Degradative activities from human neutrophils toward dental composites and tooth dentin

Gitalis, Russel 1, 2; Glogauer, Michael 2; Finer, Yoav 1, 2

1. Institute of Biomaterials and Biomedical Engineering, University of Toronto; 
2. Faculty of Dentistry, University of Toronto

Background: Human neutrophils in the oral cavity contain several factors that are hypothesized to have cholesterol esterase-like (CE) and matrix metalloproteinase-like (MMP) activities that contribute to the degradation of composite and dentin, and compromise the restoration-tooth interface.
Objective: To measure the CE and MMP activities from human neutrophils and their effect on the degradation of composite and dentinal collagen.
Methods: CE and MMP activities were measured with nitrophenyl-esters or fluorimetric MMP substrates. Degradation of composite (Z250, 3M) and dentinal collagen was quantified by measuring release of a universal composite degradation byproduct, bishydroxy-propoxy-phenyl-propane (BisHPPP) or a marker of collagen degradation, hydroxy-proline, using ultra performance liquid chromatography, UV spectroscopy and mass spectrometry. 
Results: Neutrophils possessed CE activity (1.28±0.29 units/106 neutrophils), and degraded composite after 48 (0.20±0.04) and 96 hours (0.007±0.001 μg BisHPPP released/cm2*107 neutrophils) of incubation. Neutrophils had higher gelatinase MMP-9 activity (0.099±0.018) then collagenase MMP-8 activity (0.004±0.001 μmol/minute*107 neutrophils), which were stable for up to 24 hours. Neutrophils degraded dentinal collagen (15.32±1.23 μg hydroxy-proline released/107 neutrophils) after 24 hours of incubation.
Conclusion: This research provides evidence that neutrophils can degrade resin composite and dentin, the two main components of the restoration-tooth interface.
Significance/Impact: The ability of neutrophils to degrade both dental composite and tooth dentin could accelerate the degradation of the restoration-tooth interface, and compromise the longevity of the restoration. Development of restorative materials that resist CE and counteract MMP activities could decrease the above degradation and increase longevity of the restoration.