Inlays, onlays and overlays

Inlays, onlays and overlays are used to restore cavities that are too large and cannot be repaired through simple esthetic fillings, but can be resolved without placing a dental crown. The necessary preparation is somewhere between the two, so when the size of the cavity permits it, we will choose the more conservative solution, in order to preserve as much natural tooth structure as possible.

Here’s what you need to know about inlays, onlays and overlays:

• The pieces, also known as “indirect fillings”, are manufactured in the Dental Laboratory and are permanently cemented to the remaining tooth.
• They can be made of composite, ceramic or
• As long as they are properly cared for, further decay will be prevented.
• They are more long-lasting than direct esthetic fillings.
• They are used for damaged lateral teeth (premolars and molars) because they can strengthen their structure enough to restore chewing function completely.
• The preparation is reduced compared to that for a crown.

Normally two sittings are required for this procedure (a temporary restoration will be used in between the two):

• Tooth preparation and impression (the impression is sent to the Lab)
• The restoration is cemented on the prepared tooth.

What is the difference between inlays, onlays and overlays?

The classification is based on a few factors like: the area of the tooth that needs to be replaced, the size of the cavity and, consequently the prosthetic piece’s its extent in the hard tissue. The architecture of the preparation will always follow conservative principles, but will be projected so that maximum resistance is achieved. So, in the first visit, a suitable type of indirect filling will be chosen, depending on its shape and coverage as such:

Inlays are inserted on the chewing surface of the tooth; they are always surrounded by healthy tissue. The inlay usually restores cavities that are formed in the central pits and ridges of the tooth.

Onlays are larger than inlays, they will also cover one or more of the cusps. This type of indirect filling is required when the preparation extended to the pointed parts of the tooth (the cusps). This happens sometimes when tooth decay has left the tooth with not enough supporting tissue to sustain the direct bite load.

Overlays are similar to onlays but they cover an even larger area of the biting surface. Sometimes these are called “partial crowns” or “table-tops” because of their shape, but they aren’t necessarily always the same. The main principle is that they will spread the pressure from the bite uniformly, so the possibility of fracture is significantly reduced.

When choosing one over the other, the state of the remaining tooth walls is very important. Indirect fillings will only be applied when we have:

• Healthy dental pulp.
• No chipping or cracks of the enamel.
• Healthy opposing teeth surfaces.
• Correct or corrected bite loading.
• Good oral hygiene.

Benefits and drawbacks

Inlays, onlays and overlays will fit inside the tooth preparation like a piece of a jigsaw puzzle, so their fit is highly superior compared to a direct filling and they will also last longer.

The ceramic inlays, onlays or overlays can be designed (in the Dental Laboratory) to look exactly like a natural tooth, so in addition to restoring lost tissue and bite function, they also have excellent esthetical qualities.

When used for cavities between teeth, because they are custom made, a better contact surface can be obtained, so the gingival tissue is better protected against trauma and inflammation. The risk of secondary decay is almost eliminated.

Onlays and overlays can also be used to help recover intermaxillary relations and establish a proper TMJ position in complicated cases, where we have entire arches severely affected by bruxism (teeth grinding), bite trauma, errosion and other dental issues.

All things considered; they do have some strict contraindications. If the tooth is highly affected by decay or a very large part of the facial and inner surface is damaged, then dental crowns are a better solution.

Even though the indirect fillings are more expensive than classic fillings, the many advantages and benefits they offer easily compensates for the extra cost: longevity, dental health maintenance, esthetics.

Caring for an inlay, onlay or overlay

Caring for an indirect filling is very similar to caring for a direct esthetic filling or for a dental crown:

• Brush your teeth at least twice a day (morning and evening) and clean between your teeth with floss and / or a waterpik every day.
• Use the oral care products recommended by our doctors to ensure that they meet the appropriate safety and efficacy standards for your particular case.
• As with natural teeth, it is advisable to avoid extremely hard foods, chew ice or other hard objects, such as pencils or fruit kernels.
• Be sure to schedule regular check-ups and professional teeth cleanings at our clinic.
• regular check-ups and professional teeth cleanings at our clinic.