Biomedical subjects

D H Pashley

Publications and source records attributed to D H Pashley.

At least 19 recordsLinked to original sources

PubMed1992

Effects of dentin surface treatments on the shear bond strength of Vitrabond.

The influences of nine dentin surface treatments were evaluated on the shear bond strength of a new light-cured glass-ionomer cement (GIC) and on the SEM morphology of the treated dentin surfaces. The following treatments were performed: saline solution (control), NaOCl, acidic glycine, EDTA, malic acid, malic acid plus glycine, polyacrylic acid, tannic acid, and neutral+acidic oxalate solutions. Buccal dentin surfaces were polished with #320-grit abrasive paper, treated with one of the chemicals, washed, and air-dried. Cylindrical GIC samples were then applied to the dentin surface, stored in 100% humidity, and tested after 24 h. SEM observations demonstrated no effect of saline or NaOCl treatment on the smear layer but its complete removal with exposure of collagen fibrils after malic or malic acid plus glycine treatment. Partial removal of the smear layer occurred following glycine treatment and with tannic or polyacrylic acids. Complete removal of the smear layer was seen after EDTA or pyruvic acid treatment. Oxalate treatment produced a layer of crystals, which completely covered the dentin surface. Shear bond strength of GIC was significantly increased only by treatment with the oxalate solutions.

Dental Bonding↗

PubMed1992

Relationship between bond strength and microleakage measured in the same Class I restorations.

Microleakage measurements were made by use of a pressurized fluid method in Class I restorations prepared in extracted human teeth just prior to measuring the tensile bond strengths of the same restorations. The restorative materials included dentin bonding systems that are applied to smear layers as well as those which remove the smear layer. A light-cured glass-ionomer cement was also included. The results demonstrated that there was an inverse relationship between dentin bond strength and microleakage in some materials and that the bond strengths made to three-dimensional Class I cavities were much lower than those made to flat dentin surfaces. Measurement of microleakage by fluid filtration had no apparent effect on bond strength.

Adhesives↗

PubMed1992

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↗

PubMed1992

Response of pulpal blood flow to intra-arterial infusion of endothelin.

Laser Doppler flowmetry was used to determine the effect of the vasoconstrictor endothelin 1 (ET-1) on the pulpal blood flow of intact dogs' teeth during mandibular arterial infusion. ET-1 produced a profound decrease in pulpal blood flow of a relatively long duration at lower doses than similar infusions of norepinephrine. The decrease in pulpal blood flow in response to ET-1 was partially attenuated by the calcium channel blocker nifedipine. These findings demonstrate the presence of receptors for ET-1 in the microvasculature of the dental pulp and suggests that ET-1 may function in the local control of the pulpal microcirculation.

Animals↗

PubMed1992

Medication of the dental pulp: a review and proposals.

For years, dentists have desired to treat the intact dental pulp. Since it is well-known that many substances, including some drugs, are capable of permeating dentin, we believe it is possible to treat certain types of pulpitis by applying drugs at the base of cavity preparations. Useful drugs include local anesthetics to block pain transmission, glucocorticoids or non-steroidal anti-inflammatory agents (NSAIA) to treat inflammation, NSAIA or narcotic analgesics for pain control, and antibiotics to treat infection. The literature is reviewed and proposals are presented to study medication of the dental pulp.

Administration, Topical↗

PubMed1992

Dentin bonding agents.

Dentin bonding is discussed both in terms of the substrate and in terms of newer bonding systems that have recently been marketed. The most popular bonding systems are presented along with several new systems from Germany and Japan. Etching of dentin is discussed in terms of both its advantages and its disadvantages. Bonding systems can be used to repair fractured teeth as well as to restore carious teeth. This area of knowledge is rapidly expanding. Most of the new products are improvements over their predecessors.

Acid Etching, Dental↗

PubMed1992

Effects of aluminum oxalate/glycine pretreatment solutions on dentin permeability.

Aluminum oxalate buffered with glycine to pH 0.5-2.5 has been proposed as a dentin pretreatment for the Gluma bonding system. In this experiment, the effects of 1-minute treatments of smear layers with these aluminum oxalates on the permeability of human dentin were determined in vitro. The aluminum oxalate solutions at pH 0.5-1.5 removed most of the original smear layer but occluded the tubules with crystalline deposits which decreased dentin permeability. Those solutions used at pH 2.0 and 2.5 increased dentin permeability. All dentin pretreatments increased dentin permeability when measured after a 24-hour storage period, especially the solutions at pH 2.0 and 2.5. The SEM correlates of these permeability changes indicated that these solutions remove the smear layer but reocclude the tubules with precipitates which are probably different forms of calcium oxalate, aluminum phosphate and calcium phosphates.

Adult↗

PubMed1992

Effect of warm air on the shear bond strength of composite resins.

This investigation evaluated the operating characteristics of a recently introduced tooth dryer and its effect on the bond strength of three composite resins to etched enamel. The effect of varying air pressure, distance from the tip of the tooth dryer, and distance laterally from mid-air stream on temperature were measured using a rapid-response thermocouple. Specimens were subjected to shear forces either immediately after bonding or after 5 days of water storage. The air stream required from 32 to 41 seconds to reach maximal temperature; however, more than 90% of the maximal temperature was obtained in 20 seconds. There was an increase in temperature with increased air pressure and a decrease in temperature with increasing distance from the tip. The temperature dropped rapidly laterally from the center of the air stream. The shear bond strength measurements were significantly higher for the specimens prepared using the tooth dryer for one composite resin tested immediately after bonding; there was no statistically significant difference for the other resins. The effect of warm air on the shear bond strength of composite resins to etched enamel may be dependent on the resin used and the time between bonding and testing.

Air↗

PubMed1992

Interactions of conditioners on the dentin surface.

The distinction between dentin conditioners and primers has become blurred as agents have been combined to simplify the steps required in dentin bonding. Most bonding systems use acidic conditioners designed to remove the smear layer and demineralize the dentin surface. It would seem desirable to reduce the acid concentration and/or application time to the minimum required to obtain maximum bond strengths and minimum microleakage. The pulpal effects of acidic conditioners seem to be minimal if the subsequently placed bonding agents and resin composites truly seal dentin. Several systems have been designed to be bonded to smear layers, including the new light-cured glass-ionomer cements. More research is needed to develop methods of strengthening smear layers and the bonds between them and adhesive resins.

Acid Etching, Dental↗

PubMed1992

Smear layer: overview of structure and function.

Smear layers are created on hard tissues whenever they are cut with hand or rotary instruments. This thin (1-2 microns) layer of denatured cutting debris is very tenacious and, in fact, is often the surface to which restorative materials are luted. The solubility characteristics, chemical reactivity and the structure-function relationships of this layer have not yet been well-defined. During creation of the smear layer, cutting debris is forced variable distances into dentinal tubules. These so-called smear plugs, together with the smear layer decrease dentin permeability, dentin sensitivity and surface wetness. Bonding adhesive resins to smear layers appears to limit the theoretical bond strength unless the smear layers are loosened or partially removed. Future research in this area will include the use of surface analytical techniques such as Auger electron spectroscopy and ESCA. These techniques are required because of the thinness of the smear layer. It is clear that the nature of this critical interface between dental materials and cut hard tissues remains largely unknown. This field will provide fertile ground for future research.

Animals↗

PubMed1992

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↗

PubMed1992

Dentin wetness, permeability and thickness and bond strength of adhesive systems.

This study evaluated the shear bond strength of Scotchbond 2, Clearfil PhotoBond, Tenure, All-Bond and Vitrabond and their sensitivity to dentin permeability, wetness and thickness. Occlusal dentin was prepared from extracted human teeth that were connected to a hydraulic pressure apparatus. Dentin permeability was calculated as a fluid flow rate and dentin surface wetness was evaluated using the Periotron device. Dentin thickness was measured using a pincer caliper. Shear bond strength was tested after 24 hours storage under hydrostatic pulpal pressure. Several significant correlations were found between dentin wetness, dentin permeability and remaining dentin thickness and the shear bond strengths of Scotchbond 2, Tenure and All-Bond/no etch. No apparent correlations were observed for the other adhesive systems.

Acid Etching, Dental↗

PubMed1991

Fluid and protein flux across the pulpodentine complex of the dog in vivo.

Dentinal fluid volume and protein concentrations were measured from cavities prepared in the dentine of dog molars. Fluid was collected under spontaneous conditions, during the application of negative pressures, and during a recovery period. The data allowed the calculation of dentine permeability as hydraulic conductances, fluid flux, protein flux, reflection coefficients and pulpal tissue pressures. In general, the protein concentration of dentinal fluid was about one-fifth that of plasma during spontaneous conditions and it fell when fluid flux was increased by the application of external negative pressures. The collection and analysis of dentinal fluid looks promising as a non-invasive method of assessing the state of the underlying pulp.

Animals↗

PubMed1991

Clinical correlations of dentin structure and function.

Dentin, a porous, fluid-filled mineralized tissue, may provide critical mechanical support to overlying enamel. Once the enamel or cementum surface seals are lost by disease or trauma, the same organization that provided critical mechanical support then becomes a liability, offering millions of fluid-filled diffusion channels from the periphery directly to the pulp. If restorative materials placed in cavities do not seal the dentin, there is a fluid-filled continuum from the cavosurface margins, around gaps between the restorative material and the tooth, to dentin surfaces, then through dentin via its tubules to the pulp. Under most conditions these channels permit bidirectional diffusion of exogenous and endogenous substances across dentin. Occasionally, hydrodynamic stimuli will produce transient, rapid movement of dentinal fluid that will induce pain. The tubules are sometimes so close together in deep dentin that their intrinsic wetness interferes with the bonding of adhesive resins. This permits the formation of gaps, microleakage, dentin sensitivity, and, occasionally, pulpal irritation. Many clinical problems such as poor dentin bonding, microleakage, dentin sensitivity, and pulpal irritation have a common denominator in the structure and function of dentin.

Dental Materials↗

PubMed1991

Shear bond strength of Scotchbond in vivo.

The shear bond strengths of Scotchbond, HEMA/Scotchbond, and Scotchbond 2 were measured in vivo in dog canine and molar enamel and dentin. Dentin bond strengths were compared in superficial, middle, and deep dentin. The acid-etched enamel bond strengths of the three bonding systems ranged from 10 to 11 MPa and were not statistically different. Scotchbond/Silux bonds to superficial and middle cuspid and molar dentin were 3 MPa and were not statistically different. HEMA-treated dentin did not consistently improve Scotchbond strengths to either tooth type at any dentin depth. Deep dentin from either tooth type yielded significantly lower bond strengths. Scotchbond 2/Silux shear bond strengths were significantly higher (6-8 MPa) in superficial and middle cuspid dentin but were not different from Scotchbond bonds made to deep cuspid dentin or to any depth of molar dentin. The observation that molar bond strengths are lower than those made to cuspid dentin indicates that there are important substrate differences between teeth as well as within dentin as a function of depth. The dog model may be useful for the screening of new dentin bonding systems prior to clinical trials.

Animals↗

PubMed1991

Hydrostatic intrapulpal pressure and bond strength of bonding systems.

The purpose of this study was to evaluate the effect of intra-pulpal pressure on shear bond strength of three light-cured glass-ionomer cements (GC lining cement, Vitrabond, and Zionomer) and four dentin bonding agents [Gluma/Scotchbond, Scotchbond 2, MBL, and Clearfil Photo Bond]. Buccal dentin surfaces were prepared just below the DEJ by means of a diamond bur. Dentin treatments were made for Zionomer (Zionomer conditioner), Scotchbond 2 (Scotchprep), MBL (10-3 solution), Clearfil PB (H3PO4), GC lining cement (Polyacrylic acid), and Gluma/Scotchbond (EDTA). Resin composites were inserted into tubes, positioned on dentin, cured, tested after five min or 24 h, and compared with samples bonded and stored under an intra-pulpal pressure of 36 cm of saline. After 24 h in superficial dentin, intrapulpal pressure reduced the bond strength only in MBL, Scotchbond 2, and Zionomer. Clearfil PB bond strength was increased, while Vitrabond, GC lining cement, and Gluma/Scotchbond were unaffected by the presence of pulpal pressure. However, in deep dentin, Scotchbond 2 and Clearfil PB shear bond strengths were significantly reduced by storage in the presence of 36-cm H2O pulpal pressure. Only Vitrabond remained unaffected by pulpal pressure in deep dentin.

Composite Resins↗

PubMed1991

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↗

PubMed1991

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↗