Einar Hals

Histopathology of in vitro Caries Developing around Silver Amalgam Fillings

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.

Correlated Electron Probe Microanalysis and Microradiography of Carious and Normal Dental Cementum

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.

Highly Acid SnF2 and TiF4 Solutions

In a previous in vitro study, a considerable fluoride uptake was found in scaled root surfaces following treatment with a TiF4 solution (1.1 M F, pH 1.0). In spite of the

Histopathology of Natural Caries around Silver Amalgam Fillings

The histopathology of natural secondary caries associated with silver amalgam fillings was studied and compared with the histopathology of experimental in vitro and in vivo

Histopathology of experimental in vivo caries around silver amalgam fillings.

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.

Natal and neonatal teeth; histologic investigations in two brothers.

Abstract The literature on teeth present at birth or erupting immediately after birth is surveyed briefly. A report is given of the eruption of the first tooth in three brothers. The oldest one got his teeth at the normal time. The second boy had a lower incisor that erupted nine days after birth (“neonatal tooth”). This tooth was shed when the boy was 6 years old, and it was a little smaller than the other lower incisors. The youngest boy had two lower incisors present at birth (“natal teeth”) which, however, were removed nine days later. The present article deals with the histologic investigation of the two natal teeth and the neonatal tooth mentioned. In the natal teeth the enamel, in which mineralization has not been accomplished, comers only the incisal two-thirds of the crown, while the cervical third is covered by cementum. Extensive enamel caries developed during these nine days when the boy was nursed solely by his mother. Signs of caries in the dentine could also be observed. In the dentine the incisal half is otherwise normal, while the cervical half shows a most irregular structure, namely, dentinal tubules decreasing in length toward the cervix, where they disappear completely, and further cell inclusions in empty spaces in the mineralized matrix. In the part of the dentine covered by cementum there is a peripheral zone of interglobular dentine with very small globuli. In the part of the dentine covered by enamel, the peripheral zone is normal. It is true of the whole bulk of dentine that any incremental pattern is hardly visible. Neither are the semilunar formations, visible in polarized light and indicative of spherical mineralization, present in their ordinary pattern. The dentinoenamel junction does not have the normal scalloped appearance. At the cervix the dentine shows a deposition of more or less regular bone tissue assuming the form of a root. No Hertwigs sheath is present. The cause of the formation of the irregular dentine and the bony root is supposed to be mechanical irritants due to the mobility of the tooth. The absence of Weils zone and the cell-rich zone in the pulp is not pathologic, but is in accordance with a normal. stage of development. An ascending pulpitis deriving from accumulations of bacteria in the basal pulp border can be established. These bacteria must have come from the oral cavity through the periodontal tissue in the same way as in deciduous teeth prior to their shedding. The neonatal tooth described has a root with extension as to be expected in a normal shedding tooth. A broad zone with spaces occupies the exterior part of the root dentine. The cervical third of the enamel is hypoplastic and hypomineralized. The familial tendency indicates that in these two brothers the natal and neonatal teeth have been formed in superficial position due to a genetic factor.

Effect of NaF, TiF4 and APF Solutions on Root Surfaces in vitro, with Special Reference to Uptake of F

The in vitro uptake of various ions in scaled root surfaces from TiF4 and acidulated phosphate fluoride (APF) solutions, both with 1.1 M F and pH 1.0, was compared with that from a NaF solution, 0.5 M F, pH 7.1, using electron microprobe analysis, microradiography and polarized light microscopy. The mean F concentration (1.7%) and the mean depth (17 μm) of zones showing F increase following treatment with TiF4 solution were much greater than in the NaF group. A fine layer of Ti-containing material covered the surface of the specimens. The APF solution caused even greater depositions of F, but a marked subsurface demineralization. Thus, TiF4 and APF solutions with the same F molarity and pH showed different effect on the root surfaces. The results indicate that the use of TiF4 in the topical application of fluoride may have several advantages. Further in vitro studies are warranted.

Electron probe microanalysis of secondary carious lesions associated with silver amalgam fillings

Secondary caries associated with silver amalgam fillings is characterized by outer lesions and cavity wall lesions. In this study the content of minerals and the penetration of elements from the amalgam into such lesions were analyzed. In sections of 11 teeth including cases of natural secondary caries and experimental in vitro and in vivo lesions around silver amalgam fillings the distribution of Ca, P, Mg, Zn, Sn, Cu, Ag and Hg was studied by means of two-dimensional X-ray images, linear scans and point analyses. Dentine wall lesions where microradiographs had shown increased radiopacity relative to intact tissue, exhibited considerably reduced Ca and P values. The outer portion of the radiopaque areas contained 5--8% Zn and Sn, decreasing to less than 0.1% at a varying distance up to 130 mum from the cavity wall. Hg was not detected, nor was Ag, except in one specimen. The increased radiopacity of this zone as observed on microradiographs is, therefore, obviously caused by the presence of Zn and Sn. Zn and Sn had also penetrated into the moderately demineralized enamel lesions, but the concentrations were generally lower than those observed in the dentine.

Penetration of ions from silicate cement restorations into Copalite--covered cavity walls.

This study aimed to asses the effect of silicate cement on Copalite -covered cavity walls in extracted human teeth. Class V cavities were prepared in 24 premolars and filled with silicate cement (Bio-Trey). Four cavities were unlined, the rest of the cavities were lined with 1 or 2 layers of Copalite before insertion of the restorations. After 6 months, 70-100 microns thick longitudinal sections of the teeth were studied by polarized light microscopy, microradiography and electron probe microanalysis. When imbibed in water or quinoline, a subsurface zone of altered birefringence was noticed in nearly all cavity walls. Nearly half of the cavity walls in the experimental groups showed a surface zone of increased radiopacity. In a few instances a subsurface radiolucent zone was present. By electron probe microanalysis F (0,4-3% by weight), Zn (1-4%) and Al (0,2-6%) were measured in the outer 10-60 microns of the cavity walls. The study shows that even with a double layer of Copalite, known to prevent microleakage, a desirable uptake of F and Al from silicate restorations into cavity walls can take place. Copalite does not prevent a phosphoric acid effect on the cavity walls.

Histopathology of experimental in vivo caries around silicate fillings

Caries was produced around 18 silicate fillings in permanent teeth in 12 patients, aged 14—60 years. The cavities were lined with 1 layer of Tubulitec® (Dental Therapeutics AB, Sweden), and insulated with a zinc phosphate base. The teeth were scheduled for extraction for orthodontic and prosthodontic reasons, and the experimental period ranged from 34—326 days with a mean at 131 days. Four teeth served as controls of the effect of the preparation procedure. Following extraction, ground sections were prepared, and examined mainly by polarized light microscopy and microradiography. Except for minor differences, the pathogenesis of the observed in vivo lesions was found to correspond closely to that of experimental in vitro caries around silicate fillings. Outer lesions occurred in 14 of the 32 »secondary caries risks» and in most cases revealed only slight demineralization. A cavity wall lesion was observed in the enamel in 24 out of 31 risks, and in the dentine in 3 out of 27 risks. Hypermineralization of ...