Implant Surface Variability Between Progressive Knife-Edge Thread Design and International Organization for Standardization Thread with and Without Tapping Area: A Model Analysis

An implant's thread design plays a key role in enhancing primary stability by optimising the distribution of loading forces and biomechanical structural interlocking. An increase in bone-to-implant contact (BIC) surface availability affects osseointegration timing and leads to different biomechanical behaviours. To assess their theoretical impacts on osseointegration functionality, this study aims to analyse and compare the surface areas of two different thread designs: progressive knife-edge and V-shaped metric ISO ones. Six implant models are virtually created, with progressive knife-edge threads, non-self-tapping ISO threads, and ISO threads with tapping areas, considering two arbitrary diameters (3.8 mm and 4.6 mm). For both diameters, the models also have identical lengths (9.5 mm) and external outlines. The total, superior half, and inferior half external surface areas are measured using a digital tool (SolidWorks 2023 SP 5.0, Dassault Systèmes, Waltham, MA, USA). Then, the percentage difference in external surface area (ΔESA) is calculated. A greater ΔESA is found in the knife-edge design compared to the ISO thread self-tapping implants for the 4.6 mm diameter (ΔESA = +9.9%). However, for the 3.8 mm diameter, the ΔESA is -1.5% in favour of the ISO self-tapping model. Considering the apical half of the models, the ΔESA is always greater in the knife-edge models, varying from +9.3% to +23.5%. Implants with progressive knife-edge threads offer a significantly larger external surface area than those with ISO threads for the 4.6 mm rather than the 3.8 mm diameter. Considering the apical halves of the implants, the tapping area negatively affects the ΔESA, as well as the ISO thread design. Future research is needed to investigate whether the inspected surface area differences correspond to significant primary and secondary stability variations.