Endodontic pathogens possess collagenolytic properties that degrade human dentine collagen matrix

To measure collagenolytic protease activity from Enterococcus faecalis and Micrococcus luteus and their ability to degrade human dentinal collagen.

Proteases activity of E. faecalis ATCC 29212, ATCC 47077 and M. luteus towards generic and specific human matrix metalloproteinase (MMP) substrates was measured using a fluorimetric assay. The ability of the bacteria to degrade dentinal collagen was tested by quantifying the amount of hydroxyproline released into the media following incubation of the bacteria or heat-inactivated bacteria (HIN) with demineralized human dentine samples for 24 h and by scanning electron microscopy (SEM). Multifactorial anova and Tukey's post hoc test were used to analyse the data (P < 0.05).

All strains had MMP-like activities, but with different substrate affinity; E. faecalis ATCC 29212, ATCC 47077 and M. luteus had the greatest affinity towards MMP-8 (7.75 ± 0.88 μmol L^-1 /3 × 10⁶ CFU), MMP-9 (33.86 ± 5.16 μmol L^-1 /3 × 10⁶ CFU) and generic MMP (26.08 ± 4.48 μmol L^-1 /3 × 10⁶  CFU), respectively. The amount of hydroxyproline released from demineralized dentine was similar (P > 0.05) for the three strains (range 1.8 ± 0.17 to 2.38 ± 0.39 μg 50 μL^-1 ) and was significantly higher (P < 0.001) compared to their HIN counterparts (0.61 ± 0.22 μg 50 μL^-1 ). SEM revealed increased collagen network degradation after incubation with bacteria versus HIN.

Endodontic pathogens possess collagenolytic protease properties that enable them to degrade dentinal collagen, potentially compromising the restoration-tooth and sealer-tooth interfaces. These collagenolytic protease properties could facilitate the migration of pathogenic bacteria into the root canal system and explain in part their role in root canal infections.