Flow diagram showing distribution of subjects.
tooth
Written informed consents were obtained from all the subjects. After completion of treatment and debonding of brackets, deep scaling and curettage was performed. Then, two types of fixed mandibular lingual retainers from canine-canine were installed. All retainers were bonded by a single operator, to minimize bias and to standardize the method. Blinding was not possible in this study due to the visible nature of the intervention and assessment. Group 1 subjects received fiber-reinforced composite retainers (INOD, U.P. Fiber Splint, 2mm, Seoul, Korea) while Group 2 (control group) received multistranded stainless steel wire retainers (0.0175-in, All Star Orthodontics, Camas, WA, USA).In Group 1 subjects, the mandibular anterior dental region was well isolated. Intercanine distance was measured using dental floss, and the correct length of fiber ribbon was cut with a scalpel blade. The ribbon was pretreated with adhesive primer (Transbond™ XT adhesive primer; 3M Unitek). Lingual surfaces of the six anterior teeth were etched with 37% phosphoric acid gel (Meta Biomed) for 30 seconds, washed sufficiently and air-dried. Then, adhesive primer was applied with applicator brush and light-cured with a light emitting diode (Otholux; 3M) for 15 seconds on each tooth. Subsequently, application of low viscosity composite resin (Transbond™ LV; 3M Unitek, Monrovia, California, USA) was performed. Eventually, fiber ribbon was conformed to the lingual surfaces of the six anterior teeth with plastic instrument, the excess composite was removed, and each tooth was light-cured for 15 seconds. Further composite resin was applied with applicator for finishing. Finally, each tooth was light-cured for 10 seconds. Oral hygiene instructions were delivered (
