An evaluation of occlusal changes during orthodontic retention

The problem of orthodontic relapse is of fundamental importance for clinicians. In the literature there are few studies concerning the change in position of the teeth after orthodontic treatment. This study analyzes the occlusal changes during the first six months of orthodontic retention and the effectiveness of the Hawley retainer at the upper arch and the canine-to-canine multi-stranded fixed retainer at the lower arch in maintaining the anterior tooth alignment. 48 patients were recruited. PAR index, ABO DI, ABO CRE, Irregularity Index, intercanine, interpremolar and intermolar widths were measured for each patient before (T0) and at the end (T1) of the fixed orthodontic treatment and after 1 (T2), 3 (T3) and 6 (T4) months of retention. Statistics used were paired samples t-test and Wilcoxon matched-pairs signed-ranks test. The p-value was considered statistically significant for P<0.05. During 6 months in retention there was a worsening of PAR index (mean: 1.13±1.08; P<0.001), dental alignment (median: 2.5; P=0.0001) and occlusal relationships (median: 2; P=0.0101); a statistically significant improvement of posterior occlusal contacts (median: 2.54; P=0.0004), marginal ridges (median: 0.5; P=0.0250) and interproximal contacts (median: 0.46; P=0.0305). The stability of the orthodontic results has proved to be similar for the two dental arches, as well as the effectiveness of the two retainers in maintaining the alignment of the anterior teeth. During 6 months in retention the occlusal changes were minimal and didn’t affect the stability of the orthodontic treatment in a clinically significant manner. The effectiveness of the upper Hawley retainer and the lower multi-stranded fixed retainer in maintaining the alignment of the anterior teeth was similar.