Effect of dentine conditioners on the bonding efficacy of one-bottle adhesives.

The bonding efficacy of four one-bottle adhesives (OptiBond Solo Plus, Gluma Comfort Bond, One Step and Prime & Bond NT) and a multi-step adhesive (Clearfil Photo Bond) as a control was evaluated. The dentine cavity wall was conditioned with phosphoric acid or ethylenediaminetetraacetic acid (EDTA) and the marginal integrity was estimated by measuring the wall-to-wall contraction gap width between the composite and the dentine cavity surface. In the positive control group, the adhesive was applied following glyceryl methacrylate (GM) priming. The analyses were performed by Kruskal-Wallis and Mann-Whitney U-tests. One-bottle adhesives were clearly inferior to the multi-step bonding system in marginal integrity when dentine was conditioned with EDTA. The present findings also suggested that the marginal sealing ability of ethanol-based one-bottle systems was better than acetone-based one-bottle systems when dentine surfaces were conditioned with EDTA. Nevertheless, further investigations are needed on the function of fillers in one-bottle adhesives for the prevention of contraction gaps.

Bonding efficacy and side effects of the high purity glyceryl mono-methacrylate.

The purpose of this study was to examine the efficacy of experimentally developed high purity glyceryl mono-methacrylate (GM) as a dentine primer and to evaluate the possibility of allergic reaction. The efficacy of experimental dentine primers was evaluated by measuring the polymerization contraction gap width and the tensile bond strength. Allergic reaction was evaluated by the guinea-pig maximization test. The skin reaction was evaluated according to the criteria of the International Contact Dermatitis Research Group. Contraction gap formation was completely prevented and the tensile bond strength was not significantly affected by priming with GM on high-purity GM. The allergic response decreased when high-purity GM was employed as the challenger. It was concluded that the clinical use of the high-purity GM is beneficial as the delayed allergic reaction could be avoided with no detrimental effect on the dentine bonding.

First case of a single heterozygote of an abnormal hemoglobin, Hb Stanmore, [beta111(G13)Val-->Ala].

We describe a hemoglobin beta-chain mutant detected incidentally in an unusual profile of glycated hemoglobin (HbA1c) measured by ion-exchange HPLC. Analysis of intact globin by electrospray ionization mass spectrometry (ESI-MS) and peptide analysis by on-line HPLC-ESI-MS-MS revealed the substitution, [beta111(G13)Val-->Ala], which was confirmed by DNA analysis. This was the second case of Hb Stanmore. As the first case combined beta(0)-thalassemia, and the family study in that case showed no case of Hb Stanmore without combined thalassemia, the case presented here is the first case of single heterozygote, and the first Japanese case. Hb Stanmore is isoelectrophoretically silent with only mild clinical symptoms, although stability by isopropanol test was positive.

Depth of cure and marginal adaptation to dentin of xenon lamp polymerized resin composites.

Marginal adaptation of four resin composites (Clearfil APX, Estelite, Silux Plus and Z-100) cured with two xenon lamp units (Plasma Arc Curing System or Apollo 95E) or a halogen lamp unit (Witelite) were evaluated by measuring the wall-to-wall contraction gap width. A cylindrical dentin cavity (ø3 mm x 1.5 mm) prepared in an extracted human molar was treated with the Megabond system or an experimental bonding system consisting of 0.5 M EDTA, 35% GM and Clearfil Photo Bond prior to composite filling and was irradiated for three seconds (xenon lamp) or 40 seconds (halogen lamp). The contraction gap was measured with a light microscope. In addition, the curing capability of these three light sources was evaluated by measuring the curing depth of the composites filled in a split Teflon mold (ø4 mm x 8 mm). There was no marginal gap formation for Clearfil APX, Estelite and Silux Plus treated with the experimental bonding system regardless of the type of light sources. The curing depth of the xenon lamp was significantly higher than the halogen lamp, while marginal adaptation did not suffer any significant deterioration.

Effects of soft-start irradiation on the depth of cure and marginal adaptation to dentin.

Marginal adaptation of four resin composites, Clearfil APX, Estelite, Silux Plus and Z-100 cured with two irradiation methods (soft-start or high-power start) of a commercial soft-start halogen lamp unit (Elipar Highlight) were evaluated by measurement of the wall-to-wall contraction gap width. One-hundred and sixty cylindrical cavities, 3 mm in diameter and 1.5 mm in depth, were prepared in extracted human molars. The 80 cavity walls were treated with the Megabond system and each 20 cavities were filled with one of four resin composites. Then, each 10 fillings were irradiated by the soft-start method (soft-power light for 10 seconds followed by high-power light for 30 seconds) or high-power light for 40 seconds. The other 80 cavity walls were treated with an experimental bonding system consisting of 0.5M EDTA as a conditioner, 35% glyceryl mono-methacrylate as a primer and Clearfil Photo Bond as a bonding agent. The cavities were restored wtih the four resin composites and two irradiation methods, the same as the Megabond group. The contraction gap was measured with a light microscope and expressed in % of the cavity diameter. In addition, the curing capability of these two light sources was evaluated by measurement of the curing depth of the four resin composites using a split Teflon mold 4 mm in inner-diameter and 8 mm in height. Marginal gap formation of Clearfil APX, Estelite and Silux Plus with the experimental bonding system was completely prevented regardless of the kind of irradiation methods used. The deterioration of marginal adaptation caused by the Megabond system could not be improved by use of the soft-start method programmed in Elipar Highlight.

Adverse effect of dentine bonding agent on the oral mucosa of guinea pigs.

The purpose of present study was to determine the possibility of nebulous discoloration of the oral mucosa of guinea pigs as a result of the application of dentine bonding agents. The materials used were the Clearfil Photo Bond (CPB) system's mixture agent, universal agent and catalyst agent. Four types of experimental catalysts were used. In male albino guinea pigs weighing 300-500 g, oral mucosa irritation tests were performed in accordance with the guidelines of the Cosmetic, Toiletry and Fragrance Association (CTFA). Macroscopical findings on the oral mucosa showed that there was strong nebulous discoloration immediately after application of CPB mix and CPB catalyst and throughout the experimental periods. However, CPB without 10-methacryloxdecyl dihydrogen phosphate (MDP) did not produce noticeable nebulous discoloration and inflammation. The CPB mix caused pathological changes, such as paraketosis and hyperkeratosis on the endepidermis of the mucosa, immediately after its application.

Efficacy of dentin bonding to cervical defects.

The bonding efficacy of sclerotic dentin was determined by measuring the polymerization contraction gap width of a commercial light-activated resin composite in a cervical defect and by measuring the micro-Vicker's hardness at the dentin adhesive surface; morphological characteristics were observed using a scanning electron microscope in extracted human incisors and premolars. Contraction gap formation was completely prevented when the cavity wall was primed with 35 vol% glyceryl mono-methacrylate solution after 0.5 mol/L EDTA conditioning. The contraction gap width was significantly decreased when the resin composite was filled into the sclerotic dentin cavity even when priming was omitted. These results suggest that the sclerotic dentin, which is frequently observed in cervical defects, should be preserved as a substrate because it exhibits an effect of dentin priming and is suitable for bonding.

Novel ring transformation of 5-(2,3,5-tri-O-benzoyl-beta-D-ribofuranosyl)-isoxazole-4-carbaldehyde with 1,2-diaminobenzenes to 3-cyano-1,5-benzodiazepine C-nucleosides.

Syntheses of 3-cyano-7- and 8-substituted-4-(beta-D-ribofuranosyl)-1H-1,5-benzodiazepines were reported. Treatment of isoxazole carbaldehyde with 1,2-diamino-4-nitrobenzene in chloroform gave a Schiffs base, 4-(2-amino-5-nitrophenyl)iminomethyl-5-(2,3,5-tri-O-benzoyl-beta-D-ribofuranosyl)isoxazole in 82% yield with no trace of the other regioisomer. The cyclocondensation of the resulting Schiffs base in benzene containing trifluoroacetic acid (TFA) gave 3-cyano-8-nitro-4-(2,3,5-tri-O-benzoyl-beta-D-ribofuranosyl)-1H-1,5-benzodiazepine in 49% yield. The same reaction of isoxazole carbaldeyde with 1,2-diamino-4-methoxy- and 4-chlorobenzenes afforded the corresponding Schiffs bases. Extending the reaction time for Schiffs base gave the corresponding cyanobenzodiazepines in good yields. Debenzoylation of the compounds with sodium methoxide produced deprotected C-nucleosides.

Detection of bisphenol-A in dental materials by gas chromatography-mass spectrometry.

The xenoestrogenic substance bisphenol-A is widely used as a synthetic precursor of resin monomers, such as bisphenol-A diglycidyl methacrylate. Reports describing the release of bisphenol-A from polymerized resin into saliva have aroused considerable concern regarding exposure to xenoestrogen by dental treatment. The purpose of the present study was to demonstrate a reliable methodology of detecting the trace amounts of bisphenol-A in dental materials. Bisphenol-A was separable from bisphenol-A diglycidyl methacrylate, which is often employed as the principal dimethacrylate monomer, by selective extraction with a Sep-Pak C18 cartridge. Using this extraction method in combination with a gas-chromatography mass-spectrometry, we have obtained evidence that all unpolymerized materials used in this study were contaminated with bisphenol-A. Quantitative analysis using a deuterium-labeled compound as an internal standard revealed bisphenol-A contents in commercial dental materials ranging from < 1 microgram/g material to about 20 micrograms/g material. The polymerized dental materials released up to 91.4 ng bisphenol-A/g material into phosphate buffered saline during 24-h incubation. These results indicate that bisphenol-A can be released from dental materials, however the leachable amount would be less than 1/1000 of the reported dose (2 micrograms/kg body weight/day) required for xenoestrogenisity in vivo.

A study on the adsorption structure of an adhesive monomer for precious metals by surface-enhanced Raman scattering spectroscopy.

In order to clarify the role of a primer on the adhesion between dental precious metals and resin, surface-enhanced Raman scattering (SERS) technique has been applied to the structural analysis of the adhesive monomer, 6-(N-(4-vinylbenzyl)propylamino)-1,3,5-triazine-2, 4-dithione (VBATDT) adsorbed on colloidal Au surfaces. VBATDT is one of the major components of commercial primers. A mixture of a methanol solution of VBATDT and aqueous Au colloid was illuminated by the 647.1 nm line from a Kr ion laser to obtain the SERS. The most intense peak at 458 cm-1 due to C = S stretching in the Raman spectrum of solid VBATDT disappears completely in the SERS, while all the other peaks due to vinylbenzyl group vibrations remain unchanged. It suggests that some structural change occurs in VBATDT upon adsorption on Au which involves the C = S bonds and that the molecule undergoes thione-thiol-type tautomerization in the adsorption process. The SERS spectrum of a commercial primer containing VBATDT exhibits a similar spectral pattern. The present results lead us to conclude that some specific interactions exist between the sulfur atoms of VBATDT and Au surface to form chemical bond likes, which are effective to improve the bond strength between dental precious metals and resin. The ambivalent properties of the primer, chemical stability in storage and chemical affinity to Au, are also explained by the thione-thiol-type tautomerization of VBATDT on the basis of the spectroscopic evidence.

Effect of mechanical properties of resin composites on the efficacy of the dentin bonding system.

This study determined the relationship between marginal adaptation to dentin cavity preparations, tensile bond strength of the restorations, and mechanical properties of the composites. Contraction gaps, tensile bond strengths, flexural strengths, and Young's modulus of eight commercial resin composites were determined. Eight resin composites (Clearfil AP-X, Estelite, Estio LC, Litefil II-A, Prodigy, Progress, Silux Plus, and Z-100) were applied to dentin cavities or flat dentin surfaces mediated with an experimental dentin bonding system consisting of 0.5 M EDTA dentin conditioner, priming with 35% glyceryl mono-methacrylate solution, and a commercial dentin bonding agent application (Clearfil Photo Bond). The contraction gap of the resin composite in a cylindrical dentin cavity was prevented completely for three of the resin composites tested (Clearfil AP-X, Estelite, and Silux Plus). The measured tensile bond strength correlated significantly not only with the tensile strength (r2 = 0.506; 0.01 < P < 0.05), but also with the flexural strength (r2 = 0.871; P < 0.001) and Young's modulus (r2 = 0.712; 0.001 < P < 0.01) of the composites, whereas the contraction gap did not correlate significantly with the measured tensile bond strength, the tensile strength, the flexural strength, or Young's modulus (P > 0.05). However, the results did indicate that the higher tensile bond strengths measured in the traditional test may be related to the higher mechanical properties of the resin composites because of the number of specimens that exhibited cohesive failure.

Effect of cavosurface angle on dentin cavity adaptation of resin composites.

The effect of the cavosurface angle of dentin cavities prepared in extracted human molars on the cavity adaptation of a resin composite was evaluated by measuring the gap width between the resin composite and the dentin cavity wall. Cavities with cavosurface angles of 90 degrees, 120 degrees, 135 degrees, or 150 degrees were pretreated with one of two commercial dentin bonding systems or an experimental dentin bonding system. The contraction gap width was measured at both the cavity margin and the section cavity using a light microscope. Complete cavity adaptation was obtained with pretreatment of the experimental groups regardless of the cavosurface angle. The contraction gap observed at the cavity margin was prevented with the two commercial dentin bonding systems when the cavosurface angle was increased to 150 degrees. A high correlation was observed between the contraction gap width and the proportion of the free surface to the adhesive surface of the resin composite restoration.

Effect of functional monomer in commercial dentin bonding agents use of an experimental dentin bonding system.

The objective of the present study was to understand the role of the functional monomers in dentin bonding agents of an experimental dentin bonding system by measuring the wall-to-wall contraction gap and tensile bond strength measurement. The efficacy of three commercial dentin bonding agents after using EDTA for conditioning and GM for priming was evaluated by measuring the contraction gap of the resin composite in a cylindrical dentin cavity, and by measuring the tensile bond strength of the composite to a flat dentin surface. The effect of the functional monomers was demonstrated by the contraction gap measurement alone. The value of the contraction gap was significantly different between the commercial dentin bonding agents and these agents without functional monomers (p < 0.05). It was concluded that the functional monomers were essential to obtaining the marginal integrity of the resin composite in the dentin cavities.

Effectiveness of simplified dentin bonding systems.

The effectiveness of newly developed commercial dentin bonding systems (SB, MB II and KB) was evaluated by measuring the contraction gap width of a resin composite restored into a cylindrical dentin cavity prepared in an extracted human molar and by measuring the tensile bond strength to the flat dentin surface. In addition, calcium loss during dentin conditioning was analyzed using electron microanalyses. An experimental dentin bonding system composed of EDTA conditioning, GM solution priming and a bonding agent containing 10-MDP was employed as a control in which it was presumed that contraction gap formation was prevented completely. However, gap formation was observed using the three commercial simplified dentin bonding systems. SEM observation showed that the gap was formed between the resin composite and the top surface of the dentin cavity wall indicating that the fracture occurred at the adhesive interface, but never inside the dentin nor inside the resin composite.

Effect of 10% phosphoric acid conditioning on the efficacy of a dentin bonding system.

The efficacy of a commercial total-etch wet-bonding dentin bonding system and the effect of conditioning using 10% phosphoric acid both on the Ca-content in the substrate dentin and on the efficacy of the experimental contraction gap-free dentin bonding system were evaluated by measuring the wall-to-wall polymerization contraction gap width of a commercial light-activated resin composite filled into a cylindrical cavity prepared in extracted human dentin. The Ca-content in the dentin was measured with an EDS. Complete marginal adaptation was obtained only in the experimental contraction gap-free dentin bonding system group. The Ca-content in the dentin was rapidly reduced by the 10% phosphoric acid conditioning. It was concluded that the dentist should not decalcify the dentin cavity wall possibly by using a dentin conditioner such as 10% phosphoric acid because the resin composite paste is apt to separate easily from the decalcified dentin cavity wall during polymerization.

2-HEMA-free dentin bonding system to prevent contraction gap.

The effects of 2-hydroxyethyl methacrylate (2-HEMA) both in the primer and in the commercial dentin bonding agent on the efficacy of the dentin bonding system was evaluated by measuring the polymerization contraction gap width of a commercial resin composite restored in a cylindrical dentin cavity prepared in an extracted human molar. Contraction gap formation was prevented in the group of the EDTA-conditioning followed by glyceryl mono-methacrylate, ethylene glycol and 1,6-hexanediol priming regardless of the 2-HEMA content in the dentin bonding agent containing 10-methacryloxydecyl dihydrogen phosphate. However, gap formation could not be prevented completely by the 2-HEMA priming. Therefore, it was possible to conclude that 2-HEMA was neither essential in the primer nor in the dentin bonding agent because of its low bonding efficacy and the resulting side effects on skin tissue as a delayed allergic reaction.

The adverse effect of commercial dentine-bonding systems on the skin of guinea pigs.

It was widely known that 2-hydroxyethyl methacrylate (2-HEMA) can cause contact dermatitis. Commercially available dentine primers and dentine bonding agents that contain 2-HEMA are widely used. The purpose of this study was to investigate the cumulative irritation and delayed hypersensitivity caused by commercial dentine bonding systems when applied to the skin of guinea pigs. We have concluded that almost no dentine bonding systems cause cumulative irritation, but some commercially available dentine bonding systems may produce delayed hypersensitivity.

Bonding efficacy and interfacial microstructure between resin and dentine primed with glyceryl methacrylate.

OBJECTIVES: To evaluate the effect of two experimental primers based on glyceryl methacrylate (GM, 2,3-dihydroxypropyl methacrylate) and 2-hydroxyethyl methacrylate (2-HEMA) on the marginal adaptation of light-cured composite placed into cylindrical dentine cavities and to study the interfacial microstructure. METHODS: The bonding efficacy of two experimental dentine primers combined with a dentine cleanser composed of either 0.5 mol l-1 EDTA neutralized to pH 7.4 by sodium hydroxide or 10% citric acid containing 3% ferric chloride (10-3 solution), and a commercial dentine bonding agent containing phosphate ester, were examined by measuring the wall-to-wall polymerization contraction gap of a commercial light-activated resin composite placed into cylindrical dentine cavities. The adhesive interface between the dentine and the dentine adhesive was observed using a transmission electron microscope (TEM). RESULTS: The formation of a contraction gap was completely prevented by priming with GM, regardless of the dentine cleanser used. However, in groups primed with 2-HEMA, gap formation was observed in three and four specimens out of 10 in the groups that were cleaned with the EDTA and 10-3 solution, respectively. In samples primed with GM, a high-density layer was observed by TEM at the superficial dentine in the hybrid layer, which may have indicated a high monomer content, whereas no density variations were observed in the hybrid layer in samples primed with 2-HEMA.

Cavity adaptation of resin composite in canine cavity in vivo.

The efficacy of four commercial and two experimental dentin bonding systems was examined by observing the cavity adaptation of commercial light-cured resin composites restored in the dogs scheduled to be sacrificed after a medical experiment. Before being sacrificed, a cylindrical class V cavity was prepared in each canine, and the cavity wall was treated with one of four commercial dentin bonding systems according to the manufacturers instructions followed by resin composite filling. The maximum contraction gap widths at the occlusal, gingival and axial cavity wall were measured on the cavity section 30 min after the polymerization of the resin composite under a light microscope. Contraction gap formation was completely prevented in only one of the experimental groups in which the cavity wall was primed with 35 vol% glyceryl mono-methacrylate (GM). In addition, observation of cavity adaptation in the canine in vivo was useful to estimate consistently the efficacy of the bonding systems.

Marginal adaptation of commercial compomers in dentin cavity.

The dentin cavity adaptation and setting characteristics of four commercial compomers were evaluated by measuring the wall-to-wall contraction gap width in the cylindrical dentin cavity and measuring the compressive strength for a maximum of 14 days after setting. The dentin cavity wall was pretreated by the dentin adhesives according to each manufacturer's instructions or the experimental contraction gap-free dentin bonding system. Complete marginal integrity was obtained in only one compomer and two resin composites which were combined with the experimental dentin bonding system. The compressive strength of two resin composites and two compomers ten minutes after setting was comparable to that after 14 days which indicated that the compomers exhibited setting characteristics as rapidly as the resin composite. It was concluded that a high efficacy dentin bonding system is required for commercial compomers to prevent gap formation during irradiation caused by the rapid setting shrinkage.