Cytotoxicity of Polymer Modified Portland Cement

Objectives: The major advantages of Portland cement based materials are their low cytotoxicity and superior sealing ability due to the leaching of calcium at the material dentin interface. Portland cement (Type 1) has been modified with PMMA and zirconium oxide to create a root canal filling material with a more favorable setting time than Portland cement based materials currently used in Endodontics. The aim of this study is to evaluate whether Portland cement based materials can maintain low cytotoxicity after being modified with PMMA and zirconium oxide.

Methods: Portland cement (type 1) was modified with specific measures of PMMA and zirconium oxide (for radiopacity). This material was then compared to Amalgam, Super EBA, and pure Portland cement (Type 1) by means of MTT assay. Specimens were prepared in acetyl copolymer molds (2mm deep by 3mm in diameter) and allowed to set for 24 hrs before being added to wells containing 100,000 adult pulp fibroblasts each. Specimens were incubated for 24hrs at 37°C before adding MTT reagents and being read via Victor 3 light spectrophotometer. Afterwards, in order to test an unknown material developing as a halo around Portland cement based samples, each well was washed with silver nitrate and placed under UV light to test for calcium.

Results: Pair wise comparison via ANOVA could not determine significant difference between any two specific groups. Welch's ANOVA determined that there is significant difference (P=.024) somewhere between the groups. Qualitative analysis of silver nitrate wash determined that both pure Portland cement samples and Polymer Modified Portland cement samples were leaching calcium products that adhered to the well surface.

Conclusions: Modifying Portland cement with PMMA and zirconium oxide allows for calcium leaching out of the material and onto adjacent surfaces. Cytotoxicity of material samples were determined, however specific variability between groups could not.