title: Comparison between two methods to evaluate temperature changes produced by composite light curing units and polymerization techniques.
abstract: OBJECTIVE
  This study evaluated the temperature change into the pulp chamber during the light curing of composite resin by direct (bovine tooth) and indirect (matrix) methods.
  
  
  METHODS
  Direct method: fifty standardized cavities (2x2x2 mm) were prepared in bovine incisors, which were randomly assigned to evaluation of the temperature changes in the pulp chamber. Indirect method: temperature changes were evaluated through a dentine slice of 1.0 mm thickness in a elastomer cubic mold (2x2x2 mm). Filtek Z250 composite resin (3M/ESPE) was photo-activated using three light curing units: quartz-tungsten-halogen (QTH) by continuous, soft-start or intermittent light modulations; light emitting diode (LED); and plasma arc-curing (PAC). Ten groups (N.=10) were established according to technique evaluation and photo-activation methods. All experiments were carried out in a controlled environment (37 °C and 50 ± 10% relative humidity). The temperature changes were recorded using a digital thermometer attached to a type-K thermocouple in contact with the dentin slice (indirect method) or in contact with the axial wall (dentin) of pulp chamber (direct method). The results were submitted to ANOVA and Tukey's test (α=0.05).
  
  
  RESULTS
  Temperature changes were statistically higher for the matrix indirect method (2.56 ºC) than bovine teeth direct method (1.17ºC). The change temperature was statistically higher for the PAC (1.77 ºC) when compared to other photo-activation modes in bovine teeth direct method.
  
  
  CONCLUSIONS
  The two methods of temperature evaluation were different, however indirect method detected the higher temperature increase. Higher energy density arising from the light curing units and polymerization techniques promoted higher temperature increase.
authors.affiliation: Department of Restorative Dentistry, University of Campinas, Piracicaba, Brazil.
authors.forename: F H F
authors.initials: FH
authors.lastname: Loureiro
authors.forename: S
authors.initials: S
authors.lastname: Consani
authors.forename: R D
authors.initials: RD
authors.lastname: Guiraldo
authors.forename: R L X
authors.initials: RL
authors.lastname: Consani
authors.forename: S B
authors.initials: SB
authors.lastname: Berger
authors.forename: R V
authors.initials: RV
authors.lastname: Carvalho
authors.forename: L
authors.initials: L
authors.lastname: Correr-Sobrinho
authors.forename: M A C
authors.initials: MA
authors.lastname: Sinhoreti
mesh_terms: D000818:Animals; D002164:Camphor / Q000031:analogs & derivatives / Q000528:radiation effects; D003188:Composite Resins; D055117:Curing Lights, Dental / Q000145:classification; D003804:Dentin; D006813:Humidity; D066298:In Vitro Techniques; D008422:Materials Testing; D010777:Photochemistry; D058567:Photoinitiators, Dental / Q000528:radiation effects; D058105:Polymerization / Q000528:radiation effects; D013696:Temperature; D013821:Thermometers
chemical_list: D003188:Composite Resins; D058567:Photoinitiators, Dental; D002164:Camphor; C553149:camphorquinone