Total 90 stock titanium abutments (Anyridges; MEGAGEN, Seoul, Korea) with different angulations and collar lengths were used in this study and divided into three groups, 30 each according to the degree of abutment angulations GI 0° abutment, GII 15° abutment, and GIII 25°. Each group was divided into two subgroups, 15 each according to implant abutment collar lengths: subgroup A (2 mm) and subgroup B (4 mm). For each sample conical hybrid connection implant, 4.5 mm diameter × 10 mm length bone level implants with platform-switching were used. Titanium abutment screw was used (Fig. 1).

Ninety auto-polymerized acrylic resin blocks were prepared for this study using a stainless steel split cylindrical mold with 20 mm length, 20 mm width, and 2.5 in. thickness. A stainless steel base was made wider than the split cylinder, so it can be seated inside this base. At the center of the base, small opening with the same diameter of implant abutment was made so it can help implant abutment assembly to be centralized vertically in the acrylic resin block. Split cylindrical mold was cleaned and dried; then, vaseline was applied into the whole internal surface to ensure separation of acrylic block from the mold. Implant fixture and abutment were screwed through the hole in the stainless steel base.

The auto-polymerized acrylic resin powder and liquid were mixed according to the manufacturer’s recommendation, poured inside the split cylindrical mold, and left for polymerization. After polymerization, implant fixture was unscrewed from abutment to separate the split cylinder from the stainless steel base; then, the cylinder was removed showing the acrylic resin block with implant fixture centralized vertically and perpendicular to the base and the platform was flushed with acrylic resin block level. Finishing and polishing were made, using micromotor, by red and white stone (Fig. 2).

Ninety stock titanium abutments were selected with post length of 7 mm; each abutment had titanium screw with same length, diameter, thread, and head design for each group. For each selected abutment, metal tube was fabricated to fit accurately on the abutment. The titanium abutment was mounted on the fixture which was prepared to be scanned with a 3D scanner (Smart optics, England). The desired design and dimensions of metal tube was designed by CADCAM software (Dentcreate, Exocad) in wax (CopraDur, White peaks dental solution, Germany), with flat occlusal surface (10 mm in diameter) which was parallel to the horizontal plane and perpendicular to the implant fixture long axis to permit contact with the testing machine piston in a flat horizontal plane. In the center of the flat occlusal surface, a small rounded hole was designed exactly opposite to the abutment screw hole that facilitates screw driver accessibility for easy tightening and removal. Then, this accurately designed wax pattern was casted to a nickel chromium alloy tube (Fig. 3).