Dental developmental stage affects the treatment outcome of maxillary protraction in skeletal Class III children: A systematic review and meta-analysis
Article Category: research-article
Published Online: Jul 13, 2021
Page range: 37 - 49
DOI: https://doi.org/10.21307/aoj-2021-004
© 2021 Wei Miao et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
A skeletal Class III malocclusion may involve maxillary hypoplasia, or mandibular hyperplasia, or a combination of both. It has been found that approximately two-thirds of subjects presenting with a skeletal Class III malocclusion have maxillary hypoplasia, 1 which negatively affects orofacial aesthetics and function.
Maxillary protraction therapy using a facemask (reverse headgear) is invariably used for the treatment of skeletal Class III malocclusion as a result of maxillary hypoplasia in growing patients. 2-4 The principle of maxillary protraction includes opening the maxillary sutures, increasing cartilagenous and subperiosteal osteogenesis, promoting a favourable clockwise rotation of the mandible in low angle cases, and inhibiting unfavourable forward and downward growth of the mandible. 5,6
The optimal timing for maxillary protraction therapy is still cause for debate. A number of studies have found that maxillary protraction therapy carried out at an early age is more effective than that performed at a later age in improving a skeletal Class III relationship. 2,3,7-9 For example, a study using pubertal growth to select and group patients found that maxillary protraction applied at a pre-pubertal or mid-pubertal age showed greater orthopaedic effects than at late-puberty. 7 An additional study using chronological age to group patients showed that maxillary protraction therapy is more effective in patients under 10 years of age than in patients older than 10 years. 10 In contrast, further studies have found that a patient’s age had little influence on the effectiveness of maxillary protraction therapy. 11-14 For example, a study in patients with mixed dentitions (deciduous and permanent dentitions were not included) reported similar therapeutic responses when maxillary protraction began either before or after eight years of age. 11 An additional study also found no statistical difference in the treatment outcome of maxillary protraction in patients aged between seven and 12 years, and the amount of skeletal change between the protraction groups subdivided by age was not statistically significant. 12 The controversy regarding the optimal timing of maxillary protraction therapy was mainly due to the inconsistencies within the participants and the different methodologies used in the reported studies that did not include the deciduous dentition.
Therefore, the aim of this systematic review was to investigate the effect of the stage of dental development (i.e., primary dentition, early mixed dentition, late mixed dentition and early permanent dentition) on the treatment outcome of maxillary protraction in skeletal Class III children.
This systematic review followed the ROBINS-I (Risk Of Bias In Non-randomised Studies of Interventions) guidelines, as a tool for assessing the risk of bias in non-randomised studies of interventions. 15,16
A systematic search to identify all of the relevant studies was conducted within the following databases: MEDLINE (via PubMed; no restrictions were employed regarding language or year of publication), Web of Science, EMBASE, CENTRAL (The Cochrane Library), CBM (Chinese Biological Medical) database and CNKI (Chinese National Knowledge Infrastructure) database. A supplemental manual search was conducted by reviewing the reference lists of the related papers and review articles. The search strategy included controlled vocabulary and free terms. It was developed for MEDLINE and adapted for the other databases (Table I). The grey literature was searched on SIGLE (System for Information on Grey Literature in Europe), Clinicaltrial.gov, OpenGrey and the World Health Organization’s International Clinical Trial Registry Platform. The grey literature consists of papers that have not been published or have been published informally or non-commercially, such as government reports, statistics, patents, and conference papers and posters. All searches were conducted on 30 August 2019.
Search strategy used for PubMed.
| Search history | Number of results | |
|---|---|---|
| #1 | Maxillary protraction OR facemask OR face mask OR facial mask OR reverse headgear | 6340 |
| #2 | Class III OR Class 3 | 189199 |
| #3 | Malocclusion, Angle class III [Mesh] | 3528 |
| #4 | #2 OR #3 | 189199 |
| #5 | Primary dentition OR deciduous dentition | 15204 |
| #6 | Early mixed dentition OR late mixed dentition OR mixed dentition OR early permanent dentition | 3589 |
| #7 | #5 OR #6 | 17327 |
| #8 | #1 AND #4 AND #7 | 78 |
The inclusion criteria for the studies were participants who were patients presenting with a skeletal Class III malocclusion caused by maxillary hypoplasia from the period of the primary dentition to the early permanent dentition whose intervention involved maxillary protraction therapy using a facemask (with or without rapid maxillary expansion). A comparison was provided by untreated Class III patients who were matched for age and gender and whose outcomes were skeletal and dentoalveolar variables measured on lateral cephalometric radiographs. The study designs were randomised clinical trials (RCTs), controlled clinical trials (CCTs) or cohort studies and the published papers provided the original data or the data could be obtained from a primary source. The exclusion criteria of the studies were identified by case reports, review articles, conference papers, patients treated with other orthodontic or orthopaedic appliances, and patients affected by cleft lip/palate and/or other craniofacial syndromes.
Two calibrated reviewers (W.M. and D.Z.) independently screened the titles and abstracts of the identified studies. Consensus was obtained by discussion and consultation with the third reviewer (Y.P.) to resolve any disagreements during study selection and data extraction. The two reviewers (W.M. and D.Z.) independently extracted data from the studies using a data extraction form. The following information was collected: author and year of publication, country of origin, study design, number and age of participants, details of interventions and controls, assessment methods, and cephalometric outcomes.
Each study was assessed using the evaluation method recommended by the ROBINS-I. 15,16 Bias domains included bias due to confounding, bias due to the selection of participants into the study, bias due to intervention classification, bias due to deviations from intended interventions, bias due to missing data, bias due to outcome measurement and bias due to the selection of the reported result. The overall risk of bias of each study was assessed as low, moderate, serious, critical risk of bias or no information. In the present review, studies assessed at low risk of bias were defined as ‘high quality’, whereas others were considered as ‘low quality’. 15,16
Review Manager version 5.3 (The Cochrane Collaboration, 2012) was used for the meta-analysis.
17,18
Mean differences (MD) and standard mean differences (SMD) with 95% confidence intervals (95% CI) were calculated for all of the evaluated variables. SMD were used when the calculation of identical effects differed between the studies.
A total of 136 articles were screened for relevance (Figure 1). After applying inclusion and exclusion criteria, 97 studies did not meet the inclusion criteria and were excluded. A total of 39 full papers were retrieved and reviewed, among which 20 articles were excluded for the reasons given in Figure 1. Finally, 19 studies 2-4,7-9,11-14,19-27 were included in the systematic review.
Figure 1.
Flow Diagram.
The 19 trials included in the present review were published between 1993 and 2017 (12 studies were conducted in Asia, four in Europe, and three in North America), describing a total of 767 participants who were evaluated and grouped into primary dentition (N = 98), early mixed dentition (N = 325), late mixed dentition (N = 244), and early permanent dentition (N = 85) (Table II).
Characteristics of the included studies.
| Study | Location | Study design | Dentition (year of age) | Sample size | Appliance |
|---|---|---|---|---|---|
| Kajiyama 2004 | Japan | CCT | Primary (5.6) |
Primary (N=34) |
FM |
| Lee 2010 | South Korea | CCT | Primary (6.1) |
Primary (N=26) |
FM |
| Saadia 2000 | Mexico | CCT | Primary (3-6) |
Primary (N=38) |
FM+RME |
| Saadia 2001 | Mexico | CCT | Primary (3-6) |
Primary (N=38) |
FM+RME |
| Fareen 2017 | Malaysia | CCT | Early mixed (8-9) |
Early mixed (N=20) |
FM |
| Atalay 2010 | Turkey | CCT | Early mixed (8.18) |
Early mixed (N=15) |
FM |
| Cha 2003 | South Korea | CCT | Early mixed (9.82) |
Early mixed (N=34) |
FM+RME |
| Wang 2002 | China | CCT | Early mixed (7.3) |
Early mixed (N=32) |
FM+RME |
| Baccetti 2000 | Italy | CCT | Early mixed (5.5-7.8) |
Early mixed (N=16) |
FM+RME |
| Baccetti 1998 | Italy | CCT | Early mixed (6.9) |
Early mixed (N=23) |
FM+RME |
| Merwin 1997 | Hong Kong | CCT | Early mixed (6.8) |
Early mixed (N=15) |
FM+RME |
| Liu 2013 | China | CCT | No information (8-15) | Late mixed (N=14) |
FM |
| Yuksel 2001 | Turkey | CCT | Late mixed (9.8) |
Late mixed (N=17) |
FM |
| Takada 1993 | Japan | CCT | Early mixed (7.8) |
Early mixed (N=20) |
FM |
| Baik 1995 | South Korea | CCT | Early mixed (<10) |
Early mixed (N=11) |
FM+RME |
| Kapust 1998 | America | CCT | Primary dentition (4-7) |
Primary dentition (N=15) |
FM+RME |
CCT = Controlled clinical trial; FM = Facemask; RME = Rapid maxillary expansion.
The interventions used in the included studies were FM (facemask) and FM+RME (facemask and rapid maxillary expansion). The studies of Saadia et al. 13,21 appeared to be the same research with different cephalometric measurements, therefore these two studies were merged into one in the quantitative meta-analysis.
The treatment outcomes assessed in the included studies included SNA, SNB, ANB, SN/GoGn, ANS-Me, overjet and the Wits appraisal.
After a quality assessment, three of the included studies 2,8,27 were assessed as low risk of bias (high quality), eight studies 3,4,7,14,20,24-26 were assessed as having a moderate risk of bias, and five studies 11,13,21-23 were assessed as having a high risk of bias (Table III). When assessing bias due to confounding factors, the severity of the maxillary retrusion was considered as the most important factor influencing intergroup comparability. When assessing bias due to deviations from intended interventions, the timing and force of maxillary protraction that might affect the treatment outcomes and prognosis were considered as the most important factors.
Risk of bias of the included studies assessed by ROBINS-I (Risk Of Bias In Non-randomized Studies of Interventions).
| Study | Bias due to confounding | Bias in selection of participants into the study | Bias in classification of interventions | Bias due to deviations from intended interventions | Bias due to missing data | Bias in measurement of outcomes | Bias in selection of the reported result | Overall risk of bias |
|---|---|---|---|---|---|---|---|---|
| Kajiyama 2004 | Moderate | Moderate | Low | Low | Low | No information | Low | Moderate |
| Lee 2010 | Moderate | Moderate | Low | Low | Low | Low | Low | Moderate |
| Saadia 2000 | Serious | Moderate | Low | Low | Low | No information | Low | Serious |
| Saadia 2001 | Serious | Moderate | Low | Low | Low | No information | Low | Serious |
| Fareen 2017 | Low | Low | Low | Low | Low | Low | Low | Low |
| Atalay 2010 | Moderate | Moderate | Low | Low | Low | Low | Low | Moderate |
| Cha 2003 | Moderate | Serious | Low | Low | Low | Low | Low | Serious |
| Wang 2002 | Serious | Serious | Low | Low | Low | Low | Low | Serious |
| Baccetti 2000 | Moderate | Low | Low | Low | Low | No information | Low | Moderate |
| Baccetti 1998 | Low | Low | Low | Low | Low | No information | Low | Low |
| Merwin 1997 | Serious | Serious | Low | Low | Low | Low | Low | Serious |
| Liu 2013 | Moderate | Moderate | Low | Low | Low | Low | Low | Moderate |
| Yuksel 2001 | Moderate | Moderate | Low | Low | Low | No information | Low | Moderate |
| Takada 1993 | Moderate | Moderate | Low | Low | Low | Low | Low | Moderate |
| Baik 1995 | Moderate | Moderate | Low | Low | Low | Moderate | Low | Moderate |
| Kapust 1998 | Low | Low | Low | Low | Low | Low | Low | Low |
The Egger’s tests (Table IV) showed no publication bias in most of the measurements, except the SN/GoGn (
Egger’s test for the analysis of small study effects on publication bias.
| SNA | SNB | ANB | SN/GoGn | ANS/Me | Overjet | |
|---|---|---|---|---|---|---|
| Primary dentition vs early mixed dentition | 0.539 | 0.704 | 0.639 | 0.054 | N/A | N/A |
| Early mixed dentition vs late mixed dentition | 0.099 | 0.217 | 0.195 | 0.022* | 0.001* | 0.313 |
| Late mixed dentition vs early permanent dentition | 0.764 | 0.144 | 0.576 | 0.207 | N/A | 0.220 |
Five studies were included in the meta-analysis between the primary dentition and early mixed dentition (Figure 2). The treatment outcomes of maxillary protraction involved in the meta-analysis included SNA, SNB, ANB, SN/GoGn and ANS-Me. The treatment effect was significantly greater in the primary dentition than that produced in the early mixed dentition with respect to an increase in SNA (MD = 1.23°, 95% CI = 0.19 – 2.27,
Figure 2.
Meta-analysis between primary dentition and early mixed dentition.
The efficacy assessment of the primary dentition group for Class III malocclusion versus the early mixed dentition group. The comparison was performed using five indices. 1: Angle SNA. The primary dentition group presented a greater increase in SNA than the early mixed dentition group (MD = 1.23, 95% CI = 0.19 – 2.27,
Twelve studies were included in the meta-analysis between the early mixed dentition and late mixed dentition (Figure 3). The treatment outcomes of maxillary protraction involved in the meta-analysis included SNA, SNB, ANB, SN/GoGn, overjet and ANS-Me. The treatment effect was greater in the early mixed dentition than that produced in the late mixed dentition with respect to an increase in overjet (MD = -0.74 mm, 95% CI = -0.98 – -0.50,
Figure 3.
Meta-analysis between early mixed dentition and late mixed dentition.
The efficacy assessment of the early mixed dentition group for Class III malocclusion versus the late mixed dentition group. The comparison was performed using six indices. 1: Angle SNA. There were no significant differences in SNA between the two groups (MD = -0.39, 95% CI = -0.82 – 0.05,
The meta-analysis included five studies conducted between the late mixed dentition and early permanent dentition (Figure 4). The treatment outcomes of maxillary protraction involved in the meta-analysis included SNA, SNB, ANB, SN/GoGn, overjet and Wits. There was no statistically significant difference between the two groups in all outcomes, including SNA (MD = 0.61°, 95% CI = -0.16 – 1.38,
Figure 4.
Meta-analysis between late mixed dentition and early permanent dentition.
The efficacy assessment of the late mixed dentition group for Class III malocclusion versus the early permanent dentition group. The comparison was performed using six indices. 1: Angle SNA. There were no significant differences in SNA between the two groups (MD = 0.61, 95% CI = -0.16 – 1.38,
The meta-analysis included three studies conducted between the early mixed dentition and early permanent dentition (Figure 5). The treatment outcomes of maxillary protraction involved in the meta-analysis included SNA, SNB and ANB. The treatment effect was greater in the early mixed dentition than that produced in the early permanent dentition with respect to an increase in SNA (MD = 1.02°, 95% CI = 0.05 – 2.0,
Figure 5.
Meta-analysis between early mixed dentition and early permanent dentition.
The efficacy assessment of the early mixed dentition group for Class III malocclusion versus the early permanent dentition group. The comparison was performed using three indices. 1: Angle SNA. The early mixed dentition group presented a greater increase in SNA than the early permanent dentition group (MD = 1.02, 95% CI = 0.05 – 2.0,
The meta-analysis included two studies conducted between the primary dentition and late mixed dentition (Figure 6). The treatment outcomes of maxillary protraction involved in the meta-analysis included SNA, SNB and ANB. The treatment effect was significantly greater in the primary dentition than that produced in the late mixed dentition with respect to an increase in SNA (MD = 0.62°, 95% CI = 0.03– 1.21,
Figure 6.
Meta-analysis between primary dentition and late mixed dentition.
The efficacy assessment of the primary dentition group for Class III malocclusion versus the late mixed dentition group. The comparison was performed using three indices. 1: Angle SNA. The primary dentition group presented a greater increase in SNA than the late mixed dentition group (MD = 0.62, 95% CI = 0.03 – 1.21,
No study comparing the treatment effect of maxillary protraction between the primary dentition and the early permanent dentition was included in this review.
Maxillary protraction using a facemask is applied for the treatment of a skeletal Class III malocclusion. An important factor influencing the treatment effect of protraction therapy is considered by many to be the timing of treatment. Maxillary protraction has been carried out in growing patients at a variety of ages and dental stages, ranging from the primary dentition to the early permanent dentition. The optimal timing for maxillary protraction, however, is still unclear. The findings of the present systematic review suggest that the dental stage affects the treatment outcome of maxillary protraction for a hypomaxillary skeletal Class III malocclusion. The treatment effect at an early dental stage was more effective than that undertaken at a late dental stage in improving a skeletal Class III relationship. However, treatment duration and patient co-operation should not be overlooked when considering early treatment. In addition, although the variations in effectiveness between the various dental stage groups were generally statistically significant, most variations were small. This may affect clinical significance as standard deviations of 2 mm and 2 degrees have been considered as the threshold for clinically meaningful differences. 28
It has been found that an extra-oral protrusive force could cause remodelling of the circummaxillary sutures and maxillary tuberosity, as well as produce forward movement and anterior displacement of the maxilla. 6 Histological studies have shown that maxillary growth is dependent on the sutural activity located at the anterior border of the pterygoid process. The pterygopalatine and zygomaticomaxillary sutures require reaction in craniofacial complex remodelling during the treatment of skeletal Class III malocclusion. 29 Although clinical observations have suggested that the pterygopalatomaxillary suture may still be patent during adolescence and may keep playing a role in facial growth, there are few studies that show an accurate fusion time of these sutures prior to puberty.
In addition to chronological age, physiological age associated with dental age has been found to be clinically useful as a maturity indicator determining the pubertal growth period. 30 It has been commonly applied in clinical trials when assessing and grouping a patient’s growth stage. Previous studies have mostly focused on the mixed dentition and pubertal spurt, and a number of studies have also looked into relatively younger patients in the primary dentition as well as older patients in the early permanent dentition, with encouraging treatment results. Therefore, the present review included a wide range of dental stages; i.e., primary dentition, early mixed dentition, late mixed dentition, and the early permanent dentition.
In the current study, the maxillary protraction carried out during the primary dentition showed greater sagittal improvements than outcomes generated in the early and late mixed dentitions. These findings are in agreement with previous studies, 3,13,21 which have suggested that early treatment may be worthy of consideration for the management of a skeletal Class III malocclusion once a clear diagnosis is made and helpful patient co-operation occurs. Although the SNB angle decreased significantly more in the early mixed dentition compared with the late mixed dentition, the difference in treatment outcome between the early mixed dentition and late mixed dentition was not clearly evident based on the current meta-analysis. The change in SNB could also be due to the natural growth of the mandible, which resulted in the forward movement of point B leading to a natural change, particularly when patients grow relatively faster during the late mixed dentition than in the early mixed dentition. The improvement in overjet was a result of a skeletal effect (SNA, SN/GoGn and ANS/Me) and a dental effect (inclination of the mandibular incisors). 6 The maxillary protraction carried out during the late mixed dentition showed similar sagittal improvements as treatment performed during the early permanent dentition, which is consistent with the previous studies. 4,12 No difference has been found in the effect of maxillary advancement after maxillary protraction between the pre-pubertal and pubertal growth peak groups, but there was less maxillary skeletal advancement in the post-pubertal growth peak group. 23
Previous studies have also reported no difference between an early treatment group (7–10 years old) and a late treatment group (11–14 years old), 31 but the present study applied chronological age, rather than dental age, to group participants. In addition, there was great variation between the included studies regarding the type of appliances, the wear time per day, the force strength applied, and the possible combination with RME (rapid maxillary expansion), which could potentially contribute to the clinical heterogeneity of the studies included in the systematic review. As an example in the quantitative analysis of the study, nine studies used facemask in combination with RME, 2,8,11,13,14,20-23 while seven studies used facemask alone. 3,4,7,24-27 It was noted that a number of studies reported that there was no significant difference in the treatment outcomes of maxillary protraction with or without RME, except for reduced upper incisor angulation when the RME was performed. 10,32,33 The follow-up period of the included studies was relatively short, and ranged from six months to two years. The long-term effect of maxillary protraction therapy still requires more well-designed, controlled trials.
The dental stage affected the treatment outcome of protraction in hypoplastic maxillary Class III children. The treatment effect at an early dental stage may be more effective than that at a later stage in improving the skeletal Class III relationship. However, treatment duration and patient co-operation should not be neglected when considering early treatment. The long-term effect of maxillary protraction therapy still requires more well-designed, controlled trials.