Comparison of compressive strength of a novel hydroxyapatite tack with titanium and resorbable tacks – an in-vitro study

Abstract

The development of resorbable fixation devices has gained momentum due to limitations associated with titanium systems, including the need for device removal, soft-tissue complications, and uncertain long-term outcomes. This study introduces a novel hydroxyapatite (HA) tack designed for guided bone regeneration and evaluates its mechanical performance against titanium and resorbable copolymer tacks (L-lactide, D, L-lactide, and trimethylene carbonate). Dense HA blocks were custom-machined into tacks and tested alongside commercially available titanium and degradable copolymer tacks. All tacks ( n = 12 each) were mounted to PMMA blocks and assessed using a universal testing machine to determine maximum load and compressive strength. Measurements were analyzed using the Kruskal–Wallis test with Bonferroni-adjusted Wilcoxon rank-sum post-hoc comparisons. Titanium tacks demonstrated the highest mechanical performance, with a maximum load of 899.44 ± 190.91 N (mean ± SD) and a compressive strength of 1145.18 ± 243.06 MPa higher than hydroxyapatite (HA) tacks (maximum load of 164.09 ± 81.18 N; compressive strength: 97.53 ± 51.37 MPa) and resorbable polymer tacks (maximum load of 91.75 ± 63.57 N; compressive strength of 114.31 ± 83.26 MPa) ( p < 0.001). HA and resorbable polymer tacks exhibited similar mean values for compressive strength and maximum load ( p > 0.05). In pilot insertion testing, HA tacks did not exhibit any premature failures when inserted into human bone samples. Within the limitations of this study, titanium tack remains the strongest fixation device. The newly developed HA tack demonstrated mechanical compression strength comparable to the resorbable polymer tack and withstood insertion in bone samples without failure.