title: Alpha- and beta-forms of gutta-percha in products for root canal filling.
abstract: OBJECTIVE
  This study was undertaken to evaluate which materials were in the alpha-form of gutta-percha as claimed, and which were in the more conventional beta-form, and to explore the effect of heating on the materials.
  
  
  METHODS
  Samples of gutta-percha without chemical additives, and dental gutta-percha formulations which included (i) two products previously studied; (ii) 12 newer products; and (iii) one newer product that had been stored at high temperature, were analysed by simultaneous differential thermal analysis and thermogravimetry.
  
  
  RESULTS
  It was found that only four of the newer materials contained the alpha-form; all the rest comprised beta-gutta-percha. No weight loss was found for any material under the conditions of the present experiments. A typical heating cycle up to 130 degrees C caused changes in material behaviour - that is, on reheating fewer endothermic peaks were present. Storage of gutta-percha samples for 10 years under ambient temperature and storage in a heater at 80 degrees C appeared to have no effect on properties.
  
  
  CONCLUSIONS
  It was concluded that heating dental gutta-percha to 130 degrees C causes physical changes; this was not seen with chemically pure gutta-percha. The presence of additives in the dental samples altered material behaviour.
authors.affiliation: Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota School of Dentistry, Minneapolis 55455, USA. combe001@tc.umn.edu
authors.forename: E C
authors.initials: EC
authors.lastname: Combe
authors.forename: B D
authors.initials: BD
authors.lastname: Cohen
authors.forename: K
authors.initials: K
authors.lastname: Cummings
mesh_terms: D004055:Differential Thermal Analysis; D004356:Drug Storage; D006171:Gutta-Percha / Q000737:chemistry*; D006358:Hot Temperature; D013818:Thermogravimetry
chemical_list: D006171:Gutta-Percha