Dentists' agreement on treatment of asymptomatic impacted third molar teeth: interview study

BMJ 1997; 315 doi: (Published 08 November 1997) Cite this as: BMJ 1997;315:1204
  1. Colwyn M Jones, senior registrar in dental public healtha,
  2. Kevin O'Brien, professora,
  3. A S Blinkhorn, professora,
  4. J P Rood, professora
  1. a Department of Dental Medicine and Surgery, University of Manchester, Manchester M15 6FH
  1. Correspondence to: Mr C M Jones Public Health Medicine, Wigan and Bolton Health Authority, Bryan House, Wigan WN1 1AH
  • Accepted 8 April 1997


The main indications for removal of a third molar tooth were outlined at a consensus development conference of the National Institutes of Health in 1979.1 These are (a) acute or chronic infection in a third molar tooth, (b) damage to adjacent teeth, (c) irreparable decay in the tooth, and (d) a cyst or space occupying lesion in the tooth. Currently a quarter of third molar teeth are removed without being diseased,2 and the need for their removal has been questioned.3 We measured the variation in and reliability of decisions made by a random sample of dentists about the treatment of asymptomatic impacted third molar teeth.

Subjects, methods, and results

We prepared case notes for 25 patients that contained details of the patient's age and sex, a colour intraoral photograph of one asymptomatic lower third molar tooth, and a monochrome glossy print of a radiograph of the lower jaw. All of the patients attended a dentist regularly, and none of them had any coexisting medical or dental conditions to influence the removal or retention of the tooth. The photographs in two cases were poor quality, so only 23 cases were included in the study. A random sample of 90 dentists was selected from the 391 dentists listed by the family health services authorities in two district health authorities in the north west of England. We made an appointment with each dentist to view the case notes and record his or her recommendation. A second assessment was carried out one month later. To prevent dentists from memorising individual cases we asked them if they would repeat the exercise only after they had completed the first assessment. The agreement within each dentist (individual reliability over time) was calculated with the κ statistic. Interexaminer agreement was calculated with multiexaminer κ.4 Significance was taken as P<0.05.

Seventy four dentists agreed to take part in the study; 16 had left or retired when we tried to contact them. All 74 completed the first and second assessments.

At the first assessment the dentists suggested extraction of 0 to 19 teeth (median 6; mean 7.05 (95% confidence interval 5.91 to 8.19)). At the second assessment they suggested extraction of 0 to 21 teeth (median 6; mean 6.77 (5.62 to 7.92)). Agreement between dentists was fair at the first assessment (κ=0.22 (0.21 to 0.23)) and poor at the second (κ=0.11(0.10 to 0.11)). The reliability of the dentists' decisions over time varied from excellent (κ=1.00) for 10 dentists to extremely poor (negative κ score; worse than chance) for one dentist. For 17 dentists reliability was excellent (κ=1.0 to 0.80), for 10 good (κ= 0.79 to 0.6), for 22 moderate (κ=0.59 to 0.4), for 19 fair (κ=0.39 to 0.2), and for 6 poor (κ<0.2).


This study highlights the poor agreement between dentists making decisions on the extraction of asymptomatic lower third molar teeth. Uncertainty in predicting the clinical outcome of leaving an asymptomatic impacted third molar in situ may encourage elective removal.

The surgical removal of teeth is not without risk, especially the risk associated with general anaesthesia. Surgery is also associated with postoperative pain and facial swelling, leading to time lost from work. Up to 6% of patients have paraesthesia of the tongue or lower lip, and 1% have permanent nerve damage.5

We suggest that referrals of asymptomatic third molars could be reduced by improved education and the introduction of clinical guidelines.


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