(x-rays, local anesthesia, sedation and more)
Both x-rays and novocaine (and other drugs used for local anesthesia, such as bupivacaine and lidocaine) are considered to be compatible with breastfeeding.
Most medications used for oral and IV sedation are considered compatible with breastfeeding.
Nitrous oxide (laughing gas) sedation is also considered to be compatible with breastfeeding. It is virtually insoluble in the bloodstream, which means it goes from your brain to your lungs to the room air immediately after you stop breathing it in. Per Hale, “it is rapidly eliminated from the body due to rapid exchange with nitrogen via the pulmonary alveoli (within minutes). A rapid recovery generally occurs within 3-5 minutes… Ingestion of nitrous oxide orally via milk is unlikely.” See Conscious Sedation for more information.
.
A mother who has wisdom tooth surgery should not need to interrupt breastfeeding at all (except during the surgery, of course). To minimize baby’s exposure (and increase mom’s comfort), mom can nurse just before she goes in for the procedure. There is no need to wait on breastfeeding afterwards or to pump and dump — mom can nurse as soon as she feels alert enough to hold baby. See Breastfeeding when mom has surgery for more information on breastfeeding and general anesthesia.
There are many pain medications compatible with breastfeeding. See How do I determine if a medication is safe for a breastfeeding mother? for more information.
Additional information
@ 
- Conscious Sedation and Breastfeeding: Recommendations for Patients by Maurenne Griese, RNC, BSN
- Anesthetic medications and breastfeeding
- Breastfeeding when mom has surgery
@ other websites
- Drug distribution in human milk: Dental Implications by Dr R.G. Woods of the Australian Dental Association, from Australian Prescriber 1997;20(2);51. This article refers to the article Drug distribution in human milk by K. F. Ilett, J. H. Kristensen, R. E. Wojnar-Horton & E. J. Begg, from Australian Prescriber 1997;20(2);35-40.
Research
Giuliani M, Grossi GB, Pileri M, Lajolo C, Casparrini G. Could local anesthesia while breast-feeding be harmful to infants? J Pediatr Gastroenterol Nutr 2001 Feb;32(2):142-4. Conclusion: “This study suggests that even if a nursing mother undergoes dental treatment with local anesthesia using lidocaine without adrenaline, she can safely continue breastfeeding.”
Ortega D, Viviand X, Lorec AM, Gamerre M, Martin C, Bruguerolle B. Excretion of lidocaine and bupivacaine in breast milk following epidural anesthesia for cesarean delivery. Acta Anaesthesiol Scand 1999 Apr;43(4):394-7. Conclusion: “This study documents the magnitude of excreted lidocaine, bupivacaine and PPX in breast milk, and indicates that the use of both lidocaine and bupivacaine for epidural anaesthesia is safe with regard to breast-feeding.”
Lebedevs TH, Wojnar-Horton RE, Yapp P, Roberts MJ, Dusci LJ, Hackett LP, Ilett K. Excretion of lignocaine and its metabolite monoethylglycinexylidide in breast milk following its use in a dental procedure. A case report. J Clin Periodontol 1993 Sep;20(8):606-8. “Nursing mothers receiving lignocaine for standard dental procedures can be advised that continuation