Could these teeth be sensitive from gum recession? Yes it can, sometimes. Not all exposed dentin acts the same way. Some exposed dentin is extremely sensitive, while in other areas of exposed dentin may be relatively insensitive This can be explained by the microscopic structure of dentin.
Dentin when viewed under a microscope is looks similar to bone without any marrow spaces The structure is a calcified material that has tiny tubules (holes). When dentin is laid down it has fluid inside the tubules and each has a tiny odontoplastic process ( the process is usually associated with a nerve fiber) that sits inside the pulp. If the tubule is touched by cold liquid or touch it can cause pain The more tubules that are touched, the more pain! This is why exposed dentin can be extremely sensitive.
Some dentin is insensitive. Why? It can become less sensitive because some or all of the tubules become “sclerotic”. When dentists speak of sclerotic dentin , they mean that the tubules have become calcified and therefor not sensitive. Sclerotic dentin can form for a number of reasons. When dentin is freshly exposed in the mouth it initially is sensitive but over time the tiny tubules get plugged up with debris and can become calcified. Also sometimes when the pulp is irritated by caries, teeth grinding or after a cavity is filled, it reacts by forming secondary dentin. This new dentin tends to be adjacent to older dentin and can cause the older dentin to be cut off from any nerve processes that can create sensitivity. The older dentin now becomes insensitive and becomes nonvital, since it has no fluid filled tubules with living odontoblastic processes in it. The pulp remains vital, but some of the outer layers of dentin are not.
If I have a patient who is complaining of sensitivity coming from a tooth and I see some exposed dentin on the tooth, I test it for sensitivity by running a sharp dental tool over the dentin surface and see how my patient reacts. If the patient displays a startled reaction, there is a good chance that the exposed dentin is playing an active role in their sensitivity. Some of these patients have another problem that can cause the increased sensitivity (a crack in the tooth, or an hyperemic pulp) but others may just need to seal this exposed dentin with a small composite restoration.
Dr. Andrea Stevens is a cosmetic and family dentist in practice in Kanata, Ontario. If you have dental questions, you can call her at 613.271.7091.