Which is correct Dr. or Dr? appointment and Contact

The Oxford Learners’ Dictionary says:

Mr abbreviation
(British English)
(also Mr. North American English, British English)

While the Oxford Learner’s Dictionary of American English just states:

Mr. abbreviation

and has no entry for Mr without the period.

So I believe that both Mr and Mr. are acceptable in British English (even though Mr without period is preferred), while Mr. with period is mandatory in American English.

As an Italian, I prefer Mr without the period, because in school we were taught that the period following an abbreviation stood for “following letters omitted”, but the r in Mr and in Dr is the last letter of Mister and Doctor, so no letter following “r” is omitted.
I think that the British usage tends to conform to this “European” (Latin?) rule.