the pure quartz core fiber 39 s characteristics are indicated by the solid line and the germanium doped quartz core fiber 39 s characteristics by the broke line as apparent from fig3 with respect to the light 0 2 to 0 3 u03bcm in wavelength which is in the range of wavelengths of bactericidal ultraviolet rays loss is much smaller with the pure quartz core fiber than the germanium doped quartz core fiber as shown in fig1 the hand piece 3 is connected to one end of light guide 2 and contains a light emitting means 4 at its opposite end the operator holds the hand piece 3 to control the areas of the root canal needing sterilization an operation that will be described in detail later fig2 illustrates hand piece 3 and light emitting means 4 in one embodiment in which hand piece 3 acts as a coupling means between light guide 2 and light emitting means 4 light emitting means 4 is detachably connected to the hand piece body 12 and includes an optical fiber 11 having a pure quartz core that is covered with a stainless steel fiber protecting pipe 18 that serves as a guiding means holder 14 slidably holds light emitting means 4 to hand piece body 12 the front end portion of the fiber protecting pipe 18 is bent at about 45 u00b0 and optical fiber 11 bends at a similar angle the bending angle of u03b8 of fiber protecting pipe 18 should be set to a value for easier insertion into a tooth to be sterilized this will depend on the position of the.