Abstract
The purpose of this article is to evaluate the amount of the relapse of anterior crowding and the efficacy of retention appliances by reviewing the best available scientific evidence. A survey of articles published up to November 2019 about the stability of dental alignment and retention after fixed orthodontic treatment was performed using seven electronic databases. Study Selection: Only randomized clinical trials investigating patients previously treated with multi-bracket appliances with a follow-up period longer than 6 months were included. Data Extraction: Two authors independently performed the study selection, data extraction, and risk of bias assessment. All pooled data analyses were performed using a random-effects model. Statistical heterogeneity was evaluated. In total, eight randomized clinical trials (RCTs) were included, grouping data from 987 patients. The ages of the patients varied across the studies, ranging between 13 and 17 years. The observation period ranged between 6 and 24 months. The data showed no significant intercanine width modifications during the retention period with both fixed and removable retainers. A significant modification of Little’s Index was found for the mandibular removable retainers with a mean difference of 0.72 mm (95% Cl, 0.47 to 0.98) and for the maxillary removable retainers with a mean difference of 0.48 mm (95% Cl, 0.27 to 0.68). No significant changes were found by evaluating Little’s Index modification for the mandibular fixed retainers. The results of this meta-analysis showed that all the considered retainers were effective in maintaining dental alignment after fixed orthodontic treatment. However, fixed retainers showed greater efficacy compared to removable retainers.
Highlights
Stable tooth position after orthodontic treatment is considered a treatment goal
Evidence shows that the majority of orthodontic treatments move teeth from a stable to an unstable position [1]
In order to obtain a quantitative estimation of occlusal changes occurred with different retention protocols, we considered the single-arm data of clinical trials as the data obtained from case-series studies, and we performed a meta-analysis extrapolating and combining these data
Summary
Stable tooth position after orthodontic treatment is considered a treatment goal. Evidence shows that the majority of orthodontic treatments move teeth from a stable to an unstable position [1]. In this way, the use of a retainer is considered the only method able to maintain occlusal results [2]. Post-treatment tooth stability can be affected by several different factors, including bone and soft tissue development [3], primary crowding [4,5,6], dental eruption [7], modification of arch form [8], post-treatment occlusion [9], and the characteristics of pre-treatment malocclusion [10].
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