Crown Gum not connected

I have been to the dentist for the past 3 weeks have my 2 front crowns replaced. My old crowns were 12 years old, and I am sure when they were fitted, they went flush to the gums, as if they were natural teeth growing out of the gums.

The new crowns I have just had fitted are ok, but I have a problem with the fact that they don't fit flush with the gims. I thought that cosmetic dentistry mean't they should look by the the natural teeth.

I am annoyed beccause I had the teeth changed as there was a gap at the top, albeit the gap was a dark grey and very evident, the gap now is not grey and now huge, but the crown is still not completely up to the gum. I went back, and the dentist said it can not go right up to the gum as it will irritate it and wear it down over the years.

Is he correct? is it true that the crown should not go right up to the gum, and it shouldn't look like it is growing naturally out of the gum?

Any help would be great.
Thanks
Tony