All Resin — these are the most affordable variety available but are not acknowledged for their strength. They can fracture easily and tend to wear down over a period. Staining is a problem associated with this variety.
All-Ceramic [all porcelain] — this variety can be very expensive but if aesthetics is a major consideration in your decision this can be a great option. They can offer the best color matches with your other ones because porcelain is translucent and reflects the natural color of what’s beneath. Porcelain is, however, a poor conductor of heat and therefore the initial period of sensitivity to heat and cold is negligible for some time. You will not be affected by allergies as it is common with some other materials. However, they tend to wear out faster than most other materials. They are also susceptible to cracking under the forces of chewing especially with patients suffering from bruxism. Considering these reasons, porcelain caps needed for any molars are made thicker necessitating the need to trim more enamel from the teeth. These are generally used on front ones where aesthetics are more important.
Zirconia Or Milled — If you are concerned about aesthetics but finances are not a consideration you are recommended to go with zirconium. They are the most expensive variety but being translucent they can provide a very good color match with your others. They are not susceptible to cracks as the ceramic ones are because they are metallic. Zirconia is presently highly popular among many people. CAD/CAM facilities allow the zirconia crowns to be milled even as the patient rates. This can also be saved for a second visit.
Made from Porcelain Fused To Metal — Fusing porcelain over metal [which may even be zirconia] has helped to overcome the disadvantage of the brittleness of all-porcelain crowns while still offering good color matches to the adjacent ones. They are the best aesthetic choice after all porcelain. However, the metal underlay can become visible along the gum line if the gum recedes. Furthermore, the underlying metal [normally a gold alloy] can make the cap appear unnatural. The zirconia base can be milled and will be more affordable than a gold base.