Mandibular ramus grafting a computerized tomography and anatomical study Swarts, Z.1, Wilson, T.1, Willmore, K.1, Perinpanayagam, H.1, Merrifield, P. 1, Galil, K.1,2 Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, Western University1 London Health Sciences Center, University Hospital2, London, Ontario, Canada METHODOLOGY INTRODUCTION CURRENT RESULTS OBJECTIVES ACKNOWLEDGEMENTS REFERENCES Determine the anatomical course and position of the inferior alveolar nerve through virtual and gross cadaveric dissection. Determine the anatomical course and position of the lingual nerve through gross cadaveric dissection. Reveal the location and maximum length, width and depth of a mandibular ramus harvest utilizing knowledge of the course and location of the inferior alveolar and lingual nerves 4. Utilizing inferior alveolar nerve course and measurement, develop a framework for surgical harvesting of the mandibular ramus to minimize disruption and altered sensation. MANDIBULAR BLOCK AUTOGRAFT Approximately 1 million autologous bone grafts performed per year worldwide. The mandibular ramus is a favorable location for bone graft harvest due to: No cutaneous scarring Same operating field for harvest and graft to reduce surgical and anesthesia time Grafts experience minimal volume loss MANDIBULAR BODY ANATOMY The lingual and inferior alveolar nerve (IAN) are both branches of the mandibular nerve from the fifth cranial nerve (trigeminal) that will give off a posterior division that travels along the mandibular canal in the case of the IAN or travels medially to the tongue in the case of the lingual nerve. INCIDENCE OF ALTERED SENSATION Altered sensation of the skin, mucosa and related structures following bone harvesting at the mandibular body has been reported: 16.2% temporary sensory disturbance 2.3% permanent sensory disturbance GROSS CADAVERIC DISSECTION OSTEOTOMY VIRTUAL DISSECTION DISTANCE TO IAN GROSS CADAVERIC DISSECTION- LINGUAL NERVE TO ALVEOLAR RIDGE Preliminary results suggest that the safe thickness of the osteotomy to avoid damage to the inferior alveolar nerve should be no deeper than 3mm, the width should be maximum 11.5mm and the length should be a maximum of 30mm. Donor Info External Oblique: Superior Body: Anterior Body: Inferior Body: Dentate: (n: 9) 30.99 mm SD: 2.91mm 12.17 mm SD: 1.28mm 11.67 mm SD: 1.53mm 31.82 mm SD: 2.61mm Partially Edentulous: (n: 4) 29.78 mm SD: 1.74mm 14.21 mm SD: 1.42mm 13.69 mm SD: 1.99mm 30.55 mm SD: 1.91mm Edentulous: (n: 17) 30.35 mm SD: 2.67mm 13.29 mm SD: 1.35mm 12.29 mm SD: 1.64mm 31.76 mm SD: 3.28mm Table 2: Osteotomy measurements to determine length and width of bone harvest for three specific dental categories 1. GROSS CADAVERIC DISSECTION A B C Donor Info 0% IAN Distance (mm) 25% IAN Distance (mm) 50% IAN 75% IAN 100% IAN Dentate: (n: 9) 2.93 SD: 0.89 3.27 SD: 1.19 3.15 SD: 0.97 2.58 SD: 0.96 2.11 SD: 1.40 Partially Edentulous: (n: 8) 3.46 SD: 1.03 3.64 SD: 1.67 3.21 SD: 1.54 2.71 SD: 1.43 2.10 SD: 1.51 (n: 1) 2.46 2.72 1.48 2.25 Figure 1: Reconstruction of localized maxillary ridge defect with autogenous mandibular ramus block bone graft for dental implant replacement (Singh et al.,2013) Nerve loss info: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4788806/pdf/medoral-21-e241.pdf Figure 3a: Cadaveric mandibles are harvested, heads are bisected and mucosa cleaned from mandibular body region, Figure 3b: Genioglossus muscle was cut and lingual nerve was localized to determine distance from the superior border of the nerve to the alveolar ridge. Figure 3c: Mandibular bone was harvested using a hand drill and chisel, inferior alveolar nerve was noted for its exposure in the graft window. Table 3: Closest distance from the cortical bone at each quartile removed for harvest to the buccal border of the inferior alveolar nerve. 2. VIRTUAL DISSECTION A Total Average (n:30) Dentate (n:9) Partially Edentulous Average (n:4) Edentulous (n:17) Lingual Nerve 14.16 mm SD: 4.89 mm 17.00 mm SD: 3.74 mm 17.59 mm SD: 2.94 mm 11.85 mm SD: 4.65 mm B C Table 4: Distance from the superior border of the lingual nerve to the alveolar ridge, measured at the second molar region. Figure 4a: Using the micro CT Amira Software the area of interest in the mandibular body was isolated and four virtual cuts were made to replicate the bone harvesting procedure used with the cadaveric specimens. Figure 4b: Using the feature “ObliqueSlice” , five separate slices were placed at the quartiles of the area of harvest. Figure 4c: Each micro CT slice was measured to determine the thickness of the cortical bone and the distance to the inferior alveolar nerve. Extending my my most sincere gratitude to: Dr. Khadry Galil, primary supervisor, mentor Committee members: Dr. Wilson, Dr. Willmore, Dr. Perinpanyagam, Dr. Merrifield Clinical Anatomy colleagues Anatomy lab supervisor Haley Linklater and lab technician Kevin Walker Dr. Santiago Cobos Cobos, DDS Table 1a: Donor Data – Cadavers CADAVERIC 30 Total specimens 12 / 30 Male 18 / 30 Female 9 / 30 Dentate 4 / 30 Partially Edentulous 17 / 30 Edentulous Age range: 61-93 (Average: 76.6) Table 1b: Donor Data – Virtual VIRTUAL 18 Total specimens 14 / 18 Male 4 / 18 Female 9 / 18 Dentate 8 / 18 Partially Edentulous 1 / 18 Edentulous Age range: 58-94 (Average: 77.0) Figure 2: Illustration of the course of the mandibular division of the trigeminal nerve. The terminal branches of the inferior alveolar nerve and lingual nerve (yellow),and third molar (red) are shown.(Gray, 1918) Table 1b: Donor data for virtual mandibles: sex, presence of teeth, age range, average age. Table 1a: Donor data for cadaveric mandibles: sex, presence of teeth, age range, average age. 3. MATERIALS AND MEASUREMENT A B C D Singh, A., Gupta, A., Yada, A., & Chaturvedi, T. (2013). Reconstruction of localized maxillary ridge defect with autogenous mandibular ramus block bone graft for dental implant replacement. Journal of Dental Implants, 3, 81-84. Gray, H. (1918). Anatomy of the human body. Philadelphia: Lea & Febiger. Elucidation on the course and position of the IAN and lingual nerve throughout the mandibular body is necessary to avoid nerve damage when harvesting bone in this area. Figures 5a: Micromotor BesQual-2 electric hand drill used for the osteotomy. Figure 5b: Digitial Caliper used for measurements, chisel and hammer used to remove harvested bone, other tools used for cleaning the harvested region. Figure 5c:Buccal aspect of removed bone that was the measured for its length, width and depth. Figure 5d: Harvested bone grafts from the 30 hemi-mandibles being preserved in Dettol.