Application of high resolution microfocus X-ray CT for the observation of human tooth.
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The calcification degree of extracted human teeth was observed by using high resolution microfocus X-ray CT. As samples, upper and lower first premolars extracted from a 21-year-old female were used. The computed tomograms were produced by high resolution microfocus X-ray CT with a open vacuum X-ray source, rotating sample stage, and image sensor. The distinction between enamel and dentin was very clear, and the shape of the pulp cavity was also clearly identified. The secondary dentin was visible in the circumpulpal dentin. The color map displays showed the heterogeneity of the calcification degree not only in the dentin but also in the enamel. The enamel was divided into three layers according to the calcification degree. High resolution microfocus X-ray CT was very useful for the observation of the internal structure of human teeth without destroying the samples. (+info)
Efficacy of dentin bonding to cervical defects.
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The bonding efficacy of sclerotic dentin was determined by measuring the polymerization contraction gap width of a commercial light-activated resin composite in a cervical defect and by measuring the micro-Vicker's hardness at the dentin adhesive surface; morphological characteristics were observed using a scanning electron microscope in extracted human incisors and premolars. Contraction gap formation was completely prevented when the cavity wall was primed with 35 vol% glyceryl mono-methacrylate solution after 0.5 mol/L EDTA conditioning. The contraction gap width was significantly decreased when the resin composite was filled into the sclerotic dentin cavity even when priming was omitted. These results suggest that the sclerotic dentin, which is frequently observed in cervical defects, should be preserved as a substrate because it exhibits an effect of dentin priming and is suitable for bonding. (+info)
Induction and regulation of crown dentinogenesis: embryonic events as a template for dental tissue repair?
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Close regulation of odontoblast differentiation and subsequent secretory activity is critical for dentinogenesis during both embryogenesis and tissue repair. Some dental papilla cells achieve commitment and specific competence, allowing them to respond to epithelially derived inductive signals during the process of odontoblast differentiation. Temporo-spatial regulation of odontoblast differentiation is dependent on matrix-mediated interactions involving the basement membrane (BM). Experimental studies have highlighted the possible roles of growth factors in these processes. Regulation of functional activity of odontoblasts allows for both ordered secretion of the primary dentin matrix and maintenance of vitality and down-regulation of secretory activity throughout secondary dentinogenesis. After injury to the mature tooth, the fate of the odontoblast can vary according to the intensity of the injury. Milder injury can result in up-regulation of functional activity leading to focal secretion of a reactionary dentin matrix, while greater injury can lead to odontoblast cell death. Induction of differentiation of a new generation of odontoblast-like cells can then lead to reparative dentinogenesis. Many similarities exist between development and repair, including matrix-mediation of the cellular processes and the apparent involvement of growth factors as signaling molecules despite the absence of epithelium during repair. While some of the molecular mediators appear to be common to these processes, the close regulation of primary dentinogenesis may be less ordered during tertiary dentinogenic responses. (+info)
Analysis of pulpal reactions to restorative procedures, materials, pulp capping, and future therapies.
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Every year, despite the effectiveness of preventive dentistry and dental health care, 290 million fillings are placed each year in the United States; two-thirds of these involve the replacement of failed restorations. Improvements in the success of restorative treatments may be possible if caries management strategies, selection of restorative materials, and their proper use to avoid post-operative complications were investigated from a biological perspective. Consequently, this review will examine pulp injury and healing reactions to different restorative variables. The application of tissue engineering approaches to restorative dentistry will require the transplantation, replacement, or regeneration of cells, and/or stimulation of mineralized tissue formation. This might solve major dental problems, by remineralizing caries lesions, vaccinating against caries and oral diseases, and restoring injured or replacing lost teeth. However, until these therapies can be introduced clinically, the avoidance of post-operative complications with conventional therapies requires attention to numerous aspects of treatment highlighted in this review. (+info)
Histomorphological response of dogs' dental pulp capped with white mineral trioxide aggregate.
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This study was conducted to observe the response of dogs' dental pulp to white mineral trioxide aggregate (MTA) when used as pulp capping material. The pulp of 15 dogs' teeth was experimentally exposed and capped with white MTA. The animals were sacrificed two months later and the specimens were prepared for histomorphological study. The pulp capped with white MTA showed a healing process with complete dentin bridge formation in all samples. In some cases, there was not a tubular dentin shape, but only a structure with an interesting morphological aspect sealing the exposure site. Only 2 specimens exhibited pulp inflammation. In conclusion, the data obtained in this study showed that white MTA has the necessary properties of a pulp capping material. (+info)
Histological analysis of rat dental pulp tissue capped with propolis.
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The aim of the present study was to assess the response of rat dental pulp to direct pulp capping with propolis. Flavonoid and non-flavonoid materials were purified from an ethanol extract of propolis obtained from South Sulawesi, Indonesia. A Class I cavity was prepared on the occlusal surface of the right maxillary first molar in Sprague Dawley rats. The dental pulp was exposed and then capped with a zinc oxide-based filler as a control (group I), or with propolis flavonoids (group II) or non-flavonoids (group III). The animals were sacrificed at week 1, 2 or 4, biopsy samples were obtained, and these were stained and viewed by light microscopy. The results showed that pulp inflammation occurred in groups I and III as early as week 1. No dentin bridge formation was seen in these groups. In contrast, there was no evident inflammatory response in group II at week 1. Mild and moderate pulp inflammation in this group occurred at 2 and 4 weeks after treatment, respectively. Partial dentinal bridge formation was seen in group II at week 4. Therefore, the present results suggest that direct pulp capping with propolis flavonoids in rats may delay dental pulp inflammation and stimulate reparative dentin. (+info)
Reduced antigenicity of type I collagen and proteoglycans in sclerotic dentin.
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Antigenic alterations to the dentin organic matrix may be detected by an immunohistochemical approach. We hypothesized that alterations in the antigenicity of type I collagen and proteoglycans occur in sclerotic dentin under caries lesions. Transverse sections were prepared from carious teeth in the sclerotic zone and normal hard dentin. A double-immunolabeling technique was performed on these sections, with anti-type I collagen and anti-chondroitin 4/6 sulfate monoclonal primary antibodies. We used gold-conjugated secondary antibodies to visualize the distribution of intact collagen fibrils and proteoglycans by high-resolution SEM. For sclerotic dentin, labeling densities were 19.57 +/- 3.01/microm2 for collagen and 9.84 +/- 2.62/microm2 for proteoglycans. For normal hard dentin, values were 35.20 +/- 2.73/microm2 and 17.03 +/- 1.98/microm2, respectively. Distribution of intact collagen fibrils and proteoglycans in sclerotic dentin was significantly lower than in normal hard dentin. Reductions in antigenicity from the organic matrix of sclerotic dentin under caries lesions raise concern about the potential of intrafibrillar remineralization. (+info)
An in vitro evaluation of pH variations in calcium hydroxide liners.
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The purpose of this present study was to determine the pH changes of five different commercially available calcium hydroxide liners and variations of pH at different time intervals. The following commercially available materials were investigated: Dycal (LD Caulk); Calcimol (Vocco Products); calcium hydroxide powder (Deepti Products); Calcimol LC (Vocco Products); Lime-Lite (Pulpdent Corporation). Five samples were prepared from each liner. The pH measurements were recorded at time intervals of 1 h, 24 h, 3 days and 7 days after mixing of the liner. The pH variations of each material at the given time intervals were recorded and the means were calculated. Comparison of the mean values at all time intervals with the statistical analysis showed significantly high differences (P < 0.001) between pH values induced by each material at all time intervals. Among the water-insoluble products, Dycal had the strongest alkaline effect after 7 days interval. The materials that chemically hardened produced higher pH values than materials that hardened by a visible light source after 7 days. (+info)