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Update on coronectomy. a safer way to remove high risk mandibular third molars Tara Renton Dental Update 2024 40:5, 707-709.
Authors
TaraRenton
BDS, MDSc, PhD
Professor of Oral Surgery, King's College London; Honorary Consultant in Oral Surgery, King's College Hospital NHS Foundation Trust and Guy's and St Thomas' NHS Foundation Trust, London
Abstract: Decoronation of high risk mandibular third molars (M3Ms) has become common practice in parts of UK and USA. With the introduction of Cone Beam CT scanning, there has been an evolution in the practice, with avoidance of unnecessary coronectomies based on CBCT findings. Also, additional anatomical features found only on CBCTs have introduced possible additional indications to undertake intentional coronectomy.
Trigeminal nerve injury is the most problematic consequence of dental surgical procedures with major medico-legal implications. Iatrogenic injuries to the third division of the trigeminal nerve remain a common and complex clinical problem. Altered sensation and pain in the orofacial region may interfere with speaking, eating, kissing, shaving, applying make-up, toothbrushing and drinking; namely just about every social interaction we take for granted. Usually after oral rehabilitation, the patient expects and experiences significant improvements, not only regarding jaw function, but also in relation to dental, facial, and even overall body image. Thus these injuries have a significant negative effect on the patient's self-image and quality of life and the iatrogenesis of these injuries lead to significant psychological effects.
Clinical Relevance: Coronectomy is an alternative procedure to complete removal of a mandibular third molar in situations where there is high risk of damage to the inferior alveolar nerve.
Article
Third molar surgery-related inferior alveolar nerve injury is reported to occur in up to 3.6% of cases permanently and 8% of cases temporarily.1,2 Factors associated with Inferior Alveolar Nerve Injury (IANI) are age, difficulty of surgery and proximity to the IAN canal. If the tooth is closely associated with the IAN canal radiographically, 20% of patients having these teeth removed are at risk of developing temporary IAN injury and 1–4% are at risk of permanent injury.1–5
Radiographic signs indicative of possible IAN risk include:
If these plain film radiographic risk factors are identified, removal of the third molar will result in elevated risk of IANI (2% permanent and 20% temporary). The patient must be informed about this elevated risk prior to extraction.
Coronectomy reduces the likelihood of nerve injury by ensuring retention of the vital roots when they are close to the inferior alveolar canal (as estimated on radiographs or CBCT) (Figure 1). The method aims to remove only the crown (all enamel) of an impacted mandibular third molar while leaving the root and pulp undisturbed, thereby avoiding direct or indirect damage to the IAN.
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