title: Influence of cyclic heating on physical property and biocompatibility of α- and β-form gutta-percha.
abstract: OBJECTIVE
  Thermoplasticized techniques with high temperature and repetitive heating in root canal filling may cause degeneration of gutta-percha, producing cytotoxic byproducts and interfering sealing quality. This study was conducted to investigate the influence of cyclic heating on the physical property and biocompatibility of α- and β-form gutta-perchas.
  
  
  METHODS
  Both α- and β-form gutta-perchas were submitted to two heating processes: continuous heating and cyclic heating. Continuous heating was carried out by heating the samples up to 300°C and 400°C. The samples were then analyzed by differential scanning calorimetry, differential thermal analysis (DTA), and thermogravimetry. For cyclic heating process, samples were heated from 30°C to 200°C for seven cycles and analyzed with DTA and thermogravimetry. For cell adhesion assay, samples were treated (30°C to 200°C, one and seven cycles), submitted to cell culture and examined by scanning electron microscope.
  
  
  RESULTS
  Differential scanning calorimetry and DTA indicated that α-form gutta-percha presented a major endothermic peak at 50-57°C, while β-form gutta-percha showed two major endothermic peaks at 46-50°C and 60-63°C. Total weight loss of β-form gutta-percha was about 2-fold greater than that of α-form gutta-percha after continuous heating up to 300°C, or cyclic heating for seven times. Scanning electron microscopy showed no obvious difference of cell adhesion on α- and β-form samples, even with seven cyclic heating or one heating cycle. However, the attachment of the cells to the culture plate (the control) is better than to the gutta-percha samples.
  
  
  CONCLUSIONS
  The increase of heating cycles for α- and β-form gutta-percha exerts no adverse influence on their biocompatibility. Because the physical property of β-form gutta-percha becomes unstable when it is heated at over 300°C or subjected to cyclic heating, β-form gutta-percha may not be recommended for use in thermoplasticized gutta-percha techniques.
authors.affiliation: School of Dentistry and Graduate Institute of Clinical Dentistry, National Taiwan University and National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Ya-An
authors.initials: YA
authors.lastname: Cheng
authors.affiliation: School of Dentistry and Graduate Institute of Clinical Dentistry, National Taiwan University and National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Shih-Hao
authors.initials: SH
authors.lastname: Huang
authors.affiliation: Dental Department of Chang Gung Memorial Hospital, Linkou Branch, Taoyuan, Taiwan.
authors.forename: Hsiang-Chi
authors.initials: HC
authors.lastname: Hsien
authors.affiliation: School of Dentistry and Graduate Institute of Clinical Dentistry, National Taiwan University and National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Yu-Chih
authors.initials: YC
authors.lastname: Chiang
authors.affiliation: School of Dentistry and Graduate Institute of Clinical Dentistry, National Taiwan University and National Taiwan University Hospital, Taipei, Taiwan. Electronic address: pinlin@ntu.edu.tw.
authors.forename: Chun-Pin
authors.initials: CP
authors.lastname: Lin
mesh_terms: D000818:Animals; D002152:Calorimetry, Differential Scanning; D002448:Cell Adhesion / Q000502:physiology; D002478:Cells, Cultured; D004055:Differential Thermal Analysis; D005347:Fibroblasts / Q000648:ultrastructure*; D006171:Gutta-Percha / Q000737:chemistry*; D006358:Hot Temperature; D008422:Materials Testing / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D051381:Rats; D012389:Root Canal Obturation / Q000379:methods*; D013818:Thermogravimetry
chemical_list: D006171:Gutta-Percha
keywords: biocompatibility testing; differential thermal analysis; gutta-percha