BB hint #3 Pre-prep "preparation" part B

Part B includes the path of insertion and removal or PI & R of the final crown.
Often if the tooth you are preparing for a crown has either had decay that has cavitated or collapsed mesially and distally, the net mesial/distal dimension of the tooth has actually decreased and to a small degree, the roots of the subject tooth to the adjacent teeth are closer together.
This affects the final "P,I and R" in the following ways:
1. the adjacent teeth tend to tilt toward the narrowing tooth
(photo)
2.the contacts now become more pointed for the new crown than ideal, due to the tilt of the adjacent teeth
(photo)
3. you can have a prep that "draws" with itself, but not necessarily drawing with the required P,I & R that the adjacent teeth present you with.

So what is the solution? I have to tell a story on one of my best and admired professors at USC, Dr Richard Kahn. I had come back as a part time faculty to teach in the operative department and was in one of my first days just following him around helping the students.
We were trying to help a student with a troublesome seating of a crown and as they struggled, I opened my big mouth and blurted out what would have been blasphemy while I was in school:
"why don't you just adjust the adjacent tooth"
I had looked at the BWX and noticed that the adjacent tooth, made by a dental student a few years earlier was excessively bulky and making it very difficult to seat the new crown due to concept #3 above. The crown seated on the die with no undercuts, but when placed on the "untouched model" we always had to do, it was hitting heavily on the distal where the bulky crown was. I noticed that the distal preparation was sort of deep and "tucked under" the old crown, thus not allowing the full seating simply due to the fact that the dimension of the occlusal access (photo) was narrower than the total length m/d of the prepared tooths outer dimensions. Thus a simple recontouring of the very bulky crown, while marking the contact point would allow full seating.
Dr Kahn looked up at me, smiled and gracefully said something like, "Dr Nelson, I knew I trained you well! I admired him for acknowledging to me and all the students there watching that he had gotten so narrowed down to the details of seating, he hadn't even looked at the adjacent teeth.
Another factor affecting the "assumptions" was that he knew the adjacent crown was made at the school, so his operational situation was an assumption it's contours were correct, or it wouldn't have been passed off, right?
In other words, he was acknowledging how in a school environment, it is easy to miss the "forest for the trees"
take care
fmn