Treatment effects of the quad-helix/crib appliance in open bite patients: a prospective long-term study

AIM: To prospectively investigate the stability of early treatment of dentoskeletal open bites with the quadhelix/crib (Q-H/C) appliance. SUBJECTS AND METHOD: Twenty-eight subjects (16 females, 12 males) with a dentoskeletal open bite due to thumb-sucking habits treated consecutively with the Q-H/C appliance. Lateral cephalograms were analysed before treatment (T1; mean age 8.2 ± 1.3 years), at the end of active treatment with the Q-H/C appliance (T2; mean age 9.7 ± 1.6 years) and about 5 years after treatment (T3; mean age 14.6 ± 1.9 years). The mean duration of treatment was 1.4 years ± 5 months. The T1-T2, T2-T3, and T1-T3 dentoskeletal changes were analysed with Friedman ANOVA and Tukey’s post-hoc tests (P < 0.05). RESULTS: The statistically significant T1-T2 increase in overbite during Q-H/C therapy (4.0 ± 2.0 mm) overcorrected the amount of anterior open bite at T1 (–2.2 ± 1.9 mm). During post-treatment observation no significant change occurred in the overbite (0.2 ± 1.5 mm). Both the maxillary and mandibular incisors showed significant extrusion both during T1-T2 (2.7 ± 1.6 mm and 1.8 ± 1.1 mm, respectively) and T2-T3 (2.4 ± 2.4 and 3.5 ± 2.5 mm, respectively) intervals. The mandibular plane to FH and palatal plane to mandibular plane angles showed significant closure during the T1-T3 interval (–2.8 ± 2.7 and –4.0 ± 2.9, respectively). CONCLUSION: The Q-H/C appliance was effective in producing a stable correction of the dentoskeletal open bite in 86 per cent of growing subjects with thumb-sucking habits. Long-term correction of an anterior open bite was associated with extrusion of the upper and lower incisors and with favourable changes in vertical skeletal relationships.