Clinical longevity of resin-bonded bridges bonded using a vinyl-thiol primer.

The purpose of this study is to clinically confirm the adhesive effect of a vinyl-thiol primer (V-Primer) for precious alloys. Further, we examined the failure of resin-bonded bridges (RBBs) in order to improve the clinical longevity of RBBs, and to analyse the causes of failure. Twenty-six RBBs were bonded with V-primer and Super Bond C & B between May 1987 and December 1997 in the Dental Clinic of the Health Sciences University of Hokkaido. The RBBs were made of silver-palladium-gold alloy or metal-ceramic gold alloys. V-primer was effective in bonding Super Bond C & B to the RBBs made of silver-palladium-gold alloys. Ten prostheses had functioned satisfactorily for 8-11 years. However, six of the 26 RBBs had become detached. In four of the six failed RBBs, the type of bond failure was a mixture fracture in the resin-enamel interface. Our results suggest that: (1) V-primer is effective on RBBs made of silver-palladium-gold alloys. (2) Mechanical retention is necessary for retainers to improve the longevity of RBBs when the V-primer is applied to RBBs made of precious alloys without copper. (3) The RBB should not be applied to abutment teeth that have differences in tooth mobility.

Cytotoxicity of bisphenol A glycidyl methacrylate on cytochrome P450-producing cells.

Of the cytochrome P450 (CYP) family of carcinogen-activating enzymes, CYP3A is the major form found in human livers. The purpose of this study was to investigate the cytotoxic effects of dental resin monomers after being metabolized by CYP3A4 and CYP3A7, using a colony formation assay and a neutral red assay. Specimen wells were plated with transfected cells derived from the Chinese hamster lung at 100 cells well(-1). The experimental group consisted of CYP-producing 3A4-10 and 3A7-40 cells, while the control group consisted of non-CYP-producing CR-119 cells. Bisphenol A (BPA) and bisphenol A glycidyl methacrylate (Bis-GMA) and a positive control (Aflatoxine Bl) were added separately to each well and cultured for 7 days. After cultivation, the number of the colonies was counted and IC50 values were determined. The data were statistically analysed by a Student's t-test. The resultant of IC50 values indicated that the monomers were not metabolically activated by CYP3A4 or CYP3A7 as compared with the control (P < 0.05). We also confirmed that these monomers act neither as activators nor as inhibitors of CYP3A4 and CYP3A7.

Cytotoxicity of dental resin monomers in the presence of S9 mix enzymes.

The purpose of the this study was to evaluate the cytotoxicity of dental resin monomers in the presence of a rat liver S9 mix containing cytochrome P 450 enzymes. JTC-12 cells derived from a monkey kidney were seeded on a 96-well multi-well-plate at 9 x 10(3) cells per well. After cultivation, the S9 mix was added to the wells as an S9 mix group (+S9), and PBS- was added to the other wells as a none-S9 mix group (-S9), then 7 different concentrations of various monomers were added to each well. All the specimens were cultured for another 24 hrs. The cell survival ratios (CSR) were calculated by using a neutral red cytotoxicity assay. CSR for 50 micrograms/mL of Bis-GMA/S9 mix was 92.6% while for none-S9 mix it was 6.6%. The values of CSR for UDMA, Bis-MPEPP, EGDMA, TEGDMA, DMAEM, 4-META and HEMA exhibited a reduction in cytotoxicity in the presence of the S9 mix. There were significant differences between +S9 and -S9 for respective monomers (p < 0.05). However, there were no significant differences between +S9 and -S9 for MMA (p < 0.05).

DNA strand break by 2,5-dimethyl-4-hydroxy-3(2H)-furanone, a fragrant compound in various foodstuffs.

2,5-Dimethyl-4-hydroxy-3(2 H)-furanone (DMHF), produced by Maillard reaction of sugar/amino acid and found in various foodstuffs, showed mutagenicity to Salmonella typhimurium TA100 strain with and without S9 mix, and induced micronucleated mouse peripheral reticulocytes. DNA strand breaking activity of the compound at pH 7.4 increased with the increasing dose of the compound and with the increasing incubation time. The breaking activity was inhibited in the presence of superoxide dismutase, catalase, hydroxyl radical scavengers, spin trapping agents, thiol compounds and metal chelators, and also by removal of dissolved oxygen from the incubation mixture. Addition of Fe(III) ion to the incubation mixture enhanced the breaking activity. Incubation of DMHF with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) gave electron spin resonance signals characteristic to DMPO-OH adduct, indicating generation of hydroxyl radical. It was found that DMHF generated hydroxyl radical with an aid of a trace amount of metal ions, and induced DNA strand breaking. Mutagenicity and induction of micronucleated reticulocytes by DMHF may be caused as a result of DNA modification via hydroxyl radical.

[Toxic activities of the Ga-Sn alloy (Adlloy-OH) on nutritional condition and dental caries development in rats].

The toxic activities of Ga-Sn alloy (Adlloy-OH) in experimental rats, its relations to the nutritional condition and dental caries development, were studied for three months. Adlloy, 0.3 g or 3 g per body weight (kg), was fed orally with the basal diet consisting of casein, sucrose, bean oil, mineral, and vitamin mixtures. Biochemical assays of serum was carried out for total protein, albumin, calcium, inorganic phosphate, glucose, urea, creatine, alkaline phosphatase, GOT, and GPT. There was no convincing evidence of toxic effects on growth and biochemical data by the oral feeding of Addloy-OH.

[A study on adhesive strength of cyanoacrylate dental adhesive, 'F.H. Cement'--thermal-cycled effects].

This study investigated the adhesive strength of cyanoacrylate dental adhesive, 'F.H cement' after being thermal-cycled in order to certify its stability in water. The adhesive strength was compared using Zinc phosphate cement, Glass ionomer cement, Dental adhesive resin and F.H cement when an ivory die and a cast crown were adhered by these different cements. Results of the study indicated the following: 1. The adhesive strength after being thermal-cycled indicated that F.H cement had a greater strength than the other cements (Zinc phosphate cement and Glass ionomer cement) and was equal to that of the Dental adhesive resin. 2. F.H cement was also found to be the strongest in adhesive strength when different tapers were used.

[Biological evaluation of biomaterials using cultured chick embryo femurs (3)].

The biological effects of adhesive resins were studied by an organ culture method using chick embryo femurs, of which usefulness was investigated to evaluate the biocompatibility of biomaterials. Superbond C & B and Panavia EX were processed to form test pieces of 0.35 mm in diameter and 2 mm in length. The test piece was inserted into the distal epiphysis of the femur, which was cultured at 37 degrees C for 7 days. The biomaterials were evaluated by relative growth rate, relative wet/dry weight ratio (W/D) and histological examination. The femurs with insertion of Superbond C & B or Panavia EX did not show growth inhibition, but W/D of Panavia EX was significantly higher than that of control. Histologically, undifferentiated cartilage cells and immature cartilage matrix were observed in the tissue adjacent to Panavia EX. These results suggested that Panavia EX had a slightly toxic effect on the chick embryo femur.

A white band and a transparent zone observed at an interface between a polymerizing polyfunctional monomer and a poly(methyl methacrylate) rod, I.

Macro- and microscopic studies were made of an interfacial microstructure which developed between a bifunctional monomer and a PMMA rod (or beads) during polymerization. The microstructure consisted of a white band and a blue transparent zone.