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

One of the major events involving inflammatory processes is the alteration of microcirculatory hemodynamics by inflammatory mediators released from tissue components. Using modern macrocirculatory techniques, 15 mu radioisotope labeled microspheres, 133Xe washout, laser Doppler flowmetry and double isotopes, 125 and 131I-albumin, and microcirculatory methods, intravital fluorescence microscopy with FITC labeled dextran, we have examined the effects of selected mediators, e.g. 5-hydroxytryptamine (5-HT), prostaglandin E2 (PG-E2), bradykinin (BK), substance P (SP), calcitonin gene related peptide (CGRP) and histamine on blood flow and vascular permeability in the pulp of experimental animals. Surprisingly, SP and CGRP caused weak albumin leakage in the pulp, while the opposite is true in high compliance tissues, such as muscles, suggesting that the vessels in a low compliance environment, such as the pulp, may not be as permeable in response to selected mediators. Intraarterial injection of 5-HT caused a strong vasoconstriction which was mediated by 5-HT1p receptor subtype. The pulpal 5-HT receptor subtype was identified by immunocytochemistry, receptor autoradiography and functional investigations. Intravital fluorescence microscopy observations of the rat incisor preparation showed that histamine, BK and PGE2 increased permeability, whereas isoproteranol caused partial inhibition of the BK-induced increase. In an induced pulpal inflammation model using plaque extract, blood flow increased over 40% in the moderately inflamed pulp, which demonstrated severe vasodilation and polymorpholeukocyte accumulation. In the partially necrotic pulp, blood flow decreased nearly 35%. Results of this study clearly show that there is a high structural/functional correlation in pulpal microcirculation in inflammation. As demonstrated in this presentation, the effects of inflammatory mediators on pulpal microcirculatory hemodynamics are complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Dentinal sensitivity is a common complaint of patients. Removal of cementum or enamel leaves the dentin exposed allowing various stimuli to produce fluid movement through the dentinal tubules. These fluid movements are believed to activate pulpal sensory nerves leading to pain. Various therapeutic approaches have been investigated to treat this problem. Resins, fluoride compounds and oxalate solutions have been used to block the dentinal tubules. KNO3 and SrCl2 are active ingredients in desensitizing tooth pastes but neither compound reduces the permeability of dentine. The ability of various solutions to decrease hypertonic (3M NaCl) evoked nerve activity was tested in the canine teeth of anesthetized cats. Excitatory and desensitizing solutions were placed into a deep dentinal cavity prepared over the incisal pulp horn. An electrode used to record nerve activity was also placed into this deep cavity. KNO3 and other K+ ion containing solutions elicit a biphasic effect on nerve activity. Immediately following application of these solutions into the deep dentinal cavity there is a brief burst of high frequency spike activity. Following this brief period of excitation, the intradental nerves are silent and respond weakly to hypertonic NaCl. CaCl2 and other divalent cation solutions also inhibit hypertonic NaCl induced nerve activity, but have a weaker effect than that exerted by K+. These observations can be explained based on the effects of various ions on nerve excitability. Increasing the K+ ion concentration in the vicinity of the dentinal nerve terminal depolarize and activates the nerve fibers. Following a prolonged period of depolarization the action potential mechanism is inactivated. Divalent cation solutions stabilize the nerve membrane without changing the membrane potential. Desensitizing solutions do not decrease nerve activity by an effect on pulpal blood flow. This experimental model does not entirely explain the clinical action of these desensitizing agents. The role of inflammation in hypersensitivity and dental pain is currently being investigated.

Protein modifications such as phosphorylation and dephosphorylation are known to control several cell functions including regulation of the cell cycle, signal transduction and enzyme activation/inactivation. Bone and dentin contain highly phosphorylated anionic proteins that appear to be involved in the regulation of mineralization. This study was designed to identify and characterize the enzyme(s) responsible for phosphorylation (kinases) of dentin phosphoprotein (DPP) during dentinogenesis. DPP-protein kinase activity was demonstrated in a crude homogenate of dental pulp and odontoblast cells. In parallel studies, oligonucleotides to conserved amino acid sequences present in the active site of kinases were constructed and used to screen a lambda-gt11 tooth organ cDNA library. Several cDNA clones were isolated, the size of the insert determined by PCR (polymerase chain reaction) amplification, and in situ hybridization was used to determine cellular localization during tooth organ development. Preliminary evidence provides additional molecular determinants involved with candidate kinases responsible for DPP phosphorylation and dentinogenesis.

This study is part of a collaborative study entitled "Life-style and health" which is being conducted in Finland, India and Tanzania, using the same methods. The aim of the study is to describe health habits (smoking, alcohol consumption, use of medical drugs, exposure to sugars and hygiene habits) in Viekijärvi, a village in eastern Finland. Of the villagers 50% of those aged 20 years and over were randomly selected to take part in the study. Of these, 72% (n = 179) returned the standard questionnaire they had been sent. Smoking was as common among men in Viekijärvi as in Finland in general, but less common among women. Alcohol consumption reflected the national consumption. The use of medical drugs was high: 45% of respondents used such preparations daily. The most common exposure to sugar on a daily basis was sugar-sweetened coffee. Most people in Viekijärvi (89%) brushed their teeth at least once a day. A strong positive correlation was found between frequencies of toothbrushing and handwashing mirroring unidimensional hygienic behaviour. The results of this study will form a basis for a health promotion programme, to be developed by the villagers themselves.

Dentine hypersensitivity is a common painful condition about which relatively little is known. A review of the literature reveals that most research has been concerned with the clinical assessment of therapeutic agents. However, even here there is little information concerning the actual mode of action of such agents. Many clinical aspects of the condition also appear anecdotal at best and there is always a need to consider a differential diagnosis to exclude other causes of dentinal pain. Detailed prevalence figures are not available for dentine hypersensitivity as it affects different groups, although age and possibly gender differences are apparent. Additionally, the condition shows predilections for certain oral sites which may be of aetiological relevance. Consistent with the hydrodynamic theory hypersensitivity lesions reveal large numbers of widened dentinal tubules at the surface and patent to the pulp. The use of dentine replica techniques could prove useful in objectively studying the condition and monitoring treatments. It is apparent that in clinical management little attention has been paid to factors which expose dentine and open tubules. Without consideration of aetiological factors the management of Dentine Hypersensitivity may be compromised.

The effect of chronic exposure of dentin to the sensitivity of intradental nerves was studied in dogs. The dentin of canine and incisor teeth was exposed one week prior to the experiments in which 34 single fiber units dissected from the inferior alveolar nerve were recorded. In the teeth with acutely bared dentin 36 nerve fibers were tested. SEM of the chronically exposed dentin showed that practically no tubule apertures could be found since the surface was covered with bacteria and oral debris. This coating had to be removed by drilling and acid etching before any responses could be evoked. When compared to the teeth with acutely exposed dentin, the sensitivity of the fibers responding to drilling, probing, osmotic stimulation, and air blasts applied to the dentin was weakened in the chronic cases, in the sense that fewer units of those tested responded. However, cold evoked nerve activity only in some chronically exposed teeth, suggesting sensitization of the nerves. TEM revealed electron-dense substance in the dentinal tubules of the chronic teeth. Some of the material was evidently cellular remnants aspirated from the pulp and some of it, staining more faintly, could be extravasated plasma proteins. In the acute cases the tubules were emptier. Light microscopy showed histological injuries in the pulp-dentin border. It is concluded that the decrease in the responsiveness of the pulp nerve fibers in the chronic cases was due to the changes in the dentin.

The hydrodynamic theory of dentin sensitivity is based on the premise that sensitive dentin is permeable throughout the length of the tubules. Such a condition may permit the diffusion of bacterial products across dentin to the pulp where they may cause irritation of pulpal soft tissues. However, the slow outward movement of dentinal fluid tends to flush the tubules free of exogenous substances. This balance between the inward diffusion of exogenous substances, whether bacterial or the active ingredients in desensitizing medicaments, and the cleansing action of dentinal fluid flow needs to be examined experimentally.

Fluid movement in the pulp depends largely upon the physiology of the blood vessels; normally there is a net efflux of fluid and proteins from the capillaries into the extracellular environment. Most pulp capillaries lie close to the odontoblast layer and in order to see whether fluid can pass between the odontoblasts into the predentin we have perfused the vessels of molar tooth germs in anesthetized piglets with the electron dense tracer lanthanum. The results show that the tracer permeates the capillaries but encounters a barrier to permeability at the apical (predentinal) ends of the odontoblasts. The completeness of the barrier to the tracer lanthanum is discussed together with structural evidence of tight junctions between odontoblasts in both pigs and humans and the presence of collagen fibers through the tight junctional zone. It is concluded that there is little or no evidence that pulp fluid is normally confluent with predentin. An advantage of this arrangement may be that by maintaining an enclosed microenvironment it permits regulation of the orderly process of matrix deposition and mineralization of predentin to dentin. In order to maintain constant vascular and extracellular fluid pressures the capillary efflux has to be balanced by fluid removal; recent work in cats has shown that lymphatic vessels are available to transport fluid out of the pulp. In this paper the differences in the intrapulpal distribution of these vessels have been extrapolated to human teeth in an attempt to explain certain variations in the symptoms and progress of pulpal inflammatory conditions.

Small diameter afferent nerves in the pulp contain vasoactive peptides (tachykinins and CGRP) which are released upon nerve stimulation causing long lasting vasodilation. The aim of the present experiments was to study the contribution of afferent nerves in vasodilator reactions in the cat dental pulp when clinical procedures were applied. For this purpose the inferior alveolar nerve (IAN) was cut unilaterally 10 days prior to study. Lower canines were then subjected to various stimuli and blood flow responses in the pulp were monitored by laser Doppler flowmetry. Bipolar electrical tooth stimulation (5 impulses, at 2 Hz, 50 microA) and application of capsaicin (10(-4) M) in a deep cavity instantaneously induced long lasting increases in pulpal blood flow in control teeth but not in denervated teeth. Bradykinin (10(-3) M) applied locally produced a more rapid and larger pulpal vasodilation in innervated than in denervated teeth. Intermittent grinding (3 times, 1 sec each) of surface dentin with a round diamond bur instantly increased flow in control teeth by 53%, whereas in denervated teeth the response was delayed and significantly smaller (16% increase). Deeper preparations produced long lasting responses of similar magnitude on both sides but the onset was much slower in denervated teeth. Percussion and low intensity ultrasonic stimulation (1 sec) instantly caused increased flow in control teeth but not in denervated teeth. The effect was abolished by local anesthetic (mepivacaine) injection apically. Sympathectomy and acute IAN denervation did not alter the responses. The results show that afferent (sensory) nerves contribute importantly to hemodynamic reactions in the pulp in response to clinical procedures.