Way back in 1965 Kakaehashi et al(1) showed us that in the absence of microorganisms, even exposed dental pulps can survive quite well. For those of you who aren’t familiar with the research, gnotobiotic (or germ-free) rats had pulps exposed and the access cavities were left completely open. These rats lived in a sterile environment and ate sterile food. After the rats were sacrificed, histology showed that even though the pulp exposures were open and had food and debris packed into them, the pulps in these teeth remained vital and showed healing in the form of dentine bridging. Conversely, the rats who lived in normal environments showed bacterial contamination of their pulps leading to necrosis and paeriapical inflammation.
I recently treated a case where a single piece gold inlay and post needed to be removed as there was carious breakdown of the margins. The tooth was asymptomatic and had been so since the post and restoration was placed over forty years prior. There was no root filling to be seen .On removal of the post and restoration, I was a little surprised by what I found. Have a look at the video below…..
The apical portion of the pulp remained vital after 40 years. This shows the importance that microorganisms play in pathology of the pulp. Other factors, especially heat from preparations (especially when not using water spray) and mechanical trauma can damage a pulp, but microorganisms play the MOST important role.
So, my recommendations when placing restorations are to use chlorhexidine or sodium hypochloride to clean cavities prior to restoration, use a good aseptic technique to exclude saliva (i.e. rubber dam) and use materials and techniques that seal well and prevent bacteria gaining access to deeper parts of restorations and thus the pulp. Oh, and don’t try putting a post into tooth without root filling it first. You’re not going to get as lucky as the dentist who did this one.
1. The Effects of Surgical Exposures of Dental Pulps in Germ-Free and Conventional Laboratory Rats. KAKEHASHI S, STANLEY HR, FITZGERALD RJ. Oral Surg Oral Med Oral Pathol. 1965 Sep;20:340-9.