THERAPY The Twin-block appliance, used during the

mixed dentition in Class II Division Imalocclusions, may providepsychosocial benefits

ARTICLE

ANALYS IS &

EVALUATION

Original Article O’Brien K, Wright J, Conboy F, Chadwick S, Connolly I, Cook P,et al. Effectiveness of early orthodontic treatment with theTwin-block appliance: a multicenter, randomized, controlled trial.Part 2: Psychosocial effects. Am J Orthod Dentofacial Orthop2003;124:488-94; discussion 494-5.

Level of Evidence 1b

Purpose To determine the psychosocial benefits that result from the useof the Twin-block appliance in Class II Division I malocclusionsduring the mixed dentition

Source of Funding Information not available

ed controlled trial

Type of Study/Design Randomiz

Summary

SUBJECTSThe sample consisted of 176 subjects who were enrolledbetween March 1997 and August 1999 at 14 hospital-based orthodontic specialty practices in the UnitedKingdom. All subjects were between 8 and 10 years oldat the time of enrollment, and they were randomlyassigned to Twin-block therapy (41 females, 48 males)or observation only (41 females, 46 males). All subjectspresented with Class II Division I malocclusions, and aminimum of 7 mm of overjet.

THERAPYThe treatment group received 15 months of therapywith the Twin-block appliance, a removable, functional

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appliance that postures the mandible forward. Subjectswere instructed to wear the appliance 24 hours per day,with removal only for contact sports and swimming.

MAIN OUTCOME MEASUREThe main outcome measures were the Piers-HarrisChildren’s Self-Concept Scale scores (total score and6 cluster scores) and the Perceptions of the Benefitsof Orthodontic Treatment questionnaire scores.

MAIN RESULTSAt the onset of the study, the Piers-Harris scores forthe treatment and control groups were both higherthan reported population norms. After 15 months oftreatment, the treatment group exhibited significantlybetter self-concept scores than the untreated group. The

improvement in the treatment group was roughly 10%of the original scores. The results of the Perception ofthe Benefits of Orthodontic Treatment questionnaireindicated that 4 main factors (general well being,confidence, health of teeth, mouth function) accountedfor 60% of the variance.

CONCLUSIONSThe results of this study suggest that the use of theTwin-block appliance during mixed dentition results inhigher self-concept scores.

Commentary and Analysis

This is a landmark study in orthodontics, due to theimplementation of a multi-site design to evaluate earlyorthodontic treatment. The first publication from thisproject reported on the effectiveness of the Twin-blockappliance in correcting Class II Division I malocclu-sions,1 and this second publication addresses potentialpsychosocial benefits. Due to recent controversy overthe merits of 2-phase treatment, both of these questionsare important to answer.

Detecting the psychosocial benefits of orthodontictreatment has been difficult, as the authors point outin this article. The strengths of this study are the con-sistency of the improvement in self-concept scores,both overall and for each of the 6 clusters of the Piers-Harris test. On the other hand, both the treated anduntreated groups had self-concept scores that werealready above population norms at the onset of thestudy, and the improvement in scores was only about10%. Thus, while this study reports an improvement in

Journal of Evidence-Based Dental PracticeVolume 4, Number 4

self-concept scores, it is uncertain if these gains trans-late into any meaningful or measurable difference inthe lives of these patients.

Several randomized trials have reported that limitedorthodontic treatment in the mixed dentition producessignificant dental and skeletal differences in Class IIDivision I patients compared to untreated Class IIDivision I controls. However, these assessments wereperformed at an intermediate stage, and these differ-ences were not maintained when the treated anduntreated groups were compared after comprehensiveorthodontic treatment.2,3 Along these lines, one mightask whether the improvements in self-concept willremain after comprehensive orthodontic treatment isperformed in both groups of the current randomizedtrial. Hopefully the authors will be able follow-up thesepatients and answer this question.

REFERENCES1. O’Brien K, Wright J, Conboy F, Sanjie Y, Mandall N, Chadwick S,

et al. Effectiveness of early orthodontic treatment with the Twin-block appliance: a multicenter, randomized, controlled trial. Part 1:Dental and skeletal effects. Am J Orthod Dentofacial Orthop2003;124:234-43.

2. King G, McGorray S, Wheeler T, Dolce C, Taylor M. Comparison ofpeer assessment ratings (PAR) from 1-phase and 2-phase treatmentprotocols for Class II malocclusions. Am J Orthod DentofacialOrthop 2003;123:489-96.

3. Tulloch J, Proffit W, Phillips C. Outcomes in a 2-phase randomizedclinical trial of early Class II treatment. Am J Orthod DentofacialOrthop 2004;125:657-66.

Reviewer:Greg Huang, DMD, MSD, MPHUniversity of WashingtonSeattle, Washington

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