More conservative than a crown, inlays and onlays are two methods of restoring normal
tooth structure after decay or other damage. Inlays and onlays are known as indirect
fillings because unlike a standard filling that is done in a dentist's office, both are made
in a laboratory and cemented or bonded to the surface of the tooth during a second visit
to the dentist. And unlike standard fillings, inlays and onlays do not weaken the tooth
structure, but actually strengthens it. After the procedure the tooth can bear up to
50 - 75% more chewing force.

An inlay is done when the tooth structure replaced is within the cusp tips of the tooth.
If the damage is more extensive and the new structure covers the entire chewing
surface including one or more tooth cusps, the procedure is called an onlay. At the
initial consultation the dentist will determine whether the tooth can be repaired using
an inlay or onlay procedure or whether a more extensive treatment, such as a crown,
is needed. Once it is determined that an inlay or onlay will suffice, a decision needs
to be made as to the material. Gold has the longest track record, but it does tend to be
less aesthetically appealing. Porcelain and tooth colored composite resin are two other
choices of material for the new tooth structure. Because both of these materials are
tooth colored they are particularly favored if the tooth is visible or if aesthetic results are
an important goal. However, porcelain or composite resin may be more expensive than
gold and these materials have been used for less time for this purpose, so their track
record for longevity is less known.

Inlays and onlays are performed using very similar procedures. Both require two trips
to the dentist. At the first appointment, the dentist begins the procedure by numbing the
area using a local anesthetic. The decay or damage is removed using a drill, preparing
the tooth for its new surface. After all the damage is removed, an impression is made
of the prepared tooth so the inlay or onlay material can be cast in a form that will fit the
tooth exactly. A temporary restoration is placed on the tooth to protect it until the
laboratory makes the new structure and it can be bonded to the tooth. This can take
about two to three weeks.

Using the impression, a laboratory prepares the new tooth surface using gold, porcelain or composite resin. Upon return to the dentist's office, the temporary restoration is removed and the surface is cleaned to prepare for the new structure. The dentist will then try in the new restoration to ensure that there is a correct fit that doesn't interfere with your bite. If the fit is good, using special cement or bonding, the inlay or onlay is permanently attached to the tooth. Some minor adjustment may need to be made to the restoration if there are interferences. To finish the procedure, the dentist will polish the cemented or bonded structure and tooth.