Inlays and onlays are often referred to as partial crowns. They are more conservative restorations than a full crown and are used to replace tooth structure when there is too much tooth structure missing to be restored properly with a bonded filling(*) .Old fillings, decay and fractures in the existing tooth are removed to ensure a solid base for the onlay using CEREC computer technology (CADCAM) a precise porcelain restoration is created to fit into the tooth. The restoration created is like a "puzzle piece" that replaces the missing tooth structure. This is done to strengthen the tooth, restore its shape, and prevent further damage. An inlay is done when there is no damage to the cusps of the tooth and the inlay can be placed right on the tooth. An onlay is used when the damage is a little more extensive. The restoration is bonded to the tooth structure and os virtually invisable to the naked eye, it blends with the natual tooth structure.
(*)Bonded composite fillings that are too large often expand and contract over time with thermal changes inside of your mouth(due to cold/hot liquids and food). This expansion/contraction can lead to gaps between the tooth structure and the margin of the filling. These miroscopic openings leading to areas for bacteria to enter and breakdown tooth structure causing what is know as recurrent decay
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