INLAYS / ONLAYS
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 the composite resins could be achieved in the last years, solid inlays do exclude this problem. Another advantage of inlays over direct fillings is that there is 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, precision of fabrication, marginal integrity, proper contouring for gingival (tissue) health, and ease of cleansing offers. However, this might be only the case for gold. While short term studies come to inconsistent conclusions, a respectable number of long-term studies detect no significantly lower failure rates of ceramic or composite inlays compared to composite direct fillings. Another study detected an increased survival time of composite resin inlays but it was rated to not necessarily justify their bigger effort and price.