Natural Desensitization

There are several naturally occurring processes that can improve hypersensitivity over time, even without treatment intervention. These include sclerosis of dentin, deposition of secondary, and tertiary dentin, creation of a smear layer, and calculus formation on the surface of the dentin.

Sclerosis of dentin is the naturally occurring deposition of minerals within tubules that results in a thicker layer of peritubular dentin that is a highly mineralized dentin that is deposited inside the periphery of the tubules. This process eventually results in the tubule becoming smaller in diameter, making it less permeable and less able to transmit stimuli. Many desensitizing agents are intended to stimulate mineral deposition to reduce the circumference of the dentinal tubules. Secondary dentin develops after the tooth root is formed. It differs from the primary dentin, which is formed prior to tooth eruption. Both types are formed by odontoblasts, but secondary dentin is secreted more slowly than primary dentin. Secondary dentin also is formed on the floor and roof of the pulp chamber which causes the pulp chamber to eventually decrease in size. This, in effect, provides a barrier between the dentinal tubules and the pulp to protect the pulp from additional stimuli. Tertiary dentin, also known as reparative dentin, forms after exposed dentin has been traumatized by a stimulus. These natural processes affect dentin permeability and the neural responses of the pulp.9,37

The smear layer has been described as a combination of organic and inorganic microcrystalline debris of cementum and dentin which forms in response to instrumentation such as scaling and root planing, or can occur by burnishing the tooth with a toothbrush, toothpick or other device.10,38 The smear layer plugs the dentinal tubule orifices with debris that consists of dentinal shavings, tissue debris, odontoblastic processes, and microbial elements.39 Calculus formation also provides a protective coating to shield exposed dentin from stimuli. This is evidenced by the postdebridement sensitivity that clients report after removal of heavy calculus deposits.

Just two weeks after subgingival debridement, natural desensitization has been shown to occur.11 Current hypersensitivity treatment modalities are aimed at stimulating these natural processes.