PubMed · 5760329
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C Parrini. 1968. [On dentin sensitivity].. https://pubmed.ncbi.nlm.nih.gov/5760329/
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OBJECTIVES: Development of an adequate interfacial seal is fundamental to achieving a good dentine bond. This study investigates the influence of the properties and application of primers and resin adhesives on dentine interfacial morphology and micropermeability, using a fluorescence confocal microscopy technique. METHODS: Three commercially available (Optibond, Clearfil Liner Bond 2, Pertac Universal Bond) and four experimental dentine bonding systems based on the total each technique were used in the study. Approximal cavities were prepared in third molar teeth and restored using the dentine bonding system (DBS) and resin composite. In the interfacial morphology study the primer and adhesive bonding system were labelled with fluorescent dyes, while in the micropermeability study the pulp chambers were filled with fluorescent labelled saline for 3 h. Ten teeth were prepared in each study for each dentine bonding system. Teeth were sectioned longitudinally and viewed with a tandem or laser scanning confocal microscope. Interfacial micropermeability from the pulpal wall was measured using image analysis techniques. RESULTS: All primers and adhesives showed good penetration of the prepared dentine, except Pertac Universal Bond which manifested 100% micropermeability. The lowest micropermeability results were obtained with Clearfil Liner Bond 2, Optibond and a total etch experimental system where the primer was applied with agitation and contained no photo-initiators and the adhesive resin was unfilled. The latter, when used with a photosensitive version of the same primer, demonstrated a detrimental effect on micropermeability. Light activation of primers in the experimental systems coincided with very variable patterns of leakage. CONCLUSIONS: This high resolution confocal fluorescence technique enabled both the degree and site of micropermeability within the interfaces to be recorded. Matching of primers and adhesives in DBS is important to minimize micropermeability. The non-polymerized primer system probably retained some elasticity in the hybrid zone and so gave less leakage than experimental primers with photo-initiators.
The purpose of this study was to determine whether a nanosecond-pulsed, frequency-doubled Nd:YAG laser emitting at 532 nm can be used as an alternative to mechanical methods of root canal treatment or as an adjunct to conventional endodontic preparation. Laser parameters whose thermal effects did not exceed safety thresholds for adjacent periodontal tissues were selected in a preliminary study. In 27 extracted human teeth, root canals were irradiated for 30 to 60 s at fluences of 2 to 2.2 J/cm2, and 10 Hz. Samples were observed using SEM. Laser irradiation could achieve smear layer removal after minimal manual preparation. However, results were inhomogeneous, and at higher energy densities thermal damage was observed, especially in the fully manually prepared samples. Nanosecond-pulsed irradiation at 532 nm can achieve complete smear layer removal. However, mechanisms must be developed to monitor laser effects and avoid potential damage to collateral structures.
BACKGROUND AND OBJECTIVE: The use of excimer lasers for treatment of dental hard tissues has considerable potential because the combined characteristics of low wavelength and short pulse result in limited heat diffusion and, therefore, tissue ablation without the problems of collateral damage. To date, there are relatively few published studies concerning the effects of excimer laser irradiation on dental hard tissues. Thus the present study was conducted to examine the morphological changes in tooth dentin subsequent to ArF excimer laser irradiation. STUDY DESIGN/MATERIALS AND METHODS: The morphologic changes induced in normal, nondiseased human dentin following irradiation by an ArF excimer laser at fluences ranging from 1 to 4 J/cm2 and the number of laser pulses ranging from 50 to 1,000 were evaluated by scanning electron microscopy. RESULTS: Two modes of ablation, photochemical at low fluences and thermal at high fluences, were observed. A fluence of 1 J/ cm2 when combined with 50 or 100 pulses produced a uniform ablation of the dentin surface without signs of tissue melting. At fluences > 1.5 J/cm2, the thermal mode of ablation was more efficient at removing intertubular dentin than peritubular dentin. Further, when compared to the lower fluences, the higher settings produced a rougher ablation crater surface. Additionally, the higher fluences produced surface melting with each pulse and sealing of exposed dentinal tubules after irradiation with 100-300 laser pulses. CONCLUSIONS: The photochemical and thermal mechanisms of tooth dentin ablation were identified based on significant differences in tissue morphology following laser irradiation. The rates of tissue ablation and the observed morphologic changes indicate that the ArF excimer laser could be useful for caries removal and sealing of exposed dentinal tubules.