 This study examined the effectiveness of under-preparation of implant insertion sites in improving primary stability. The study used three different types of implants, 3.3 mm x 13 mm, for by 13 mm, in two different polyurethane blocks, 10 and 20 PCF density, within without a cortical sheet, D1, D2, D3. The study found that under-preparation of the implant insertion sites resulted in higher insertion torques, IT, and resonance frequencies, RFA, when compared to non-under-prepped sites. Additionally, the study found that the 3.3 mm x 13 mm implant had better primary stability than the 4 x 13 mm implant when under-prepped. This article was authored by Luca Camuzzi, Margarita Tomodai, Hugo Cavani, and others.