Dentin permeability, dentin sensitivity, and treatment through tubule occlusion.
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Dentin↗
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Dentin permeability and dentin sensitivity.
The hydrodynamic theory of dentin sensitivity is based on the premise that sensitive dentin is permeable throughout the length of the tubules. Such a condition may permit the diffusion of bacterial products across dentin to the pulp where they may cause irritation of pulpal soft tissues. However, the slow outward movement of dentinal fluid tends to flush the tubules free of exogenous substances. This balance between the inward diffusion of exogenous substances, whether bacterial or the active ingredients in desensitizing medicaments, and the cleansing action of dentinal fluid flow needs to be examined experimentally.
Dentin↗
Dentin permeability: sealing the dentin in crown preparations.
Provisional restorations of full crown preparations may permit more microleakage of bacteria and their products than the final castings do. However, most investigations of the sealing qualities of cemented castings have reported that they too permit dye leakage. One approach to the problem is to seal the dentin with dentin bonding agents at the completion of the crown preparation. This study evaluated the ability of six different dentin bonding agents to seal the dentin of crown preparations of human teeth in vitro using two independent techniques. The first technique quantitated fluid filtration across dentin before and after treatment with dentin bonding agents at one hour, one day, one week, and one month and after thermocycling. The second method measured silver nitrate penetration of the thin veneers of dentin bonding agents into the dentin. Both methods correlated well with each other. The best seals were obtained with Prisma Universal Bond 2 or Superbond powder plus liquid. The worst seals were found using Gluma and Superbond liquid only. Clearfil PhotoBond, Amalgambond, and Scotchbond 2 gave intermediate results. Although the dentin bonding agents tend to accumulate on chamfers, thereby increasing their thickness to 200-300 microns, the method looks promising as a simple way to protect the pulp from the consequences of microleakage.
Analysis of Variance↗
The relationship between dentin bond strengths and dentin permeability.
The relationship between dentin permeability and the shear bond strength of Scotchbond/Silux was investigated. In the presence of a smear layer, there was no correlation between dentin permeability and dentin bond strengths. After removal of the smear layer with acids, there was an inverse relationship between dentin permeability and dentin bond strength. The bond strengths were high when dentin permeability was low and decreased as dentin permeability increased. Creation of smear layers with abrasive paper or dental burs reduced permeability by 80-85%. When Scotchbond/Silux bonds were made to such smear layers and then broken, the permeability of the dentin remained low. If the smear layer was removed by acid-etching prior to bonding, the permeability increased. When these bonds were broken, the permeability of the dentin remained elevated.
Adolescent↗
Scanning electron microscopy and dentinal permeability analysis of smear layer.
The aim of the present study was to evaluate the surface morphology and the permeability of dentine after different acid treatments: polyacrylic acid, maleic acid, phosphoric acid and saline solution as control. Dentine permeability was expressed as hydraulic conductance. All the acid treatments removed the smear layer and increased the dentine permeability.
Acid Etching, Dental↗
[Effect of various pretreatments for dentin bonding on dentin permeability].
Pretreatment of the dentinal surface with acidic solution is now considered to be necessary to obtain strong bonding between dentin and resin materials. Effects of various surface treatments for dentin bonding on dentinal smear removal have been reported by SEM observation. In this study, changes of dentin permeability after the surface treatments were measured using Pashley's technique. Forty-second treatments with either phosphoric acid gel, aqueous phosphoric acid, 10-3 solution or aqueous 10-20 Ca solution (10% citric acid containing 20% CaCl2) produced greater increases in dentin permeability compared with the treatments using either 10-20 Ca gel, Tenure Conditioner, Scotchprep or Gluma 2 for 40 seconds. Treatments with primers including adhesive monomers such as Scotchprep and Mirage Conditioner also increased the dentin permeability by removal of the smear layers and smear plugs. Application of a bonding agent (Clearfil Photobond) for 1 minute did not remove the smear plugs and the dentin permeability remained the same as before the treatment. The changes in dentin permeability were not predictable by SEM observation in some cases.
Acid Etching, Dental↗
A study of the dentinal permeability of the pulp chamber floor of human lower molars with separate roots.
The permeability of the dentin of the pulp chamber floor of lower molars with separate roots was studied, after instrumentation of the root canals by manual or ultrasonic techniques. The dentinal permeability was evaluated by the degree of penetration of copper ions in the tissue and quantified by methods used in morphometry. None of the combinations of irrigating solution/instrumentation technique caused an increase in the permeability of dentinal tissue in the pulp chamber region, probably because the dentin is reparative dentin, which is more amorphous and less tubular than primary dentin.
Analysis of Variance↗
The effects of calcium hydroxide on dentin permeability.
Calcium hydroxide paste was applied to human dentin in vitro to determine its effects on dentin permeability. Discs of dentin were acid-etched on both sides to permit determination of their maximum permeability. Smear layers were then applied to the enamel sides of the discs, thereby reducing dentin permeability 99%. Topical application of Ca(OH)2 paste to the smear layer reduced dentin permeability further, to levels 48% below that of untreated smear layers. When the Ca(OH)2-treated smear layers were exposed to 6% citric acid for two min, dentin permeability returned to the initial acid-etched value, demonstrating that Ca(OH)2 offers little protection to acid challenge. Treatment of acid-etched dentin with Ca(OH)2 produced a similar reduction in dentin permeability, which was restored to normal following acid challenge. Thus, Ca(OH)2 is effective at reducing the permeability of both the smear layer and of acid-etched dentin, in vitro.
Acid Etching, Dental↗
Effect of endodontic procedures on root dentin permeability.
The purpose of this study was to quantitate the sequential effects of endodontic procedures on the permeability of human root dentin in vitro. Forty single-rooted teeth were used. Both the crown and the apical 2 mm of the root were removed. The hydraulic conductance of the root before and after various endodontic procedures was measured using a fluid filtration method. Measurements were also made of dentin thickness, intracanal diameter changes, and changes in intracanal surface area. The results showed that instrumentation by K files alone or in combination with Gates Glidden drills did not alter radicular dentin permeability when the cementum remained intact. After removing the cementum, the creation of a smear layer and smear plugs on the canal surface tended to offset the expected increase in dentin permeability created by increasing the intracanal surface area and decreasing root dentin thickness. EDTA treatment inside the instrumented canal to remove the smear layer did not increase permeability significantly. The use of K files followed by Gates Glidden drills tended to remove more cervical dentin, increased the intracanal surface area, and increased the hydraulic conductance of root dentin more than the use of K files alone.
Dental Cementum↗
The effects of burnishing NaF/kaolin/glycerin paste on dentin permeability.
The effects on dentin permeability of burnishing NaF, kaolin, or glycerin, alone and in various combinations, were determined using an in vitro system. The results indicate that the important variable was not any of the constituents of the paste but the burnishing process itself. Burnishing dentin creates a partial smear layer on the dentin surface, thereby occluding the orifices of dentinal tubules sufficiently to reduce fluid movement across dentin 50 to 80%.
Acid Etching, Dental↗
Dentin permeability: effects of endodontic procedures on root slabs.
The permeability of human radicular dentin was measured as a hydraulic conductance before and after treatment with K files and before and after subsequent treatment of the endodontic smear layer with NaOCl, 50% citric acid, or 3% monopotassium-monohydrogen oxalate. Filing reduced dentin permeability 25 to 49%, respectively, depending upon whether outer or inner root dentin was filed. The permeability of these smear layers was unaffected by 5% NaOCl but increased many times after treatment with 50% citric acid for 2 min. Oxalate treatment lowered root dentin permeability to levels below that produced by creation of smear layers due to the production of a crystalline precipitate.
Adult↗
Effects of CO2 laser energy on dentin permeability.
The effect of a CO2 laser on the structure and permeability of smear layer-covered human dentin was evaluated in vitro. Three different energy levels were used (11, 113, and 566 J/cm2). The lowest exposure to the laser energy increased dentin permeability, measured as a hydraulic conductance, due to partial measured as a hydraulic conductance, due to partial loss of the superficial smear layer and smear plugs. The intermediate energy level also increased dentin permeability by crater formation, making the dentin thinner. The lack of uniform glazing of the surface of the crater, leaving its surface porous and in communication with the underlying dentinal tubules also contributed to the increase in dentin permeability seen with the intermediate laser energy. The highest laser energy produced complete glazing of the crater surfaces and sealed the dentinal tubules beneath the crater. However, it also completely removed the smear layer in a halo zone about 100-microns wide around each crater which increased the permeability of the pericrater dentin at the same time it decreased the permeability of the dentin within the crater. The combined use of scanning electron microscopy and permeability measurements provides important complementary information that is essential in evaluating the effects of lasers on dentin.
Adolescent↗
[Review of studies of enamel and dentin permeability to bacteria and bacterial toxins].
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Bacteria↗
[Changes in dentin permeability for microorganisms during caries treatment].
Effects of a number of chemicals and of the time elapsed since the preparation on dentine permeability for microorganisms were under study. Dentine permeability was found the highest immediately after the preparation and after acid treatment. Potassium oxalate and calcium hydroxide reduced dentine permeability.
Animals↗
Dentinal permeability in assessing therapeutic agents.
The measurement of dentinal permeability has been useful in confirming the mechanism of the hydrodynamic hypothesis for pain transmission in hypersensitive patients, has advanced our understanding of how neural agents can reach the pulpal nerves, and has provided useful data to compare and evaluate therapeutic agents. Methods to assess permeability have varied from direct dye penetration techniques to measurement of fluid flow through dentin sections to SEM photography of impression replicas in vivo. A number of clinical therapeutic strategies have emerged from this work as well as ways to mitigate the progressive nature of the condition.
Dentin↗
Measurement of dentin permeability and wetness by use of the Periotron device.
The ability of the Periotron device to measure changes in dentin permeability and wetness was evaluated by use of extracted human teeth in vitro. Pulpal pressures were varied from zero to 40 cm H2O for simulation of different pulpal tissue pressures. Non-physiologic pulpal pressures of 703 cm H2O were used for comparison of dentin permeability measurements made with the Periotron device with those made using micropipettes. Measurements made with the Periotron device correlated well with methods used previously for measurement of dentin permeability. The shear bond strength of Scotchbond 2/Silux was measured 24 h after being bonded to dentin held at zero pulpal pressure. There was an inverse correlation between the shear bond strengths of Scotchbond 2/Silux and Periotron values, suggesting that increased wetness decreases the bond strength of that system. The Periotron device offers a new, simple, convenient measure of dentin surface wetness which may be useful in dentin bonding studies.
Adhesiveness↗
Dentin permeability: effects of crown preparation.
Sequential crown reductions of extracted human teeth were made to evaluate both regional differences in dentin permeability and the effects of tooth reduction. Two different methods of tooth reduction were used. In group 1, tooth reduction was nonuniform but was done in a manner similar to conventional crown preparations. Maximum, total crown permeability was measured using a pressurized fluid filtration technique after removing the smear layer. Regional reductions in permeability were accomplished by creating smear layers on mesial, distal, buccal, lingual, and occlusal surfaces sequentially. Between each step, changes in dentin permeability were measured. In group 2, tooth reductions were uniform and regional permeability was reduced by localized application of potassium oxalate. Both methods demonstrated increased permeability of dentin as the prepared surfaces approached the pulp chamber. Generally, the mesial surfaces were more permeable than the distal surfaces. The occlusal and lingual surfaces were the least permeable regions.
Adult↗
Effects of high-speed cutting on dentin permeability and bonding.
The effects of high-speed cutting by use of a diamond bur with or without water coolant or sanding by 80-grit SiC paper on dentin permeability, before and after surface treatment, and dentin bonding of adhesive resins were compared. Three different bonding systems were used: Scotchbond DC, which requires no removal of smear layers, and two others, Clearfil Photobond and Superbond C&B, both of which remove smear layers (phosphoric acid gel or 10% citric acid containing 3% ferric chloride, respectively). Creation of smear layers by bur cutting or sanding reduced dentin permeability to levels that were only 1-3% of the maximum permeability values. Scotchbond DC gave low but consistent bond strengths (3.7-6.1 MPa) to dentin covered with smear layers. Clearfil PHotobond also produced consistent bond strengths (8.6-9.4 MPa). The increase in the permeability of dentin after phosphoric acid treatment was higher when the SiC paper was used (146%) than when the high-speed bur was used (87-90%). The smear layer and smear plugs produced by the diamond bur were more resistant to 10-3 treatment than were the SiC-created smear layers. The bond strengths of Superbond showed the highest bond strengths to the conditioned dentin when the high-speed cutting was used with water coolant (16.3 MPa), compared with the other two groups (12.2-12.5 MPa).
Analysis of Variance↗