A crown made and fitted in a single visit follows the same sequence as a laboratory crown. The steps are compressed rather than skipped, and each has its own constraints.
Design starts from a scan of the preparation
After the tooth is prepared, the preparation, the opposing teeth and the bite relationship are scanned, giving the software the three surfaces it needs.
The margin where the restoration will meet the tooth is identified on screen, and this line determines the fit more than any later step.
Software then proposes a crown shape, drawing on the adjacent teeth and stored anatomical forms, which the operator adjusts before manufacture.
Milling removes material rather than adding it
A blank of ceramic is held in the mill and cut by rotating burs following the design, in a subtractive process.
Bur diameter sets the finest detail achievable, since no cutting tool can produce an internal feature smaller than itself.
This is why very fine fissure anatomy is often refined by hand afterward and why the design allows for the tool's geometry.
The material dictates what happens next
Some ceramics are milled in a partially sintered state, then fired to reach full strength and their final shade, shrinking predictably during that step.
Others are milled at full strength and need only polishing or a brief glaze firing, which shortens the appointment.
Material choice therefore affects both the time involved and the strength available, and it is selected against the position and function of the tooth.
What is gained and what is traded
Avoiding a temporary crown removes the risk of it debonding, the sensitivity that follows, and a second appointment with more anaesthetic.
Against that, complex layering for high aesthetic demands is still done by a technician working by hand, since a milled block is uniform in structure.
Front teeth with demanding shade requirements are where a laboratory retains a clear advantage, and many practices use both routes accordingly.
The clinical steps have not changed
Preparation still has to provide adequate thickness, a defined margin and a path of insertion, and no scanner corrects a preparation that lacks them.
Moisture control at the margin remains critical, because a margin obscured during scanning produces a poorly fitting crown regardless of manufacturing precision.
Whether a crown is the right treatment at all is a separate question, decided from the amount of remaining tooth structure and the state of the pulp.