Background: The primary stability is a determinant clinical condition for the success of 25
dental implant procedure. The aim of this study was to investigate the primary stability of three 26
different dental implants macro-design in different bone density using a validated and repeatable 27
in vitro technique employing solid rigid polyurethane blocks. Materials and Methods: Five im-28
plants 3.8x13mm for each macro-design (i.e. IK – tapered; IC – cylindric; and IA – active blade shape) 29
were positioned into 20- and 30- pounds per cubic foot (PCF) polyurethane blocks. Bucco-lingual 30
(BL) and mesial-distal (MD) implant stability quotient score (ISQ) was assessed by resonance fre-31
quency analysis while, insertion/removal torques were evaluated by dynamometric ratchet. Re-32
sults: IC implants shown better primary stability in terms of ISQ compared to IA and IK in lower 33
density block (20 PCF), while IK was superior to IA in higher density (30 PCF). IC shown higher 34
removal torque in 30-PCF compared to IA and IC. Conclusions: Our evidence showed that im-35
plants macro-design might represent a key factor on primary stability, in particular on low-density 36
alveolar bone. Clinicians should consider patients features and implant geometry during low-den-37
sity jaws rehabilitation. Further investigations are needed to generalize these findings.