Abstract: A dental unit has a manifold module incorporating respective fluid-conducting conduits for the supply of water and air to dental instruments, each conduit leading to a respective self-sealing coupling member, said members forming a set located on one outer face of the manifold module for simultaneous releasable connection to a set of respective mating members on a manifold extension module. The manifold module may be corrected directly or via one or more manifold extension modules to one or more instrument control modules. Alternatively, the manifold extension modules and/or instrument control modules may be connected directly to a set of self-sealing coupling members located on a set of conduits supplying water and air.