In a lip type seal, a case is tightly fitted and fixed to an inner circumferential surface of a housing through a gasket. A dental implant can include a body portion, extending from a proximal end to a distal end along a longitudinal axis, including a central bore extending from the proximal end to a termination point, located proximal of the distal end. The lower link is rotatably mounted on a crankpin of a crankshaft and connected to the upper link by an upper pin.