Effectiveness of Two Types of Fixed Lingual Retainers in Preventing Mandibular Incisor Relapse.

Objective: To compare and evaluate the relapse tendency of two types of fixed lingual retainers using Little's irregularity index for a follow-up of one year.
Study Design: Randomised clinical trial.
Place and Duration of Study: Department of Orthodontics, Dr. Ishrat Ul Ebad Khan Institute of Oral Health Sciences and Dow Dental College in Dow University of Health Sciences, Karachi, Pakistan, from November 2017 to March 2019.
Methodology: A total of 54 patients were recruited and divided into two groups by random allocation. Subjects who have completed fixed appliance (MBT) orthodontic treatment and non extraction cases with moderate crowding in the lower arch were included. Subjects with caries, restoration, fracture or missing lower anterior teeth were excluded. Group 1 received fiber reinforced composite (FRC) retainers and group 2 received multistranded stainless steel (MSW) retainers. They were recalled after every three months interval for one year. Relapse tendency of retainers using Little's irregularity index was evaluated at each visit.
Results: Comparison of relapse tendency between two retainers showed statistically significant results (p<0.05). The mean difference of CPD between two retainers at T0 was found to be 0.09 mm (p=0.01). At T1, it was determined to be 0.3 mm (p=0.022), and at T2 it was found to be 0.3 mm (p=0.008). At T3 and T4, it was found to be 0.5 mm (p<0.001) and 0.5 mm (p=0.002), respectively. All mean differences were statistically significant.
Conclusion: Fiber-reinforced retainers are more effective in preventing the mandibular incisor relapse. The results of the study also suggest that the irregularity of the dentition increases with the passage of time.