PubMed · 6583929
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
W M Schmitt. 1983. [Biotechnical preparation system using a surface carver].. https://pubmed.ncbi.nlm.nih.gov/6583929/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
OBJECT: Previous work [Jones CS. Factors influencing the finishing of direct filling materials. PhD Thesis, University of London; 2002] has shown that there is an optimum load, speed and time that produced the smoothest surface when finishing glass-ionomer cement using each of four grades of a disc system. This study looks at the effects of lubrication on the temperature produced in samples of GIC when finished dry and with different lubricants using these optimal loads, speeds and times. It also compares the surface finish produced using different lubricants. MATERIALS AND METHODS: A thermocouple connected so that it permitted the display and recording of temperature against time was inserted 1mm into the base of samples of a glass-ionomer cement. The samples were finished and polished using each of the grades of a disc system in a specially constructed jig that mimicked oral finishing. After roughening, the pre-determined optimum loads, speeds and times were used sequentially for each of the four grades of disc. Five samples were tested for each method of finishing. Firstly run dry, then in turn lubricated with water, walnut oil and petroleum jelly. After the use of each abrasive disc the surface roughness was measured using a profilometer. One of the five samples was selected at random and prepared for examination in the scanning electron microscope. All results were subjected to non-parametric statistically analyses. RESULTS: Walnut oil and petroleum jelly produced significant temperature increases compared to both dry and with water finishing. Lubricated with water significantly reduced the temperature rise compared to dry. The Ra values of 0.5 microm was obtained for the coarse and a value of 0.3 microm for the medium discs run without lubrication. With lubrication the Ra increased although there was little difference between the lubricants. However the photomicrographs showed that walnut oil and petroleum jelly caused gross morphological changes indicating major surface destruction. CONCLUSIONS: The practice of finishing GICs using petroleum jelly or similar lubricant appears to be detrimental. Further experimental work needs to be done to advise practitioners on finishing GICs to produce the smoothest surface possible.
OBJECTIVES: To investigate claims that Duceram low-fusing ceramic (Duceram-LFC), a 'hydrothermal' dental veneer will increase in strength after hydrolytic testing and surface polishing.Methods. Using pre-determined powder/liquid slurry constituents, nominally identical Duceram-LFC disc-shaped specimens were fabricated to obtain mean bi-axial flexure strengths, standard deviations, Weibull modulus (m) and Vickers hardness. Thirty specimens were tested 'dry' (control), after 24 and 48h immersion in a water bath maintained at 37+/-1 degrees C and a further 30 samples polished to a 6 micrometer nap finish. RESULTS: Mean bi-axial flexure strengths of specimens tested dry were found to be 67.04+/-13.87MPa (m=7.23+/-1.32) compared with 61.01+/-15.23MPa (m=4.29+/-0.78) and 68.42+/-23.36MPa (m=3.29+/-0.60) for 24 and 48h immersion, respectively. Following surface polishing, the bi-axial flexure strength was 95.91+/-22.4MPa (m=4.37+/-0.8). Vickers hardness numbers showed no significant difference between the dry control group and after 24 and 48h immersion (P>0.05). SIGNIFICANCE: Results obtained do not support claims for surface flaw and/or defect healing through the formation of an SiOH layer at the surface of Duceram-LFC specimens over time. However, the polishing regime interrupted the defect population associated with flaws present in dry (control) samples of Duceram-LFC which can be attributed to an associated reduction of initial surface flaws and/or defects.
This study investigated the effects of reconditioning on the slot dimensions and the static frictional resistance of stainless steel brackets at 0, 5, and 10 degrees bracket/archwire angulation. A sample of 45 used, commercially reconditioned 0.018 x 0.030 inch stainless steel standard edgewise brackets was compared with a matched sample of 45 new brackets. The slot dimensions of 15 new and 15 reconditioned brackets were examined using a photomicroscope. With new brackets both the occluso-gingival slot width (mean = 0.0197 inch) and slot depth (mean = 0.0304 inch) exceeded the manufacturer's nominal dimensions of 0.018 x 0.030 inch. The reconditioning process resulted in a further increase in slot width (mean = 0.0205 inch), which was statistically significant (P = 0.028), and a reduction in slot depth (mean = 0.0291 inch), which was highly statistically significant (P = 0.002). This may be attributable to preferential metal removal by the electro-polishing phase of the reconditioning process. Friction testing of 30 new and 30 reconditioned brackets demonstrated that both showed an increase in binding effects as the bracket/archwire angulation was increased from 0 to 5-10 degrees. However, the changes in slot dimensions secondary to reconditioning did not result in a statistically significant difference in mean static frictional resistance when the two bracket types were compared. Although the brackets were altered physically by the reconditioning process, their performance during simulated sliding mechanics was not adversely affected. This implies that reconditioning may not result in clinically significant effects.