The Open Dentistry Journal




ISSN: 1874-2106 ― Volume 13, 2019

The Effect of Chin-cup Therapy in Class III Malocclusion: A Systematic Review



Sophia Mousoulea1, *, Ioannis Tsolakis2, Efstratios Ferdianakis3, Apostolos I. Tsolakis3
1 Department of Orthodontics and Dentofacial Orthopedics, 251 Hellenic Air Force General Hospital, Athens, Greece
2 Laboratory for Experimental Surgery and Surgical Research “N. S. Christeas”, Medical School, University of Athens, Greece
3 Department of Orthodontics, School of Dentistry, University of Athens, Greece

Abstract

Background:

The treatment of Class III malocclusion has been challenging for orthodontists. Among a plethora of treatment modalities, the chin-cup is considered a traditional appliance for early orthopedic intervention.

Objective:

The present study aims to investigate the current scientific evidence regarding the effectiveness of chin-cup therapy in Class III malocclusion of prognathic growing patients.

Method:

A systematic review of the literature was conducted using PubMed/Medline and the Cochrane Central Register of Controlled Trials from January 1954 to October 2015. Articles were selected based on established inclusion/ exclusion criteria.

Results:

The search strategy resulted in 3285 articles.14 studies were selected for the final analysis. They were all CCTs, 13 of retrospective and 1 of prospective design. Methodological quality was evaluated by a risk of bias assessment, as suggested by the Cochrane Risk of Bias Assessment Tool for Non-Randomized Studies on Interventions. The reported evidence presented favorable short-term outcomes both in hard and soft tissues improving the Class III profile, as well as desirable dento-alveolar changes, positively affecting the Class III malocclusion.

Conclusion:

There is considerable agreement between studies that chin-cup therapy can be considered for the short-term treatment of growing patients with Class III malocclusion, as indicated by favorable changes both in the hard and soft tissues. The existence of considerable risk of bias in all selected studies and the unclear long-term effectiveness of chin-cup therapy highlight the need for further investigation to draw reliable conclusions.

Keywords: Chin-cup Therapy, Class III Malocclusion, Class III Treatment, Mandibular Prognathism, Skeletal Malocclusion, Systematic Review.


Article Information


Identifiers and Pagination:

Year: 2016
Volume: 10
First Page: 664
Last Page: 679
Publisher Id: TODENTJ-10-664
DOI: 10.2174/1874210601610010664

Article History:

Received Date: 05/03/2016
Revision Received Date: 07/09/2016
Acceptance Date: 28/10/2016
Electronic publication date: 09/12/2016
Collection year: 2016

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open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution-Non-Commercial 4.0 International Public License (CC BY-NC 4.0) (https://creativecommons.org/licenses/by-nc/4.0/legalcode), which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.


* Address correspondence to this author at the Department of Orthodontics and Dentofacial Orthopedics, 251 Hellenic Air Force General Hospital, Athens, Greece; Tel: +306973277463; E-mail: sophia.mousoulea@gmail.com




INTRODUCTION

Skeletal Class III malocclusion is clinically presented as a result of maxillary retrusion, mandibular protrusion or a combination of the two [1Toffol LD, Pavoni C, Baccetti T, Franchi L, Cozza P. Orthopedic treatment outcomes in Class III malocclusion. A systematic review. Angle Orthod 2008; 78(3): 561-73.
[http://dx.doi.org/10.2319/030207-108.1] [PMID: 18416617]
-3Gelgör IE, Karaman AI. Non-surgical treatment of Class III malocclusion in adults: two case reports. J Orthod 2005; 32(2): 89-97.
[http://dx.doi.org/10.1179/146531205225020952] [PMID: 15994982]
]. It is often associated with complex dento-alveolar problems, which include an anterior edge-to-edge relation or anterior and/or posterior crossbite [4Karakıs D, Kaymak D, Dogan A. The evaluation of maximum bite force in the occlusal rehabilitation of patient with Angle Class III malocclusion: a case report. J Adv Prosthodont 2013; 5(3): 364-8.
[http://dx.doi.org/10.4047/jap.2013.5.3.364] [PMID: 24049580]
]. Patients with Class III malocclusion exhibit potential esthetic problems presenting a concave profile, and a vertical function pattern [3Gelgör IE, Karaman AI. Non-surgical treatment of Class III malocclusion in adults: two case reports. J Orthod 2005; 32(2): 89-97.
[http://dx.doi.org/10.1179/146531205225020952] [PMID: 15994982]
, 4Karakıs D, Kaymak D, Dogan A. The evaluation of maximum bite force in the occlusal rehabilitation of patient with Angle Class III malocclusion: a case report. J Adv Prosthodont 2013; 5(3): 364-8.
[http://dx.doi.org/10.4047/jap.2013.5.3.364] [PMID: 24049580]
], which limits their function to vertical movements.

The prevalence of Class III malocclusion presents a wide variety among and within populations [5Hardy DK, Cubas YP, Orellana MF. Prevalence of angle class III malocclusion: a systematic review and meta- analysis. Open J Epidemiol 2012; 2: 75-82.
[http://dx.doi.org/10.4236/ojepi.2012.24012]
, 6Soh J, Sandham A, Chan YH. Occlusal status in Asian male adults: prevalence and ethnic variation. Angle Orthod 2005; 75(5): 814-20.
[PMID: 16279828]
], as declared by a high 23% rate in Asian populations contrasted to a smaller 5% rate in Caucasians [1Toffol LD, Pavoni C, Baccetti T, Franchi L, Cozza P. Orthopedic treatment outcomes in Class III malocclusion. A systematic review. Angle Orthod 2008; 78(3): 561-73.
[http://dx.doi.org/10.2319/030207-108.1] [PMID: 18416617]
, 7Zurfluh MA, Kloukos D, Patcas R, Eliades T. Effect of chin-cup treatment on the temporomandibular joint: a systematic review. Eur J Orthod 2015; 37(3): 314-24.
[http://dx.doi.org/10.1093/ejo/cju048] [PMID: 25179261]
]. Treatment of Class III malocclusion has been a challenge for orthodontists [1Toffol LD, Pavoni C, Baccetti T, Franchi L, Cozza P. Orthopedic treatment outcomes in Class III malocclusion. A systematic review. Angle Orthod 2008; 78(3): 561-73.
[http://dx.doi.org/10.2319/030207-108.1] [PMID: 18416617]
]. Among various treatment modalities, the chin-cup is considered a traditional appliance for the early orthopedic management of prognathic growing patients [2Liu ZP, Li CJ, Hu HK, Chen JW, Li F, Zou SJ. Efficacy of short-term chincup therapy for mandibular growth retardation in Class III malocclusion. Angle Orthod 2011; 81(1): 162-8.
[http://dx.doi.org/10.2319/050510-244.1] [PMID: 20936970]
, 8Ritucci R, Nanda R. The effect of chin cup therapy on the growth and development of the cranial base and midface. Am J Orthod Dentofacial Orthop 1986; 90(6): 475-83.
[http://dx.doi.org/10.1016/0889-5406(86)90107-1] [PMID: 3466528]
-11De Clerck HJ, Proffit WR. Growth modification of the face: A current perspective with emphasis on Class III treatment. Am J Orthod Dentofacial Orthop 2015; 148(1): 37-46.
[http://dx.doi.org/10.1016/j.ajodo.2015.04.017] [PMID: 26124026]
]. Its clinical effectiveness has been investigated over the years with many studies confirming a general improvement of Class III malocclusion through backward and downward mandibular rotation, retardation of mandibular growth, remodeling of the mandible and the temporomandibular joint (TMJ), retroclination of mandibular incisors and closing of the gonial angle [1Toffol LD, Pavoni C, Baccetti T, Franchi L, Cozza P. Orthopedic treatment outcomes in Class III malocclusion. A systematic review. Angle Orthod 2008; 78(3): 561-73.
[http://dx.doi.org/10.2319/030207-108.1] [PMID: 18416617]
, 2Liu ZP, Li CJ, Hu HK, Chen JW, Li F, Zou SJ. Efficacy of short-term chincup therapy for mandibular growth retardation in Class III malocclusion. Angle Orthod 2011; 81(1): 162-8.
[http://dx.doi.org/10.2319/050510-244.1] [PMID: 20936970]
, 7Zurfluh MA, Kloukos D, Patcas R, Eliades T. Effect of chin-cup treatment on the temporomandibular joint: a systematic review. Eur J Orthod 2015; 37(3): 314-24.
[http://dx.doi.org/10.1093/ejo/cju048] [PMID: 25179261]
, 10Chatzoudi MI, Ioannidou-Marathiotou I, Papadopoulos MA. Clinical effectiveness of chin cup treatment for the management of Class III malocclusion in pre-pubertal patients: a systematic review and meta-analysis. Prog Orthod 2014; 15: 62.
[http://dx.doi.org/10.1186/s40510-014-0062-9] [PMID: 25679781]
, 11De Clerck HJ, Proffit WR. Growth modification of the face: A current perspective with emphasis on Class III treatment. Am J Orthod Dentofacial Orthop 2015; 148(1): 37-46.
[http://dx.doi.org/10.1016/j.ajodo.2015.04.017] [PMID: 26124026]
].

Despite the plethora of the available evidence, clinical results achieved with the chin-cup constitute a controversial issue among researchers. Owing to the absence of a standard protocol concerning the chin-cup’s appropriate use and the contradicting results of the reported outcomes and outcomes measures, a clear interpretation of data is not possible [1Toffol LD, Pavoni C, Baccetti T, Franchi L, Cozza P. Orthopedic treatment outcomes in Class III malocclusion. A systematic review. Angle Orthod 2008; 78(3): 561-73.
[http://dx.doi.org/10.2319/030207-108.1] [PMID: 18416617]
, 2Liu ZP, Li CJ, Hu HK, Chen JW, Li F, Zou SJ. Efficacy of short-term chincup therapy for mandibular growth retardation in Class III malocclusion. Angle Orthod 2011; 81(1): 162-8.
[http://dx.doi.org/10.2319/050510-244.1] [PMID: 20936970]
, 7Zurfluh MA, Kloukos D, Patcas R, Eliades T. Effect of chin-cup treatment on the temporomandibular joint: a systematic review. Eur J Orthod 2015; 37(3): 314-24.
[http://dx.doi.org/10.1093/ejo/cju048] [PMID: 25179261]
,12Watkinson S, Harrison JE, Furness S, Worthington HV. Orthodontic treatment for prominent lower front teeth (Class III malocclusion) in children. Cochrane Database Syst Rev 2013; 9(9): CD003451.
[http://dx.doi.org/10.1002/14651858.CD003451.pub2] [PMID: 24085611]
]. Although a great number of studies focus on the skeletal and dento-alveolar changes [2Liu ZP, Li CJ, Hu HK, Chen JW, Li F, Zou SJ. Efficacy of short-term chincup therapy for mandibular growth retardation in Class III malocclusion. Angle Orthod 2011; 81(1): 162-8.
[http://dx.doi.org/10.2319/050510-244.1] [PMID: 20936970]
, 7Zurfluh MA, Kloukos D, Patcas R, Eliades T. Effect of chin-cup treatment on the temporomandibular joint: a systematic review. Eur J Orthod 2015; 37(3): 314-24.
[http://dx.doi.org/10.1093/ejo/cju048] [PMID: 25179261]
, 10Chatzoudi MI, Ioannidou-Marathiotou I, Papadopoulos MA. Clinical effectiveness of chin cup treatment for the management of Class III malocclusion in pre-pubertal patients: a systematic review and meta-analysis. Prog Orthod 2014; 15: 62.
[http://dx.doi.org/10.1186/s40510-014-0062-9] [PMID: 25679781]
-12Watkinson S, Harrison JE, Furness S, Worthington HV. Orthodontic treatment for prominent lower front teeth (Class III malocclusion) in children. Cochrane Database Syst Rev 2013; 9(9): CD003451.
[http://dx.doi.org/10.1002/14651858.CD003451.pub2] [PMID: 24085611]
], the effects of chin-cup therapy on facial soft tissues remain uninvestigated. Furthermore, the vast majority of studies report outcomes of the chin-cup use obtained over a short-term period [2Liu ZP, Li CJ, Hu HK, Chen JW, Li F, Zou SJ. Efficacy of short-term chincup therapy for mandibular growth retardation in Class III malocclusion. Angle Orthod 2011; 81(1): 162-8.
[http://dx.doi.org/10.2319/050510-244.1] [PMID: 20936970]
, 7Zurfluh MA, Kloukos D, Patcas R, Eliades T. Effect of chin-cup treatment on the temporomandibular joint: a systematic review. Eur J Orthod 2015; 37(3): 314-24.
[http://dx.doi.org/10.1093/ejo/cju048] [PMID: 25179261]
, 10Chatzoudi MI, Ioannidou-Marathiotou I, Papadopoulos MA. Clinical effectiveness of chin cup treatment for the management of Class III malocclusion in pre-pubertal patients: a systematic review and meta-analysis. Prog Orthod 2014; 15: 62.
[http://dx.doi.org/10.1186/s40510-014-0062-9] [PMID: 25679781]
, 12Watkinson S, Harrison JE, Furness S, Worthington HV. Orthodontic treatment for prominent lower front teeth (Class III malocclusion) in children. Cochrane Database Syst Rev 2013; 9(9): CD003451.
[http://dx.doi.org/10.1002/14651858.CD003451.pub2] [PMID: 24085611]
], while there is a lack of studies examining the long-term effectiveness of chin-cup therapy.

For the aforementioned reasons the purpose of the present systematic review is the investigation of the short- and long-term effects on both the hard and soft tissues induced by chin-cup therapy in the Class III malocclusion of growing patients, based on the existing scientific evidence.

MATERIALS AND METHODOLOGY

Type of Participants

Prognathic growing patients (pre-pubertal, pubertal) with Class III malocclusion receiving chin-cup therapy for the improvement of their skeletal, dento-alveolar and facial characteristics.

Type of Interventions

Chin-cups. (Potential confounders and co-interventions were specified and taken into account).

Comparisons

No treatment.

Outcomes

-Primary: Skeletal, dento-alveolar and soft-tissue effects of chin-cup therapy.

-Secondary: Short and long-term effectiveness of chin-cup therapy, if provided, in order to assess the stability of the results.

All reported time-points after the completion of the treatment, judged by the authors of the trials were included. The short-term effectiveness is related to the outcomes obtained upon the end of the active treatment with chin-cup therapy, while the long-term effectiveness is related to the ones obtained at a post-treatment observation after the end of the active treatment.

Search Strategy

A literature search was carried out by applying the Medline database (PubMed www.ncbi.nih.gov) and the Cochrane Central Register of Controlled Trials covering the period from January 1954 to October 2015 and using the following Medical Subject Heading (MeSH) terms; “Malocclusion, Angle Class III”, “chin-cup therapy”, “chincap therapy”, (Table 1). A schematic representation of the search strategy is shown in Fig. (1).

Table 1
Search strategy.


Fig. (1)
Flow diagram of the literature search process.


Selection Criteria

Articles selected for this study fulfilled the criteria for inclusion, (Table 2). The criteria included randomized clinical trials (RCTs), prospective and retrospective clinical trials (CCTs) with untreated control groups. The retrieved studies had to use cephalometrics for analyzing the effects of chin-cup therapy contrasted to untreated Class III control groups. Table 2 also presents in detail the exclusion criteria.

Table 2
Inclusion-exclusion criteria.


Data Extraction

Two independent reviewers (SM, EF) made the assessment of the articles individually in predefined data extraction forms. No blinding to the authors during data extraction was made and any inter-examiner conflicts were resolved by discussion with a third reviewer (IT). The same reviewers performed the risk of bias assessment of the articles, with one author (AT) acting as the coordinator.

Quality Analysis

For the qualitative evaluation of the retrieved studies the risk of bias was assessed by two reviewers (SM, EF) independently. The assessment was based on the following tool: A Cochrane Risk of Bias Assessment Tool for Non-Randomized Studies on Interventions (ACROBAT-NRSI) [13Sterne JAC, Higgins JPT, Reeves BC, et al. On behalf of the development group for ACROBAT-NRSI. A Cochrane Risk of Bias Assessment Tool for Non-randomized Studies of Interventions (ACROBAT- NRSI), Version 1.0.0, 2014 September 24; [accessed 2015 November 27] Available from: http://www.riskofbias.info ]. This tool addresses seven domains of bias; bias due to confounding, bias in selection of participants into the study, bias in measurement of interventions, bias due to departures from intended intervention, bias due to missing data, bias in measurement of outcomes and bias in selection of the reported result.

Important confounders with regard to chin-cup therapy were considered those that could have an impact on the reported results. Thus, the following confounders were taken into account both for patients and controls: ethnicity (as Asian populations have a higher prevalence of Class III malocclusion) [1Toffol LD, Pavoni C, Baccetti T, Franchi L, Cozza P. Orthopedic treatment outcomes in Class III malocclusion. A systematic review. Angle Orthod 2008; 78(3): 561-73.
[http://dx.doi.org/10.2319/030207-108.1] [PMID: 18416617]
, 7Zurfluh MA, Kloukos D, Patcas R, Eliades T. Effect of chin-cup treatment on the temporomandibular joint: a systematic review. Eur J Orthod 2015; 37(3): 314-24.
[http://dx.doi.org/10.1093/ejo/cju048] [PMID: 25179261]
,14Miyajima K, McNamara JA Jr, Sana M, Murata S. An estimation of craniofacial growth in the untreated Class III female with anterior crossbite. Am J Orthod Dentofacial Orthop 1997; 112(4): 425-34.
[http://dx.doi.org/10.1016/S0889-5406(97)70051-9] [PMID: 9345155]
-16Ngan P. Early treatment of Class III malocclusion. Semin Orthod 2005; 11: 140-5.
[http://dx.doi.org/10.1053/j.sodo.2005.04.007]
], age in relation to the skeletal maturity stage, pre-treatment skeletal Class of malocclusion (when it was not skeletal Class III both for patients and controls), soft-tissue profile individual variation in thickness and in tension, and pre-treatment overjet. Moreover, co-interventions were considered the use of additional appliances, such as an occlusal bite plate, a quad-helix appliance, a lingual arch, etc., and the utilization of force magnitude of the chin-cup traction.

Three different outcomes were investigated; skeletal, dento-alveolar and soft-tissue effects of chin-cup therapy in Class III malocclusion both in the short- and in the long-term. For every different outcome of each study an initial risk of bias for every domain was assessed, as indicated by the ACROBAT-NRSI [13Sterne JAC, Higgins JPT, Reeves BC, et al. On behalf of the development group for ACROBAT-NRSI. A Cochrane Risk of Bias Assessment Tool for Non-randomized Studies of Interventions (ACROBAT- NRSI), Version 1.0.0, 2014 September 24; [accessed 2015 November 27] Available from: http://www.riskofbias.info ]. Because same issues applied to all outcomes, a grouped assessment was made. Finally, an overall risk of bias judgement for each study was achieved.

RESULTS

Our search strategy resulted in 3285 articles. After selection, according to the inclusion/exclusion criteria (Table 2), 46 studies were gathered and read in full-text. Finally, 14 studies were retrieved for the final analysis. The remaining 32 articles were excluded, mainly, because there were no untreated controls or the controls were not skeletal Class III patients, the treatment was combined with extractions or surgery and their objective was out of the scope of interest of the present study. Table 3 summarizes the data of the 14 included studies.

Clinical heterogeneity among studies (different outcome assessment, variable age of patients and different follow-up duration), and the high risk of bias in general precluded the quantitative synthesis of results in a meta-analysis.

Skeletal Effects

The majority of the studies showed a general improvement of skeletal Class III malocclusion, through increased ANB [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
-22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
], Wits appraisal [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
] and decreased SNB [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
-22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
], SNPg [23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
]. Moreover, the anterior facial height [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 18Tuncer BB, Kaygisiz E, Tuncer C, Yüksel S. Pharyngeal airway dimensions after chin cup treatment in Class III malocclusion subjects. J Oral Rehabil 2009; 36(2): 110-7.
[http://dx.doi.org/10.1111/j.1365-2842.2008.01910.x] [PMID: 19522895]
, 22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
], the mandibular plane angle (SN-MP) [18Tuncer BB, Kaygisiz E, Tuncer C, Yüksel S. Pharyngeal airway dimensions after chin cup treatment in Class III malocclusion subjects. J Oral Rehabil 2009; 36(2): 110-7.
[http://dx.doi.org/10.1111/j.1365-2842.2008.01910.x] [PMID: 19522895]
-20Lin HC, Chang HP, Chang HF. Treatment effects of occipitomental anchorage appliance of maxillary protraction combined with chincup traction in children with Class III malocclusion. J Formos Med Assoc 2007; 106(5): 380-91.
[http://dx.doi.org/10.1016/S0929-6646(09)60323-5] [PMID: 17561473]
, 22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
] and the FMA [23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
] were significantly increased, whereas the gonial angle [20Lin HC, Chang HP, Chang HF. Treatment effects of occipitomental anchorage appliance of maxillary protraction combined with chincup traction in children with Class III malocclusion. J Formos Med Assoc 2007; 106(5): 380-91.
[http://dx.doi.org/10.1016/S0929-6646(09)60323-5] [PMID: 17561473]
, 23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
, 25Alarcón JA, Bastir M, Rosas A, Molero J. Chincup treatment modifies the mandibular shape in children with prognathism. Am J Orthod Dentofacial Orthop 2011; 140(1): 38-43.
[http://dx.doi.org/10.1016/j.ajodo.2009.10.046] [PMID: 21724085]
, 26Deguchi T, McNamara JA. Craniofacial adaptations induced by chincup therapy in Class III patients. Am J Orthod Dentofacial Orthop 1999; 115(2): 175-82.
[http://dx.doi.org/10.1016/S0889-5406(99)70346-X] [PMID: 9971929]
] was significantly decreased, indicating a tendency towards a backward and downward rotation of the mandible induced by the chin-cup. Furthermore, restraint of the mandibular length was pointed out in five studies [23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
, 25Alarcón JA, Bastir M, Rosas A, Molero J. Chincup treatment modifies the mandibular shape in children with prognathism. Am J Orthod Dentofacial Orthop 2011; 140(1): 38-43.
[http://dx.doi.org/10.1016/j.ajodo.2009.10.046] [PMID: 21724085]
-28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
] by significant decreases in mandibular body length [23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
, 27Wendell PD, Nanda R, Sakamoto T, Nakamura S. The effects of chin cup therapy on the mandible: a longitudinal study. Am J Orthod 1985; 87(4): 265-74.
[http://dx.doi.org/10.1016/0002-9416(85)90001-6] [PMID: 3857003]
], total mandibular length [23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
, 26Deguchi T, McNamara JA. Craniofacial adaptations induced by chincup therapy in Class III patients. Am J Orthod Dentofacial Orthop 1999; 115(2): 175-82.
[http://dx.doi.org/10.1016/S0889-5406(99)70346-X] [PMID: 9971929]
-28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
] and anteroposterior compression of the distance between the condyle and the coronoid process [25Alarcón JA, Bastir M, Rosas A, Molero J. Chincup treatment modifies the mandibular shape in children with prognathism. Am J Orthod Dentofacial Orthop 2011; 140(1): 38-43.
[http://dx.doi.org/10.1016/j.ajodo.2009.10.046] [PMID: 21724085]
]. Significant reduction of the ramus height was also noted [22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
, 23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
, 25Alarcón JA, Bastir M, Rosas A, Molero J. Chincup treatment modifies the mandibular shape in children with prognathism. Am J Orthod Dentofacial Orthop 2011; 140(1): 38-43.
[http://dx.doi.org/10.1016/j.ajodo.2009.10.046] [PMID: 21724085]
, 27Wendell PD, Nanda R, Sakamoto T, Nakamura S. The effects of chin cup therapy on the mandible: a longitudinal study. Am J Orthod 1985; 87(4): 265-74.
[http://dx.doi.org/10.1016/0002-9416(85)90001-6] [PMID: 3857003]
]. With regard to the skeletal changes in the cranial base and the midface, two studies [8Ritucci R, Nanda R. The effect of chin cup therapy on the growth and development of the cranial base and midface. Am J Orthod Dentofacial Orthop 1986; 90(6): 475-83.
[http://dx.doi.org/10.1016/0889-5406(86)90107-1] [PMID: 3466528]
, 27Wendell PD, Nanda R, Sakamoto T, Nakamura S. The effects of chin cup therapy on the mandible: a longitudinal study. Am J Orthod 1985; 87(4): 265-74.
[http://dx.doi.org/10.1016/0002-9416(85)90001-6] [PMID: 3857003]
] reported significant closure of the cranial flexure angle (N-S-Ba), indicating inhibition of the downward vertical growth of the midface [8Ritucci R, Nanda R. The effect of chin cup therapy on the growth and development of the cranial base and midface. Am J Orthod Dentofacial Orthop 1986; 90(6): 475-83.
[http://dx.doi.org/10.1016/0889-5406(86)90107-1] [PMID: 3466528]
] and less downward mandibular displacement relative to the cranial base [27Wendell PD, Nanda R, Sakamoto T, Nakamura S. The effects of chin cup therapy on the mandible: a longitudinal study. Am J Orthod 1985; 87(4): 265-74.
[http://dx.doi.org/10.1016/0002-9416(85)90001-6] [PMID: 3857003]
].

Table 3
Data extraction.


Dento-Alveolar Effects

The main dento-alveolar changes produced by the chin-cup were the achievement of a significant overjet [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 20Lin HC, Chang HP, Chang HF. Treatment effects of occipitomental anchorage appliance of maxillary protraction combined with chincup traction in children with Class III malocclusion. J Formos Med Assoc 2007; 106(5): 380-91.
[http://dx.doi.org/10.1016/S0929-6646(09)60323-5] [PMID: 17561473]
-22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
, 29Gökalp H, Kurt G. Magnetic resonance imaging of the condylar growth pattern and disk position after chin cup therapy: a preliminary study. Angle Orthod 2005; 75(4): 568-75.
[PMID: 16097225]
] and retroclination of the lower incisors [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 19Akin M, Ucar FI, Chousein C, Sari Z. Effects of chincup or facemask therapies on the orofacial airway and hyoid position in Class III subjects. J Orofac Orthop 2015; 76(6): 520-30.
[http://dx.doi.org/10.1007/s00056-015-0315-3] [PMID: 26446505]
, 21Barrett AA, Baccetti T, McNamara JA Jr. Treatment effects of the light-force chincup. Am J Orthod Dentofacial Orthop 2010; 138(4): 468-76.
[http://dx.doi.org/10.1016/j.ajodo.2008.12.024] [PMID: 20889053]
, 22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
]. More precisely, Ritucci and Nanda [8Ritucci R, Nanda R. The effect of chin cup therapy on the growth and development of the cranial base and midface. Am J Orthod Dentofacial Orthop 1986; 90(6): 475-83.
[http://dx.doi.org/10.1016/0889-5406(86)90107-1] [PMID: 3466528]
] declared that transition in overjet occurred with a marked degree of flaring of the maxillary incisors, followed by a variable amount of uprighting, based on lateral cephalograms. Overjet correction was, also, reported byAlacrόn et al. [25Alarcón JA, Bastir M, Rosas A, Molero J. Chincup treatment modifies the mandibular shape in children with prognathism. Am J Orthod Dentofacial Orthop 2011; 140(1): 38-43.
[http://dx.doi.org/10.1016/j.ajodo.2009.10.046] [PMID: 21724085]
], mainly achieved by mandibular incisor retroclination. Moreover, Barrett et al. [21Barrett AA, Baccetti T, McNamara JA Jr. Treatment effects of the light-force chincup. Am J Orthod Dentofacial Orthop 2010; 138(4): 468-76.
[http://dx.doi.org/10.1016/j.ajodo.2008.12.024] [PMID: 20889053]
] noted the uprighting of the lower incisors, indicated by the decreased IMPA, as the most significant dental change between the chin-cup and the control groups. Significant proclination of the upper incisors [8Ritucci R, Nanda R. The effect of chin cup therapy on the growth and development of the cranial base and midface. Am J Orthod Dentofacial Orthop 1986; 90(6): 475-83.
[http://dx.doi.org/10.1016/0889-5406(86)90107-1] [PMID: 3466528]
, 17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 19Akin M, Ucar FI, Chousein C, Sari Z. Effects of chincup or facemask therapies on the orofacial airway and hyoid position in Class III subjects. J Orofac Orthop 2015; 76(6): 520-30.
[http://dx.doi.org/10.1007/s00056-015-0315-3] [PMID: 26446505]
, 20Lin HC, Chang HP, Chang HF. Treatment effects of occipitomental anchorage appliance of maxillary protraction combined with chincup traction in children with Class III malocclusion. J Formos Med Assoc 2007; 106(5): 380-91.
[http://dx.doi.org/10.1016/S0929-6646(09)60323-5] [PMID: 17561473]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
] was also pointed out. However, the aforementioned results, especially those regarding the proclined upper incisors, should be carefully interpreted in order to clarify whether they constitute net effects of the chin-cup alone or the additional appliances that were used and were co-interventions.

Changes regarding overbite varied, depending on the appliance that was used. More specifically, Arman et al. [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
] noted a significant decrease in overbite in all the treated groups (chin-cups only, chin-cups with removable bite plate, reverse headgear with rapid maxillary expansion devices).

Regarding the molar relationship after the active treatment, Ritucci and Nanda [8Ritucci R, Nanda R. The effect of chin cup therapy on the growth and development of the cranial base and midface. Am J Orthod Dentofacial Orthop 1986; 90(6): 475-83.
[http://dx.doi.org/10.1016/0889-5406(86)90107-1] [PMID: 3466528]
] declared that chin-cups accelerate the mesial movement of maxillary molars, without any effect on their eruption rate, while Wendell et al. [27Wendell PD, Nanda R, Sakamoto T, Nakamura S. The effects of chin cup therapy on the mandible: a longitudinal study. Am J Orthod 1985; 87(4): 265-74.
[http://dx.doi.org/10.1016/0002-9416(85)90001-6] [PMID: 3857003]
] manifested that the initial Class III occlusion was corrected to Class I relationship in all of the patients.

Soft-Tissue Effects

The effects of chin-cup therapy on the soft tissues were reported in five studies [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 19Akin M, Ucar FI, Chousein C, Sari Z. Effects of chincup or facemask therapies on the orofacial airway and hyoid position in Class III subjects. J Orofac Orthop 2015; 76(6): 520-30.
[http://dx.doi.org/10.1007/s00056-015-0315-3] [PMID: 26446505]
, 21Barrett AA, Baccetti T, McNamara JA Jr. Treatment effects of the light-force chincup. Am J Orthod Dentofacial Orthop 2010; 138(4): 468-76.
[http://dx.doi.org/10.1016/j.ajodo.2008.12.024] [PMID: 20889053]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
, 28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
]. Significant forward movement of the upper lip was declared in four studies [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 19Akin M, Ucar FI, Chousein C, Sari Z. Effects of chincup or facemask therapies on the orofacial airway and hyoid position in Class III subjects. J Orofac Orthop 2015; 76(6): 520-30.
[http://dx.doi.org/10.1007/s00056-015-0315-3] [PMID: 26446505]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
, 28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
] with a concomitant forward movement of the soft-tissue point A [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
], while the movement of the lower lip presented differing results. Arman et al. [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
], Alacrόn et al. [28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
] and Barrett et al. [21Barrett AA, Baccetti T, McNamara JA Jr. Treatment effects of the light-force chincup. Am J Orthod Dentofacial Orthop 2010; 138(4): 468-76.
[http://dx.doi.org/10.1016/j.ajodo.2008.12.024] [PMID: 20889053]
] stated a decreased distance of the lower lip to E plane (LL-E Ricketts line [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 21Barrett AA, Baccetti T, McNamara JA Jr. Treatment effects of the light-force chincup. Am J Orthod Dentofacial Orthop 2010; 138(4): 468-76.
[http://dx.doi.org/10.1016/j.ajodo.2008.12.024] [PMID: 20889053]
, 28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
]) and lower lip’s retraction (LL-VR [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
]) with a concomitant backward movement of the soft-tissue point B [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
] and the soft chin (Pg(s) [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
]). However, Abu Alhaija and Richardson [24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
] showed significant forward movement of the lower lip [24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
]. A general soft-tissue facial profile improvement was attributed to the chin-cup by Alacrόn et al. [28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
], who demonstrated similar correlations between the changes in the hard and in the soft tissues, especially the one between a significant reduction of the facial convexity angle and a significant pogonion retrusion in the chin-cup group.

Stability

Two studies [23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
] reported information concerning the stability of treatment outcomes, using cephalometric x-rays at a post-treatment observation. Abu Alhaija and Richardson et al. [24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
], following a one-year post-treatment cephalometric observation, reported a significant increase in mandibular length, which was in accordance with Sakamoto et al. [23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
], whose study found a forward displacement of the mandible in one-year post-treatment observation and total relapse in the original mandibular growth pattern after two years. Both studies [23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
] showed a significant increase in the anterior face height.

As for the dental effects, the significantly increased overjet achieved by chin-cups was maintained one year after the end of the treatment [24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
].

Although stability in the soft-tissue profile was evident at the post-treatment observation, the upper, the lower lip and the chin continued to grow forward following the skeletal pattern [24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
].

Quality Analysis

The overall judgement for the risk of bias was found serious for all the retrieved studies, (Table 4). All had a serious risk of bias concerning the selection of participants into the study (selection bias). Based on the ACROBAT-NRSI [13Sterne JAC, Higgins JPT, Reeves BC, et al. On behalf of the development group for ACROBAT-NRSI. A Cochrane Risk of Bias Assessment Tool for Non-randomized Studies of Interventions (ACROBAT- NRSI), Version 1.0.0, 2014 September 24; [accessed 2015 November 27] Available from: http://www.riskofbias.info ], all the studies were found to have some important problems in the corresponding domains, indicating cautious interpretation of the reported results.

DISCUSSION

In this systematic review, our primary goal was to search the existing literature for randomized and control clinical trials regarding the short- and long-term effects of chin-cup therapy on hard and soft tissues of growing patients. These had to include untreated patients as controls.

Table 4
Risk of bias assessment (ACROBAT-NRSI).


Although this was not the first time that this issue has been addressed in the literature, researchers in previous systematic reviews did not investigate the long-term effects of chin-cup therapy [2Liu ZP, Li CJ, Hu HK, Chen JW, Li F, Zou SJ. Efficacy of short-term chincup therapy for mandibular growth retardation in Class III malocclusion. Angle Orthod 2011; 81(1): 162-8.
[http://dx.doi.org/10.2319/050510-244.1] [PMID: 20936970]
, 10Chatzoudi MI, Ioannidou-Marathiotou I, Papadopoulos MA. Clinical effectiveness of chin cup treatment for the management of Class III malocclusion in pre-pubertal patients: a systematic review and meta-analysis. Prog Orthod 2014; 15: 62.
[http://dx.doi.org/10.1186/s40510-014-0062-9] [PMID: 25679781]
, 12Watkinson S, Harrison JE, Furness S, Worthington HV. Orthodontic treatment for prominent lower front teeth (Class III malocclusion) in children. Cochrane Database Syst Rev 2013; 9(9): CD003451.
[http://dx.doi.org/10.1002/14651858.CD003451.pub2] [PMID: 24085611]
], the soft tissue changes [2Liu ZP, Li CJ, Hu HK, Chen JW, Li F, Zou SJ. Efficacy of short-term chincup therapy for mandibular growth retardation in Class III malocclusion. Angle Orthod 2011; 81(1): 162-8.
[http://dx.doi.org/10.2319/050510-244.1] [PMID: 20936970]
, 10Chatzoudi MI, Ioannidou-Marathiotou I, Papadopoulos MA. Clinical effectiveness of chin cup treatment for the management of Class III malocclusion in pre-pubertal patients: a systematic review and meta-analysis. Prog Orthod 2014; 15: 62.
[http://dx.doi.org/10.1186/s40510-014-0062-9] [PMID: 25679781]
, 12Watkinson S, Harrison JE, Furness S, Worthington HV. Orthodontic treatment for prominent lower front teeth (Class III malocclusion) in children. Cochrane Database Syst Rev 2013; 9(9): CD003451.
[http://dx.doi.org/10.1002/14651858.CD003451.pub2] [PMID: 24085611]
] and the adolescence as a study growth period [10Chatzoudi MI, Ioannidou-Marathiotou I, Papadopoulos MA. Clinical effectiveness of chin cup treatment for the management of Class III malocclusion in pre-pubertal patients: a systematic review and meta-analysis. Prog Orthod 2014; 15: 62.
[http://dx.doi.org/10.1186/s40510-014-0062-9] [PMID: 25679781]
].

Our search strategy resulted in only CCTs, thirteen of retrospective [8Ritucci R, Nanda R. The effect of chin cup therapy on the growth and development of the cranial base and midface. Am J Orthod Dentofacial Orthop 1986; 90(6): 475-83.
[http://dx.doi.org/10.1016/0889-5406(86)90107-1] [PMID: 3466528]
, 17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
-28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
] and one of prospective design [29Gökalp H, Kurt G. Magnetic resonance imaging of the condylar growth pattern and disk position after chin cup therapy: a preliminary study. Angle Orthod 2005; 75(4): 568-75.
[PMID: 16097225]
], with no RCT found. One possible reason is that RCTs are not common in orthodontics, since various parameters are required. These include patient/observer blinding to treatment and ethical matters regarding the control group whose decision of participation is negatively affected by receiving no treatment.

The final studies were cohort studies with weaknesses due to the serious risk of bias, as it is described in detail in Table 4. All the studies were found to have selection bias, as the selection of both participants and controls was related to the received intervention and likely to the outcomes.

Furthermore, the studies were judged to have a serious risk of bias concerning the outcomes’ measurements when the knowledge of the received intervention by the assessors was likely to influence the outcomes in a way that it could cause statistically significant differences. Thus, three studies [8Ritucci R, Nanda R. The effect of chin cup therapy on the growth and development of the cranial base and midface. Am J Orthod Dentofacial Orthop 1986; 90(6): 475-83.
[http://dx.doi.org/10.1016/0889-5406(86)90107-1] [PMID: 3466528]
, 23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
, 27Wendell PD, Nanda R, Sakamoto T, Nakamura S. The effects of chin cup therapy on the mandible: a longitudinal study. Am J Orthod 1985; 87(4): 265-74.
[http://dx.doi.org/10.1016/0002-9416(85)90001-6] [PMID: 3857003]
] received that characterization, as the way that the outcome measure was conducted, was considered to have the potential to significantly affect the outcomes. The risk of bias was judged low, when blinding of outcome assessors was reported [25Alarcón JA, Bastir M, Rosas A, Molero J. Chincup treatment modifies the mandibular shape in children with prognathism. Am J Orthod Dentofacial Orthop 2011; 140(1): 38-43.
[http://dx.doi.org/10.1016/j.ajodo.2009.10.046] [PMID: 21724085]
, 28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
]. These studies were considered comparable to a well-performed randomized trial with regard to this domain, according to the ACROBAT-NRSI [13Sterne JAC, Higgins JPT, Reeves BC, et al. On behalf of the development group for ACROBAT-NRSI. A Cochrane Risk of Bias Assessment Tool for Non-randomized Studies of Interventions (ACROBAT- NRSI), Version 1.0.0, 2014 September 24; [accessed 2015 November 27] Available from: http://www.riskofbias.info ]. Consequently, studies pertaining to neither categories, were judged to have a moderate risk of bias [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
-22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
, 26Deguchi T, McNamara JA. Craniofacial adaptations induced by chincup therapy in Class III patients. Am J Orthod Dentofacial Orthop 1999; 115(2): 175-82.
[http://dx.doi.org/10.1016/S0889-5406(99)70346-X] [PMID: 9971929]
, 29Gökalp H, Kurt G. Magnetic resonance imaging of the condylar growth pattern and disk position after chin cup therapy: a preliminary study. Angle Orthod 2005; 75(4): 568-75.
[PMID: 16097225]
]. Based on the ACROBAT-NRSI [13Sterne JAC, Higgins JPT, Reeves BC, et al. On behalf of the development group for ACROBAT-NRSI. A Cochrane Risk of Bias Assessment Tool for Non-randomized Studies of Interventions (ACROBAT- NRSI), Version 1.0.0, 2014 September 24; [accessed 2015 November 27] Available from: http://www.riskofbias.info ] in these studies the outcome measure was only minimally influenced by the awareness of the received intervention and any error in measuring the outcome was only minimally related to intervention status. The methods of outcome assessment were comparable across intervention groups both for the studies with a moderate and a low risk of bias.

Another weakness of the observational studies, both prospective and retrospective, is the presence of confounders. In the present systematic review, we considered confounders, all those factors that were possibly related to the chin-cup therapy and could cause significant changes in the results. Ethnicity was needed to be taken into account, as Class III malocclusion is more frequently seen in Asian populations [1Toffol LD, Pavoni C, Baccetti T, Franchi L, Cozza P. Orthopedic treatment outcomes in Class III malocclusion. A systematic review. Angle Orthod 2008; 78(3): 561-73.
[http://dx.doi.org/10.2319/030207-108.1] [PMID: 18416617]
, 7Zurfluh MA, Kloukos D, Patcas R, Eliades T. Effect of chin-cup treatment on the temporomandibular joint: a systematic review. Eur J Orthod 2015; 37(3): 314-24.
[http://dx.doi.org/10.1093/ejo/cju048] [PMID: 25179261]
, 14Miyajima K, McNamara JA Jr, Sana M, Murata S. An estimation of craniofacial growth in the untreated Class III female with anterior crossbite. Am J Orthod Dentofacial Orthop 1997; 112(4): 425-34.
[http://dx.doi.org/10.1016/S0889-5406(97)70051-9] [PMID: 9345155]
-16Ngan P. Early treatment of Class III malocclusion. Semin Orthod 2005; 11: 140-5.
[http://dx.doi.org/10.1053/j.sodo.2005.04.007]
] and consequently these patients may be more often treated with chin-cups. Moreover, patients of Asian ancestry may present different baseline characteristics, as well as a different growth pattern than other populations, thus significantly affecting the results. The age of the participants in relation to their skeletal maturity stage was also accounted for. This was mainly due the fact that the prepubertal patients may present different results from patients that are in the peak of their growth or later. Skeletal Class of malocclusion was considered a confounder when there was doubt on whether the treated and/or the control group had skeletal Class III malocclusion or when some controls had skeletal Class I. Soft-tissue individual variation in thickness and in tension was co-estimated, since it could affect the reported results regarding the soft-tissue changes, as it was highlighted by Arman et al. [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
] and Alacrόn et al. [28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
]. Finally, pre-treatment overjet was also considered a confounder.

In addition, co-interventions were addressed. More specifically, the use of additional appliances, such as a lingual arch to flare the maxillary incisors [23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
, 26Deguchi T, McNamara JA. Craniofacial adaptations induced by chincup therapy in Class III patients. Am J Orthod Dentofacial Orthop 1999; 115(2): 175-82.
[http://dx.doi.org/10.1016/S0889-5406(99)70346-X] [PMID: 9971929]
] or a quad-helix appliance [21Barrett AA, Baccetti T, McNamara JA Jr. Treatment effects of the light-force chincup. Am J Orthod Dentofacial Orthop 2010; 138(4): 468-76.
[http://dx.doi.org/10.1016/j.ajodo.2008.12.024] [PMID: 20889053]
] were considered critically important co-interventions that could significantly alter the outcomes. To illustrate this, in four studies [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 19Akin M, Ucar FI, Chousein C, Sari Z. Effects of chincup or facemask therapies on the orofacial airway and hyoid position in Class III subjects. J Orofac Orthop 2015; 76(6): 520-30.
[http://dx.doi.org/10.1007/s00056-015-0315-3] [PMID: 26446505]
, 20Lin HC, Chang HP, Chang HF. Treatment effects of occipitomental anchorage appliance of maxillary protraction combined with chincup traction in children with Class III malocclusion. J Formos Med Assoc 2007; 106(5): 380-91.
[http://dx.doi.org/10.1016/S0929-6646(09)60323-5] [PMID: 17561473]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
] the declared proclination of the upper incisors [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 19Akin M, Ucar FI, Chousein C, Sari Z. Effects of chincup or facemask therapies on the orofacial airway and hyoid position in Class III subjects. J Orofac Orthop 2015; 76(6): 520-30.
[http://dx.doi.org/10.1007/s00056-015-0315-3] [PMID: 26446505]
, 20Lin HC, Chang HP, Chang HF. Treatment effects of occipitomental anchorage appliance of maxillary protraction combined with chincup traction in children with Class III malocclusion. J Formos Med Assoc 2007; 106(5): 380-91.
[http://dx.doi.org/10.1016/S0929-6646(09)60323-5] [PMID: 17561473]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
] followed by forward movement of the soft-tissue point A [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
] and the upper lip [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 19Akin M, Ucar FI, Chousein C, Sari Z. Effects of chincup or facemask therapies on the orofacial airway and hyoid position in Class III subjects. J Orofac Orthop 2015; 76(6): 520-30.
[http://dx.doi.org/10.1007/s00056-015-0315-3] [PMID: 26446505]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
] was probably the result of an additional occlusal bite plate [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 19Akin M, Ucar FI, Chousein C, Sari Z. Effects of chincup or facemask therapies on the orofacial airway and hyoid position in Class III subjects. J Orofac Orthop 2015; 76(6): 520-30.
[http://dx.doi.org/10.1007/s00056-015-0315-3] [PMID: 26446505]
], an upper removable appliance [24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
] and of the combination of maxillary protraction and chin-cup traction in an occipitomental anchorage appliance [20Lin HC, Chang HP, Chang HF. Treatment effects of occipitomental anchorage appliance of maxillary protraction combined with chincup traction in children with Class III malocclusion. J Formos Med Assoc 2007; 106(5): 380-91.
[http://dx.doi.org/10.1016/S0929-6646(09)60323-5] [PMID: 17561473]
]. The significantly increased overjet [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 19Akin M, Ucar FI, Chousein C, Sari Z. Effects of chincup or facemask therapies on the orofacial airway and hyoid position in Class III subjects. J Orofac Orthop 2015; 76(6): 520-30.
[http://dx.doi.org/10.1007/s00056-015-0315-3] [PMID: 26446505]
-21Barrett AA, Baccetti T, McNamara JA Jr. Treatment effects of the light-force chincup. Am J Orthod Dentofacial Orthop 2010; 138(4): 468-76.
[http://dx.doi.org/10.1016/j.ajodo.2008.12.024] [PMID: 20889053]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
] that was noted, was expected to be a result of the aforementioned additional appliances. However, it was also reported in studies where patients, treated solely with chin-cups, were contrasted to untreated controls [8Ritucci R, Nanda R. The effect of chin cup therapy on the growth and development of the cranial base and midface. Am J Orthod Dentofacial Orthop 1986; 90(6): 475-83.
[http://dx.doi.org/10.1016/0889-5406(86)90107-1] [PMID: 3466528]
, 28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
, 29Gökalp H, Kurt G. Magnetic resonance imaging of the condylar growth pattern and disk position after chin cup therapy: a preliminary study. Angle Orthod 2005; 75(4): 568-75.
[PMID: 16097225]
]. One possible reason is the occlusal interferences in the transition of the occlusion from a one with underjet to one with overjet [8Ritucci R, Nanda R. The effect of chin cup therapy on the growth and development of the cranial base and midface. Am J Orthod Dentofacial Orthop 1986; 90(6): 475-83.
[http://dx.doi.org/10.1016/0889-5406(86)90107-1] [PMID: 3466528]
], that flare the upper incisors. It could also be the result of the significant retroclination of lower incisors caused by the chin-cup [8Ritucci R, Nanda R. The effect of chin cup therapy on the growth and development of the cranial base and midface. Am J Orthod Dentofacial Orthop 1986; 90(6): 475-83.
[http://dx.doi.org/10.1016/0889-5406(86)90107-1] [PMID: 3466528]
, 22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
]. At last, utilization of force magnitude was considered a co-intervention as well, since significant reduction in ramus height was noted when lighter force in chin-cup traction was used [22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
].

Patients under chin-cup therapy showed an improved facial profile, merely induced by the backward and downward rotation of the mandible [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
-20Lin HC, Chang HP, Chang HF. Treatment effects of occipitomental anchorage appliance of maxillary protraction combined with chincup traction in children with Class III malocclusion. J Formos Med Assoc 2007; 106(5): 380-91.
[http://dx.doi.org/10.1016/S0929-6646(09)60323-5] [PMID: 17561473]
, 26Deguchi T, McNamara JA. Craniofacial adaptations induced by chincup therapy in Class III patients. Am J Orthod Dentofacial Orthop 1999; 115(2): 175-82.
[http://dx.doi.org/10.1016/S0889-5406(99)70346-X] [PMID: 9971929]
, 28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
]. This was documented by a decrease in the SNB [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
-22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
] and closure of the gonial angle [20Lin HC, Chang HP, Chang HF. Treatment effects of occipitomental anchorage appliance of maxillary protraction combined with chincup traction in children with Class III malocclusion. J Formos Med Assoc 2007; 106(5): 380-91.
[http://dx.doi.org/10.1016/S0929-6646(09)60323-5] [PMID: 17561473]
, 23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
, 25Alarcón JA, Bastir M, Rosas A, Molero J. Chincup treatment modifies the mandibular shape in children with prognathism. Am J Orthod Dentofacial Orthop 2011; 140(1): 38-43.
[http://dx.doi.org/10.1016/j.ajodo.2009.10.046] [PMID: 21724085]
, 26Deguchi T, McNamara JA. Craniofacial adaptations induced by chincup therapy in Class III patients. Am J Orthod Dentofacial Orthop 1999; 115(2): 175-82.
[http://dx.doi.org/10.1016/S0889-5406(99)70346-X] [PMID: 9971929]
]. It was also correlated with an increase in the anterior facial height [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 18Tuncer BB, Kaygisiz E, Tuncer C, Yüksel S. Pharyngeal airway dimensions after chin cup treatment in Class III malocclusion subjects. J Oral Rehabil 2009; 36(2): 110-7.
[http://dx.doi.org/10.1111/j.1365-2842.2008.01910.x] [PMID: 19522895]
, 22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
, 24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
]. In contrast, Wendell et al. [27Wendell PD, Nanda R, Sakamoto T, Nakamura S. The effects of chin cup therapy on the mandible: a longitudinal study. Am J Orthod 1985; 87(4): 265-74.
[http://dx.doi.org/10.1016/0002-9416(85)90001-6] [PMID: 3857003]
] recorded significant decreases in the anterior face height during chin-cup therapy in comparison with untreated controls. This was attributed to the 43% decrease in the downward displacement of pogonion during treatment, which was not stable at the post-treatment observation, when it was increased by 60% [27Wendell PD, Nanda R, Sakamoto T, Nakamura S. The effects of chin cup therapy on the mandible: a longitudinal study. Am J Orthod 1985; 87(4): 265-74.
[http://dx.doi.org/10.1016/0002-9416(85)90001-6] [PMID: 3857003]
]. The backward and downward rotation of the mandible was correlated with an increase in the ANB angle as well [17Arman A, Toygar TU, Abuhijleh E. Profile changes associated with different orthopedic treatment approaches in Class III malocclusions. Angle Orthod 2004; 74(6): 733-40.
[PMID: 15673133]
, 19Akin M, Ucar FI, Chousein C, Sari Z. Effects of chincup or facemask therapies on the orofacial airway and hyoid position in Class III subjects. J Orofac Orthop 2015; 76(6): 520-30.
[http://dx.doi.org/10.1007/s00056-015-0315-3] [PMID: 26446505]
, 21Barrett AA, Baccetti T, McNamara JA Jr. Treatment effects of the light-force chincup. Am J Orthod Dentofacial Orthop 2010; 138(4): 468-76.
[http://dx.doi.org/10.1016/j.ajodo.2008.12.024] [PMID: 20889053]
-23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
]. However, there is ambiguity in whether only the mandible or both the mandible and the maxilla are responsible for this.

Moreover, there is controversy among researchers regarding the retardation of the mandibular growth during chin-cup therapy. A significant reduction of the mandibular length (ramal, body and total length) was reported in five studies [22Abdelnaby YL, Nassar EA. Chin cup effects using two different force magnitudes in the management of Class III malocclusions. Angle Orthod 2010; 80(5): 957-62.
[http://dx.doi.org/10.2319/022210-110.1] [PMID: 20578869]
, 23Sakamoto T, Iwase I, Uka A, Nakamura S. A roentgenocephalometric study of skeletal changes during and after chin cup treatment. Am J Orthod 1984; 85(4): 341-50.
[http://dx.doi.org/10.1016/0002-9416(84)90191-X] [PMID: 6608880]
, 26Deguchi T, McNamara JA. Craniofacial adaptations induced by chincup therapy in Class III patients. Am J Orthod Dentofacial Orthop 1999; 115(2): 175-82.
[http://dx.doi.org/10.1016/S0889-5406(99)70346-X] [PMID: 9971929]
-28Alarcón JA, Requena MA, Delgado AC, González E, Martín C. Association between changes in soft and hard tissue after early chin cup treatment. J Orofac Orthop 2015; 76(3): 225-39.
[http://dx.doi.org/10.1007/s00056-015-0286-4] [PMID: 25929711]
] indicating an improvement in the skeletal profile of the treated patients. Most interesting were the findings of Wendell et al. [27Wendell PD, Nanda R, Sakamoto T, Nakamura S. The effects of chin cup therapy on the mandible: a longitudinal study. Am J Orthod 1985; 87(4): 265-74.
[http://dx.doi.org/10.1016/0002-9416(85)90001-6] [PMID: 3857003]
], whose study presented a reduction in absolute mandibular length, which continued after the end of the active treatment. In contrast, the studies of Gökalp and Kurt [29Gökalp H, Kurt G. Magnetic resonance imaging of the condylar growth pattern and disk position after chin cup therapy: a preliminary study. Angle Orthod 2005; 75(4): 568-75.
[PMID: 16097225]
] and Abu Alhaija and Richardson [24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
] showed significantly increased mandibular body [24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
, 29Gökalp H, Kurt G. Magnetic resonance imaging of the condylar growth pattern and disk position after chin cup therapy: a preliminary study. Angle Orthod 2005; 75(4): 568-75.
[PMID: 16097225]
] and total mandibular length [24Abu Alhaija ES, Richardson A. Long-term effect of the chincap on hard and soft tissues. Eur J Orthod 1999; 21(3): 291-8.
[http://dx.doi.org/10.1093/ejo/21.3.291] [PMID: 10407538]
]. Gökalp and Kurt [29Gökalp H, Kurt G. Magnetic resonance imaging of the condylar growth pattern and disk position after chin cup therapy: a preliminary study. Angle Orthod 2005; 75(4): 568-75.
[PMID: 16097225]
] attributed these alterations in the forward bending of the condyle, as a result of bone deposition between the condylar head and neck during chin-cup therapy.

The aforementioned controversy led to further investigating attempts by researchers in order to elucidate the role of chin-cup therapy in the retardation of mandibular growth. Similar attempts were also made to assess the potential influence of chin-cup therapy in the appearance of Temporomandibular Joint Disorders (TMD). It has been speculated that internal derangement of the TMJ is likely to occur due to the direct application of the backward chin-cup’s force on the mandibular condyle [7Zurfluh MA, Kloukos D, Patcas R, Eliades T. Effect of chin-cup treatment on the temporomandibular joint: a systematic review. Eur J Orthod 2015; 37(3): 314-24.
[http://dx.doi.org/10.1093/ejo/cju048] [PMID: 25179261]
]. This was recently evaluated in a systematic review [7Zurfluh MA, Kloukos D, Patcas R, Eliades T. Effect of chin-cup treatment on the temporomandibular joint: a systematic review. Eur J Orthod 2015; 37(3): 314-24.
[http://dx.doi.org/10.1093/ejo/cju048] [PMID: 25179261]
] by Zurfluh et al. who, interestingly, concluded that despite the craniofacial adaptations induced by chin-cups in patients with Class III malocclusion, chin-cup therapy does not constitute a risk factor for the development of TMD, as the existence of insufficient or low-quality evidence in the literature do not allow clear statements regarding the influence of chin-cup treatment on the TMJ. Nevertheless, they related TMD with age and a stressful lifestyle that seem to differentiate the effects imposed on TMJ.

As for the soft-tissue effects, although confounding was evident, the documented results indicate a general soft-tissue profile improvement when the chin-cup is used in skeletal Class III patients. However, in the lack of studies that evaluate the long-term stability of the aforementioned changes, no definite conclusions can be reached.

In the basis of these manifestations, it is evident that the effects of chin-cup therapy both in the short-and especially in the long-term need further investigation and better substantiation with more high-quality evidence to draw reliable conclusions.

CONCLUSION

In summary, the present systematic review shows that the chin-cup therapy can be considered for the short-term treatment of growing patients with Class III malocclusion. More specifically, the following are evident:

  • The skeletal profile is improved, as it is confirmed by significant changes in measured variables, which indicate a downward and backward rotation of the mandible.
  • Favorable dento-alveolar changes, such as a significant increase in overjet are also observed. However, data need to be carefully interpreted in the presence of co-interventions, such as additional appliances that could have an impact on the outcomes.
  • The soft tissues show a general improvement in the facial profile, following the accompanying skeletal and dento-alveolar changes, but with uncertain long-term stability.

Nevertheless, existing limitations that do not permit a clear judgement need to be taken into account. The unclear role of chin-cup therapy in the retardation of mandibular growth, the need for further investigation of the long-term effectiveness and the general lack of high quality evidence suggest cautious interpretation of the reported findings and highlight the need for future research with more high-quality evidence-based clinical trials, in order to draw reliable conclusions.

CONFLICT OF INTEREST

The authors confirm that this article content has no conflict of interest.

ACKNOWLEDGEMENTS

Declared none.

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