A question that everyone who has wisdom teeth wants to know these days is the following: “If you use Computed Tomography (CT) can it lower the risk of developing a nerve injury from having wisdom teeth removed?”
Three authors from Spain (Sanmarti-Garcia, Valmaseda0-Castellon, Gay-Escoda) recently conducted a study asking this question titled “Does Computed Tomography Prevent Inferior Alveolar Nerve Injuries Caused by Lower Third Molar Removal?” appearing in the Journal of Oral and Maxillofacial Surgery (vol 70, pages 5-11, 2012).
The issue is as stated by the authors is that
“panoramic radiography alone cannot identify the buccolingual position of the mandibular canal and the 3M roots.”
Computed tomography (CT) is able to show this information. Even so an estimated 40% of cases show superposition of the roots and the mandibular canal. Hence many of the potential CTs performed may potentially add additional costs and exposes patients to additional radiation without in some cases adding any clinically useful information to the pre-surgical picture.
The authors state
“the utility of CT in the extraction of a 3M is questionable because in most cases it does not modify the surgical technique, it seems to have a low positive predictive value for IAN injury (not much higher than panoramic radiography because the incidence of IAN injury is very low), and it does not always correctly identify the mandibular canal. Unfortunately, although many reports have insisted on the advantages of CT imaging for determining the relation between the lower 3M and the IAN, there have been no reports in the dental literature showing any decrease of the prevalence or severity of IAN resulting from preoperative CT scanning.”
As stated in literature the incidence of inferior alveolar nerve (IAN) injury from wisdom teeth removal is roughly 0.5% to 8%.
The results of the study were
“…CT examinations per se do not seem to significantly decrease the prevalence of IAN injuries”
The study states that sample size is a concern for adequate statistical power but states that using the typical alpha of 0.05 and beta of 0.2 would have required many more hundreds of patients that what was used in the study.
Another potential issue with the study raises is that of selection bias where patients who have a CT performed and show a clear risk may not extract the wisdom teeth.
The authors state that the debate about whether to perform a CT scan for third molar extractions is still open.