Correlation of dental health behavior with health awareness and subjective symptoms in a rural population in Japan.

The aim of this study was to determine the association of dental health behavior with health awareness, oral condition, and subjective symptoms in Japan. The present study included 1699 individuals who underwent dental checkups at the public health center of Miura City. All those who underwent dental checkups were asked to fill out a questionnaire. The correlation between having a regular dentist and each of the other items was analyzed. Undergoing regular checkups was significantly related to having a regular dentist. To analyze the correlation of dental health behavior with Subjective symptoms and Health awareness, structured equation modeling was performed following factor analysis. As a result, only the regression weight between dental health behavior and health awareness was found to be statistically significant. The present survey indicates that dental health behavior was significantly related to Health awareness but not to Subjective symptoms.

Comparative inhibitory effects of magnolol, honokiol, eugenol and bis-eugenol on cyclooxygenase-2 expression and nuclear factor-kappa B activation in RAW264.7 macrophage-like cells stimulated with fimbriae of Porphyromonas gingivalis.

BACKGROUND: The anti-inflammatory activity of magnolol and related compounds is currently a focus of interest. In the present study, the inhibitory effects of these compounds on cyclooxygenase (COX-2) expression and nuclear factor-kappa B (NF-κB) activation were investigated in RAW264.7 macrophage-like cells stimulated with the fimbriae of Porphyromonas gingivalis, an oral anaerobe. MATERIALS AND METHODS: The cytotoxicity of magnolol, honokiol, eugenol and bis-eugenol against RAW264.7 cells was determined using a cell counting kit (CCK-8). The regulatory effect of these compounds on the expression of COX-2 mRNA, stimulated by exposure to the fimbriae was investigated by real-time polymerase chain reaction (PCR). NF-κB activation was evaluated by enzyme-linked immunosorbent assay (ELISA)-like microwell colorimetric transcription factor activity assay (Trans-AM) and western blot analysis. The radical-scavenging activity was determined using the induction period method in the methyl methacrylate-azobisisobutyronitrile (AIBN) polymerization system under nearly anaerobic conditions. The phenolic bond dissociation enthalpy (BDE) and orbital energy were calculated at the density functional theory (DFT) B3LYP/6-31G* level. RESULTS: The cytotoxicity against RAW264.7 cells declined in the order bis-eugenol>eugenol> honokiol>magnolol, whereas the radical-scavenging activity declined in the order honokiol, bis-eugenol>magnolol> eugenol. Magnolol and honokiol significantly inhibited the fimbria-induced expression of COX-2 at non-cytotoxic concentrations. Both the fimbria-stimulated binding of NF-κB to its consensus sequence and phosphorylation-dependent proteolysis of inhibitor κB-α were markedly inhibited by magnilol and honokiol, whereas eugenol and bis-eugenol did not inhibit COX-2 expression and NF-κB activation. Magnolol and honokiol possessed a high electronegativity (χ) value. CONCLUSION: Magnolol and honokiol exhibit antioxidative activity, low cytotoxicity, and anti-inflammatory activity. These compounds may be capable of preventing chronic inflammatory diseases induced by oral bacteria.

Relationships between base-catalyzed hydrolysis rates or glutathione reactivity for acrylates and methacrylates and their NMR spectra or heat of formation.

The NMR chemical shift, i.e., the π-electron density of the double bond, of acrylates and methacrylates is related to the reactivity of their monomers. We investigated quantitative structure-property relationships (QSPRs) between the base-catalyzed hydrolysis rate constants (k1) or the rate constant with glutathione (GSH) (log k(GSH)) for acrylates and methacrylates and the (13)C NMR chemical shifts of their α,ß-unsaturated carbonyl groups (δC(α) and δC(ß)) or heat of formation (Hf) calculated by the semi-empirical MO method. Reported data for the independent variables were employed. A significant linear relationship between k1 and δC(ß), but not δC(α), was obtained for methacrylates (r(2) = 0.93), but not for acrylates. Also, a significant relationship between k1 and Hf was obtained for both acrylates and methacrylates (r(2) = 0.89). By contrast, log k(GSH) for acrylates and methacrylates was linearly related to their δC(ß) (r(2) = 0.99), but not to Hf. These findings indicate that the (13)C NMR chemical shifts and calculated Hf values for acrylates and methacrylates could be valuable for estimating the hydrolysis rate constants and GSH reactivity of these compounds. Also, these data for monomers may be an important tool for examining mechanisms of reactivity.

Mechanisms of action of (meth)acrylates in hemolytic activity, in vivo toxicity and dipalmitoylphosphatidylcholine (DPPC) liposomes determined using NMR spectroscopy.

We investigated the quantitative structure-activity relationships between hemolytic activity (log 1/H(50)) or in vivo mouse intraperitoneal (ip) LD(50) using reported data for α,ß-unsaturated carbonyl compounds such as (meth)acrylate monomers and their (13)C-NMR ß-carbon chemical shift (δ). The log 1/H(50) value for methacrylates was linearly correlated with the δC(ß) value. That for (meth)acrylates was linearly correlated with log P, an index of lipophilicity. The ipLD(50) for (meth)acrylates was linearly correlated with δC(ß) but not with log P. For (meth)acrylates, the δC(ß) value, which is dependent on the π-electron density on the ß-carbon, was linearly correlated with PM3-based theoretical parameters (chemical hardness, η; electronegativity, χ; electrophilicity, ω), whereas log P was linearly correlated with heat of formation (HF). Also, the interaction between (meth)acrylates and DPPC liposomes in cell membrane molecular models was investigated using (1)H-NMR spectroscopy and differential scanning calorimetry (DSC). The log 1/H(50) value was related to the difference in chemical shift (ΔδHa) (Ha: H (trans) attached to the ß-carbon) between the free monomer and the DPPC liposome-bound monomer. Monomer-induced DSC phase transition properties were related to HF for monomers. NMR chemical shifts may represent a valuable parameter for investigating the biological mechanisms of action of (meth)acrylates.

A review of the developments of multi-purpose primers and adhesives comprising novel dithiooctanoate monomers and phosphonic acid monomers.

This paper reviews the developments of dithiooctanoate monomers and acidic adhesive monomers, and their roles in multi-purpose primers and adhesives in promoting adhesion to multiple substrate materials. Novel dithiooctanoate monomers exhibited excellent bonding to precious metals and alloys when compared against conventional sulfur-containing monomers. Newly developed phosphonic acid monomers, endowed with a water-soluble nature, enabled sufficient demineralization of dental hard tissues and thus improved bonding to both ground enamel and dentin. The optimal combination for bonding to dental hard tissues and precious and non-precious metals and alloys was 5.0 wt% 10-methacryloyloxydecyl 6,8-dithiooctanoate (10-MDDT) and 1.0 wt% 6-methacryloyloxyhexyl phosphonoacetate (6-MHPA). For bonding to dental porcelain, alumina, zirconia, and gold (Au) alloy, a ternary combination of silane coupling agent, acidic adhesive monomers, and dithiooctanoate monomers seemed promising. The latest development was a single-bottle, multi-purpose, self-etching adhesive which contained only acidic adhesive monomers and dithiooctanoate monomers but which produced strong adhesion to ground enamel and dentin, sandblasted zirconia, and Au alloy.

Radical-scavenging activity of dietary phytophenols in combination with co-antioxidants using the induction period method.

The radical-scavenging activity of dietary phytophenols has been investigated by many researches due to their antioxidant, anti-inflammatory and anticancer property but the radical-scavenging effect of 2-phytophenol and the phytophenol:co-antioxidants, vitamin C and thiol combination under nearly anaerobic conditions still remains unknown. The radical-scavenging activity for seventeen phytophenols and for six synthetic phenols (positive controls) was investigated using the induction period method in the polymerization of methyl methacrylates (MMA) initiated by thermal decomposition of benzoyl peroxide (BPO) by monitoring differential scanning calorimetery (DSC). The k(inh) for the phytophenols was likely with the range 0.5 × 10³ M⁻¹s⁻¹-2.2 × 10³ M⁻¹s⁻¹, whereas that for synthetic phenols, hydroquinone and galvinoxyl, was with the range 7 × 10³ M⁻¹s⁻¹-8 × 10³ M⁻¹s⁻¹. Also, the additive scavenging effect of the (-)-epigallocatechin (EGC):(-)-epicatechin (EC) and the (+)-catechin:epicatechin (EC) combination was observed at 1:1 molar ratio, whereas that of the EC:quercetin combination showed the cancel (prooxidative) effect. Furthermore, the EGC:ASDB (L-ascorbyl 2,6-dibutylate) or 2-ME (2-mercaptoethanol) combination showed the prooxidative effect. Such enhancement of prooxidation in the combination may increase their toxic effects due to their cooxidation. Also, the synergic, additive or cancel effects of the flavonoid:vitamins E combination on the induction period in the BPO (a PhCOO* radical) and 2,2'-azobisisobutyronitrile (AIBN, an R* radical) systems are discussed.

A review of the developments of self-etching primers and adhesives -Effects of acidic adhesive monomers and polymerization initiators on bonding to ground, smear layer-covered teeth.

This paper reviews the developments of self-etching primers and adhesives, with a special focus on the effect of acidic adhesive monomers and polymerization initiators on bonding to ground, smear layer-covered teeth. Ionized acidic adhesive monomers chemically interact with tooth substrates and facilitate good bonding to ground dentin. Polymerization initiators in self-etching primers further promote effective bonding to ground dentin. To promote bonding to both dentin and enamel, phosphonic acid monomers such as 6-methacryloyloxyhexyl phosphonoacetate (6-MHPA) were developed. These novel adhesive monomers also have a water-soluble nature and are hence endowed with sufficient demineralization capability. A new single-bottle, self-etching, 2-hydroxyethyl methacrylate (HEMA)-free adhesive comprising 6-MHPA and 4-acryloyloxyethoxycarbonylphthalic acid (4-AET) was developed. This novel adhesive enabled strong adhesion to both ground enamel and dentin, but its formulation stability was influenced by pH value of the adhesive. To develop hydrolytically stable, single-bottle, self-etching adhesives, hydrolytically stable, radical-polymerizable acidic monomers with amide or ether linkages have been developed.

Synthesis of novel acryloyloxyalkyl and methacryloyloxyalkyl 6,8-dithiooctanoates and evaluation of their bonding performances to precious metals and alloys.

This study investigated the bonding effectiveness of novel acryloyloxyalkyl and methacryloyloxyalkyl 6,8-dithiooctanoates (dithiooctanoate monomers) to precious metals and alloys. Eight kinds of dithiooctanoate monomers were synthesized in 16.09-39.34% yields. They were characterized and confirmed as new compounds using (1)H- and (13)C-NMR spectroscopy and mass spectral analysis. Eight experimental primers each containing 5.0 wt% of a novel dithiooctanoate monomer in acetone were prepared. After primer treatment and 2,000 thermal cycles, tensile bond strengths of MMA-PMMA/TBBO resin to seven metal adherends were measured. Results were as follows: 17.2-29.3 MPa (Au), 41.9-49.6 MPa (Ag), 36.8-47.6 MPa (Pt), 36.7-47.5 MPa (Pd), 34.0-48.9 MPa (Au alloy), 24.3-49.6 MPa (Ag alloy), 35.0-48.8 MPa (Au-Ag-Pd alloy). 10-Methacryloyloxydecyl 6,8-dithiooctanoate exhibited the highest mean bond strength to gold (29.3 MPa) and 12-methacryloyloxydodecyl 6,8-dithiooctanoate to Au alloy (48.9 MPa). Therefore, it was found that the novel dithiooctanoate monomers synthesized in this study exhibited excellent bonding to precious metals and alloys.

Effects of a newly designed HEMA-free, multi-purpose, single-bottle, self-etching adhesive on bonding to dental hard tissues, zirconia-based ceramics, and gold alloy.

This study investigated the bonding effectiveness of newly designed self-etching adhesives to four types of adherends--enamel, dentin, zirconia, and gold (Au) alloy. Five experimental adhesives were prepared, which contained 3.0-5.0 wt% 6-methacryloyloxyhexyl phosphonoacetate (6-MHPA) or 6-methacryloyloxyhexyl 3-phosphonopropionate (6-MHPP), 3.0 wt% 4-acryloyloxyethoxycarbonylphthalic acid (4-AET) or 17.0 wt% 4-methacryloyloxyethoxycarbonylphthalic acid (4-MET), 0-0.5 wt% 6-methacryloyloxyhexyl 6,8-dithiooctanoate (6-MHDT) or 10-methacryloyloxydecyl 6,8-dithiooctanoate (10-MDDT), and varying contents of Bis-GMA, dimethacrylate monomers, water, acetone, and a photoinitiator system. After 2,000 times of thermal cycling, shear bond strengths (SBSs) between a resin composite (Beautifil II, Shofu Inc., Japan) and the four adherends, bonded using the experimental adhesives, were measured at 1.0 mm/min. No statistically significant differences in SBS for bonding to ground enamel, dentin, sandblasted zirconia and Au alloy (p>0.05) were found between experimental adhesives which contained 6-MHPA and/or 6-MHPP, 4-MET or 4-AET, 6-MHDT and/or 10-MDDT, Bis-GMA, and dimethacrylates. An adhesive layer of less than 5.0 µm thickness, by scanning electron microscopy observation, revealed strong adhesion to the four adherends. Therefore, the newly designed multi-purpose, self-etching adhesive strongly adhered to all the four adherend materials tested.

Design of a new, multi-purpose, light-curing adhesive comprising a silane coupling agent, acidic adhesive monomers and dithiooctanoate monomers for bonding to varied metal and dental ceramic materials.

A newly designed, light-curing adhesive was investigated for its bonding effectiveness to porcelain, alumina, zirconia, Au, Au alloy, Ag alloy, Au-Ag-Pd alloy, and Ni-Cr alloy. Four experimental adhesives were prepared using varying contents of the following: a silane coupling agent [3-methacryloyloxypropyltriethoxysilane (3-MPTES)], acidic adhesive monomers [6-methacryloyloxyhexyl phosphonoacetate(6-MHPA),6-methacryloyloxyhexyl3-phosphonopropionate(6-MHPP)and 4-methacryloyloxyethoxycarbonylphthalic acid (4-MET)], and dithiooctanoate monomers [6-methacryloyloxyhexyl 6,8-dithiooctanoate (6-MHDT) and 10-methacryloyloxydecyl 6,8-dithiooctanoate (10-MDDT)]. After all adherend surfaces were sandblasted and applied with an experimental adhesive, shear bond strengths (SBSs) of a light-curing resin composite (Beautifil II, Shofu Inc., Kyoto, Japan) to the adherend materials after 2,000 times of thermal cycling were measured. For the experimental adhesive which contained 3-MPTES (30.0 wt%), 6-MHPA (1.0 wt%), 6-MHPP (1.0 wt%), 4-MET (1.0 wt%), 6-MHDT (0.5 wt%) and 10-MDDT (0.5 wt%), it consistently yielded the highest SBS for all adherend surfaces in the range of 20.8 (4.8)-30.3 (7.9) MPa, with no significant differences among all the adherend materials (p>0.05). Therefore, the newly designed, multi-purpose, light-curing adhesive was able to deliver high SBS to all the adherend materials tested.

Development of a new single-bottle multi-purpose primer for bonding to dental porcelain, alumina, zirconia, and dental gold alloy.

This study investigated the bonding efficacy of a combined primer application which comprised a silane coupling agent, an acidic adhesive monomer, and a dithiooctanoate monomer, as well as the influence of shelf life on bonding. Five experimental primers (coded as Si-P-SS-1 to Si-P-SS-4, and Si-SS as the control) were prepared using 20.0-40.0 wt% 3-methacryloyloxypropyltriethoxysilane (3-MPTES), 0-7.44 wt% 6-methacryloyloxyhexyl phosphonoacetate (6-MHPA), and 0.50 wt% 10-methacryloyloxydecyl 6,8-dithiooctanoate (10-MDDT). After 24-hour storage at 23°C (Initial) and 2-month storage at 50°C (Aged), tensile bond strengths (TBSs) of a resin cement (ResiCem, Shofu Inc., Kyoto, Japan) to primer-treated porcelain, alumina, zirconia, and Au alloy were measured. With the Initial and Aged primers of Si-P-SS-1 to Si-P-SS-3, there were no statistically significant differences in the mean TBSs (MPa) [porcelain: 21.7-29.2; alumina: 21.4-25.3; zirconia: 20.3-24.5; and Au alloy: 23.4-27.6] among these three primers (p>0.05), but they were significantly higher than that of the control primer (p<0.05). The experimental primers Si-P-SS-1 to Si-P-SS-3 demonstrated good potential as multi-purpose primers: they had good shelf lives as single-bottle primer systems and were thus able to exhibit good bond strength to all the adherends tested after 2-month storage under accelerated aging conditions.

Effect of the combination of dithiooctanoate monomers and acidic adhesive monomers on adhesion to precious metals, precious metal alloys and non-precious metal alloys.

This study investigated the effect of the combination of a dithiooctanoate monomer and an acidic adhesive monomer on adhesion to precious metals, precious and non-precious metal alloys. From a selection of four dithiooctanoate monomers and six acidic adhesive monomers, 14 experimental primers containing a combination of 5.0 wt% of a dithiooctanoate monomer and 1.0 wt% of an acidic adhesive monomer in acetone were prepared. Tensile bond strengths (TBSs) of MMA-PMMA/TBBO resin to nine kinds of precious metals, precious metal alloys, and non-precious metal alloys after 2,000 thermal cycles were measured. Results showed that there were no significant differences in TBS among the primers to all the precious and non-precious metal adherends tested (p>0.05). Highest TBS values (46.5-55.8 MPa) for bonding to Au alloy, Au-Ag-Pd alloy, Co-Cr alloy, and Ni-Cr alloy were achieved with the primer which contained 5.0 wt% 10-methacryloyloxydecyl 6,8-dithiooctanoate (10-MDDT) and 1.0 wt% 6-methacryloyloxyhexyl phosphonoacetate (6-MHPA). Therefore, 5.0 wt% 10-MDDT and 1.0 wt% 6-MHPA was determined as the optimal combination for bonding to precious metals, precious and non-precious metal alloys.

Design of a metal primer containing a dithiooctanoate monomer and a phosphonic acid monomer for bonding of prosthetic light-curing resin composite to gold, dental precious and non-precious metal alloys.

The effect of metal primers on adhesion of a resin composite to dental metal alloys was investigated. Experimental primers containing a dithiooctanoate monomer [10-methacryloyloxydecyl 6,8-dithiooctanoate (10-MDDT) or 6-methacryloyloxyhexyl 6,8-dithiooctanoate (6-MHDT)] and a phosphonic acid monomer [6-methacryloyloxyhexyl phosphonoacetate (6-MHPA) or 6-methacryloyloxyhexyl 3-phosphonopropionate (6-MHPP)] were prepared. After treating Au, Au alloy, Ag alloy, Au-Ag-Pd alloy, and Ni-Cr alloy with the experimental primers, their shear bond strengths (SBSs) with a prosthetic light-curing resin composite (Solidex, Shofu Inc., Japan) were measured after 1-day storage followed by 5,000 thermal cycles. The SBSs between Solidex and the primer-treated metals which were incubated in air at 50°C for 2 months were further measured. Results showed that the SBSs [mean (SD)] of all metal adherends treated with primer DT-PA-1 (5.0 wt% 10-MDDT, 1.0 wt% 6-MHPA) ranged between 31.2 (5.2) and 34.5 (5.8) MPa. The SBSs of the primer-treated metals did not degrade after 2-month incubation at 50°C. Therefore, a combined primer application consisting of a dithiooctanoate monomer and a phosphonic acid monomer provided efficacious bonding to Au as well as precious and non-precious metal alloys.

Radical-scavenging activity of melatonin, either alone or in combination with vitamin E, ascorbate or 2-mercaptoethanol as co-antioxidants, using the induction period method.

BACKGROUND: Melatonin shows antioxidant/prooxidant activity but its mechanism of action remains unknown. MATERIALS AND METHODS: The radical-scavenging activity of melatonin and various melatonin/co-antioxidant mixtures in a 1:1 molar ratio was evaluated in terms of the length of the induction period (IP) for polymerization of methyl methacrylate (MMA), initiated by thermal decomposition of 2,2'-azobisisobutyronitrile (AIBN) or by benzoyl peroxide (BPO) under nearly anaerobic conditions, which was monitored by differential scanning calorimetry (DSC). RESULTS: The observed IP (A) for a pinoline, L-ascorbyl 2,6-dibutyrate (ASDB), vitamin E (alpha-, beta-, gamma- or delta-T) or 2-mercaptoethanol (2ME) mixture was compared with the calculated total sum of IP (melatonin+each co-antioxidant) (B). For both the AIBN and BPO systems, the A/B for the melatonin/ASDB, beta-T, gamma-T or delta-T mixture was 0.3-0.7, whereas that for the melatonin/2ME mixture was approximately 1. For the AIBN system, the A/B for the melatonin/alpha-T or pinoline mixture was 0.7-0.8. By contrast, for the BPO system, that for the melatonin/alpha-T or pinoline mixture was approximately 1. CONCLUSION: The prooxidant effect of the melatonin/ascorbate or vitamin E mixtures induced by radical-oxidizing activity may help to explain the anticancer activity of melatonin in biological systems.

Effect of novel dithiooctanoate monomers, in comparison with various sulfur-containing adhesive monomers, on adhesion to precious metals and alloys.

This study investigated the effect of novel dithiooctanoate monomers, in comparison with conventional sulfur-containing monomers, on adhesion to precious metals and alloys. Nine experimental primers containing 5.0 wt% 2-methacryloyloxyethyl 6,8-dithiooctanoate (2-MEDT), 6-methacryloyloxyhexyl 6,8-dithiooctanoate (6-MHDT), 10-methacryloyloxydecyl 6,8-dithiooctanoate (10-MDDT), bis(2-methacryloyloxyethyl) disulfide (BMEDS), bis(5-methacryloyloxypentyl) disulfide (BMPDS), bis(10-methacryloyloxydecyl) disulfide (BMDDS), 6-(4-vinylbenzyl-n-propyl) amino-1,3,5-triazine-2,4-dithione (VBATDT), N-(4-mercaptophenyl)methacrylamide (MPMA), or 4-methacryloyloxyethoxycarbonylphthalic anhydride (4-META; control) were prepared. After primer pretreatment and bonding using modified MMA-PMMA/BPO-DEPT resin, tensile bond strengths to precious metals and alloys after 2,000 thermal cycles were measured. For bonding to Au or Ag, novel 2-MEDT, 6-MHDT, and 10-MDDT exhibited significantly higher tensile bond strengths than conventional BMEDS, BMPDS, BMDDS, VBATDT, MPMA, and 4-META (p<0.05). For bonding to Au alloy, Ag alloy, and Au-Ag-Pd alloy, all the novel dithiooctanoate monomers showed significantly higher tensile bond strengths than conventional BMEDS, BMPDS, VBATDT, MPMA, and 4-META (p<0.05). It was found that novel dithiooctanoate monomers exhibited excellent bonding to precious metals and alloys when compared with conventional sulfur-containing monomers.

Effect of PMMA filler particles addition on the physical properties of resin composite.

The aim of this study was to evaluate the effect of additional polymethyl methacrylate (PMMA) fillers on the physical properties of experimental resin composites. PMMA particles (d=30 µm) were added to an experimental methacrylate-based resin composite in five concentrations of 0, 2.0, 4.8, 9.1, and 23.1 wt%. Properties such as contact angle, water sorption and compressive strength were measured and the fractured specimens were observed with a scanning electron microscope. The results showed that a small amount (2 wt%) of additional PMMA fillers inhibited the crack propagation and enhanced compressive strengths of the resin composites, without a significant change in water contact angle of surface or increased water sorption. However, in higher portions, the mechanical properties were not improved as a debonding at the interface between untreated fillers and the matrix, or failure within the organic filler could reduce the compressive yield strength of the composite.

Kinetic polymerization behavior of fluorinated monomers for dental use.

The kinetic polymerization behavior of 2,2,2-trifluoroethyl methacrylate (TFEMA), 1,1,1,3,3,3-hexafluoroisopropyl methacrylate (HFIPMA), 2,2,2-trifluoroethyl acrylate (TFEA) and 1,1,1,3,3,3-hexafluoroisopropyl acrylate (HFIPA) was determined by isothermal differential scanning calorimetry (DSC) and high-performance liquid chromatography (HPLC) in order to improve the properties of fluorinated powder-liquid adhesive resins. Conversion and heat of polymerization were calculated, and the solubility of the homopolymers in common solvents was examined. Comparison of their polymerization reactivity with that of MMA revealed that the overall rate of polymerization initiated by benzoyl peroxide (BPO) decreased in the order TFEA>MMA>TFEMA>HFIPA>HFIPMA. Based on the retention time of the monomer determined by HPLC, the hydrophobicity of the monomers was found to increase in the order MMA

Radical-scavenging activity and cytotoxicity of p-methoxyphenol and p-cresol dimers.

Compoundswith two phenolic OH groups like curcumin possess efficient antioxidant and anti-inflammatory activity. We synthesized p-cresol dimer (2,2'-dihydroxy-5,5'-dimethylbiphenol, 2a) and p-methoxyphenol dimer (2,2'-dihydroxy-5,5'-dimethoxybiphenol, 2b) by ortho-ortho coupling reactions of the parent monomers, p-cresol (1a) and p-methoxyphenol (1b), respectively. Their antioxidant activity was determined using the induction period method, and their cytotoxicity towards RAW 264.7 cells was also investigated using a cell counting kit. The stoichiometric factors n (number of free radicals trapped by one mole of antioxidant moiety) for 2a and 2b were 3 and 2.8, respectively, being greater than those for 1a and 1b. The ratio of the rate constant of inhibition to that of propagation (k(inh)/k(p)) for 2a and 2b was similar to that for 2-t-butyl-4-methoxyphenol (BHA), a conventional food antioxidant. The 50% inhibitory dose (ID50) declined in the order 1b > 1a >> 2b > 2a > BHA. The cytotoxicity for 2a and 2b was significantly greater than that for the parent monomers (p < 0.001), but smaller than that for BHA (p < 0.01). Compounds 2a and 2b may be useful as food antioxidants.

Prediction of the reduced glutathione (GSH) reactivity of dental methacrylate monomers using NMR spectra - Relationship between toxicity and GSH reactivity.

It has been established that the toxicity of acrylate and methacrylate monomers is driven by their reactivity towards glutathione (GSH). With this relationship, the objective of this study was to predict the GSH reactivity of dental methacrylate monomers, and hence their toxicity, using the (13)C-NMR chemical shifts of beta-carbon (delta(Cbeta)) and the (1)H-NMR shifts of the protons attached to beta-carbon (delta(Ha), delta(Hb)). The different nucleophiles were chosen to compare the different nucleophilic reactions involving acrylate and methacrylate monomers. In conjunction with the use of literature data for monomer/GSH reactivity, significant linear relationships between GSH reactivity (log K) and delta(Cbeta )or delta(Ha )were observed (p<0.001). As for the oral LD(50 )values of some dental dimethacrylates in mice, they were estimated using linear regression curve fitting of GSH reactivity-toxicity response data. Results revealed an acceptable correlation between the oral LD(50 )values of acrylates and methacrylates and GSH reactivity (p<0.05, outlier: HEMA). In conclusion, the present findings suggested that NMR spectra might be useful for predicting the toxicity of dental methacrylates.

Bonding durability against water of a fluorine-containing resin for precious metal alloys.

In order to clarify the effect of fluorination of an adhesive resin on the durability of the resin bond to precious metal alloys, 2,2,2-trifluoroethyl methacrylate (TFEMA)-poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA)/TBBO adhesive resin was prepared. The tensile bond strength of this resin to precious metal alloys treated with 9,10-epithiodecyl methacrylate (EP8MA) generally increased in the order Ag alloy