Modified Versus Clear Twin Block for Skeletal Class II Malocclusion (MTB-CTB)

May 20, 2026 updated by: Feras baba, University of Aleppo

Evaluation of the Efficacy of Functional Therapy Using Modified Twin Block Versus Clear Twin Block in Class II Skeletal Patients: A Randomized Controlled Clinical Trial

This study aims to evaluate the effectiveness of a modified Twin Block appliance compared to a conventional clear Twin Block appliance in the treatment of skeletal Class II malocclusion caused by mandibular retrusion in growing patients.

This is a two-arm randomized controlled clinical trial including patients aged 10-13 years diagnosed with skeletal Class II malocclusion. Participants will be randomly allocated into two equal groups.

Skeletal, dental, and soft tissue changes will be assessed using lateral cephalometric analysis and cone-beam computed tomography (CBCT). Additionally, temporomandibular joint (TMJ) health, pain perception, and functional tolerance will be evaluated using standardized clinical indices and patient-reported outcome measures.

The study aims to compare the modified appliance with the conventional design in terms of skeletal improvement, TMJ safety, and patient acceptance.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Skeletal and dentofacial anomalies, particularly Class II malocclusion due to mandibular retrusion, represent one of the most prevalent orthodontic problems during growth. Functional appliances, especially the Twin Block appliance, are widely used to enhance mandibular development and correct jaw discrepancies. However, variations in treatment protocols, particularly regarding advancement mechanics and appliance modifications, may influence both skeletal outcomes and temporomandibular joint (TMJ) response.

This study aims to investigate the effects of a modified Twin Block appliance, incorporating progressive mandibular advancement and additional design modifications such as lower lip pads intended to influence muscular activity, compared to a conventional clear Twin Block appliance.

A two-arm randomized controlled trial will be conducted on growing patients aged 10-13 years diagnosed with skeletal Class II malocclusion due to mandibular retrusion. Participants will be randomly allocated into two equal groups using a computer-generated randomization sequence with allocation concealment.

Skeletal and dental changes will be evaluated using lateral cephalometric radiographs and cone-beam computed tomography (CBCT), with particular attention to condylar morphology, joint space dimensions, and craniofacial skeletal relationships. TMJ health will be assessed using the Helkimo Index. Patient comfort, pain perception, and functional adaptation will be evaluated using validated questionnaires administered at multiple time points throughout the treatment period.

Radiographic and clinical assessments will be performed at baseline (T0) and after 7 months of functional appliance therapy (T1). Repeated patient-reported outcome measures will be collected at predefined intervals during treatment.

The objective of this study is to determine whether the modified Twin Block appliance provides superior skeletal and functional outcomes while maintaining temporomandibular joint safety and improving patient tolerance compared to the conventional appliance.

Study Type

Interventional

Enrollment (Estimated)

40

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Child

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Systemically healthy patients.
  • Patients willing to accept removable functional appliance therapy.
  • Skeletal Class II malocclusion (Angle Class II Division 1).
  • Skeletal Class II due to mandibular retrusion (ANB > 5°, Wits appraisal > 5 mm, SNB < 78°, NSAr ≥ 125°, with normal maxillary position).
  • Normal or horizontal growth pattern (MM angle < 30° or Björk angle < 40°).
  • Growth stage corresponding to MP3 stage or pre-pubertal peak according to hand-wrist radiograph (Björk and Helm, 1967).
  • No severe dental crowding in the dental arches and no significant maxillary dental protrusion.
  • Absence of congenital anomalies, trauma, burns, or surgical scars affecting the temporomandibular joint or craniofacial structures.
  • Absence of systemic or rheumatologic diseases affecting the temporomandibular joint.

Exclusion Criteria:

  • Presence of clinical signs or symptoms of temporomandibular joint disorders.
  • Functional mandibular deviation.
  • Presence of unilateral or bilateral posterior crossbite.
  • Previous orthodontic treatment.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Modified Twin Block Group
Patients in this group will be treated using a modified Twin Block appliance incorporating progressive mandibular advancement and lower lip pads designed to influence muscular activity and enhance skeletal effects.
Device: Modified Twin Block Appliance
A modified Twin Block functional appliance incorporating progressive mandibular advancement and lower lip pads designed to modify muscular activity and enhance mandibular growth. The appliance is used for the treatment of skeletal Class II malocclusion due to mandibular retrusion in growing patients.
Other Names:
  • Progressive Twin Block
Active Comparator: Conventional Clear Twin Block Group
Patients in this group will be treated using a conventional clear Twin Block functional appliance for correction of skeletal Class II malocclusion.
Device: Conventional Clear Twin Block Appliance
A conventional clear Twin Block functional appliance used for correction of skeletal Class II malocclusion in growing patients. The appliance acts by posturing the mandible forward to stimulate functional and skeletal adaptation.
Other Names:
  • Clear Twin Block

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in mandibular skeletal position measured by SNB angle on lateral cephalometric radiographs
Time Frame: Baseline (T0) and after 7 months of treatment (T1)
Assessment of sagittal mandibular skeletal position using the SNB angle (degrees) measured on standardized lateral cephalometric radiographs.
Baseline (T0) and after 7 months of treatment (T1)
Change in effective mandibular length measured by Co-Gn distance on lateral cephalometric radiographs
Time Frame: Baseline (T0) and after 7 months of treatment (T1)
Assessment of mandibular length using the Condylion-Gnathion (Co-Gn) linear measurement in millimeters obtained from lateral cephalometric analysis.
Baseline (T0) and after 7 months of treatment (T1)
Change in condylar dimensions assessed using cone-beam computed tomography (CBCT)
Time Frame: Baseline (T0) and after 7 months of treatment (T1)
Assessment of temporomandibular condylar morphology using CBCT, including condylar length, condylar width, and condylar height measured in millimeters.
Baseline (T0) and after 7 months of treatment (T1)
Change in temporomandibular joint spaces assessed using CBCT
Time Frame: Baseline (T0) and after 7 months of treatment (T1)
Assessment of condylar position within the glenoid fossa using CBCT measurements of anterior joint space (AJS), superior joint space (SJS), posterior joint space (PJS), and medial joint space (MJS), measured in millimeters.
Baseline (T0) and after 7 months of treatment (T1)

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Temporomandibular joint dysfunction symptoms assessed using the Helkimo Anamnestic Index (Ai)
Time Frame: Baseline (T0) and after 7 months of treatment (T1)

Assessment of temporomandibular joint dysfunction symptoms using the Helkimo Anamnestic Index questionnaire. The index classifies patients into:

  • Ai0: no symptoms
  • Ai1: mild symptoms
  • Ai2: severe symptoms Higher scores indicate greater temporomandibular dysfunction severity.
Baseline (T0) and after 7 months of treatment (T1)
Patient-reported pain intensity assessed using a Numeric Rating Scale (NRS)
Time Frame: 1 week, 2 weeks, 6 weeks, 3 months, and 6 months after appliance insertion
Assessment of pain intensity reported by patients using a numeric rating scale ranging from 0 to 10, where 0 indicates no pain and 10 indicates maximum pain.
1 week, 2 weeks, 6 weeks, 3 months, and 6 months after appliance insertion
Patient-reported discomfort and functional limitation assessed using a validated questionnaire
Time Frame: 1 week, 2 weeks, 6 weeks, 3 months, and 6 months after appliance insertion
Assessment of appliance-related discomfort and functional or social impairment using a validated questionnaire adapted from Sergl and Zentner (1998), modified by Idris et al. (2012). The questionnaire evaluates pressure sensation, tooth sensitivity, speech impairment, swallowing difficulty, mouth restriction sensation, and social confidence using a numeric rating scale from 0 to 10. Higher scores indicate greater discomfort and poorer appliance acceptance.
1 week, 2 weeks, 6 weeks, 3 months, and 6 months after appliance insertion
Change in lower incisor inclination measured by IMPA on lateral cephalometric radiographs
Time Frame: Baseline (T0) and after 7 months of treatment (T1)
Assessment of lower incisor inclination using the Incisor Mandibular Plane Angle (IMPA) measured in degrees on lateral cephalometric radiographs.
Baseline (T0) and after 7 months of treatment (T1)
Change in upper incisor inclination measured by U1-SN angle on lateral cephalometric radiographs
Time Frame: Baseline (T0) and after 7 months of treatment (T1)
Assessment of upper incisor inclination using the upper incisor to SN plane angle (U1-SN) measured in degrees on lateral cephalometric radiographs.
Baseline (T0) and after 7 months of treatment (T1)
Change in overjet measured on lateral cephalometric radiographs
Time Frame: Baseline (T0) and after 7 months of treatment (T1)
Assessment of overjet as the horizontal distance between upper and lower incisors measured in millimeters on lateral cephalometric radiographs.
Baseline (T0) and after 7 months of treatment (T1)
Change in overbite measured on lateral cephalometric radiographs
Time Frame: Baseline (T0) and after 7 months of treatment (T1)
Assessment of overbite as the vertical overlap between upper and lower incisors measured in millimeters on lateral cephalometric radiographs.
Baseline (T0) and after 7 months of treatment (T1)
Change in sagittal molar relationship measured on lateral cephalometric radiographs
Time Frame: Baseline (T0) and after 7 months of treatment (T1)
Assessment of sagittal molar relationship using linear measurements in millimeters between upper and lower first molars on lateral cephalometric radiographs.
Baseline (T0) and after 7 months of treatment (T1)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Aleppo

Investigators

  • Study Director: Abdulmalek Majanni, PhD, Faculty of Dentistry, University of Aleppo

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

May 1, 2026

Primary Completion (Estimated)

December 1, 2026

Study Completion (Estimated)

December 1, 2026

Study Registration Dates

First Submitted

May 12, 2026

First Submitted That Met QC Criteria

May 20, 2026

First Posted (Actual)

May 27, 2026

Study Record Updates

Last Update Posted (Actual)

May 27, 2026

Last Update Submitted That Met QC Criteria

May 20, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • MClearTB
  • UADS-3478-26052024/SRC-1994 (Other Identifier: University of Aleppo Local Ethics Committee)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data will not be shared due to patient privacy and confidentiality considerations. The study involves pediatric orthodontic patients, and data will be reported in aggregate form only.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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