The root of all evil

Remember the horrendous bilateral leg fracture experiment from last week? The senior author on that study is featured again this week! I think we should name this guy the Marquee du Sade of primate experimentation. This week he’s published an article about the interactive effects of tooth infection, root canal, bone healing and an experimental bone growth support treatment. They subjected 6 crab-eating macaques to dental hell for approximately one year.

Citation: Bergenholtz G, Wikesjo UM, Sorensen RG, Xiropaidis AV, Wozney JM. Observations on healing following endodontic surgery in nonhuman primates (Macaca fascicularis): effects of rhBMP-2. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2006 Jan; 101(1):116-25.

Summary of experiment: All monkeys were given tooth infections in their upper (4) and lower (4) incisors using a gruesome technique developed 25 years ago:

“The pulp tissue in each tooth included in the study was accessed, lacerated with endodontic files, and exposed to the oral environment for 1 week to induce a pulpal infection.”

A temporary filling was put in each tooth for 4 (upper teeth) or 7 (lower teeth) months. Bone lesions developed in 37/48 teeth. Several months after the temporary fillings were put in, they performed root canals for the infected teeth. Teeth on one side of the mouth were treated with the experimental agent. Dental exams and photos were taken pre- and post-surgery and at 1, 3 and 4.5 months post-surgery. Animals were euthanized for histopath.

There was some degree of healing over time – seen as early as one month after surgery.

“The findings corroborate previous observations on bone healing and cementum regeneration following endodontic surgery including a human biopsy material and experimental lesions in laboratory animals.”

However, there were complications. At 4.5 months post surgery, all animals had completely or partially necrotic pulp in the infected teeth. There were complications in 3 surgeries – which authors attributed to the difficulty of there being two root canals so close together on roots that were narrow and curved (not really very much like human teeth). At 1 month, x-rays revealed that 4 of the canals had been over-filled with root filling material – something that hadn’t been noticed in the post-surgery x-rays.

My Notes:

• Animals were anesthetized with telazol for X-rays and exams
• A prophylactic antibiotic injection was given within one hour of each surgery + 5 day treatment with broad spectrum antibiotics. (Given the necrosis and lesions, not enough to control infection.)
• Long-acting opiate pain killer (buprenorphine) was given for TWO DAYS after each surgery for pain control. AFTER you have holes drilled in 8 teeth with pulp laid bare? Or after 4 simultaneous root canals????? 2 days of pain medicine?
• Euthanasia by Phenobarbital overdose

The experimental agent didn’t have any effect on outcome, but they didn’t say it that way:

“In conclusion, from a clinical perspective this study does not generate support for the use of powerful biologic agents to enhance bone healing following endodontic surgery.”

Um, if there was no difference, the substance didn’t enhance healing and apparently wasn’t powerful.

Author affiliations:
Göteborg University, Göteborg, Sweden
Temple University School of Dentistry, Philadelphia, PaWyeth Research, Cambridge, Mass

No funding acknowledged