Changes in the physical properties of the Ultrafil low-temperature (70°C) thermoplasticized gutta-percha system

Three tests were used to obtain a basic understanding of the changes taking place in the physical properties of the Hygenic Ultrafil system. The materials studied were raw gutta-percha, gutta-percha points, and the two Ultrafil materials Blue (firm set) and White (regular set) gutta-percha. In the first test a differential scanning calorimeter was used to determine melting points; two crystalline forms were observed in the dental materials and only one crystalline form in the raw gutta-percha. In the second test a magnetic bearing torsional creep apparatus was used in which the rates of crystallization were observed. The differences seen in the induction times of the crystallization are related to the amount of mastication of the gutta-percha. Mastication in this usage is the manufacturers process of mixing the raw gutta-percha with its other components. The gutta-percha is masticated slightly in the points and considerably more in the Ultrafil material. Ultrafil exhibits longer periods of time required to induce nucleation at any specific temperature due to the increased mastication. Melting points were also decreased with increased mastication. In the third test a dilatometer was used to observe isothermal volumetric shrinkage of the materials during crystallization. When the Ultrafil material was compared with the gutta-percha points, the blue material had approximately the same amount of shrinkage, 2.6%; the white material shrank slightly less, 2.2%. The raw gutta-percha being 100% polymer had the greatest amount of shrinkage, 4.6%.