Multicenter RCT 5-year survival of screw-retained Cerec chairside-made hybrid abutment posterior ceramic crowns

To evaluate the survival and success at 5 years of Cerec fabricated screw-retained hybrid abutment posterior ceramic crowns made in one chairside session using perforated blocks as compared to PFM crowns.

Between 2015 and 2023 a multicenter RCT including 7 sites followed 90 implant screw-retained crowns distributed on 45 molars and 45 premolars. The crown materials were PFM/gold abutment (G0, N = 30), lithium disilicate (Li2Si) IPS e.max CAD (G1, N = 30) and polymer infiltrated ceramic network, (PICN) VITA Enamic (G2, N = 30), bonded on titanium bases (TiBase). Patients were recalled once a year. Mechanical outcomes included fracture (F) for which recovered parts were analyzed using fractographic means, partial (PD) or full debonding (FD) and screw loosening (SL). Survival included critical events needing crown replacement. Success included critical and non-critical events. Kaplan-Meier survival estimates and log-rank (Mantel-Cox) test for significance at 95 % confidence level and intervals were calculated.

Survival: G0 93.3 % (2 F), G1 100 %, G2 31 % (2 F, 9 PD). Success: G0 86.7 % (2 F, 2 SL); G1 93.1 % (2 SL), G3 25.4 % (2 F, 10 PD, 1 FD, 2 SL). Partial debonding was significantly more prevalent in PICN than Li2Si (P < 0.01), occurring between the third and fifth year of observation. No statistical differences for operator-related failures were found. Enamic full thickness fractures occurred after 3.3 and 3.8 years. PFM chip fractures at years 1 and 5.

Within the limits of this study, data suggests that the Cerec fabricated hybrid abutment Enamic crowns bonded to Dentsply Sirona TiBase abutments in one chairside session are not recommended due to the high incidence of non-recoverable partial debonding events. IPS e.max CAD hybrid abutment crowns, on the contrary, performed very well in this RCT. Our findings, however, are limited to the specific set-up of Cerec hybrid abutment crown fabrication and should not be extrapolated to other existing digital workflows, titanium bases and nonperforated ceramic blocks for hybrid abutment crowns.