An in vivo method for microhardness measurements on human teeth

A non-destructive, in vivo method of measuring the enamel hardness directly on patients is described. Normal values on 39 students arc given and compared with those of five patients, one of whom suffered from abnormal oral acid concentration, and the others from the effects of various degrees of hyposialosis caused by radiologic treatment of tumors in head and neck. The difference between the two groups was significant below the 0.1% level. It was suggested that the method may be used to test the degree of salivary gland inactivation after radiologic treatment and the efficiency of different saliva substitutes used to alleviate the effects of hyposialosis.     

Histochemical study of giant tubule content in dentin of unerupted cow incisors

Abstract – Incisal dentin of mandible cow incisors was studied by incident light. The material consisted of 12 intact permanent unerupted incisors from 2-yr-old cows removed immediately after bleeding. These specimens were kept in an isotonic EDTA-sucrose solution to be decalcified while maintaining vitality of cellular components. Three of the specimens were successfully dissected in a mesiodistal plane, exposing the giant tubule lumens and their content. By the use of NBT, a compound reduced by the dehydrogenase enzymes of the electron transport in the inner mitochondrial membrane, it was concluded that the giant tubules contained vital cells. The giant tubules were also shown to communicate with the incisal part of the pulp cavity by wide openings.     

Dental caries and diet in an Alaskan Eskimo population

abstract – The diet and the prevalence of dental caries in a group of Alaskan inland Eskimos have been studied on two occasions. Considerable changes in living habits had occurred during the 8–10 intervening years. A marked change in diet was noted. The percentage of total calories obtained from protein had decreased by about 50 % and that from carbohydrate increased by nearly 50 %. The change in diet was accompanied by a drastic increase in the prevalence of dental caries. The DMFT rate for primary teeth showed an almost 90 % increase and the DMFT rate for permanent teeth of persons over 6 years of age exhibited a four-fold increase. The most dramatic change was observed in individuals 30 years of age or older. In this previously caries-free group, all subjects had developed caries in the course of 8 years.     

A histopathologic study of replanted teeth with superficially demineralized root surfaces in Java monkeys

abstract — Since unmineralized tissues are supposed to possess a resistance to resorption, and demineralized dentin implants induce bone formation and may be remineralized, it was thought worthwhile to study the effect of superficial demineralization of the root surface prior to replantation of the maxillary incisors in 14 Java monkeys. The investigation showed that this treatment caused an accentuated resorption and ankylosis of the tooth as well as other pathologic changes in the periodontium. The technique neither improves the healing of the replanted tooth nor prolongs the survival time.     

Transmission electron microscopy on sound demineralized guinea pig dentin

abstract – An investigation of the ultrastructure of sound demineralized guinea pig dentin was carried out by means of the electron microscope. ERL-4206® (vinyl cyclohexene dioxide), a new low viscosity epoxy resin medium was found superior to Epon-812® for the embedding of demineralized dentin for electron microscopic studies. The demineralization by means of 0.2 N HCl resulted in a poor preservation of the odontoblastic processes. No evidence for the existence of a hypermineralized peritubular zone was found. In contrast to human dentin the area adjacent to the tubules in guinea pig dentin was composed of dense bundles of collagen fibrils. In the vicinity of the predentin these bundles formed a 1 μm wide zone and were arranged parallel to the tubular axis. In the outer part of the dentin no marked differences were observed between the collagenous framework of the peritubular and the intertubular zones. Here too the preferred direction of the collagen fibrils was parallel to the tubules. The structure of guinea pig dentin differed markedly from that of human dentin but resembled the structure observed in rat dentin. It is possible that cross-striated collagen fibrils are essential for the induction of heterotopic bone formation. The bone-inducing capacity of guinea pig and rat dentin might depend on their high content of stable cross-striated collagen.     

Alveolar ridge augmentation in rats by Bio-Oss

Abstract – The purpose of the study was to examine if Bio-Oss initiated osteoinduction or osteoconduction when implanted into rats. Sintered and unsintered granules of the anorganic bovine bone Bio-Oss was implanted subperiosteally for alveolar ridge augmentation purposes and heterotopically in the abdominal muscles of rats. Light microscopic evaluation revealed no osteoinduction or osteoconduction in connection with sintered or unsintered Bio-Oss. A foreign body reaction was observed around both forms.     

Scanning electron microscopic studies on demineralized guinea pig dentin

abstract – Sound, demineralized adult guinea pig dentin was observed by means of the scanning electron microscope. The dentinal tubules were fairly regular, some of them containing odontoblastic processes (Tomes fibers). These fibers were smooth surfaced, branching and much smaller than the surrounding tubules. Their small diameters were probably caused by the preparation procedures. The inner tubular walls were rough, probbly because of interlacing collagen fibrils. The peritubular dentin was relatively compact and composed of a considerable amount of cross-striated fibrils. Similar fibrils were found in the intertubular zones where they were arranged in fiber-bundles giving the intertubular zones a honeycombed or spongelike appearance. Such a distinct honeycombed appearance was not found in transmission electron microscope studies of dentin. This discrepancy is possibly due to differences in tissue preparation. The relatively poor development of peritubular dentin compared with intertubular dentin is in agreement with other studies in animals with continued tooth growth.     

Psoriasis: a defect in the regulation of epidermal proteases, as shown by serial biopsies after cantharidin application

The possible role of epidermal serine proteases in the genesis of psoriatic lesions was investigated by sequential biopsies of the epidermal damage induced by topical cantharidin. In the skin of normal subjects, epidermal damage was followed by the transient appearance of proteolytic activity in the upper epidermis accompanied by temporary hyperacanthosis and perivascular inflammatory cells in the superficial dermis. In the uninvolved skin of five patients with psoriasis this proteolysis persisted longer, for more than 7 days. Thereafter, in three of the patients, the proteolysis abated, and this was followed by disappearance of the hyperacanthosis and the dermal infiltrate; in the other two psoriatics the proteolysis and hyperacanthosis increased, and a typical Koebner phenomenon ensued. Migration of neutrophils into the epidermis occurred as a later event. Thus the abnormal persistence of proteolytic activity in the upper epidermis after cantharidin application distinguishes the normal from the psoriatic skin injury response and might initiate the psoriatic lesion.     

Cellular events leading to blister formation in bullous pemphigoid

Cellular events occurring in eight patients with bullous pemphigoid were studied by light and electron microscopy. Sections (0.5 μm) of large surface area, overlapping blisters and surrounding skin, were examined and correlated ultrastructural studies were performed on selected areas. The peroxidase contained in granules of neutrophils, cosinophils and young macrophages was visualized by incubation with diaminobenzidine and hydrogen peroxide. This cytochemical reaction was used as a marker to study the release of granule enzymes from these inflammatory cells. The release of such enzymes from eosinophils and occasionally from macrophages on the epidermal basement membrane (more precisely in the lamina lucida) was demonstrated in the skin surrounding the blisters in four patients. The release of these enzymes was also observed in the floor of the blisters in all eight patients. It is well known that these granules contain several protcolytic enzymes. These observations are therefore consistent with the proposal that proteolytic enzymes of eosinophils play a pathogenic role during the initial stages of blister formation in bullous pemphigoid.