Your dental staff general policy manual should contain policy of one week vacation after one year and up to two weeks after three years.
If staff members have two weeks of vacation I would make them take one of their vacation weeks at the same time the practice owner takes vacation.
That way you don't need to have more than one person manning the phones thus cutting down your overhead.
If dental patients for your state can get hygiene care without the doctor being present that could change.
Problems comes when you're paying, for example, a hygienist three weeks of vacation, and then you have to hire a temp at that time and having to pay them generally far more than the market value.
When you add holiday pay or paid time off (PTO) you'll see this becomes onerous especially for new doctors who inherit the situation from the previous practice.
Another thing to take into account is whether the staff are at the local averages for pay for their position. Quite often the staff just continually get raises every year which then puts staff pay percentage too high. This usually comes about because the previous dentist gave annual raises. And what ends up happening is the various staff members are getting paid far greater then the averages in their area because of this arbitrary pay raise every year.
If you're going to keep your staff pay percentages below 27% (below 25% is preferable) you have to rein in what the previous dentists was doing on raises, time off, etc.
As with any HR policies always check with your lawyer or a local HR professional to ensure your HR policies are complaint with state and federal regulations.