Contact Damage of New Chairside CAD/CAM-materials for Full Posterior Crowns

Objectives: New CAD/CAM-materials, consisting of ceramic and polymer, are available for chairside dentistry. Due to their polymer component, they are less brittle than pure glass ceramics, so they are advertised for patients with higher masticatory forces. Previous studies analyzed the abrasion related to contact damage of these new materials. However, this method characterizes only the outer contact damage. Thus, it was the aim of this in vitro study, to investigate the inner contact damage after loading and compare the results with etablished lithium disilicate ceramics IPS e.max CAD (Ivoclar Vivadent).

Methods: To manufacture standardized specimens, one crown-STL-file and one die-STL-file were constructed for a posterior tooth. 96 CAD/CAM-fabricated crowns (16 IPS e.max CAD (EX); 16 Lava Ultimate Restorative (LU), 3MEspe; 16 Vita Enamic (VE), Vita Zahnfabrik; 16 Brilliant Crios (BC), Coltene; 16 Cerasmart (CS), GC; 16 Experimental-Block (EB)) were milled and cemented on 96 identically CAD/CAM-milled human molars with their corresponding luting systems. Following, the specimens were artificially aged in a chewing simulator by cyclic loading (prematec F1000) for 1,000,000 cycles (5-500 N, 2 Hz, 37°C). A dye penetration test was performed to detect inner contact damage. For inspection, digital microscope (Smartzoom 5, Zeiss) was used. Statistical analysis was performed by Wilcoxon rank-sum test.

Results: EX (Mean, Interquartil Range: 28.4%, 23.8-33%) showed the highest damages followed by VE (56.4%, 49.4-63.5%). LV (76.1%, 68.1-84.1%), BC (80.15%, 74.1-88.7%), CS (84.1%, 76.3-91.9%) and the EB (73.9%, 68.4-79.6%) showed the lowest damages. There was a significant difference between EX, VE and all four other tested groups (p< 0.05).

Conclusions: Overall, the results demonstrate the potential of new CAD/CAM-materials for patients with higher masticatory forces. Within the limitation of this in vitro study, hybrid ceramics can be recommended for clinical use.