Differences in Volumetric Tooth Loss for Monolithic Ceramic Crowns, Occlusal Overlays and Partial Coverage Onlays

The purpose of this in vitro study was to compare the volumetric loss of clinical crown structure for commonly encountered clinical situations for monolithic ceramic crowns, occlusal overlays, and partial coverage onlays.Typodont teeth made with pre-existing mesio-occluso-distal (MOD) preparations for mandibular first molars and maxillary first premolars were prepared with three different preparations: a full contour monolithic zirconia crown, a lithium disilicate occlusal overlay, and mesio-occluso-disto-buccal/mesio-occluso-disto-lingual (MODB/MODL) lithium disilicate onlays for premolars/molars. 3D metrological software was used to evaluate the volumetric loss of clinical crown structure for each preparation type. Subsequently, the mesiolingual cusps of mandibular molars and buccal cusps of maxillary premolars were excluded for a separate analysis, to simulate patient presentation with an existing restoration and sheared off cusp.Full coverage monolithic zirconia crowns removed 45.37 - 219.53 mm3 of remaining clinical tooth structure, depending on the clinical scenario and tooth position, while lithium disilicate overlays removed 27.48 - 105.13 mm3. MODB/MODL lithium disilicate onlays removed 5.48 - 47.45 mm3 . In each scenario tested, MODB/MODL onlays removed significantly less clinical crown structure than overlays (P<0.001); both MODB/MODL onlays and overlays removed significantly less structure than full coverage crowns (P<0.001).Monolithic zirconia crown restorations require significantly more removal of remaining tooth structure than lithium disilicate occlusal overlays and partial coverage onlays for commonly occurring clinical situations requiring indirect restorations. Int J Prosthodont 2023. doi: 10.11607/ijp.8011.