Properties of an Experimental Premixed Endodontic Material

Mineral trioxide aggregate, a successfully used endodontic material, requires mixing of powder and liquid components prior to use. This study evaluated a new premixed material consisting of Portland cement (PC), polyvinylbutyral (PVB), and ethanol as a potential endodontic material.  OBJECTIVES: To determine hardening properties and dye penetration resistance of PC-PVB composite.  METHODS:  PVB-ethanol solutions (10mass% and 25mass% PVB) were prepared by dissolving PVB (mw=88k) in absolute ethanol. For each solution, PC-PVB pastes with P/L ratios of 3, 2, and 1 were prepared.  Specimen disks (6mm D x 3mm H) were prepared by placing PC-PVB paste in a mold, which was then covered with fritted glass plates and placed in water. Ingress of water into the paste led to material hardening. The specimen was demolded after 1d, immersed in water for 6d, and placed in a dye (1mass% poly-R dye, pH 7.4) solution for 7d.  The specimen was then fractured and distances of dye penetration into the material were measured at 10 points on each fractured surface under a microscope (25x). Sample hardening properties were evaluated on similarly prepared discs using Gilmore needle method.  RESULTS:  Premixed PC-PVB pastes remained in a soft and cohesive state indefinitely. They transformed to clay-like materials in (10-30) min after exposure to water. Samples with P/L=3 hardened in about 120min while those with P/L=1 remained pliant. Dye penetration ranged from 0.0 mm (n=3), for all samples prepared with P/L =3, to a maximum of (0.20±0.13) mm (n=3) for samples prepared with 10% PVB and P/L=1.  Two-way ANOVA showed that both PVB% and P/L produced significant effects (p<0.05) and there were interactions between main effects. CONCLUSION: Some of the test PC-PVB materials possessed adequate dye penetration resistance and hardening properties required for endodontic materials.  Supported by NIDCR DE11789, ADAF, NIST, US Navy, and JMSDF.