Crowns Of Human Teeth Research Articles

Effect of chloroform, xylene, and halothane on enamel and dentin microhardness of human teeth

Objective. The purpose of this study was to assess in vitro the effect of commonly used gutta-percha solvents on the microhardness of human enamel and dentin. Study Design. Crowns of human teeth were cut and treated with chloroform, xylene, and halothane. Treatment consisted of exposing the specimens for 5 or 15 minutes to the test solvents. Acid-treated and saline-treated specimens served as controls. After each treatment period, the specimens were rinsed, dried, and prepared for Vicker’s microhardness analysis. Vicker’s microhardness values for each specimen were recorded before and after treatment, and the differences were statistically compared. Results. A statistically significant decrease in enamel and dentin microhardness was found in most solvent-treated groups; the amount of the decrease was directly related to the exposure time. Conclusions. Chloroform, xylene, and halothane may cause a significant softening effect on both enamel and dentin. This softening is already apparent after 5 minutes of treatment.( Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;87:366-8)

Strain–structure relations in human teeth using Moiré fringes

Teeth are subjected to stress during normal function. The manner in which the resulting strain is distributed within the tooth is related to its structure. The Moiré fringe technique was used to map the in-plane strain distribution in slices from human tooth crowns under compression. The strain inside enamel is much less than in dentin, and there is a roughly 200 μm thick zone in dentin beneath the dentin–enamel junction which undergoes larger strain than the central coronal dentin. This zone is softer and less mineralized than the bulk of the dentin. The strain distribution in this zone along the dentin-enamel junction shows localized maxima on both the lingual and the labial sides. This study is consistent with the hypothesis that within the dentin there are structural adaptations for transferring and minimizing stress.

Effect of whole saliva components on enamel demineralization in vitro.

The aim of the present study was to use an in vitro enamel demineralization model (1) to confirm that whole saliva pretreatment conferred acid resistance to dental enamel and (2) to determine whether this phenomenon was attributable to specific salivary proteins, minerals, lipids, or some combination of these. Crowns of human teeth, each with one exposed window, were prepared in groups of ten. They were each pretreated by immersion individually in 4 ml of either (1) clarified whole saliva for 18, 72, or 168 h, (2) dialyzed saliva (3500 MWCO membrane), (3) the "flow-through" fraction from a DEAE separation of whole saliva (neutral and basic proteins), (4) the "eluted" fraction of a DEAE separation of whole saliva (anionic proteins), or (5) a combination of salivary lipids and the DEAE "flow-through" fraction of whole saliva (neutral and basic proteins). Control groups were group 6 with no pretreatment, group 7 pretreated for 168 h in a borate buffer (5 mmol/l), and group 8 pretreated in a mineral solution containing calcium (0.7 mmol/l) and phosphate (2.6 mmol/l). The crowns were then demineralized for 7 d in vitro (0.1 mol/l acetate, 1 mmol/l Ca and phosphate, pH 5.0) to produce artificial caries-like lesions. Lesions were assessed by cross-sectional microhardness profiles, and mineral loss (delta Z, micron x vol% mineral) calculated. Mineral loss (delta Z) values decreased linearly with the square root of time of pretreatment by whole saliva, confirming a time-dependent protective effect of salivary pellicle against demineralization of enamel.(ABSTRACT TRUNCATED AT 250 WORDS)

Occurrence and distribution of blackish staining on the crowns of human teeth obtained from an archeological excavation of a medieval site in Norway.

An excavation in Trondheim, Norway, in 1984-85, uncovered a part of the medieval (1100-1600) cemetery of St Olav's Church. Of 388 excavated skeletons, 248 had skulls where the condition of the jaws and teeth allowed examination. In 51 of these skulls the teeth exhibited a characteristic blackish staining. A higher percentage of affected skulls was found in areas with organic, woodchip layers than in areas with gravelly sand. Affected skulls tended to have a high percentage of their teeth stained, but the staining tended to be restricted to only one or two of the three tooth surfaces scored. Posterior teeth were more often affected than anterior teeth, the occlusal/incisal part more often than the cervical part, and the buccal/labial part more often than the lingual part. Nonerupted third molars could also be stained. Staining seemed to be hampered by calculus. Occurrence of staining was independent of the presence or absence of a coffin and of coffin type. The extent of staining (% of stained surfaces within a dentition) was independent of sex and age. High correlation was found between all four jaw quadrants. There was no independence between color of the jawbone and occurrence of stained teeth. It was concluded that the staining phenomenon probably can be ascribed to factors in the soil. In vivo predisposing influences cannot be excluded.

Dental enamel growth, perikymata and hypoplasia in ancient tooth crowns.

This paper describes the hypoplastic defects commonly seen on the surface of ancient human tooth crowns, excavated from archaeological sites, and presents a new method for estimating the ages at which these defects were initiated during life. The method is based upon examination of microscopic incremental structures on the enamel surface and it is possible also to apply it to reconstruction of the sequence and timing of dental crown development. The method of examination is non-destructive and allows full use to be made of the large numbers of complete, unworn dentitions which are found amongst archaeological remains.

Instruments for-measuring surface profiles: An application in the study of ancient human tooth crown surfaces

Abstract Two computer-interfaced instruments have been developed to measure the microscopic features of surfaces. One is based on a stylus which tracks across the surface being studied, while the other is based upon a measuring microscope. Both have wide potential applications within archaeology, but they are currently being used to measure layered structures on the surface of ancient human tooth crowns and programs have been developed to analyse the results.

A new technique for screening chemical toxicity to the pulp from dental restorative materials and procedures.

An in vitro test system is described which allows for quick and relatively inexpensive examination of the potential for chemical toxicity to the pulp of materials and procedures used in the restoration of single teeth. The test system consisted of two sequential steps. First, a restorative procedure was carried out on a freshly-extracted human tooth crown, to the pulpal surface of which had been attached a chamber filled with sterile tissue-culture medium. The preparation was kept at 37 degrees C. The culture medium was removed at day one and replaced with fresh medium, which was removed at day 3. In the second step, we used a standard tissue-culture toxicity assessment technique to examine both culture medium samples for the presence of chemical toxins. In use, this system gave results which correlated well with the known clinical potential for pulpal toxicity of various dental materials and techniques. For example, zinc oxide-eugenol used as temporary filling or base had no apparent potential for toxicity. Sealing a cotton pellet containing phenol into a cavity was of high apparent potential toxicity. Acrylic resin as intracoronal or extracoronal fillings showed potential for toxicity; this potential was decreased by lining with calcium hydroxide cement. Composite resin placed onto etched dentin had apparent toxic potential, but had less such potential when placed onto unetched dentin. The technique had some advantages over previously described in vitro toxicity test for restorative materials, because it included a step requiring diffusion of potential toxins into and through human dentin, and because it allowed for examination of variations in technique which mimic clinical behavior, and of materials used in sequence or in combination.

Reexamination of cariogenesis in relation to the distribution of enamel lamellae on crowns of human teeth.

Reexamination of cariogenesis in relation to the distribution of enamel lamellae on crowns of human teeth.

The autoradiographic pattern of the in vitro uptake of proline by the coronal areas of intact and carious human teeth

Whole crowns of human teeth, both immediately after extraction and after preservation in liquid nitrogen, were incubated for 6 h in the presence of [ 14C]- or [ 3H]-proline. Autoradiographs were prepared from sections of intact teeth and teeth with carious lesions of varying depths and location. The number of silver grains per cm 2 in the predentine, odonto-blast layer and pulp were counted in selected fields magnified × 430 representing the deepest parts of the carious lesions. No differences in the labelling pattern were observed between the intact teeth incubated freshly after extraction and those preserved in liquid nitrogen. The densest labelling of intact teeth was seen in the predentine and odontoblast layer. The alterations under initial dentine caries appeared as increased labelling of the predentine and decreased labelling of the odontoblast layer; no alterations were observed in the underlying pulp. In advanced lesions, the predentine labelling decreased and that in the odontoblast layer and pulp increased. In the initial stages, caries seems to activate collagen synthesis in a relatively restricted area of the underlying structures, but in more advanced stages, caries seems to increase the odontoblastic cellular polypeptide chain formation but prevent further maturation of the collagen.

Distribution with age and attrition of peritubular dentine in the crowns of human teeth

Sections of 37 human canine teeth, 7 unerupted, cut transversely at 3 levels occlusal to the pulp, were microradiographed; tubules were counted in groups according to the degrees of tubule closure. In unerupted teeth, there was no consistent variation with age in the numbers of the 4 types of tubule at any level of section, or between the levels of single teeth. With attrition scores 0, 2 and 3, peritubular dentine increased progressively with age, a pattern less evident with attrition score 1. When attrition and age were controlled statistically, tubule closure decreased markedly from outer to inner levels and open tubule counts increased markedly in the same direction. Volume fraction analysis on sections from an intermediate level showed that peritubular dentine increased markedly with attrition, and the tubular lumen reduced reciprocally. The amount of intertubular dentine remained constant. Kendall partial rank correlation coefficients showed a closer relationship between attrition and tubule closure than between age and tubule closure in erupted teeth.

Measurements of Cervical Undercuts of Human Tooth Crowns

The dimensional factors of the cervical undercut of the human teeth were measured. The facial and lingual undercuts showed considerable deviations in depth, width, and inclination to the crown axis and the food stream. The proximal undercuts showed a uniform depth of 1 +/- 0.3 mm with some deviations in width and inclination.

The relationship between the surface area of the enamel crowns of human teeth and that of the dentine-enamel junction

The surface area of the enamel and that of the dentine-enamel junction and the volume of enamel were calculated using a computer-based three-dimensional reconstruction technique. The surface area of the dentine-enamel junction was compensated for its pitted nature. Different individual teeth had wide variation in surface areas but, for the same kind of tooth the ratio between the surface area of the enamel and that of the dentine-enamel junction was very similar. Only a small amount (8–17 per cent) need be added to the thickness of crystals emerging normal to the enamel surface to account for the difference in surface areas. If it is assumed that crystals have uniform width and thickness, the angle of emergence of the crystals observed is sufficient to provide the required increase in the enamel surface area.

Measurements of cervical undercuts of human tooth crowns (author's transl)

Measurements of cervical undercuts of human tooth crowns (author's transl)

人の歯冠象牙質表面構造について

The dentin surface of human tooth crown was observed by means of scanning electron microscope and the following results were obtained. 1. Very clear picture of shallow depressions (foveola eburnea, Dentinfurche) showing fine network structure was obtained by lower magnification which demonstrated markedly different patterns in size and shape of respective depression according to the difference of tooth kinds used and sites of the crown observed. 2. By the use of higher magnification, not only came smaller depressions that subdivided each depression in sight, but also the presence of numerous pits that further subdivided the smaller depression and were presumed to be remnants of ameloblasts (Tomes' processes) was confirmed lying among complicated bundles of Ebner' fibrils.

A mineralized cuticular structure with connective tissue characteristics on the crowns of human unerupted teeth in amelogenesis imperfecta: A light and electron microscopic study

Premature degeneration and absence of the reduced enamel epithelium was observed in two unerupted teeth from a patient with amelogenesis imperfecta. This epithelial degeneration was accompanied by the patchy formation of a mineralized cuticular structure resembling cementum on the follicular surface facing the enamel. The demineralized cuticle showed histochemical evidence of a high content of collagen and acid mucopolysaccharide. Electron microscopic studies failed to reveal the presence in the cuticle of typically banded collagen fibrils. The cuticle was granular and showed a laminated internal structure. Although the cuticle may represent a form of afibrillar cementum, it should be noted that its formation appeared unrelated to direct cellular synthesis. Rather, it appeared to be associated with the degenerative process affecting the reduced enamel epithelium. The possibility that cuticle formation is dependent on adsorption by the enamel of connective tissue components was suggested. The degeneration of the reduced enamel epithelium would merely allow these connective tissue components to gain access to the enamel surface. The resemblance of the coronal cuticle in amelogenesis imperfecta to that found near the cemento-enamel junction of normal human teeth was pointed out, both with respect to ultrastructure and possible origin. It may be that these cuticular structures should be considered under the category of acquired pellicles with the understanding that their formation occurs in unerupted teeth, in areas of the crown not covered by an intact layer of reduced enamel epithelium.

The decalcification and discoloration of intact noncarious human tooth crowns by an oral strain of lactobacillus acidophilus

The decalcification and discoloration of intact noncarious human tooth crowns by an oral strain of lactobacillus acidophilus

REVIEW OF BOOKS AND ARTICLES

Yahres, Herbert. Your teethhow to save them.Sandler, H. C., and Struscer, Harry. Studies in public health dentistry: dental treatment needs of 3,282 children aged 2 to 16 years, in New York City.American Dental Association. Compulsory health insurance is not the answer.Wisan, J. M. and Gruebbel, A. O. Dental health habits: a questionnaire survey.Entine, Martin. A survey of dental diseases as a diagnostic aid in rheumatic fever.Lawrence, J. D. American dentistry.Scott, D. B., Kaplan, Harry and Wyckoff, R.W.G. Replica studies of changes in tooth surface with age.Fosdick, L. W., and Ludwick, W. E. Ammonia content of dental plaque in relation to dental caries.Engel, M. B. Glycogen and carbohydrate‐protein complex in developing teeth of the rat.Becks, Hermann, and Jensen, A. Dental caries prevention service.Dretsen, Samuel, Green, H. I., Carson, Bess C., and Speis, T. D. The in vitro production of a “yellow‐brown melanin‐like pigment” in organic matrix of noncarious human tooth crowns by methylgiyoxal (pyruvic aldehyde) and acetol (acetyl carbinol).

The in Vitro Production of a "Yellow-Brown Melanin-Like Pigment" in the Organic Matrix of Noncarious Human Tooth Crowns By Methylglyoxal (Pyruvic Aldehyde) and Acetol (Acetyl Carbinol)

The in Vitro Production of a "Yellow-Brown Melanin-Like Pigment" in the Organic Matrix of Noncarious Human Tooth Crowns By Methylglyoxal (Pyruvic Aldehyde) and Acetol (Acetyl Carbinol)