This article discusses dental clinical negligence in England and Wales. Legal tests and procedural rules may differ elsewhere.
A poor outcome after dental treatment does not, by itself, show that a dentist caused it. Even where care fell below the required standard, there is a separate question: what difference did that failing actually make? A useful causation opinion compares what happened with what would probably have happened if appropriate care had been provided.
The alleged failing
The first step is to identify the alleged breach of duty precisely. “The treatment was negligent” is too broad to test. Was the concern a missed finding on a radiograph, a delay in referral, an unsuitable treatment plan, or a failure to explain an option? The answer determines which alternative course of care needs to be considered.
For an alleged clinical failing, the opinion should set out the likely sequence with appropriate care: when the problem would have been recognised, what further assessment would probably have followed, and which treatment options would realistically have been available. That sequence must be grounded in the evidence at the relevant time. Appropriate care cannot be assumed to guarantee a favourable result.
Actual and likely outcomes
Suppose periodontal disease was identified later than it should have been. Earlier diagnosis and management may have affected the extent of progression, the treatment required or the timing of tooth loss. The starting condition matters: some deterioration may have occurred despite appropriate care, while the delay may have added to it. The expert should assess whether the delay contributed to actual deterioration, and to what extent. That is different from saying only that it increased the risk of deterioration. Whether any contribution is material in the legal sense is for the court. Where several causes combined, their precise shares may not be clinically separable; the opinion should explain what the evidence does establish.
Similarly, where a tooth was extracted after a disputed course of treatment, an expert should consider whether the tooth was likely to have been retained with appropriate care, for how long, and with what further treatment. It may be possible to support a conclusion about additional treatment or an earlier extraction without saying that the tooth would have lasted indefinitely.
Consent and patient choice
Where the alleged failing concerns consent, the comparison is different. The question includes what the patient would probably have decided if properly informed, and what would have followed from that decision. The dental expert can explain the reasonable treatment alternatives and their likely clinical consequences. Evidence about the patient's own priorities and likely choice also matters; those findings are ultimately for the court.
Evidence and uncertainty
Contemporaneous notes, radiographs, periodontal charting, referrals and subsequent treatment records may help establish the condition at each stage. Gaps in those records can materially limit the opinion. A report should say which facts are documented, which are assumed, and whether a different account of the facts would change the conclusion.
Percentages need particular care. An estimate that a tooth had, say, a 40% chance of avoiding extraction with appropriate care means that, on balance, it would have been lost in any event. That does not establish that the failing caused its loss. Even then, a case may involve identifiable additional treatment or an earlier loss that can be assessed separately. A percentage chance cannot simply be converted into the same percentage of damages. The approach to a lost chance of a better medical outcome is a legal matter; Gregg v Scott [2005] UKHL 2 illustrates the distinction in an England and Wales clinical negligence claim.
Questions for the letter of instruction
A focused letter of instruction can ask what would probably have happened with appropriate care; what injury or additional treatment, if any, was probably avoidable; whether the timing of the outcome would have changed; and which conclusions depend on disputed facts or missing records. If consent is in issue, it should also identify the information allegedly omitted and the alternative choice said to have been available. The relevant records and a clear chronology are especially important when the alleged harm developed over time. For instructions across the UK, Republic of Ireland or internationally, see how to instruct.
For England and Wales, the usual starting point for factual causation is the “but for” comparison, assessed on the balance of probabilities. Particular cases can raise more complex issues. The dental expert's role is to give a reasoned clinical opinion within their expertise; the court decides the legal question on the evidence as a whole.