What are guidelines?

Guidelines are systematically developed statements and recommendations produced to help practitioners and patients make decisions about the best healthcare and treatment for specific circumstances.1 Guidelines should consist of two components; an evidence summary and the detailed instructions on how to apply this to the patient.2 Each guideline statement should be tagged with the level of evidence on which it is based so the reader can take this into account. Guidelines are based on the worldwide available literature to make them applicable to as many patients as possible.

So what is the status of the NICE guidance on wisdom teeth given this description of guidelines and what has been the impact and the implications for patient care in England and Wales?

Guidelines should ideally be based on the highest level of research available such as systematic reviews with meta-analysis of randomised controlled trials (see Figure 1 for hierarchy of evidence). Unfortunately, guidelines may be produced even if high quality research evidence is not available to support them. The NICE guidance on wisdom teeth published in 2000 clearly stated that they had 'no' research evidence to support their recommendations.3 Interestingly, however, the authors claimed that the removal of asymptomatic wisdom teeth should therefore stop because there was no evidence for the health benefit to patients. Surely by implication there was also no evidence for the patient harm that might result from retention of asymptomatic wisdom teeth. Many areas of medicine and dentistry do not yet have a research base describing health benefit but it would seem inappropriate to suspend all of these pending the outcome of future research. The value and intention of guideline publication without good research evidence to support them must surely be questioned.

Figure 1
figure 1

Diagram showing the hierarchy of evidence for clinical guidelines

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Evidence-Based Practice

Evidence-based practice is the explicit and judicious use of current best clinical research evidence to guide healthcare decisions. It integrates this best research evidence with clinical expertise and patient values. The aim of evidence-based practice is to optimise clinical outcomes and the patients' quality of life. Guidelines are an important part of evidence-based practice. The NICE guidance on wisdom teeth states that, 'health professionals are expected to take them fully into account when exercising their clinical judgement about the circumstances in which it is appropriate to consider the extraction of wisdom teeth'.3 They also state that, 'they do not, however, override the individual responsibility of health professionals to make the appropriate decisions in the circumstances of the individual patient, in consultation with the patient and/or guardian/carer'.

Despite this caveat, there is considerable pressure for NHS and independent clinicians to 'comply' with NICE guidance. The opening statement is black and white enough: 'The practice of prophylactic removal of pathology-free impacted third molars should be discontinued.' There is no hint of using the guidance in the context of other aspects of evidence-based practice. The guidance also states that prospective clinical audit programmes should record the proportion of extractions adhering to the criteria described and that such programmes are likely to be more effective when they form part of the organisation's formal clinical governance arrangements. It has become common practice for hospital trusts in England and Wales to include compliance against NICE wisdom tooth guidance on their audit programme without questioning the robustness of the guidance.

One group of researchers assessing the quality of clinical guidelines within dentistry concluded that if recommendations within clinical guidelines are to be relied upon, the methods used in their development must be explicit and free from bias.4 Many busy clinicians will not be familiar with guideline development and rely on NICE to produce guidelines that are reliable.

Global guidance on wisdom teeth

In England and Wales the ability of oral surgeons to make decisions about whether or not impacted wisdom teeth should be removed has been constrained by the NICE guidelines. The decision is in fact usually made by the general dentist who may not refer to the oral surgeon because of the guidance or who may attempt to refer but have the referral returned by referral triage.

How do dentists and oral surgeons make their decision in the rest of the world? In the US very little exists in the way of guidelines and emphasis is placed on the surgeons' opinion and delivery of care that meets the needs of each individual patient.5 The American Association of Oral and Maxillofacial Surgeons provides some indications for wisdom tooth removal but also strongly recommends evaluation by a surgeon. In the US there is encouragement to consider removal of impacted teeth, including asymptomatic teeth and those displaying no signs of disease, in young adulthood. US research suggests that young adults are at risk from periodontitis effecting wisdom teeth which may lead to chronic oral inflammation that has been linked to coronary artery disease, stroke, renal vascular disease, diabetes and even obstetric complications.6,7,8 The mechanism suggested involves bacterial toxins and inflammatory mediators entering the circulation and contributing to the formation of platelet aggregation, adhesions and vascultitis. This research has not been universally accepted, even in the US.

What about the rest of world? It seems that guidelines are not commonly produced and that many other countries tend to follow practice of the US or UK. This emphasises the responsibility of guideline developers in producing robust research-based statements to benefit patients.

Benefits and harms of wisdom tooth removal

The NICE guidance on wisdom teeth describes the harms that may arise from the surgical removal of wisdom teeth but does not describe the benefits. The risks of wisdom tooth surgery as described as including temporary or permanent nerve damage, alveolar osteitis, infection and haemorrhage as well as temporary local swelling, pain and restricted mouth opening. The guidance also states that there are also risks associated with the need for general anaesthesia in some of these procedures, including rare and unpredictable death.9,10

Clinical decision-making should of course be based on the relative benefits and harms for the patient, in the context of best research evidence, clinical experience and patient values. The benefits of wisdom tooth removal will depend on the indication for the removal. If the indication is prevention of pericoronitis then the benefits will be include the alleviation of the effects of pericoronitis. Local effects may include pain, bad taste, swelling of pericoronal tissues, swelling of the face, and trismus. Systemic effects may include lymphadenopathy, pyrexia, malaise, and airway compromise with rare and unpredictable death.

Similarly, if the indication for removal is the prevention of other potential consequences of retention then the benefits include the alleviation of the symptoms and signs of these pathologies. These may include pulpitis or abscess associated with caries of the wisdom tooth or adjacent molar tooth, or infection or pathological fracture associated with development of a dentigerous cyst. The important question is, what is the risk of retained wisdom teeth going on to develop pathology?

Implications for the NHS

Wisdom teeth are the most commonly impacted teeth in the oral cavity and the use of surgical intervention to treat wisdom teeth used to be one of the most commonly performed surgical procedures in the UK.11,12 Interestingly, the number of wisdom tooth surgical procedures had started to reduce in the NHS before the publication of the NICE guidance in 2000. This is thought to have been a consequence of the guidance on wisdom teeth management produced by the Faculty of Dental Surgery of the Royal College of Surgeons of England in 1997. Significant cost savings may have been anticipated on the publication of the NICE guidance but this may not have been realised. It is of course laudable to control expenditure in any healthcare system and the NHS in England and Wales is facing challenges of costs, needs and demands in common with other healthcare systems of the world as a consequence of successfully improving health. The private sector has shown a similar reduction, of around 65%, in the wisdom tooth surgery.13

Implications for patient care

The argument of the NICE guidance is presumably that retention of wisdom teeth means that the patient avoids the morbidity of surgery and develops no future pathology. But is this true? Do patients remain pathology free? One study created an actuarial life-table and related survival analysis to shed light on the natural history of impacted lower third molars.14 Patients were followed for just one year but it was found that 5.47% required removal during this time. Another study that reviewed patients with asymptomatic wisdom teeth four-years after initial assessment found that almost 40% of the wisdom teeth required removal for a variety of reasons including pericoronitis and caries.15 The American Associate of Oral and Maxillofacial Surgeons suggests that 85% of wisdom teeth will eventually require removal.16

The authors own audit experience has found that 37% of 211 consecutive patients referred for the removal of wisdom teeth to a hospital department of oral surgery presented with caries in the adjacent molar requiring restoration or extraction. This concern has been highlighted in a number of publications.17,18,19

The DH produced 'Delivering Better Oral Health an evidence-based toolkit for prevention' in 2007 and updated in 2009 for general dental practitioners and salaried primary care dentists.20 The toolkit is a good example of tagging guideline statements with the level of evidence supporting them. This toolkit does not refer to wisdom teeth which is not unexpected given clear instruction from NICE guidelines that the, 'standard routine programme of dental care' for pathology-free wisdom teeth 'need be no different' than other teeth in the mouth. But is this true? Should a partially erupted wisdom tooth be considered a predisposing factor for caries? The recommendation for patients with predisposing factors is to use a fluoride mouthrinse daily (0.05% NaF) at a different time in addition to brushing with a fluoride varnish and limiting sugar consumption. But we don't have any evidence of efficacy of this recommendation for partially erupted wisdom teeth.

Also, the term in the NICE guideline 'standard routine programme of dental care' is not straightforward when it comes to radiographic examination of wisdom teeth. Not all practices have facilities for dental panoramic radiography, and bitewing and periapical radiographs are usually not helpful for radiographic examination of wisdom teeth. Panoramic radiography is encouraged when 'clinically indicated'21 but this is based on the development of symptoms and signs. In a study investigating pericoronal lesions, over a quarter of the pathology was found to be attributed to dentigerous cyst formation.22

McArdle and Renton evaluated data obtained from a variety of NHS databases from 1989 to 2009 and found that following an initial decline in wisdom tooth surgery following the introduction of NICE guidelines, there was then an increase again to pre-NICE levels. The mean age of patients requiring removal of wisdom teeth increased from 25 years to 32 years over the time period. Their analysis also revealed an increase in those experiencing caries as an indication for removal,23 despite continuing improvement in oral health within the UK population.24 Surgery is associated with greater morbidity when delayed and the patient is older because of increasing bone density and increasing association with medical co-morbidity.10

Evidence

What is the current evidence on retention versus removal of wisdom teeth? A Cochrane systematic review by Mettes et al., published in 2012, found no randomised clinical trials comparing 'removal' with 'retention' of asymptomatic wisdom teeth and concluded that there was no evidence to support or refute removal.26 The authors did find one study that looked only at the effect on late lower incisor crowding but this was of high risk of bias.

Conclusion

Guidelines can be a very useful part of evidence-based practice and support clinicians and patients in making decisions about the best and most appropriate treatment. However, clinical guidelines should be based on best research evidence. The NICE guidance on wisdom teeth has discouraged the removal of wisdom teeth but there is growing evidence that this has not been in best interests of all patients and that for many this is just delaying the inevitable need for surgery. Patients who are referred late may have caries in the adjacent molar tooth or cystic pathology and require more significant surgery than would have been required if they had been referred to an oral surgeon earlier. We need more information about whether prevention of caries in feasible in this situation. The NICE guidelines are now over ten years old and have not been updated since production and publication. We need revised wisdom tooth guidance that interprets wisdom tooth guidance and takes into account the best interests of the patient.

Meanwhile, rather than 'compliance' to guidance that have been produced without the basis of research evidence, we need dentists and oral surgeons to practice evidence-based care, use their clinical expertise and take account of patient values. Consideration should be given to caries risk assessment and the judicious use of radiographs.