van Dijken JWV. A 6-year evaluation of a direct composite resin inlay/onlay system and g. iass ionomer cement-composite resin sandwich restorations. Acta Odontol Scand 1994;52:368-376. Oslo. ISSN 0001-6357The most undesirable characteristic of composite resin is its polymerization shrinkage. Two techniques developed to counter this problem are the Composite inlay and the sandwich composite filling. The durability of 100 direct composite inlays and 34 closed and 16 open sandwich composite fillings made with a conventional glass ionomer cement were evaluated during a 6-year period in a group of low and high caries risk patients. Modified USPHS criteria were used. Six inlays (6%), 5 closed sandwich fillings (14.7%), and 12 open sandwich fillings (75%) needed replacement. Six other inlays and three closed sandwich fillings showed non-acceptable defects that could be repaired with composite resin. The direct composite inlays showed very good clinical durability, whereas the open sandwich filling with conventional glass ionomer cement as dentin replacement cannot be advocated as a class-II restoration.