A dental receptionist (or any staff member for that matter) should never try to wing it when it comes to answering patient’s dental questions.
Your receptionist should only answer those questions she knows the answer to without diagnosing or giving out medical advice.
If the receptionist does not know the answer or it is beyond her scope of responsibility she should simply say something to the effect of, “Mr. Jones, that is something I will have to check with the doctor on (or office manager or whoever). I will get back to you by the end of the day or first thing tomorrow with the information.”
Over time she will know that some questions cannot be answered over the phone and simply inform the patient they will need to come in.