Methods: This was a multi-centre randomised trial carried out in 14 UK hospital orthodontic departments. One hundred and seventy four children aged 8-10 years old with Class II division I malocclusion with overjets greater than 7mm were randomly allocated to receive either treatment with a Twin Block appliance (89 patients) or to an untreated control group (85 patients). Data were collected on the subjects at the start of the study (DC1) and 15 months later (DC2). Incisal trauma was recorded from the patient history, radiographs and visual examination of intra-oral photographs. The data were analysed with chi-squared tests.
Results: The mean age of the children at DC1 was 9.6 years, of these, 9.2% of the treatment group and 8.8% of the control group had suffered incisal trauma. This was influenced by the size of the overjet and the Class II skeletal discrepancy. At the end of the study period the mean overjet of the treatment group had reduced by 6.6mm (95% CI=7.2 to 5.9) and had increased by 0.3mm (95% CI= 0.03 to 0.62) for the control group. 10.3% of the treatment and 7.9% of the control group had suffered new incisal trauma. This was not significantly different.
Conclusions: Half of the incisal trauma that the subjects experienced had occurred before the study started. Early Twin Block treatment did not reduce the incidence of incisal trauma.
This study was supported by the Medical Research Council: G9410454