That seems a bit odd. Mind you, it all depends exactly WHY they tried the experiment. It could well have been to try and eliminate the 'ghosting' effect on the reverse, which it failed to do. What it DID do however, is to ensure that Britannia was fully struck up, avoiding the flattening to face and upper body which the non-RE obverse was causing. So you could say it was a partial success.
I wouldn't have thought that a single broken tooth would have caused them to abandon the experiment, but then again, in 1916 the nation had a lot more to think and worry about than how well struck up pennies were.