title: Modified cytotoxicity evaluation of elastomeric impression materials while polymerizing with reduced exposure time.
abstract: OBJECTIVE
  Cytotoxicity evaluation is an important step in biocompatibility assessment of dental impression materials. Previously, cytotoxicity evaluations were carried out on already set ('set') impression materials for contact time or extraction time of 24 h or longer in duration. However, clinically, dental impression materials are in contact with oral tissue while they are being set ('polymerizing'), for no longer than 10 min. Hence, the aim of this study was to investigate the difference in results between 'polymerizing' and 'set' forms of impression materials as well as the difference in results between longer duration of contact or extraction time (12 or 24 h) and shorter duration of time (15 or 30 min).
  
  
  METHODS
  Seven dental impression materials of different chemical compositions were tested. Two commonly used in vitro tests were used-test on extraction and test by direct contact. Both 'polymerizing' and 'set' forms of impression materials were used with different durations of extraction and contact (15 min, 30 min, 12 h and 24 h).
  
  
  RESULTS
  There were significant (p < 0.05) differences of cell viability and cell proliferation between the 'polymerizing' and 'set' impression materials. Also, significant (p < 0.05) differences were noted with variance in duration of time.
  
  
  CONCLUSIONS
  In light of the results, it is recommended to use a 'polymerizing' state of dental impression material for cytotoxicity evaluation, with 15 or 30 min of contact between cell and dental impression materials and an extraction time of 15 or 30 min that is more reflective of clinical situations.
authors.affiliation: Research Center for Orofacial Hard Tissue Regeneration, Yonsei University College of Dentistry, Seoul, Republic of Korea.
authors.forename: Jae-Sung
authors.initials: JS
authors.lastname: Kwon
authors.forename: Sang-Bae
authors.initials: SB
authors.lastname: Lee
authors.forename: Chong-Kwan
authors.initials: CK
authors.lastname: Kim
authors.forename: Kyoung-Nam
authors.initials: KN
authors.lastname: Kim
mesh_terms: D001672:Biocompatible Materials; D003764:Dental Materials
chemical_list: D001672:Biocompatible Materials; D003764:Dental Materials