Anchorage Reinforcement in Bimaxillary Proclination Cases - a 3-arm Randomised Controlled Trial

Bimaxillary proclination is common in Malaysia especially among Malay, Chinese and possibly the Malaysian Aborigines. Treatment commonly constitutes extraction of upper and lower first permanent premolars with maximum anchorage requirement. Various anchorage device exists, but conventional devices such as Nance button, transpalatal arch and molar blocks are still commonly used to good effect in treatment of bimaxillary proclination. A comparison of these commonly used conventional anchorage devices (molar block, transpalatal arch, Nance button), especially in treating bimaxillary proclination cases, surprisingly has not been done.

Soft tissue changes also occur in bimaxillary proclination. However, changes in the soft tissue profile using these conventional anchorage devices do not exist, as evidence shows that anchorage devices can affect soft tissue outcomes

Hence, the investigators aim to investigate compare the effectiveness and soft tissue changes of using just molar blocks, molar blocks with transpalatal arch and molar blocks with Nance button.

This study will be done as a 3-arm parallel randomised controlled trial. The allocation ration is set at 1:1:1. This study will adhere to the PICO and CONSORT guidelines, and will be registered with the clinical.org website.

Sample size calculation was conducted using G Power 3.9.1.4. The standard deviation of the movement of maxillary permanent first molar was estimated at 2.2 mm. The mean difference of 1.00 mm was considered the smallest important difference to be detected, which was also used as the effect size. In order to detect the difference of 1.00 mm with a power of 0.80 (80%) and an alpha of 0.05, accounting for a 20% dropout, the total sample size required is 15, which will be randomised into 3 groups (5 Nance group, 5 TPA group and 5 molar block group).