Choice of Extracoronal Restorations
The transition between an intracoronal and an extracoronal restoration is based on the amount of remaining tooth substrate following removal of decay and/or existing restorations. If sufficient dentine and enamel are present, an intracoronal restoration (direct or indirect) is the first choice of treatment. With greater tooth loss, reduced retention, coronal destruction and mutilated anatomy, an indirect extracoronal restoration is superior for restoring morphology, function, aesthetics and durability. Essentially, extracoronal restorations are classified as onlays, veneers and full-coverage crowns. The distinction between an onlay or veneer and a partial coverage crown is nebulous, and various configurations have been proposed, e.g. 1/2, 3/4, 7/8, etc. depending on the remaining tooth substrate and the type of restorative material used.
Decision-making with the informed consent of the patient depends on the following criteria:
- Minimal intervention – retaining maximum tooth structure and respecting periodontal, occlusal and pulpal health;
- Tooth integrity – strength of remaining tooth structure, and performance and durability of the chosen restorative material;
- Clinical feasibility – access for facilitating preparation, placement, impressions and cementation;
- Prognosis and survival rates – resistant to wear, occlusal forces, fractures and ease of oral hygiene procedures;
- Aesthetics – location of tooth in mouth;
- Cost – use of a dental laboratory increases fees compared to a direct approach.
Below are indications for indirect restorations:
- Cavity size – for posterior teeth with defective old restorations, the criteria for replacement depend on the size of the cavity once the restoration and decay are removed. If the occlusal width of the intracoronal preparation is greater than half the distance of the buccal and lingual cusp tips, an extracoronal restoration should be considered. In these circumstances, an onlay or f/>