Since crown preparation needs to preserve the anatomy of the crown while creating space for the bulk of the material, our prep should also have this curve as well. To simplify things, this curve can be divided into two parts: Gingival 2/3 and Incisal 1/3. While thinking that this curve has two parts, these are actually coherent to each other with a smooth transition in between.
Most often when we think about the labial surface as having 2 planes, we tend to overdo it and make two obvious distinct planes forming an angle. This is a very common mistake. The labial surface should not look like a bird’s beak when viewed mesiodistally!
Actually, the difference of angle of both surfaces are not that great actually, but when you place a perio probe to compare, you will definitely see that there is a change of angle of the planes.
ERRORS
- Over-exaggeration of the placement of angles.
- Doing both of the surface at the same time will either create an even straight surface or sometimes over-exaggeration of the
PREVENTION
We must give our 2nd plane (incisal plane) last and do not reduce the planes together. When doing the gingival plane, we must disregard the angle at the cervical constriction because it will only confuse us on what angle our bur should be at.
We recommend you to follow our approach in creating the two plane reduction. This section lists some instructions to reduce the surface one at a time, starting with the gingival 2/3 first. And then doing the incisal 1/3 thereafter.
Insert Michael’s video