Inlays, Onlays, and Crowns: Understanding the Similarities and Differences

Admin • June 25, 2020

Woman With Mouth Open — Sarasota, FL — Gregory S. Rutherford, DDS, PA

Despite their hard enamel coatings, teeth can sustain damage due to accidents, decay, or age-related wear and tear. Fortunately, modern dental techniques offer patients several options for restoring portions of their teeth. Three such options include inlays, onlays, and crowns.

Differences in Form

Crowns, inlays, and onlays differ in the amount of tooth surface that they replace. A dental crown gets its name from the fact that it covers the entire crown of the tooth, from the fissures and chewing surfaces on top to just below the gum line. This complete coverage also causes people to refer to crowns as caps.

Inlays solely address cracks or decay in the fissures between the cusps of a tooth, much like fillings. Unlike fillings, however, dentists fabricate inlays outside the mouth instead of simply shaping the restorative material inside a drilled hole in the tooth.

An onlay covers both the fissures of the tooth and one of the cusps.

Differences in Function

Inlays, onlays, and crowns all restore a tooth's structure and function to some degree. The choice of restoration that your dentist recommends will depend mainly on the extent of the damage, the strength of the remaining tooth, and amount of tooth material that needs reinforcement.

Dentists often turn to inlays as the next step beyond fillings for the repair of large, deep cavities that standard fillings cannot correct satisfactorily. A form-fitted porcelain or composite inlay actually lends greater chewing strength of the repaired tooth while offering more durability than a filling.

An onlay can protect and strengthen a tooth in which at least one cusp has become cracked, chipped, or broken along the chewing surface. It serves as an intermediate measure to keep such damage from progressing to the point that it needs a crown.

Dental crowns provide the strongest functional reinforcement for broken, chipped, or cracked teeth. Unlike inlays or onlays, they can restore cracks or other damage that extend to the sides of the teeth (but not for cracks that extend into the roots).

Dental crowns also play roles in more extensive kinds of tooth restoration. For instance, an implant will include a permanent crown to provide a realistic smile and natural chewing function. Crowns also fill out the missing teeth in bridges.

Differences in Appliance

Inlays, onlays, and crowns all share certain similarities regarding preparation and installation. In all three cases, the dentist must make the tooth ready to receive its restoration. This process may involve cleaning out decay and shaping the tooth enamel.

If you need an inlay, you may find the enamel shaping process similar to that of having a tooth drilled for a filling. Onlays may require more extensive enamel removal from the surface receiving the restoration. Crowned teeth usually need reshaping of all enamel surfaces.

The dentist will take impressions of the tooth during this preparatory appointment. These impressions will go to a dental laboratory, which will create a restoration that fits the tooth perfectly. Whatever type restoration you get, you may need to wear a temporary restoration until the permanent version arrives.

Differences in Lifespan and Cost

The life expectancy of any tooth restoration hinges on many factors, from the type of procedure and the materials used to the care that the restored tooth receives from its owner.

Dental crowns, which typically take a lot of punishment from biting and chewing forces, typically last from five to 15 years before they start to wear out. Dental inlays or onlays may last much longer than crowns, although they may also need replacement eventually.

Crowns cost more than inlays or onlays due to the more extensive amount of work and material that goes into them. However, onlays made of gold or other expensive materials can sometimes rival crowns in this area.

Gregory S. Rutherford, DDS, PA, can help you choose the ideal tooth restoration for your needs. Contact our clinic today.

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