Osteoblast Attachment and Gene Expression on Endodontic MTA Biomaterials

Objectives: The mineral trioxide aggregates (MTA) that are used in endodontics are very biocompatible, but the mechanisms underlying their cellular response are unknown. The objective of this study was to characterize the cell-surface interactions and gene expression of human osteoblasts grown on alternative formulations of MTA.

Methods: A human alveolar bone chip was obtained from a routine oral surgical procedure and explant cultures were harvested after 3-4 weeks of outgrowth in a-minimum essential medium supplemented with fetal calf serum. These cells were seeded onto Grey and Tooth-colored ProRootŪ MTA disks which had been prepared with either water or local anesthetic solution. Replicate MTA disks were recovered after 1, 7 and 14 days of growth.

Results: Scanning electron microscopy showed that the cells attached and spread out onto the MTA surfaces within 24 hours. There were numerous cellular processes that were interacting with the underlying MTA surface and with adjacent cells. The cells had proliferated to form a matrix that overlaid the MTA surface within 7 days and this layer had increased over 14 days of growth. RT-PCR analysis detected Type I collagen and Runx2 message within 24 hours of cell attachment. Collagen and Runx2 expression were maintained in the 7 day cultures and sustained over 14 days of growth on the MTA surfaces. Similar cell-surface interactions and gene expression were found on the alternative formulations of MTA.

Conclusion: Endodontic MTA biomaterials support human alveolar bone cell attachment and the formation of a collagenous matrix while maintaining an osteoblastic phenotype. The cells responded similarly to Grey and Tooth-colored MTA mixed with water or local anesthetic solution.

This research was supported by the American Association of Endodontists Foundation and the National Institutes of Health (T32DE007034).