Impact of <Emphasis Type="Italic">Streptococcus mutans</Emphasis> on the generation of fluorescence from artificially induced enamel and dentin carious lesions in vitro

The purpose of this study was to examine whether Streptococcus mutans is implicated in the generation of fluorescence detected in carious lesions. Enamel surfaces and dentin cavities of extracted human teeth were subjected to artificial caries generation by exposing them either to a culture medium containing S. mutans or to a lactic acid buffer for 2 weeks. Fluorescence from the lesions was detected with confocal laser scanning microscopy or fluorescence microscopy at various excitation wavelengths, and maximum fluorescence radiance was computed using imageanalyzing software. Culture media of S. mutans were also examined for fluorescence generation. The results demonstrated that S. mutans-induced enamel and dentin lesions exhibited increased fluorescence in the red and green spectral regions, with the signal stronger in the red region. In the blue region, however, fluorescence signals in the corresponding area were below the background level. Significantly weaker or virtually no fluorescence was detected in lactic acid-demineralized lesions at all excitation wavelengths. Neither bacterial cells nor culture media generated any fluorescence. These results indicate that, although the presence of S. mutans may be a prerequisite for the emission of fluorescence from carious lesions, some interaction of S. mutans with exposed tooth matrix elements may also be required for the generation or unmasking of fluorophores.     

Effects of six particulate metals on osteoblast-like MG-63 and HOS cells in vitro

The effects of six particulate metals (Al, Ti, Zr, Nb, Ta and Cr) on cell viability and alkaline phosphatase (ALP) activity were studied in vitro using two types of osteoblast-like cells, MG-63 and HOS cells. The cell viability in the presence of Al, Ti and Zr was depressed at lower concentrations than in the presence of Nb, Ta and Cr. The average sizes of the Al, Ti, Zr, Nb, Ta and Cr particulates were 6.48 microm, 16.99 microm, 5.07 microm, 14.18 microm, 8.32 microm and 23.27 microm respectively. The interaction of HOS cells with the particulates was more sensitive than that of MG-63 cells. ALP activity increased at higher concentrations only with the Al particulates; other experimental conditions did not exert an influence on ALP activity. These findings suggest that the cell viability of osteoblast-like cells might be influenced by particulate size and metal type, but ALP activity was not influenced by these factors.     

Expression of osteoprotegerin in synovial tissue and degradation of articular cartilage: comparison with arthroscopic findings of temporomandibular joint disorders

OBJECTIVE: The aim of this study was to investigate the correlations among the expression of osteoprotegerin (OPG) in synovial tissue and the degree of synovitis, the degeneration of articular cartilage, and the adhesions in patients with internal derangement and osteoarthritis of the temporomandibular joint (TMJ).Study design The expression of OPG, which was detected immunohistochemically, and the degree of arthroscopy of 31 patients with internal derangement and osteoarthritis of the TMJ were assessed and the correlations between them were analyzed statistically. RESULTS: OPG was expressed in the cytoplasm of the endothelial cells, synovial lining cells, and fibroblast cells. TMJs with osteoarthritis had a higher degree of articular cartilage degeneration than did TMJs with internal derangement. There was a correlation between the expression of OPG in the endothelial cells and the degree of the articular cartilage degeneration (P <.01). CONCLUSION: The expression of OPG might be associated with the development of degenerative changes of articular cartilage.     

Effects of TGF-beta on hyaluronan anabolism in fibroblasts derived from the synovial membrane of the rabbit temporomandibular joint

Hyaluronan (HA) synthesis in the synovial membrane is affected by various chemical mediators. It is hypothesized that transforming growth factor-beta 1 (TGF-beta 1) would be a mediator to modulate HA synthesis in cultured synovial membrane fibroblasts of the temporomandibular joint (TMJ). Fibroblasts were extracted from the TMJ synovial membrane of four-week-old Japanese white rabbits. The amount of HA and expression levels of HA synthase (HAS) mRNAs induced by TGF-beta 1 treatment were analyzed by means of high-performance liquid chromatography and real-time polymerase chain-reaction, respectively. Both medium and large amounts of HA were enhanced by the stimulation of TGF-beta 1. HAS2 mRNA expression was enhanced 13-fold after six-hour stimulation with TGF-beta 1 (10 ng/mL), whereas HAS3 mRNA expression was not changed significantly. These results suggest that TGF-beta 1 enhances the expression of HAS2 mRNA in the TMJ synovial membrane fibroblasts and may contribute to the production of high-molecular-weight HA in the joint fluid.     

Longitudinal follow-up of osseointegrated implants in patients with resected jaws

PURPOSE: To investigate the effects of bone grafting and radiotherapy on implant survival rates. MATERIALS AND METHODS: This follow-up study involved 36 patients with 180 implants who were treated between January 1989 and December 2000 by prosthodontic rehabilitation using osseointegrated implants following jaw resection. They comprised 20 patients with malignant tumors, 12 with benign tumors, and 2 patients each with osteomyelitis and cysts. RESULTS: A total of 15 implants (11 in the maxilla and 4 in the mandible) were removed for various reasons during the follow-up study. Implant survival rates were calculated using the Kaplan-Meier method; the overall survival rate for the 180 implants was 88.6%. Specific implant survival rates were as follows: in residual bone, 73.8% for the maxilla and 95.2% for the mandible; in grafted bone, 80% for the maxilla and 94.1% for the mandible; in irradiated bone, 79.7%; and in nonirradiated bone, 93.5%. DISCUSSION: Radiotherapy, a dose of 30 Gy, was performed in patients with malignant tumors but not in patients with benign tumors, cysts, or osteomyelitis. No differences were found in the results for implants placed due to jaw resection for malignant tumors and those for implants placed due to benign tumors, cysts, or osteomyelitis. Implants lost varied in length from 7 to 18 mm. Among these, loss was more frequent with shorter implants (lengths to 10 mm). CONCLUSION: The clinical results obtained in the present study compare favorably with those obtained by others. However, jaw reconstruction and rehabilitation should not be performed by the oral surgeon alone; oral and maxillofacial function should be restored using a team approach in close cooperation with specialists in prosthodontics and periodontics to improve the result of implant treatment.     

Dentin bond durability after three years using a dentin bonding agent with and without priming

Objectives: This three-year study was conducted to evaluate the tensile bond strengths of a dual-cured bonding resin, with and without priming, to bovine dentin.Methods: Superficial bovine dentin was conditioned with 37% phosphoric acid and left unprimed (control) or was primed with 5-NMSA. Clearfil Photobond (Kuraray Co., Japan) was placed and light-cured, a layer of Protect Liner (Kuraray Co.) was applied, cured, then covered with Photo Clearfil Bright (Kurary Co.) resin composite and cured. Bonds were stressed in tension to failure at 1 d, 1 mon, 3 mon, 6 mon, 1 y and 3 y after preparation. Ten specimens were made for each group. Results were analyzed using one-way ANOVA and Duncan's multiple range test. Visual and SEM observations determined mode of failure and were analyzed using the Mann-Whitney U-test. Separate 1 d and 3 y specimens were fractured across the bonded interface and observed using a Field Emission SEM. After observation, the photomicrographs were compared for visual qualitative changes between the two time periods.Results: The control (non-primed) group showed only a small decrease in bond strengths over 3 y, but in the primed group, a significant decrease was observed (p < 0.05). The bond strength of the non-primed group (5.2 MPa) was less than the primed group (10.6 MPa) at 1 d (p < 0.01), but by 3 y, the bonds of both groups were similar, 4.3 MPa and 5.5 MPa, respectively. Fractography indicated that only adhesive failure occurred in the control group. Failure in the primed group was cohesive in dentin initially, but shifted to the base or top of the hybrid layer after 1 y. Field Emission SEM observations showed hybrid layer formation in the primed group, but minimal resin infiltration in the control group.Significance: Initially greater bond strengths were obtained for the primed group compared to the unprimed group (p < 0.01). However, by 3 y, the bond strength had decreased markedly in the primed group (p < 0.01), being almost the same for both groups. It was concluded that priming may only be useful to achieve strong bonding in the short term. These results may have significant implications related to clinical longevity of restorations.     

Multidirectional distraction osteogenesis for Crouzon syndrome: technical note

This report describes multidirectional distraction osteogenesis in a patient with Crouzon syndrome. A RED system and a Hyrax expansion screw were used for lateral expansion of the maxilla. Advancement distraction osteogenesis and a Dyna Form were used for widening distraction osteogenesis of the mandible. The devices were fixed after a quadrangular osteotomy and a bimaxillary midline osteotomy.     

A study of cavity preparation by Er:YAG laser. Effects on the marginal leakage of composite resin restoration

The purpose of this study was to evaluate marginal leakage of composite resin restoration from cavities prepared by Er:YAG laser. The observation of the dentin surface after the application of laser irradiation was performed by LSM, the cutting surface showed a rough surface similar to scales, and exposed dentinal tubules were observed without striations or a smeared layer formation that were observed when using a rotary cutting device. Leakage tests revealed no significant differences in the marginal seal for both enamel and dentin between cavities prepared by Er:YAG laser irradiation and when using an air-turbine. In this study, the usefulness of cavity preparation by Er:YAG laser irradiation in composite resin restoration was suggested.