
Zentner et al. (2001)10010103Low
  • Description of quality score assignment: A—0, if inadequate description; 1, if some details of sample selection missing; and 2, if in-depth description of sample selection. B—0, if not performed and 1, if performed. C—0, if sample comprised non-consecutive patients or no information regarding this was included and 1, if sample comprised consecutive patients. D—0, if inadequate outcome measure; 1, if partially adequate outcome measure; and 2, if adequate outcome measure. E—0, if method error not evaluated; 1, if partially adequate method error analysis; and 2, if adequate method error. F—0, if inadequate and 1, if adequate. G—0, if not performed; 1, if partially adequate validation; and 2, if adequate validation.

Results

The search strategy resulted in the retrieval of 232 publications. Application of inclusion/exclusion criteria allowed identification of 14 relevant studies (Table 2), of which 11 were found both in PubMed and Embase, one exclusively in PubMed, and two were identified through hand searching. No pertinent article was found in the Cochrane Central Register or in the Lilacs database. The main reasons for exclusion were lack of identified predictors of success/relapse, case reports, and review articles.

Despite the fact that nominally 763 subjects were evaluated in the 14 included studies, the actual number of individuals examined was 683, because the sample evaluated by Zentner et al. (2001) was most probably part of another sample included in this review (Zentner and Doll, 2001). Gender distribution in three articles was not stated (Zentner and Doll, 2001; Zentner et al., 2001; Wells et al., 2006). Of the 538 subjects examined in the remaining 11 publications, 231 (43%) were males and 307 (57%) were females. In one study, the number of male subjects exceeded the number of females (Battagel, 1993), whereas Yoshida et al. (2006) included only females in their sample.

The ethnicity of the examined subjects was described in nine articles (Table 2). Ethnic background can be surmised on the basis of country of origin of five investigations. In two studies (Ngan and Wei, 2004; Ghiz et al., 2005), the samples comprised individuals of different ethnicity (Caucasian and Asian).

Various treatment regimens were employed in the examined samples. In five studies, patients treated with chincups were included: in four the chincup was the sole orthopaedic appliance (Tahmina et al., 2000; Ferro et al., 2003; Ko et al., 2004; Moon et al., 2005), whereas in the investigation by Yoshida et al. (2006) a combination of a chincup and facemask was employed. In five investigations, the treatment protocols included the use of facemasks, typically in combination with rapid maxillary expansion (Baccetti et al., 2004; Ngan and Wei, 2004; Ghiz et al., 2005; Wells et al., 2006; Yoshida et al., 2006). Orthopaedic appliances, such as cervical headgear attached to the mandible, or functional appliances were used less frequently (one study, Battagel, 1993). Three studies (Zentner and Doll, 2001; Zentner et al., 2001; Schuster et al., 2003) included patients treated by various methods.

The average age at commencement of treatment was 9.4 years and ranged from 5.6 (Franchi et al., 1997) to 12.4 (Battagel, 1993) years. The average age at which the final (end of follow-up) examination was carried out was 17.2 years and ranged from 15.8 (Franchi et al., 1997) to 22 (Ferro et al., 2003) years. The average length of post-treatment follow-up was 6.3 years and ranged from 5.4 (Baccetti et al., 2004; Yoshida et al., 2006) to 9 years (Ferro et al., 2003). It should be emphasized, however, that age at commencement and completion of treatment, age at final records, or length of follow-up were not always reported (Table 2).

Overjet was the most frequently used measure of treatment outcome. It was employed to establish success/(uncertain)/relapse groups by the authors of nine studies (Table 2). However, overjet was the only measure of treatment outcome in three studies (Ferro et al., 2003; Ngan and Wei, 2004; Wells et al., 2006); in other investigations, it was used in conjunction with overbite (Battagel, 1993; Ko et al., 2004; Moon et al., 2005) or with Angle classification (Baccetti et al., 2004; Ko et al., 2004; Ghiz et al., 2005; Yoshida et al., 2006). On the other hand, Zentner and Doll (2001) and Zentner et al. (2001) employed the Peer Assessment Rating (PAR) Index to identify successful or relapsed cases. Subjective measures, such as ‘need for surgery at the end of observation’ (Schuster et al., 2003), ‘good facial profile’ (Ko et al., 2004), or ‘occlusal status’ (Tahmina et al., 2000) were also used.

In 10 investigations, treatment outcome was described dichotomously (success versus relapse). The reported success rate ranged from 51.1 (Franchi et al., 1997) to 88.5 (Ferro et al., 2003) per cent. Ngan and Wei (2004) and Yoshida et al. (2006) matched success and relapse groups to include the same number of successful and relapsed patients. In those investigations, the success rate could not be calculated. Battagel (1993) and Moon et al. (2005) also established an ‘uncertain’ group, in which treatment outcome was judged as doubtful. If uncertain groups are disregarded, the success rate in the studies by Battagel (1993) and Moon et al. (2005) roughly corresponds to 50 per cent. Zentner and Doll (2001) and Zentner et al. (2001) employed the PAR Index to establish ‘greatly improved’, ‘improved’, and ‘worse/no different’ groups. Assuming that the results of treatment of patients from the greatly improved and improved groups were successful, the success rate was equal to 87.5 per cent.

In total, 38 different predictors of treatment outcome were identified in 14 studies. Thirty-five were cephalometric variables (20 linear, 13 angular, and two ratios) and three were derived from analysis of study models. Most studies reported a set of three to four predictors (Battagel, 1993; Franchi et al., 1997; Tahmina et al., 2000; Zentner et al., 2001; Ferro et al., 2003; Schuster et al., 2003; Baccetti et al., 2004; Ghiz et al., 2005; Wells et al., 2006). However, Ko et al. (2004) listed 12 variables, which were correlated with successful treatment outcome. On the other hand, Zentner and Doll (2001) and Ngan and Wei (2004) identified one predictor: apical base relationship (Zentner and Doll, 2001) and growth treatment response vector (Ngan and Wei, 2004).

Only two studies shared more than one predictor of treatment outcome. Ferro et al. (2003) and Ko et al. (2004) listed ANB angle and Wits appraisal as predictors. Gonial angle was the most frequently identified variable by different groups of researchers (Tahmina et al., 2000; Zentner et al., 2001; Ko et al., 2004; Ghiz et al., 2005; Yoshida et al., 2006); however, it was included in the prediction models in only five of 14 investigations (36%). Among other predictors identified in more than one study was the Wits appraisal (three studies), total mandibular length (Co–Pog), mandibular ramus length (Co–Goi), ANB angle, overbite, AB to mandibular plane angle, and apical base relationship (all in two studies).

Discussion

The uncertainty regarding the long-term results of Class III treatment was a stimulus to identify potential predictors of therapeutic success or failure. If an unfavourable outcome of therapy could be anticipated prior to treatment, then the type and timing of orthodontic/orthopaedic treatment could be modified. The authors of all studies included in this review employed a similar strategy of predicting factors – they divided patients long-term out of treatment into two (success versus relapse) or three (success versus uncertain versus relapse, or greatly improved versus improved versus worse/no different) groups demonstrating different therapeutic results. Subsequently, usually pre-treatment, variables correlated with treatment success or relapse, were established. In most studies discriminant function or regression analyses were performed to identify the sets of variables showing the highest prediction capability (i.e. prediction models). Ngan and Wei (2004) took a different approach. They evaluated cephalometric radiographs taken after the first phase of treatment [rapid maxillary expansion and facemask (RME+FM) therapy] and at follow-up. On the basis of post-treatment and follow-up cephalometric records, those authors then developed a ‘Growth treatment response vector (GTRV)’ – a ratio of horizontal growth changes of the maxilla and mandible determined along the occlusal plane. The GTRV below a certain value was reported to be suggestive of an unsuccessful second phase of treatment with fixed appliances. In such cases comprehensive edgewise treatment should be postponed.

The review of the 14 identified articles demonstrated that there were no studies that shared an identical set of predictors of treatment outcome. On the contrary, there was a substantial diversity of predictors. Of the 14 investigations, only Ferro et al. (2003) and Ko et al. (2004) enumerated concurrently more than one common variable (ANB and Wits). If the reviewed articles are grouped according to orthodontic/orthopaedic treatment modality (RME+FM or chincup), only little similarity can be observed within each group regarding detected predictors. For example, RME+FM treatment was used in the children examined by Baccetti et al. (2004), Ngan and Wei (2004), Ghiz et al. (2005), and Wells et al. (2006). Despite the extensive cephalometric analyses carried out (except for the investigation by Ngan and Wei, 2004), only two variables having a predictive value were simultaneously established in more than one study: mandibular ramus length (Baccetti et al., 2004; Ghiz et al., 2005) and total mandibular length (Ghiz et al., 2005; Wells et al., 2006). An alternative method of orthopaedic treatment of Class III malocclusion, the chincup, was used in the children followed by Tahmina et al. (2000), Ferro et al. (2003), Ko et al. (2004), and Moon et al. (2005). Of the 18 different predicting factors identified in the above mentioned four investigations, 14 were established only in a single study (Table 2) and four (ANB, Wits, gonial angle, and AB to mandibular plane angle) were identified concurrently by the authors of two studies (Table 2). Moreover values of coefficients of correlation between a particular variable and outcome might be low. Zentner et al. (2001) reported that the correlation coefficient for a set of two variables, gonial angle and apical base relationship, selected by means of regression analysis was 0.137; Pearson correlation coefficient (r) for gonial angle only was 0.238 (r2 = 0.057), which suggests a rather weak association between the set of selected predictors and treatment outcome.

The variety of the variables assumed to have a predictive value, the dissimilarity of the sets of predictors established by different groups of researchers, and the possible low correlation between a particular predictor and treatment outcome (only a few studies specified values of correlation coefficients) imply that prediction of Class III treatment outcome is questionable. On the other hand many authors reported high classification power for the developed prediction models: Franchi et al. (1997) demonstrated 95.6 per cent accuracy of discriminant function, Schuster et al. (2003) 93.2 per cent, Tahmina et al. (2000) 85.7 per cent, Yoshida et al. (2006) 84.4 per cent, and Baccetti et al. (2004) 83.3 per cent. A lower classification power (< 80%) was reported by Moon et al. (2005) where 77.8 per cent of cases were correctly classified, 73.3 per cent by Battagel (1993) and 73 per cent by Wells et al. (2006). In order to reconcile these conflicting data, an innate property (limitation) of prediction models based on discriminant function and regression analyses should be considered. Models for prediction of treatment outcome derived from these statistical procedures prognosticate post hoc what has occurred previously. It is not uncommon to obtain very good classification if one uses the same cases from which the classification functions are computed. In order to determine how well a current classification model ‘performs’ one must classify a priori different cases, that is, cases that were not used to estimate the classification model. Only classification of new cases allows assessment of the predictive validity of the classification model; the classification of old cases only provides a diagnostic tool to identify outliers or areas where classification function seems to be less adequate (Klecka, 1980; StatSoft Inc., 2008).

A priori classification of new cases was carried out only by Battagel (1993). Although correct classification of 7 out of 8 new patients resulted in a discriminative power of 87.5 per cent, the small number of classified cases precludes any firm conclusions. Unfortunately, as other authors did not perform validation procedures, the actual accuracy of the prediction is unknown. It can only be speculated that the low actual predictive power of the developed prediction models might have contributed to the wide disparity between them.

The number of groups created in the reviewed papers was not identical. Two groups, success and relapse, were established in 10 studies, and three groups, success, uncertain and relapse or greatly improved, improved and worse/no different, in four studies. Although similar outcome measures were employed in most investigations, overjet, overbite or Angle classification, they were not used uniformly. For example, Ghiz et al. (2005) set overjet at 1 mm as a discriminating value between the success and relapse groups, whereas Wells et al. (2006) determined successfully treated patients as having an overjet > 0 mm. Moon et al. (2005), in turn, defined their success group as patients with an overjet in excess of 2 mm. Overbite was also used differently in various studies. Battagel (1993) classified patients with overbite > 0 mm to the success group, whereas Moon et al. (2005) used an overbite > 1.5 mm for classification to the success group. As a result, success or relapse groups from various investigations were likely not equivalent. Therefore this potential inequivalence might have contributed to disparity among the prediction models.

The success rates, computed on the basis of data from the studies selected for this systematic review, may not be accurate due to inadequate sample selection. Determination of the success rate of a Class III treatment protocol should involve evaluation of consecutive patients. If the sample consists of selected rather than consecutive subjects there is a risk of unduly optimistic rates of success. A child diagnosed with a Class III malocclusion may be treated orthodontically or treatment may be delayed until craniofacial growth is complete. At that time orthodontic/surgical treatment is usually initiated. In, so called, borderline cases making a binary choice, i.e. to start or postpone treatment, is difficult since there are premises both to begin and to delay treatment. Some clinicians may initiate treatment, whereas others may postpone it, in a patient with a malocclusion of the same severity. Therefore, depending on the approach of an orthodontist or orthodontic department, if a similar treatment philosophy is adhered to – more aggressive (meaning orthodontic treatment of children even with severe malocclusions) or more cautious (meaning a delay of orthodontic therapy in subjects with severe Class III) – the success rate may differ despite the use of the same orthodontic protocol or appliance. It is also likely to be higher in a sample in which few borderline subjects are included, and lower in a sample with many borderline cases. Thus, the actual rate of success or relapse can be established provided a sample comprises consecutively diagnosed and treated children. Unfortunately, samples from the reviewed articles comprised selected cases and no information on the criteria regarding the treatment decision: treat versus postpone, was offered.

Conclusions

The following conclusions can be made on the basis of the review of the 14 included studies:

  • 1) The possibility of accurate prediction of outcome of orthodontic/orthopaedic treatment of Class III malocclusion seems questionable.

  • 2) Validation testing of a prediction model on the cases, which were not used to develop it, is mandatory in order to evaluate an actual discriminative power of the prediction model.

References

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