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At least 361 records · Page 20Linked to original sources
PubMed1989

Optical measurement of dental cast profile and application to analysis of three-dimensional tooth movement in orthodontics.

Dental casts are frequently used for measuring the size, shape and position of a tooth. We have developed an optical apparatus for measuring a three-dimensional profile of a dental cast. The measurement is based on the triangular method which detects a laser spot on a cast by an image sensor. The apparatus is computer-controlled and designed to achieve a total measuring depth of 40 mm, a data acquisition time of 25 ms per point and a minimum scanning pitch of 0.1 mm. The depth and lateral resolutions are 0.05 and 0.1 mm, respectively, within a depth range of 25 mm. As a particular application of the apparatus, three-dimensional movement of teeth, including rotational movement, during orthodontic treatment, has been quantified by means of the superimposition of tooth profiles using a computer.

Child↗
PubMedDate not supplied

[X-ray diagnostic apparatus in dentistry (a review)].

The X-ray dental equipment and photo-developing devices used for dentistry in Russia, the absorbed doses per tooth examination, and allied digital (sensory) transducers are considered.

Costs and Cost Analysis↗
PubMed2005

In vitro differentiation of human dental follicle cells with dexamethasone and insulin.

The dental follicle is an ectomesenchymally derived connective tissue harboring precursor cells for the tooth supporting apparatus. In this study, we examined gene expression of freshly isolated human dental follicle cells during osteogenic differentiation in vitro. These plastic adherent fibroblastic cells express Notch-1, nestin and vimentin. We differentiated dental follicle cells with dexamethasone or insulin-based protocols into membrane-like structures containing mineralizing foci. An analysis of mineralized tissue with atomic force microscopy illustrated a bone and cementum-like structure. A real-time RT-PCR analysis was developed to investigate expression of typical osteoblast or cementoblast related genes during differentiation. Gene expressions of osteocalcin (OCN), bone morphogenic protein (BMP)-2 and nestin were increased during the both differentiation approaches. Our work demonstrates differentiation of dental follicle cells with an insulin-based protocol for the first time.

Adult↗
PubMed1998

[Dental fluorosis of brick tea type in rats].

To observe the dental fluorosis of brick tea type, 48 white rats were fed by 245 mg.L-1 of brick tea, respectively. The rat model of brick tea type fluorosis were successfully established after 90 days. Naked eye examination of rats' incisors showed that brick tea and sodium fluoride (as positive control) groups all suffered from dental fluorosis. Using the dissecting microscope, the scanning electron microscope, and the energy spectrum apparatus, we also proved that the high concentration of brick tea could cause dental fluorosis.

Animals↗
PubMed1982

Forced eruption: principles in periodontics and restorative dentistry.

Forced orthodontic eruption is based on an understanding of the normal dental unit. The relationships between tooth, attachment apparatus, gingival unit, and force and stress demand consideration when forced eruption is used to treat carious or traumatic destruction of clinical crowns, lateral root perforations, or isolated vertical periodontal defects. Factors that must be judged acceptable prior to the initiation of therapy are (1) esthetics, (2) clinical root length, (3) root proximity, (4) root morphology, (5) furcation location, (6) individual tooth position, (7) collective tooth position, and (8) the ability to restore teeth. A correct diagnosis is essential and must precede the choice of forced eruption as a clinical solution. Correctly chosen, force eruption allows the tooth to assist in the support of a multiunit restoration or maintain its individual integrity while contributing to esthetics, speech, and function.

Dental Caries↗
PubMed1981

Dynamic mechanical properties of amalgams.

A recently developed dynamic mechanical analysis technique was utilized to determine the setting rates of dental amalgams. Via a compound parallel beam apparatus the dynamic mechanical properties of five amalgam materials were continuously measured at 37 degrees C within ca. 7 min after the start of trituration. Over a 15 hr period results showed that the modulus of elasticity (Ea) increased from 1.2 X 10(10) Pa to 6.5 X 10(10) Pa--the latter generally approaching those values reported via ultrasonic techniques. Moduli results via compression tests on microspecimens (3 X 2 X 1 mm) paralleled previous reliable literature data, nominally yielding values for Ea of 2-3 X 10(10) Pa. The extent of Ea scatter from both inter- and intrapreparer experiments appeared similar, although superior technique generally could be recognized by a systematic shift of the mean results to higher Ea's. In addition to modulus studies both compressive strengths (sigma max) and their corresponding strains (epsilon) were measured on microspecimens at a strain rate (epsilon) of 0.031 min-1, with a significant increase being noted in sigma max for the one material tested at over an order of magnitude increase in epsilon.

Dental Amalgam↗
PubMed1981

[Structural organization of the microcirculatory bed of the primordia of human deciduous teeth].

By means of injection and noninjection techniques structural organization of microcirculatory bed in the deciduous (milk) teeth germs have been studied in human fetuses, newborns and children. A definite dependence of the angioarchitectonics on the developmental stage of every tooth has been stated. Morphological differentiation of separate parts of the microcirculatory ways in the dental papilla is connected with dentinogenesis, and in the dental saccule--with amelogenesis, periodontum and alveolar wall formation. Those dental germ zones which have a peculiar functional importance (peripheral parts of the dental papilla, dental saccule in the area of the epithelial dental organ) are characterized by the presence of certain structural-functional apparatuses which provide increasing contact areas between blood and the tissues. Intraorganic circulatory bed of the dental papilla consists of identically constructed vascular complexes. The conformity coefficient between the arteriolar inlet and the venular outlet of the dental papilla microcirculatory ways during dentinogenesis is between 0.16--0.3. It has been stated that devices regulating the blood stream in the deciduous tooth germs (anastomoses, sphincters, arcades, etc.) are forming during the antenatal and early postnatal periods.

Amelogenesis↗
PubMed2005

Fine structural and cytochemical observations on the dental epithelial cells during cap enameloid formation stages in Polypterus senegalus, a bony fish (Actinopterygii).

Tooth germs during cap enameloid formation stages in Polypterus senegalus were investigated by transmission electron microscopy and enzyme histo- and cytochemistry. Enameloid formation was divided into three stages: matrix formation, mineralization, and maturation. The enamel organ consisted of the inner dental epithelial cells, stellate reticulum, and outer dental epithelial cells during cap enameloid formation stages, but no stratum intermedium was found. During the matrix formation stage, the tall inner dental epithelial cells contained well-developed Golgi apparatus, abundant cisternae of rough endoplasmic reticulum and mitochondria. Spindle-shaped vesicles containing a filamentous structure were seen in the distal cytoplasm. During mineralization and maturation stages, many ACPase positive lysosomes were present in the cytoplasm, whereas the organelles were decreased in number. The infoldings of the distal plasma membrane of the inner dental epithelial cells were visible in the mineralization stage but were not marked in the maturation stage. The activity of nonspecific ALPase, Ca-ATPase, and K-NPPase was detected at the plasma membrane of the inner dental epithelial cells during the stages of mineralization and maturation. The results of fine structure and enzyme cytochemistry suggested that the dental epithelial cells were mainly involved in the degeneration and removal of enameloid matrix and in material transportation during the enameloid mineralization and maturation stages, rather than in the enameloid matrix formation. The results also showed that the structure of the dental epithelial cells in Polypterus was different from that in teleosts and gars, but that the function of the dental epithelial cells was similar to that in teleosts possessing well-mineralized cap enameloid.

Animals↗
PubMedDate not supplied

[Correlation between occluding trauma and dental erosion].

The study presents data obtained by examination of a lot of patients with erosions of the teeth. At the same time histologic sections were prepared from teeth with cuneiform lesions that had to be removed as a result of parodonthopathic processes. Histological studies that have been carried out have demonstrated hyperemia of the dental pulp, and blood suffusion, sometimes accompanied by oedema. Slight rarefaction of dentine was also noted in other microscopic fields, with characteristic enlargement of the interdentinal spaces. The fact that the histological picture does not provide too much data on the etiopathogenic mechanism of the cuneiform lesions it may be considered that the occluding trauma is one of the major causes of these coronal lesions. Occluding balancing as performed by the authors in these patients have always demonstrated the presence of erosions in teeth that had suffered from occluding trauma. By this attitude and with these means of therapy one can prevent the development of new lesions of the cuneiform type, and thus contribute to the decrease in the morbidity, and to the prevention of the various disturbances in the dentomaxillary apparatus.

Dental Occlusion, Traumatic↗