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A temperature-dependent, IR-controlled casting technology for the non-precious dental alloy Wiron 88 (Bego) is presented and compared with a traditional procedure. The new casting allows the production of cast objects with favourable and reproducible material properties. Compared with the commonly used technology hardness, grain size and susceptibility to corrosion could be reduced. Texture after casting was found to be homogeneous. The procedure presented meets the requirements for a modern casting technology and be adapted to older automatic casating devices.
Out of the great number of very important investigations on metal ceramics, only a small section can be represented. Those precious metal alloys which were developed for metal ceramics 25 years ago, were able to create and body confidence in the new ceramic proceedings of production for crowns and bridges. The number of failure caused by cracking and bursting was of a minor kind. The necessity of having cheaper alloys at one's disposal, e.g. gold-reduced alloys, palladium-alloys and non-precious metal alloys, involved that investigations for locating mistakes in the ceramics were carried through. Afterwards, changes of working methods had to be tested, in order to eliminate bubbles and cracks. The demonstrated results are designed to achieve better crowns and bridges. Allbountiful instructions are not possible, however, each alloy and each ceramic mass requires a special method of handling. If this happens, metal ceramics should continue to be a valuable clinically practicable method.
The results of the regular dental care of 192 mental and physical handicapped patients were analysed in a 5-year-period. The care system in which the prevention, the therapy in narcosis and the annual control are combined is very effective on a long-term basis. The handicapped patients had a lower prevalence of caries, a higher percentage of filled teeth and less extractions compared to a group of handicapped patients without continuous dental care.
50 patients suffering from tempero-mandibular dysfunction syndrome (TMS), 25 patients suffering from localized periodontal recessions, and 25 clinical healthy subjects were used for a clinical investigation. The oral hygiene index (Greene/Vermillion), the pocket depth, the size of periodontal recessions, the frequency of McCall-garlands, the frequency of Stillman-clefts, the frequency of wedge-shaped defects, the amount of occlusal wearing, and the clinical and anamnestic dysfunctions-index (Helkimo) were compared between the three different groups. No connection between the frequency and the size of any periodontal symptoms and the signs of TMS-dysfunctions could be found.
23% of a nonselected group of patients showed wedge shaped defects (9-10 of them per person). The number of teeth with these cervical erosions increases with age. Small accumulation of plaque was found. 65% of the patients with wedge shaped defects had parafunctions and 70% had a chronic pain. A complex of causes underlies the wedge shaped defects. A causal relation appears to exist between wedge shaped defects, occlusal disharmony, parafunctions and strong psychological tension of patients.
In principle it is possible to homogenize the enamel surface by melting structural elements with the continuous wave CO2 laser. An experimental caries model was used for testing the acid resistance of the laser exposed tooth surfaces. Laser-treatment and measured exposure to acid produced zones of homogeneous smelting with microcracks and disintegration symptoms. Underneath the melted region the heat leakage obviously causes photo-thermic++ effects determined by increased resistance to acid.
We tested a new diagnostic procedure for the characterization of subgingival plaque in 119 subjects suffering from adult periodontitis. The method can be characterized as a hydrolysis of BANA (N-benzoyl-DL-arginine-beta-naphthylamide) by peptidases of Porphyromonas gingivalis, Bacteroides forsythus and Treponema denticola. The result of a positive will be a more or less blue coloured test paper representing the amount of these three peridontal pathogens into the subgingival plaque. After the periodontal initial therapy the frequency of the positive colour reaction was significantly reduced. A correlation between the colour reaction and the clinical signs of periodontitis as well as the morphological characterization of subgingival plaque by darkfield microscopy could not been found. The new method for the characterization subgingival plaque seems to be useful for the judgement of a successful periodontal therapy at single sites.
The direct and indirect effect on the endodont after thermic treatment with the micro-plasma unit from EGIDE were examined in animal experiments. The EGIDE unit is considered by its producer to be an alternative for CO2 lasers. The histological evaluation showed that both the plasma-therapy of dentin and the exposed pulp lead to massive pathological changes of endodont and was inferior to traditional methods as the indirect pulpcapping.
It was proven that abrasion of artificial plastics teeth of different sizes (front and molar) of an usual-intrade assortment can be described with a common numeric value. The abrasion of Vitapan teeth is about 50% of that of IPN teeth. Isosit teeth are very little resistant against abrasion under the experimental conditions of this investigation.
On the basis of a literature survey there is a discussion about advantage and disadvantage of dental amalgam, possible alternatives and at least eventual dangers by intoxication of mercury. As result the amalgam were found without hesitation and classified as clinical suitable.
Tooth surface loss by erosion presents a challenge to the general practioner in terms of identification of patients at risk, diagnostic investigation and early therapy. The guidelines contain advice for changing the food habits and behaviour in oral hygiene. Patients, who prefer erosive products (fruits, juice, cola) or who vomit should use a bicarbonate mouthrinse to neutralize the acid. The spectrum of therapy reachs of simple fillings with glassionomer cements and composites to comprehensive crown therapy. Several particularities in the psychological care of patients with eating disorders are described.
Because of the excellent biocompatibility titanium can be considered as an ideal material for prosthetic reconstructions. Especially for base metal alloys titanium is an alternative due to the low cost. Processing still causes problems. In this paper a vacuum pressure casting system and a combination of milling and spark erosion are described and investigated. Both techniques are suitable to manufacture prosthetic restorations with a high accuracy of fit. Problems in dental castings lie in the occurrence of a superficial reaction zone of about 40-100 microns width. No final conclusions concerning the metal-ceramic compound can be drawn at the moment for lack of undisputable results in different mechanical bonding tests. Due to the remaining difficulties the future importance of titanium in prosthetic dentistry cannot be prognosticated.
A review from literature is given to problems of osseointegration of implants, to the biologic host defensive mechanism against plaque accumulation in the marginal region of osseointegrated implants as well as to problems of functional occlusal stress of such implants. Results of an investigation at IMZ-implants are integrated in the discussion: size of plaque accumulation, quality of subgingival plaque (dark field microscopy), bleeding on probing, pocket depth, correlation between these clinical signs.
The effects of a very short pulsed infrared mini-TEA-CO2-laserbeam at the wavelength of 10.6 microns on dentine were studied. The results of the light- and scanning electron microscopic investigation indicated the possibility of a precise removal of hard tooth structure without causing thermal damage of the tissue. Removing material by photoablation leads to a retentive surface on dentine and to a partially closure of the dentinetubuli at the bottom of the treated cavity. Undesirable thermal effects like surface-cracking and carbonisation were not observed.
The increasing morbidity of the psychosomatical eating disorders demands more attention by the general practioners. The origin of the anorexia nervosa and bulimia nervosa and the clinical picture are described. The consequences of the acid erosion at the teeth are shown with illustrations. The cooperation between the psychotherapist and the dentist has a positive influence on the long therapy of the patients.
Subgingival and irregular restoration margins have an unfavourable influence on the marginal periodont. The margins close to the gingiva of 206 restorations (age of restorations mean = 49.4 months) showed incorrectnesses in most cases with marginal inflammation as a result. That's why the demand of high precision, supragingival positioning of margin restoration and removal of all potential plaque-retentive or mechanic irritated surface is raised.
Resulting from clinical observation the relations between acute and chronical pulpitis and pulpitis chronica clausa, regressive metamorphoses and pulpal biomorphose are examined by histological findings and the literature. The etiological, nosological and pathohistological differentiation of this process is discussed. With the rising up of endodontological therapy needs into the middle and higher age the chronical inflammatorical and biomorphological events are more important. Proposals for diagnostics, differentiation and in the role wainting up instead of a early therapy are made.
The comparative measuring of the dust-seizure-efficiency of aspirators is being carried out by a practice-related treatment of 5 cylindrical-shaped specimen made of a commercial cobalt-chromium-alloy with aluminum-oxide-grinding instruments and silicone-rubber-polishers. A small-filter-apparatus takes up the person related samplings of the occurring total-dust-amount, which is then being calculated by a gravimetric standard-measuring-procedure. The cobalt-chromium-dust-fraction in the total dust amount is determined through an x-ray-fluorescence-analysis. Workplace dust-aspiration-equipment of the firms KaVo, Freuding and Wassermann have been subjected to testing. The values of the efficiency of all aspirators turned out to be below the American Threshold Limit Value TLV-TWA (Threshold Limit Value-Time Weighted Average) of 0.5 mg/m3 for chromium. The strict TLV-TWA-value of 0.05 mg/m3 for cobalt it also--with the exception of the Freuding-aspirator A 84 with aspiration-tube--not exceeded.
Whether fluoridation of drinking water would have an influence on orthodontic extraction therapy and especially on selection of extraction objects was inquired. Treatment results of 256 patients of a town with fluoridation of drinking water (Chemnitz) who had extraction of teeth under their orthodontic treatment, were interpreted and compared with these of a district without fluoridation of drinking water (Berlin). Evident differences concerning extraction frequency of the various species of teeth were noticed.
Recent epidemiological investigations about caries report about phenomenons like "caries increase" or "caries decline". This kind of observation bases on prevalence-studies. But describing such phenomenons does not give the opportunity to explain the observations. For that purpose the modern methodology of epidemiology should be used. Despite of the fact that epidemiology differs exactly between incident and prevalent cases, the use of incidence studies seems to be extremely seldom in stomatology. This paper discusses the problems, which occur in incidence-studies about caries and especially in cohort-studies. The authors show the difficulties to adopt terms like incidence density and cumulative incidence to studies about caries. A proposal is given in order to adopt the modern methodology of epidemiology to the special problem of caries.