Interface dimensions of CEREC-3 MOD onlays

Evaluation was undertaken of the interface dimensions of MOD ceramic onlays fabricated using the Cerec 3 system. A master die was prepared on a maxillary second premolar Ivorine tooth from which 20 Cerec 3 onlays and 20 feldspathic onlays were made. A total of 80 cement analogues were produced using elastomeric impression material and sectioned orthogonally. Interface dimension was measured using Image Analysis Software. The ceramic onlays constructed using Cerec 3 demonstrated significantly larger cement lute space compared with laboratory produced feldspathic porcelain onlays with mean thickness of 201.3 +/- 78.0 microm and 139.7 +/- 49.7 microm respectively (P < 0.001). Large interface dimensions were particularly noted in the proximal boxes. The multiple variables involved in the construction of the Cerec onlays as well as the complexity of the onlay design may be contributing factors to the large cement space.