Assessment of the Effect of Abutment Size on the Tensile Strength of Crowns Cemented on One-Piece Abutments

Abutment dimension is one of the most important factors affecting the retention of implant-supported restorations. Thick abutments have the advantages of providing a thicker outer body wall and more surface area for retention. This study aimed to determine the effect of abutment dimension on the retention of implant-supported restorations.

Forty implant analogs were mounted in auto-polymerizing acrylic resin blocks with the use of a surveyor in this in vitro study. Forty titanium abutments (7 and 5.5 mm in height, and 3.5 and 4.3 mm in width) were placed on each implant analog using 30N.cm torque. The crowns were cemented with temporary cement. All the specimens were stored under 100% relative humidity at 37ºC for 48 h prior to testing. Each crown underwent a tensile force with increasing force in a universal testing machine at a crosshead speed of 0.5 cm/minute, and the tensile strength was recorded (N). The data were analyzed with two-way ANOVA using SPSS 23.

An increase in abutment height significantly increased the tensile strength (p value = 0.03). An increase in the abutment width decreased the tensile strength, but it was not significant (p value = 0.41). There was a direct and significant correlation between the abutment height-to-width ratio and restoration retention (r = 0.343, p value = 0.01). There was a direct but poor correlation between the abutments total surface (abutment height*abutment diameter) and retention (r = 0.185, p value = 0.127).

Increased abutment height and height-to-width ratio had a more positive effect on retention than increased total surface area provided by increased width.