A dental assistant should never leave the operatory once a procedure begins. Your biggest costs are labor, lab and time. Why do you slow down to get up out of the operatory to go get something? Every single thing you need for every single procedure should be carried in the operatory in tubs or already be in every single operatory. Think Logistics! If it takes you 90 minutes to do a crown your overhead is usually 65%. If it takes you 45 minutes it is usually 50%. Labor, your collection policy (not your fee schedule), and the time spent doing each procedure are the largest cost drivers in dentistry.