What Are Dental Onlays?

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You’ve come to our office for your cleaning and examination appointment, where we’ve gathered all the information we need for Dr. Slepchik to prepare your specific dental treatment plan.  We must also consider how we get to the final result when choosing what treatment to do.  When we see teeth that has cuspal breakdown, there are 2 options: a crown or an onlay. Your cusps are the main contribution to chewing;  if they are broken down or weakened, they must be reinforced and strengthened.

We could describe a dental onlay as a type of filling for a damaged tooth. However, this type of restoration is in a class of its own because it is not placed directly in a cavity like a standard filling. Onlays are custom-made restorations that are carved out of ceramic or porcelain material to fit over one or more cusps of a tooth. The cusps are the high points that are situated at each corner of a tooth. It is important to preserve or restore cusps because they play an integral role in chewing. Onlays are made in our dental lab using impressions from the damaged tooth and are bonded to the tooth in the next visit.

What Are The Benefits Of Dental Onlays?

Dental onlay treatment is recommended for patients because it is a conservative approach to restoring teeth. An onlay outperforms a standard, direct filling because it is customized to recreate nearly 100 percent of the natural strength the tooth had before the injury or decay. At the same time, an onlay achieves excellent results without the need for extensive modification of the natural tooth. This conservative approach reduces the risk of nerve irritation in the tooth that could lead to ongoing pain. Unlike a direct metal deep filling, there is virtually no chance of extra space existing between the restoration and the tooth material.

When Are Dental Onlays Recommended?

A dental onlay may be recommended if a tooth has sustained damage that extends over one of its corners. This is referred to as cuspal replacement. Onlays can be used to replace old amalgam fillings that have cracked or lost integrity, as naturally happens over time. Sometimes, the decay is extensive and requires more coverage to protect the tooth.

What Are Onlays Made Of?

Dental onlays are made from dental porcelain. The impression is taken here in our office using our Itero which links directly to our dental laboratory. Following the preparation appointment, it takes about 2 weeks for the lab to make it. You return to our office and the onlay is permanently cemented in your mouth. Dental porcelain is also extremely durable and looks just like a natural tooth.

The Dental Onlay Procedure

If a dental exam reveals tooth damage, Dr. Slepchik evaluates the extent of it so the most suitable repair can be made. Your options are fully explained to you, as well as shown on the intra-oral camera, allowing you to make a confident decision regarding the care that will provide you with the best outcome.

To prep the tooth for its new restoration, the minor reduction will be performed using anesthetic. Reduction only removes the part of the tooth that has been damaged. An impression is then taken with Itero, our computerized impression system that links directly to our lab.  This will be used to create a model of the tooth that will serve as a guide for the new onlay. A temporary restoration is placed over the tooth and the models and specifications are sent to our dental lab.

A second visit is needed to bond your onlay to the tooth. After removing the temporary and any dental cement that has adhered to the tooth, the onlay is set into place. A few assessments are conducted to ensure the onlay is well-situated on the tooth and also that it fits naturally against the opposing tooth when you bite down. Once all aspects of the onlay are satisfactory, a bonding material is applied and hardened with a high-intensity light.

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Large worn composite restorations on last Molars.
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Best treatment chosen: Porcelain Onlays restorations. Photo of temporaries in place. Used while the porcelain is fabricated in the Laboratory.
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Porcelain onlays in place
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Another view of final work.

Before & After Dental Onlays

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onlay after

What’s The Difference Between Dental Onlays And Dental Crowns?

The primary difference between an onlay and a dental crown is that one fits onto the top and side part of a tooth and the other covers the tooth completely. Crowns used to be considered the gold standard when extensive restoration was necessary. However, now, more dentists and their patients are choosing onlays. The reason is that onlay treatment is a more conservative approach than a dental crown. To place a crown, it is necessary to remove a large portion of natural tooth structure. An onlay only requires that the damaged enamel be removed.

Fitted over only the upper aspect of the tooth, an onlay is bonded into place. The bonding process creates tight margins that cannot be penetrated by bacteria. There is no soft tissue around the onlay as there is around the gumline margins of a crown. Because gum tissue may become inflamed and recede away from the crown, there is a slight risk of infection at some point.

Both crowns and onlays look just exactly like a natural tooth. Both have a comparable life span.

How Long Do Onlays Last?

A dental onlay can last 10 to 15 years or more. The lifetime of an onlay may be affected by many factors; such as where it is in the mouth and how you take care of your mouth at home. Do you keep your cleaning appointments with your hygienist according to your specific dental regimen after treatment? All these factors play a role in how long any dental procedure will last.

What Do Dental Onlays Look Like?

Once an onlay is in place, it will look like your natural teeth. Dr. Slepchik will take into account the colour, size, shape etc of the surrounding teeth to make sure it matches.

Maintaining Your Onlays


Onlays are a strong and stable option for minimal tooth reconstruction. Regular daily brushing and flossing, as well as your dental examination and cleaning appointments must be continued after the procedure is complete.

Alternatives To Dental Onlays

Patients may consider a dental filling or dental crown as an alternative to an onlay. Each has advantages and disadvantages. Fillings may repair teeth in a single visit. However, the application technique is generally not as durable and long-lasting as an onlay. A dental crown can provide substantial coverage for a tooth but requires more enamel reduction than is necessary with an onlay. During your visit, we are happy to discuss all appropriate treatment options based on the damage your tooth has sustained.

Are There Risks To Getting Dental Onlays?

It is uncommon to experience complications from a dental onlay. However, this procedure carries similarly minimal risks to dental crowns and fillings. There is the potential for allergic reaction to the dental anesthetic. If you’ve had a cavity filled in the past and tolerated the anesthetic injection without any reaction, you can feel confident getting your dental onlay. There is a risk of prolonged sensitivity in the treated tooth, though this side effect usually lasts only a week or two. Because our onlays are made with high-quality dental porcelain, there is no risk of allergy to the restoration itself. However, there is a risk that the porcelain could crack. Taking good care of your teeth and not chewing on hard foods or objects can help avoid this.

Can I Eat Normally With Dental Onlays?

Yes. Once your final onlay is bonded to the tooth, you can expect to resume eating normally. The onlay is made to fit into the tooth and is secured with a strong bonding material. It’s shape provides structural integrity to the tooth to withstand the normal force of chewing.

Are Dental Onlays Right For Me?

A dental onlay is a good treatment option for repair that falls in between a filling and a crown. To receive a crown would require that a fair amount of the tooth be reduced. This is necessary to allow the crown to fit over the tooth to the gumline. A dental onlay provides just the right amount of repair to fortify the tooth for normal chewing without unnecessary reduction.

How Do Onlays Differ From Inlays?

Inlays and onlays are considered indirect fillings. This means they are made outside of the mouth, similar to a dental crown. Each is made to fit the particular size and shape of a cavity. Inlays and onlays are each used on molars and premolars to repair damage that is too extensive for a traditional filling but not significant enough for a dental crown. The primary difference between the two is the part and amount of the tooth they cover. Molars and premolars have cusps, slightly raised areas, that are located at the corners and edges of the chewing surface of teeth. A dental inlay is made to fit within the cusps of a tooth. An onlay is made to fit into the biting surface as well as over one or more cusps that have been damaged.

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Is The Procedure Painful?

The dental onlay procedure is not much different from a cavity appointtment. The dentist numbs the tooth before removing the damaged enamel, so you do not experience any pain. As the tooth is being prepared for its onlay, you may feel slight pressure on your jaw. Dr. Slepchik works gently and methodically to prepare the tooth without excessive drilling and force. Using precise technique and local anesthetic, he makes sure that patients are not uncomfortable during the procedure. After the tooth has been prepared, minor sensitivity may occur. This usually resolves soon after the final restoration is bonded to the tooth, if not before.

What Is The Long-Term Outcome For Most People?

Dental porcelain is extremely strong and durable for many years. Studies estimate that between 71 and 98 percent of porcelain onlays remain functional for 5 or more years.  With good oral care, a porcelain onlay can last well over 15 years.

Schedule A Consultation

To learn more about Dental Onlays or to schedule a consultation, call Dr. Lenny Slepchik’s downtown Montreal office at 514-875-7971, email us at, or click here to send us a contact form. We are located in Downtown Montreal, next to the Fairmont Queen Elizabeth Hotel across from Place Ville Marie. Metro Mc Gill or Metro Bonaventure.

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