Effect of vacuum-formed retainers combined with modified Hawley Ⅱretainers on anterior deep overbite malocclusion

Objective To find an appropriate method to effectively maintain the result of correcting deep overbite malocclusions by using vacuum-formed retainers only or combined it with modified HawleyⅡ retainers. Methods Eighty adolescent patients (age ranging from 13-20 years) and eighty adult patients (age ranging from 21-42 years) with deep overbite malocclusions after orthodontic treatment in department of stomatology, Aerospace Central Hospital from March 2011 to November 2013 were included in this study. The two groups were randomly divided into 2 subgroups: group A, B and group C, D, with 40 patients in each group. Patients in group A and C (vacuum-formed retainers group) wore the vacuum-formed retainers day and night, while the patients in group B and D (combination group) wore the vacuum-formed retainers in the day time and modified Hawley Ⅱ retainers at night. Study models, cephalograms, periapical radiograph and photo of occlusal surface were taken for each patient on the day of debond (T1) and 12 (T2), 24 (T3) months after debond. The differences between two measurements were compared. Results The ocurrence rate of occlusal trauma in vacuum-formed group was significantly higher than combination group during 12 months retention period group A (0.33±0.48) vs group B (0.14±0.35), group C (0.13±0.34) vs group D (0.05±0.23), P＜ 0.05. However, the molar occlusion contact area ratio (MOCAR) in combination group was significantly higher than vacuumformed group during 24 months retention period group A (3.99±1.32) vs group B (9.83±1.57), group C (7.31±1.55) vs group D (10.11±0.77), P＜ 0.05. Conclusion Combination group is better than vacuum-formed retainers group in preventing anterior teeth trauma occlusion and reduction of molar contact area, and it can contribute to molar occlusal adjustment and periodontal health for adolescent patients.