Conventional dental methods of placing crowns usually require two appointments. During the first one, the dentist prepares the tooth, takes an impression and places a temporary crown. The temporary is usually on for 2-3 weeks. During that time lots of things can happen: the tooth may become sensitive or start hurting, it can break, or the temporary may pop off. The E4D system eliminates the waiting period for a final restoration saving you from possible discomfort and the time of having to come back.
Sometimes, a tooth is planned to be restored with just a normal filling, but the decay or fracture is so extensive that a direct restoration would compromise the structural integrity of the restored tooth. In such situations, an indirect inlay restoration may be used. When an inlay is used, the tooth-to-restoration margin may be finished and polished to a very fine line of contact to minimize recurrent decay. Opposed to this, direct composite filling pastes shrink a few percent in volume during hardening. This can lead to shrinkage stress and rarely to marginal gaps and failure. Although improvements of composites have been achieved in the past few years solid inlays do exclude this problem. Another advantage of inlays over direct fillings is that there are almost no limitations in the choice of material. While inlays might be ten times the price of direct restorations, it is often expected that inlays are superior in terms of resistance to occlusal forces, protection against recurrent decay, the precision of fabrication, marginal integrity, proper contouring for gum health, and ease of cleansing offers.
An Overlay is like a crown which covers the entire surface of the tooth but instead of destroying perfectly healthy tooth which a crown would do we will only prepare the damaged part and taking off little as possible. Compared to the size of inlays and onlays, overlays do cover more of the tooth giving it a skull cap design to it.
When decay or fracture areas of a tooth that make amalgam or composite restorations impossible to place because of factors such as cuspal fracture or remaining tooth structure that undermines perimeter walls of a tooth, an onlay might be indicated. Similar to an inlay, an onlay is an indirect restoration which incorporates a cusp or cusps by covering or onlaying the missing cusps. The onlay allows for conservation of tooth structure when the only alternative is to totally eliminate cusps and perimeter walls for restoration with a crown. Just as inlays, onlays are fabricated outside of the mouth.