A Randomized Clinical Trial of two Alternative Designs of Twin-Block Appliance

Abstract

Objective

To test if placing a Southend clasp on the upper and lower incisors during Twin-block appliance treatment will control their angulation and enhance skeletal correction.

Design

Prospective, randomized, controlled clinical trial (ISRTCTN 45965219).

Setting

Orthodontic Department, Royal Preston District General Hospital, Preston, UK.

Participants

Fifty-two consecutive patients aged 9–30 years undergoing treatment for Class II division 1 malocclusion (ANB>5°, OJ>6 mm).

Method

Two alternative designs of Twin-block appliance were allocated randomly. One with a Southend clasp on the upper and lower central incisors and one without. The appliances were identical in all other aspects.

Outcomes

Skeletal and dental changes measured on before and after treatment lateral cephalometric radiographs.

Results

There was a statistically significant change in ANB angle between the Southend group (−3·5°) and the Non-Southend group (−2·6°) (P = 0·004). The change in upper incisor angulation was −6·1° for the Southend group and −12·0° for the Non-Southend group, which was statistically significant (P = 0·005). The change in lower incisor angulation was 3·0° for the Southend group and 6·9° for the Non-Southend group, which was statistically significant (P = 0·005).

Conclusions

The presence of a Southend clasp on the upper and lower incisors during Twin-block treatment limited their tipping which enhanced the skeletal correction.