PubMed · 829693
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P Delevanes. [The traumatized tooth].. https://pubmed.ncbi.nlm.nih.gov/829693/
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Dentin proteoglycans are fundamental constituents of the dentin matrix and are distributed ubiquitously both in dentin and cement. They have several important functional properties; in particular, they have a fundamental role in the maintenance and the correct stabilization of collagen fibers. The use of phosphoric acid on dentin, as proposed in most common dental adhesive systems to establish a reliable bond, may affect the molecular structure of proteoglycans. The aim of this study was to evaluate, after the application of EDTA or phosphoric acid on dentin, the dentin proteoglycans with an immunocytochemical approach with high resolution SEM. For this purpose, dentin disks obtained from recently extracted human molars were etched with a 35% water solution of phosphoric acid for 15 s, 30 s, and 60 s. Control specimens were conditioned with EDTA. Specimens were immunolabeled with a monoclonal antibody antichondroitin sulfate and visualized with a gold-conjugated secondary antibody. Conditioning dentin with EDTA resulted in a distinct labeling of the proteoglycans, as visualized on branching fibrillar structures in the order of 10-20 nm. The use of 35% phosphoric acid on dentin revealed a coagulation of proteoglycans after etching for 15 s while a very low labeling signal was detectable after 30 s. No labeling was obtained after etching dentin with phosphoric acid for 60 s. These results suggest that the use of 35% phosphoric acid on dentin is able to produce significant structural modifications of the dentin proteoglycans even after short application times. Additionally, when applied on the dentin surface for more than 30 s, phosphoric acid produces a dramatic decrease in proteoglycans' antigenicity, probably due to structural modifications of the three-dimensional conformation of these molecules.
Dentin permeability was measured alternatively with two methods: a 10-microl capillary method with visual evaluation (PC) and a motorized automatic measuring device (Flodec, FD), both interposed in a simulated perfusion system. Eight human third molar coronal fragments were connected to systems, and their permeability to distilled water measured at 0, 5, 10, 15, 20, 25, and 29 cm H(2)O pressure. Resultant permeabilities (in microl/s) for both techniques were interrelated with the use of the Passing and Bablok nonparametric method, which gives information about the range of constant and proportional errors and their 95% confidence intervals (95CI). The relationship between the methods is described by the regression formula: FD = -0.0003 + 0.945.PC, with 95CI for constant (-0.0015-0.0009) and for slope (0.738-1.168), indicating that both methods are interchangeable, although not identical.
The effect of laser parameters on laser-dentine interaction is little known. The aim of this in vitro study was to determine the effect on dentine crater depth of Nd:YAG laser radiation in relation to pulse repetition rate, total delivered energy, dentine site and the presence or absence of a dye. One hundred and forty-four sound third molars were extracted and sectioned transversely to provide 288 upper and lower cut surfaces. The upper surfaces were painted with a layer of dye (IR5) suitable for absorption at 1064 nm. The specimens were divided into 12 sub-groups each containing 12 upper and 12 lower specimens. These were exposed to a Nd:YAG laser with a 30 nanosecond (ns) pulse duration. This laser operated in a non-contact mode (spot diameter 165 microm) with pulse repetition rates of 2.5, 5.4 and 10.5 Hz. Four total energies were delivered at each repetition rate; 2.3, 3.63, 3.96, 4.29 joule (J) at 2.5 Hz repetition rate; 2.3, 2.64, 3.63, 4.29 J at 5.4 and 10.5 Hz repetition rates. Five outer and three inner sites were irradiated on each specimen. Each dentine crater depth was measured five times using a Reflex Microscope and a three-dimensional centre of gravity derived. An upper and lower specimen were taken from each sub-group and viewed under a scanning electron microscope (SEM). ANOVA was applied: total delivered energy and dyed/undyed were found to have a statistically significant effect on crater depth (p<0.0001). In general increasing energy and the presence of dye produced deeper craters. Inner/outer dentine location and repetition rate were not found to be statistically significant. All craters were carbonised.