Dental Crowns (Lab Made)
A crown can be made for any tooth in the mouth (unlike an OVC which is only for back chewing teeth). Crowns are typically recommended for heavily filled, broken or root-filled teeth that may break or fracture. They can cover all the chewing surface of the tooth and extend to the gumline like a glove fitting over a hand, or can partially cover the walls of the tooth. Our crowns are manufactured at Evolve Dental Studios, an NZ laboratory behind our building by an experienced team of technicians.
Front or anterior teeth crowns all appear to be white on the outside, and their substructure may be porcelain emax, a porcelain fused to metal structure, or zirconia. It depends how much tooth is remaining and strength required as to which material to use; your dentist and lab technician will choose the optimal material with your guidance.
Posterior or back teeth can be made from the same materials an anterior crown, but also can be made from a gold alloy. The back teeth in your mouth (not your wisdom teeth), are smaller in height than the molar tooth in front, making less space for the crown material. Gold crowns remove the least amount of tooth structure and are the strongest, longest-lasting restoration; hence back teeth benefit from gold the most. For a more natural look, crowns can be white like front teeth. Porcelain wears away the opposing teeth as it is harder than natural teeth unlike gold. Although it is harder wearing against teeth, it is brittle if it is too thin. This means more tooth is required to be removed so the porcelain is of a thickness that makes it much less likely to break.
CROWNS – THE PROCEDURE
The tooth is numbed up, and an impression and shade of the tooth is taken. A portion of the tooth is removed from all angles of the tooth, approximately 0.7mm for gold and 2-2.5mm for porcelain. Two layers of retraction cord are placed around the gum to hold this away from the prepared crown margin. A silicone impression is taken of the prepared tooth, and an impression of the opposing arch is taken in alginate. How your teeth come together is recorded using a silicone bite material. Lastly a temporary crown is manufactured and temporarily cemented into place.
After-care is hugely important after a temporary crown is placed. It is very important to keep the gums around the prepared tooth as healthy as possible. This is with brushing and flossing. It is better to use string floss in this instance. When flossing, please floss down towards the gum and draw the floss out from the gumline. This (hopefully!) means the temporary crown will stay in place. If you pull floss up and out as normal, it may dislodge the temporary crown. If this does happen, please come into the practice for us to recement it at no cost.
If the tooth is a front tooth, we recommend our patients to see our lab technician for a shade. Ben will contact you to arrange a suitable time. This will only take 5-10 minutes.
Three weeks after the preparation, the crown is ready to be fitted. The tooth is numbed up again as before, and the temporary crown is removed. Sometimes they lift off, but sometimes the temporary crown needs sectioning to be removed. The temporary cement is removed, and the final crown is trial fitted into place. The shade, bite and margins are checked before using permanent cement to fit the crown. Sometimes the crown requires a minor adjustment after fitting. The tooth is now as good as new, and in a much stronger state.
Root-filled teeth are somewhat brittle, therefore benefit from crowns as these provide significant strength. Some crowns are placed on teeth that respond positively to cold air prior to treatment, but in 10% or less of teeth, the tooth will die and require a root canal treatment, or extraction.
RISKS OF CROWNS
Sometimes crowns can fall off and be recemented back into place, although when a crown has fallen off, there could be something underlying that is not functioning anymore. Occasionally, the only way to reattach the crown to the tooth is to electively do a root canal treatment, place a post into the canal and manufacture a new crown. Infrequently a crown snaps off the tooth and there is inadequate tooth structure to remake a new crown and the only option is removal of the tooth.