Diamond instruments
Diamond instruments are usually rotary and rotationally symmetrical, sometimes oscillating, dental instruments almost always used in drive units (handpieces, contra-angles, turbines) in all areas of dental medicine and technology for widely varying purposes ranging from preparation and trimming conservative or prosthetic restorations to reducing proximal enamel during orthodontic treatment or surgical applications. Certain diamond instruments are for manual use only such as for roughening sites prepared for posts prior to adhering.
Diamond instruments are manufactured by embedding single or multiple layers of multi-surface natural or industrial diamond particles into a layer of bonder (often galvanically bonded or sintered to the metal blank). The edges of the particles abrade tissue and many types of material (mostly hard tooth structure such as enamel and dentine). Worn edges and particles breaking out of the bonder cause the instruments to become blunt. Sintered diamonds and silicone ("rubber") polishers are not only "coated" on the surface, the entire instrument is impregnated with diamond particles making them self-sharpening (but their original size and shape wear down). Colour-coded rings are used for classifying diamond instruments according to their abrasivity (depending on the particle size) ranging from extra-coarse (approx. 150 µm for reducing structure rapidly) to ultra-fine (approx. 15 µm for final finishing).
Diamond bur
When manufactured carefully (precise dimensioning of the instrument geometry, quality, sharpness/homogeneity of the particles, steel quality) diamond instruments run smoothly, perform efficiently and are long lasting.
The different shapes and sizes of diamond instruments can be designated numerically and uniformly acc. to DIN EN ISO 6360-1 (e.g. shank length/material, grit size, diameter of the working section).
Bud-shaped diamond bur
Different degrees of frictional force are generated depending on the pressure exerted, speed, diameter, grit size and traction of the drive unit. To prevent the undesirable effects of frictional heat in tissue (e.g. coagulation of proteins) or materials (e.g. cracked zirconia or melted acrylic), diamond instruments are often (a "must" when used intraorally) cooled continually with water. This ensures that dust particles can be flushed away simultaneously thus preventing the instrument clogging. Non-coated grooves, axial or spiralling around the instrument, have the same effect.
The integration of tungsten carbide blades, guide lugs, non-coated areas etc. allows certain structures to be protected against reduction or reduced even more.
Most diamond instruments are autoclavable and for multiple usage. Sterile, disposable diamond instruments are increasingly in use for clinical purposes.
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elongation at rupture | Bruchdehnung |
Wax build-up technique Wax build-up technique The various anatomical structures (such as cusp tips and slopes as well as marginal ridges) are usually built up one after another by adding small portions of wax (often using differently coloured waxes for didactic purposes). The firm, special waxes first have to be melted at room temperature. This can be carried out by warming small portions on differently shaped working tips of hand instruments in an open flame (such as a gas burner) or using electrically heated instruments which provide for more accurate temperature control and avoid contamination (e.g. electric wax-knife, induction heaters, wax dipping units). The wax is applied drop-by-drop to ensure that the warmer molten wax added last fuses seamlessly with the firm, cooler material. After hardening, the wax pattern can be reduced by sculpting, milling guidance surfaces or drilling to add retainers. Modern procedures include flexible, occlusal preforms for adding contours to soft wax. In addition, wax preforms, such as for occlusal surfaces or bridge pontics, are available in various shapes and sizes. Recently, irreversible, light-curing materials have been introduced for use instead of reversible thermoplastic waxes. Wax preforms To ensure that the wax pattern can be released without being damaged, model surfaces, opposing dentition and preparations must be hardened/sealed with special lacquer (applied by spraying, brushing or dipping). These waxes are mostly relatively rigid/elastic after cooling. Attaching wax sprues to a removable framework supported on double crowns using a hand instrument When employing the lost wax technique, prefabricated wax sprues, bars and reservoirs are attached to the patterns. Once the pattern has been released and its sprues waxed onto the crucible former, it is invested in a casting ring with refractory investment material. The wax can then be burnt out residue-free and casting completed. Unlike standard wax build-up techniques, a diagnostic wax-up is not intended for fabricating an indirect restoration, but rather for simulating the appearance and/or external contouring for producing orientation templates. |