Readers Questions

By 26 March, 2019Members

So you might remember I asked my subscribers recently what things they were concerned about when it came to dentistry.  In response, I got sent the following question.  I’ll answer it as best I can, but do remember I am not a lawyer so my interpretation of the matters raised might differ from that given by our more legally minded friends.

I’m also going to post this to The Dentist Facebook page because I think we need a debate about this as opinions are clearly divided.


I was reading this month’s Dental Update and Tara Renton’s article “Inferior Dental Blocks Versus Infiltration Dentistry: Is it time for change?”  It is a very long article that tries to cover the very large topic of local anaesthetics in dentistry.  It left me with several questions.  The most mind boggling I shall try to explain below:  In her summery she says “A radical change in LA practice is required with regard to many aspects of patient safety based upon current evidence”.  She also seems to feel further research is needed – but concedes that funding is unlikely.

The article also says that dentists should warn patients undergoing Dental LA of possible nerve injury and material risks.  I wondered what the “current evidence” is?

Her article says:

  • the reported adverse reaction rate to dental LA is 1:1,000,000
  • and the death rate from dental LA is 0.000002% (I translated this to be 1:50,000,000)

When I happened to be discussing this with an Engineer – they pointed out that the Fatal Accident Rate for large commercial passenger flights in 2018 was 9:25,000,000.  He also added that he was more likely to drop dead of a heart attack walking along the street and that going to see a dentist was bad enough without being warned about what he feels is a statistically meaningless risk. 

I understand that since “Montgomery vs Lanarkshire Healthboard” – clinicians are to discuss risks in terms of Material Risk to that patient – however:

  • the risk of the risk of shoulder dystocia (in the Montgomery vs Lanarkshire case) is 9-10% (1:10) not 1:1,000,000.
  • Even if you apply the formula: VALUE = probability x Perceived Consequences => there is a massive difference simply because 1:10 is much more probable than 1:1,000,000

As a grass roots dentist I feel the important thing about dentistry is not to hurt people and to treat them in a kind and thoughtful and considerate manner.   If Dental LA is safer than Air Travel (which is the safest form of transport allegedly) then I do not understand why one would need to formally consent patients for having a dental LA?  I just wondered what you thought as you have a better understanding of the medico-legal side of things.  I do wonder what patients and the general public think of this as well actually.


Okay, let’s get down to the meat of this.  I have seen Tara Renton speak before, and I know she is not in favour of giving ID blocks, especially when using Articaine.  I haven’t read the article because it is behind a pay wall.  She has her reasons for saying this, and it is understandable that patients can be distressed from receiving an injury to their ID nerve from what to us is the simplest of procedures.

From the research I could find, ID nerve injury from an ID block ranges between 1:25,000 to 1:800,000, so it is a relatively low-risk procedure.  What we need to determine is whether we need to warn the patient about this under Montgomery and under the GDC standards.

I would say that for most people we probably don’t but there is a chance I might be mistaken.  So why do I say this?  Well, under Montgomery there are three types of risk:

  • General risks (Anaesthetic will leave you numb for example)
  • Treatment-specific risks (tuberosity # upon taking out an upper 8 for example)
  • Patient-specific risks

And ID nerve damage following an ID block is so rare, it really likely only comes under patient-specific risks.  For treatment specific, and general risks, the courts have made some movement on clarifying what a material risk is.

A v East Kent Hospitals University NHS Foundation Trust (2015) – Claim dismissed, the Judge finding that the material risk claimed by the claimant was NOT a risk that a reasonable patient in the claimants position would have attached significance – Dingemans J said that a risk of 1:1,000 could be described as “theoretical, negligible or background”


Tasmin v Barts Health NHS Trust (2015) – found for the defendant. Dismissing the claim, the judge said the risk of serious injury was negligible, of the order of 1:1,000. He held that this was not a material risk, citing A v East Kent Hospitals NHS Foundation Trust [2015] EWHC where Dingemans J described a risk of 1:1,000 as ‘theoretical, negligible or background’. However, he preferred to formulate the risk as being ‘too low to be material’. The claim therefore failed.


The Montgomery duty requires patients to be given choice. It is not enough to advise of the risks and benefits of a recommended treatment. Patients must be told of the risks of ‘the recommended treatment, and of any reasonable alternative or variant treatments’ – so for an ID block, if you felt the material risk was relevant to them, you would give the warning plus the alternative options (Supra crestal etc)

A consent form signed on the day of surgery, or at any time, doesn’t indicate valid consent.  Consent forms are only part of a process of advising and providing consent

Whether a risk is material or advice is adequate is not a matter to be judged by the standards of the medical profession. It is for the court.  – and that right there is the problem.

Montgomery requires a doctor to take reasonable care ‘to ensure that the patient is aware of any material risks involved in any recommended treatment, and of any reasonable alternative or variant treatments. The test of materiality is whether, in the circumstances of the particular case, a reasonable person in the patient’s position would be likely to attach significance to the risk, or the doctor is or should reasonably be aware that the particular patient would be likely to attach significance to it – so Mr’s Miggins down the pie shop probably doesn’t need to know about the risk from an ID block.  But someone who is an internationally renowned saxophone player, whose livelihood might be affected by a permanently numb lip…..?

There is still the notion, post-Montgomery that not all risks are material. So we aren’t at the point of having to warn of death for every LA injection.  But, as I have already said, only the court can ultimately decide whether a patient should have been warned.

The problem is, if we are now having to warn about such insignificant risks, where does it end?  Do we have to warn them about the risk of being involved in an RTA on the way to the surgery?  What about the risk that the electricity might go out mid-treatment (which in my career has happened several times)?

This is not what Montgomery was intended to create and I’m hoping we can get some clarity because it’s clearly something people are worried about.

What do you think?