A device for dispensing a dental material comprises a compartment for the dental material, a piston for extruding the dental material from the compartment, and a spindle drive for moving the piston and the compartment relative to one another. The first and second lens groups are disposed in order from the object side to the image side. There is provided at the downstream side end of the extension thin tube a back pressure valve 13 for uniformly increasing the pressure in the tube and for bringing the pressure close to the actual environment in the engine cylinder. A bump which is to be mechanically and electrically connected to the ground metallic layer is provided. A desired fiber optic end shape may be provided by the method, system and device described herein.