Proceedings of the Finnish Dental Society. Suomen Hammaslaakariseuran toimituksia最新文献

Nerve growth factor (NGF) is known to have an essential role in prenatal development of spinal and trigeminal primary sensory neurons serving nociceptive functions. Investigation of a possible function of NGF in development of intradental innervation has recently begun with the demonstration by others of NGF mRNA and NGF receptor in the pulp. The pulp is of special interest in this respect because of its late development and unusual properties of its innervation. In the present study, use of a sensitive ELISA for NGF has made it possible to detect and measure NGF antigen in pulps of developing rat molars. Pulps contained relatively high concentrations of NGF before and during the time of innervation development.

The initial vascular reactions during inflammation are vasodilation and increased vessel permeability. Both these basic reactions cause increased pulpal fluid volume. In the dental pulp the inflammatory vascular reactions take place in a rigid enclosed dentin chamber, which to some extent makes the pulp vulnerable. Due to this lack of distensibility any gain in pulpal volume will necessarily increase the pulpal tissue pressure. If the tissue pressure rises to the same level as the blood pressure it will compress the pulpal vessels, thus counteracting a beneficial blood flow increase during inflammation. Using the micropuncture technique and laser Doppler flowmetry we have performed simultaneous measurements of tissue pressure and blood flow in the cat dental pulp during neurogenic inflammation. Sensory nerve stimulation caused a rise both in blood flow and tissue pressure. Our findings thus strongly suggest that the increased pulpal tissue pressure promote fluid absorption back into the blood. If, in theory, plasma proteins and other macromolecules had leaked out during sensory nerve stimulation they must have been successfully removed by lymphatics, unless the tissue pressure would have risen to the same level as the capillary blood pressure causing a fall in PBF. This was not found. On the contrary, increased blood flow was measured, even in experiments lasting for more than 8 hours. It is therefore concluded that the pulp may have a beneficial blood flow increase during inflammation in spite of simultaneously increased tissue pressure.

Arachidonic acid metabolism in normal rat incisor pulp was examined by measuring the conversion activity of exogenously added arachidonic acid in pulpal homogenates. It was demonstrated that the major metabolites were 12-hydroxyeicosatetraenoic acid and prostaglandin (PG) I2. Immunohistochemical studies revealed that PGI2 synthase was distributed in the pulpal blood-vessel cells, fibroblasts and odontoblasts, suggesting that PGI2 may contribute to regulating the function of these cells. When the incisor pulp was experimentally inflamed by applying lipopolysaccharide, arachidonic acid metabolism in the pulp showed overall increase. Change in the pulpal vascular permeability, which was assessed by quantifying the amount of extravasated dye, was almost parallel to the changes in PGE2 and PGI2 production. When production of the PGs was inhibited by indomethacin, the increase of vascular permeability in the inflamed pulp was also suppressed. Topically-applied PGE2 and PGI2 methyl ester abolished the suppression of increase in vascular permeability by indomethacin. These results suggest that PGE2 and PGI2 may be involved in the increase of vascular permeability in the experimental pulp inflammation. We further measured the production of leukotriene (LT) B4 in the inflamed pulp by incubating isolated pulp samples with Ca ionophore A23187, followed by radioimmunoassay. Change in LTB4 production was revealed to be almost parallel to that of neutrophil infiltration. BW755C, an inhibitor of both cyclooxygenase and lipoxygenase, reduced both LTB4 production and neutrophil infiltration. Accordingly, it was suggested that LTB4 may be involved in neutrophil infiltration in the experimental pulp inflammation.

The normal structure and function of the odontoblast cell layer is often perturbed by a variety of pathological processes as well as by the restorative procedures and materials required to treat them. It is well accepted and documented that a number of acute histological changes may take place under these circumstances resulting in the loss of integrity of the odontoblast cell layer. To date, our understanding of the immediate physiological response of the odontoblast to pathological processes or iatrogenic trauma remains limited. This paper reviews: first, the evidence for and against the existence of physiological barrier between the distal segments of odontoblast cell bodies; second, the alteration of this physiological barrier following routine restorative procedures; third, the role junctional complexes may play in this barrier function, and finally, the role that dental innervation, both afferent and efferent, may play in influencing and regulating the response of the dental pulp to external stimuli.

In the young cat, the natural replacement of deciduous teeth with a permanent dentition may be accompanied by extensive peripheral nerve degeneration and reinnervation. Since we have previously reported significant physiological effects of tooth pulp deafferentation on V brainstem neurons, we wished to determine if deafferentation associated with deciduous tooth exfoliation was accompanied by comparable neuroplastic changes in the brainstem of kittens. We have examined the pulpal afferent terminating pattern within the brainstem as well as the electrophysiological properties of V brainstem neurons during this naturally occurring deafferentation phenomenon. The pattern of the HRP-labelled terminals in different parts of V brainstem subnuclei in kittens was similar to that in adult cats. The highest density of labelled terminals was found in the subnucleus oralis. The properties of subnucleus oralis neurons also showed many similarities between kittens at age of 3-4 months old and adult cats, e.g., (1) in the proportions of neurons activated by tactile stimulation of 1-4 teeth (mandibular and maxillary canines and premolars), (2) the ratio of neurons showing fast adapting or slow adapting responses to dental tactile stimulation, (3) the proportions of neurons activated by electrical pulp stimulation of 1-4 teeth, and (4) the minimal latencies of pulp-evoked responses. However, the incidences of pulpal inputs as well as the convergent pattern to oralis neurons of afferent inputs evoked by periodontal stimulation and electrical pulpal stimulation were less common in kittens than adult cats.

Permanent teeth are usually not attacked by osteoclasts despite their situation in a site where active bone resorption constantly takes place as a result of local and systemic osteoclast activating factors. This fact points to antiresorption factors residing in both the periodontal ligament (PDL) and the pulp. Concerning the PDL homeostasis factor (i.e. permanency of a separation between the alveolar socket and the root surface and protection of the root surface against osteoclastic activity), recent studies have shown that this factor, at least with respect to trauma and wound healing, is linked to, and probably resides in, the cementoblast layer and/or the cells next to this layer. If there is loss of this tissue integrity, root resorption may occur; especially if non-PDL derived cells gain access to the site. With respect to the pulp, no systematic research has been performed regarding the homeostasis of this structure (i.e. permanency of the pulpal organ with its specific anatomy and functional stability). In evaluating the events where resorption does occur, it appears that the loss of tissue components within the pulp (including odontoblasts) implies a risk of root canal resorption if nonpulpally derived cells gain access to the site. Root resorption following traumatic dental injuries, whether located along the root surface or within the root canal appears to be a sequel to wound healing events, where a significant amount of the PDL or pulp has been lost due to the effect of acute trauma. The goal of these processes is removal of injured tissue from zones of trauma, space creation for neovascularization or control of infection. Irrespective of the goal, these processes have a potential for root resorption. The type of tissue repair, i.e. repair originating from the dental pulp, the PDL or bone or a combination, seems to be of importance in determining the risk of root resorption during the healing process.

The paper presents an overview of the oral health situation in Denmark with consideration to the effectiveness of dental health care services to children, adolescents, and adults. According to the Act on Dental Health consolidated in 1986, the Municipal Dental Service provides systematic preventive and curative care free of charge to the child population and adolescents. The adults are responsible for a substantial part of the payments at the private dental practitioners but some of the payments, in particular the curative services, are covered by the National Health Insurance Scheme. The Municipal Dental Service is attended by nearly 100%. In order to plan and evaluate the service, a standardized recording system has been established. Thereby, national oral epidemiological data have been provided since 1972. Partly due to the preventive approach, a general decrease over-time in the prevalence of dental caries has been documented for children and adolescents. For example, in 1972 children in first class had a mean caries experience of 12.4 def-s against 3.9 def-s in 1990. Moreover, the distribution of dental caries has become even more skewed which means that an increasing number of the children are free of caries while a limited number of the children still show a significant caries experience. According to interview data from 1987, 72% of the adult population 16 years of age and above reported regular dental visits at least once a year. The proportion of regular dental visitors were high in 16-24-years-old (92%) but lower in the age group 65-74 (35%). In 1982, clinical epidemiological data were collected as part of a national oral health survey. The results indicated that the amount of untreated dental caries and the number of missing teeth were significantly lower among regular dental visitors than irregulars. As to periodontal health, treatment needs were also prominent among regular dental visitors. In a longitudinal survey, over-time changes in the occurrence of denture wearers have been observed. In 1976, 30% of the 35-44-year-olds were denture wearers against 11% in 1986. One important finding from this survey was that social inequality in oral health seems to be reduced in younger adults. Finally, experiences from implementation of health education and preventive dental care in industrial settings are discussed, and the health outcome of a comprehensive public dental health care programme for old-age pensioners is reviewed.

Although the prevalence of caries has decreased markedly in children, adolescents, and young adults in most industrialized countries, caries continues to be the main reason for tooth loss, particularly among the high risk segment of the population. In many developing countries, where traditional dietary patterns have changed to include sugar-containing foods and beverages, caries prevalence has increased and will continue to do so in the immediate future. Accordingly, it would be a serious mistake to be complacent about caries prevention. In future industrialized countries will see computers playing a significant role in cariology, finding applications not only in research and practice administration but directly in clinical practice as well. They will be used in every operatory in the assessment of caries risk, the recording of caries prevalence, the direct storing of radiographic information, and the restoration of carious teeth, assisted by computer-aided design and computer-aided manufacture (CAD/CAM) technology. Fluoride therapy, both systemic and topical, will continue to be the basis of caries prevention. Dental sealants, which are highly effective in protecting pits and fissures when applied soon after the teeth erupt, will be more widely used in the future when insurance plans will pay for prevention. Substitution of sucrose and syrups by non-fermentable sweetening agents can also reduce caries increments, but most agents are more expensive than sucrose and require consumer education to pay for the additional cost. Caries, as an infectious and transmissible disease, is amenable to prevention by interfering with the chain of transmission or by suppressing the putative pathogens, the mutans streptococci, in infected patients.(ABSTRACT TRUNCATED AT 250 WORDS)