Long-term Stability of Treatment With the Twin Block Appliance

August 3, 2026 updated by: Region Jönköping County

The objective of this observational study is to investigate the long-term stability of treatment with the Twin block appliance in a patient group previously treated with a Twin block appliance. The main questions it aims to answer are:

  1. Does treatment with the Twin block appliance give a lasting treatment result or does the bite relapse over time due to different factors such as short treatment time, compliance or the patient's natural growth pattern?
  2. How many patients that had received treatment with Twin block appliance required additional treatment with fixed appliances and for what reason?

Researchers will compare the patients present bite at (T2) by using study casts and cephalometric x-rays and compare this data with previous registrations made pre- (T0) and post-treatment (T1). Additional factors, such as how much relapse a patient has on average, will also be investigated.

Study Overview

Status

Enrolling by invitation

Conditions

Detailed Description

Orthodontic treatment during growth is called interceptive orthodontics. The objective is to affect the growth of the jaws and the position of the teeth with the assistance of a removable orthodontic appliance. One such appliance is the Twin block appliance, which is used to treat patients with an Angle class II malocclusion (Clark et al., 2022). The prevalence of Angle class II malocclusion is approximately 25% (Proffit et al., 2013).

There is however a lack of studies on the long term treatment stability of the Twin block appliance (Ehsani et al., 2015). Treatment with removable appliances also carry a great cost for both the individual, the parents and for society as a whole (Permert et al., 1998). The objective of the present study is to present guidelines concerning which patients that would benefit the most from treatment with Twin block appliance over time.

The present study will use a previous patient material consisting of 72 patients from the study by Frilund et al., (2023) "Patient compliance with Twin Block appliance during treatment of Class II malocclusion: a randomized controlled trial on two check-up prescriptions" to review the long term stability of treatment with Twin block appliance. These 72 patients were previously treated with a Twin block appliance. Their records will be reviewed to find patients who have had no additional orthodontic treament, and these patients will be asked to participate in the present study. If they accept, their present bite (T2) will be registered by study casts and with a cephalometric x-ray. This data (T2) will then be compared with their study casts and cephalometric data before treatment start (T0) and after treatment (T1). The main variables that will be investigated are overjet, overbite and molar relationship, as well as cephalometric values. The collected material will also be dichotomized into two groups, one with optimal current status with a neutral molar relation and a horizontal overjet of 4 mm or less, and one with a suboptimal current status presenting an angle class II molar relationship and/or an overjet greater that 4 mm.

The patients that recieved additional orthodontic treatment after their treatment with Twin block appliance will also be investigated to compare the reason for them having additional treatment and to investigate if the primary reason was relapse or other additional factors.

Statistical analysis of collected data will be perfofmed with the appropriate stastical models, depending on if the data has a normal distribution or not.

The study has recieved ethical approval from the ethical board at the University of Linköping, Dnr 2025-08312-02. All patients will have to give their informed consent to participate in the study by signing a consent form.

Results will be published in appropriate medical journals and at interdisciplinary conferences and lectures.

Study Type

Observational

Enrollment (Estimated)

72

Contacts and Locations

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

Study Locations

  • Sweden
    • Jönköping County
      • Jönköping, Jönköping County, Sweden, 551 11
        • The Institute of Postgraduate Dental Education

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
  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

The patient cohort was originally recruited and treated from December 2018 to October 2020 The inclusion criteria for the previous study were healthy patients according to the American Society of Anaesthesiology Classification (ASA I and II), aged 8-14 years at treatment start and with an overjet of 6 mm or more together with an incomplete lip closure.

Exclusion criteria were severe chronic conditions such as asthma and allergy, neuropsychiatric disorders, craniofacial syndromes, and previous orthodontic treatment. Recruitment of the patients continued until the number of participants met the estimated sample size.

This patient group were then contacted again for recruitement to the present study during June 2026 to August 2026.

Description

Inclusion Criteria:

Patient participated in the previous study "Patient compliance with Twin Block appliance during treatment of Class II malocclusion: a randomized controlled trial on two check-up prescriptions" .Eur J Orthod. 2023. https://doi.org/10.1093/ejo/cjac046

Exclusion Criteria:

None

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

Cohorts and Interventions

Group / Cohort
Long term follow-up without additional orthodontic treatment
Patients that recieved treatment with Twin block, without having recieved additional treatment afterwards.
Long term follow-up with additional orthodontic treatment
Patients that recieved treatment with Twin block and then also required additional treatment afterwards.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Difference in horisontal overjet
Time Frame: From enrollment (T0) to follow up (T2), about 6 years later.
The difference in horisontal overjet measured in millimeters at follow up (T2), compared with pre- (T0) and post-treatment (T1) values.
From enrollment (T0) to follow up (T2), about 6 years later.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Molar relationship
Time Frame: From enrollment (T0) to follow up (T2), about 6 years later.
Molar relationship at follow-up (T2), compared to molar relationship pre-(T0) and post-treatment (T1).
From enrollment (T0) to follow up (T2), about 6 years later.
Overbite
Time Frame: From enrollment (T0) to follow up (T2), about 6 years later.
The difference in vertical overjet measured in millimeters at follow up (T2), compared with pre- (T0) and post-treatment (T1) values.
From enrollment (T0) to follow up (T2), about 6 years later.
Cephalometric data
Time Frame: From enrollment (T0) to follow up (T2), about 6 years later.
Comparing cephalometric values of SNA, SNB and ANB pre- (T0), post-treatment (T1) and at follow-up (T2).
From enrollment (T0) to follow up (T2), about 6 years later.

Collaborators and Investigators

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

Sponsor

Region Jönköping County

Investigators

  • Principal Investigator: Anders Magnusson, Med dr., Region Jönköping

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 (Actual)

July 10, 2026

Primary Completion (Estimated)

August 30, 2026

Study Completion (Estimated)

December 20, 2026

Study Registration Dates

First Submitted

August 3, 2026

First Submitted That Met QC Criteria

August 3, 2026

First Posted (Actual)

August 7, 2026

Study Record Updates

Last Update Posted (Actual)

August 7, 2026

Last Update Submitted That Met QC Criteria

August 3, 2026

Last Verified

July 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • Dnr 2025-08312-02

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

IPD Plan Description

Data collection is not yet complete.

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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