Heating composite resins: Is it beneficial?

This question was submitted by a general dentist: Is it beneficial to heat composite resin before placing it? Are there any disadvantages or advantages to heating?

Dr. Stephen Ferrier provided a quick initial response to the question in collaboration with Dr. Suham Alexander, Oasis Clinical Editor.

Dr. Stephen Ferrier is Assistant Professor in restorative dentistry at the Schulich School of Medicine and Dentistry at Western University. 

Heating composite resin is one way of increasing the flowability of an unpolymerized resin as the viscosity is reduced. This can be advantageous in improving the adaptation of the material to the cavity preparation and decreasing voids. Another advantage of heating the resin may be increasing the surface hardness of the material.

However, the coefficient of thermal expansion of resin material ranges from 2 to 6 times that of the normal tooth structure. As a result, the heated resin will occupy a larger volume and subsequent cooling of the resin after placement may have an additive effect with polymerization shrinkage. This may result in a sub-optimal marginal seal and post-operative sensitivity.

Additionally, the pre-heating of the resin material may adversely affect the packabilty and stickiness of the composite impacting the clinician negatively.

It should also be noted that the temperature of the composite drops quickly after it is removed from the heating device.

An alternative method of increasing the flow of resin is to supply mechanical energy in the form of sonic/ultrasonic vibration as thermal expansion will not be a factor.

References

1. Lohbauer, U., Zinelis, S., Rahiotis, C., Petschelt, A., & Eliades, G. (2009). The effect of resin composite pre-heating on monomer conversion and polymerization shrinkage. Dental Materials : Official Publication of the Academy of Dental Materials, 25(4), 514-519. doi:http://dx.doi.org/10.1016/j.dental.2008.10.006 
2. Wagner, W. C., Aksu, M. N., Neme, A. L., Linger, J. B., Pink, F. E., & Walker, S. (2008). Effect of pre-heating resin composite on restoration microleakage. Operative Dentistry, 33(1), 72-78. doi:http://dx.doi.org/10.2341/07-41
3. Van Noort, R. (2013) Introduction to Dental Materials. 4th Edition. Mosby.