Perhaps you have heard of the new trend in people having porcelain inlays installed in their teeth instead of convention fillings made from a metal amalgam comprized of mercury and silver or gold. For some people, its a decision made because they are uncomfortable with the mercury that is in the filling amalgam, while for others the reason is purely cosmetic.
This is because porcelain inlays are the same color as the tooth itself, so they tend to blend right in with the rest of the tooth. Is there other reasons why a person might or may not choose porcelain inlays for their next filling? One of the down sides of porcelain inlays is that they take two dentist visits to have installed, unlike a standard metal filling that takes only one visit.
This is because the porcelain inlay has to be made in a dental lab from a mold that is taken during the first visit. One more positive side of porcelain inlays however, is that unlike metal fillings they are far less tolerable to expansion and contracting caused by eating or drinking very cold or very hot foods and drinks.
This means that they will last longer and can never cause the tooth to crack. Also porcelain inlays tend to be far more secure over the long run, because they are actually glued into the tooth with a high tech dental adhesive.
Standard metal filings are not glued in but they are packed into a crevice that is shaped in such a way that the filling is "locked" into place when it is completed. Also, because porcelain inlays take two visits to have completely installed and have to be special made in a dental lab they are course are more expensive then a standard metal filling.