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At least 847 records · Page 47Linked to original sources
PubMed1997

A light microscopic and ultrastructural examination of calcified dental tissues on horses: 4. Cement and the amelocemental junction.

Ultrastructural examinations showed the diameter of cement lacunae to be greater in infundibular cement than in peripheral cement of upper cheek teeth, which in turn was greater than in the peripheral cement of the lower cheek teeth. However, numbers of lacunae/unit area remained similar in these 3 dentinal region. Two types of cemental hypoplasia were found in equine cheek teeth. The first type was termed central infundibular cemental hypoplasia and was confined to the central region of infundibular cement. The cement adjacent to these frequently large defects was very porous and contained large vascular channels. In recently erupted cheek teeth, these central infundibular cemental defects were filled with connective tissue. The size of these cemental defects, the relationships of such defects with the occlusal surface and the degree of porosity of cement surrounding these defects may be important in the development of cemental caries. The second type of cemental defect was found at the amelodentinal junction of both peripheral and infundibular cement and was termed junctional cemental hypoplasia and appeared as spaces varying from focal, to long narrow defects along the amelocemental junction with the adjacent cement of normal appearance. Peripheral cement was deposited both directly, i.e. on unresorbed or resorbed enamel surfaces or indirectly, where the cement was separated from enamel by a thin calcified layer. The surface of unresorbed enamel had a pitted appearance, with the bases of the pits formed by enamel prisms and the pit walls by interprismatic enamel. The cemental surface of resorbed enamel contained depressions of variable shapes and sizes. These depressions which are believed to be caused by the resorption of enamel by odontoclasts were both focal and diffuse and were more marked on the cemental surface of infundibular as compared to peripheral enamel.

Animals↗
PubMed1971

Opal precipitation by marine gastropods (Mollusca).

The high silicon content of certain radular sites of the Patellacea (Mollusca, Gastropoda) is shown by infrared absorption spectrums to be fixed in the form of the mineral opal. Opal and goethite mineralize the cusps and bases of the teeth. The presence of opalized base plates only in the families Acmaeidae and Lepetidae appears to be of taxonomic significance. Minimum values of the volume of fixation and of the turnover rate of opal by the Patellacea are calculated to assess the role of this previously neglected taxon in biological fixation of silica in the oceans. The significance of these organisms points to the much needed study of the silica transport system in tissue-grade Metazoa.

Animals↗
PubMed1989

Cystic teratoma of the ovary: CT detection.

Computed tomography (CT) was performed in 38 patients with 41 benign cystic teratomas of the ovary and two patients with malignant transformation. CT depicted all tumors. The presence of fat in 40 of 43 cases (93%), tooth or calcification in 24 of 43 (56%), Rokitansky protuberance in 35 of 43 (81%), tufts of hair in 28 of 43 (65%), and a fat-fluid level in five of 43 (12%) allowed a definite diagnosis of ovarian cystic teratoma in 42 of 43 cases (98%). In the two cases of malignancy, single large (greater than 10 cm) plugs (with uptake of contrast medium in one) with a cauliflower appearance and an irregular border forming an obtuse angle with the inner wall of the cyst suggested malignant transformation. In three cases of benign cystic teratoma, a mucinous tumor (one benign, one borderline, one malignant) arising in the same ovary was seen at pathologic examination but was only diagnosed with the help of CT in two of three cases. Thickening of the tube was noted in two cases of torsion of the adnexa. CT findings were compared with findings at radiography of the abdomen and hysterosalpingography in 30 cases, ultrasound in 31, and magnetic resonance imaging in three. This study demonstrated that CT was the best procedure for imaging cystic teratomas of the ovary.

Adnexal Diseases↗
PubMed1977

pH gradients in the developing teeth of young mice from autoradiography of [14C]DMO.

The distribution of the weak acid [14C]DMO was studied in mice, 10-19 days old, by an autoradiographic technique that does not translocate or remove the compound. Calculations of pH values in areas of the developing teeth of these animals were made by comparing the photometric density of the distribution of [14C]DMO, as an indicator of pH, with that of 14C]NAAP, as an indicator of water content, which was reported in the companion paper. The cellular layers, i.e., odontoblasts, ameloblasts, etc., had pH values of 7.1 +/- 0.1; the pH values in enamel, predentine, and dentine ranged from 7.3 to 8.5. It is suggested that an alkaline matrix promotes nucleation and growth of hydroxyapatite.

Age Factors↗
PubMedDate not supplied

Cold stress in captive great apes recorded in incremental lines of dental cementum.

Incremental lines in dental cementum of museum specimens of 11 free-ranging great apes were compared to the respective structures in 5 captive specimens of known age-at-death, and with many known life-history parameters. While the dental cementum of the free-ranging apes was regularly structured into alternating dark and light bands, 4 out of 5 captive animals showed marked irregularities in terms of hypomineralized bands which could all be dated to the year 1963. Cementum preservation was insufficient in the fifth specimen and did not permit such a differentiation. All 4 captive apes had been kept in a zoo located in the northern hemisphere, where 1963 was characterized by an extremely cold winter. Since cold stress is a calcium-consuming process, the lack of available calcium in newly forming cementum could be responsible for the observed hypomineralization. The appositional growth characteristics of dental cementum serve as a record for such life-history events.

Adaptation, Physiological↗
PubMed2005

Role of phosphophoryn in dentin mineralization.

Mineral deposition is essential for the development of hard tissues like bone and teeth. In matrix-mediated mechanisms responsible for dentin formation, type I collagen defines the framework for mineral deposition and by itself is not sufficient to support nucleation of hydroxyapatite. However, in the presence of non-collagenous proteins, nucleation sites have been identified within the hole regions of the fibrils, and at these sites, mineral crystals can grow and propagate. Non-collagenous proteins constitute 5-10% of the total extracellular matrix proteins. They are embedded within the mineral deposits, suggesting a possible interaction with the mineral phase. During dentin formation, phosphophoryn (PP), an abundant macromolecule in the extracellular matrix, can initiate mineral deposition in localized regions by matrix-mediated mineralization mechanism. In our work, we have demonstrated that PP, due to its highly phosphorylated post-translational modification, can bind calcium ions with high affinity and at the same time aggregate collagen fibrils at the mineralization front. Molecular modeling has further demonstrated that the spacing of the carboxyl and phosphate groups present on PP might be essential for dictating the crystal orientation relative to the collagen substrate. Thus, PP may provide the interface linkage between mineral crystal and collagen fibrils.

Animals↗
PubMed1992

Organic structures of the hypercalcified peritubular matrix in horse dentine.

EDTA-insoluble organic structures of the hypercalcified peritubular matrix (PM) in horse dentine were observed by scanning electron microscopy. The PM was enveloped in double cylindrical structures composed of fibrillar sheaths in the inner and outer peripheries. Between the outer fibrillar sheath and intrinsic fibrils of the intertubular matrix, a calcified cementing membrane existed. Within the PM, warped cone-shaped structures of fibrillar sheaths, overlapping at intervals of 4-6 microns and semiconcentrically surrounding the dentinal tubule, extended from the inner fibrillar towards the outer fibrillar sheath. The cone-shaped fibrillar sheaths following the inner and outer fibrillar sheaths were identified as the incremental lines of the PM. Most of these fibrils may be collagen although it could not be confirmed, whereas non-collagenous organic materials in the lateral branches of the dentinal tubule are radially arranged in the PM. These EDTA-insoluble structures were three-dimensionally illustrated using an image-analysing system.

Acid Etching, Dental↗