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At least 289 records · Page 16Linked to original sources
PubMedDate not supplied

[Changes in the biological and immunologic parameters in the oral cavity of the aged. Review].

Senescence is the effect of the immune system incapacity to see "self" and "non-self"; timo-involution induced down-regulation of immunoregulatory -T and B-lymphocytes. Immunosenescence mutations in oral cavity are examined. Even the oral ecosystem presents disorders in quality and quantity of the bacterial plaque and a different immune response. Age senescence is particularly evident in the masticatory apparatus, in fact the dental tissues have remarkable morpho-structural physiological changes; the epithelial, connective and osseous tissues of the periodontium have structural age changes related to the collagen synthesis and physical properties, with an increase of the stroma and a decrease of cell population. The osseous tissue presents cellular atrophy, sclerosis, osteoporosis and is undergoing a continuous structural remodelling; the oral mucous membranes show a thinning of epithelium and an increase of the stroma related to the parenchyma. Specific individual changes could be appraised in the involution of stomatognathic apparatus, more than an indefinite reduction of the performances.

Aged↗
PubMed1996

Influence of fluoride on secretory pathway of the secretory ameloblast in rat incisor tooth germs exposed to sodium fluoride.

Fluoride, which is an environmental toxicant, is a potent inducer of mottled enamel in humans and rats. To define the influence of fluoride on the secretory pathway in enamel fluorosis, mottled enamel was induced in the incisor tooth germs of rats by subcutaneous injections of sodium fluoride for 4 days, and then morphological and cytochemical changes of the secretory ameloblast were examined in the tooth germs with HRP-labeled lectin (Con A, GS-I, SBA and PNA) and En3 antibody labeling amelogenins. The accumulation of small vesicles on the route of the secretory pathway between the rER and the Golgi apparatus, disorder of Golgi stacks, and formation of abnormal large granules in distal cytoplasm were seen in the secretory ameloblast. Lectin staining patterns of the secretory ameloblast indicated the disturbance of the vesicular transport between the rER and the Golgi apparatus, and disorganization of the Golgi stack. Immunolabeling of the cell showed disruption of the sorting and fusion process on the secretory pathway. These results suggest that the fluoride disturbs the intracellular transport in the synthesis-secretory pathway of the ameloblast, and that this effect of fluoride on the synthesis-secretory pathway participates in the formation of enamel fluorosis.

Ameloblasts↗
PubMed1978

Dental x-ray spectrometry with an Si(Li) semiconductor.

Spectra from a dental x-ray apparatus with varying tube potentials and various added filters were measured with the use of an Si(Li) semiconductor. The mean energies of the spectra were calculated to estimate radiation qualities under various conditions. A phantom lip made of Arcylite was used to compare the attenuated quantities of radiation incident on the lip, according to the radiation quality, resulting from various tube potentials and added filtration.

Elementary Particles↗
PubMed1975

[Radiation protection in intra-oral dental radiography].

At the time being, all dental X-ray apparatuses in the German Democratic Republic are inspected step by step on the basis of the regulations in force. An essential objective of these measures consists in ensuring that the X-ray apparatuses used comply with the standards for radiation hygiene. In this regard, the present situation is still unsatisfactory. A considerable reduction of the radiation exposure to the patients and the operating personnel, however, may be achieved easily, using simple means. An example is the restriction of the useful beam, as to which practical advice is given. Furthermore, recommendations are presented for the proper operation and for the determination of the control area required by the radiological protection regulation.

Dentists↗
PubMedDate not supplied

[Intraoral panoramic radiography].

The paper presents techniques of dental filming and an apparatus for its performance, which has the following parameters, voltage, 55 kV; current, 0.1 mA; exposure, 1 sec.

Humans↗
PubMed1992

[The temporomandibular joint].

With its discordant articular surfaces and complete division in two cavities separated by a disk, the temporomandibular joint appears as a complex anatomical and functional entity. Combined movements involving anteroposterior gliding between the disk and temporal bone in the upper cavity, anteroposterior condyle translation, hinge and rotation movements between the disk and mandibular condyle contribute to the different movements of the jaw. With dental occlusion, the masticatory apparatus therefore includes five functionally coordinated articular compartments. Various impairments of the normal static and dynamic features of the temporomandibular joint may lead to relatively frequent pathological conditions which can be easily diagnosed by modern imaging and arthroscopic methods.

Diagnostic Imaging↗
PubMed1990

[A study of dynamics of orthodontic archwire on the dental arch. 1. Distribution of orthodontic forces during labial movement of bilateral incisors].

The study on labial movement of maxillary unilateral incisor had been reported previously. This study was the case of maxillary bilateral incisors. Orthodontic forces during labial movement of maxillary bilateral incisors which were produced by stainless steel archwire with vertical loops and nickel titanium archwire, were measured and were examined the distribution of orthodontic forces to the dental arch in the experimental apparatus with strain gauges. The following results were found: 1. In nickel titanium archwire, orthodontic forces were distributed to the entire dental arch, and the distribution of orthodontic forces could be classified into three types, which were similar to the previous study. 2. In stainless steel archwire with vertical loops, orthodontic forces were distributed only to bilateral incisors and adjacent tooth to bilateral incisors. 3. When bilateral incisors displaced lingually, it showed that there were additional orthodontic forces distributions as if two unilateral distributions were overlapped. 4. For maxillary bilateral incisors were moved in optimum force, some consideration to adjust the loops of stainless steel archwire was needed.

Dental Stress Analysis↗
PubMed1991

[Environmental problems in dentistry].

The materials used to treat dental patients endanger the environment. The most important polluting materials are the heavy metals, in particular mercury. The sulphides are of lesser importance and the other chemically active and infected materials are almost harmless. The gathering and discharging of most of these materials, preferably by own initiative, does not pose any problems. The removal of amalgam from the sewage however, requires a specific apparatus.

Dental Amalgam↗
PubMed1978

Effect of experimentally induced marginal periodontitis and periodontal scaling on the dental pulp.

Experimental breakdown of the periodontal attachment apparatus was produced in six young adult monkeys to study the effect on the tissue of the dental pulp by (1) periodontitis, (2) scaling and plaque accumulation on exposed root dentin. Periodontal tissue breakdown was induced by the placement of ligatures around the neck of 92 permanent teeth. Subsequent plaque formation caused marked loss of periodontal tissue support, which after a period of 5--7 months amounted to 30--40% of the root length. One group of teeth received no further treatment. Other teeth were subjected to scaling and root planing. Following treatment, plaque was allowed to accumulate for 2, 10, and 30 days on the freshly planed root dentin surfaces. Histologic examination revealed that in comparison to teeth with normal periodontal conditions, 57% of the teeth exposed to periodontitis exhibited pathologic pulp tissue alterations. Secondary dentin formation and/or inflammatory cell infiltrates were observed within localized areas of the pulp subjacent to root surfaces exposed to periodontal tissue destruction. The changes within the pulp were of "mild" nature and only one tooth displayed signs of total pulp necrosis. Lateral canals communicating with both the pulp cavity and the exposed root surface were never detected. Teeth subjected to scaling and subsequent plaque accumulation in comparison with teeth with periodontitis alone exhibited no obvious aggravation or increased incidence of pathologic pulp reactions. The findings show that in the monkey (1) periodontal destruction limited to the cervical half of the root and (2) plaque accumulation on exposed root dentin does not cause severe alteration in the pulp of the roots involved.

Animals↗
PubMed1981

The tensile creep characteristics of dental amalgam. I. Stress dependence.

Equipment is described which enables the determination of the creep behavior of small specimens of dental amalgam under tensile stresses. The apparatus has been used to measure the creep strain of both low and high copper dental amalgams at 34 degrees C, in the stress range 9.4 to 38.8 MNm(-2), for time periods of up to 24 h. Significant differences were found in the controlling creep mechanisms for the various amalgam types. Conventional amalgam displayed classical steady-state creep. The high copper amalgams, however, were best represented by transient creep equations implying interference to the motion of dislocations by the presence of hardening precipitates.

Dental Amalgam↗
PubMed2002

[Treatment using the Lehman apparatus in patients with malocclusion in light of teleradiologic tests and dental arch measurements].

The aim of this study was to assess the usefulness of Lehman's appliance for the management of distocclusion and to establish indications and contraindications to its use. The mean duration of treatment was also determined and compared to such in similar form of malocclusion treated with other types of functional appliances. Linear measurements were performed on dental plaster casts before and after treatment. Cephalometric analysis served to establish the mechanism of Class II correction (skeletal or dentoalveolar) and to reveal any increase in mandibular length caused by Lehman's appliance. The material consisted of thirty-three Class II patients (18 girls and 15 boys), aged 9 to 15 years, treated successfully with Lehman's appliance for distocclusion. Dental plaster casts and lateral cephalograms were obtained at the beginning and end of treatment. Improvement in occlusal relationship in the molar, canine and incisor segments was the result of dental and skeletal changes. Metric analysis of dental casts before and after treatment showed that active treatment was associated with an increase in transversal dimensions of the upper arch ranging from 1.8 to 2.4 mm. Overbite and overjet decreased considerably. Anterior length of upper arch was reduced significantly in boys only and was accompanied by distraction and transition from a V-shaped to U-shaped type of arch. These changes helped to harmonize transversal dental relationship of both arches and improved conditions for functional skeletal base adaptation. Treatment with Lehman's appliance improved the intermaxillary relationship and led to a decrease in the ANB angle attributable to a change in the SNA angle in girls and the SNB angle in boys. The mandibular reaction in girls with Class II/2 was interesting: the SNB angle increased considerably, indicating "unblocking" of the mandible. Changes in the vertical skeletal relationship were limited to a minor reduction in the index. Maxillary incisors moved little, but mandibular incisors showed significant proclination. The present findings demonstrate an additional increase in total mandibular length achieved with Lehman's appliance. This important effect contributed to a successful treatment of Class II malocclusion. Nevertheless, it should be remembered that this growth process depends on other factors, such as age, growth potential, growth pattern, and duration of appliance use. Average duration of treatment was 15 +/- 5.2 months in girls and 17.1 +/- 7.1 months in boys. In the case of girls, treatment in skeletal Class I was shorter than in skeletal Class II; the contrary was true in boys. Duration of treatment was shorter in patients with orthognathic type of face, irrespective of gender. Patients with deep vertical relationship showed a better prognosis in terms of duration and effects of treatment.

Adolescent↗