Biomedical subjects

H Hisamitsu

Publications and source records attributed to H Hisamitsu.

At least 37 records · Page 2Linked to original sources

PubMed1997

In vitro inhibition of caries around a resin composite restoration containing antibacterial filler.

Class V cavities were prepared and restored with resin composite containing antibacterial filler powder (Apacider-AW, Ap-AW) using experimental restorations. The restored teeth were incubated in vitro with the cariogenic bacteria Streptococcus mutans IFO 13955. Ground sections were then prepared and examined using macrophotography. Lesions of the outer and inner wall were noted, and the depths of which the lesions penetrated were measured. We found that, in restorations containing 1-5 wt% Ap-AW, caries penetrated the marginal area, while in restorations containing 10 wt% Ap-AW the margin remained free of caries out to a distance of about 1.1 and 1.8 mm on the occlusal and gingival sides, respectively.

Biocompatible Materials↗

PubMed1997

Effects of polyvalent alcohol solutions as dentine primers.

OBJECTIVES: The purpose of this study was to examine the bonding effect of polyvalent alcohols as dentine primers without a methacrylate group, which may cause contact dermatitis. METHODS: The efficacy of polyvalent alcohols as dentine primers was estimated by measuring the wall-to-wall polymerization contraction gap width of a light-activated resin composite filled in a cylindrical dentine cavity in an extracted human tooth. A dentine cavity was cleaned with ethylenediaminetetraacetic acid (EDTA) and primed with an aqueous solution of either ethylene glycol, glycerol, erythritol, xylitol or sorbitol at concentrations of between 25 and 75 wt%. A light-cured resin composite was filled after the application of a commercial dual-cured bonding agent. RESULTS: Contraction gap formation was completely prevented only in the group in which the dentine cavity had been primed with an aqueous solution of 62.5% wt% ethylene glycol. Furthermore, in the measurement of a tensile bond strength to a flat dentine surface, high tensile bond strength (17.5 +/- 4.4 MPa) was observed in the group that was primed with 62.5% ethylene glycol solution. CONCLUSION: These results suggest that it is not necessary to dissolve methacrylates in a dentine primer when the primer is dried with a blast of compressed air before application of a polymerizable, suitable bonding agent. It is concluded that a dentine primer composed of polyvalent alcohol solutions without a methacrylate group which may cause contact dermatitis, is effective as a dentine primer, affects the dentine surface, and promotes the efficacy of the dentine bonding system.

Acid Etching, Dental↗

PubMed1996

Contact dermatitis caused by 2-HEMA and GM dentin primer solutions applied to guinea pigs and humans.

The purposes of this study were to examine whether 2-HEMA, GM, and methacrylic acid cause contact dermatitis, and to determine the optimum concentrations of these primers for sensitization and challenge in guinea pigs. A sensitizing concentration of 0.2% 2-HEMA resulted in strong rubefaction and several vesiculopapules in response to the challenge, and a sensitizing concentration of 0.5% GM produced strong rubefaction at 24 hours. We also observed the development of contact dermatitis on human brachia in a closed-patch test. Skin that was treated with both 2-HEMA and GM clearly showed the onset of rubefaction and itchiness. 2-HEMA caused sensitized delayed allergic reactions at all the concentrations tested.

Animals↗

PubMed1996

Evaluation of skin irritation and sensitization of two diol solutions used as experimental dentin primers in humans and guinea pigs.

The purpose of the present study was to evaluate the safety of ethylene glyco (EG) and 1,6-hexanediol (HD) solutions as experimental dentin primers when subjected to the guinea pig maximization test (GPMT), primary irritation test, cumulative skin irritation test and human patch test. No primary and cumulative skin irritation resulting from the use of 62.5% EG or 45% HD solutions was observed. In the case of GPMT, the animals sensitized with 2-hydroxyethyl methacrylate (2-HEMA) responded to 100% HD. 62.5% EG and 45% HD as dentin primers were safer than 2-HEMA such as a methacrylic primer.

Adult↗

PubMed1996

Contact angle of dentin bonding agents on the dentin surface.

Physical changes in the surface characteristics of dentin during bonding procedures were evaluated by measuring the contact angles of three standard liquids, to determine the surface free energy, and that of a commercially available dual cured dentin bonding agent dropped on the primed dentin surface. The commercial dentin bonding agent did not form a hemispherical shape on the ground dentin surface, probably because it penetrated into the smear layer due to the microcapillary effect. Not could the contact angle be measured on the dentin surfaces treated with any of four experimental primers, because the bonding agent rapidly spread over the primed dentin surface. It was concluded that the priming of the dentin surface after removing the smear layer served to increase the surface free energy and to improve the wettability of the bonding agent on the dentin.

Chemical Phenomena↗

PubMed1995

A delayed hypersensitivity reaction to dentine primer in the guinea-pig.

OBJECTIVE: This study was undertaken to examine the possibility of a delayed hypersensitivity reaction or contact dermatitis occurring in the guinea-pig in response to methacrylate derivatives used as experimental dentine primers. METHODS: The dentine primers 2-HEMA, GM, MA and MMA were tested in a guinea-pig maximization test. RESULTS: All the dentine primers tested produced positive delayed hypersensitivity reactions in the guinea-pig. MMA produced the most severe reaction. CONCLUSION: It is concluded that in the clinical situation, clinicians and other members of the dental team should be aware of the need for careful handling of the dentine primers tested.

Animals↗

PubMed1995

Duration of cleaning and priming of dentine and contraction gap formation.

OBJECTIVES: The effects of the duration of cleaning and priming on the marginal adaptation of a light-activated resin composite in a cylindrical dentine cavity were examined by measuring the width of the wall-to-wall polymerization contraction gap. METHODS: The dentine cavity was cleaned with ethylene diamine tetra-acetic acid (EDTA) and primed 35 vol% hydroxyethyl methacrylate (HEMA) or glyceryl methacrylate (GM) solution for up to 60 s. The cavity was filled with a light-cured resin composite after the application of a dual-cured dentine bonding agent. RESULTS: The formation of a contraction gap by the composite appeared to be prevented completely, regardless of the duration of priming with GM solution, when the cavity was cleaned with EDTA for 60 s. When cleaning was limited to just 30 s, GM priming had to be prolonged to 60 s to obtain complete marginal integrity. A significantly wide contraction gap was observed without EDTA cleaning, even when the cavity wall was primed with GM solution for 60 s. CONCLUSION: GM solution was a better dentine primer than HEMA solution, since HEMA priming did not prevent gap formation under any of the conditions tested.

Acid Etching, Dental↗

PubMed1995

Water content in experimental dentine primers to minimize the contraction gap width of a light-cured resin composite.

OBJECTIVES: The effect of water content in experimental dentine primers consisting of an aqueous solution of either glyceryl methacrylate (GM) or hydroxyethyl methacrylate (HEMA), and in experimental self-etching dentine primers composed of methacryloxyethyl hydrogen phenyl phosphate (Phenyl-P), was evaluated by measuring the wall-to-wall polymerization contraction gap width of a commercial light-activated resin composite filled in a cylindrical dentine cavity prepared in an extracted human molar. METHODS: A commercial light-cured dentine bonding agent was applied to the cavity after cleaning with EDTA and priming with either GM or HEMA, or after self-etching priming by Phenyl-P diluted in either GM or HEMA solution. RESULTS: In the GM and HEMA solutions, the gap width was minimized when the water content was 65 wt% even though gap formation could not be prevented by HEMA solution. With the self-etching dentine primers, gaps could not be observed under the light microscope with 16 wt% Phenyl-P diluted in 35 wt% GM or HEMA or with 20 wt% Phenyl-P diluted in 20 wt% GM or HEMA. CONCLUSION: The water content in both the experimental dentine primers and the self-etching dentine primers which yielded the minimum contraction gap width for the resin composite in the dentine cavity was approximately 60 wt%.

Composite Resins↗

PubMed1995

Optimum concentration and application time of 1,6-hexanediol as a dentin primer.

The optimum concentration and application time for an experimental dentin primer composed of an aqueous solution of 1,6-hexanediol were determined by measuring the wall-to-wall polymerization contraction gap width of a commercial light-activated resin composite in a cylindrical dentin cavity prepared in an extracted human molar. Contraction gap formation was completely prevented only when the dentin cavity wall was primed with 45 wt% 1,6-hexanediol for 60 s. There were no significant differences in tensile bond strength among primers composed of 20.0-57.5 wt% 1,6-hexanediol. These results suggest that the optimum concentration and application time are 45 wt% and 60 s, respectively.

Analysis of Variance↗

PubMed1994

Efficacy of various commercial dentin bonding systems.

OBJECTIVES: The purpose of this study was to test the bonding efficacy of fifteen commercial dentin bonding systems and also to determine the effect of various commercial dentin cleaners on bonding and dentin hardness. METHODS: Each commercial bonding system was examined by two methods: 1) measuring the maximum contraction gap of a light-cured composite in a cylindrical dentin cavity; and 2) determine the tensile bond strength to a flat dentin surface. In addition, various commercial dentin cleansers were investigated to determine if dentin hardness was reduced after cleaning. As a control, the dentin surface was cleaned with neutralized EDTA prior to the combined application of an experimental dentin primer, a commercial bonding agent, and a commercial light-cured composite. RESULTS: The study demonstrated that complete marginal adaptation was obtained by the experimental dentin bonding system used as the control. However, it was not possible to completely prevent gap formation with the commercial dentin bonding systems tested. A high correlation (R = 0.88) was observed between maximum contraction gap width and reduction of hardness only in the group in which the dentin was rinsed after cleaning. SIGNIFICANCE: It is very important to combine optimal dentin cleansers, primers, and bonding agents to compensate for the polymerization contraction stress of the composite. Therefore, it was speculated that the commercial dentin bonding systems tested in this study consisted of unsuitable materials.

Acid Etching, Dental↗

PubMed1994

Self-etching dentin primers containing phenyl-P.

The dentin bonding efficacies of two commercial dentin bonding systems and experimental self-etching dentin primers composed of methacryloxyethyl hydrogen phenyl phosphate (Phenyl-P) and either hydroxyethyl methacrylate (HEMA) or glyceryl methacrylate (GM,2,3-dihydroxypropyl methacrylate) were examined. The wall-to-wall polymerization contraction gap width of a commercial light-activated resin composite in a cylindrical dentin cavity and the tensile bond strength to a flat dentin surface were measured. Changes in dentin hardness were determined by Micro Vickers Hardness measurement, and an SEM observation was performed after priming. Formation of a contraction gap was completely prevented by the application of Phenyl-P diluted in HEMA or GM solution combined with a commercial dentin bonding agent, although gap formation was evident in nearly half of the specimens with both commercial dentin bonding systems. The mean tensile bond strengths of the tested groups varied from 16.3 to 20.7 MPa, and there were no significant differences between groups. Based on the measurement of Micro Vickers Hardness and SEM observation after priming, a slight reduction in dentin hardness was observed. However, this reduction in dentin hardness due to self-etching priming did not significantly correlate with either contraction gap width or tensile bond strength.

Acid Etching, Dental↗

PubMed1994

Effect of filler content on bonding efficacy of 4-META MMA/TBB bonding agent.

The effect of adding micro filler to 4-META MMA/TBB dentin bonding agent was examined by measuring the wall-to-wall polymerization contraction gap of a commercial light-cured resin composite in a cylindrical dentin cavity and the tensile bond strength of the flat dentin surface. Gap formation was not completely prevented by using a filled dentin bonding agent although the tensile bond strength was significantly greater than that obtained using the unfilled dentin bonding agent. These results indicate that the addition of micro filler to the dentin bonding agent does not produce complete adaptation of the resin composite to the dentin cavity wall.

Acrylic Resins↗

PubMed1993

Factors affecting tensile bond strength of composite to dentin.

Five factors which might affect the tensile bond strength of an experimental dentin bonding system to extracted human dentin were evaluated. Flat dentin surfaces of extracted human teeth were cleaned with 0.5 mol/L EDTA and pretreated with 35% glyceryl methacrylate solution. A commercial light-activated composite was then bonded using a commercial bonding agent. The five evaluated factors were: 1) embedding or not embedding the specimens in an epoxy resin, 2) thickness of the specimens, 3) crosshead speed during measurement, 4) storage time of the specimens, and 5) dentin substrate depth. Measurements were made of the bond strengths that resulted from the effects of these varied factors. These measurements were compared to a control group. Only the specimen thickness significantly affected the measured bond strength, and extremely thin specimens (about 1 mm) showed the lowest bond strength.

Composite Resins↗

PubMed1993

Effect of delayed light curing of a resin composite on marginal integrity in cylindrical dentine cavities.

The effect of delayed light curing of resin composite on marginal adaptation has been examined by measuring the wall-to-wall polymerization contraction gap when using a commercial resin composite together with experimental dentine bonding systems to restore cylindrical preparations in dentine. Morphological changes in dentine during dentine bonding procedures were observed using a scanning electron microscope. In a previous report, the contraction gap width for a resin composite increased when irradiation of the resin system was delayed, despite the use of a dentine bonding system considered to be 'contraction' gap free. Such deterioration in marginal adaptation was minimized by use of an experimental dentine primer, 40% erythritol methacrylate aqueous solution (EM), followed by the use of a commercial dual- or autocured dentine bonding agent. Under scanning electron microscopy, the dentine surface microstructure became unclear after EM priming, and a polymer film was detected after polymerization of the dual-cured dentine bonding agent. The hydrogelled primer and the formation of a polymer network on the dentine surface may prevent the flow of fluid from the pulp through the dentine tubules, and maintain marginal integrity if there is delay in light curing of light-activated resin composite systems.

Analysis of Variance↗

PubMed1993

Efficacy of dentin bonding agents combined with self-etching dentin primers containing Phenyl-P.

The bonding efficacies of three commercial dentin bonding agents and an intermediate resin combined with two self-etching dentin primers (aqueous solutions of methacryloxyethyl hydrogen phenyl phosphate (Phenyl -P, 20 wt%) and either hydroxyethyl methacrylate (HEMA, 35 wt%) or glyceryl methacrylate (GM, 35 wt%)) were examined by measuring the wall-to-wall contraction gap of a light-activated resin composite in a cylindrical dentin cavity prepared in extracted human teeth. Among the tested bonding agents, only one material showed complete adaptation between the resin composite and the dentin cavity margin i. e. a dual -cured agent that contained 10-methacryloxydecyl dihydrogen phosphate (MDP). The contraction gap of the intermediate resin was significantly reduced by pretreatment with the experimental self-etching dentin primers containing Phenyl-P.

Acid Etching, Dental↗

PubMed1993

Shear bond strength of composite resin to unbleached and bleached human dentine.

The purpose of this study was to compare the shear bond strength of composite resin to unbleached and bleached human dentine when used in conjunction with new dentine bonding systems. One hundred extracted, caries free, permanent human molars were used in this study. An in vitro walking bleach model was developed to stimulate clinical conditions during bleaching. It was found that the mean shear bond strength of composite resin to bleached dentine attained was lower than that to unbleached dentine. The value of 6.7 MPa bond strength to bleached human dentine demonstrated by All-Bond dentine conditioner and adhesive (Technique 1B) was much higher than in previous reports.

Borates↗

PubMed1992

Wind-up of tooth pulp-evoked responses and its suppression in rat trigeminal caudal neurons.

Induction and suppression of wind-up were studied in 97 tooth pulp-driven neurons in the trigeminal subnucleus caudalis, using Wistar albino rats anesthetized with urethane and alpha-chloralose. Tooth pulp stimulation applied to an ipsilateral lower incisor evoked early discharges, indicating excitatory inputs from A-delta fibers and subsequent late discharges from C-fiber volleys in caudal neurons. Wind-up was efficiently evoked by stimulation delivered at 0.3-1 Hz, with current intensity sufficient to evoke late discharges. Conditioning stimulation of the arcuate nucleus of the hypothalamus (ARH) suppressed late discharges, including wind-up, without affecting the A-fiber response. Focal cooling of the periaqueductal gray (PAG) abolished the suppression by the ARH and further enhanced the wind-up of the caudal neurons. These results suggest: 1) Temporal summation of depolarization evoked by C-fiber volleys builds wind-up in caudal neurons; 2) ARH stimulation suppresses late discharges by blocking synaptic transmission from C-fiber inputs, and this interrupts prolonged facilitation of the neurons; 3) the ARH is involved in induction of inhibitory controls descending from the PAG to the trigeminal caudalis.

Animals↗

PubMed1992

Laser-Raman spectroscopic study of the adhesive interface; analysis between 4-META/MMA-TBB resin and bovine or human dentin.

A study of the adhesive interface between 4-MET/MMA-TBB resin and hydroxyapatite or bovine enamel was reported. The present report is a continuation of that study. The possible chemical interaction between 4-methacryloxyethyl trimellitic acid (4-MET) and bovine or human dentin was examined by laser Raman spectroscopy. A 4-MET monomer solution was prepared by evaporating two thirds of the methyl methacrylate (MMA) in a commercial dentin adhesive. The solution was then applied to a dentin surface after treating the surface with an aqueous solution of 10% citric acid containing 3% ferric chloride. A salt formed on both bovine and human dentin surfaces. This salt was formed by the process we previously reported in which 4-MET formed a salt on the hydroxyapatite and bovine enamel. No evidence was observed of chemical reaction between 4-MET and any organic component in the dentin.

Acrylic Resins↗