Apparatus administers dental anesthetic to intraligamentary tissue with a drive unit and handpiece with injection needle connected by flexible tube to the unit. The drug is passes to the tissue at an instantaneous pressure at the needle tip that varies due to placement. A minimum threshold pressure is desired for administering the drug to the tissue. A practitioner moves the handpiece to insert the needle tip near the intraligamentary tissue and the instantaneous pressure is sensing or calculating. An auditory ascending signal indicates when the instantaneous pressure is rising, and when the instantaneous pressure reaches the threshold pressure a perceptible auditory specific signal indicates the practitioner has moved the tip into intraligamentary tissue. The tip is then maintained for supplying a selected dosage of the drug. Another auditory signal notifies the practitioner that the instantaneous pressure is declining or fluctuating before reaching the minimum threshold pressure.