I had a patient ask over the weekend why some crowns had less anatomy than others. I told her when we do occlusal reduction, we reduce 2mm off the occlusal surface of the pre-existing restoration – we follow the contours not of the original native tooth, but rather off the contours of the existing restoration. If we had wanted plunging, deep, dramatic anatomy, we would have either had to arbitrarily drill deeper (guesstimating the depth of the fissure and then taking 1.5-2mm below this as a standard for material resistance form) or actually place a direct composite with full anatomy, dialled into the occlusion before prepping 1.5mm-2.0mm deep from this level. To be minimally invasive, we often work with the contours of the existing anatomy to reduce only what is needed to achieve our functional aim, which trumps occlusal esthetic anatomy for me posteriorly when it comes to bonded porcelain restorations.
Some food for thought…pretty is not always better for the patient. Note: the 24 PFM crown is being replaced after endodontic retreatment.