Impacted Wisdom Teeth Near the Nerve: Types of Impaction, CT Checks, and Criteria for Referral to Oral & Maxillofacial Surgery

What is an impacted wisdom tooth?

An impacted wisdom tooth is one that has not erupted into its normal position and remains in the gum or jawbone [1]. Impaction is classified as soft tissue impaction (covered only by gum), partial bony impaction (partly covered by bone), and complete bony impaction (fully buried in bone), and extraction difficulty depends on the angle (horizontal, mesially tilted, and so on) and depth [2]. When DentStat analyzed 2,600 patient comments on impaction and nerve proximity, questions about impaction types were repeatedly accompanied by fear of numbness and anxiety about what consent forms say [3]. This article lays out, in order, the checking procedures and referral criteria that these worries are about.

What does it mean that it’s close to the nerve?

Inside the lower jawbone runs a canal (the inferior alveolar nerve canal) carrying the inferior alveolar nerve, which provides sensation to the lower lip and chin skin, and the lingual nerve runs on the tongue side [1]. The roots of lower wisdom teeth sometimes form close to this nerve canal, so the distance between them and whether they touch are assessed before extraction [1]. Proximity does not mean damage, and the purpose of the assessment is to understand the positional relationship in advance and plan the approach [2]. Sensation in the area sometimes becomes dull after extraction, but this is often temporary, and if it persists, it needs care [1].

When is a CT scan needed?

When the basic panoramic X-ray shows signs of proximity, such as the wisdom tooth roots appearing to overlap the nerve canal, CT confirms the 3D positional relationship [1]. A panoramic image is two-dimensional, so it is hard to tell whether an overlap is actual contact, whereas CT shows the cheek-side and tongue-side positions of the roots and nerve canal and the distance between them in three dimensions [2]. Not every wisdom tooth extraction needs CT. It is considered when more information is needed, such as signs of proximity or deep impaction [1]. The comment analysis also found many questions asking why CT was recommended, showing demand for explanations of the criteria [3].

When are patients referred to Oral & Maxillofacial Surgery?

The following findings are generally the reasons for referral [1][2].

Finding	Details
Proximity to or contact with the nerve canal	CT confirms contact between the roots and the nerve canal [1]
Complete bony or horizontal impaction	Deep impaction requiring removal of a wide area of bone [2]
Accompanying lesions	Pathological findings such as cysts are present as well [2]
Overall health	Systemic management is needed, such as for bleeding risk [1]

Referral is a routine procedure that takes equipment and specialty into account and should not be read as a sign that the condition is especially serious [1]. For upper wisdom teeth, the main point of assessment is the distance to the maxillary sinus rather than the nerve, and if the roots are close, the possibility of perforating the sinus during extraction is assessed in advance [2].

What is coronectomy, which leaves part of the root?

Coronectomy is a planned procedure for lower wisdom teeth very close to the nerve canal in which only the crown of the tooth is removed and the roots are left in place [2]. Its purpose is to avoid nerve irritation that could occur while forcing out the roots, and the remaining roots are monitored with regular imaging [2]. The comment analysis found questions about whether leaving the roots and stitching was a mistake [3], but if it was a coronectomy explained in advance, it is one of the options for protecting the nerve [2]. Whether it applies depends on the type of impaction and condition of the roots, so discuss it with a dentist.

Common myths and facts

Some people take a finding of nerve proximity as a sure sign of numbness, but proximity is grounds for further checks and planning, not a prediction of the outcome [1]. The altered sensation item on a consent form is a procedure for explaining possible situations in advance, and being told about specific risks is itself part of normal care after imaging assessment [1]. Some also believe that a deeply impacted tooth can be left alone if it causes no symptoms, but impacted wisdom teeth can be linked to cavities in the neighboring molar and cysts, so a plan is needed, whether regular imaging follow-up or extraction [2]. In the comment analysis, many questions asked definitively about the chance of numbness, but there were also reports of anxiety easing after people were walked through the CT check and referral process [3].

For an overview of when wisdom teeth are extracted, how pain progresses, and insurance coverage, see the wisdom tooth guide. For dental clinics by region, see Find a Dentist.