Micronuclei and cytomorphometric alterations in fixed (metal/ceramic) and removable orthodontic appliances: a...

Orthodontic appliances may induce mechanical and biochemical stress on the oral mucosa, potentially leading to early cytological alterations.

To evaluate and compare the cytomorphometric parameters and micronuclei (MN) frequency in fixed metal, ceramic, and removable orthodontic appliances in adolescents at 1 and 6 weeks after appliance placement.

This prospective exploratory comparative study was conducted on 30 adolescents divided into three groups: metal, ceramic, and removable orthodontic appliance (n = 10 each). Exfoliative cytology using Papanicolaou staining was performed at two experimental sites (S1, S2) and one non-contact intraoral comparison site (S3) at 1 week (T1) and 6 weeks (T2). No true pre-treatment baseline (T0) was available. Intergroup comparisons were made using Kruskal-Wallis, and the Wilcoxon signed-rank test was used for within-group comparisons.

Intergroup comparison showed no significant differences for cytoplasmic (C ) area and nuclear (N) area, and N: C ratio across most comparisons (p > 0.05) (p = 0.096-0.995; η² = 0.0003-0.16). A difference was noted only for MN frequency at the S1T1 (p = 0.04; η²=0.22). The principal findings were derived from intragroup T1-to-T2 comparisons. In the fixed metal appliance group, MN (p ≤ 0.028) and N: C ratio (p = 0.002) increased significantly across all sites(S1, S2, S3), with strong effect sizes. The ceramic appliance group showed limited, site-specific changes, with micronucleus frequency significantly increased at S1 (p = 0.014), while the N: C ratio (p = 0.037) and nuclear area (p = 0.002) showed significant changes at S3. The removable appliance group showed a significant increase in MN frequency, N:C ratio, and cytoplasmic area across selected sites, with strong effect sizes.

Within the limitations of this small exploratory study, early post-placement cytological alterations were observed in the oral mucosa during orthodontic treatment, particularly in MN frequency and N: C ratio. However, these findings should be interpreted cautiously due to lack of true pre-treatment baseline. Also, most intergroup comparisons were non-significant. MN frequency and N: C ratio may indicate promising research indicators of cytological alterations suggestive of cytogenetic stress, especially in the fixed metal and removable appliance groups. Nevertheless, there is need for larger longitudinal studies with true baseline assessment before stronger conclusions can be drawn.