Bolam v. Friern
The standard of treatment required and what is accepted practice is clearly stated in:
Bolam v. Friern HMC  1 WLR 582, 587-8.
The test is the standard of the ordinary skilled man exercising and professing to have that skill. A man need not possess the highest expert skill at the risk of being found negligent. It is well-established law that it is sufficient if he exercises the ordinary skill of an ordinary man exercising that particular art
A dentist is not guilty of negligence if he acted:
...in accordance with a practice accepted as proper by a responsible body of medical men skilled in that particular area....a man is not negligent, if he is acting in accordance with such a practice merely because there is a body of opinion who would take a contrary view
Bolitho v City and Hackney Health Authority
November 27 1997 HOUSE OF LORDS
A court was not bound to hold that a defendant doctor escaped liability for negligent treatment or diagnosis just because he led evidence from a number of medical experts who were genuinely of the opinion that his treatment or diagnosis accorded with sound medical practice.
The court had to be satisfied that the exponents of the body of opinion relied on could demonstrate that such opinion had a logical basis.
In particular in cases involving, as they often did, the weighing of risks against benefits, the judge, before accepting a body of opinion as being responsible, reasonable or respectable, would need to be satisfied that, in forming their views, the experts had directed their minds to the question of comparative risks and benefits and had reached a defensible conclusion on the matter