Heraeus 360 Newsletter
May 2011
Lee Ann Brady DMD
There are a few classic concerns I have when adhesively placing a composite restoration. For the first few days and weeks after the patient is in I hope not to see their name on the schedule because they are having sensitivity. When patients are in the office for their hygiene visits I worry about seeing discolored margins, gaps at the restoration margin, recurrent decay or fracture of the remaining tooth. All of these “failures” are contributed to by the stress caused when composite materials shrink during polymerization. This stress causes cusps to flex and stress at the tooth/composite interface. For as long as I have been doing composites we have been talking about how to manage this clinically. It is these clinical implications that are at the heart of my worries.
We have been striving to overcome shrinkage stress and it’s affects through clinical technique and material development for many years. . On the technique side we vary placement of the material and light curing methodology in an attempt to reduce shrinkage stress.
Which of these to utilize and how well they work is still being unraveled in the literature. One theory is that we alter our clinical technique to manage the ratio between the bonded surface and unbounded surface of the material. Using this information the technique of applying composite in thin layers became popular. Recently we have come to understand that the mass of the material being polymerized also has an impact on micro-leakage
Other approaches include altering the light exposure in an attempt to increase the amount of time for resin flow. Curing techniques like “soft start”, “pulse delay” and “wave” work from these theories. Application of a layer of flowable in the base of the restoration, and newer concepts on pre-heating the composite material are also an attempt to manage shrinkage stress.
While we can continue to work from the technique side, what is clear is that working with composite materials that produce low shrinkage stress, due to their inherent chemical properties is the key to success. The inherent properties of the composite have been proven to be far more effective then any of the technique based solutions.
Class one restorations can be challenging when thinking about managing post op sensitivity and issues related to shrinkage stress. For this patient I chose Venus Diamond composite. Following preparation, the tooth was etched, Gluma Powergel was applied prior to the application of IBond Total Etch Dentin adhesive.
