J Korean Assoc Oral Maxillofac Surg.  2012 Aug;38(4):231-239. 10.5125/jkaoms.2012.38.4.231.

Evaluation of the course of the inferior alveolar canal in the mandibular ramus using cone beam computed tomography

• Kwon KH
• Sim KB
• Lee JM

• KMID: 2189630
• DOI: http://doi.org/10.5125/jkaoms.2012.38.4.231

Abstract

OBJECTIVES
This study sought to provide guidelines in order to decrease the incidence of nerve injury during mandibular ramus bone harvesting, and to improve understanding of the anatomical structure of the inferior alveolar canal (IAC) to include its distance from the exterior buccal cortex.
MATERIALS AND METHODS
In January and February 2009, 20 patients who visited the Wonkwang University Department of Oral and Maxillofacial Surgery reporting various conditions underwent cone beam computed tomography and were included in this study. Patients with missing left or right mandibular first molars or incisors, or who had jaw fracture or bone pathologies, were excluded. The reference point (R point) was defined as the point where the occlusal plane reached the anterior ramus of the mandible. The position of the IAC in relation to the R point, the buccal bone width (BW), the alveolar crest distance (ACD), the distance from the alveolar crest to the occlusal plane (COD), and the distance from the IAC to the sagittal plane (CS) were determined using proprietary image analysis software which produced cross-sectional coronal and axial images.
RESULTS
The distance medially from the R point to the IAC along the axial plane was 6.19+/-1.21 mm. The HD from the R point, posteriorly to IAC, in the lateral view was 13.07+/-2.45 mm, the VD from the R point was 14.24+/-2.41 mm, and the ND from the R point was 10.12+/-1.76 mm. The pathway of the IAC was positioned almost in a straight line along a sagittal plane within 0.56+/-0.70 mm. The distance from the buccal bone surface to the IAC increased anteriorly from the R point.
CONCLUSION
Marking osteotomy lines in the retromolar area in procedures involving bone harvesting should be discouraged due to the risk of damage to IAC structures. Our measurements indicated that the area from the R point in the ramus of the mandible to 10 mm anterior can be safely harvested for bone grafting purposes.

Keyword

Cone-beam computed tomography; Mandibular nerve

MeSH Terms

Bone Transplantation
Cone-Beam Computed Tomography
Dental Occlusion
Humans
Incidence
Incisor
Jaw Fractures
Mandible
Mandibular Nerve
Molar
Osteotomy
Surgery, Oral

Figure

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  Fig. 1 Schematic of the mandible in lateral view. (R point: reference point)

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  Fig. 2 Schematic of the mandible in superior view. (Mn.: mandible, R point: reference point)

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  Fig. 3 Inferior alveolar canal, coronal cross-sectional. (R point: reference point, RS: R point to sagittal plane distance, COD: distance from the alveolar crest to the occlusal plane, ACD: alveolar crest distance, BW: buccal bone width, CS: distance from the inferior alveolar canal to the sagittal plane)

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  Fig. 4 Schematic of lateral view of IAC position measurements. (Ant.: anterior, IAC: inferior alveolar canal, R point: reference point, HD: horizontal distance, ND: nearest distance, VD: vertical distance, NDx: nearest distance on x plane, VDx: vertical distance on x plane, X: distance from baseline)

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  Fig. 5 IAC position measurements, cross-sectional occlusal plane. (IAC: inferior alveolar canal, VD: vertical distance, R: reference)

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  Fig. 6 Course of inferior alveolar canal along a sagittal plane (mean±standard deviation) (+10 mm=anterior, R point=buccal/lateral). (R point: reference point)

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