Retentive strength of implant-supported CAD-CAM lithium disilicate crowns on zirconia custom abutments using 6 different cements.
BACKGROUND
The optimal retention of implant-supported ceramic crowns on zirconia abutments is a goal of prosthodontic treatment.


OBJECTIVE
The purpose of this in vitro study was to evaluate the retentive strength of implant-supported IPS e.max CAD-CAM (e.max) crowns bonded to custom zirconia implant abutments with different cements.


METHODS
An optical scan of a zirconia custom abutment and a complete-coverage modified crown was designed using an intraoral E4D scanner. One hundred twenty lithium disilicate crowns (IPS e.max CAD) were cemented to 120 zirconia abutment replicas with 1 of 6 cements: Panavia 21 (P21), Multilink Hybrid Abutment (MHA), RelyX Unicem 2 (RXU), RelyX Luting Plus (RLP), Ketac Cem (KC), and Premier Implant (PI). The specimens were stored at 37°C in 100% humidity for 24 hours. Half of the specimens were thermocycled for 500 cycles. The retentive force was measured using a pull-out test with a universal testing machine. Mean retentive strengths (MRS) were calculated using 2-way ANOVA and the Tukey-Kramer test (α=.05).


RESULTS
The MRS (MPa) after 24-hour storage were P21 (3.1), MHA (2.5), RXU (2.5), RLP (1.3), KC (0.9), and PI (0.5). The MRS after thermocycling were MHA (2.5), P21 (2.2), RLP (1.8), KC (1.4), RXU (1.1), and PI (0.3). P21 had the highest MRS after 24-hour storage (P<.001), but after thermocycling MHA had the highest MRS (P<.001). RXU showed a significant decrease in MRS after thermocycling (P<.05). Cement residue was mostly retained on the zirconia abutments for P21, while for the other cements' residue was retained on the lithium disilicate crowns.


CONCLUSIONS
The cements tested presented a range of retentive strengths, providing the clinician with a choice of more or less retentive cements. MHA was the most retentive cement after thermocycling. Thermocycling significantly affected the retentive strengths of the P21 and RXU cements.
Former Resident, Graduate Prosthodontics, University of Texas School of Dentistry at Houston, Houston, Texas; Private practice, Dickinson, ND.
Krysta
K
Sellers
Clinical Professor of Oral Biomaterials, University of Texas School of Dentistry at Houston, Houston, Texas.
John M
JM
Powers
Clinical Associate Professor, University of Texas School of Dentistry at Houston, Houston, Texas. Electronic address: sellers.krysta@gmail.com.
Sudarat
S
Kiat-Amnuay
D017076:Computer-Aided Design; D003442:Crowns; D000044:Dental Abutments; D001840:Dental Bonding / Q000379:methods; D003738:Dental Cements / Q000627:therapeutic use*; D059605:Dental Implant-Abutment Design; D003776:Dental Porcelain / Q000627:therapeutic use*; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D003799:Dental Stress Analysis; D006801:Humans; D066298:In Vitro Techniques; D015040:Zirconium / Q000627:therapeutic use*
D003738:Dental Cements; C493120:lithia disilicate; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide