## Facts

- A dental patient sued a dentist for professional negligence after a tooth slipped from the dentist’s forceps during extraction and was swallowed by the patient.
- The patient claimed the dentist’s negligent technique caused the swallowing and that the swallowed tooth produced later internal illness and physical disability.
- The patient offered lay testimony describing the event, subsequent symptoms, and claimed improvement after he later expelled the tooth, but presented no medical expert testimony linking the tooth to the alleged internal conditions.
- The dentist testified he used proper methods and exercised appropriate care and skill.
- Multiple defense medical experts testified that the dentist’s conduct met professional standards and that the patient’s claimed illness and disability were attributable to other conditions, not swallowing the tooth.

## Issues

1. Whether the evidence permitted a reasonable jury to find that the dentist failed to exercise the ordinary care and skill of dentists in similar circumstances.
2. Whether a jury could find medical causation for internal illness based on the patient’s lay testimony when uncontradicted expert testimony attributed the condition to other causes.

## Decision

- The court sustained the dentist’s exceptions and set aside the plaintiff’s jury verdict.
- The court held the evidence was legally insufficient to prove either professional negligence or that the dentist’s conduct caused the patient’s subsequent illness and disability.
- The trial judge should have directed a verdict for the defendant rather than submitting the case to the jury.

## Legal Principles

- In professional negligence actions, the plaintiff bears the burden to prove both breach of the applicable standard of care and causation of the claimed injury.
- When alleged medical causation involves matters beyond common knowledge, competent expert testimony is generally required to establish causation.
- A jury may not reject unanimous, uncontradicted expert testimony on technical medical questions and substitute speculation where the opposing party offers no competent medical evidence supporting a contrary causal inference.
- The occurrence of an adverse outcome during treatment, without more, does not itself permit an inference of professional negligence.

## Conclusion

The court reversed the plaintiff’s recovery because the record contained no competent evidence that the dentist’s technique fell below professional standards or that swallowing the tooth caused the patient’s later internal condition, and the jury could not base findings on conjecture contrary to unopposed expert medical testimony.


Toy v. Mackintosh, 110 N.E. 1034 (Mass. 1916)