During caries excavation, we are excavating infected dentin and leaving affected (and normal) dentin behind. But what’s the difference? Normal dentin has apatite crystals in the intertubular dentin and odontoblastic processes in the tubular lumen.
Fusayama reported that carious dentin consists of two distinct layers – an outer layer and an inner layer. Sturdevant refers to the outer layer as infected dentin and the inner layer as affected dentin. Infected dentin is the outer layer of dentin, meaning it’s closer to the DEJ. It is the softest type of dentin. It is infected with bacteria and other damaging things such as acids and enzymes. We must remove infected dentin because it cannot be repaired through remineralization, and we must also remove the bacterial infection. Affected dentin is the inner layer because it is usually closer to the pulp. It’s harder than infected dentin, but softer than normal dentin. It is softer because of the demineralization – minerals lost from the intertubular dentin have formed precipitates in the tubular lumen. It does not need to be removed because if the tooth remains vital, affected dentin can be remineralized. As a caries lesion advances, the bacteria are not at the front. It’s like a marching band in a parade – there are usually some folks who carry a banner ahead of the band. They’re part of the band, but they don’t make any music. I love marching bands, so I hate to drag them down in a rather weak caries analogy, but… Let's say we don't want live music in our parade, just like we don't want decay in our teeth. (I said it was a weak analogy.) If we take away the musicians, we can keep music from being played as the parade marches down the street. We can leave the folks with the banner in the parade because since they don’t have instruments, they can’t make music. If this marching band were a caries lesion, the musicians would be infected dentin carrying instruments, ahem, bacteria. The folks with the banner would be affected dentin – part of the band (or caries lesion), actually the front of it – but not making any music. If that’s not confusing enough, the lagniappe included in this post is a brief discussion of the difference between affect and effect. Affect means to change. Effect is what happens as a result of that change. So the caries process affects dentin, and the effects are infected and affected dentin. Ah, words.
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Side note - whenever I refer to Sturdevant or Summitt, I'm citing one of these two electronic textbooks:
- Heymann, Harold, et al. Sturdevant's Art and Science of Operative Dentistry. 6th ed., Mosby, 2012. - Hilton, Thomas J. Summitt's Fundamentals of Operative Dentistry: A Contemporary Approach. 4th ed., Quintessence, 2013. |