1. 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:
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: (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: (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,
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.