Overall objective of this project is the standardization and improvement in the use of gutta percha based materials for filling root canals. Characterization of the aging process by chemical changes and the determination of the effect of aging on mechanical properties will be continued. Investigation will also be conducted to determine thermal conductivity and melt-flow characteristics utilizing simulated and actual root canals. Determination will be made of optimum cone composition and characteristics as well as appropriate test equipment for inclusion in specifications. Recommendations will be made for improvement of clinical procedures.