Veneer, Inlay, Onlay, Crown…What the heck is it?

This new technology terminology is confusing to patients, insurance companies and even dentists. Therefore, we have come up with a term, Bonded Porcelain Restoration, or BPR. Whether ½ your tooth is covered, ¼, ¾, or all of it, we call it a BPR. And the beauty of this technology is that we remove only the defective part of your tooth (old filling, decay, etc.). If half of your tooth is healthy, we don’t touch that part. We leave it intact.

Dr. Al Gerretsen wrote the following article, Bonding Terminology, for dental professionals and the dental industry in order to set a standard terminology and to aid in clarifying discussions between dentists, insurance companies and regulatory bodies.

Bonding Terminology

By Dr. Al Gerretsen

With the increase in the use of direct and indirect ceramic bonded restorations, clarification of restoration definitions is required. Some new technology is given to clarify the size of ceramic restorations.

A review of the present definitions is required. The terms filling, inlay, onlay, core, post, full crown, ¾ crown, 7/8 crown, and the new compact crown and endo crown will be clearly defined as they pertain to the differing materials available to dentists. This will serve as a guideline in discussions with fellow practitioners as well as insurance companies and regulatory bodies.

The material chosen for restoration of the tooth always determines preparation design. In the past the terms inlay, onlay and crown were related to gold. Now with the more tooth conservative preparations allowed by bonding technology we no longer can rely on these definitions to accurately describe ceramic restorations.

The diagram below identifies the critical anatomical landmarks on a tooth. (cusp tip, height of contour, marginal ridge, mesial, occlusal, distal, lingual, vestibular)

To determine the preparation form for most restorations three general rules of thumb are utilized.

The 2/3 Rule:

If the preparation width exceeds 2/3 of the distance from the fissure to the cusp tip then cusp protection is required and an indirect restoration is recommended. At this point the cusps are sufficiently weakened from loss of dentin support of the enamel that cusp fracture is imminent.

The Incisal Rule:

If the incisal edge of an anterior tooth is worn or fractured so that the remaining tooth is only 80% or less of it’s original length, a veneer or crown may be indicated.

The Height of Contour Rule:

A restoration that extends past the height of contour of a cusp is classified as a crown. If the restoration does not reach the height of contour it is an onlay.

Direct Restorations:

Direct restorations are placed incrementally into a tooth without the use of any type of impression.

Fillings:

Materials available: amalgam, composite, assorted temporary materials. A filling is a direct restoration incrementally placed into a prepared cavity in a tooth to restore lost tooth structure. Fillings can extend into all five tooth surfaces and can cover lost cusps and extend subgingivally.

Indirect Restorations:

Indirect restorations involve the use of an impression to allow for restoration fabrication outside of the patient’s mouth and is then placed into the tooth as one complete unit.

Inlay:

Materials available: gold, ceramics, and some processed composites. An inlay is fabricated outside the mouth after an impression has been taken. The restoration is then cemented or bonded into the tooth. The width of the restoration does not exceed the 2/3 rule so no cusps are covered. An inlay can extend to all surfaces of the tooth.

Onlay:

Materials available: gold, ceramics, and some processed composites. An onlay is fabricated outside the mouth after an impression has been taken. It is then cemented or bonded into the tooth. The width of the restoration exceeds the 2/3 rule (at one or more cusps) so cusps require support. In the case of gold, the cusp must be covered. In the case of a bonded restoration the cusp regains its strength from the bonding process and therefore the cusp does not always need to be covered if the margin can be placed in a non-occluding region. A ceramic or processed composite is classified as an onlay when one or more cusp tips have been reached during preparation. An onlay can extend to all surfaces of the tooth, but not beyond the height of contour on the buccal or lingual surfaces of a repaired cusp.

Compact Crown

With the use of bonding technology and ceramic materials, cores are not usually required. If the height of contour of any cusp has been exceeded, a crown is required. This is significantly different from conventional crowns and therefore more appropriately named a compact crown. The margins may or may not be supragingival.

Full Crown

Covers the majority of the tooth past the height of contour on all the cusps usually with no internal preparation anatomy but more like a thimble in shape.

Endo Crown

An endo crown is a full or compact crown that extends a post into the pulp chamber and/or pulp canal(s) as one unit (not a separate post).

Veneer

Materials available: gold, ceramic. Refers to the indirect restoration of the majority of the labial (or buccal) or lingual surface of a tooth. It may extend over the incisal edge or cusp tip or just to it. Veneers or crowns can also be done strictly for cosmetic or esthetic reasons.

Core/Buildup

Materials available: amalgam, composite, and ceramics. A core or buildup is a filling that replaces damaged tooth structure prior to preparation and replacement of a crown. It is not required to place a core to repair minor deficiencies in structure.

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