Mouth alcohol

By Anna Sandiford 14/03/2011 3

Can dentures make a breath reading higher than it should be? In short, yes. It’s a query I had last week from a solicitor and it’s one I’ve had several times over the years.
Alcohol can become lodged under the plate of dentures and remain there as a ‘reservoir’, with alcohol fumes evaporating into the mouth cavity over a period of time. When someone is asked to provide a breath sample to a breath testing device, they blow air from their lungs into the testing device. If the person has been drinking alcohol, alcohol absorbed into the blood is transferred into the breath through the lungs (via the alveoli) – measuring the alcohol concentration from the base of the lungs is the basis of evidential breath testing instruments, hence why you are required to provide a long, deep breath to the testing device.
If alcohol is present in the mouth for some reason, this can also be introduced into the breath testing device at the time of any test and can contribute to the breath an amount of alcohol that is not related to the blood alcohol concentration. This can therefore result in an artificially high reading.
Such additional alcohol can come from, amongst other sources, alcohol stored (albeit temporarily) in dental plates and other mouth items. However, this effect doesn’t last forever and is known to dissipate over a relatively short period of time.
In countries overseas, there is a mandatory stand-down period between the time that a person is asked by Police to provide a breath alcohol sample to an evidential tesing device and the time that they actually provide that sample. The reason for this is to allow any potential mouth alcohol effects (not just relating to dentures) to dissipate. However, New Zealand does not have such a mandatory stand-down period. The chances of a mouth alcohol effect therefore increase.
In these situations, knowing the case circumstances and timeline is vital – a copy of the breath testing printout should also provide some clues as to whether a mouth alcohol effect could have adversely affected a breath alcohol reading. If the breath reading is not reliable then it should not be accepted in court.

3 Responses to “Mouth alcohol”

  • The short answer to the question that dentures can make a breath alcohol test higher than it should be, is no not yes. Dentures do not act as a deposit for alcohol. The mouth alcohol effect disappears within fifteen minutes for individuals with dentures as it does for individuals who do not have dentures. (Kempe, C.R., “Study of the dissipation rate of ethanol from the oral cavity”, Law and Order, 20(9): 94, 1972; Harding, P.M., et al., “The effects of dentures and denture adhesives on mouth alcohol retention”, J. Forensic Sci., 37(4): 999-1007, 1992; Katzgraber, F., et al. “Dentures: A deposit for alcohol?”, Blutalkohol, 32: 274-278, 1995)

    There would be no mouth alcohol effect in breath tested individuals (with or without dentures) in which there is a 15 minute period of time after the last alcoholic drink was consumed. Additional safeguards are duplicate breath tests with proper agreement and the slope/mouth alcohol detectors that many evidential instruments have.

    Even though New Zealand has no mandatory fifteen minute “stand-down” period, a recent large and detailed study of 11,837 drivers showed no evidence of mouth alcohol causing falsely high breath test results compared to the actual blood alcohol concentration (Stowell, A.R., et al. “New Zealand’s breath and blood alcohol tesing programs: further data analysis and forensic implications” Forensic Science International, 178: 83-92, 2008). This is probably due to the fact that few drivers are drinking just before the police stop them and the usual delay in processing the arrested driver before the evidential breath test is conducted.

    It is also interesting to note Canada also has no mandatory fifteen minute “stand-down” time.

    • Thank you for your comment. As you say, the 15 minutes should be enough for any mouth alcohol effect, whatever the cause, to dissipate. The breath testing devices should indeed be able to detect a breath difference from mouth alcohol and also should be able to detect interfering substances by virtue of the alcohol curve and internal detectors.
      Unfortunately, some of the evidential breath testing devices in use in New Zealand do not flag up breath differences/interfering substances and in cases where there have not been 15 minutes between the time a breath request was made and samples were provided then breath results can be adversely affected: I had a case at the end of last year with exactly this situation where the first breath result was 900+ and the second, 2 minutes later, was approx 440 – the device did not report either a breath difference or an interfering substance issue. Although is not common, it does occur. The study by Stowell et al may not pick up such cases because the driver may not have elected to provide a blood sample.

  • Your case report illustrates the third safeguard against mouth alcohol. The fifteen minute wait did not occur, the breath alcohol device either did not have a mouth alcohol detector or the slope detector didn’t pick up mouth alcohol, but the third safeguard of duplicate breath alcohol tests showed mouth alcohol. The result of 900+ followed by a result of 440, two minutes later indicates mouth alcohol, for there is a rapid exponential drop of the mouth alcohol effect.

    You are correct in that the slope or mouth alcohol detector will not always pick up the mouth alcohol effect as I have published in several studies (Wigmore, JG, and Leslie, GM, The Effect of Swallowing or Rinsing Alcohol Solutoin on the Mouth Alcohol Effect and Slope Detection of the Intoxilyzer 5000, JAT, 25(2): 112-114, 2001; and Buczek, Y. and Wigmore JG The Significance of Breath Sampling Frequency on the Mouth Alcohol Effect, Can. Soc. Forensic Sci. J. 35(4): 185-193, 2002). Hence the other safeguards.

    Your case is interesting and I would highly recommend that you publish it as a Case Report (with additional detail) in a Forensic Journal. It would be very informative to other forensic scientists practicing in this field. I would suggest perhaps you publish in the Canadian Society of Forensic Science Journal, where I have published several studies on mouth alcohol. Remember the old adage: “Science does not exist unless it is published.”