Abstract: A dental operating unit is shown for use behind the head of a reclining patient's chair. There is a central, floor-mounted dentist's dynamic instrument service cabinet and an elongated counter top that is elevated above the service cabinet a short distance thereby leaving a gap between the cabinet and the counter top, and there is a pair of pivoted bracket arms located within the gap above the service cabinet and beneath the counter top. One pivot bracket arm has an anchor pivot that supports the bracket arms, while the free end of the second bracket arm is attached to a dental assistant's unit; whereby this dental assistant's unit is supported by a pair of swinging bracket arms which are capable of moving so that the dental assistant's unit may be reversible from either the left side or the right side of the patient's chair.