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High speed handpieces
Handpieces are the most frequently used device in restorative dentistry, but there can be a huge variation in quality, price, longevity and after-sales support depending on the supplier, brand and model of handpiece you choose. Good quality, well maintained handpieces can help your practice minimise unnecessary expenditure, and even prevent delayed appointments.
Dental handpiece types – air turbine versus electrical
There are two systems for powering handpieces: air turbine and electrical. Air driven handpieces contain an air-driven rotating turbine to generate rotation, and are powered by compressed air. They can reach speeds of up to 400,000 rpm or more with a variable torque. However, faster speed does not mean its better.
Electric motor handpieces use an electric motor to drive the head and can be considered self-contained systems. Internal gearings allow them to run at a constant torque (consistent power) with speeds of up to 200,000 rpm.
High speed handpieces
High speed handpieces (often referred to as ‘high speeds’) are used for rapid removal of enamel and tissue. They’re used to prepare cavities for restoration or crowns, remove tooth structure and create margins, and can cut through pretty much anything. They’re also used to section a tooth during surgery.
They’re one-piece units with a slight curve in appearance, and are much louder in use than slow speed handpieces. The head angulation can vary between handpieces. The only additional item used with high speeds is a bur: a rotary instrument with a friction grip (that works like a drill bit in a drill). We’ll come back to burs later.
Typically rotating at between 180,000 and 450,000 rpm, they incorporate water spray as a coolant due to the large amount of heat that they would otherwise produce. Cooling the tooth helps prevent overheating of the pulp. Water delivery can be ‘multi-port’ (three or four spray points) or a single port. A multi-port jet allows for a higher cutting rate.
Slow speed handpieces and attachments
Slow speed dental handpieces are used for removal of soft decay, finishing cavity preparation, polishing, trimming and prophy work. Referred to as ‘slow speeds’, they operate with an inbuilt motor at a typical speed of up to 80,000 rpm. They’re used with attachments that perform different functions:
Straight attachments connect to the motor base and are used for extraoral (out of the mouth) procedures such as trimming dentures
Contra-angle attachments (‘contra-angles’)use latch-type or friction grip burs. They can be used for intraoral or extraoral procedures to remove decay, polish amalgam restorations, refine cavity preparation, adjust crowns and bridges and adjust dentures. Burs vibrate less with contra-angle handpieces so they tend to be used for finer work
Prophylaxis angle attachments (‘prophy angles’) are used to hold a prophy cup and bristle brush as part of cleaning and polishing procedures. They can be made from disposable plastic or reusable metal.
Burs are the part that drills into the teeth – interchangeable, friction grip rotary instruments that are secured to the head of the handpiece using a lever chuck, push-button chuck or conventional chuck. The current standard is push-button systems that don’t require a tool for changing the bur.
There are a range of different burs of different shapes, sizes and materials, and they’re used for different purposes. Typically, they are constructed from diamond, steel or carbide.
Diamond burs tend to be used with high speed handpieces to grind away harder surfaces such as enamel. They have a relatively short lifespan.
Tungsten carbide is a hard material that’s much tougher than steel. Cuts in the head make them longer lasting and very effective as there’s little debris build up, and they stay sharp for a longer time than steel. They’re typically used to cut tooth structure rather than grind like diamond burs.
Steel burs are a low cost solution that are softer and more flexible than tungsten carbide burs. They blunt faster than carbide, but are more resistant to breaking.
The tip of the bur can be a wide variety of shapes: round burs and pear burs are used for cavity preparation and creating access points and undercuts. Cross-cut burs have cuts in the blade to prevent debris build up, and are used for sectioning and shaping teeth. Finishing burs are used for finishing restorations and shaping soft tissues.
Two numbering systems are used to help identify burs: the ISO system labels burs with a 15 digit code that identifies the bur type, shank type, length, head shape, grit (coarse versus fine) and maximum head diameter. The US system is normally used for carbide burs and is a one to four digit number.
Connectors (or ‘couplers’) attach the handpiece to the dental unit tubing to delivery water and air to the handpiece. The most common connections are Borden (two hole) and Midwest (four hole). A Bordon connection has one large hole to provide air allowing the turbine to spin, and a smaller hole for cooling water. A Midwest fitting (used more often in Europe and the US) has two large air holes to allow air in and out (exhaust), a cooling water hole, and a chip air hole (this directs air onto the cutting surface to help cool the tooth, disperse the water spray and clear debris). It’s possible to convert between two hole and four hole connectors.
Many manufacturers have their own uniquely designed couplers, so it’s important to ensure that you’re purchasing a handpiece with the right fitting.
Whilst the dentist will be using external lighting, many handpieces now come with an integrated light to help provide light intraorally. Typically, halogen or LED lights are used. LED lights are normally preferred due to their longer working life, more intense light and lower heat production.
A noisy handpiece can be off-putting to patients. Air handpieces are much louder than electric handpieces, due to the sound of the compressed air. In addition, electric handpieces generate less vibration than air turbines.
Manufacturers often differentiate their products through superior materials. Look for ceramic bearings (hard wearing), titanium bodies (stronger and more durable) and special ‘smart’ coatings for increased grip.
Specialist handpieces are available for surgical procedures.
Budget can be a big part of the purchase decision, but it shouldn’t be the deciding factor. It’s important to think about the lifetime value of the handpiece rather than the initial cost; handpiece repairs can be one of the biggest day to day costs of running a surgery.
Handpiece care and lubrication
It’s important to take care of your handpieces and there are a fantastic range of maintenance and sterilization equipment to help make it easier for you.