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Biomedical subjects

D H Pashley

Publications and source records attributed to D H Pashley.

At least 19 recordsLinked to original sources
PubMed1995

Effect of bisphosphonates and gallium on dentin resorption in vitro.

Replacement resorption may follow the replantation of an avulsed tooth. Currently there is no effective treatment for replacement resorption. The purpose of this study was to investigate the effect of bisphosphonates and gallium nitrate, which have been shown to reduce bone resorption, on cells which resorb dentin. Osteoclast-like cells were obtained by culturing cells from prenatal chick tibeas. These cells were seeded onto slices of human dentin which had been soaked in either saline (control), or solutions of 10(-5) M 1-hydroxyethylidene-1, 1-bisphosphonic acid (EHBP), 10(-6) M dichloromethylene bisphosphonic acid (Cl2MBP), or 10(-6) M gallium nitrate. Resorption was measured by counting the number of resorptive lacunae produced by the cells. Results indicated that the experimental groups did not differ significantly from each other, but each exhibited significantly reduced resorption compared with saline controls (p < 0.01). These results suggested that the experimental treatment reduced dentinal resorption by the osteoclast-like cells, and that these agents might be useful to prevent or at least postpone replacement resorption in avulsed teeth.

Animals↗
PubMed1995

Tensile properties of resin-infiltrated demineralized human dentin.

The ability of adhesive resins to restore the physical properties of demineralized dentin has not been well-documented. The unfilled resins that are used for adhesion have relatively low moduli of elasticity and limited ability to increase dentin stiffness, although they may increase the ultimate tensile strength of dentin. This study tested the hypothesis that resin infiltration of demineralized dentin can restore its tensile properties to those of mineralized dentin. Small (ca. 0.5 mm thick x 0.5 mm wide) specimens of demineralized human dentin were infiltrated with one of five different dentin bonding resins over many hours, to determine how these resins altered the tensile properties of dentin. Tensile stress and strain were measured in these and control (mineralized and demineralized) specimens until their ultimate failure. The results indicate that some adhesive resins, after infiltrating demineralized dentin, can restore and even exceed the ultimate tensile strength of mineralized dentin. These resins increased the modulus of elasticity of resin-infiltrated dentin to values equal to or greater than those of the resins but far below those of mineralized dentin. Although the conditions in this experiment were far removed from the manufacturer's recommendations or clinical practice, the results support the potential of resin infiltration for reinforcing dentin.

Acid Etching, Dental↗
PubMed1995

Tensile bond strength and SEM evaluation of caries-affected dentin using dentin adhesives.

Tensile bond strength measurements are commonly used for the evaluation of dentin adhesive systems. Most tests are performed using extracted non-carious human or bovine dentin. However, the adhesion of resins to caries-affected dentin is still unclear. The objectives of this study were to test the hypothesis that bonding to caries-affected dentin is inferior to bonding to normal dentin, and that the quality of the hybrid layer plays a major role in creating good adhesion. We used a micro-tensile bond strength test to compare test bond strengths made to either caries-affected dentin or normal dentin, using three commercial adhesive systems (All Bond 2, Scotchbond Multi-Purpose, and Clearfil Liner Bond II). For scanning electron microscopy, the polished interfaces between the adhesive bond and dentin were subjected to brief exposure to 10% phosphoric acid solution and 5% sodium hypochlorite, so that the quality of the hybrid layers could be observed. Bonding to normal dentin with either All Bond 2 (26.9 +/- 8.8 MPa) or Clearfil Liner Bond II (29.5 +/- 10.9 MPa) showed tensile bond strengths higher than those to caries-affected dentin (13.0 +/- 3.6 MPa and 14.0 +/- 4.3 MPa, respectively). The tensile bond strengths obtained with Scotchbond Multi-Purpose were similar in normal and caries-affected dentin (20.3 +/- 5.5 MPa and 18.5 +/- 4.0 MPa, respectively). The hybrid layers created by All Bond 2 in normal dentin and by Clearfil Liner Bond II in normal or caries-affected dentin showed phosphoric acid and sodium hypochlorite resistance, whereas the hybrid layers created by All Bond 2 in caries-affected dentin and those created by Scotchbond Multi-Purpose to normal and caries-affected dentin showed partial susceptibility to the acid and sodium hypochlorite treatment. The results indicate that the strength of adhesion to dentin depends upon both the adhesive system used and the type of dentin. Moreover, the quality of the hybrid layer may not always contribute significantly to tensile bond strength.

Analysis of Variance↗
PubMed1995

The effects of intracanal medicaments, fillers, and sealers on the attachment of human gingival fibroblasts to an exposed dentin surface free of a smear layer.

To date there has been very little research into the possible effects of endodontic therapy on regeneration of the lost periodontal attachment. The objective of this study was to examine the effects of endodontic medicaments on fibroblast attachment to dentin surfaces free of a smear layer. Pulp chambers of extracted third molars were filled with one of the following medicaments: gutta-percha with Roth's zinc oxide and eugenol-based sealer, warm gutta-percha with sealer, warm gutta-percha without sealer, calcium hydroxide, formocresol, cotton pellet, or left empty. A predetermined dentin surface area was then inoculated with human gingival fibroblasts at a concentration of 2 x 10(4) cells per ml. The cells were allowed to adhere to the dentin surface for either 4 or 24 hours, then cell attachment was quantified using a methyl-tetrazolium assay. The data were analyzed using a Kruskal-Wallis one-way analysis of variance and Dunn's multiple comparison test. It was determined that fibroblast attachment was significantly reduced when exposed to formocresol or warm gutta-percha without sealer at both the 4 and 24 hour interval (P < or = 0.05). This suggests that the use of formocresol or warm gutta-percha without sealer in a root canal may impede periodontal wound healing and regeneration.

Analysis of Variance↗
PubMed1994

Dentine permeability and its role in the pathobiology of dentine sensitivity.

The classical hydrodynamic theory implicated fluid movement as a transducing mechanism in the production of dental sensitivity. This theory assumes that sensitive dentine must be permeable. Various measurements of dentine permeability are discussed, including: (1) factors that influence diffusive permeation across dentine; (2) factors that influence convective fluid movement across dentine; (3) osmotic activities of solutions; (4) comparison of evaporative and convective fluid movement; (5) the interaction between outward convective fluid flux on the inward diffusive flux of molecules; and (6) the importance of pulpal blood flow in the clearance of noxious substances from dentine and pulp, a balance concept. The variables involved in achieving good penetration of desensitizing agents in the presence of outward movement of dentinal fluid are also discussed, along with the presentation of a new hypothesis which emphasizes the importance of dentine as a dynamic physiological barrier that works in harmony with neurovascular elements in the pulp in an attempt to maintain the health of the pulp-dentine complex.

Animals↗
PubMed1994

Relationship between surface area for adhesion and tensile bond strength--evaluation of a micro-tensile bond test.

OBJECTIVES: The purpose of this study was to test the null hypothesis that there is no relationship between the bonded surface area of dentin and the tensile strength of adhesive materials. METHODS: The enamel was removed from the occlusal surface of extracted human third molars, and the entire flat surface was covered with resin composite bonded to the dentin to form a flat resin composite crown. Twenty-four hours later, the bonded specimens were sectioned parallel to the long axis of the tooth into 10-20 thin sections whose upper part was composed of resin composite with the lower half being dentin. These small sections were trimmed using a high speed diamond bur into an hourglass shape with the narrowest portion at the bonded interface. Surface area was varied by altering the specimen thickness and width. Tensile bond strength was measured using custom-made grips in a universal testing machine. RESULTS: Tensile bond strength was inversely related to bonded surface area. At surface areas below 0.4 mm2, the tensile bond strengths were about 55 MPa for Clearfil Liner Bond 2 (Kuraray Co., Ltd.), 38 MPa for Scotchbond MP (3M Dental Products), and 20 MPa for Vitremer (3M Dental Products). At these small surface areas all of the bond failures were adhesive in nature. SIGNIFICANCE: This new method permits measurement of high bond strengths without cohesive failure of dentin. It also permits multiple measurements to be made within a single tooth.

Composite Resins↗
PubMed1994

Evaluation of the bond strength of dentin bonding agents used to seal resected root apices.

A number of improved dentin bonding agents have recently become available, but have not been evaluated on apical radicular dentin. The purpose of this study was to compare the tensile bond strengths of four adhesive resins on resected root ends before and after blood contamination. Forty single-rooted human incisors were cleaned and shaped and obturated. The apical 3 mm was then resected at a 45-degree angle, bonded, and tested for tensile bond strengths using an Instron machine. The bonding systems evaluated included Prisma Universal Bond 3, Scotchbond MultiPurpose Dental Adhesive, Amalgambond, and All Bond 2. All bonding systems were then covered with Prisma APH light-cure composite resin. Results indicated that the bond strengths of the blood contaminated groups were significantly less than those of the control groups, except in the case of Amalgambond where no significant difference was noted. When the surface was contaminated with blood, Prisma Universal Bond 3 had significantly lower bond strengths, whereas Amalgambond had significantly higher bond strengths than the other subgroups.

Analysis of Variance↗
PubMed1994

In vitro and in vivo measurement of remaining dentin thickness.

Experiments were performed in vitro on extracted human teeth and in vivo on dog teeth to determine the accuracy of a pulse-echo mode with an ultrasonic micrometer in measuring remaining dentin thickness. The accuracy of the ultrasonic micrometer measured remaining dentin thickness was compared with direct caliper measurements in measuring human dentin discs (correlation coefficient, r = 0.99). After modification of the delay line tip (focusing tip), the device was found to be highly accurate on both prepared extracted human teeth (r = 0.87) and in vivo on dog teeth (r = 0.92). The use of ultrasonic technology to measure remaining dentin thickness looks promising. Further research needs to be performed to make the device more clinically useful.

Animals↗
PubMed1993

Sterilization of human teeth: its effect on permeability and bond strength.

Extracted human teeth were randomly divided into three groups. Group 1 teeth were untreated and served as controls. Group 2 teeth were sterilized in a steam autoclave. Group 3 teeth were sterilized by exposure to ethylene oxide gas. Crown segments were then prepared from these teeth by resection of the roots at the CEJ and the occlusal enamel to expose a flat occlusal plane of dentin. The permeability of the dentin was determined to be similar in all three groups. The shear bond strength of Prisma Universal Bond 3 and C&B Metabond was also similar in all groups indicating that sterilization of teeth does not alter dentin permeability or bond strength.

Boron Compounds↗
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↗