What is a Dental Onlay?

What is an onlay?  Let’s keep it simple.  Basically, an onlay is an indirect restoration — meaning it is fabricated outside of the mouth — that covers one or more cusps of the tooth.  It is different than a dental crown in that a crown is a tooth shaped “cap” that is placed over the entire tooth. While the two are different, the aim of both restorations is similar. In both situations, the goal is to restore the tooth’s shape, size, strength, and appearance.  An onlay is a less-invasive way to achieve the same goal because less natural tooth structure is removed.

So how does a dentist choose between an onlay and a crown when diagnosing restorative dental work?  There are several different factors to consider; let’s take a look at a few of the key considerations:

How much healthy tooth structure remains?  If a tooth has been moderately compromised by dental caries, or significantly cut down for previous restorations, often times these teeth have nearly virgin outer surfaces of the tooth that can be preserved.  Retaining more natural tooth structure is the key.

Does a tooth have cracks?  If a tooth does have a crack, how big is the crack and where is it? Generally, if a cusp has a horizontal crack and the remaining tooth structure is intact, then an onlay is the conservative restoration.  If a tooth has a vertical crack or multiple cracks, then a crown may be indicated.

Does the patient have a history of grinding or clenching?  If a patient has a history of bruxism or clenching, the clinician will evaluate the strength of the cusps and decide whether an onlay or a crown is indicated.

Unfortunately, many dentists only offer full crowns for their patients.  Why?  Well, some argue that making a tooth preparation for crowns is easier than preparing a tooth for a dental onlay, and that is why a crown may be the more common treatment.  Additionally, when it comes to third party payment (i.e. insurance reimbursement), insurance companies typically do not reimburse reliably for onlays while crowns more often than not qualify for insurance benefits.

We believe it comes down to ethics.  A patient should have all treatment options available and presented to them. This enables the patient to make an informed, final decision when it comes to his or her own dental health.  We also strongly believe in providing minimally invasive dentistry.  In most cases, less existing tooth structure is removed with onlays as compared to full crowns.  Wouldn’t it make better sense for insurance companies to reimburse more conservative restorations like onlays, rather than full crowns?

At Cascades Center for Dental Health, we have the option of having a dental laboratory fabricate your dental onlay, or we can make it ourselves right in the office with CEREC.  Having the onlay fabricated in a laboratory would entail two visits — one to evaluate and design the onlay, and another to deliver it.  With CEREC, the onlay can be designed, fabricated and placed in a single visit.  CEREC is a computer-aided design / computer-aided manufacturing (CAD/CAM) device that enables us to take a picture of your tooth, design the onlay on the computer to fit in your tooth, fabricate it, and deliver the tooth-colored restoration during only one dental visit.

More about Onlays:

• Dental onlays have proven themselves to serve just as well as other restorations for a significant number of years.
• With onlays, there is less trauma to the nerve inside the tooth, which results in a lower chance of a root canal being needed.
• The likelihood of a new cavity forming at the edge of the restoration (called the margin) is not as high with onlays as it is with crowns. This is because the margin of an onlay is in a higher, more cleansable area, while the margin of a crown is at the gum line.
• If another restoration is ever needed, there is more tooth structure remaining to work with under an onlay as opposed to under a crown.
• Finally, dental onlays that are tooth-colored are beautiful and disappear inside the tooth, whereas some full crowns remain visible.

Here at Cascades Dental, we do what is best for you and your overall health.  Minimally invasive dentistry by preserving tooth structure is our goal, and we strive to offer our patients all available treatments for the most informed decision.  We work only with the best labs in the area, and we have been trained extensively on how to prepare and deliver dental onlays using CEREC technology, to deliver a quality restoration efficiently.

If you have any questions about anything covered in this blog, please feel free to call us or bring your questions to your next dental visit.  We look forward to serving you!