Inlays and Onlays

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Inlays and Onlays

Okay, so you’ve got some decay, and you think you might need a filling. But you’ve heard an inlay is better that they’re more durable, or that your damage is so extensive you might need an onlay. What the heck is the difference anyway? So glad you asked…

Let’s start with the basics

What’s a composite filling?

The decayed part of the tooth is drilled out, then filled with composite material, porcelain or metal.

What’s an inlay?

An inlay is used for larger cavities and is the material used is built outside the mouth, in a lab then cemented in place.

What’s an onlay?

An onlay is more involved than an inlay involving the cusp of a tooth but less of the tooth’s surface than a crown. It’s fabricated in a lab as well in a single, solid piece.

What’s a crown?

Although it sounds regal, it’s actually more of a tooth replacement option than a repair or restoration. It is used for more serious tooth decay. After removing the decay, a cap is placed over the entire tooth surface.

So that’s your 411 on tooth restoration options, let’s get back to why you might need inlays/onlays.

When is an inlay needed instead of a filling?

Size matters

When serious tooth decay occurs, or a filling is continually compromised, then inlays/onlays might be what you need. Inlays are similar to a filling in that they are mainly used for the inside of the tooth, but are typically used for larger cavities.

The perfect fit

Since inlays are made in a lab to the exact specifications of the tooth and cavity, they do not contract/shrink to the same degree as a filling after being placed. This means there’s less chance of the restoration failing or creating a gap between the filling and the surrounding tooth structure. Inlays provide a more durable surface when chewing, and are often recommended for molars as they are usually more reliable and last longer.

What is the difference between an onlay and an inlay?

An inlay is a pre-molded filling fitted into the grooves of a tooth that does not extend over the cusps of tooth. It’s used to repair a tooth after injury or decay causing a large cavity that does not affect the cusps of the tooth.

Onlays are used for more serious tooth restoration with larger areas of decay when a filling or inlay aren’t appropriate as a large amount of tooth structure must be removed. They involve a cusp of the tooth, while an inlay only fills the area between the cusps.

Can I always use an onlay? When do I need a crown?

Compared to a crown, an onlay is a less aggressive restoration. An onlay is preferable if possible, as less of the tooth structure needs to be removed and tooth preservation is always the ultimate goal of a dental professional. An onlay is more difficult to do correctly, so be sure to see someone from one of our offices qualified in onlay restoration.

Are inlays better than fillings? Which do you need?

Benefits of using an inlay

When an inlay is used, the tooth-to-restoration margin may be finished and polished to a very fine line of contact while direct composite filling pastes shrink a few percent in volume during hardening. This can lead to shrinkage, marginal gaps and failure. Improvements in composite resins have been made to address this problem but solid inlays prevent it completely. Another advantage of inlays over direct fillings is that there are almost limitless choices of material.

According to the American Dental Association inlays are generally more durable than fillings and provide superior durability.

Inlays offer:

  • Resistance to occlusal forces
  • Protection against recurrent decay
  • Precision of fabrication/proper contouring for gingival (tissue) health
  • Ease of cleaning
  • A replacement option for unsightly or broken fillings using tooth coloured resin, bonded to the tooth.

According to Colgate.com, your dentist is likely to recommend an inlay instead of a regular filling if the damage to the biting surface matches these criteria:

  • Broken, fractured or decayed teeth where it does not affect the cusp of the tooth.
  • It is extensive enough to require a large dental filling that may weaken the remaining structure.
  • The level of injury does not allow for removal of enough tooth material to support mounting a crown.

So why use fillings at all then?

Inlays are about ten times the cost of a composite filling and are usually reserved for larger cavities as tooth conservation is still the focus of dental professionals. Small cavities can be restored with direct composites instead, preserving more tooth. You only require one appointment for a filling.

When is an onlay needed?

When decay or fracture incorporate areas of a tooth where a composite filling isn’t possible an onlay is used. An onlay preserves more tooth structure than the next alternative which is a crown.

What is the procedure involved with getting an inlay/onlay?

The dentist drills the tooth to remove and clean out the decay in the tooth. The dentist takes an impression and sends it to a laboratory where the inlay/onlay is made. They are manufactured from porcelain or composite resin material matching the color of the tooth, providing an almost invisible dental restoration while repairing the chewing surface.

After the cavity is drilled, a temporary restoration is applied while the inlay/onlay is being fabricated in a dental lab. A return visit is required to fit the final custom-made onlay/inlay.

Did you know?

According to the American College of Prosthodontists traditionally, inlays were used instead of fillings to replace a small amount of tooth structure loss due to decay. At the time inlays were made only of gold which is still an option today though most prefer the more natural less costly option of porcelain.

If you have concerns about an existing cavity, or require tooth restoration, please make an appointment to evaluate your options.