title: Effects of processing parameters on physical properties of the silicone maxillofacial prosthetic materials.
abstract: OBJECTIVE
  Maxillofacial prostheses are commonly fabricated using dental stone molds. However, for evaluating physical properties, maxillofacial materials are most often cured in metal molds. A-2186 is a silicone-based maxillofacial prosthetic material. Because its cure may be inhibited by traces of impurities, its physical properties may be different when it contains additives and is cured in dental stone molds, compared to when it is cured in metal molds without additives. This study's purpose is to determine and compare the physical properties of A-2186 cured in stainless steel molds and stone molds. The effects of additives and cure conditions on the physical properties were also studied.
  
  
  METHODS
  Hardness, tensile strength, ultimate elongation, and tear strength of A-2186 cured in dental stone molds, stainless steel molds, and with and without additives were determined. The bonding strength of A-2186 to four adhesives was determined by the peel test. All comparisons were made using analysis of variance (ANOVA).
  
  
  RESULTS
  Hardness, tensile strength and ultimate elongation of A-2186 cured in stainless steel molds are significantly higher than those cured in stone molds. Adding a small amount of a pigment, a kaolin and a fiber reduces hardness, tensile strength, ultimate elongation and tear strength. Except for Hydrobond, the bond strength of the adhesives to A-2186 was not significantly affected by the cure conditions and additives.
  
  
  CONCLUSIONS
  Physical properties of A-2186 are affected by the additives commonly used in fabricating maxillofacial prostheses, and use of stone molds for curing degrades A-2186's mechanical properties. In fabricating clinical prostheses, special attention should be exercised to avoid contamination of A-2186 with impurities that could inhibit curing and produce inferior prostheses.
authors.affiliation: LAI Laboratories, Inc., Burnsville, MN, USA. jlai@aol.com
authors.forename: J H
authors.initials: JH
authors.lastname: Lai
authors.forename: J S
authors.initials: JS
authors.lastname: Hodges
mesh_terms: D000268:Adhesiveness; D000704:Analysis of Variance; D002133:Calcium Sulfate; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004548:Elasticity; D006244:Hardness; D008422:Materials Testing; D008447:Maxillofacial Prosthesis; D003765:Models, Dental; D011474:Prosthesis Design; D012826:Silicone Elastomers / Q000737:chemistry*; D013193:Stainless Steel; D013674:Technology, Dental / Q000295:instrumentation*; D013718:Tensile Strength
chemical_list: D012826:Silicone Elastomers; D013193:Stainless Steel; D002133:Calcium Sulfate