![]() Reduce back suction pollution, wipe with dressing, remove sticky dirt and dental materials on the surface of the dental handpiece in time Protective equipment: protective clothing, goggles, or face shieldsĪfter using the dental handpiece with a bur, step on the foot brake in time to flush the handpiece lumen for the 30s, as shown in Figure D.1 Various cleaning tools: soft brush, sponge, high-pressure water (air) gunģ. Cleaners and Disinfectants: Multi-enzyme solutionĢ. There may be significant fluctuations in air pressure due to the various demands on the compressor due to demand from other clinics in a multi-clinic practice.1. ![]() The air pressure should be set at 2–3 bar (29–43.5 psi) and should be confirmed using an air gauge. This will have an effect on the speed of the bur and hence the torque. Power is difficult to maintain with an air supply as the air pressure is not supplied at a constant level and may fluctuate depending on the draw down of air from the compressor. The relationship of power, torque and speed are illustrated in Figure 19.9. ![]() To allow the bur to continue to rotate, the power must be maintained. The optimum cutting speed is approximately one half of the free running speed. As the bur is applied to the tooth the bur slows to a cutting speed of between 180 000 and 200 000 rpm. The free running speed of a turbine is in the order of 300 000–400 000 revolutions per minute (rpm). This is the ability of the bur to continue to rotate and therefore cut when pressure (approximately 70 g) is applied to the substrate. One of the critical properties for any dental handpiece is torque (along with concentricity and noise). Stainless steel is also used for handpiece manufacture and lies between these two materials with respect to weight. Brass is commonly used to construct handpieces but will make the instrument heavier. Materials such as peek (a fibre-reinforced composite material) are being used by some manufacturers to construct the internal components of the handpiece so reducing the handpiece’s weight. The materials used to manufacture the instrument influence the weight of the instrument. A heavier handpiece will lead to operator fatigue more quickly than a lighter one. It is largely the clinician’s preference whether a heavy or lighter handpiece is selected. When the handpiece is held in the working position the balance should be neutral or slightly toward the handpiece head. Other factors such as the type of the tubing housing, the services (air, water and electrical cabling) to the coupling and how it is arranged on the dental unit will also contribute to the balance of the handpiece. The rapidly developing LED technology may well see considerable advances in product design and usage featuring these components in future.Ī badly balanced handpiece will compromise the accuracy of the dentist’s work and increase operator fatigue. LEDs are also relatively stable in wavelength over their lifetime and low-power LEDs produce little or no heat. The resulting light is whiter, more intense and the working life is much longer. Many manufacturers have now moved onto using low-power light emitting diodes ( LEDs). Furthermore, the glass fibreoptic rod was prone to breakage if the handpiece was dropped, and deteriorated with time due to repeated decontamination cycles in the autoclave. Halogen bulbs deteriorate with time in use and have relatively a short life. ![]() The original lights were small halogen bulbs, with the light being transmitted to the handpiece head using a fibreoptic rod. This is directed at the cutting surface so that the area being worked on is illuminated directly rather by reflection via a mouth mirror, increasing the dentist’s clarity of vision. Many modern handpieces now have a light in close proximity to the bur. There has been a move in recent years towards ceramic ball bearings, primarily because ceramic, is a harder material than stainless steel and wears less. These ball bearings are made of either stainless steel or a ceramic material. The race holds the shank of the bur, allowing it to rotate smoothly along a central axis with minimal friction. The ball bearings are surrounded by a phenolic resin that lubricates their movement in the same way as oil lubricates the moving parts of a car engine. Inside the bearing housing are seven or eight ball bearings, which run freely inside a cage called a ball race. Less control for the dentist due to the irregular cutting.This will result in irregular removal of the tissue being prepared so more tissue is removed than is necessary. It can cause the bur to break as it may snatch against the cutting surface. This vibration may also be unpleasant for the patient. This leads to vibration that is then transmitted to the material being cut, causing cracking and crazing.
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