On clinically sound buccal and lingual surfaces of 130 extracted teeth, class V cavities were prepared and filled. In some cases previously filled teeth were used. In vitro caries around the fillings was produced by immersing the teeth in an acid-gelatin system, the pH of which was held within the values 4.0–5.2 by means of lactic acid. Duration of the experiments varied within the range of 5–200 days. A number of teeth which were filled, but not exposed to the acid gelatin, were used as controls. Ground sections in series were prepared through the teeth with the fillings in situ and studied by ordinary transmitted and incident light, polarized light, ultraviolet light, and microradiography. The lesions produced consisted of two regions, the outer lesion and the cavity wall lesion. In the enamel the shape of the former and its relation to the latter seemed to be influenced by the angle made by the cavity wall with the prisms. The outer lesion developed by an action on the outer surface of the enamel or cementum and showed the features of a primary attack. Usually the wall lesion was a narrow subsurface defect in the enamel or the enamel and the dentine of the cavity wall. It represented an initial stage of the caries process and gradually encompassed the whole filling without penetrating deeply into the tissue. The development of the wall lesion was determined by the amalgam-dental tissue interface into which hydrogen ions must have diffused from the acidified gelatin. The demineralization seemed to have acted perpendicularly to the surface of the cavity wall in which reprecipitation had taken place in a few cases.
In order to compare the distribution of elements in carious cementum and root dentin with the morphology of the lesion, a correlated electron probe microanalysis and microradiographic study was carried out. Ground sections of human teeth showing early stages of root suface caries were microradiographed and subsequently analyzed for the presence of Ca, P, F, S, Mg, Na, Fe, Cu, Zn Sn, and Ag. The results show that caries in cementum starts as a partial decalcification which soon reaches the peripheral dentin and may extend to a depth of a third of a millimeter without any loos of surface contour at the light microscopic level of observation. The pattern of dissolution and reprecipitation of mineral components seems to follow the pattern seen in dentin caries. Although reprecipitation of mineral forming a hypercalcified layer at the surface of the lesion occurs regularly, a surface layer of increased radiopacity may be found even in the absence of this process due to the adsorption of foreign, heavy elements in the surface layer of carious cementum. The relatively high F content normally found in the outer layer and the additional accumulation of F in this layer both from saliva and incident to the outward diffusion of dissolved mineral, result in the development of a particularly distinct zone of recalcification at the surface during the early stages of cementum caries.
Earlier studies, have indicated an increased mineral content in the surface layer of cementum which has became exposed to the oral cavity as a result of gingival retraction. The purpose of this study was to characterize this process more precisely by elemental analysis. Serial ground sections of suitably embedded teeth from residents of a nonflooridated area were microradiographed. Sections showing 'exposed cementum with an increased radiopacity of the surface layer were processed for electron probe analysis and electron microscopy. Characteristically, the radiopaque zone had an elevated Ca and P content (7-10 % increase), unchanged Mg, extremely high F (up to 1.9 %) and elevated S (O-lOO % increase), as compared to unesposed cementum. The highest F values occurred concomi,tantly with the highest Ca and P. F showed a rapid drop and a leveling-off at a varying distance from the root surface. Electron microscopy showed increased crystal size and imjproved crystallinity in the hypercalcified layer, while demineralized sections indicated an alteration of the organic matrix. In the absence of detectable caries, exposed cementum may develop a highly calcified surface layer, am F content higher than any other calcified tissue, as well as a subsurface condensation of organic material of exogenous origin.
– Human coronal dentin was studied by light microscopy and microradiography. The material comprised 50 permanent and 10 primary anterior teeth and microradiographs of 63 primary anterior teeth from a previous study. Both intact and worn teeth were examined. Ground sections in the long axes of the crowns in the buccolingual and mesiodistal planes were prepared, as well as transverse sections. A few crowns were also examined in toto. A system of giant tubules extending from the border of the pulpal cavity could be followed, though not continuously, through the secondary and primary dentin almost to the incisal dentinoenamel junction was observed. The lumina of the tubules were 5–40 μm wide and bordered by an approximately 10‐μm‐wide, usually hypermineralized rim of dentin in which only a few dentinal tubules were clearly discernible. The giant tubules were located along the mesiodistal axes of the teeth. The number of such tubules varied between 0 and 30.
Caries was produced around class V fillings in human teeth in situ. The material consisted of 44 teeth, including 13 controls. The teeth were scheduled for extraction for orthodontic or prosthodontic reasons and the experimental period ranged from 21 to 180 days. Age of the patients ranged from 11 to 62 years. For the production of caries a preformed orthodontic band was attached to the teeth in order to induce accumulation of plaque material. Following extraction, ground sections were prepared and studied mainly by polarized light microscopy and microradiography. The pathogenesis of observed in vivo lesions was found to correspond to that of the in vitro lesions around fillings described by Hals and Nernaes [1971]. The ‘cavity wall lesion’ was seen in 11 out of 28 experimental cases. In experiments with a duration of 100 days or more, the subsurface demineralization of the ‘outer lesion’ was often followed by a secondary surface demineralization. The positively birefringent zone of enamel caries, seen when examined in quinoline, was common and was observed as early as after 21 days. In dentinal tubules ending at the cavity wall, bodies supposed to be ‘caries crystals’ were observed in 4 cases.
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