Temperature excursions at the pulp-dentin junction during the curing of light-activated dental restorations.
OBJECTIVE
Excessive heat produced during the curing of light-activated dental restorations may injure the dental pulp. The maximum temperature excursion at the pulp-dentin junction provides a means to assess the risk of thermal injury. In this investigation we develop and evaluate a model to simulate temperature increases during light-curing of dental restorations and use it to investigate the influence of several factors on the maximum temperature excursion along the pulp-dentin junction.


METHODS
Finite element method modeling, using COMSOL 3.3a, was employed to simulate temperature distributions in a 2D, axisymmetric model tooth. The necessary parameters were determined from a combination of literature reports and our measurements of enthalpy of polymerization, heat capacity, density, thermal conductivity and reflectance for several dental composites. Results of the model were validated using in vitro experiments.


RESULTS
Comparisons with in vitro experiments indicate that the model provides a good approximation of the actual temperature increases. The intensity of the curing light, the curing time and the enthalpy of polymerization of the resin composite were the most important factors. The composite is a good insulator and the greatest risk occurs when using the light to cure the thin layer of bonding resin or in deep restorations that do not have a liner to act as a thermal barrier.


CONCLUSIONS
The results show the importance of considering temperature increases when developing curing protocols. Furthermore, we suggest methods to minimize the temperature increase and hence the risk of thermal injury. The physical properties measured for several commercial composites may be useful in other studies.
Jakubinek
Michael B
MB
Department of Physics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 3J5.
O'Neill
Catherine
C
Felix
Chris
C
Price
Richard B
RB
White
Mary Anne
MA
D003188:Composite Resins / Q000009:adverse effects; D003198:Computer Simulation; D003782:Dental Pulp / Q000293:injuries*; D003799:Dental Stress Analysis / Q000379:methods; D003804:Dentin / Q000293:injuries*; D020342:Finite Element Analysis; D006358:Hot Temperature / Q000009:adverse effects; D008027:Light / Q000009:adverse effects; D055115:Light-Curing of Dental Adhesives / Q000009:adverse effects*; D013814:Thermal Conductivity
D003188:Composite Resins