The push button is an essential component of a dental handpiece that controls the opening and closing of the rotor chuck (bur retention mechanism). When pressed, it releases the chuck’s grip to allow bur change.
Common push button failures and their risks
Mechanical damage
The most frequent cause of push button failure is mechanical damage, typically occurring when the turbine is dropped or struck. Impact often bends the outer ring of the button, causing it to stuck. Push button will stay in half pressed or pressed position. It may still partial function and still release the chuck but that can create a false impression that replacement can be postponed.
When this happens, the stuck button can rub against the rotor during operation. At high turbine speeds, this friction generates extreme heat, posing several risks of patient or turbine operator burns from contact and rotor damage due to excessive friction heat which leads to chuck system failure from prolonged heat stress.
Spring Failure
Inside every push button is a return spring that holds the button in the up position. Over time due to fatigue, exposure to chemicals and heat or excessive force, this spring can loses its tension or in rare cases even break, leaving the button floppy or in pressed position. This can again lead to friction and extreme heat, with risks of burns and chuck system failure from heat stress.
Contamination (debris & corrosion)
The button mechanism by design contains a cavity housing the spring, directly behind the bearing. This spring area is hard to clean thoroughly, making it a prime spot for aerosols and debris buildup inside the button mechanism, causing gritty and sticky movement or possible corrosion if the instrument is poorly maintained. Initial cleaning attempts like blowing out debris or spray oiling may resolve minor blockages.
A hard or incompressible push button may be caused by trapped debris of a failed bearing, such as broken cage pieces or loose balls, jamming and preventing the button from being pressed. If dislodging trapped fragments is unfeasible the button can be disassembled (if the button design allows for this) and cleaned by a professional, or in any case, it needs to be replaced.
The above picture also shows the worn central part of the button that maintains contact with the chuck mechanism. This wear results from stopping the rotor with the push button, this practice is not recommended. Over time, this causes button abrasion and excessive frictional heat, which can again lead to chuck failure. If the long-term abrasion of the push button’s center piece continues, it may eventually wear down completely, preventing the push button from releasing the chuck.
Check out our range of replacement turbine push buttons and contra-angle push buttons , or send your handpiece to us for inspection and repair if the issue requires more than basic repair.