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

The effects of substance P (SP) administration on vascular permeability were studied in the dental pulp (DP) of upper and lower incisors and in the submandibular gland (SMG) of male rats. Vascular permeability was assessed by means of extravasation of Evans blue dye. SP was diluted in 0.5% bovine serum albumin (BSE) and infused into the left common carotid artery. Separate groups of animals receive chloropyramine, an H1 histamine receptor antagonist (10 mg kg-1 i.v.) or indomethacin, a prostaglandin synthesis inhibitor (4 mg kg-1 i.v.) prior to SP infusions. Infusion of SP for 5 min increased plasma extravasation both in DP and SMG, with a threshold of about 30 pmol min-1 and 74 pmol min-1, respectively. Enhanced salivary secretion was also observed. Although the administration of 74 pmol min-1 of SP significantly lowered the systemic blood pressure, experimental hypotension elicited by haemorrhage did not influence vascular permeability in either organ tested. After chloropyramine administration the SP effect on vascular permeability in both DP and SMG was abolished. Indomethacin pretreatment failed to prevent the permeability-enhancing action of SP. Our results suggest that substance P increases both pulpal and glandular plasma extravasation in the rat indirectly, via the release of histamine and the activation of H1 histamine receptors.

The arousal of the two components of pain (the first rapid or sharp pain and the second dull pain) are considered to be related to activation of A delta- and C-type nociceptive primary afferents, respectively. The same dichotomy of pain sensations may also exist in teeth, although due to the short distance between the site of stimulation and the brain the two sensations might not be as clearly separated as in stimulation of, for example, the extremities. The sensations evoked by stimulation of human teeth vary according to the type of the stimuli applied. Low-intensity electrical stimulation is able to induce non-painful (prepain) sensations. At high current intensities pain is evoked. Drilling, probing and air-drying of exposed dentin induce only pain. Most studies also indicate that thermal stimulation only induces painful sensations. The quality of dental pain can vary. Typically, dentinal stimulation of teeth with healthy pulps induces sharp pain. On the other hand intense heat stimulation can result in dull pain which radiates to a wider area of the face and jaws. This component of the stimulus-induced pain seems to share some characteristics of toothache associated with painful pulpitis. Single fibre recordings of intradental nerve activity in experimental animals have shown that in addition to A-fibres a considerable number of C-type primary afferents innervate the dental pulp. This is in accordance with the results of neuroanatomical studies, which indicate that 70-80% of pulpal axons in human, monkey, dog, and cat teeth are unmyelinated. Intradental A- and C-fibre groups seem to be functionally different and can be activated separately by certain external stimuli. Comparison of the response characteristics of the pulp nerve fibres and the sensations induced from human teeth indicate that: 1) A-fibres are responsible for the sensitivity of dentine and thus for the mediation of the sharp pain induced by dentinal stimulation, 2) Prepain sensations induced by electrical stimulation result from activation of the lowest threshold A-fibres some of which can be classified as A beta-fibres according to their conduction velocities. Comparison of the responses of the A beta- and A delta-fibres indicate that they belong to the same functional group, 3) Intradental C-fibres are activated only if the external stimuli reach the pulp proper. Their activation may contribute to the dull pain induced by intense thermal stimulation of the tooth and to that associated with pulpal inflammation.

SEM and TEM photomicrographs were presented of the smear layer and several dentin-adhesive interfaces. It was shown that as the wetting and penetration of the dentin adhesive increased, the shear bond strength also increased. Three categories of dentin adhesives were presented. Category one included Scotchbond, Dentin Adhesit and Gluma, with shear bond strength values between 5 and 7 MPa; the second category, dentin adhesives based on Dr. Bowen's research, included Tenure and Mirage Bond, with shear bond strengths between 8 and 14 MPa; the third category included Superbond and Scotchbond 2, with shear bond strength values up to 20 MPa. Failures occurred at the interface or in the resin adhesive for materials in categories one and two; failures occurred through the dentin or composite for materials in category three.

DGI-II has been linked to the group specific component (Gc) on 4q and to interferon induced protein 10 (INP10) on 4q. We studied a three generation family with DGI-II along with a four generation DGI-II family to more precisely place DGI-II in the existing genetic map of 4q and to determine if genetic heterogeneity existed between various DGI-II families. Affected family members had brownish discoloration of the teeth, enamel fracturing and radiographic evidence of coronal and radicular pulp chamber obliteration. Thirteen polymorphic markers on 4q were studied including D4S35, D4S1, ALB, Gc, MGSA, AR, INP10, ADH3, FGFB, EGF, IL2, IF, and MNS. Gc and MNS blood group antigen typing were done using commercial SERA. Restriction fragment length polymorphism analysis using Southern blotting was done on the remaining markers. Pairwise linkage analysis was performed using the procedures of Morton. Tight linkage between DGI-II and eleven genetic markers, including Gc and EGF, was excluded. The tightest linkage with DGI-II was identified with the probe INP10 at theta = 0.0 with lod = +3.91. However, INP10 RFLP differences were detected between the families, such that DGI-II correlated with different alleles in each family. Results from this study demonstrated that DGI-II may possibly arise from more than one genetic mutation.

Dentin phosphoprotein (DPP, phosphophoryn) is the major non-collagenous protein component of the dentin extracellular matrix. This highly acidic phosphorylated protein is solely expressed by ectomesenchymal-derived odontoblast cells of the tooth organ. Previous biochemical studies have suggested the absence of this protein associated with the human genetic disease dentinogenesis imperfecta (DGI) Types I and II. However, due to the normal degradation of human DPP during dentin maturation, it has not been possible to establish if these reported differences were due to changes in DPP expression or secondary degradation rates in DGI affected versus normal teeth. Recently, we have taken both a molecular and biochemical approach to address this problem. Molecular studies have utilized genetic linkage studies performed on several multi-generation informative DGI kindreds. These studies have determined linkage between DGI Types II and III and two markers localized to the long arm of human chromosome 4 in the region 4q11-4q21. The strategy used in our study was to map the DPP gene locus to the long arm of human chromosome 4, in the same region as DGI, using a DPP oligonucleotide probe and somatic hybrid cell lines. The results indicate DPP is not localized to any region of human chromosome 4. Our data indicates that a mutation within the DPP gene locus is not associated with DGI Types II or III. This data is supported by the identification of human DPP (95 kDa) within the dentin extracellular matrix of molars isolated from an affected DGI type II patient using a mouse anti-DPP antibody. However, this does not exclude the possibility that enzymes associated with DPP post-translational modifications (ie. phosphorylation or degradation) might be responsible for this genetic disease.

This paper represents an invited reaction to three papers presented at the International Conference on Pathobiology of the Dentin/Pulp Complex, June, 1991. Repair dentinogenesis following transplantation into normal and germs free animals are correlated with results elucidating the expression of dentin phosphoproteins, collagen, and osteocalcin. The importance of transcription and translation controls of dentin matrix components are discussed and reviewed. In addition, possible implications of a molecular chaperone protein, Hsp47, in controlling dentinogenesis is introduced. Future research directions are developed and include: (a) identification of odontoblast precursors; (b) delineation of markers for odontoblasts at varying degrees of differentiation; (c) characterization of environmental conditions leading to odontoblast differentiation; (d) determination of the nature of repair and regenerated tissues; (e) elucidation of transcription and translation control factors, and (f) mapping the human genome for dentin matrix constituents.

A comparison is made between the resorption of bone and the resorption of the mineralized tissues of teeth. The structure and function of osteoclasts are described well as the factors that regulate their activity. The cells resorbing the dental mineralized tissues are of the same cell type as osteoclasts. The dental tissues are covered by cementoblasts or odontoblasts which differ from the osteoblasts in that they do not respond to hormones and cytokines that stimulate bone resorption. Root resorption therefore seem to require damage of the cementoblastic layer in combination with necrosis or inflammation or replacement of the cementoblastic layer by osteoblasts. The root resorption that occurs at the shedding of the primary teeth is induced in a different way possibly by substance(s) from the reduced enamel epithelium. There seems to be no systematic study on the frequency and extension of root resorption in association with inflammatory or neoplastic conditions. It is suggested that dentigerous cysts and some epithelial tumors induce root resorption in the same way as the erupting tooth. The mechanisms by which some other tumors or tumor-like conditions cause root resorption are essentially unknown.

Using the quantitative 15 microns microsphere injection method, the effects of several restorative procedures on pulpal microcirculation in dog canine teeth were investigated. Pulpal blood flow (PBF) decreased steadily as the remaining dentin thickness (RD) became smaller with crown preparation without water spray. One hour after the preparation wit 1/3 RD (approximately 1 mm) PBF was reduced to 10% of the control, indicating that dry deep preparation has a deleterious effect on PBF. A careful preparation to an RD of 1 mm under copious water spray had a negligible effect on PBF. Dry preparation to an RD of more than 50%, on the other hand, caused a significant increase in blood flow through shunt vessels, AVAs and "U"-turn loops as determined with the 9 microns and 15 microns microspheres. These shunt vessel activities were especially prominent in the apical portion of the pulp, suggesting that the activation of the shunt vessels may be one of the compensatory mechanisms of the pulp in response to inflammation. In rat incisor teeth observed by intravital microscope, shunt vessels opened up as the incisor tips were drilled. Impression procedures after tooth preparation with water spray using the copper band with wax caused severe flow fluctuation as compared to rubber base material impression. In anesthetics, the use of epinephrine was found to be the single most important factor affecting pulp circulation. Whether it is by infiltration or mandibular block, the use of epinephrine containing anesthetic caused a severe reduction in PBF.(ABSTRACT TRUNCATED AT 250 WORDS)

This study was undertaken to investigate how various population characteristics affect the choice of different tooth cleaning methods and to estimate their role in preventing occurrence of plaque, calculus and gingivitis among rural adults in Tanzania. Two hundred adults aged 20 years and over were interviewed and clinically examined for plaque, calculus and gingival bleeding. A high proportion (97.5%) of the subjects reported that they clean their teeth every day. Among them, 69.4% used only indigenous tooth cleaning methods, 16.3% only factory made toothbrushes and 14.3% both. Twigs (Chewing sticks) were the most commonly used indigenous tooth cleaning method, followed by charcoal. Together with age, educational and occupational status and tribal origin significantly affected the choice of tooth cleaning method. Men had more often visible plaque than women (OR = 2.84). However, other sociodemographic factors and the method of cleaning teeth were not significantly associated with the occurrence of plaque, calculus or gingival bleeding.

During studies designed to improve the bonding of adhesive resins to tooth structure, it was found that methacrylates with both hydrophobic and hydrophilic groups promoted monomer penetration into suitably prepared dentin. The monomers impregnated and became entangled with the collagen fibrils of surface demineralized dentin, creating a hybrid layer after their polymerization. The identification, properties and function of the hybrid layer, a new biologic composite, are explained.