The indirect pulp cap is a valuable tool in a dentist’s tool in a dentist’s bag of tricks. I perform this procedure when I do desire to avoid a root canal procedure on a tooth that may not absolutely require one.
It differs from it’s cousin the ‘direct pulp cap’ in that it does not involve an actual pulpal exposure. Instead, when cleaning out a large cavity the dentist make the choice to be more fussy about cleaning the areas of the tooth away from the nerve, but chooses to not expose the actual nerve by removing all of the ‘affected dentin’.
Affected dentin is tooth structure that has been partially demineralized by the bacteria causing the decay, but not ‘frankly decayed’. It is not chocolaty colored but may have a slightly different color than healthy, unaffected, dentin. Unlike ‘sound’ dentin which is sterile affected dentin may have some bacteria present in it and not be sterile.
During the indirect pulp cap procedure, I selectively dissect out the decay from a tooth. I start by making an ‘outline form for the tooth’s filling. I open up the tooth in the area of the decay to the point where I can not detect any decay in the tooth along the walls of the prep. At that point I carefully excavate the wall of the tooth nearest to the pulp(axial wall in dentist speak).
I do this either with small sharp spoon excavators with very gentle pressure, or a round bur with extremely gentle pressure.
As I clean I continually check the tactile qualities of the affected dentin to judge how clean I have gotten that part of the tooth. I also shine a bonding light on the tooth to judge the color of the affected dentin and to help assess how close the pulp is to the area I am working.
Although this process takes longer than preparing a regular cavity, It allows me to avoid numerous pulpal exposure that would have occurred if I used a more conventional excavation technique. When I have completed my excavation and thoroughly examined the tooth for any possible small pulpal exposure, I place Dycal over the parts of the excavation closest to the pulp and then place a glass ionomer restoration in the tooth. Often I use an glass ionomer material named ‘Miracle mix (Fuji GC) and use it as an intermediate filling material . I find that many ot the teeth that get these indirect pulp caps require crowns and an intermediate filling allows me time to see whether the tooth will remain asymptomatic, prior to preparing it for its crown. Another material that I can use to cover over the Dycal is IRM material.
If composite it to be placed at this session I follow a slightly different protocol. I would either use a whitish glass ionomer base or Vitrabond to cover the dycal. I never place composite directly over dycal, since dycal absorbs moisture and if a composite is place over dycal I am concerned that the moisture sorption by the composite material will dissolve and degrade the dycal. Covering the Dycal with glass inomer or IRM tends to protect it from getting wet by excess moisture.
In direct pulp caps can and do work well even for some previously symptomatic teeth. Most of the times after indirect pulp caps , the teeth’s pulp remain vital and I am able to make a permanent restoration for the tooth and do not need to perform a root canal. I do not have to re-excavate any affected dentin at a later time(as advocated by some dentists). A small percentage of the time, the procedure, the tooth either gets symptomatic or I discover that the nerve has died by checking subsequent check up X-rays. I have been selectively using indirect pulp caps for many years and I find that my success rate for this procedure is better than 85% .