Assessment of matrix metalloproteinase-9 in pulpal blood as a biomarker of inflammation in primary teeth: An in vivo pilot study

Background: The dental pulp, derived from mesenchymal tissue, undergoes complex inflammatory changes during the progression of dental caries. Accurate assessment of pulpal status is essential for successful pulp therapy in primary teeth, which are inherently more susceptible to pulpal involvement due to their anatomical characteristics. Conventional diagnostic methods are often unreliable in pediatric patients, particularly when treatment is performed under general anesthesia. Biomarker-based evaluation of pulpal blood may provide an objective alternative for assessing pulpal inflammation. Aim: This study aimed to investigate matrix metalloproteinase-9 (MMP-9) levels in pulpal blood as a potential biomarker of inflammation in primary teeth. Settings and Design: This prospective, observational pilot study was conducted in the Department of Pediatric Dentistry, D. Y. Patil Dental School, Pune. Methods: Ten mandibular primary second molars from healthy children aged 4–8 years with deep carious lesions approaching the pulp were included. Pulpal blood samples (100 μL) were collected under aseptic conditions during pulpotomy or pulpectomy procedures. Gelatin zymography was performed to assess the gelatinolytic activity of MMP-9, followed by densitometric quantification. Pulpal bleeding control time was recorded to evaluate its association with MMP-9 levels. Statistical Analysis: Data were analyzed using SPSS version 13. Associations were assessed using the Chi-square test, and differences in MMP-9 levels were analyzed using the unpaired t -test, with statistical significance set at P < 0.001. Results: Zymographic analysis revealed gelatinolytic bands corresponding to MMP-9 (71–124 kDa). Intense enzymatic activity was observed in two samples from teeth diagnosed with irreversible pulpitis requiring pulpectomy, while samples from reversible pulpitis showed minimal or undetectable activity. No significant correlation was found between MMP-9 levels and pulpal hemostasis duration. Conclusion: Elevated MMP-9 levels reflect severe pulpal inflammation in primary molars, highlighting its potential as a biochemical biomarker. Further large-scale studies are required to validate its diagnostic and prognostic utility in pediatric endodontics.