Original article
Effectiveness of early orthodontic treatment with the twin-block appliance: A multicenter, randomized, controlled trial. Part 1: Dental and skeletal effects

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Abstract

This study evaluated the effectiveness of early orthodontic treatment with the Twin-block appliance for the developing Class II Division 1 malocclusion. This multicenter trial was carried out in the United Kingdom. A total of 174 children, aged 8 to 10 years old, with Class II Division 1 malocclusion were randomly allocated to receive treatment with a Twin-block appliance or to an untreated, control group. Data were collected at the start of the study and 15 months later. Results showed that early treatment with Twin-block appliances resulted in reduction of overjet, correction of molar relationships, and reduction in severity of malocclusion. Most of this correction was due to dentoalveolar change, but some was due to favorable skeletal change. Early treatment with the Twin-block appliance is effective in reducing overjet and severity of malocclusion. The small change in the skeletal relationship might not be considered clinically significant.

Section snippets

Material and methods

This investigation had the null hypotheses that orthodontic treatment provided with the Twin-block appliance during the transitional dentition stage of development has no effect on (1) anteroposterior relationship of the maxilla to the mandible after treatment, (2) overjet, and (3) dental malocclusion as recorded by the peer assessment rating (PAR).

Fourteen hospital-based orthodontic specialists in the United Kingdom (UK) agreed to take part in the study. Each had undergone basic specialty

Results

A total of 174 patients were enrolled into the project. Of these, 89 (41 girls, 48 boys) were allocated to the Twin-block and 85 (39 girls, 46 boys) to the control group. Enrollment started in March 1997 and was completed by August 1999. The last data collection was done in November 2000. The average age of the children was 9.7 (SD = 0.98) years for the treatment group and 9.8 (SD = 0.94) years for the control group.

We found that 14 (16%) of the children who were enrolled in the treatment group

Skeletal versus dental change

One of the most important morphologic findings of this study was that early intervention with a Twin-block appliance successfully reduced dental overjet, molar discrepancies, and severity of malocclusion. This was achieved by a combination of dental and skeletal change. Interestingly, the amounts of overjet and molar change that were attributable to skeletal change were 27% and 41%, respectively, and this was made up of growth modification of both the mandible and the maxilla to a similar

Conclusions

In a multicenter setting in the UK, early orthodontic treatment with the Twin-block appliance resulted in substantial reduction in the overjets of children with Class II malocclusion. This was mainly due to dentoalveolar change, with a small element of favorable skeletal change. The magnitude of the patient’s initial discrepancy was related to the outcome of treatment. This study reinforces the findings of other, similar randomized, controlled trials that suggest that early functional appliance

Acknowledgements

The authors thank the patients who took part in this study and the supporting staff for their additional work at the treatment centers.

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Supported by the Medical Research Council (G9410454).

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