Engines having turbochargers with a mechanically actuated wastegate typically control the wastegate in response to the air pressure at an outlet of a compressor portion of the turbocharger. In such a single-lever mixing valve, increased hygiene and an improved visual impression are achieved in a simple construction by the pins being rotatably mounted about a rotation axis which is in alignment with the pivot axis of the actuating shank. It is shaped to conform to the teeth and maxillary and mandibular anatomy, and easily inserted by the user himherself. The 1\xd73 coupler may be constructed from a series of Y-branch couplers.