Metal versus Fiberglass Post-Orthodontic Retainers Short-Term Effects on Plaque Index and Microbial Colonization: An Observational Study

In orthodontics, post-treatment retention phase is crucial for maintaining the obtained clinical results. In cases of crowding, a bonded fixed retainer is often chosen to maintain teeth alignment in the anterior sector of the lower dental arch. A fixed retainer can remain in the mouth for years. Therefore, it is important that it is applied with harmless materials for the level of plaque control. The present study aimed to investigate the salivary concentrations of Streptococcus mutans (S. mutans) and Lactobacilli, and the Sillness and Loe plaque index, in patients wearing metal wire versus fiberglass orthodontic retainers. Forty post-orthodontic patients were included in the sample: in 20 subjects a metal wire retainer was applied (MR), while in the others a fiberglass retainer was applied (FR). The variables were recorded at baseline (T0), after 1 month (T1), and after 2 months (T2) of follow-up. The percentage of patients with a level of S. mutans and Lactobacilli colonization > 10(5) increased over time in the FR group (T0 = 0%, T1 = 5%, T2 = 35%), compared with the MR group. PI increased in the FR group (T0 = 0, T1 = 14, T2 = 27), and remained almost the same in the MR group (T0 = 3, T1 = 0, T2 = 2). From the present results it appears that the metal wire retainer is better than the fiberglass retainer for the level of plaque control performed by the patients.