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Title Preoperative Identification of the Inferior Alveolar Nerve Anterior Loop via CBCT Imaging Can Influence Implant Treatment Planning
Clinical Question In patients requiring mandibular implant placement anterior to the mental foramen, what percentage of these patients have a radiographically identifiable anterior loop of the inferior alveolar nerve?
Clinical Bottom Line In patients requiring mandibular implant placement anterior to the mental foramen, pre-operative identification of the inferior alveolar nerve anterior loop with CBCT can have an influence on surgical treatment planning. This is based on two retrospective case reports involving a total of 776 subjects showing both a varying range of alveolar nerve anterior loop lengths and differing accuracy between CBCT and panoramic imaging.
Best Evidence (you may view more info by clicking on the PubMed ID link)
PubMed ID Author / Year Patient Group Study type
(level of evidence)
#1) 24583891Filo/2014694 CBCT scansCase Control Study
Key resultsDefining the anterior extension of the alveolar nerve (aAL) as the distance between the anterior border of the mental foramen and the anterior border of the alveolar nerve loop, this study found that 69.73% of patients had a mean aAL value of 1.16 mm. Furthermore, the range of aAL was 0.3-5.6 mm with 95.81% of the values in the 0-3 mm range; thus, assuming a safety margin of 3 mm anterior to the mental foramen, there would still be an approximate 4% potential for nerve injury with implant placement in patients with an aAL.
#2) 25549693Vujanovic-Eskenazi/201582 partially or totally edentulous healthy patients Case Control Study
Key resultsAlthough not statistically significant, the presence of an anterior loop of the alveolar nerve was identified in 36.6% of subjects using panoramic radiography compared to 48.8% of subjects using CBCT.
Evidence Search "Cone-Beam Computed Tomography"[Mesh] AND "Mandibular Nerve"[Mesh]
Comments on
The Evidence
Validity: The Filo study, although not a meta-analysis, involved CBCT scans only (the gold standard in imaging) and used a high number of patients when making measurements to determine the length of the anterior loop. The Vaujanovic-Eskenazi study, although showing a substantial 12% difference in identification of the anterior loop of the alveolar nerve, did not achieve statistically significant results; however, the study directly compared CBCT to panoramic imaging using close to 100 subjects. Perspective: The importance of these studies is directly related to the consequences of not accurately planning for implant placement; mainly, the risk associated with severing the alveolar nerve and associated vascular structures. Furthermore, if only panoramic images are to be used, a substantial hindrance in accuracy and prosthodontic placement must be compromised for by use of over-conservative safety margins (6 mm anterior to panoramic mental-foramen identification).
Applicability In light of the facts that (1) nearly 70% of patients have an anterior extension of the alveolar nerve and (2) it has been shown that panoramic imaging is inferior at identifying this as such compared to CBCT, the potential benefits (less risk of paresthesia and increased prosthodontic flexibility in terms of favorable biomechanical proportions) of proper identification of the alveolar nerve loop in patients receiving implants far outweigh the ALARA concerns a patient might have.
Specialty/Discipline (Oral Medicine/Pathology/Radiology) (General Dentistry) (Oral Surgery)
Keywords alveolar nerve, anterior loop, CBCT, and panoramic radiography
ID# 3115
Date of submission: 11/21/2016spacer
E-mail kats@livemail.uthscsa.edu
Author Joshua Kats, DDS
Co-author(s) e-mail
Faculty mentor/Co-author S. Thomas Deahl, II, DMD, PhD
Faculty mentor/Co-author e-mail deahl@uthscsa.edu
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