An observational study in Malocclusion, Angle Class II, Overbite (Excessive) Horizontal and Overbite (Excessive) Deep, sponsored by Region Jönköping County. Enrolling by invitation at 1 site in Sweden. Per ClinicalTrials.gov, last updated 2026-08-07.
Sponsored by Region Jönköping County · Observational
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:
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.
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.
124 studies on the registry are indexed under Malocclusion, Angle Class II; 19 are open to participants now.
Browse Malocclusion, Angle Class II studies →Region Jönköping County is the lead sponsor of 16 studies on the registry; 6 are open to participants now.
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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.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
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
Patients that recieved treatment with Twin block, without having recieved additional treatment afterwards.
Patients that recieved treatment with Twin block and then also required additional treatment afterwards.
Difference in horisontal overjet
The difference in horisontal overjet measured in millimeters at follow up (T2), compared with pre- (T0) and post-treatment (T1) values.
Time frame: From enrollment (T0) to follow up (T2), about 6 years later.
Molar relationship
Molar relationship at follow-up (T2), compared to molar relationship pre-(T0) and post-treatment (T1).
Time frame: From enrollment (T0) to follow up (T2), about 6 years later.
Overbite
The difference in vertical overjet measured in millimeters at follow up (T2), compared with pre- (T0) and post-treatment (T1) values.
Time frame: From enrollment (T0) to follow up (T2), about 6 years later.
Cephalometric data
Comparing cephalometric values of SNA, SNB and ANB pre- (T0), post-treatment (T1) and at follow-up (T2).
Time frame: From enrollment (T0) to follow up (T2), about 6 years later.
Plan to share: Undecided — Data collection is not yet complete.
Started Jul 2026 (actual). Primary completion is estimated for Aug 2026, 1 month after the start.
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Malocclusion, Angle Class II →
Region Jönköping County