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      Comparison of cephalometric measurements of the Twin Block and A6 appliances in the treatment of Class II malocclusion: a retrospective comparative cohort study

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          Abstract

          Background

          Skeletal Class II malocclusion is a common malocclusion that seriously affects patients’ profile and occlusal function. The key to treatment is to use functional appliances guide the mandible forward. This study aimed to evaluate the clinical efficacy of traditional functional appliance Twin Block (TB) and invisible functional appliance (A6).

          Methods

          In the retrospective cohort study, 46 patients with Class II Division 1 mandibular retrognathia (23 females, 23 males; mean age 13.66±4.25 years) from the Third Affiliated Hospital of Sun Yat-sen University were selected. They were divided into A6 group and TB group according to the type of appliance guided mandibular forward used in orthodontic treatment (n=23 each; average treatment time 9.82±3.52 months). Lateral cephalometric radiographs were taken before and at the end of each treatment, and paired t-test or paired rank-sum tests were performed when appropriate to detect any statistical significance at the level of α=0.05.

          Results

          The baseline characteristics of the two groups of patients were similar. Treatment with both appliances helped correct Class II malocclusion, improve the discrepancy between the maxilla and mandible, reduce the labial inclination of the maxillary anterior teeth, and relieve the deep overbite. A comparison of the treatment effects of the TB and A6 groups showed that the A6 had a better effect when moving Point A backward, and performed better in the abduction of the anterior teeth. TB group has more advantages than A6 group in moving forward point B and improving the nasolabial angle.

          Conclusions

          Both the A6 and TB can significantly improve Class II malocclusion. A6 showed an obvious advantage in moving Point A backward and adducting the anterior teeth, which better corrects a skeletal Class II malocclusion.

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          Most cited references35

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          Prevalence of malocclusion and orthodontic treatment need in the United States: estimates from the NHANES III survey.

          L J Moray, William R Proffit, H Fields (1997)
          Data from the third National Health and Nutrition Examination Survey (NHANES III) provide a clear picture of malocclusion in the US population. Noticeable incisor irregularity occurs in the majority of all racial/ethnic groups, with only 35% of adults having well-aligned mandibular incisors. Irregularity is severe enough in 15% that both social acceptability and function could be affected, and major arch expansion or extraction of some teeth would be required for correction. About 20% of the population have deviations from the ideal bite relationship; in 2% these are severe enough to be disfiguring and are at the limit for orthodontic correction. In Mexican-Americans compared to the rest of the population, incisor irregularity and both severe Class II and Class III malocclusions are more prevalent, but deep bite and open bite are less prevalent. Application of the Index of Treatment Need to the survey data reveals that 57% to 59% of each racial/ethnic group has at least some degree of orthodontic treatment need. Over 30% of white youths, 11% of Mexican-Americans, and 8% of blacks report receiving treatment. Severe malocclusion is observed more frequently among blacks, which may reflect their lower level of treatment. Treatment is much more frequent in higher income groups, but approximately 5% of those in the lowest income group and 10% to 15% of those in intermediate income groups report being treated.
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            Mandibular changes produced by functional appliances in Class II malocclusion: a systematic review.

            Paola Cozza, Tiziano Baccetti, Lorenzo Franchi … (2006)
            The aim of this systematic review of the literature was to assess the scientific evidence on the efficiency of functional appliances in enhancing mandibular growth in Class II subjects. A literature survey was performed by applying the Medline database (Entrez PubMed). The survey covered the period from January 1966 to January 2005 and used the medical subject headings (MeSH). The following study types that reported data on treatment effects were included: randomized clinical trials (RCTs), and prospective and retrospective longitudinal controlled clinical trials (CCTs) with untreated Class II controls. The search strategy resulted in 704 articles. After selection according to the inclusion/exclusion criteria, 22 articles qualified for the final analysis. Four RCTs and 18 CCTs were retrieved. The quality standards of these investigations ranged from low (3 studies) to medium/high (6 studies). Two-thirds of the samples in the 22 studies reported a clinically significant supplementary elongation in total mandibular length (a change greater than 2.0 mm in the treated group compared with the untreated group) as a result of overall active treatment with functional appliances. The amount of supplementary mandibular growth appears to be significantly larger if the functional treatment is performed at the pubertal peak in skeletal maturation. None of the 4 RCTs reported a clinically significant change in mandibular length induced by functional appliances; 3 of the 4 RCTs treated subjects at a prepubertal stage of skeletal maturity. The Herbst appliance showed the highest coefficient of efficiency (0.28 mm per month) followed by the Twin-block (0.23 mm per month).
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              Global distribution of malocclusion traits: A systematic review

              Maged Alhammadi, Esam Saleh Halboub, Mona Salah Fayed … (2018)
              Abstract Objective: Considering that the available studies on prevalence of malocclusions are local or national-based, this study aimed to pool data to determine the distribution of malocclusion traits worldwide in mixed and permanent dentitions. Methods: An electronic search was conducted using PubMed, Embase and Google Scholar search engines, to retrieve data on malocclusion prevalence for both mixed and permanent dentitions, up to December 2016. Results: Out of 2,977 retrieved studies, 53 were included. In permanent dentition, the global distributions of Class I, Class II, and Class III malocclusion were 74.7% [31 - 97%], 19.56% [2 - 63%] and 5.93% [1 - 20%], respectively. In mixed dentition, the distributions of these malocclusions were 73% [40 - 96%], 23% [2 - 58%] and 4% [0.7 - 13%]. Regarding vertical malocclusions, the observed deep overbite and open bite were 21.98% and 4.93%, respectively. Posterior crossbite affected 9.39% of the sample. Africans showed the highest prevalence of Class I and open bite in permanent dentition (89% and 8%, respectively), and in mixed dentition (93% and 10%, respectively), while Caucasians showed the highest prevalence of Class II in permanent dentition (23%) and mixed dentition (26%). Class III malocclusion in mixed dentition was highly prevalent among Mongoloids. Conclusion: Worldwide, in mixed and permanent dentitions, Angle Class I malocclusion is more prevalent than Class II, specifically among Africans; the least prevalent was Class III, although higher among Mongoloids in mixed dentition. In vertical dimension, open bite was highest among Mongoloids in mixed dentition. Posterior crossbite was more prevalent in permanent dentition in Europe.
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                Author and article information

                Journal
                Journal ID (nlm-ta): Ann Transl Med
                Journal ID (iso-abbrev): Ann Transl Med
                Journal ID (publisher-id): ATM
                Title: Annals of Translational Medicine
                Publisher: AME Publishing Company
                ISSN (Print): 2305-5839
                ISSN (Electronic): 2305-5847
                Publication date (Print and electronic): August 2022
                Publication date (Print): August 2022
                Volume: 10
                Issue: 16
                Electronic Location Identifier: 876
                Affiliations
                [1]deptDepartment of Orthodontics , The Third Affiliated Hospital of Sun Yat-sen University , Guangzhou, China
                Author notes

                Contributions: (I) Conception and design: Z Sun, Y Pan, Z Mai; (II) Administrative support: Z Mai, H Ai; (III) Provision of study materials or patients: T Lin, H Lu, H Ai, Z Mai; (IV) Collection and assembly of data: Z Sun, Y Pan; (V) Data analysis and interpretation: Z Sun, Y Pan, Z Mai; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors.

                [#]

                These authors contributed equally to this work.

                Correspondence to: Hong Ai. Department of Orthodontics, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou 510630, China. Email: aih-zssy09@ 123456126.com ; Zhihui Mai. Department of Orthodontics, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou 510630, China. Email: maiya2007@ 123456126.com .
                Article
                Publisher ID: atm-10-16-876
                DOI: 10.21037/atm-22-3762
                PMC ID: 9469128
                PubMed ID: 36111042
                SO-VID: 90b33984-8ea3-4ca6-91e5-4b9c1c2798a0
                Copyright © 2022 Annals of Translational Medicine. All rights reserved.
                License:

                Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0.

                History
                Date received : 23 June 2022
                Date accepted : 10 August 2022
                Categories
                Subject: Original Article

                Keywords: class ii malocclusion,functional appliance,invisible appliance without brackets,lateral cephalometric radiographs,mandibular advancement
                Data availability:
                Keywords: class ii malocclusion, functional appliance, invisible appliance without brackets, lateral cephalometric radiographs, mandibular advancement

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