Description of the condition
Anxiety towards dental treatment is widespread in the population. The latest adult dental health survey in the UK reported that 36% of participating adults had moderate dental anxiety and 12% extreme dental anxiety (NHS information Centre 2010). It is also a global problem, although published figures vary throughout the world. It is also possible that much severe anxiety goes unreported as sufferers may not attend the dentist due to their fear. Dental anxiety and fear of dentistry can be considered facets of the same problem and the terms can be used interchangeably in both lay and scientific discourse.
Dental anxiety is unpleasant for sufferers. There are physical, psychological and behavioural consequences of anxiety and it may lead to neglect of the dentition. Physical effects include shaking, sweating and increased heart rate, sometimes at the thought of dental treatment. Psychological effects include feelings of low self esteem, shame, fear etc. Behavioural changes include the avoidance of dental appointments and in severe cases sufferers may avoid mention of dentists in television, film, newspapers and conversation.
For dental care professionals anxious patients are an important cause of stress as it is often difficult to provide treatment for such individuals. In addition, anxiety may lead patients to cancel their appointments or simply fail to attend their appointments on the day.
Both pharmacological and psychological approaches to overcoming fear of dental treatment are widely reported in the literature, but no one approach is acceptable or applicable to all (de Jongh 2005). Behavioural methods have been shown to be effective and there is some evidence that long term improvement is more likely in patients who receive such methods compared to those who receive pharmacological interventions (Aartman 2000).
Description of the intervention
Hypnosis has been proposed as a potential mode of treatment in the alleviation of dental anxiety and has been used by dentists since the first reports of tooth extraction under hypnosis in the 1800s. Hypnosis in dentistry has been used in many ways. These include as a method of pain control, to control or reduce anxiety towards treatment, to treat dental and needle phobia and to assist in changing habits detrimental to oral health such as smoking (Simons 2007).
According to the British Psychological Society:
"The term 'hypnosis' denotes an interaction between one person, the 'hypnotist', and another person or people, the 'subjects'. In this interaction the hypnotist attempts to influence the subjects' perceptions, feeling, thinking and behaviour by asking them to concentrate on ideas and images that may evoke the intended effects. The verbal communications that the hypnotist uses to achieve these effects are termed 'suggestions'. Suggestions differ from everyday kinds of instructions in that they imply that a 'successful' response is experienced by the subject as having a quality of involuntariness or effortlessness. Subjects may learn to go through the hypnotic procedures on their own, and this is termed 'self hypnosis'" (page 3) (British Psychological Society 2001).
How the intervention might work
Hypnosis has been used to treat anxiety in many contexts not just dentistry. It has been evaluated as an adjunct to cognitive behavioural therapy and considerable benefit was demonstrated in a number of conditions with obesity studies having the largest effect sizes in one meta-analysis (Kirsch 1995) and long term follow-up (Schoenberger 2000). Benefit has also been demonstrated in anxiety disorders, although further well designed studies are needed (Schoenberger 2000).
There may be a number of mechanisms by which hypnosis could relieve anxiety about dentistry. These may be specific to hypnosis or non-specific effects of the therapeutic situation using hypnosis.
- During dental treatment, hypnotic suggestions for relaxation may ameliorate anxiety by reducing autonomic arousal. Hypnotic relaxation is used here in a similar way to reciprocal inhibition (Wolpe 1958).
- Hypnosis is dependent upon good rapport between hypnotist and subject and the dentist/patient relationship is an important modifying factor in anxiety, a poor relationship increasing the likelihood of a patient becoming anxious. In a survey of Danish adults, anxious people were more likely to have negative experiences of dentists' behaviours (Moore 1993).
- Hypnotic procedures could make dental treatment more acceptable which may challenge patient's negative beliefs about dentistry. This could include using techniques aiming to help patients to reformulate memories of traumatic experiences of dental treatment with the help of appropriate intervention by the therapist (British Psychological Society 2001).
- Fear of pain is one of the reasons that patients may be anxious and hypnosis is a well established method of pain control (Montgomery 2000).
- Hypnosis can potentiate the use of imagery and can be used as an adjunct to techniques such as systematic desensitisation, modelling and other behaviour modification techniques (Simons 2007).
- People having hypnotic experiences such as pain sensation show patterns of brain activity closely corresponding to those found when the person has the same experience in reality. It is possible that suggestions to experience other effects, for example relaxation and comfort may reduce anxiety in similar ways (Derbyshire 2004).
Why it is important to do this review
There is published work on the effectiveness of hypnosis as a treatment for dental anxiety, including clinical trials comparing hypnosis to other behavioural methods and to normal treatment protocols (for example Eitner 2006; Hammarstrand 1995; Moore 2002) but so far, the evidence for its effectiveness has not been subject to systematic review. As the public become more interested in complementary approaches in health care in general it becomes more important than ever that evidence is evaluated.
Hypnosis is regarded as a benign procedure. It is recommended that it is used within the expertise of the hypnotist - hypnosis should only be used to treat conditions that the professional would treat without hypnosis. In addition, the British Psychological Society recommends that only those with considerable experience in treating such patients should use it with psychotic patients (British Psychological Society 2001).
Many researchers contend that hypnosis cannot evoke psychotic states such as schizophrenia and that a minority of people report such things as headaches, dizziness, nausea or stiff necks, with a much larger percentage reporting positive effects (Lynn 2000).
However, there are documented instances of adverse effects of the use of hypnosis in clinical and experimental contexts. Most are mild and of short duration, but practitioners should have appropriate training in order to recognise and deal effectively with such occurrences (Gruzelier 2000).
Costs to the patient will vary according to the healthcare system in place, but one US study showed that using hypnosis as an adjunct to sedation may reduce costs (Lang 2002).
Hypnosis is of international interest, the International Society of Hypnosis (ISH) has constituent societies in 19 countries worldwide (ISH 2013).
A similar review of hypnosis in dentistry for children has recently been published (Al-Harasi 2010), so a corresponding review for adults would be desirable.
To determine the effects of hypnosis (with or without conscious sedation or prior to or following general anaesthesia) in reducing anxiety towards dental treatment.
Criteria for considering studies for this review
Types of studies
Randomised controlled trials (RCTs).
We will exclude cross-over trials.
Types of participants
Participants will be adults seeking or undergoing dental treatment. No restrictions will be placed on trials including patients with co-morbidities including other psychological disorders, however, we will include such factors in the characteristics of included studies to allow a decision to be made on whether this could be a confounder.
Types of interventions
Hypnosis can be used as a stand-alone intervention or as an adjunct to other pharmacological and non-pharmacological treatments for dental anxiety. In order to examine as much evidence as possible both methods of use will be included in this review.
Interventions will be any hypnotic technique with or without the addition of pharmacological sedation or general anaesthesia. The comparisons will be no treatment or usual care, placebo, sedation, general anaesthesia, other behavioural techniques.
As hypnosis can be used as an adjunct to other anxiety reduction techniques, studies will be included in which hypnosis is used adjunctively to other pharmacological and behavioural techniques. In such studies, comparisons will be the technique without the addition of hypnosis.
Trials comparing different types of hypnotic treatment, for example live versus tape recorded hypnosis, will be included.
Trials of hypnosis associated with local anaesthesia will also be included.
Types of outcome measures
- Self reported dental anxiety measured by anxiety scales or state anxiety scales.
- Physiological measures of anxiety (including dental anxiety), heart rate, heart rate variability, blood pressure, skin conductance or any other recognised measure.
It is possible that these may not have been the primary outcome of the study itself as studies often include measurement of anxiety in studies aimed primarily at other dental issues, e.g. pain.
- Ability to accept dental treatment - this may be measured by questionnaire or be indirectly assessed by successful completion of planned dental treatment.
- Patient satisfaction with hypnosis or dental treatment or both.
- Reduction in dosage of any sedative agent used.
- Ease of carrying out treatment - this assessment should be made by the dentist carrying out the dental treatment who may not be the same person as the hypnotist.
- Adverse effects.
Search methods for identification of studies
For the identification of studies included or considered for this review, detailed search strategies will be developed for each database searched. These will be based on the search strategy developed for MEDLINE (Appendix 1) appropriately revised for each database.
We will search the following databases:
- Cochrane Oral Health Group's Trials Register (whole database)
- Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, current issue)
- MEDLINE via OVID (1946 to present)
- EMBASE via OVID (1980 to present)
- PsycINFO via OVID (1806 to present)
- CINAHL via EBSCO (1980 to present)
- AMED via OVID (1985 to present).
The MEDLINE search will combine the subject search with the Cochrane Highly Sensitive Search Strategy for identifying reports of randomised controlled trials (2008 revision) (as published in box 6.4c in the Cochrane Handbook for Systematic Reviews of Interventions version 5.1.0, updated March 2011) (Higgins 2011). The searches of EMBASE and PsycINFO will be combined with the Cochrane Oral Health Group's filters for identifying randomised controlled trials.
Searching other resources
We will search the following databases for ongoing trials:
- ClinicalTrials.gov (http://www.clinicaltrials.gov)
- The metaRegister of Controlled Trials (http://www.controlled-trials.com).
We will handsearch the following journals:
- Contemporary Hypnosis (2000 to present)
- International Journal of Clinical and Experimental Hypnosis (2000 to present)
- American Journal of Clinical Hypnosis (2000 to present)
- Australian Journal of Clinical & Experimental Hypnosis (2000 to present).
The reference lists of all eligible trials will be checked for additional studies. Specialists in the field known to authors will be contacted for any unpublished data.
Data collection and analysis
Selection of studies
At least two review authors will screen the titles and abstracts from the electronic searches to identify potentially eligible studies which require further evaluation to determine whether they meet the inclusion criteria for this review. Full text copies of all eligible and potentially eligible studies will be obtained and these will be further evaluated in detail by two review authors to identify those studies which actually meet all the inclusion criteria. From this group, those studies which do not meet the inclusion criteria will be recorded in the excluded studies section of the review and the reason for exclusion will be noted.
Disagreements will be resolved by discussion.
We will include all studies meeting the selection criteria in this review regardless of quality.
Articles in languages other than English will be assessed by their abstracts, where possible, and if they appear to be potentially eligible, the full text of the article will be translated.
Data extraction and management
Two review authors will extract information relevant to the objectives and outcome measures into a specially designed data extraction form independently and in duplicate. Any disagreements will be resolved by discussion. We will not be blinded to the journal of publication or the author(s) of the paper.
The following data will be extracted.
- Study design: RCT - number of arms.
- Conducted in (country).
- Number of centres.
- Recruitment period.
- Funding source.
- Inclusion criteria.
- Exclusion criteria.
- Number of patients randomised.
- Number of patients evaluated.
- Treatment interventions including methods and duration.
- Control interventions including methods and duration.
- Numbers of patients in each group.
- Primary outcomes of trial and time(s) measured.
- Secondary outcomes of trial and time(s) measured.
- Was there a sample size calculation.
- Duration of follow-up.
- Comparisons at baseline.
- Any other issues.
Assessment of risk of bias in included studies
All studies meeting the selection criteria will be included in this review regardless of quality.
Risk of bias will be assessed using the methodology set out in chapter 8 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).
Included trials will be assessed for.
- Random sequence generation.
- Allocation concealment.
- Blinding of participants and personnel (although it is recognised that this may not be possible due to the nature of the interventions). Judgement will be made as to whether non-blinding would affect the outcome and therefore constitute a risk of bias even where blinding is not possible.
- Incomplete outcome data.
- Selective reporting.
- Other sources of bias.
Trials will be assessed for risk of selection bias and allocated to one of the following groupings.
- Low risk of bias - adequate concealment of the allocation (e.g. sequentially numbered, sealed, opaque envelopes or centralised randomisation).
- Unclear risk of bias - uncertainty about whether the allocation was adequately concealed (e.g. where the method of concealment is not described or not described in sufficient detail to allow a definite judgement).
- High risk of bias - inadequate allocation concealment (e.g. investigators knew in advance what the allocated assignment of the next participant would be).
For performance bias, judgement will be made on whether blinding of participants and study personnel is possible and if not, whether this produces a low, high or unclear risk of bias.
Detection bias in trials of hypnosis has similar issues, it is not always possible to blind outcome assessors to the intervention provided. Judgement will be made as above for performance bias.
Attrition bias will be addressed by examining missing data and drop-outs from the trials and reported as above using the criteria in chapter 8 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).
Selective reporting will be assessed and reported using the criteria in chapter 8 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).
Other sources of bias will be assessed as above.
Measures of treatment effect
Levels of anxiety measured by anxiety scales will be treated as continuous data and will be reported as mean and standard deviations.
Physiological measures will be considered similarly.
Dichotomous outcomes are possible such as completion of planned treatment or adverse effects. Adverse effects will be reported as number occurring with a risk ratio if necessary. Completion or not of planned treatment will be reported as a risk ratio.
Unit of analysis issues
It is likely that studies will have used heterogenous outcome measures including a variety of different scales.
It is unlikely that cluster randomised trials or multiple arm studies exist in this area, but repeated measures are commonly used. In these cases several different outcomes will be defined, based on different times of measurement and analysed separately as recommended by chapter 9 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).
Dealing with missing data
Trial authors will be contacted to attempt to retrieve missing data where necessary.
Assessment of heterogeneity
Heterogeneity in the results of trials will be assessed where appropriate, by inspection of a graphical display of the results and by formal tests of heterogeneity. Sources of heterogeneity are anticipated to be patient characteristics, outcome measures and the nature of the intervention and control groups.
Assessment of reporting biases
If there are sufficient numbers of trials, publication bias will be assessed according to the recommendations on testing for funnel plot asymmetry as described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).
We will only conduct a meta-analysis if there are studies of similar comparisons reporting the same outcome measures. We will combine risk ratios for dichotomous data and mean differences for continuous data using fixed-effect models unless there are more than three studies in the meta-analysis.
Subgroup analysis and investigation of heterogeneity
Subgroup analysis may be carried out if sufficient data are available based on:
- initial anxiety levels on outcomes (e.g. dental phobia versus dental anxiety)
- the effect of the addition of hypnosis to sedation
- the effects of different dental treatments (e.g. oral surgery versus restorative treatment)
- the use of local anaesthetic versus no local anaesthetic.
Providing there are sufficient included trials, sensitivity analysis based on studies at low risk of bias will be undertaken.
Presentation of main results
A summary of findings table will be developed for the primary outcomes of this review using GRADEPro software. The quality of the body of evidence will be assessed with reference to the overall risk of bias of the included studies, the directness of the evidence, the inconsistency of the results, the precision of the estimates, the risk of publication bias and the magnitude of the effect. The quality of the body of evidence for each of the primary outcomes will be categorised as high, moderate, low or very low.
Appendix 1. MEDLINE (OVID) search strategy
1. exp Dentistry/
2. (dental$ or dentist$ or "oral surg$" or orthodont$ or pulpotom$ or pulpect$ or endondont$ or "pulp cap$").mp.
3. ((dental or tooth or teeth) and (fill$ or restor$ or extract$ or remov$ or "cavity prep$" or caries or carious or decay$)).mp.
4. ("root canal therapy" or "root canal treatment” or “endodontic$").ab,sh,ti.
5. ((dental adj3 implant$) or (tooth adj3 replant$")).ab,sh,ti.
6. 1 or 2 or 3 or 4 or 5
7. Hypnosis, Dental/
8. exp Hypnosis/
9. exp Hypnosis, Anesthetic/
10. "Imagery (Psychotherapy)"/
11. Relaxation Therapy/
12. (autosuggestion or auto-suggestion).mp. [mp=title, original title, abstract, name of substance word, subject heading word, unique identifier]
14. "autogenic$ train$".mp. [mp=title, original title, abstract, name of substance word, subject heading word, unique identifier]
15. 7 or 8 or 9 or 10 or 11 or 12 or 13 or 14
16. 6 and 15
The above subject search will be combined with the Cochrane Highly Sensitive Search Strategy for identifying reports of randomised controlled trials (2008 revision) (as published in box 6.4.c in the Cochrane Handbook for Systematic Reviews of Interventions version 5.1.0 updated March 2011) (Higgins 2011).
1. randomized controlled trial.pt.
2. controlled clinical trial.pt.
5. drug therapy.fs.
10. exp animals/ not humans.sh.
11. 9 not 10
Contributions of authors
Catherine Potter, Paul Coulthard, Richard Brown and Tanya Walsh wrote the protocol and will complete the review (protocol draft, acquisition of trial copies, trial selection, data extraction, data analysis, data interpretation, review draft and update draft).
Declarations of interest
Catherine Potter: no interests to declare.
Paul Coulthard: no interests to declare.
Richard Brown: no interests to declare.
Tanya Walsh: no interests to declare.
Sources of support
- The University of Manchester, UK.
- Manchester Academic Health Sciences Centre (MAHSC), UK.The Cochrane Oral Health Group is supported by MAHSC and the NIHR Manchester Biomedical Research Centre
- Cochrane Oral Health Group Global Alliance, UK.All reviews in the Cochrane Oral Health Group are supported by Global Alliance member organisations (British Orthodontic Society, UK; British Society of Paediatric Dentistry, UK; Canadian Dental Hygienists Association, Canada; National Center for Dental Hygiene Research & Practice, USA and New York University College of Dentistry, USA) providing funding for the editorial process (http://ohg.cochrane.org/)
- National Institute for Health Research (NIHR), UK.CRG funding acknowledgement:
The NIHR is the largest single funder of the Cochrane Oral Health GroupDisclaimer:
The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the NIHR, NHS or the Department of Health