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

Regeneration and morphological changes in sensory peptidergic nerves in pulp and periodontium were studied after general dental trauma by means of immunohistochemistry. In control teeth also the total nerve supply was demonstrated by using antibody to the general neuronal marker, protein gene product (PGP)9.5. Two experimental rat models were used, i.e. tooth replantation and induced traumatic occlusion. Results from these studies are reviewed here. In the controls, the PGP9.5-immunoreactive(IR) nerve supply in pulp and periodontium was generally denser compared to CGRP-IR and SP-IR nerves. In the replanted teeth, regeneration of CGRP-IR nerves closely followed the pulp cell renewal. Density and distribution of the regenerated nerves showed two different patterns which seemed to depend on the capacity of the renewed pulp to form postoperative dentine. The nerve density never reached the same level as the controls. In teeth not able to form irregular dentine, the pulp was sparsely innervated and the pulp cavity was filled with innervated bone. Nerve responses in CGRP-IR and SP-IR nerves after unilateral induced traumatic occlusion in the first maxillary molar were studied at different observation periods up to 30 days. After 5 days, localized morphological nerve changes were found both in the pulp and periodontium within the total rat molar dentition. With increasing observation periods, the pulpal neural changes progressed and were extended to all pulpal areas compared to the periodontium, where the nerve responses remained localized to cervical and apical tissues throughout the experiment.

There is a general agreement that the extracellular environment plays a critical role in controlling cell behavior. Thus, significant research efforts have focused on understanding the effects of extracellular matrix proteins on cell function. In particular we have focused on determining the role of adhesion proteins in the regulation of root formation. Using an OPN antibody, 2arN (generously provided by Drs Craig and Denhardt), the expression of OPN during root formation was determined. OPN (osteopontin) is a bone-associated adhesion protein. OPN was expressed in the dental follicle region of molars obtained from 3 day old CD-1 mice, but was not expressed in the odontoblast layer. In contrast by day 8, positive staining was noted in the odontoblast layer, as well as in the area of Hertwig's epithelial root sheath. However, at this same time point no positive labeling for 2arN was observed in the enamel organ or in the dental papillae cells. By day 15 positive staining for OPN was seen in the area of the periodontal ligament, as well as the region of primary deposition of extracellular matrix onto dentin. Also determined was the ability of fibronectin, OPN and dentin sialoprotein (DSP) to promote the attachment of dental ectomesenchymal cells, in vitro. Interestingly, these cells attached remarkable well on bacteriological dishes (control) in the absence of an adhesion protein. DSP did not increase cell attachment beyond that observed for control cells. In contrast, both fibronectin and OPN enhanced cell attachment. These studies, while preliminary indicate that OPN is expressed in a unique fashion during root development, thus suggesting a regulatory role for such adhesion proteins during root formation.

Current methods for diagnosis of pulpal pathosis are often inadequate and there is a need for an in vivo method to visualize dental pulp tissue. This report compares micromagnetic resonance imaging (MMRI) with routine H & E histology on a cross sectional view of a molar tooth. The extracted tooth was imaged with a Bruker AM-400 NMR spectrometer modified with a microimaging accessory. The tooth was then decalcified and sectioned at the same level as the MMR image. Image intensity readings were acquired for specific areas of the pulp chamber for comparison with histology. The results demonstrate that there is a close correlation between the MMRI and the low power H & E appearance of pulp tissue.

The convenience of the so-called harmonious combinations of five basic radiographic cephalometric measurements (Segner), derived from multiple regressions and presented in the form of a correlation box, as a means of diagnosing skeletal malocclusion has been evaluated statistically. The study involved 55 untreated orthodontic patients 7-14 years old with Angle's Class I malocclusion. The correlation box was built stepwise on the basis of four linear regressions computed between five angular measurements (SNA, SNB, NSL/ML, NSL/NL, and NSAr). The regression analyses indicated that the correlation box was not accurate enough. The coefficients of determination for the regressions varied between 0.26 (for NSL/NL) and 0.63 (for SNB). Most part of the variation in NSL/ML, NSL/NL, and NSAr angles remained unexplained. Individual norms indicated by the box for the ANB angle seemed doubtful in many cases. The correlation box seemed to show the statistically most probable associations between measurements used. The combinations may be harmonious but the existence of other harmonious combinations cannot be excluded.

A brief review of the normal sensory innervation of teeth is presented, especially concerning the fibers that are immunoreactive (IR) for calcitonin gene-related peptide (CGRP). Numerous CGRP-IR fibers innervate coronal dentin at sites populated by primary odontoblasts and associated pulp cells that synthesize nerve growth factor (NGF). If the primary odontoblasts and adjacent pulp cells are lost as a consequence of injury, CGRP-IR dentinal innervation is greatly reduced. The responses of CGRP-IR nerve fibers to pulpal injury are reviewed. Those reactions show that pulpal sensory nerve fibers can alter the size, shape and immunoreactivity of their terminal branches in response to different stages of inflammation and healing.

Numerous studies using various animal and human models have reported changes in the morphology and metabolic activity of primary odontoblasts in the mature tooth pulp after perturbations of the tooth including cavity preparation and restoration, pulpal exposures and pulp capping with various capping agents. The first part of this study investigated changes in primary and replacement odontoblast activity after cavity preparation or pulpal exposure. Two groups of rats were used in this investigation. One group of rats had Class V cavities prepared to the DEJ of the first maxillary molars. These rats were immediately injected with 3H-proline and killed 15, 30 or 60 minutes later. Rats killed at day 1, 3, 5, 7, 10 or 14 were injected one hour prior to sacrifice. The second group of rats each had a pulp exposure that was capped with a calcium hydroxide containing material and restored with a composite resin. Rats were sacrificed as previously described. Tissue was processed routinely for ultrastructural analysis and E.M. autoradiography. The second part of this study consisted of an injection of 125I-fibrinogen one hour prior to a class V cavity preparation 1/2 the distance through dentin thickness. Rats were sacrificed at 5, 10, 15 and 30 minutes postsurgery. Differences in the location and distribution of the reduced silver halide grains were recorded as well as differences in the amount and distribution of the various organelles measured between primary and replacement odontoblasts. The results of this study suggests that primary and replacement odontoblasts were morphologically and physiologically dissimilar at the time periods tested in this study. 125I-fibrinogen was demonstrated within the dentinal tubules and in the floor of the cavity preparation as early as 5 minutes after completion of the cavity preparation. The preliminary results of the 125I-fibrinogen suggest that operative trauma can effect very rapid changes to the dental pulp leading to leakage of plasma proteins from the circulation, between odontoblasts, out of the tubules to the cut dentin surface.

Osteoblasts and odontoblasts are both derived from the same mesenchymal cell line. Our aim was to investigate whether the processes of bone destruction and dentinal caries are biologically similar. The working hypothesis was that after the initiation of caries in the enamel, its rate of progression in the dentine is regulated by cell-mediated factors. Experimental caries was induced in the rat with a high sucrose diet combined with Streptococcus sobrinus infection. Both destruction of dentine and its apposition in the pulp under the carious lesions were measured after vital staining with tetracycline. Caries progression and dentine apposition were higher in developing teeth prior to apex "closure" than in adult, fully-formed teeth. Rats placed on a cariogenic diet during tooth development had an increased rate of caries progression. Fluoride administration via the drinking water was associated with decreased dentine apposition and little progression of dentine caries during the developmental stages. Dentine apposition was enhanced in adult rats placed on fluoride administration, while caries progression was reduced, whereas in animals subjected to metabolic acidosis dentine caries progression was enhanced, with reduced dentine apposition. In contrast, alkalotic animals had less dentinal lesions and smaller ones than the controls. Three theories are advanced to explain the observed changes: (i) They may be associated with changes in alkaline phosphatase activity in the pulpo-dentinal complex, (ii) they may be mediated by ionic changes in the dentinal fluid, or (iii) they may reflect the liberation of growth factors from dentinal matrix.

An immunohistochemical study was made of the temporal changes in the expression of the c-fos oncogene protein in the spinal trigeminal nucleus complex (STNC) after three different types of dental injury. One hour after tooth extraction or pulp exposure, c-fos neurons appeared in the ipsilateral subnucleus caudalis, but there were very few c-fos neurons in the ipsilateral subnuclei oralis and interpolaris, and in the trigeminal main sensory nucleus and contralateral STNC. The great number of c-fos neurons was found 2-4 hours after injury, levels decreased by 8 hours after injury. Twenty-four hours after injury, the number of these neurons in subnucleus caudalis became very small. Shallow cavity preparation, however, did not induce an increase in the number of c-fos neurons at any selected postoperative time in STNC. These results indicate that c-fos neurons appear mainly in subnucleus caudalis very soon after severe dental injury.

Many factors have to be considered in developing new intense sweeteners to replace sugars in the diet for the benefit of dental health. These include their general properties, safety and toxicological evaluation, metabolic fate in the body, regulatory status and dental research documentation. The choice of new sweeteners with improved properties is expanding, with particular attention being paid to multiple sweetening, materials of natural origin and calorie control, as well as dental health gains, the distinction between non-cariogenic and anti-cariogenic properties, securing regulatory approval and developing an attractive range of foods and drinks containing the new materials.