The method for choosing crown appearance, as well as its fabrication and testing is identical regardless of whether it is placed over a natural tooth or over an implant; the only difference is in the process used to prepare a patient. On this page we will discuss the process of placing crowns on natural teeth, both for single crowns covering one tooth and a string of crowns comprising a bridge. You can read about the way crowns are placed on implants in the section dealing withimplants.
PREPARATION FOR CROWN FABRICATION
During the first visit, impressions are taken in order to register the position, shape and appearance of teeth. Aside from taking the impressions, we can also do a CAM-CAD 3D scan, which is a good way to go if we decided on full zirconium crowns or full ceramic crowns using the CEREC machine, since the machine can import 3D scan data for maximum accuracy. Another case where computer scanning is desirable is when we have to do a full arch work in both jaws, because software facilitates the planning of the final work, although this technique is again combined with the standard taking of impressions.
What comes next is choosing the shape, size, length and colour of future teeth. After this, the recontouring is done, after which impressions are taken and temporary dental crowns are made, which is given to every patient. Recontouring lasts as little as an hour for a smaller number of teeth, to up to 6 hours for recontouring all teeth in both jaws. Recontouring itself is performed using stat-of-the-art local anesthetics with prolonged effect, making the process of recontouring completely painless. The maximum depth of recontouring is between 0.5mm to 2mm.
HOW DEEP DO WE GO IN TEETH RECONTOURING?
Many patients will know from their personal experience what it is like to have a bulk of a tooth stripped off in order to place a crown, with only a small portion of the original tooth left peaking out of gums. This practice has long been abandoned, because new technologies enable us be minimally invasive with maximum esthetic and functional results, while almost completely preserving the tooth substance.
The application of non-metal crowns yields perfect results with minimal contouring involved. Metal-ceramic crowns require a more substantial teeth contouring since it is necessary for the ceramic that is placed over the metal core to have certain thickness in order to mask that core, so it becomes impossible to have a very thin crown. If a tooth is healthy and a crown is placed for purely esthetic reasons, the contouring may then be done to the depth of only 0.5mm.
In practice, the contouring of both jaws, taking impressions and fabrication of all temporary dental crowns in a single visit has proven to be the best solution as far as the patient is concerned, although this one session may last up to several hours. There is an option to prepare one jaw at a time, but this is far more strenuous for the patient because they would have to undergo the same procedure twice.
Comparing the dental crown colour with the desired colour
TRYING OUT DENTAL CROWNS
The tryout of teeth is the most important phase of crown fabrication where a patient is presented with their new teeth. Dental ceramic crowns are not polished yet at this point, but they possess the shape and the basic colour, so there is still room to make corrections in shape and colour. At this stage, the colour of crowns may be adjusted towards yellow only, not towards white, which is why it is crucial that the patient choose the colour wisely during the initial discussion with the dentist, where listening to our advice is always a good idea.
From time to time, there is a possible interim stage, which is the trial of metal substance for metal-ceramic crowns or zirconium core for non-metal ceramic crowns. This stage is normally omitted if the impressions taken are well-made; it is necessary only in rare cases when we are not 100% sure that the impression will reflect a patient’s needs in a proper way.
If the crowns are placed in full arch on one or both jaws, each patient gets a silicon cover to wear during night to prevent any damage to crowns. There is a mandatory checkup one day after the cementing to check the bite and to make final adjustments to the occlusion of the new crowns.