If you do touch the bulb by mistake, gently clean it with cotton soaked in ethyl alcohol. Carefully insert the new bulb into the socket and remove the wrapper. CAUTION Never operate the dental light with the light shield removed. The shield is your protection against injury if the bulb shatters. Replace the light shield, and test the dental light to ensure it works properly. Notify the dental repair department to replace the spare light bulb you used, or if the light does not begin to function properly. Light Shield The light shield is constructed of hard plastic and is used to protect the dental light bulb and the reflector. Because  the  dental  light  is  close  to  the  patient treatment area, it is frequently soiled by splatter and aerosols. Use the following steps to clean the light shield: Ensure the light has cooled before cleaning the light  shield. Release  the  fastening  devices  on  the  dental  light to remove the light shield. Immerse the shield in warm, soapy water, rinse in clear water, and then wipe dry with a lint-free cloth. When the shield is clean, replace it on the dental light and test for proper operation. Light Reflector The light reflector is constructed of glass and is protected by the light shield. Use the following steps to clean the inside surface of the reflector when dust or spots reduce the efficiency of the light: Allow the light and reflector to cool before removing the light shield. Use a soft, lint-free cloth to gently remove any accumulated dust particles. Unplug   the   DDS   or   dental   light.   Use   a dampened cloth with water or a diluted solution of mild dishwashing soap for a more thorough cleaning. Ensure the cloth is not so wet that it drips into the electrical parts of the light. Wipe the inside surface of the reflector in one direction only. Ensure no residue remains on the reflector. Never use abrasives or chlorine on the surface of the reflector. Doing so can damage or discolor the  surface  of  the  reflector,  causing  poor lighting. Do not rub heavily or clean the reflector when it is hot. Never soak the reflector in cleaning solutions. After cleaning is completed, replace the light shield and test for proper operation. DENTAL HANDPIECES A dental handpiece is a precision-built mechanical device designed for use with rotary instruments, such as burs, stones, wheels, and discs, used in dental treatment. Handpieces may be air driven, electric, or compressed  gas  (for  surgical  handpieces).  Surgical handpieces  are  discussed  in  Dental  Technician, Volume 2, Chapter 5, “Oral Surgery Assistance.” Handpieces can be classified according to the revolutions per minute (rpm) or speed at which they operate. One type is the low- or slow-speed, and the other is referred to as the high-speed contra-angle. Both the low- and high-speed handpieces use an air system to operate several parts of the handpiece. The main function of the air is to rotate the air turbine or vane drive. Basically, this means the air system is the main power source for these handpieces. Fiber   optic   accessories   attached   to   dental handpieces allow the provider to operate handpieces with a light source and is discussed in this section. CONTRA-ANGLE HANDPIECES This   type   of   handpiece   is   used   in   cavity preparations to remove the bulk of enamel, dentin, and old  metal  restorations.  It  is  also  used  to  prepare retention grooves and bevels with a cavity preparation and to develop the cavity outline. The high-speed contra-angle handpieces (fig. 11-8) turn at a higher rate of  speed  than  the  slow-speed  handpieces.  Its  speed ranges from 380,000 to 400,000 rpm depending on the model. High-speed handpieces are operated by air pressure. The term contra-angle describes the angle at 11-12