Acid-etched Dentin Research Articles

Intradental nerve activity induced by reduced pressure applied to exposed dentine in the cat.

In order to study the excitation of intradental nerves by fluid flow in dentinal tubules the following experiments were performed. The fluid flow was caused by reduced hydrostatic pressure applied to the exposed dentine surface of the canine teeth in the anesthetized cat. In one series of 7 cats the intradental nerve activity was recorded by means of electrodes inserted in dentinal cavities. Provided that the pressure was sufficiently reduced and applied to acid-etched dentine in preparations of sufficient depth, intradental nerve activity of different impulse amplitudes was recorded. The responding pressure sensitive units were found to be sensitized by a brief local application of veratrine and desensitized by potassium chloride. In the second series 26 single functional pulp nerve fibre units were dissected from the inferior alveolar nerve in 7 cats. Nerve impulses were recorded by means of platinum-iridium wire electrodes. The conduction velocities of the 9 fibres responding to reduced pressure varied from 8.3 to 43.0 m/s. Five of these fibres also responded to elevated pressure. None of the 9 fibres conducting impulses with a velocity below 2 m/s responded to a reduction in pressure. thus, the present data strongly suggest that intradental nerve endings with myelinated axons are activated by fluid flow in dentinal tubules. Our results support the hydrodynamic mechanism of dentine sensitivity.

Activation of intradental nerves in the dog to some stimuli applied to the dentine

Both scraping of superficial dentine and air blasts induced bursts of action potentials in 19 out of 22 units immediately. In 5 out of 16 units 4.9 mol/l CaCl 2-solution was also effective. Dry absorbent cotton activated 5 out of 16 units with a 10–20 s latency. All 18 units tested responded to mechanical irritation of the pulp. Acid etching of dentine made the units more sensitive. Resin impregnation abolished the responses. Drilling of dentine with a turbine bur induced responses of the same type as air blasts. Three units responded to heat and 2 also to cold. Hypertonic NaCl-solution was only effective when applied either to the pulp (in 9 out of 12 units) or to the inner dentine (in 5 out of 17 units). It is concluded that intradental nerve fibres sensitive to several different stimuli exist in the dog. Many of the stimuli used induce fluid flow in dentinal tubules in vitro. Nerve activation might have been due to the same mechanism with all stimuli used, possibly to mechanical distortion of the peripheral pulp tissue as a result of the fluid flow. The findings support the hydrodynamic hypothesis of dentine sensitivity.

The retentive ability of acid-etched dentin

1. The retentive quality of dentin to Sevriton, Restodent, and Nuva-Seal was not enhanced by acid etching in this investigation. 2. Acid etching smooths and cleans the dentinal surface. 3. Acid etching clears tubule orifices slightly. 4. Sevriton was the most adhesive material tested. Nuva-Seal was the least retentive of the three materials studied.

Microhardness of acid-etched dentin.

Microhardness of acid-etched dentin.