Wisdom teeth, or third molars, generally erupt between the ages of 17 and 26 years. These are the last teeth to erupt, and they normally erupt into a position closely behind the last standing teeth (second molars). Space for these teeth to erupt can be limited. Wisdom teeth often fail to erupt or erupt only partially, which is often due to impaction of the wisdom teeth against the second molars (teeth directly in front of the wisdom teeth). In most cases, this occurs when second molars are blocking the path of eruption of third molar teeth and act as a physical barrier, preventing complete eruption. An impacted wisdom tooth is called asymptomatic and disease-free in the absence of signs and symptoms of disease affecting the wisdom tooth or nearby structures.
Impacted wisdom teeth can cause swelling and ulceration of the gums around the wisdom teeth, damage to the roots of second molars, decay in second molars, gum and bone disease around second molars and development of cysts or tumours. General agreement exists that removal of wisdom teeth is appropriate if signs or symptoms of disease related to the wisdom teeth are present. Less agreement exists about the appropriate management of asymptomatic disease-free impacted wisdom teeth.
What was the research?
A systematic review to assess the effects of removal compared with conservative management of impacted wisdom teeth, in the absence of symptoms and without evidence of local disease, in adolescents and adults. This is an update of an existing review published in 2012
Who conducted the research?
The research was conducted by a team led by Hossein Ghaeminia of Radboud University Medical Center on behalf of Cochrane Oral Health. John Perry, Marloes E.L. Nienhujis, Verena Toedtling, Marcia Tummers, Theo J.M. Hoppenreijs, Wil J.M. Van der Sanden and Theodorus G. Mettes were also on the team.
What evidence was included in the review?
We searched the medical literature up to May 2016 and found one randomised controlled trial (RCT) and one prospective cohort study to include in this review. These studies involved 493 participants in total. The RCT conducted at a dental hospital in the UK included 77 adolescent male and female participants, and the cohort study conducted at a private dental clinic in the USA involved 416 men aged 24 to 84 years.
What did the evidence say?
Available evidence is insufficient to show whether or not asymptomatic disease-free impacted wisdom teeth should be removed.
One study at serious risk of bias provided very low quality evidence suggesting that the presence of asymptomatic disease-free impacted wisdom teeth is associated with increased risk of periodontitis (infection of the gums) affecting the adjacent second molar (teeth directly in front of the wisdom teeth) in the long term. In the same study, no evidence was found to suggest that the presence of asymptomatic disease-free impacted wisdom teeth increases the risk of caries affecting the adjacent second molar.
Another study, also at high risk of bias, found no evidence to suggest that removal of asymptomatic disease-free impacted wisdom teeth has an effect on crowding in the dental arch.
The included studies did not measure our primary outcome – health-related quality of life. Nor did they measure our secondary outcomes – costs, other adverse events associated with retention of asymptomatic disease-free impacted wisdom teeth (pericoronitis, root resorption, cyst formation, tumour formation, inflammation/infection) and adverse effects associated with their removal (alveolar osteitis/postoperative infection, nerve injury, damage to adjacent teeth during surgery, bleeding, osteonecrosis related to medication/radiotherapy, inflammation/infection).
How good was the evidence?
Evidence provided by the two studies included in this review is of low to very low quality, so we cannot rely on these findings. High-quality research is urgently needed to support clinical practice in this area.
What are the implications for dentists and the general public?
In light of the lack of available evidence, patient values should be considered and clinical expertise used to guide shared decision making with patients who have asymptomatic disease-free impacted wisdom teeth. If the decision is made to retain asymptomatic disease-free impacted wisdom teeth, clinical assessment at regular intervals to prevent undesirable outcomes is advisable.
What should researchers look at in the future?
Long-term, well-designed prospective studies comparing removal or retention of asymptomatic disease-free impacted wisdom teeth are urgently needed. Well-designed RCTs investigating the long-term and rare effects of retention and removal of asymptomatic disease-free impacted wisdom teeth, in a representative group of individuals, are unlikely to be feasible. If randomisation is not possible, studies should register important baseline data such as age and general and oral health status, including the frequency of dental checkups, the DMFS/T (Decayed Missing Filled Surfaces/Teeth) index or frequency of oral hygiene. These confounding domains should be balanced at baseline or adjusted for with appropriate analyses. A crucial and easily comparable outcome is oral health-related quality of life. However, further development and validation of patient-reported outcome measures (PROMs) are needed in the context of managing asymptomatic disease-free impacted wisdom teeth. The secondary outcomes described in this review are also of great importance for decision making in the management of asymptomatic disease-free impacted wisdom teeth and should be measured in future studies. Because pathology may develop in a wisdom tooth or in the adjacent second molar over the whole of a patient’s lifetime, studies with long-term follow-up (at least five years) are needed. This is very challenging, as young participants are difficult to contact when they move to higher education, travel or change locations while seeking employment.
Ghaeminia H, Perry J, Nienhuijs MEL, Toedtling V, Tummers M, Hoppenreijs TJM, Van der Sanden WJM, Mettes TG. Surgical removal versus retention for the management of asymptomatic disease-free impacted wisdom teeth. Cochrane Database of Systematic Reviews 2016 , Issue 8 . Art. No.: CD003879. DOI: 10.1002/14651858.CD003879.pub4 .