Before you try to get pregnant is the best time to see the dentist, because then x-rays can be obtained and if extensive dental work is required there are less limitations than during pregnancy.
It is critical to maintain good oral hygeine during pregnancy. Dental disease, poor oral hygeine, and gingivitis are risk factors for preterm labor and preterm delivery because of the bacteria that are present and circulating in dental disease states. This is an easy intervention and investment in future pregnancy.
If you are already pregnant and have not visited the dentist, do so now! You can have a cleaning at any time in pregnancy. You can have cavities filled and novocaine can be used (we tell the dentist to try to avoid using epinephrine).
You also should not have nitrous oxide (laughing gas) during pregnancy. Local anesthetics can be safely used, as can oral narcotic pain medication such as darvocet, percoset, and codeine, if extensive work is done, and significant postoperative pain is anticipated.
Make sure your dentist calls your Ob/gyn to check the safety of any medications, pain relievers or antibiotics used in pregnancy.