The effect of a monomeric dental resin on odontoblastic functions in vitro
Somjin Ratanasathien, D. of Conservative Dentistry, F. of Dentistry, PSU.
Carl T. Hanks, D. of Oral Medicine, Oral Pathology and Oncology, School of Dentistry, U. of Michigan,
Ann Arbor, USA.
Corresponding e-mail : ratanasathien@yahoo.com
Grant : NIDCR grant. DE09296
Presented : 78th General Session of the IADR, April 5-8, 2000, Washington, D.C., USA
Key words : biocompatibility, dental materials, dentin bonding agents, dental resins,
cell culture
Occasional papers on clinical studies have reported unfavorable pulpal reactions of teeth restored with dental resins, varying from inflammation and reparative dentin formation to death of odontoblasts. In vitro studies have shown cytotoxicity of monomeric resins in several cell lines
and diffusion of resins from incomplete polymerization via dentinal tubules. The objective of this research was to determine biocompatibility of UDMA, a common component in several dentin bond-ing agents and resin composites, in a mouse odontoblast like cell line (MDPC.23) as follows: (i) investigation of the effect of UDMA on odontoblasts, by measuring the succinic dehydrogenase activity, (ii) determination of the mode of odontoblastic death, necrosis or apoptosis, using flow cytometry and TUNEL assay, (iii) determination of alteration of cell cycle progression of odontoblasts by UDMA, using flow cytometry, and (iv) investigation of the effect of nontoxic concentrations of UDMA on dentin sialoprotein (DSP) expression of odontoblasts, using Western blot analysis.
The results showed that UDMA had cytotoxicity in the range of 1-100 mM, with the TC50 of 56 +/
- 17 mM, after 24-h exposure. Data from flow cytometry and TUNEL assay indicated that UDMA caused odontoblastic death primarily by necrosis. UDMA inhibited the cell proliferation of a concentration-dependent manner, but no marked change of cell cycle progression in response to UDMA was observed. Therefore, the effect of UDMA on disturbance of the cell cycle of odonto-
blasts was nonspecific by methods used. Nontoxic concentrations of UDMA caused an increased
level of DSP expression. In conclusion, this research suggests that dentin bonding agents should
not be used in direct pulp capping because of its cytotoxicity. With some remaining dentin present, dental resins may play a role in reparative dentin formation underneath resin-restored cavities.
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