conservative by design
Dental inlay and onlay restorations are used when old fillings need to be removed or replaced and are sometimes referred to as ‘partial crowns’. They are also used used to repair teeth with mild to moderate decay or are cracked and fractured. Ideal candidates for inlay or onlay work typically have too much damage or decay in the tooth structure, to be predictably treated using a composite or an amalgam, but have sufficient healthy tooth remaining to avoid the need for a crown. This allows the dentist to conserve more of the patient’s original tooth structure.
A dental inlay looks very much like a conventional filling in a tooth where the extent of the damage in a tooth is confined within the cusp of the teeth, as seen in the diagram above. An inlay is fabricated in the laboratory and then cemented to the prepared tooth. The advantages an indirect method to restore a tooth, versus a filling made directly in the mouth, is that the inlay is created in a controlled environment absent of saliva and contaminants that can interfere with the bonding.
An onlay is indicated when the damage to the tooth extends beyond the confines of the cusp. The onlay design will encompasses the missing cusp and will extend to any cusp where the structural integrity is compromised. Similar to inlays, the old fillings are removed, the preparation of the tooth is modified and refined to maximize retention of the restoration. An impression of the tooth is made and sent to the laboratory to fabricate and once completed it is cemented in a similar fashion to the inlay. Both inlays and onlays can be fabricated from several different materials. Each material has its own advantages and disadvantages and is summarized below.
Porcelain is the most advantageous material for satisfying a high esthetic demand. Typically made of lithium disilicate, also referred to as eMax porcelain, it is the union of strength and style. It lacks the impact strength and malleability of gold but is still a very strong material. On an accurate model of the tooth, the margins of an eMax restoration can have a great adaptability to the tooth structure and our ability to bond it to tooth provides a great seal.
Gold is still considered the best material in dentistry, but what it possesses in physical characteristics it lacks in esthetic appeal. As esthetics has an ever increasing demand in dentistry gold has become less and less desired. As a restorative material, gold has the closest properties to natural enamel and dentin than any other material. Its main advantages are strength, long term longevity and durability.
Composite resin is the only material that is used as a direct and indirect material and is one of two materials that are used in conventional fillings, the other being amalgam. As with porcelain and gold, an indirect method of fabricating composite resin inlays and onlays have the advantage of being under a controlled environment. Composite resin is sensitive to moisture, so the manipulation of the material in a dry environment has a tremendous advantage. Of the options available, composite resins have the least strength and hardness, but is the most easily manipulated and most easily repaired if fractured or damaged during function.