Strain analysis and fracture strength of different abutments for cement-retained crowns on an internal hexagon implant

Purpose: Many aftermarket abutments for cement-retained crowns are available for the Tapered Screw-Vent implant (Zimmer Dental, Carlsbad, CA, USA). Of these aftermarket abutments this is wide variation, from stock to custom abutments, as well as material differences such as zirconia, titanium, or a combination of the two. This study was performed in two parts: the aim of Part I was to measure and compare different strains conferred to the bone around the implants for nine different abutments for cement-retained crowns on an implant with an internal hexagon platform. The aim of Part II was to measure and compare the force required to cause fracture of ten different abutments for cement-retained crowns on an implant with an internal hexagon platform. Material and Methods: Nine 4.1mm x 11.5mm Tapered Screw-Vent implants were placed into a 12 x 2 x 8mm resin block for strain measurements. Five abutment specimens of each of the nine different abutments (n = 44 total) were tried into one of the nine implants. Monolithic zirconia crowns were then fabricated for each of the nine different abutments and the crowns were cyclically loaded at thirty degrees two times at a frequency of 2Hz and strain was measured and recorded. Ten Tapered Screw-Vent Implants were then individually secured in a loading apparatus, and three abutment specimens of each of the ten different abutments (n = 30 total) were loaded at a 30 degree angle until fracture of the implant abutment complex was achieved. The strain to the resin block was determined using three-dimensional digital image correlation (3D DIC), an optical measurement technique. Commercial image correlation software (VIC 3D v7.0 , Correlated Solutions, Inc. Columbia, SC, USA) was used to analyze the strain around the implants. Data for maximal and minimal principle strains as well as load to fracture were compared using analysis of variance with a Tukey-Kramer post-hoc test (alpha = .05). Results: Strain measurements showed no significant difference between any of the abutments when looking at minimal (compression) principle strains (p>.05). For maximal (tensile) principle strains the Atlantis Zirconia abutment and the Zimmer Patient Specific Abutment showed the highest and second-highest strain around the implant, respectively, with the Atlantis Zirconia being significantly greater than all abutments excluding the Zimmer PSA, and the PSA being significantly greater than the AstraTech ZirDesign and Legacy Straight Contoured abutment in titanium as well as zirconia (p