Bimaxillary dental proclination is the condition where the upper and lower dental arches are procline thus increase lip fullness. Since the aim of orthodontic treatment in bimaxillary proclination in to get flatten profile where the incisor inclinations are purposely reduced or interincisal angle are increased, therefore it is guarded for corrected dentition to maintain stable or not post orthodontic treatment.Therefore, this study is looking into evidence which is the best retainer to maintain stability of bimaxillary proclination cases following fixed appliances treatment.

Study title Stability of Bimaxillary Proclination Cases Following Fixed Appliances Treatment: A Randomized Control Trial

Study Population Pre-treatment of bimaxillary proclination patient who completed active orthodontic treatment with fixed appliances and are scheduled to debond at Orthodontic Clinic, Faculty of Dentistry, University of Malaya.

Study Design Randomized, prospective, single-center control trial. Three parallel arm groups of patients will be assigned for 3 types of retention methods; 1.VFR 2.Fixed bonded retainer 3.Double regime (bonded & VFR)

Aim of study To determine the best mode of retention to maintain the stability of bimaxillary proclination cases treated by four premolars extraction and fixed appliances.

Specific Objectives

1. To measure the post treatment dental and soft tissue stability in the retention phase up to one-year post treatment
2. To compare the effectiveness the different types of retainers to maintain the stability of orthodontically corrected bimaxillary proclination
3. To determine the impact of the different types of retainers on the OHRQoL

Sample Size The sample size calculation was done using G*power software version 3.1.The f-test, repeated measures ANOVA, within-between interaction were used.

Based on the effect size of 0.43 (Keating PJ 1986), maximum accuracy (power) of 80% (0.80), error of 5% (0.05), number of groups are 3, number of measurements are 2, correlation among repetitive measures is 0.5, nonsphericity correlation is 1, total number of 18 subjects needed for entire study. Allowing for 50% dropout, a final sample size of 27 subjects with 9 subjects per group will be used.

Study Duration September 2019 - Disember 2021

Inclusion Criteria:

1. Pretreatment bimaxillary proclination patients with interincisal angle less than 125º (Keating PJ 1986).
2. Patients with fixed orthodontic appliances treatment on both arches consisting of the extraction of 4 premolars (Keating 1986).
3. Both arches are indicated for retainers.
4. Pre-treatment lateral cephalometric radiograph of adequate diagnostic quality.

Exclusion Criteria:

1. Pretreatment spacing eg: Median diastema.
2. No change or proclined lower labial segment post treatment.
3. Early debond patient.
4. Patient intended to relocate within study period.
5. Hypodontia that require prosthesis, cleft lip and/or cleft palate, or orthognathic cases.
6. Patients with learning disabilities and unable to listen, speak and read written instructions in Bahasa Melayu or English.

The patient will be decided for the type of retention treatment by picking an opaque and sealed envelope.

The participants study models will be examined and assigned with a blinding code by first researcher , who will be blinded to the subjects' retainer allocation. Patients name on the printed radiograph will also be removed. Therefore,the first researcher will be blinded to those she will be measuring. The blinding code will be prepared by second researcher before first researcher measure the casts and radiographs.