A dental chair is medical equipment hardwired to power, water, air, and suction. Disconnecting it wrong damages a very expensive unit, so this is a job for dental equipment specialists in most cases.
Pro tip: Keep the equipment serial numbers and a full photo set of connections for the technician who recommissions it.
Watch out: Do not disconnect a hardwired dental chair yourself; water, air, and electrical lines require proper capping to avoid damage and hazards.