Dr. Beckman's International Veterinary Dentistry Institute offers courses in all areas of vet dentistry.    Online & Live Courses for Vets and Techs https://veterinarydentistry.net/    To request an invitation to the VDP Program: https://ivdi.org/    Complications of Extractions or Oro-Nasal Fistula (ONF) Closure After Radiation in Humans and Dogs Introduction  Radiation therapy is a common treatment modality for certain cancers affecting the oral cavity in both humans and dogs. While effective for managing malignancies, radiation can lead to significant challenges in dental procedures, particularly tooth extractions and oro-nasal fistula (ONF) closures. This evaluation synthesizes literature discussing complications associated with these procedures in both species, highlighting parallels and species-specific differences.   Human Literature

1. Osteoradionecrosis (ORN) 
   • Pathophysiology: ORN is a major complication following extractions in irradiated fields. Radiation induces hypovascularity, hypocellularity, and fibrosis in the bone, reducing its ability to heal and resist infection.
   • Incidence: Studies report ORN rates between 5% and 15% after dental extractions in irradiated patients.
   • Risk Factors:
     • Total radiation dose exceeding 60 Gy.
     • Location: Mandible is more prone due to poorer vascular supply.
     • Timing: Extractions performed within 6 months post-radiation have higher risks.
     • Comorbidities: Diabetes, smoking, and poor oral hygiene exacerbate risks.
   • Management:
     • Prophylactic measures include hyperbaric oxygen therapy (HBOT).
     • Surgical debridement or segmental resection may be necessary for severe ORN.
2.  Soft Tissue Complications
   • Delayed Healing: Radiation-induced fibrosis and reduced vascularity lead to delayed mucosal healing.
   • Infections: Secondary infections, such as osteomyelitis, are common due to impaired immune response and reduced tissue integrity.
   • Dehiscence: Closure of oro-nasal fistulas is often complicated by wound dehiscence due to tension at the suture site and poor healing capacity.
3. ONF Closure
   • Challenges:
     • High recurrence rates due to radiation-induced tissue fragility.
     • Limited availability of local tissue for flap reconstruction.
   • Surgical Options:
     • Use of pedicled flaps, such as buccal or palatal flaps, has been successful.
     • Free tissue transfers (e.g., radial forearm free flap) are utilized for extensive defects.
     • Tissue engineering with growth factors or stem cells is an emerging area of interest.
   • Pre-Surgical Preparation:
     • Hyperbaric Oxygen Therapy (HBOT): While not universally applied, HBOT is frequently recommended before surgical interventions in patients at high risk for ORN. Protocols often involve 20-30 preoperative dives (2.0-2.5 ATA for 90-120 minutes per session) and 10 postoperative dives.
     • Antibiotics: Broad-spectrum antibiotics may be prescribed prophylactically to reduce the risk of infection.
     • Nutritional Optimization: Ensuring the patient’s nutritional status is optimized can improve surgical outcomes.

Veterinary Literature (Dogs)

1. Osteoradionecrosis (ORN) 
   • Pathophysiology: Similar to humans, radiation in dogs leads to hypovascularity and reduced bone turnover. The mandible is the most commonly affected site.
   • Incidence: Published reports indicate a lower incidence of ORN in dogs compared to humans, possibly due to differences in fractionation protocols and total radiation doses.
   • Risk Factors:
     • Total radiation dose (commonly > 50 Gy).
     • Larger tumor burden and proximity to the bone.
   • Management:
     • Conservative treatment includes antibiotics and analgesics.
     • Surgical intervention involves debridement or mandibulectomy in severe cases.
2. Soft Tissue Complications
   • Delayed Healing: Radiation reduces epithelial turnover and fibroblast activity, delaying healing of mucosal wounds.
   • Fistula Formation: ONF formation is common after radiation and can be exacerbated by dental extractions, particularly in the caudal maxillary region.
3. ONF Closure
   • Challenges:
     • Dogs often have limited tissue for local flap reconstruction.
     • Radiation reduces the availability and viability of tissue for surgical manipulation.
   • Surgical Options:
     • Buccal mucosal advancement flaps and rotation flaps are commonly used.
     • Palatal flaps are an alternative for larger defects.
     • Advanced techniques, such as axial pattern flaps, have shown promise.
   • Adjunctive Therapies: HBOT has been explored in veterinary medicine with anecdotal success, though systematic studies are limited.  

Comparative Analysis Common Complications

• Delayed Healing: Both species exhibit delayed healing due to radiation-induced vascular and cellular changes.
• ORN: A significant risk in humans and dogs, although reported incidences and management strategies differ.
• Wound Dehiscence: Tissue fragility and tension at surgical sites are common across species.

 

Species-Specific Differences

• • Risk Factors:
    • Humans are more affected by lifestyle factors such as smoking and systemic conditions like diabetes.
    • Dogs are less influenced by these factors but may have different radiation fractionation protocols affecting outcomes.
  • Management:
    • Free flap techniques and tissue engineering are more advanced in human medicine.
    • Veterinary approaches often rely on local flaps and less invasive options due to cost and availability constraints.  

Hyperbaric Oxygen Therapy (HBOT) Protocol Human Protocol  Hyperbaric oxygen therapy (HBOT) is commonly recommended presurgically for patients who have undergone radiation therapy, especially in the head and neck region, to reduce the risk of complications such as osteoradionecrosis (ORN) after oral surgery.  

Typical HBOT Protocol for Pre-Surgical Cases:

• • Presurgical Sessions:
    • Number of Sessions: Usually 20-30 sessions.
    • Duration of Each Session: Each session typically lasts 90 minutes at a pressure of 2.0 to 2.5 atmospheres absolute (ATA).
  • Postsurgical Sessions:
    • Additional 10-20 sessions may be recommended following the oral surgery to further promote healing and reduce the risk of complications.
  • Scheduling:
    • Presurgical HBOT is ideally started at least 3-4 weeks before the planned surgery to ensure adequate time to complete the prescribed sessions.  

Why HBOT Helps:

• Increases oxygen delivery to tissues damaged by radiation.
• Promotes angiogenesis (growth of new blood vessels) in irradiated tissues.
• Enhances fibroblast function and collagen synthesis.
• Reduces infection risk by boosting tissue oxygen levels.  

Important Notes:

• The specific number of sessions may vary depending on individual factors, such as the extent of prior radiation damage, the site of surgery, and the overall health of the patient.
• Close coordination between the oral surgeon, oncologist, and a hyperbaric medicine specialist is crucial for optimizing outcomes.

Veterinary Protocol  The use of HBOT in dogs follows adapted protocols based on human medicine, with adjustments for size and species-specific factors.

• Presurgical Sessions:
  • Number of Sessions: Typically 10-20 sessions are suggested.
  • Duration of Each Session: Sessions last approximately 60-90 minutes at pressures of 1.5-2.0 atmospheres absolute (ATA).
• Postsurgical Sessions:
  • Additional 5-10 sessions may be recommended depending on the dog's healing progress and surgical outcomes.
• Monitoring:
  • Dogs should be carefully monitored for signs of oxygen toxicity or other adverse effects during HBOT. Sedation may be required for some patients.

Future Directions

• Human Medicine:
  • Further research into tissue engineering and stem cell therapies to improve healing.
  • Optimization of prophylactic measures such as HBOT and pharmacologic agents.
• Veterinary Medicine:
  • Development of standardized protocols for managing post-radiation complications, including recommendations for the use of hyperbaric oxygen therapy (HBOT) in veterinary medicine. Emerging guidelines suggest that HBOT can support pre-surgical preparation by improving tissue oxygenation, enhancing vascularization, and promoting healing. Typical protocols involve 10-20 sessions at 1.5-2.0 atmospheres absolute (ATA) for 60-90 minutes per session, with an additional 5-10 sessions postoperatively to ensure optimal healing. Further research is needed to validate these approaches and refine their application for specific conditions.
  • Exploration of advanced reconstructive techniques and adjunctive therapies like HBOT in controlled studies.
• Cross-Species Insights:
  • Comparative studies to assess shared pathophysiology and potential therapeutic strategies across species.

Conclusion  Complications following extractions or ONF closures in irradiated fields pose significant challenges in both humans and dogs. While similarities in pathophysiology exist, differences in risk factors, management, and available interventions highlight the need for species-specific approaches. Continued research, particularly in cross-species translational medicine, is essential to improve outcomes for both populations.   Podcast Details Host: Dr. Brett Beckman, DVM, FAVD, DAVDC, DAAPM