Fusion of an impacted third and supernumerary fourth molar tooth with concrescence of the second molar: a very rare case and novel treatment approach

Introduction: We report the very rare case of a symptomatic 41-year-old female presenting with fusion of an impacted third (LL8) and fourth (LL9) mandibular molar tooth with concrescence of the second molar tooth (LL7). We share our experience of pre-operative cone-beam computed tomography (CBCT) to aid surgical planning and the novel use of piezoelectric surgery.

Case Report: A 41-year-old female was referred to the oral and maxillofacial surgery clinic with left jaw pain and swelling. Panoramic radiography revealed an impacted LL8-LL9 fused tooth with concrescence of the LL7. Cone-beam computed tomography showed direct contact with the inferior dental nerve (IDN) and lingual aspect of the double tooth. The patient underwent surgical removal of the LL8-LL9 using piezoelectric surgery to separate the double tooth from the LL7 and minimise trauma to the IDN. The patient was reviewed two weeks post-operatively with no lip/chin/tongue paraesthesia and a well healing socket.

Discussion: Though initially used for osteotomies, piezosurgery has also found success in endodontic and third molar surgery. We present the first case of successfully using pre-operative CBCT in the planning of surgery and piezoelectric surgery to separate an impacted fused LL8-LL9 from a concrescent LL7 without causing trauma to the LL7 or intimately positioned IDN.