Health Technology Assessment 2000; Vol. 4: No. 15 Rapid reviewThe effectiveness and cost-effectiveness of prophylacticremoval of wisdom teethF SongS O’MearaP WilsonS GolderJ KleijnenHealth Technology AssessmentNHS R&D HTA Programme HTA
Standing Group on Health TechnologyCurrent membersChair: Professor John Gabbay Dr Jeremy Metters Dr John TrippProfessor Kent Woods Director, Wessex Institute Deputy Chief Medical Officer, Senior Lecturer in ChildProfessor of Therapeutics, for Health Research Department of Health Health, Royal Devon and ExeterUniversity of Leicester & Development Healthcare NHS Trust Professor Maggie Pearson Regional Director of R&D, Professor Sir John Professor Tom Walley NHS Executive North WestProfessor Martin Buxton Grimley Evans Director,Director & Professor of Professor of Clinical Geratology, Mr Hugh Ross Prescribing Research Group,Health Economics, Radcliffe Infirmary, Chief Executive, University of LiverpoolHealth Economics Oxford The United BristolResearch Group, Healthcare NHS TrustBrunel University Dr Tony Hope Dr Julie Woodin Professor Trevor Sheldon Chief Executive, Clinical Reader in Medicine,Professor Shah Ebrahim Joint Director, York Health Nottingham Health Authority Nuffield Department ofProfessor of Epidemiology Policy Group, University of York Clinical Medicine,of Ageing, University of Bristol University of Oxford Professor Mike SmithProfessor Francis H Creed Faculty Dean of ResearchProfessor of Professor Richard Lilford for Medicine, Dentistry,Psychological Medicine, Regional Director of R&D, Psychology & Health,Manchester Royal Infirmary NHS Executive West Midlands University of LeedsPast membersProfessor Sir Miles Irving* Professor John Farndon Professor Michael Maisey Professor Martin RolandProfessor of Surgery, Professor of Surgery, Professor of Professor of General Practice,University of Manchester, University of Bristol Radiological Sciences, University of ManchesterHope Hospital, Salford Guy’s, King’s & St Thomas’s Professor Charles Florey Professor Ian Russell School of Medicine & Dentistry,Dr Sheila Adam Department of Epidemiology Department of Health Sciences LondonDepartment of Health & Public Health, Ninewells & Clinical Evaluation, Hospital & Medical School, Mrs Gloria Oates University of YorkProfessor Angela Coulter University of Dundee Chief Executive,Director, King’s Fund, Professor Howard Oldham NHS Trust Dr Charles SwanLondon Consultant Gastroenterologist, Glennester Dr George Poste North Staffordshire Professor of Social ScienceProfessor Anthony Culyer & Administration, London Chief Science & Technology Royal InfirmaryDeputy Vice-Chancellor, School of Economics & Officer, SmithKline BeechamUniversity of York Political Science Professor Michael RawlinsDr Peter Doyle Mr John H James Wolfson Unit ofExecutive Director, Zeneca Ltd, Chief Executive, Clinical Pharmacology,ACOST Committee on Medical Kensington, Chelsea & University of Newcastle-Research & Health Westminster Health Authority upon-Tyne * Previous Chair Details of the membership of the HTA panels, the NCCHTA Advisory Group and the HTA Commissioning Board are given at the end of this report.
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The effectiveness and cost-effectiveness of prophylacticremoval of wisdom teethF Song*S O’MearaP WilsonS GolderJ KleijnenNHS Centre for Reviews and Dissemination, University of York, UK* Corresponding authorCompeting interests: none declaredPublished July 2000This report should be referenced as follows:Song F, O’Meara S,Wilson P, Golder S, Kleijnen J.The effectiveness and cost-effectivenessof prophylactic removal of wisdom teeth. Health Technol Assess 2000;4(15).Health Technology Assessment is indexed in Index Medicus/MEDLINE and ExcerptaMedica/EMBASE. Copies of the Executive Summaries are available from the NCCHTAwebsite (see overleaf).The NHS Centre for Reviews and Dissemination was previously commissioned in 1996,by the Faculty of Dental Surgery of The Royal College of Surgeons of England, to producean assessment of published reviews. A version of this report appeared as:Song F, Landes D, Glenny A, Sheldon T. Prophylactic removal of impacted third molars: anassessment of published reviews. Br Dent J 1997;182:339–46.The review was updated for the Effectiveness Matters series in 1998: Prophylactic removalof impacted third molars: is it justified? Effectiveness Matters 1998;3(2).
Health Technology Assessment 2000; Vol. 4: No. 15 Contents List of abbreviations .................................... i 4 Discussion and conclusions ........................ 11 Quality of available evidence ......................... 11 Executive summary .................................... ii Conclusions .................................................... 121 Background ................................................... 1 Introduction .................................................. 1 Acknowledgements .................................... 13 Impacted third molars ................................ 1 References ..................................................... 15 Pathological changes associated with impacted third molars ................................... 2 Appendix 1 Search strategies ...................... 19 Complications and risks following surgery .. 22 Aims and methods Appendix 2 Summary of data extraction Aims ................................................................ 3 and quality assessment of RCTs ... ................ 21 Methods .......................................................... 3 Appendix 3 Summary of data extraction3 Results ............................................................ 5 and methodological assessment of Included studies ............................................. 5 literature reviews ............................................ 25 Excluded studies ............................................ 5 Results from RCTs .......................................... 5 Appendix 4 Data extraction summary for Results from literature reviews ...................... 6 decision analysis studies ................................. 39 Decision analyses for third molar surgery .... 7 Cost and cost-effectiveness analysis of Appendix 5 Studies excluded from prophylactic removal of third molars ........... 9 the review ........................................................ 43
Health Technology Assessment 2000; Vol. 4: No. 15 List of abbreviations3M(s) third molar(s)*AL arch length*CCTR Cochrane Controlled Trials RegisterCI confidence interval*DSD days of standard discomfortICW intercanine width*LII Little’s Irregularity Index*NICE National Institute for Clinical ExcellenceRCT randomised controlled trialSCI Science Citation IndexSD standard deviation*SIGN Scottish Intercollegiate Guidelines Network* Used only in tables i
Health Technology Assessment 2000; Vol. 4: No. 15 Executive summaryBackground surgical removal of third molars either as prophylaxis or due to associated pathologicalRemoval of wisdom teeth is one of the most changescommon surgical procedures performed in the • reported outcomes – either the pathologicalUK. Little controversy surrounds the removal of changes associated with retention of thirdimpacted third molars when they are associated molars, or post-operative complicationswith pathological changes such as infection, non- following extraction.restorable carious lesions, cysts, tumours, anddestruction of adjacent teeth and bone. However, There were no language restrictions on studythe justification for prophylactic removal of selection.impacted third molars is less certain and has beendebated for many years. Data extraction and synthesis Data from included studies were extracted into structured tables and individual study validity wasObjectives assessed against methodological checklists. Data were summarised descriptively. Decisions relating• To provide a summary of existing evidence on to study selection, data extraction and validity prophylactic removal of impacted wisdom teeth, assessment were made by two independent in terms of the incidence of surgical reviewers, and disagreements were resolved by complications associated with prophylactic discussion. For non-English papers, translators removal, and the morbidity associated with were recruited to assist with study selection and retention. data extraction.Methods ResultsA systematic review of the research literature was Forty studies were included in the review: twoundertaken. RCTs, 34 literature reviews, and four decision analysis studies.Data sourcesAn existing review formed the basis of this report, One RCT in the UK focused on the effects ofand additional literature searches were retained third molars on incisor crowdingundertaken, including searches of electronic (predominantly a cosmetic problem) in patientsdatabases (MEDLINE, 1984–99; EMBASE, 1984–99; who had previously undergone orthodonticScience Citation Index, Cochrane Controlled Trials treatment. The results of this trial suggested thatRegister, National Research Register; Database of the removal of third molars to prevent late incisorAbstracts of Reviews of Effectiveness), paper crowding cannot be justified. Another on-goingsources (including Clinical Evidence), and web- RCT in Denmark compares the effects and costs ofbased resources. Relevant organisations and prophylactic removal of third molars with removalprofessional bodies were contacted for further according to morbidity. So far, this trial hasinformation. recruited 200 participants, and preliminary results indicate that watchful waiting may be a promisingStudy selection strategy. However, more data and longer follow-upStudies were selected for inclusion if they met the of patients are needed to conclude whichfollowing criteria: treatment strategy is the most cost-effective. It is also known that a trial is on-going in the USA but• design – randomised controlled trials (RCTs), no results are available so far. literature reviews, or decision analyses• participants – people with unerupted or The methodological quality of the literature impacted third molars, or those undergoing reviews was generally poor, and none of the reviews iii
Executive summary was systematic. Conclusions from nine reviews on groups of researchers) consistently suggested that anterior crowding suggested that there was only a retention of third molars was cost-saving and more weak association between retention of third molars cost-effective compared with prophylactic removal and crowding. Six out of 21 reviews with a more of impacted third molars. general scope also concluded that the prophylactic removal of third molars was unjustified. Twelve general reviews did not conclude with a clear Conclusions message about the management of third molars. Three reviews suggested that prophylactic removal There is no reliable research evidence to support of third molars is appropriate, but these reviews the prophylactic removal of disease-free impacted were of poorer methodological quality than the third molars. Available evidence suggests that majority of other reviews. Three out of four papers retention may be more effective and cost-effective focusing on surgical management expressed than prophylactic removal, at least in the short to uncertain conclusions relating to the prophylactic medium term. extraction of third molars. It is difficult to compare prophylactic removal of Recommendations for research impacted third molars with retention in the 1. Although data from observational studies may absence of disease, partly because these two be useful, there is a need for well-designed RCTs strategies are related to different types of to compare prophylactic removal with outcomes. By using utility methods, four decision management by deliberate retention, using analyses made it possible to compare different long-term follow-up. outcomes directly in the coherent models. 2. There is also a need for decision analysis models Although there were important differences in the that could be used to compare long-term structure and methods for estimating input values, outcomes of prophylactic removal with retention the findings of the decision analyses (by two of impacted third molars.iv
Health Technology Assessment 2000; Vol. 4: No. 15 Chapter 1 BackgroundIntroduction risk of pathological changes and symptoms; if they are removed only when pathological changesRemoval of third molars (wisdom teeth) is one of occur, patients may be older and the risk of seriousthe most common surgical procedures performed post-operative complications may be greater.in the UK. In 1994–95 there were over 36,000in-patient and 60,000 day-case admissions in On the other hand, the probability of impactedEngland for ‘surgical removal of tooth’.1 Third third molars causing pathological changes in themolar surgery has been estimated to cost the future may be exaggerated.3,13 Many impacted orNHS in England up to £30 million per year,2 and unerupted third molars may eventually eruptapproximately £20 million is spent annually in the normally and many impacted third molars neverprivate sector.3 Around 90% of patients on waiting cause clinically important problems.14 In addition,lists for oral and maxillofacial surgery are third molar surgery is not risk-free. The com-scheduled for third molar removal.3 plications and suffering following third molar surgery may be considerable.15There are wide variations in rates of third molarsurgery across the UK.2,4 There is some evidence Therefore, the decision to remove third molarsthat deprived populations with poor dental health prophylactically should be based on an estimateare less likely to have third molars removed of the balance between the likelihood of retainedcompared with more affluent populations with third molars causing problems in the future andgood dental health.2,5 However, the reasons for the risks or advantages of surgery carried outthis are complex. earlier compared with later. However, it is not possible to predict reliably whether impacted thirdThe proportion of third molar surgery which is molars will develop pathological changes if theycarried out prophylactically is difficult to estimate are not removed. Wide variation has been observedprecisely and depends on the definitions used. among practitioners in their perceived risk ofSome estimates of prophylactic removal suggest future associated pathological changes and inrates of between 20% and 40%,6–8 but rates as treatment decisions in the management oflow as 4% have been reported.9 A UK survey of impacted third molars.16–18181 consultants found that of 19,971 third molarsreferred to hospital for assessment, and sub-sequently removed, 43.9% were disease-free.10 This Impacted third molarssurvey also revealed that relatively more maxillarythird molars than mandibular third molars were Impaction occurs where there is prevention ofremoved prophylactically. The rate of disease-free complete eruption into a normal functionalextracted teeth was 79.0% in 7735 maxillary third position of one tooth by another, due to lack ofmolars and 21.8% in 12,236 mandibular third space (in the dental arch), obstruction by anothermolars.10 tooth, or development in an abnormal position. According to the definitions given by the FacultyLittle controversy surrounds the removal of of Dental Surgery of the Royal College of Surgeonsimpacted third molars when they are associated of England,12 a tooth that is completely impactedwith pathological changes such as infection, non- is entirely covered by soft tissue and partially orrestorable carious lesions, cysts, tumours, and completely covered by bone within the mandibledestruction of adjacent teeth and bone.11,12 (lower jaw) or maxilla (upper jaw); partialHowever, the justification for prophylactic removal eruption occurs when the tooth is visible in theof impacted third molars is less certain and has mouth but has failed to erupt into a normalbeen debated for many years. functional position.Several reasons are given for the early removal of It should be noted that any normally erupted teethdisease-free impacted third molars: they have no used to be unerupted and partially erupted atuseful role in the mouth; they may increase the certain stages of eruption process. Therefore, 1
Background unerupted or partially erupted teeth may not is not considered to warrant the removal of be impacted.12 third molars.22–24 Cyst development is very rare and is not Pathological changes associated considered to be an indication for prophylactic removal.19 The risk of malignant neoplasms with impacted third molars arising in a dental follicle is negligible and is Impacted third molars may be associated with not considered to be an indication for prophy- certain pathological changes such as infections, lactic removal.19 dental caries, destruction of adjacent teeth, cysts and tumours. Although impacted third molars do not necessarily cause some of these pathological Complications and risks changes (such as dental caries), the impaction may increase the risk of disease, particularly when oral following surgery hygiene is poor. The potential benefit of avoiding the relatively uncommon risks of pathological changes Pericoronitis (inflammation of the gingiva associated with leaving impacted third molars in surrounding the crown of a tooth) is the most place needs to be considered alongside the risks common indication for third molar surgery,10 associated with their removal. and mainly occurs in adolescents and young adults, and less commonly in older people.19 One study Common complications following third molar reported that during 4 years of follow-up, 10% of surgery include temporary or permanent sensory lower third molars developed pericoronitis.20 nerve damage (including anaesthesia and paraesthesia), dry socket (alveolar osteitis, or Very few impacted third molars cause dental caries dry appearance of the exposed bone in the (decay) of second molars,19 though estimates of socket), infection, haemorrhage and pain. the rate vary (1% to 4.5%).15 Other possible complications include severe trismus (lockjaw), oro-antral fistula, buccal There is a low incidence (less than 1%) of root fat herniations, iatrogenic damage to the resorption of second molars with impacted third adjacent second molar, and iatrogenic molars.20,21 One review concluded that the risk of mandibular fracture. second molar root resorption by impacted third molars is low, and is likely to occur in younger The rate of sensory nerve damage after third molar patients for whom surgery is claimed to be surgery has been shown to range from 0.5% to associated with lower morbidity.19 20%.15,19,25,26 The reported overall rate of dry socket varies from 0% to 35%.15,27 The risk of dry socket The association between anterior (front) incisor increases with lack of surgical experience and crowding (predominantly a cosmetic problem) tobacco use.28 and impacted third molars is not significant and2
Health Technology Assessment 2000; Vol. 4: No. 15 Chapter 2 Aims and methods • Cochrane Controlled Trials Register (CCTR)Aims • National Research Register (NRR)This review aims to provide a summary of • Database of Abstracts of Reviews of Effectivenessexisting evidence on prophylactic removal (DARE)of impacted wisdom teeth, in terms of the • NHS Economic Evaluation Database (NHSEED).incidence of surgical complications associatedwith prophylactic removal and the morbidity Paper sources searched included Clinical Evidenceassociated with retention. (BMJ Publishing Group). A search on the following web-based resources was also carried out:Methods • Scottish Health Purchasing Information Centre (SHPIC) reportsSelection criteria for studies • Scottish Intercollegiate Guidelines NetworkStudies were selected for inclusion if they met the (SIGN) guidelinesfollowing criteria. • Agency for Health Care Policy and Research (AHCPR) clinical practice guidelinesStudy design • Guide to Clinical Preventive Guidelines,Evaluations in the form of any relevant literature Development and Evaluation Committee (DEC)reviews (published as a full paper) or randomised reportscontrolled trials (RCTs) (published as a full paper, • International Network of Agencies for Healthabstract, editorial, or letter) were considered for Technology Assessment (INAHTA) publishedinclusion. Literature reviews could include both reports and ongoing reviewsRCTs or other studies designed to address • National Coordinating Centre for Healthlong-term outcomes. Papers in all languages Technology Assessment (NCCHTA) reportswere considered. • Turning Research Into Practice (TRIP) • resources produced by the University ofParticipants Sheffield School of Health and RelatedStudies recruiting people with unerupted or Research (ScHARR), including ‘Netting theimpacted third molars, and those undergoing Evidence’ and the Internet Database ofsurgical removal of unerupted or impacted Evidence-Based Abstracts and Articlesthird molars, either as prophylaxis or because (IDEA) Topic List.of pathological changes, were eligible forinclusion. Other sources of information included The Faculty of Dental Surgery of the Royal College of SurgeonsOutcomes of England and The British Dental Association,Reported outcomes had to include either the who provided additional information as submissionpathological changes and/or symptoms associated of evidence to the National Institute for Clinicalwith unerupted or impacted third molars, Evidence (NICE). In addition, SIGN supplied theor outcomes following surgical removal of NHS Centre for Reviews and Dissemination with athird molars. draft copy of their forthcoming guidelines on the management of third molars. The reference lists ofSearch strategy included articles were also checked to identifyAn existing review formed the basis of this report.23 relevant studies.Some additional searches of the following databaseswere carried out, with no language restrictions: The strategies used for searching MEDLINE, EMBASE, SCI, and CCTR are presented in• MEDLINE (1984–99) appendix 1.• EMBASE (1984–99)• Science Citation Index (SCI) (via the BIDS Decisions on the inclusion of studies service) Titles and abstracts of studies identified by the 3
Aims and methods searches were assessed for relevance by two (Table 3 ) for literature reviews, and in appendix 4 independent reviewers. Any disagreements were (Table 4 ) for decision analysis studies. resolved by discussion, and failing this, by recourse to a third reviewer. Full papers were retrieved if Quality assessment they appeared to meet the inclusion criteria, or if Selected articles were assessed by two reviewers there was doubt as to whether they were eligible. independently, with discrepancies resolved though Screening of full papers was checked indepen- discussion. For RCTs the following aspects were dently by two reviewers, and disagreements were assessed: participant selection criteria, sample size, resolved as above. reported use of a priori power calculation, method of randomisation, baseline comparability of treat- Data extraction ment groups, use of blinded outcome assessment, Data were extracted into a structured table, and appropriate use of statistical methods for data accuracy was checked by a second, independent, analysis, reporting of withdrawals, and use of the reviewer. Discrepancies were resolved through intention-to-treat analysis. For literature reviews discussion. Different structured tables were used the following were evaluated: clarity of review aims, for reviews and RCTs. The data extracted from literature search, selection criteria, validity RCTs included study aims, method of randomisation, assessment, presentation of details of primary use of a priori power calculation, selection criteria studies, and methods of summarising data. The for participants, baseline characteristics of groups, summary of validity assessment is shown in the data intervention details, numbers allocated to each extraction tables (Table 2, appendix 2 and Table 3, group, setting of treatment, outcome measurements, appendix 3). statistical methods, results per group for each outcome, follow-up, withdrawals, and author’s Data pooling main conclusions. The data extracted from Data from literature reviews were summarised literature reviews included review aims, total descriptively. Two RCTs were identified and these number of references, and author’s main were not similar enough to allow for statistical conclusions. pooling (meta-analysis) of results. Therefore, these data were also combined descriptively. For non-English papers, translators were recruited Some cost-effectiveness data were identified in to assist with study selection and data extraction. terms of the potential cost savings associated with The data extraction summary tables are shown in reduced rates of prophylactic removal, which have appendix 2 (Tables 1 and 2) for RCTs, in appendix 3 been summarised as part of this report.4
Health Technology Assessment 2000; Vol. 4: No. 15 Chapter 3 Results the trial, but only 77 (47%) were available for dataIncluded studies collection at the 5-year follow-up.The search strategy detailed in chapter 2 generated4682 references of possible relevance to this There were no statistically significant changesreview. Once titles (and, when available, abstracts) over time between the two groups in terms ofhad been assessed, hard copies of 290 papers irregularity of dentition or intercanine width.were examined. Of these, 40 studies were included There was, however, a small but statisticallyin this review: two RCTs,24,29 34 literature significant difference in decrease in arch length,reviews,4,13,15,19,22,30–59 and four decision analysis with a slightly smaller decrease in the group thatstudies.26,60–62 One of the literature reviews was underwent surgery. A similar pattern of results waspublished as two separate papers.51,52 Two papers seen when some cases identified as having residualpublished in French63,64 duplicated an English spacing from prior premolar extractions werelanguage article, already included in this review.15 excluded from the analysis. Generalised linearOne paper published in Danish could not be modelling showed that there were no statisticallyretrieved.65 significant differences between those completing the study and those who were lost to follow-up.One RCT is a UK study,24 and the other, ongoing,trial is based in Denmark29 (appendix 2). Twelve Overall the trial was well conducted. However,literature reviews were conducted in the USA, four there was no reported power calculation forin Canada, four in the UK, four in Italy, three in sample size, and so the power of the study to detectFrance, two in Belgium, and one each in Hungary, true treatment effects is uncertain. In addition,Switzerland, Finland, Sweden, and South Africa there are few data relating to baseline(appendix 3). Two of the decision analysis studies characteristics of participants according towere conducted in the USA and two were treatment arm.conducted in the UK (appendix 4). Vondeling and colleagues (1999)29 This trial in Denmark is ongoing, and aims to assessExcluded studies the cost-effectiveness and clinical effectiveness of the prophylactic removal of third molars comparedA further 29 studies were closely considered for with extraction carried out according to associatedinclusion but were eventually excluded from the morbidity. The method of randomisation was notreview.66–94 Common reasons for exclusion described, but participants were allocatedincluded study design, discussion of impacted teeth according to a blocked and stratified scheme. Onlyother than third molars, or description of different brief selection criteria were given, namely thatsurgical techniques or methods of treating post- participants had to be healthy, aged between 18operative complications. Details of excluded and 30 years, and to have at least one mandibularstudies are shown in appendix 5 (Table 5 ). third molar remaining. No information was given about baseline characteristics of study groups. So far, 200 participants have been recruited, but thisResults from RCTs figure was not broken down by group. It is anticipated that by the end of the trial 500Harradine and colleagues (1998)24 participants will be recruited, 100 of whom willThis UK-based trial focused on the effects of undergo prophylactic extraction. Only descriptiveretained third molars on incisor crowding. A results were provided, and these suggested thatrandom number list was used to allocate par- prophylactic removal of third molars may beticipants to either extraction or retention of third associated with decreased functional health status,molars. All patients had previously undergone increased healthcare costs and production losses,orthodontic treatment. The mean age of entry to and that few patients in the watchful waiting groupthe trial was 14 years 10 months, and 55% of the have developed pathological changes that wouldsample were female. In total, 164 patients entered warrant removal of third molars. The authors 5
Results cautiously suggest that watchful waiting may be the were uncertain and no clear answer was given more favourable strategy, but further results are about the appropriateness of prophylactic removal awaited with interest. of impacted third molars.15,30,31,35,39,40,48,50,55,57–59 Six of the general reviews concluded that prophylactic removal of impacted third molars was Results from literature reviews unjustified.4,13,19,41,51,52,56 Three reviews44,46,54 recommended the prophylactic removal of third Thirty-four published literature reviews were ident- molars but the methods used in each of these ified which fulfilled inclusion criteria for the review reviews were poorer than for many other reviews reported here. Data extraction summary tables are with different conclusions (appendix 3). Out of presented in appendix 3 (Table 3 ). Twenty-one of four papers focusing on surgical complications, the assessed reviews covered general issues about three expressed uncertain conclusions,37,45,47 and the appropriateness of prophylactic removal of one was in favour of prophylactic removal.36 impacted third molars.4,13,15,19,30,31,35,39–41,44,46,48,50–52,54–59 Nine reviews focused on the association of crowding with third molars,22,32–34,38,42,43,49,53 and four Decision analyses for third molar reviews were concerned with complications following third molar surgery, namely, periodontal surgery defect,45 and sensory nerve damage.36,37,47 The appropriateness of prophylactic removal of impacted third molars should be evaluated by Methodological quality of the comparing the outcomes of prophylactic removal reviews with the outcomes of retaining teeth. One The methodological quality of the literature difficulty in the comparison of the two strategies is reviews was generally poor, and none could be in valuing and comparing the various outcomes. described as systematic. Details of study quality The outcome of surgical removal of impacted third assessment are shown with data extraction in molars is measured by the rate of various appendix 3 (Table 3 ). With one exception,4 none of complications. On the other hand, the conseq- the reviews gave details of using a structured search uences of deliberate retention of impacted third strategy to identify primary material or selection molars in the absence of associated morbidity will criteria for studies. The details of individual studies include the incidence of different pathological quoted in these literature reviews were usually changes and the rate of complications following insufficient for readers to judge the reliability of delayed surgical removal. the evidence provided. Several reviews included very brief comments on the methodological quality To be directly comparable, the outcomes of the two of primary studies,4,13,15,22,39,40,51,52 but none strategies need to be summarised by a common described a systematic assessment of validity. method. This problem has been addressed in The literature included in these reviews included several decision analyses.26,60–62 For example, ‘days reviews and case reports as well as reports of of standard discomfort’ (DSD) was used as a single studies that used a range of methodologies, unit outcome measure to estimate extraction including retrospective or prospective, cross- outcome in a decision analysis by Tulloch and sectional or longitudinal observational studies. Antczak-Bouckoms.61 In another study, the outcome No RCTs comparing the long-term outcome of was measured by a utility value that “represents a early removal with that of deliberate retention condensation of the biological, physical, of disease-free third molars were identified. sociological, and psychological parameters that These literature reviews seldom quantitatively influence a person’s sense of well-being”.26 summarised the risk of removal or retention of impacted third molars. The major features and findings from the four identified decision analyses that compared different Conclusions from reviews strategies for managing third molars are shown in Eight out of nine reviews on anterior crowding appendix 4 (Table 4 ). A decision analysis by ECRI concluded that prophylactic removal of third (an independent nonprofit health services research molars for the prevention of crowding of lower agency) has been included in Table 4 but will not be anteriors was not justified.22,32–34,42,43,49,53 The other discussed in detail here because it considered only review38 recommended prophylactic removal of economic consequences after different strategies.39 third molars, but review methods were very poor, The ECRI study concluded that there are no and only nine references were cited overall. reliable predictors of pathological changes and6 The conclusions from 12 of the 21 general reviews disease and that although prophylactic removal of
Health Technology Assessment 2000; Vol. 4: No. 15third molars decreases the likelihood of future molars with pathological changes. This strategy waspathological changes and post-operative associated with the lowest expected disability andcomplications, it does not alleviate anterior dental also the lowest expected cost. Estimations of DSDarch crowding. Surgery may benefit only one in six were 2.27, 0.67, and 0.33 for all early removals,patients, and the procedure may be associated with removal of impacted disease-free teeth, andpotential risks from post-operative complications, removal of impacted teeth with disease,such as nerve damage. respectively. The central estimates of costs, presented as the cost per person if that strategyTulloch and Antczak-Bouckoms (1987)61 were universally adopted, were $247 for all earlyThree strategies of the management of lower third extractions, $66 for extractions of impacted teethmolars were evaluated by Tulloch and Antczak- only, and $46 for extractions of impacted teethBouckoms:61 with pathology. These findings maintained a similar pattern under best- and worst-case• removing all disease-free third molars before scenarios. Here the best-case scenario was “under their complete root formation the assumptions of least severe impactions, lowest• removing only those teeth that remain chance of pathology, and lowest disability and cost impacted associated with the outcome”. The worst-case• removing only those impacted teeth that had scenario was “the most severe impaction type, the associated pathology. greatest chance of pathology, and the highest estimates of disability and cost”.The probabilities of complications associated withremoval (pain, swelling, bruising, and malaise) Brickley and colleagues (1995)26were subjectively estimated by nine surgeons. In the analysis by Brickley and colleagues,26 patient-The DSD associated with various complications derived utility values were used to measurewere estimated by 46 clinicians. The results suggest patients’ well-being following one of two strategiesthat “the strategy of removing only pathologically for the management of lower third molars: (1)involved impacted third molars is generally the removing all impacted third molars; (2) norisk-minimising option”. intervention or conservative treatment. The estimated probabilities of outcomes were based onThis decision analysis considered the expected a literature review15 and data from an audit,disability following surgical removal of third molars conducted by the authors, of 300 consecutivebut did not consider disability associated with patients with third molar problems. The resultspathological changes of retained third molars. showed that the maximum expected utility of non-The findings of this study may be questionable extraction (76.96) was better than that forbecause the estimated values of input parameters prophylactic third molar surgery (60.25). Results of(utility and probabilities) were based on the a sensitivity analysis suggest that the outcome ofsubjective judgements of clinicians, or were based non-extraction will be better than that ofon poor quality literature. However, the authors prophylactic third molar surgery unless the risk ofused sensitivity analysis to test a wide range of disease with no extraction, relative to the riskassumptions and found that the model is sensitive shown by the clinical audit and literature review, is:to the severity of the outcome “when these valuesbecome rather extreme”. • 52% higher for pericoronitis • 29% higher for resorption of an adjacent toothTulloch and colleagues (1990)62 • 32% higher for loss of the adjacent tooth dueThe decision analysis carried out by Tulloch and to cariescolleagues62 was similar to the analysis by Tulloch • 43% higher for anterior incisor crowdingand Antczak-Bouckoms61 in terms of the structure • 34% higher for cystic change.and estimates of input parameters. However, italso included the costs of different strategies. Edwards and collegues (1999)60Clinicians’ reported fees and patient records were The decision analysis by Edwards and colleagues60used to estimate the cost of the surgical procedure, was similar to that by Brickley and colleagues,26and the cost (1985 US dollars) of treating any using the same structure (decision tree) and apathological changes associated with third molars similar approach for estimating utility values andor complications of surgery. probabilities of outcomes. This decision analysis estimated and compared cost and cost-effectivenessThe results of this analysis suggested that the of different strategies. In addition, the probabilitiesoptimal strategy was to remove only impacted third of various outcomes were estimated by an up-dated 7
Results literature review (1966–98), and the values of the studies by Brickley and colleagues26 and by utility were estimated by patients who attended Edwards and colleagues.60 Decision analyses by the oral surgery clinic at the University of Wales Tulloch and colleagues62 and by Edwards and Dental Hospital. colleagues60 included the costs of different strategies. The average NHS cost was estimated as £170 for mandibular third molar retention, and £226 for Was an explicit and sensible process used surgical extraction, resulting in a marginal cost of to identify, select and combine the evidence –£56. The effectiveness of mandibular third molar into probabilities? management was rated as being greater for third The probabilities of various outcomes were molar retention (69.5) compared with surgical estimated by using subjective judgement of removal (63.3), giving a marginal effectiveness of clinicians,61 an audit of patients with third molar 6.2. The incremental ratio of cost to effectiveness problems,26 and literature reviews.26,60–62 Although for retention compared with removal was therefore the process was explicitly described and seemingly negative (–£56/6.2 = –£9.03 per extra unit of sensible, details were often not available in the effectiveness). That is, mandibular third molar published decision analyses. retention was less costly and more effective than prophylactic removal of disease-free third molars. The risk of pathological changes associated with third molars may have been overestimated in the A sensitivity analysis indicated that this finding decision analyses when the proportions of patients was sensitive to changes in the probability of with symptomatic impacted third molars were used pericoronitis, periodontal disease and caries. to estimate the incidence of pathological changes The most cost-effective strategy would alter from among the total population with impacted third retention to removal if the probability of molars. On the other hand, probabilities of pericoronitis increased from 22% to 40%, the complications following third molar surgery were probability of periodontal disease increased from estimated by including patients undergoing 5% to 17%, or the probability of unrestorable caries prophylactic and non-prophylactic third in the second molar increased from 10% to 22%. molar surgery. Are the results of the decision Were the utilities obtained in an explicit and analyses valid? sensible way from credible sources? The validity of these decision analyses should be The methods used to obtain utility values were examined to decide whether their findings are explicitly described in these decision analyses. The believable. According to guidelines about using values of utilities were estimated by clinicians in clinical decision analysis, the following questions one study by Tulloch and Antczak-Bouckoms,61 and need to be addressed:95 by patients in the decision analyses by Brickley and colleagues (1995).26 The patient-derived utility • were all important strategies and outcomes used in the decision analyses by Brickley and included? colleagues26 and Edwards and colleagues60 seems • was an explicit and sensible process used to more relevant and appropriate than the clinician- identify, select, and combine the evidence into estimated utilities used in other studies. probabilities? • were the utilities obtained in an explicit and Was the potential impact of any uncertainty in sensible way from credible sources? the evidence determined? • was the potential impact of any uncertainty in The potential impact of uncertainty in the the evidence determined? evidence was tested by sensitivity analyses in all four decision analyses. According to the results of Were all important strategies and outcomes sensitivity analyses, findings were quite robust. The included? conclusions will alter only when the severity of the The strategies compared in these decision analyses outcome or the probability of some disease seem appropriate. Prophylactic removal of changes considerably. impacted third molars was compared with retention of disease-free third molars. In the Time horizon analyses by Tulloch and colleagues61,62 only Perhaps the major weakness of these decision complications following removal of third molars analyses is that they were not able to consider were considered. The outcomes of retention and the impact of time span on the outcomes. The8 removal of impacted third molars were included in outcomes following surgical removal of third
Health Technology Assessment 2000; Vol. 4: No. 15molars occur early and are mainly short-term by the decision analyses may be relevant andevents (except permanent sensory nerve important in relation to decision-making for thedamage or other rare complications), whereas management of impacted third molars. Havingthe outcomes associated with retention of disease- said that, it should be stressed that these decisionfree third molars may occur in later life and can analyses were mainly based on research evidenceonly be fully measured with a long-term follow-up. from primary studies that had a poor qualityPatients’ time preference and the impact of long- of design.term outcomes may not have been fully incorp-orated into the decision analyses. Cost and cost-effectivenessThe cumulative probabilities of various pathologicalchanges associated with impacted third molars may analysis of prophylactic removalincrease with a longer duration of follow-up, of third molarsshifting the model more towards favouringextraction. On the other hand, the advantages of According to data reported in Extraction of wisdomretention of disease-free third molars may be teeth: submission of evidence to NICE (by the Facultyenhanced because of the effect of discounting the of Dental Surgery of The Royal College ofcosts and/or disability which might be expected to Surgeons of England), in 1995–96 the totaloccur at a more distant time, shifting the model number of third molar teeth removed was 121,577more towards favouring retention.62 (upper 42,578; lower 78,999), at a total cost of £11.8 million to the NHS General Dental ServicesThe usefulness of conventional decision analysis (England & Wales).98 Therefore, the average costis limited when it is used to study clinical decisions per third molar removed can be estimated asthat have long-term implications. When probability £97.06. According to the initial report of the UKand utility variables change over time, Markov National Third Molar project,10 43.9% of the thirdprocess analysis can be used but the modelling molars removed in 1995 were disease-free.becomes much more complicated.96 Markov Therefore it is possible to estimate that the totalmodelling has been used, for example, to simulate number of third molars removed prophylacticallythe eruption of lower third molars.97 A more in 1995–96 was about 53,372 each year in the NHScomplex Markov model may be helpful to explore General Dental Services (England & Wales) with along-term outcomes of prophylactic removal total cost of about £5.2 million. This estimated costcompared with retention of impacted third molars. should be interpreted with caution. It is possible that the data reported are inaccurate, and detailsSummary of decision analyses about cost are not available. In addition, theAlthough there were important differences in Faculty of Dental Surgery of the Royal College ofthe structure and methods for estimating input Surgeons of England suggests that current rates ofvalues, the findings of the decision analyses (by prophylactic removal are about 4%, much lowertwo groups of researchers) consistently indicated than the previous estimates. However, this needs tothat patients’ well-being is maximised if surgical be confirmed.removal is confined to impacted third molars withpathological changes. Retention was the most The decision analysis by Edwards and colleaguescost-saving and cost-effective strategy compared estimated cost-effectiveness of removal andwith prophylactic removal of all impacted retention of disease-free third molars.60 The costthird molars.60,62 to the NHS included consumables, staff costs, and overheads. The average cost (not discounted)These decision analyses made it possible to of the prophylactic removal of an impactedcompare different outcomes directly in the mandibular third molar was about 33% highercoherent models. The utility values and than the cost of retention (£226 comparedprobabilities of various outcomes were explicitly with £170).presented. The uncertainty of input values wastested. Since there are no controlled studies The compensation awarded for permanent nervecomparing long-term outcomes of retention with damage after third molar surgery ranges fromoutcomes of prophylactic removal of impacted £5000 to £14,000 per case or higher.99third molars, the recommendations provided 9
Health Technology Assessment 2000; Vol. 4: No. 15 Chapter 4 Discussion and conclusions these literature reviews ranges from nine to 149. InQuality of available evidence our 1996 review of 12 literature reviews ofThe appropriateness of prophylactic removal impacted third molars we found that reviews withof impacted third molars should be evaluated by similar aims included different sets of studies ascomparing the outcomes of prophylactic removal evidence from which to draw conclusions.23 Forwith the outcomes of retention. One difficulty in example, 69 studies were quoted overall in ninethe comparison of the two strategies lies in general reviews to discuss the association betweenvaluing and comparing the various outcomes. disease and third molars. None of these 69The outcomes of surgical removal of impacted references was used by more than five literaturethird molars are assessed by the rate of various reviews. One study was quoted in five reviews,complications. On the other hand, the whereas 43 studies were included in only oneconsequences of deliberate retention of impacted review. This discrepancy in the use of relevantthird molars without disease will include the studies cannot be explained by the year ofincidence of different pathological changes and publication or by any other acceptable reason.the rate of complications following delayedsurgical removal. To be directly comparable, the The identified literature reviews included primaryoutcomes of the two strategies need to be studies with various designs such as retrospective orsummarised by a common method, for example prospective observational studies and case reports.DSD or utilities. The relevance and quality of primary studies was inadequately assessed in the majority of cases.RCTs Sufficient details of the included primary studiesOne RCT examined the effects of early extraction were not presented and the interpretation ofof third molars on late lower incisor crowding.24 primary studies may not be valid. For example,It concluded that the removal of third molars to some reviews used the proportion of patientsreduce or prevent late incisor crowding cannot be undergoing third molar surgery to estimate thejustified. The preliminary results reported in an incidence of disease among populations. Thisabstract describing another RCT, which aims to approach may overestimate incidence considerably.compare the effects and costs of prophylactic third In addition, when the incidence was reported, themolar removal with those of removal according to duration of follow-up was sometimes unclear in themorbidity, suggested that watchful waiting may be reviews. Since the quality of studies was not appro-a promising strategy but acknowledged that more priately assessed, and sufficient details of studiesdata and longer follow-up of patients are needed were not presented, it is difficult to distinguish poorto identify the most cost-effective strategy.29 quality data from more reliable evidence providedAdditionally, a prospective multi-centre RCT has in these reviews.been commissioned in the USA, and results areawaited with interest. This RCT aims to compare These literature reviews seldom quantitativelyremoval with retention of third molars in terms summarised the risk associated with removal orof clinical, biological, and health-related quality retention of impacted third molars. It is difficultof life outcomes. It is planned to compare these to draw a balanced conclusion about the appro-outcomes across patient groups stratified by age, priateness of prophylactic third molar removal,gender, and race.98 partly because of the different outcomes of retention and removal that are used. ConsideringLiterature reviews the complexity of the relevant issues and a lack ofThe general quality of the literature reviews good objective evidence, it is perhaps unsurprisingidentified is quite poor. Since authors did not that the majority of reviews provide uncertainexplicitly describe review methods such as the recommendations. However, it appears thatsearch strategy and criteria for inclusion of literature reviews which conclude that prophylacticindividual studies, they might have selectively removal is inappropriate are of betterincluded those studies that supported their own methodological quality than many other reviewsopinion. The total number of references used in (appendix 3). 11
Discussion and conclusions Decision analyses Conclusions Several decision analyses made it possible to compare different outcomes directly in the There is no reliable research evidence to support coherent models. The utility values and the prophylactic removal of disease-free impacted probabilities of various outcomes were explicitly third molars. Available evidence suggests that presented. The uncertainty of input values was retention may be more effective and cost-effective tested. Since there are no controlled studies than prophylactic removal, at least in the short to comparing long-term outcomes of retention medium term. and outcomes of prophylactic removal of impacted third molars, the recommendations provided by the The results of two ongoing RCTs, one based in decision analyses may be relevant to the decision- Denmark29 and one in the USA, are awaited making process relating to the management of with interest. impacted third molars. However, it should be stressed that these decision analyses were mainly Recommendations for research based on research evidence from primary studies 1. Although data from observational studies may that were of poor design quality. be useful, there is a need for well-designed RCTs to compare prophylactic removal with Although there were important differences in management by deliberate retention, using the structure and methods for estimating input long-term follow-up. values, the findings of the decision analyses (by two groups of researchers) consistently 2. There is also a need for decision analysis indicated that patients’ wellbeing is maximised models that could be used to compare long if surgical removal is confined to those impacted term outcomes of prophylactic removal with third molars associated with pathological changes. retention of impacted third molars. Retention was the most cost-saving and cost- effective strategy compared with prophylactic removal of all impacted third molars.60,6212
Health Technology Assessment 2000; Vol. 4: No. 15 AcknowledgementsT he project team would like to thank The Faculty of Dental Surgery of the Royal Collegeof Surgeons of England and The British Dental We are indebted to the referees for their perseverance in reading the report and the quality of their comments.Association, for providing additional informationas submission of evidence to NICE. We would also The views expressed in this report are those of thelike to thank the Scottish Intercollegiate Guide- authors, who are also responsible for any errors.lines Network for providing us with a draft copyof their forthcoming guidelines. 13
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