Yukishige Kozawa

Changes in Bovine Dentin Mineral with Sodium Hypochlorite Treatment

Dentin powders from bovine incisors were treated with 10% NaClO solution. Differential thermal analysis (DTA) indicated the removal of organic material from the dentin sample following the treatment, since the exothermic reaction at 320°C had disappeared. X-ray diffraction studies revealed a change in the crystallinity of the dentin crystals and the formation of calcite after the treatment. Infrared absorption analysis showed that the band due to carbonate ions was weakened after the treatment, while atomic absorption spectroscopic analysis showed that magnesium ions had been dissolved from the dentin sample. The a-axis lengths of treated and heated dentin samples differed from those of untreated and heated samples. Whitlockite was always found in the untreated/heated samples, whereas it was absent in the treated/heated samples. The unit cell dimensions of the whitlockite indicated the partial substitution of magnesium for calcium. Magnesium ions seemed to be more effective than carbonate ions in forming whitlockite. These results showed that some magnesium and carbonate ions were removed from the dentin crystal structure upon NaClO treatment, while at the same time organic materials were removed from the dentin sample. It was suggested that crystals in the NaClO-treated dentin were similar to enamel crystals from a crystallographic viewpoint.

Neuroendocrine cells in Malassez epithelium and gingiva of the cat

Malassez epithelium has been designated as epithelial cell rests, the biological significance of which is still under debate. This study was designed to analyze Malassez epithelium for the presence of neuroendocrine cells. Gingival tissue was included as a positive control. Using immunohistochemistry, confocal and light microscopy, Malassez epithelium and gingival epithelium from mature cats (n=5) were examined for cells containing the neuropeptides calcitonin gene-related peptide (CGRP), substance P (SP), and vasoactive intestinal peptide (VIP). Both Malassez epithelium and the basal epithelial cell layers in gingival rete pegs regularly displayed cells immunoreactive to CGRP, SP, and VIP. The immunopositive cells were most frequently present in the epithelial cell clusters and strands of Malassez located in the cervical half of the periodontal ligament. Double immunolabeling revealed cellular co-expression of CGRP or SP with VIP, and the neuropeptides were co-localized in the cellular compartments. Labeled cells in both epithelia were occasionally supported by immunoreactive nerve fibers. This study shows that cells immunoreactive to CGRP, SP, and VIP are located within the cat Malassez epithelium. The localization of neuroendocrine cells verifies the diversity of this epithelium and confirms that Malassez epithelium is composed of different cell types, in common with epithelia from other locations. The presence of neuroendocrine cells in Malassez epithelium strongly suggests biological functions of this tissue, and the neuropeptide content may thus indicate endocrine functions of the cells.

Bone Formation Induced by Several Carbonate- and Fluoride-Containing Apatite Implanted in Dog Mandible

Synthetic hydroxyapatite (HAP), carbonate-apatite (CHA) and car bon te-fluoride-apatite (CFA) were implanted into dog mandible bone for 2, 3, 4, 5 and 6 weeks. The che mical composition and crystallographic properties of the synthetic apatites were examined using FT-IR, TG-DTA, AAS and X-ray diffraction. The comparative resorption in vivo for the experimental period was in the order: CHA >> CFA > HAP. CHA formed new bone com parable with the shamcontrol, and CFA induced fast bone-remodeling and newly formed Haversian s y tem. The results confirmed that CHA are potential bone-grafting materials and als o showed that CFA, compared to CHA or HAP materials, accelerate bone formation. Introduction Carbonateand/or fluoride-containing calcium hydroxyapatite are conside red as possible bone graft materials [1-3]. In vitro and in vivo studies showed that fluoride present in synthetic or bone apatite enhances osteoblastic activity [3, 4]. In vitro studies also showed that fluoride-containing apatite inhbited osteoclastic activity [5].The aim of this study was to com pare the biocompatibility and biodegradation carbonateand fluoride-containing apatites implanted in dog mandible bone. Materials and Methods Carbonate hydroxyapatite (CHA), carbonateand fluoride-containing apati te (CFA) and carbonateand fluoride-free apatite (HAP) were synthesized according to me hods previously described [6, 7]. Their chemical and crystallographic properties were determined us ing X-ray diffraction (XRD), FTIR, thermogravimetry (TG-DTA), and AAS. The materials were pow dered, sieved with 200-mesh, sterilized and implanted in surgically created holes (3mm diamet er) in the mandible of Beagle dogs. The implanted materials were covered with biodegradable membranes to prevent material loss during the experiment. After 2, 3, 4, 5, and 6 weeks, the dogs were sacrif iced under anesthesia. Histological stained sections of the mandible bones were observed using a microscope. Results XRD analysis confirmed the substitution of carbonate (CO 3) and fluoride (F) in the apatite structure based on shifts in diffraction peaks reflecting lattice paramete r changes due to CO 3-for-PO4 and Ffor-OH substitutions in calcium hydroxyapatite, Ca 10(PO4)6(OH)2. Carbonate substitution in CHA and in CFA was demonstrated as the absorbance bands at about 1400 to 1560 and at about 770 to 800 cm-1 in the FT-IR spectra 7 nd the weight losses above 400 C in TG-DTA. Histological sections of these materials showed a clear diffe renc in the extent of resorption or dissolution of the implanted apatites and in the pattern and type of bone f ormation. HAP remained Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 395-398 doi:10.4028/www.scientific.net/KEM.240-242.395

Thermal Stability of Mineralized and Demineralized Dentin: A Differential Scanning Calorimetric Study

The purpose of this study was to determine the difference, if any, in the thermal stability of collagen in mineralized and demineralized dentine compared to that in unmineralized tissues, using differential scanning calorimetry, DSC. Human tooth dentin blocks, about 1 x 1 x 2 mm in size, were used in this study. Some dentin blocks were demineralized using a Plank Rychlo solution; others, using EDTA solution. The mineralized dentin showed an exothermic peak at about 310 degrees C and the combustion of organic materials was completed at about 450 degrees C. For the demineralized dentin, the combustion was completed at higher temperature range and showed a strong exothermic peak at about 470 degrees C. An exotherm at the temperature between 450 degrees C and 470 degrees C was also observed in DSC pattern of native type I collagen from calf skin and rat tail tendon. DSC pattern of rat tail collagen showed a close similarity to that of the demineralized dentin. Statistically, the same heat flow value was obtained both from the mineralized dentin and the demineralized dentin and from the native type I collagen. These findings indicated that the thermal stability of collagen in dentin is lower than collagen in uncalcified connective tissue. It is suggested that in calcified collagen, the apatite crystallites may have intruded into spaces of the crosslinks of intra- and inter-fibrils, and in so doing, destroyed the crosslinks.

Apoptosis in regressive deciduous tooth germs of Suncusmurinus evaluated by the the TUNEL method and electron microscopy

Apoptosis in regressive primary (deciduous) dental primordia was examined in the embryos of Suncus murinus, which is a monophyodont. The primary tooth germs of S. murinus are temporarily formed and disappear during the embryonic period before they are calcified. Most primary tooth germs reach the bell stage and degenerate by embryonic day 22 (E22). Light microscopy on haematoxylin-eosin-stained sections revealed that intensely labelled granular substances are frequently present in the epithelial portion (enamel organs) of the deciduous tooth germs during the period from E18 to E20. The terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labelling method, computer-assisted three-dimensional reconstructions, and electron microscopy confirmed that these variable-sized granular substances are similar to apoptotic cells or bodies. Apoptotic structures were mainly found in the primary tooth germ located on the buccal surface of the secondary (successional) tooth germ. These results lead to the conclusion that apoptosis is closely associated with the involution and disappearance of the deciduous tooth germ in S. murinus. A primary tooth germ was observed on the buccal side of all the corresponding successional tooth germs, although the buccal surface of the secondary tooth germ of third upper molar teeth developed only to epithelial thickening without mesenchymal condensation. The findings, therefore, suggest that apoptosis is responsible for disappearance of the primary dental primordia during tooth development in S. murinus.

Pemphigus vulgaris involving the mouth and esophagus: Report of a case and review of the literature

A case of pemphigus vulgaris involving the mouth and esophagus is presented. Cases of pemphigus vulgaris involving the esophagus in the literature are reviewed; the initial symptom in all cases is in the oral cavity. Although the mortality rate for pemphigus vulgaris involving the esophagus is relatively high, the present case was managed successfully by active therapy with steroids.

Rhabdomyosarcoma of the left mandible

Abstract Rhabdomyosarcoma is a relatively uncommon tumor in the oral cavity. About 81 cases of intraoral rhabdomyosarcoma have been described in the literature since 1854.1–3 The authors recently encountered a case of embryonal rhabdomyosarcoma of the left mandible, which was diagnosed by means of electron microscopy and immunohistochemical techniques.

Origin and Evolution of Cementum as Tooth Attachment Complex

Abstract A general view of the origin and development of cementum is discussed. The evolutionary origin of the cementum is a lining bone tissue that ties the dermal bone to the dermal tooth in Ostradodermi (armored fish, Agnatha, cartilaginous vertebrate). The connective tissue around the dermal tooth forms it, and it is absorbed after connecting the tooth in tooth replacement. The odontoblast forming the dermal tooth loses its polarity, but the osteoblast which forms the lining bone remains multi-polar. Connective tissue forming the dermal tooth has further developed to form the pedicle and fibrous tissue connecting the teeth and jaw bones in fish and amphibians. In reptiles, teeth unite to the jaws with the pedicle bone, which is formed from the periodontal connective tissue. The formation aspect of the pedicle on the jaws differs from the dentine surface of the tooth root, because the pedicle is deposited on the jaw after absorption, but is directly deposited on the dentine. Some parts of the pedicle show as Sharpeys fibers but others are similar to the hyaline cartilage structures. It has been shown that the formation mechanisms have two polarities, like the human periodontal membrane, between the jaws and tooth root. Cementum is deposited not only on the surface of the root but also on the tooth crown as coronal cementum in mammals. When the coronal cementum develops, the enamel surface is absorbed by dental follicle tissue in horses etc., the enamel development is partially inhibited and forms a rugged surface in elephants etc., and enamel reduction is seen in Berardius (tooth whale). The ivory (lateral incisor) of the elephant and the tusk of the walrus ( Odobenus ) are covered in thick cementum; this is a root cellular cementum with rhythmic incremental lines, because the top of it has thin enamel.

Two Patterns of Calcification in Rat and Rabbit Incisor Dentin

The authors have reported previously that there are some differences of crystal orientation and calcification pattern between the enamel-covered labial and cementum-covered lingual dentin in rat incisors [1–2]. As in the rat, the incisors of the rabbit are continuously growing, and some reports have indicated that the dentin of incisors in both animals shows significant differences between the labial and lingual areas [3–6]. The purpose of this study was to investigate the structural differences between labial and lingual dentin of incisors from both rats and rabbits.

Functional characterization of calcium channels localized on the growth cones of cultured rat dorsal root ganglion cells.

Ca2+ channels on growth cones of cultured rat dorsal root ganglion (DRG) neurons were functionally characterized with an optical method using Fura-2. An increase in intracellular calcium concentration ([Ca2+](i)) of the growth cone was induced in response to electrical stimulation to the DRG cell body. The ([Ca2+](i))-increase was partly inhibited by either of omega - conotoxin GVIA (omega - CgTx, 3 microM) or omega - agatoxin IVA (omega - aga IVA, 300 nM) and completely blocked by both present at the same time, but was not affected by nicardipine (30 microM). The omega - CgTx - as well as omega - aga IVA - sensitive Ca2+ channels were immunologically localized on the growth cones using field emission scanning electron microscopy. It is concluded that the omega - CgTx - as well as omea - aga IVA - sensitive Ca2+ channels are involved in the ([Ca2+](i))-increase in the growth cones of the cultured DRG neurons, leading to glutamate release before synapse formation.