Update on dentin hypersensitivity: with the focus on hydrodynamic theory and mechanosensitive ion channels

Dentin hypersensitivity is an abrupt intense pain caused by innocuous stimuli to exposed dentinal tubules. Mechanosensitive ion channels have been assessed in dental primary afferent neurons and odontoblasts to explain dentin hypersensitivity. Dentinal fluid dynamics evoked by various stimuli to exposed dentin cause mechanical stress to the structures underlying dentin. This review briefly discusses three hypotheses regarding dentin hypersensitivity and introduces recent findings on mechanosensitive ion channels expressed in the dental sensory system and discusses how the activation of these ion channels is involved in dentin hypersensitivity.

Dentina / Dentin

Si bien la dentina y la pulpa tienen marcadas diferencias en su composición y estructura, ambas están tan íntimamente ligadas por su origen embriológico, que cualquier cosa que afecte a la dentina lo hará sobre la pulpa y viceversa. El ejemplo más claro en ese sentido está dado por el líquido intersticial. Este líquido, semejante al plasma pero con menos proteínas, constituye una continuidad entre ambos tejidos y sus efectos hidrodinámicos son muy importantes, tanto en los estados fisiológicos como en los patológicos

Dentina / Dentin

Si bien la dentina y la pulpa tienen marcadas diferencias en su composición y estructura, ambas están tan íntimamente ligadas por su origen embriológico, que cualquier cosa que afecte a la dentina lo hará sobre la pulpa y viceversa. El ejemplo más claro en ese sentido está dado por el líquido intersticial. Este líquido, semejante al plasma, pero con menos proteínas, constituye una continuidad entre ambos tejidos y sus efectos hidrodinámicos son muy importantes tanto en los estados fisiológicos como en los patológicos.

Dentina / Dentin

Si bien la dentina y la pulpa tienen marcadas diferencias en su composición y estructura, ambas están tan íntimamente ligadas por su origen embriológico, que cualquier cosa que afecte a la dentina lo hará sobre la pulpa y viceversa. El ejemplo más claro en ese sentido está dado por el líquido intersticial. Este líquido, semejante al plasma, pero con menos proteínas, constituye una continuidad entre ambos tejidos y sus efectos hidrodinámicos son muy importantes tanto en los estados fisiológicos como en los patológicos.

[Antimicrobial effect of Citrus aurantifolia extract on Enterococcus faecalis within the dentinal tubules in the presence of smear layer]

Instrumentation of the root canals results in formation of smear layer which covers the dentinal tubules. In infected teeth, it is ideal to achieve a material that has the ability to remove the smear layer besides antimicrobial activity. Therefore, this study was designed to evaluate the antimicrobial effect of Citrus aurantifolia extracts [lime juice and rind extract] on Enterococcus faecalis within dentinal tubules in the presence of smear layer. One-hundred and forty dentin tubes were prepared from bovine incisors. After removal the smear layer, the specimens were infected with Enterococcus faecalis. Then, the smear layer was reformed. Test solutions were used as the irrigants in study groups as follows: group 1: 5.25% NaOCl; group 2: 17% EDTA; group 3: NaOCl+EDTA; group 4: Lime juice; group 5: ethanolic rind extract of C.aurantifolia; group 6: 96% ethanol. Dentin chips were collected from inner and outer layers of dentinal walls and optical density was measured. The data were analyzed using one-way ANOVA and Tamphane tests. In outer layer of dentin, the efficacy of rind extract was less than that of NaOCl+EDTA [P<0.05]. Also Lime juice was less effective than EDTA, NaOCl and NaOCl+EDTA [P<0.05]. In inner layer of dentin, Lime juice was significantly less effective than NaOCl and NaOCl+EDTA [P<0.05]. The efficacy of rind extract was less than that of NaOCl + EDTA [P<0.05]. In the presence of smear layer, the antimicrobial activity of Lime juice was less than that of NaOCl but the efficacy of rind extract was similar to that of NaOCl

Real-time measurement of dentinal fluid flow during desensitizing agent application / 대한치과보존학회지

OBJECTIVES: The aim of this study was to examine changes in the dentinal fluid flow (DFF) during desensitizing agent application and to compare permeability after application among the agents. MATERIALS AND METHODS: A Class 5 cavity was prepared to exposure cervical dentin on an extracted human premolar which was connected to a sub-nanoliter fluid flow measuring device (NFMD) under 20 cm water pressure. DFF was measured from before application of desensitizing agent (Seal&Protect, SP; SuperSeal, SS; BisBlock, BB; Gluma desensitizer, GL; Bi-Fluoride 12, BF) through application procedure to 5 min after application. RESULTS: DFF rate after each desensitizing agent application was significantly reduced when compared to initial DFF rate before application (p < 0.05). SP showed a greater reduction in DFF rate than GL and BF did (p < 0.05). SS and BB showed a greater reduction in DFF rate than BF did (p < 0.05). CONCLUSIONS: Characteristic DFF aspect of each desensitizing agent was shown in NFMD during the application procedure.

Dentin permeability: the basis for understanding pulp reactions and adhesive technology

Permeability involves the passage of fluids, ions, molecules, particulate matter and bacteria into and through a substance or tissue under different and varying conditions. The permeability of the dentin is essential to support the physiology and reaction patterns of the pulp-dentin organ. Nutrients and impulses are transported from the pulp via the odontoblast process and the contents of its tubules maintain the dentin as a vital tissue. However, the main interest of this paper focuses on penetration from the outside towards the pulp rather than from the pulp towards the outside. The present overview centers on the dentinal tubules; how they are formed and how they change as a result of normal and abnormal function, age, and pathological processes and the effect of these processes on the permeability of dentin. Particular attention is focused on the patency of the dentinal tubules.This overview is largely based on the author’s own research, clinical insights and active participation in continuing dental education over the last 50 years. It is not a review of the literature related to the permeability of dentin. Rather it presents interpretation of results related to the permeability of dentin based on experience and opinions acquired over a lifetime in dental research.

A permeabilidade envolve a passagem de fluidos, íons, moléculas, material particulado e bactérias para o interior e através de uma substância ou tecido sob diferentes e variáveis condições. A permeabilidade da dentina é essencial para a fisiologia e para os padrões de reação do órgão dentino-pulpar. Nutrientes e impulsos são transportados a partir da polpa por meio dos processos odontoblásticos e o conteúdo dos seus túbulos mantém a vitalidade da dentina. Entretanto, o principal interesse deste artigo concentra-se na penetração do exterior para a polpa e não da polpa para o exterior. O presente artigo centra-se essencialmente nos túbulos dentinários; como eles são formados e como eles mudam em razão da função normal e anormal, idade e processos patológicos, e o efeito destes processos na permeabilidade da dentina. Especial atenção é dada à patência dos túbulos dentinários. Este artigo apresenta uma visão geral do assunto e baseia-se amplamente nas pesquisas e percepções clinicas do próprio autor e em sua ativa participação na educação odontológica continuada ao longo dos últimos 50 anos. Não se trata de uma revisão da literatura relacionada à permeabilidade dentinária, mas sim da interpretação de resultados relacionados à permeabilidade dentinária com base na experiência e opiniões formadas ao longo de toda uma vida dedicada à pesquisa odontológica.

Influence of intrapulpal pressure simulation on the bond strength of adhesive systems to dentin

The purpose of this study was to evaluate the influence of intrapulpal pressure simulation on the bonding effectiveness of etch & rinse and self-etch adhesives to dentin. Eighty sound human molars were distributed into eight groups, according to the permeability level of each sample, measured by an apparatus to assess hydraulic conductance (Lp). Thus, a similar mean permeability was achieved in each group. Three etch & rinse adhesives (Prime & Bond NT - PB, Single Bond -SB, and Excite - EX) and one self-etch system (Clearfil SE Bond - SE) were employed, varying the presence or absence of an intrapulpal pressure (IPP) simulation of 15 cmH2O. After adhesive and restorative procedures were carried out, the samples were stored in distilled water for 24 hours at 37°C, and taken for tensile bond strength (TBS) testing. Fracture analysis was performed using a light microscope at 40 X magnification. The data, obtained in MPa, were then submitted to the Kruskal-Wallis test ( a = 0.05). The results revealed that the TBS of SB and EX was significantly reduced under IPP simulation, differing from the TBS of PB and SE. Moreover, SE obtained the highest bond strength values in the presence of IPP. It could be concluded that IPP simulation can influence the bond strength of certain adhesive systems to dentin and should be considered when in vitro studies are conducted.

Development of nano-fluid movement measuring device and its application to hydrodynamic analysis of dentinal fluid / 대한치과보존학회지

This study was aimed to develop an instrument for real-time measurement of fluid conductance and to investigate the hydrodynamics of dentinal fluid. The instrument consisted of three parts; (1) a glass capillary and a photo sensor for detection of fluid movement, (2) a servo-motor, a lead screw and a ball nut for tracking of fluid movement, (3) a rotary encoder and software for data processing. To observe the blocking effect of dentinal fluid movement, oxalate gel and self-etch adhesive agent were used. BisBlock (Bisco) and Clearfil SE Bond (Kuraray) were applied to the occlusal dentin surface of extracted human teeth. Using this new device, the fluid movement was measured and compared between before and after each agent was applied. The instrument was able to measure dentinal fluid movement with a high resolution (0.196 nL) and the flow occurred with a rate of 0.84 to 15.2 nL/s before treatment. After BisBlock or Clearfil SE Bond was used, the fluid movement was decreased by 39.8 to 89.6%.