Dental inlays are a type of indirect dental restorations. This means that they are not constructed directly in the mouth, as conventional fillings are (composite resins and amalgams) but instead are manufactured out of the mouth in the dental laboratory and are later cemented on the tooth. Dental inlays are also said to be intracoronal restorations. This means that they are placed within the contours of a cavity in the tooth as opposed to crowns or veneers that are cemented outside of the surface of the tooth.
Simply stated, one can say that inlays are fillings that are constructed out of the mouth through a mold or impression that your dentist takes and are later cemented on the tooth. They are indicated when the tooth is more destroyed than what would be considered restorable for a direct filling, but not as much as to need a crown . It is an intermediate restoration in terms of how invasive it is for tooth structure.
Historically they were very frequently used in the past, mainly constructed in gold. These are the famous “gold fillings” that we used to see often and were the only alternative to very large amalgam restorations that could easily fracture. Nowadays, gold restorations are seldom used due to the high cost of gold and for esthetic reasons. There have also been developed different materials and techniques that have improved the clinical outcome of these restorations. Newer ceramic and polymeric materials can be adhered chemically to tooth structure unlike metals that could only be cemented. This characteristic and the fact that they exhibit a high esthetic potential have made these restorations more common. They have a very high success rate and longevity while they protect teeth from different forces and adverse situations in the mouth.