The present study aimed to evaluate the impact of the existence of an abutment screw-access hole and the filling effects on the
fatigue mechanical behavior of a luted
lithium-disilicate glass-ceramic. Seventy-two discs (Ø = 10 mm, 1.0 mm in thickness) of
lithium disilicate (IPS e.max CAD,
Ivoclar AG) were obtained from prefabricated blocks. Thirty-six abutment specimens of an opaque
zirconia (Yz - IPS e.max ZirCAD,
Ivoclar AG) and
titanium (Ti - Luminesse Ti-Cam discs, Talladium Inc.) were confectioned, and allocated according to 6 groups: Yz and Ti rigid (without screw access hole); Yz unfilled, Yz filled, Ti unfilled and Ti filled (with the screw access (Ø = 2.5 mm) in the center). For the unfilled groups, only a
polytetrafluoroethylene tape was used.
Resin composite (
Tetric N-Ceram,
Ivoclar AG) was applied to the screw access hole for the filled groups (Yz and Ti). A cyclic
fatigue test was carried out (load of 200 N, 10,000 cycles each; 20 Hz of frequency, step size of 100 N until failure detection (radial/cone crack). The
fatigue failure load (FFL) and number of cycles until failure (CFF) were recorded for statistical purposes. The stress distribution (MPa) was evaluated by finite
element analysis. A statistically positive effect of the abutment material and the presence of the screw access hole was observed (p ≤ 0.05). The rigid groups (without screw access holes) depicted almost 100% of survival after the
fatigue tests. Among the other groups, the Yz-filled group showed the best performance (p ≤ 0.05), followed by the Yz unfilled group. The Ti groups depicted lower values of FFL and CFF, with the Ti unfilled group showing the most unfavorable
fatigue behavior (p ≤ 0.05). The lowest tensile stress concentration in the restorative material was observed with the use of rigid abutments, the filled groups depicted intermediate values, while unfilled groups showed the highest stress concentration (Yz rigid = 306.3 MPa; Ti rigid = 310.4 MPa < Yz filled = 490.7 MPa; Ti filled = 498.9 MPa < Yz unfilled = 707.6 MPa; Ti unfilled = 719.7 MPa). Therefore, the presence of a screw-access hole decreases the mechanical performance of a
lithium disilicate ceramic regardless of the abutment material. In the presence of a screw-access hole,
zirconia abutments depicted a higher
fatigue failure load when compared with
titanium. The filling of the abutment screw-access hole with
resin composite increased the mechanical performance of the simulated restoration.