xi) Implantable medical devices and surgically invasive medical devices for long term use (a) Subject to clauses (b), (c) and (d), an implantable medical device or a surgically invasive medical device intended for long term use shall be assigned to Class C. (b) A long term use medical device shall be assigned to Class B, if it is intended to be placed into any tooth. (c) A long term use medical device shall be assigned to Class D, if it is intended, — (1) to be used in direct contact with the heart, the central circulatory system or the central nervous system;