Efficacy of a modified twin block appliance compared with the traditional twin block appliance in children with hyperdivergent mandibular retrognathia: protocol for a single-centre, single-blind, randomised controlled trial

Anqi Liu; Wei Zhang; Weihua Zhang; Shuangshuang Shi; Zhuoyue Chen; Yuehua Liu; Yun Lu

doi:10.1136/bmjopen-2023-071959

Efficacy of a modified twin block appliance compared with the traditional twin block appliance in children with hyperdivergent mandibular retrognathia: protocol for a single-centre, single-blind, randomised controlled trial

BMJ Open. 2023 Nov 27;13(11):e071959. doi: 10.1136/bmjopen-2023-071959.

Authors

Anqi Liu^{1

2}, Wei Zhang³, Weihua Zhang^{1

2}, Shuangshuang Shi^{1

2}, Zhuoyue Chen^{1

2}, Yuehua Liu^{4

2}, Yun Lu^{4

2}

Affiliations

¹ Department of Orthodontics, Shanghai Stomatological Hospital & School of Stomatology, Fudan University, Shanghai, China.
² Shanghai Key Laboratory of Craniomaxillofacial Development and Diseases, Shanghai, China.
³ Biomedical Informatics & Statistics Center, School of Public Health, Fudan University, Shanghai, China.
⁴ Department of Orthodontics, Shanghai Stomatological Hospital & School of Stomatology, Fudan University, Shanghai, China luyun@fudan.edu.cn liuyuehua@fudan.edu.cn.

Abstract

Introduction: Compensatory mouth breathing, caused by nasopharyngeal obstructive diseases, is the main cause of hyperdivergent mandibular retrognathia in children. Such deformities require effective growth guidance before pubertal growth peaks. The traditional mandibular advancement device, twin block (TB), can guide the forward development of the mandible. However, the side effect of increasing the vertical dimension of the lower facial third, worsens the facial profile of children with divergent growth trends. To solve this problem, a modified TB (LLTB) appliance was designed to control the vertical dimension by intruding incisors and inhibiting the elongation of posterior teeth during the advancement of the mandible, which could avoid the side effects of traditional appliances and effectively guide the growth of the mandible in a normal direction.

Methods and analysis: The study was designed as a single-centre, single-blind, randomised, parallel controlled trial. We aim to enrol 60 children aged 9-14 years with hyperdivergent skeletal class II malocclusion, using a 1:1 allocation ratio. The participants were will be randomly assigned to receive either the TB or LLTB treatment. The primary outcome will be a change in the angle of the mandibular plane relative to the anterior cranial base. The secondary outcomes will include changes in the sagittal maxillomandibular relation, occlusal plane, facial height, morphology of the mandible and upper airway width. Safety endpoints will also be evaluated.

Ethics and dissemination: Ethical approval was obtained from the ethics committee of Shanghai Stomatological Hospital. Both participants and their guardians will be fully informed of the study and sign an informed consent form before participating in the trial. The results will be publicly available in peer-reviewed scientific journals.

Trial registration number: ChiCTR2000035882.

Keywords: ORAL MEDICINE; Paediatric oral & maxillofacial surgery; SLEEP MEDICINE.

Publication types

Clinical Trial Protocol
Research Support, Non-U.S. Gov't

MeSH terms

Cephalometry / methods
Child
China
Humans
Orthodontic Appliances, Functional*
Randomized Controlled Trials as Topic
Retrognathia* / therapy
Single-Blind Method
Treatment Outcome