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At least 1,207 records · Page 67Linked to original sources
PubMed1980

The effects of cyclophosphamide, nitrosomethylurea and benzo(a)pyrene on the rat incisor.

Wistar rats given a single intraperitoneal injection of 75 mg cyclophosphamide revealed dental anomalies in the form of shortening or lengthening of incisors, and development of supernumerary teeth. Rats given additionally 5 mg/kg b. w. of a nitrosomethylurea solution over a period of four months showed the same dental anomalies, but with relatively shorter latency times. In a supplementary investigation examining the effects of benzo(a)pyrene and nitrosomethylurea applied locally to the organon dentale, neoplastic lesions and dental dysplasia were seen.

Animals↗
PubMed2002

Effect of Brn-3a deficiency on nociceptors and low-threshold mechanoreceptors in the trigeminal ganglion.

Immunohistochemistry for protein gene product 9.5 (PGP 9.5, a neuron specific protein) and vanilloid receptor 1-like receptor (VRL-1, a marker for medium-sized to large primary nociceptors) were used to assess the effects of Brn-3a deficiency on neuronal innervation of oral tissues and neurons of the trigeminal ganglion (TG). In the knockout mouse, the number of PGP 9.5-immunoreactive (-ir) nerve fibers decreased in the facial cutaneous and oral mucous epithelia, as well as the incisor and molar tooth germs. The reduction of PGP 9.5-ir Merkel endings was also observed in some vibrissae. No obvious change was detected in other tissues. Cell size analysis demonstrated that the proportion of small neurons markedly increased while that of medium-sized and large neurons significantly decreased in the TG of the mutant. Moreover, Brn-3a deficiency caused the disappearance of TG neurons which were immunoreactive for VRL-1. Together, our data suggest that nociceptors and low-threshold mechanoreceptors with medium-sized to large cell bodies may be sensitive to the loss of Brn-3a.

Afferent Pathways↗
PubMed1985

Cherubism.

Cherubism is a benign, hereditary giant cell lesion of the jaws, that appears in children as a bilateral painless swelling, between the ages of 2 and 5 years and progresses until puberty, when it spontaneously regresses. It normally requires no treatment. We had the chance to operate on a 5-year-old boy with cherubism 8 years ago, and used homogenous bone grafts to replace the diseased tissue to avoid pathological fracture of the mandible. Since then we have been following the patient, witnessing the gradual involvement of other sites in the jaws and the displacement of teeth and tooth germs.

Anodontia↗
PubMed1985

Autotransplantation of human premolars. A clinical and radiographic study of 100 teeth.

The purpose of the present study was to identify factors which might influence the success of autotransplantation, such as root development, root resorption, pulp condition and tooth eruption. The material consisted of 100 human premolars transplanted in 87 patients. The observation period ranged from 3-18 years, with a mean value 6.3 years. Clinical and radiographic examinations were performed. The transplanted premolars were divided into 7 stages of root development. At the final control, 93 teeth remained and 7 teeth were extracted. Periodontal healing without root resorption was related to stage of root development. It decreased from 93% in teeth with 3/4 root development to 37% in teeth with fully developed roots. Inflammatory root resorption was seen in 7 cases and replacement root resorption in 12 cases. Pulp revascularization was observed in 100% in stages with initial root development to 1/2 root development and decreased to 0% for teeth with fully developed roots. Pulp obliteration was observed in all cases with revascularized pulp tissue. The gingival condition was similar to contralateral, not transplanted premolars or adjacent teeth. Root growth increased with the stage of root development at the time of transplantation. It is concluded that transplantation of premolars with 1/2-3/4 root development provides a good chance of pulp survival, limited risk of root resorption and ensures sufficient final root length, and is thus recommended.

Adolescent↗
PubMed2000

Expression of 5-HT(2A), 5-HT(2B) and 5-HT(2C) receptors in the mouse embryo.

Expression patterns of 5-HT(2A), 5-HT(2B) and 5-HT(2C) receptors during mouse embryogenesis were investigated using highly specific monoclonal antibodies. Differential and overlapping spatio-temporal patterns of 5-HT(2A), 5-HT(2B) and 5-HT(2C) receptor immunoreactivity were observed during active phases of morphogenesis of a variety of embryonic tissues, including neuroepithelia of brain and spinal cord, notochord, somites, cranial neural crest, craniofacial mesenchyme and epithelia, heart myocardium and endocardial cushions, tooth germs, whisker follicles, cartilage and striated muscle. The functional significance of these receptors was tested by exposing headfold stage mouse embryos to different subtype-selective 5-HT(2) receptor antagonists for 2 days in whole embryo culture. The most potent was the pan 5-HT(2) receptor antagonist ritanserin, which has high affinity for the 5-HT(2B) receptor. Ritanserin caused 100% malformed embryos at a dose of 1 microM. The 5-HT(2A/2C) receptor antagonist mianserin also caused a significant number of malformed embryos, but only when used at a 10 fold higher dose (10 microM). Ketanserin, which primarily targets 5-HT(2A) receptors, did not cause a significant number of malformed embryos at any dose tested. Together with previous evidence that 5-HT acts as an important morphoregulatory signal during mouse embryogenesis, present evidence for the early and continued expression of functional 5-HT(2) receptors throughout gestation raises the possibility that psychotropic drugs taken during pregnancy could interfere with developmental actions of 5-HT during prenatal development of neural and non-neural tissues.

Adsorption↗
PubMed1998

Drill Free Screws: a new form of osteosynthesis screw.

Although the application of self-tapping and non self-tapping screws is virtually universal in cranio-maxillofacial surgery, the inevitable, time consuming procedure of drilling a pilot hole has some potential disadvantages, such as damage to nerves, tooth roots or tooth germs, thermal necrosis of the bone and drill bit breakage. Drill Free Screws (DFS) are a recently developed type of osteosynthesis screws, having a tip like a cork screw and specially formed cutting flutes which enable insertion of the screws without drilling. DFS 1.5 and 2 mm were inserted into discs of wood, polyvinylchloride (PVC) and porcine mandibular bone of varying thicknesses between 2 and 4 mm. The values of insertion torque and maximum torque were recorded using an electric torque tester. Thereafter, the screws were inserted with a fixed torque and uniaxial pull out tests were performed. In comparison with this, the same procedure was performed using 1.5 and 2 mm self-tapping titanium screws. Ten trials for each screw-material-combination were conducted to determine insertion torque, maximum torque and pull out analysis. The results showed that the holding power of DFS lay between 70 and 104% of the holding power of self-tapping titanium screws; only in PVC was the difference more than 15%.

Animals↗
PubMed1998

Solitary maxillary central incisor in the midline associated with systemic disorders.

A single maxillary central incisor in the midline is a rare developmental anomaly. The appearance of a single incisor in place of two teeth may occur as an isolated dental finding that can be related to fusion of two neighboring teeth or to agenesis of a tooth germ. However, the condition has also been reported to occur in association with autosomal dominant holoprosencephaly, growth retardation, and midline developmental defects. This article reports on other systemic defects that can be found in association with a single maxillary central incisor.

Anodontia↗
PubMed2003

Development of the dentition: four-dimensional visualization and open questions concerning the morphogenesis of tooth form and occlusion.

OBJECTIVES: The formation of the dental primordial should be visualized with special reference to characteristic differences for each single primordium. Until today, it has not been clear how traffic of the ameloblasts is controlled, how the folding pattern of the occlusal relief is generated or how the enamel production is terminated at the enamel surface. DESIGN: Using computer-aided reconstructions from histological serial sections, the dental primordial were visualized and, using fractured enamel specimens, the traces of each single ameloblast were followed by means of scanning electron microscopy. In this way, the developmental movements of the inner enamel epithelium can be reconstructed. RESULTS: Gathering morphological knowledge, three-dimensional polygon sets of shape data were input into a computer workstation and animated by means of the software Soft Image (Microsoft). CONCLUSIONS: The development of the human primary and permanent dentition was animated to simulate growth.

Ameloblasts↗
PubMed2000

Bovine dental papilla-derived cells immortalized with HPV 18 E6/E7.

In vitro investigations of cell-specific metabolism and cell interactions as well as biocompatibility studies are often hampered by the limited lifespan of primary cells originating from target tissues like the oral mucosa, gingiva or pulp. Pulp cells, as do other primary cells, undergo senescence after several passages in vitro. However, senescence can be overcome by transfection of primary cells with oncogenes like the HPV 18 (human papillomavirus 18) E6/E7 oncogene, resulting in immortalized cell lines. The purpose of our study was to establish and preliminary characterize an immortalized bovine dental papilla-derived cell line by transfection with HPV 18 E6/E7 for future use in biocompatibility testing of dental materials. First passage dental papilla-derived cells from molar tooth germs of 6-month-old calves were transfected by electroporation with pUC18 LCR E6/E7 coding for the HPV 18 E6/E7 oncogene. Cells underwent crisis after 5 wk in culture. Distinct cell colonies arose after about 9 wk. Cells were cloned by single cell dilution in passage 15 and 17. Out of three cell clones maintained in culture, two cell clones showed cell death after 28 and 30 wk, respectively. One cell clone overcame a second crisis after 38 wk and was maintained in culture until passage 75. Stable gene expression of HPV 18 E6/E7 oncogenes was verified by polymerase chain reaction (PCR) and immunohistochemistry. Reverse transcription (RT)-PCR revealed that the established cell line (passage 50) expresses procollagen type I, alkaline phosphatase and osteocalcin. This suggests that the immortalization with HPV 18 E6/E7 results in a cell line, which maintained phenotypic characteristics of odontoblast-like cells.

Alkaline Phosphatase↗
PubMed2002

Development of oxytalan fibers in the rat molar periodontal ligament.

Although oxytalan fibers are known to be a ubiquitous component of the periodontal ligament, little information has been available concerning their organization in the developing periodontal ligament. In the present study, growth and distribution of oxytalan fibers were examined in the developing periodontal ligament of rat molars aged 11, 14, 19, 21 and 28 days. A quantitative analysis of the fibers was made and the spatial relationship between the fibers and blood vessels was studied by means of a three-dimensional reconstruction of serial sections. At the beginning of root formation, oxytalan fibers appeared at first as dot-like structures around the root sheath as well as in areas very close to blood vessels. These structures were resolved in the electron microscope to be made up of 12-nm-wide microfibrils in the vicinity of the surface of the cells of the root sheath. In the process of development, these dot-like structures elongated into entities with helical appearances. As the development further proceeded, longer oxytalan fibers were produced in the apico-occlusal direction along with blood vessels. Quantitative analysis showed that an increase in oxytalan fibers coincided with an increase in the density of the vascular network in the developing periodontal ligament. Based on the results of the present study, the role of oxytalan fibers in the developing periodontal ligament may be in the maintenance of the integrity of the vascular system as previously suggested.

Age Factors↗
PubMed2001

Immediate repositioning of an accidentally extruded immature premolar after extracting root remnants of the primary molar.

This article describes a case where during an extraction of a primary molar's root remnant, the successor permanent tooth was accidentally extruded. The extruded tooth was immediately repositioned to its right position in the socket and it erupted normally after a short time. After 2 years, a routine clinical examination revealed normal appearance of the premolar in the dental arch. A radiograph demonstrated an obliterated coronal part of the pulp, normal root length, a slightly open apex and no periapical inflammation.

Bicuspid↗
PubMed1989

Calcification of the dental papilla. A rare finding.

An interesting case is reported, of calcification of the dental papilla. As yet, little is known about this asymptomatic calcification, which constitutes a rare radiographic finding, deforming the root of a vital tooth, generally a lower premolar or canine.

Adolescent↗