| With the enhance of health and esthetic pursuits from patients, resin composites are widely used in oral clinic, like in the cases of restoring of dental defect, fixation of loosened teeth, bonding between orthodontic attachments and teeth, and treatment of fracture of alveolar bone and jaw. The performance of compound resin has been obviously improved, which has a lot to do with the development in the adhesive systems. With the improvement of dental bonding materials, from inorganic materials to organic macromolecule materials, they are used to bond enamel, dentine, even soft tissue. Bonding restorations have a number of advantages over traditional, non-adhesive methods. The adhesive techniques can reduce the microleakage at the restorative material-tooth interface, decrease the postoperative sensitivity and recurrent caries. Resulting functional stress, which occurs in both tooth structure and restorative materials, can be more widely distributed. The weakened tooth structure can be protected and reinforced. Adhesive restorative techniques have also expanded the range of indications for esthetic restorative dentistry, allowing deteriorated or debonded restorations to be repaired or replaced with minimal loss of tooth structure. The occurrence of "etching technique" discovered by Buonocore in 1960s and the appearance of resin composites, dental bonding materials and the related techniques have given rise to many new concepts and theories. But there is little of contrastive study on the performances and restorative effects of different adhesives. In this study, several adhesives were used to estimate the cell cytotoxicity on mouse fibroblasts, observe the pulp response, and to examine the postoperative sensitivity of cariesof human teeth. It was hoped to pave a way for the correct use of adhesives and to get better restorative effects of resins.1. Study on the cytotoxicity of adhesives (Durafill, Prime & Bond NT, Clearfil SE Bond) on mouse fibroblasts cultured in vitro.Adhesives and corresponding filling resin were made into modules, which were dipped in RPMI1640 medium. Then the RPMI1640 medium were diluted to the concentration of 100%, 75%, 50%, 25% respectively. The mouse fibroblasts cultured in vitro in different cell-densities were inoculated. After 24 hours of culture, the impregnant of adhesives replaced the culturing liquid. MTT staining and spectrophotometric assay were used to determine the optical density (i.e. OD) and calculate the mean. Results: When the fibroblasts were cultured for 2,4 and 7 days, OD of the three adhesives were found to be different (P<0.05), with OD of Clearfil SE Bond being higher than the other two. OD of the three adhesives increased gradually with time. In the culture condition of four kinds of concentrations, OD of the three bonding agents were also different (P<0.05) , with OD of Clearfil SE Bond being higher than the other two. OD of the three adhesives decreased gradually as the concentration increased. Result: Cytotoxicity of the three adhesives was weak, and cytotoxicity increased with the culture time and concentration enhancement. Among the three adhesives, the cytotoxicity of Clearfil SE Bond was the least.2. Study on the effect of indirect capping pulp with adhesives systems (Prime & Bond NT, Clearfil SE Bond).Deep Class V cavities, close to the pulp cavity but not pulp-penetrating, were prepared on the buccal surface of 88 dens caninus, molars and premolars of dogs. The thickness of the remained dentine of the specimens was 553.6um. Specimens were treated respectively with Clearfil SE Bond and Prime & Bond NT cured instantly and after 20 minutes, and were then restored with resin composite Clearfil AP-X. The samples of the control group were restored with Clearfil AP-X after pulp capping with Timelime. The dogs were killed 30 or 90 days later and the teeth were extracted. After fixation, demineralization and paraffin embedding, serial sections were obtained and they were stained with H/E, Mallory s technique and Glam, ready for the observation of... |
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