Indications for the selective prophylactic removal of mandibular third molar teeth

Student thesis: Doctoral ThesisDoctor of Philosophy


The treatment or otherwise of third molars has been a controversy for a number of years. In 2000, with an emphasis on unnecessary financial costs, untoward patient outcomes and surgical morbidity, and a lack of evidence of any benefits to support prophylactic third molar removal, The National Institute of Health and Clinical Excellence (NICE) moved to eliminate the practice of prophylactic third molar removal from the National Health Service (NHS) with the introduction of its clinical guidance on the removal of wisdom teeth. This guidance led to a significant change in clinical practice in the UK and, as a consequence the practice of prophylactic third molar removal has been significantly reduced. 
Following the introduction of NICE’s guidance, the number of patients having third molars removed in secondary care decreased over the first 3-5 years of the decade. Third molar patient data sourced from the NHS Hospital Episodes Statistics (HES) databases determined treatment patterns for secondary care patients, and from the NHS Business Services Authority (NHSBSA) for primary care patients. For secondary care, patient numbers declined by approximately 30%, from a 90’s decade average of 58k cases per annum, to a low of 39k cases in 2003. In primary care the number of mandibular third molars removed fell by 60% from an average of 77k mandibular third molars in the 90’s to a low of 28k by 2004/5. Following this, and over the last 15 years, there has been a steady increase in the number of patients having third molar removal in secondary care from 39k cases per annum in 2003 to an average of 92k cases per annum for the three years of 2014-17: an increase of 136%. There is no comparable data for primary care in England as such data is no longer collected by the NHS. 
Patients having third molars removed have been shown to be 4 years older on average; from an average age of 28 years in the 90’s, to an average 32 years now. The pattern and nature of diseases indicating third molar removal have also changed. From 1995- 2000 caries and its related disease, such as dental abscess and peri-apical infection accounted for 7% of all third molars removed. By the end of the first decade of the millennium caries and related disease was accounting for approximately 26% of all third molars removed: an increase of over 300%. 
Third molar related caries can be classified in two ways. Impacted mandibular third molars (Md3M) can succumb to dental caries themselves, or contribute to the formation of distal cervical caries (DCC) on the adjacent mandibular second molar (Md2M). These two types of dental caries cannot be discriminated from the NHS databases and consequently the true frequency of third molar caries or Md2M DCC cannot be determined. Historically, Md2M DCC has been reported to account for less than 5% of all third molars removed. With the change in patient management brought about by NICE and the 300% increase in the frequency of caries related to third molars requiring removal, the frequency of Md2M DCC as the reason for third molar removal cannot be determined directly. 
Approximately 90% of DCC lesions of the Md2M are seen related to mesio-angular impacted Md3M and 10% of lesions related to horizontal impactions. Md2M DCC now accounts for 14% of all Md3M removed but remarkably accounts for 44% of all mesio-angular Md3M removed and 60% of all mesio-angular Md3M in patients over the age of 30 years. It is estimated that approximately 23k patients per annum and 27k Md3M are removed per annum due to Md2M DCC, costing approximately £27m per annum to treat with additional potential costs of £28m if patients elected to have remedial implant treatment to replace second molars. 
Md2M DCC as an indication for the removal of the impacted third molar challenges previous concepts and provides evidence for consideration of the prophylactic removal of Md3M.
Date of Award1 Jan 2020
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorFraser McDonald (Supervisor)

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