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Title Twin-Block Appliance Outperforms Dynamax Appliance For Class II, Division 1 Malocclusion
Clinical Question In a patient with a Class II, Division 1 malocclusion, is treatment using the Twin-block appliance superior to the Dynamax appliance for better occlusion and esthetics combined?
Clinical Bottom Line Better results are obtained using Twin-blocks than using Dynamax appliances for patients with Class II Division 1 malocclusion with an over-jet of 6mm or more.
Best Evidence (you may view more info by clicking on the PubMed ID link)
PubMed ID Author / Year Patient Group Study type
(level of evidence)
#1) 20691354Thiruvenkatachari B 201032 boys and 32 girls aged 10-14 YrsRandomized Controlled Trial
Key resultsAt 18 months, the Data Monitoring Committee terminated the Dynamax group due to significantly minimal over-jet and a greater incidence in adverse events and appliance breakage (Twin-block 16%; Dynamax 82%(p<0.001)). The greater increase in reversed over-jet in the Twin-block group was statistically significant (P = 0.04) at 9 months when compared with the Dynamax group. However, this difference was not evident at 12 months. Both groups experienced a similar degree of over-jet and reversed over-jet relapse (1 mm) between the withdrawal of the appliance (9 months) and the final collection of records (12 months).
#2) 17456506R. T. Lee 200728 boys between 11-14 years and 34 girls between 10-13 yearsRandomized Controlled Trial
Key resultsSkeletal, soft tissue and dental changes in the Twin-block and Dynamax groups were measured pre-and post treatment using three-dimensional optical surface laser scanning, cephalometric, and clinical features. Measurements were made at 3 month intervals with the final evaluations completed at 12 months. Twin-block therapy resulted in more antero-posterior skeletal change, median ANB reduction, larger increases in vertical facial dimension and median total anterior face height increase. A higher percentage of appliance breakage was noted in the Dynamax group (55%) compared to the Twin-block (35%).
Evidence Search malocclusion [MeSH Terms] AND Twin-block AND Dynamax
Comments on
The Evidence
A randomized controlled trial provides high level evidence. In the Thiruvenkatachari paper, a power analysis determined the size of the experimental groups and treatment was provided by 4 clinicians at 2 centers. Follow-up was every 6 weeks after appliance placement, and over-jet, overbite, molar width, and canine and molar relationship measurements were recorded. Patients were followed for 9 months.In the Lee paper, data were analyzed on an intention-to-treat basis, and the data monitoring committee (DMC) assessors were blinded to treatment allocation. A prospective project was reported. Subjects were matched for gender and age and randomly assigned to the two treatment groups. Group size was determined by conducting a power analysis. A high incidence of appliance breakage was reported in both papers, enough that the Dynamax arm of the Thiruvenkatachari study was terminated and those subjects were completed with Twin-block therapy or fixed appliances. Non-compliance was reported at 9% in both groups.
Applicability Patients with Class II, Division 1 malocclusion
Specialty/Discipline (Orthodontics)
Keywords Twin Blocks, Dynamax, malocclusion
ID# 2075
Date of submission: 07/08/2011spacer
E-mail faddoul@uthscsa.edu
Author Taoufik Faddoul
Co-author(s) e-mail
Faculty mentor/Co-author Stephen Matteson, DDS
Faculty mentor/Co-author e-mail MATTESON@uthscsa.edu
Basic Science Rationale
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Comments and Evidence-Based Updates on the CAT
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by Fauzia Dadarkar, DDS, Shadzi Jebraeili, DDS (San Antonio, TX) on 11/13/2015
A PubMed and Trip database search on this question in November 2015, found a more recent publication by Lee RT et. al (2014, PubMed ID: 23291502). This controlled clinical trial on 103 subjects used cephalograms and 3D optical laser scans, to analyze both the hard and soft tissue effects after 15-month full-time functional appliance therapy with Twin Block and Dynamax appliances. The changes observed were more pronounced with the Twin Block appliance. This study further strengthens the conclusions of this CAT.

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