Frequently asked questions

Information about the Modified Dental Anxiety Scale (MDAS).

What is dental anxiety?

Dental anxiety is an aversive psychological response to a poorly defined, or not immediately present dental stimulus interpreted as potentially harmful or dangerous, usually within a dental context. This definition is distinct from dental phobia which is characterised essentially as an individual who avoids dental treatment and can be recognised with the following criteria: a marked and persistent fear of the specific object or situation that is excessive or unreasonable, an immediate anxiety response upon exposure to the feared stimulus, which may take the form of a panic attack, recognition that the fear is excessive or unreasonable, avoidance of the anxiety-producing situation, interferes with normal functioning or causes marked distress.

Why choose MDAS to assess dental anxiety?

There are twelve reasons for selecting the MDAS to assess dental anxiety, namely:

  1. Quick to complete, 
  2. Widely used in survey, experimental and clinical studies, 
  3. Reliability found to be favourable in the UK and other national samples, 
  4. Evidence for validity, such as relates well to other measures of dental anxiety, and related constructs 
  5. Identical answering scheme for each question making comparisons simple, 
  6. Functions well as a screening tool, 
  7. Acceptability in respondents is high and does not raise anxiety in patients prior to their dental appointment (no significant instrumentation effect). 
  8. Numerous translations in other languages available, 
  9. Conversion tables with Corah’s Dental Anxiety Scale available (both directions), 
  10. Cut-off determined for extreme dental anxiety (from clinical evidence and comparison with DSMIV criteria), 
  11. Ability to compare with numerous other published studies, 
  12. Norm referenced with UK representative samples.
Do I need permission to use the Modified Dental Anxiety Scale?

No. The MDAS is freely available. Please quote the source of the measure which is:

HUMPHRIS GM, MORRISON T and LINDSAY SJE (1995) 'The Modified Dental Anxiety Scale: Validation and United Kingdom Norms' Community Dental Health, 12, 143-150.

I am not sure whether I want to measure dental anxiety with the MDAS. There seems to be a number of measures available?

All researchers have the challenge to select the measure that best reflects their interest and research question. There are a number of measures available. Dr Stan Lindsay and I were dissatisfied with the original Corah version of the Dental Anxiety Scale for number of reasons (early 1990’s), including: the answering scheme was not standard across the question items, the categories were not in consistent rank order (i.e. tense and anxious can be reversed according to some respondents) and there was no question about local anaesthetic. The later appeared an omission because a major feature of dental anxiety for many respondents is the ‘needle’.

You should inspect other measures of Dental Anxiety and decide which is correct for your study. The MDAS has advantages as can be seen in the list of 12 reasons to select this measure. No measure is perfect and one issue is that the MDAS is brief. There are measures that have greater length and go into greater detail than the MDAS. In addition the MDAS is merely a catalogue of respondent’s views to typical situations in the dental environment and does not attempt to reflect a theoretical position.

So make a selection of the measure that best fits your research question. You are advised not to design a new measure unless you are dissatisfied with what is available in the literature. The work involved is considerable.

What is the scoring procedure for the MDAS?

Simply sum the scores of the five items which have been coded from 1 to 5 (not anxious to extremely anxious respectively). You should get a scale that ranges from a minimum of 5 to a maximum of 25.

Sometimes a respondent will not reply to some of the items. What do you recommend to do with missing data?

You can calculate a mean score based upon the remaining scores as long as no more than one item on the five-item scale is missing. You may consider that you can cope with 2 items missing but bear in mind that your score then depends on almost a proxy of only just over half of the data being present.

For a single item pro-rating you can use the SPSS command: COMPUTE MDAS = Mean.4 (MDAS1, MDAS2, MDAS3, MDAS4, MDAS5).

Other methods can be considered which require specialist advice such as regression, hot deck, or multiple imputations techniques such as MCAR.

What are the norms of the MDAS?

The original paper by Humphris et al (1995) presented some norms for different samples in the UK. More recently this has been updated for UK and can be accessed free in an Open-Accessed journal (see publication list) or use this link: http://www.biomedcentral.com/1472-6831/9/20.

Is the scale one-dimensional?

This feature of psychological measures refers to the psychometric property of assessing a hypothetical construct that is essentially measuring a single property. An analogy would be that you are assessing length with a metre rule and not some other quality at the same time. The MDAS has been shown to be a one-dimensional scale. This is not surprising as it consists of only 5 question items. However please be aware that in some samples and cultures the scale may behave differently and it is worth examining the one-dimensional characteristics of the MDAS by conducting your own analysis of the data you collect. For example you can in SPSS conduct an explorative factor analysis and see if your data will be described as consisting of a single factor. More sophisticated data analysts will want to conduct confirmatory factor analysis (use AMOS, EQS, LISREL, MPLUS or the new STATA12 packages). Models can be applied that can force the scale to be described as two factors. A Chinese sample collected in Beijing was best interpreted as a two factor measure consisting of anticipatory (MDAS1 and MDAS2) and treatment (MDAS3, MDAS4 and MDAS5) sub scales.

Is there a point along the scale that could be considered as a cut-off?

This in some ways is controversial as the construct of dental anxiety is a continuum. Hence trying to fix a point along the scale is far from easy in which a researcher might consider a person to be very dentally anxious. From a practical point of view however it is sometimes helpful to be alerted that if someone scores at or above a certain level then that person could be considered as satisfying a certain profile or requires some assistance. This is very much a clinical decision and the clinician who wishes to use the MDAS in this way should be aware that the measure is an approximation and not a hard and fast decisional aid. The current cut-off is 19. Therefore those that score at or above this score would be considered as ‘very dentally anxious’. The likelihood of being dentally phobic is hard to determine as dental phobics would prefer not to complete such a measure and therefore we do not have a good evidence base. Suffice to say that the MDAS is the only dental anxiety measure to date that has based its cut-off (for very dentally anxious patients requiring extra clinical attention by the dental member of staff) on a clinical sample (Humphris et al 1995) and also with a large community sample (King and Humphris, 2010).

I have collected my data using the Corah version of the Dental Anxiety Scale. Can I compare my scores with MDAS values?

 Yes. There are Conversion Tables and SPSS routines available to perform this set of calculations. You can also do the reverse (i.e. convert MDAS to CDAS scores).

See the reference of Freeman et al (2007) for details.

Professor Gerry Humphris, University of St Andrews
Medical and Biological Sciences Building, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9TF.

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