Investigating salivary matrix metalloproteinase-2 and matrix metalloproteinase-9 activity in fixed orthodontic-induced gingival enlargement.

Background: Gingival enlargement (GE) is a common clinical observation among orthodontic patients, yet its underlying causes remain unclear. This study aims to investigate the potential involvement of salivary matrix metalloproteinase (MMP)-2 and MMP-9 activity in orthodontic-induced GE.

Materials and methods: In this case-control study, we enrolled 50 subjects, including 25 individuals with GE and 25 without. The participants, aged 10-35 years, were in the 4^th or 5^th month of their orthodontic treatment. Comprehensive clinical assessments, encompassing plaque index, gingival index, and GE score were performed, and saliva samples were subjected to gelatin zymography to assess enzyme activity. Statistical analysis, including the Chi-square test for age distribution, independent samples t-test for age comparison between study groups, Mann-Whitney U test for MMP activity comparison, and Wilcoxon signed-rank test for comparison of data from the 4^th to 5^th months of treatment, was performed using SPSS version 23.0, with a significance level set at 0.05.

Results: MMP-2 activity was undetectable in the zymograms. In the 4^th month of treatment, MMP-9 activity was more prominent in the case group, though this disparity did not reach statistical significance in the 5^th month. Furthermore, MMP-9 activity did not exhibit a correlation with the GE score.

Conclusion: The activity of MMP-9 in the saliva of orthodontic patients with GE increases during the 4^th month of treatment, but no correlation exists with the degree of GE.