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According to the experimental results, the electrodeposition of copper on impressions should be carried out with a voltage-stabilized power supply at 0.3 V. This method permits the copperplating of tube impressions of various sizes without the need for further adjustments of controls on the plating apparatus.
The purpose of this series is to convey the principles governing our aesthetic senses. Usually meaning visual perception, aesthetics is not merely limited to the ocular apparatus. The concept of aesthetics encompasses both the time-arts such as music, theatre, literature and film, as well as space-arts such as paintings, sculpture and architecture.
The authors describe an illumination apparatus--"cold light" of their design which meets the demands of the most pretentious intensity of illumination in stomatochirurgical practice. They recommend the apparatus also for other medical disciplines.
A genesis of the large salivary glands is rare. Aetiology and pathogenesis of the non-formation of these glands is uncertain. On account of marked xerostomia this non-formation is of special significance for preventive dental measures.
Sterilization of metal instruments in Chemiclaves is undoubtedly the most protective mode of sterilization, because corrosion and formation of spots is minimal. In the past sterilization with Chemiclaves was criticised, because of the emission of formaldehyde by older models and the questionable efficacy of formaldehyde sterilization for wrapped instruments. In the present investigation the capability of the newest Chemiclaves (7000/8000) to sterilize dental instruments was investigated. To monitor sterilization efficacy filter paper strips loaded with spores of Bacillus stearothermophilus or dental instruments directly contaminated with these spores were used as biological indicators. The performance of the Chemiclaves was assessed with and without a full load of instruments; after running half of the program cycle, the spore strips in the chamber being either unpacked or packed into paper bags. In addition it was investigated, whether it was feasible to use a formaldehyde free sterilization solution (Steri-Vap) with these sterilizers. The daily performance of the Chemiclaves in a dental practice and the emission of formaldehyde were tested in a room < 10 m3, in which both apparatus were operated at the same time. The Chemiclaves 7000/8000 sterilized reliably under the set test condition, however, the formaldehyde-free sterilization solution did not lead to an acceptable efficacy of sterilization. The new Chemiclaves efficiently adsorbed formaldehyde vapours. Harvey sterilizers require a meticulous observation of the producer's instruction, because in comparison to saturated steam the chemical vapours have a lower heat capacity. The Chemiclaves 7000/8000 are recommended for the sterilization of well cleaned, dry instruments wrapped in original MDT paper bags.
The visco-elastic properties of a number of set elastomeric impression materials were determined using a torsional pendulum apparatus, i.e. the real (G1) and imaginary (G2) parts of the complex shear modulus and the mechanical loss tangent (Tan delta). Comparison with published data on tension and compression set for these materials showed that whilst there was no correlation between Tan delta and tension set, there was significant (greater than 99%) correlation with compression set. Treating a permanent set test as the application of a rectangular stress pulse of duration tau, and assuming (i) linear visco-elasticity theory and (ii) that G1 and G2 are independent of frequency. Fourier integral analysis predicts that Tan delta should be proportional to permanent set. Tension set does not conform to this prediction because the deformation is nonlinear. The compression set test is shown to involve shear strains and elastomers generally are Hookean in shear. Whilst the theoretical treatment applies qualitatively, there are major quantitative disparities, the reasons for which are discussed.
The disinfecting effect to the new preparation--desoxon-5 when decontaminating plastics, used in stomatology, plastic removable [correction of demountable] dentures and orthodontic, apparatus, infected by test microbes has been studied. One of the results of the work is the determination of desoxon-5 concentrations, causing the death of test microbes on the surface of plastic objects. It is proposed to include the use of desoxon-5 as an active decontaminating preparation into the number of means on looking after removable [correction of demountable] plastic dentures.
The purpose of this series is to convey the principles governing our aesthetic senses. Usually meaning visual perception, aesthetics is not merely limited to the ocular apparatus. The concept of aesthetics encompasses both the time-arts such as music, theatre, literature and film, as well as space-arts such as paintings, sculpture and architecture.
Fibers loaded with amoxycillin trihydrate were prepared for oro-dental infections using melt spinning technique. Ethylene vinyl acetate, a biocompatible polymer was used for providing controlled release effect over a period of several days. The fibers were evaluated for in vitro release in alkaline borate buffer pH 8.1 in a biological shaker which was rotated at 50 rpm at 37 degrees C. In situ studies were carried out in continuous flow through apparatus which simulated the conditions of periodontal pocket. Microbiological evaluation was carried out on strains commonly implicated in oro-dental infections namely S. aureus, S. mutans, and Bacteroides cereus. Results of in vitro release studies revealed that the effect was sustained over a period of 6 days and followed Fickian diffusion mechanism. In situ release study samples were well above the minimum inhibitory concentration of the drug. These samples were effective in inhibiting the growth of the above-mentioned strains. The optimized formulation was characterized for general appearance, content uniformity, and SEM. Stability studies carried out on the formulation showed the degradation rate constant value of 2.79 x 10(-4) per day. Retentive fibers were found to be very effective in controlled delivery of amoxycillin, and hence can be feasible alternative to systemic administration.
With the purpose of assessing the prevalence of dento-oro-facial parafunctions, an objective examination has been carried out of dental wear. At the same, a questionnaire on the parafunctional habits of a group of 108 patients suffering from cranio-mandibular disorders was distributed and a control sample of non-dysfunctional subjects of comparable age and sex features investigated. Data were collected by means of a special clinical record and an Individual Wear Index was worked out. The results showed a high presence of parafunctions in both groups, without significant differences. Dental wear was also comparable, showing, however, a precise age-proportional gradient. The facilitating structural causes, although confirming the decisive factor of muscular hyperactivity, were the loss of posterior support and deep bite. It was concluded that dysfunction and parafunction are not interdependent, although, evidently, they often coexist and are mutually aggravating.
Titanium, once considered to be difficult to cast because of its relatively high melting point (1670 +/- 50 degrees C) and strong chemical affinity, can now be acceptably cast using newly developed casting apparatus. The objectives of this study were to examine the castability of commercially pure (CP) titanium using an ultra high-speed centrifugal casting machine and a pressure difference-type casting unit and to compare the castability of titanium with that of conventional dental casting alloys. To determine castability, two types of patterns were used: a mesh pattern of 22 x 24 mm cut polyether thread sieve, and a saucer pattern (24 mm diameter) perforated to create four T-shaped ends. The casting equipment significantly affected the mold filling of both patterns (p < 0.001). The castability indices obtained from both patterns of CP titanium cast in the centrifugal casting machine were significantly (p < 0.05) better than the indices of the castings produced in the pressure-difference casting unit. The radiographs of the saucer pattern cast in the centrifugal casting machine showed some pores that were fewer and smaller in size than the pores found in castings made in the pressure-difference unit. When the ultra high-speed centrifugal casting machine was used with the manufacturer's recommended mold material, the castability of titanium was similar to that of gold alloy or Ni-Cr alloy cast by conventional means.
The objective of this study was to determine the pressures that caused cartridge failure (leakage or fracture) of six different dental local anaesthetics available in South Africa. Forty glass cartridges of each local anaesthetic were placed in an apparatus and subjected to pressure testing using two different plungers. Failure of the cartridges was observed visually as well as on the computer screen of the testing apparatus. In addition the compressibility of local anaesthetic rubber stoppers (bungs) was measured. The data obtained was analysed by means of a two-way analysis of variance and a chi-square test. The results from this study showed that there were statistically significant differences in the mean pressures that caused failure of local anaesthetic cartridges available on the South African market.
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