ORAL HEALTH EVIDENCE-BASED PRACTICE PROGRAM
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Title Pre-Operative Use of Cone Beam CT to Evaluated Location of Mandibular Canal Before Third Molar Extractions
Clinical Question In patients with impacted lower third molars, how does pre-operative use of panoramic radiographs compare to cone beam CT in evaluating the position of the mandibular canal?
Clinical Bottom Line Cone Beam CT can more accurately predict the location of the IA nerve in relation to the roots of lower third molars as compared to traditional radiography. This makes cone beam a valuable pre-operative tool in assessing possible IA nerve injury after mandibular 3rd molar extractions. However, most experts do not routinely use CBCT before lower third molar extractions.
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) 23411471Guang-zhou/2013 537 exractions in 318 patients where the affected tooth intersected the mandibular canal.Retrospective Case Series
Key resultsCone beam CT is accurate at evaluating the position of the mandibular canal. Relationship of the mandibular canal to the roots of third molars is correlated with risk of injury. The mandibular canal located lingual to the roots of lower 3rd molars was associated with the highest rate of injury (18.6%).
#2) 20526245Palma-Carrio/2010 Retrospective data on 552 patients and prospective data on 552 patients.Narrative Review
Key resultsWhen panoramic radiographs indicate direct contact of lower third molar roots with the IA canal, cone beam can be used to evaluate the position of the IA canal in relation to the roots of lower third molars. The authors looked at a study by Susarla and Dodson which analyzed the risk of 46 lower third molars in need of extraction. Traditional radiographs placed 80.4% at high risk of IA nerve injury and CBCT classified 32.6% as high risk. However, most experts do not routinely use CBCT before lower third molar extractions.
Evidence Search IA nerve injury during 3rd molar extractions
Comments on
The Evidence
Validity: The study by Guang-zhou Xu gave relative risk of extraction when the IA canal intersects the roots of lower third molars at different locations. The patients selected for this study were appropriate for evaluation with CBCT. The article by Palma-Carrio was not very strong evidence, but the authors did a good job of evaluating other published data to come to a good conclusion of the clinical relevance of using CBCT before 3rd molar extractions. Perspective: Pre-operative use of CBCT better enables the surgeon to evaluated the relationship between the mandibular canal and the roots of lower third molars.
Applicability CT should only be used on very selective cases. If the 3rd molars MUST be removed, then CT is often just an extra expense to the patient, and should only be used for very select cases. Pre-operative use of cone beam can be used as an aid in determining possible risk of IA nerve injury in elective procedures. Using panoramic radiography for pre-operative planning of lower 3rd molars is still considered an acceptable standard of care.
Specialty/Discipline (General Dentistry) (Oral Surgery) (Periodontics)
Keywords third molars, Cone beam, Panoramic radiographs, CT
ID# 2513
Date of submission: 08/14/2013spacer
E-mail brazilc@livemail.uthscsa.edu
Author Cohl Brazil
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