Does the timing of treatment affect the clinical and psychological outcomes of Twin-block therapy?

Abstract

Design

This study is a multicenter, two-arm parallel randomized control trial carried out across 3 hospital orthodontic units. A total of 75 patients participated in the study, with 41 randomly allocated in an Immediate Treatment Group (ITG) and 34 randomly allocated into an 18-month delayed Later Treatment Group (LTG). The patients were aware as to which group they were being allocated, as were the clinicians. Both patient groups received the same twin block appliance for use during the study. The appliance was to be worn full time, including eating, but to be removed while participating in contact sports or swimming. Achieving an overjet reduction between 2–4 mm was defined as being the clinical endpoint. After this, the appliance was only worn at night up until the next data collection point, allowing an 18-month window to finish treatment.

Blinded clinicians measured skeletal changes using lateral cephalograms and overjet change via study models. Psychological impact was measured using two questionnaires: Oral Aesthetic Subjective Impact Scale (OASIS) and the Oral Health Quality of Life (OHQL). Data was collected from when the patient first registered in the study (DC1), 18 months after registration (DC2) and 3 years after registration (DC3).

Case selection

In total, 41 boys and 34 girls were included in the study. Ages for the boys ranged from within 1 month of their 12th birthday to 13.5 years old. For the girls, the range was from within 1 month of their 11th birthday to 12.5 years old. Further inclusion criteria included a class II skeletal pattern and having an overjet of 7 mm+. Exclusion criteria included patients of non-white Caucasian origin, girls aged 12.5 years+ and boys aged 13.5 years+. Furthermore, patients with a history of cleft lip or palate, mandibular asymmetry, muscular dystrophy, general health precluding compliance with treatment, a medically diagnosed growth excess or deficiency, not dentally fit or having previously received orthodontic treatment were not included in the study.

Data analysis

SPSS Version 25 software was used to undertake the data analysis. No formal statistical testing was undertaken. To analyze and compare the scores between the two groups, independent t-tests were used. All analysis was carried out at 0.05 level of significance. The reliability of the examining clinicians was assessed using Bland–Altman limits of agreement.

Results

As only the ITG were in treatment over the periods of DC1-DC2 a comparison of the clinical outcomes cannot be made. With regards to the psychological outcome, no statically significant impact was noted for the ITG when compared with the LTG, who had not started treatment (OASIS P = 0.53, OHQL P = 0.92).

When comparing the treatment effects of twin block therapy for the ITG (DC1-DC2) and the LTG (DC2-DC3), study model overjet and cephalometric changes were not statistically significant with the exception of % lower facial height (which was deemed not to be clinically significant) and mandibular unit length. There was no statistical significance with regards to the psychological outcomes post treatment when comparing the groups (OASIS P = 0.30, OHQL P = 0.85)

Conclusions

The findings of this study suggest that adolescents (with a mean age of 12 years 8 months for boys and 11 years 8 months for girls) will not be disadvantaged, either clinically or psychologically, by waiting 18 months for twin block therapy.