Ballal V, et al. – The present study was undertaken to evaluate whether the dentinal fluid levels of MMP–9 (matrix metalloproteinase–9; neutrophil gelatinase) would increase with the progression of carious lesions. Findings revealed that there was a high correlation between MMP–9 from deep and shallow lesions. The authors suggested that patients with more MMP–9 in the deep carious lesion also tended to have more MMP–9 in the shallow lesion.