title: Finite element analysis of heat generation from different light-polymerization sources during cementation of all-ceramic crowns.
abstract: BACKGROUND
  Exothermic composite resin chemical reactions and visible light generators can produce heat during a restorative polymerization process. These thermal changes in restored teeth may cause pain and irreversible pulpitis.
  
  
  OBJECTIVE
  The purpose of this study was to analyze the temperature distribution and heat flow patterns of a crowned mandibular second premolar tooth model using 3 different light-polymerization technologies and a finite element technique.
  
  
  METHODS
  A 2-dimensional finite element model was used to simulate a clinical condition. Heat flow and thermal stress distribution in a tooth during cementation of an all-ceramic crown using 4 commercially available light-polymerization units (LPUs), each with different wavelengths (Elipar TriLight, Elipar Freelight, Apollo 95 E, and ADT 1000 PAC), were investigated. The temperature values were measured at 3, 10, 12, and 40 seconds for each light-polymerizing unit (LPU) at 6 different finite element nodes. Two-dimensional temporal and spatial distribution of the thermal stress within the tooth, including the thermal coefficients and boundary conditions of the dental materials, were obtained and evaluated.
  
  
  RESULTS
  The temperature at the nodal points did not exceed 42 degrees C, which is a threshold value for tissue vitality within the recommended operating periods at the dentin and pulp surface for all LPUs, except for Elipar TriLight. In the case of Elipar TriLlight, the temperatures at the dentin and pulp surfaces were 47 degrees C and 42 degrees C, respectively.
  
  
  CONCLUSIONS
  When the light-polymerization units were used according to the manufacturers' operating procedures and without prolonged operating periods, with the exception of Elipar TriLight, the investigated LPUs did not produce significant heat. However, when the operating periods were prolonged, unacceptable temperature increases were observed, especially with the high-intensity LPUs.
authors.affiliation: Department of Prosthodontics, Istanbul University, Faculty of Dentistry, Istanbul, Turkey. eliftunc@superonline.com <eliftunc@superonline.com>
authors.forename: Elif Pak
authors.initials: EP
authors.lastname: Tunc
mesh_terms: D002484:Cementation / Q000379:methods; D003442:Crowns; D003762:Dental Instruments; D003793:Dental Restoration, Permanent / Q000295:instrumentation* / Q000379:methods; D004055:Differential Thermal Analysis / Q000379:methods; D020342:Finite Element Analysis; D006358:Hot Temperature; D008027:Light; D003765:Models, Dental