## 1 Introduction  
One of the most critical prerequisites for achieving mineralized bone at the interface with dental implants is Primary Stability (PS) [1]. This latter depends on various factors,including bone quality and density, implant micro-geometry, thread shape, and surface characteristics. Equally important is the interaction between the macrostructure of the implant threads and the implant site [1]. Generally, two main strategies aim to achieve mineralized bone at the implant-bone interface. One involves achieving a close adaptation between the implant and bone, especially in underprepared surgical sites. The other strategy creates empty spaces between the implant and the surrounding bone, leading to the formation of the so-called healing chambers [2]. In the first case, very high PS is often achieved through peri-implant bone compression. However, this can potentially lead to bone necrosis and a subsequent decrease in PS in the weeks following implant insertion. High Insertion Torque (IT) values can indeed damage the implant-abutment connection [3]. Nevertheless, the optimal surgical technique, implant macro-geometry, and IT values to achieve maximal bone formation in the peri-implant space, particularly in low-density and low-quality bone, remain unknown [4; 5; 6]. The concept of a healing chamber was introduced to mitigate peri-implant bone compression and the potential for bone necrosis [1; 2]. This could be attributed to the voids created between the implant's macro-structure and the bone hole site, which are promptly filled with a blood clot following implant insertion. Subsequently, new bone formation occurs through an intra-membranous process [2]. Recent developments have led to the creation of mathematical and biomechanical models for in vitro testing of implant-supported prostheses under various loads [7; 8]. Specifically, rigid polyurethane foam, recognized as an isotropic and homogeneous material, has become a standard prototype as per the American Society for Testing and Materials (ASTM F-1839-08 \"Standard Specification for Rigid Polyurethane Foam for Use as a Standard Material for Testing Orthopaedic Devices and Instruments\") [9]. This foam is employed for testing and demonstrating orthopedic implants, instruments, instrumentation, and for examining force distribution around dental implants in various anatomical locations [10; 11; 12]. In particular, the polyurethane foam blocks are designed to closely mimic natural bone density, as classified by [PERSON] based on density, trabecular cortex, and micro-structure into four categories: D1, dense cortical bone and poor/absent trabecular bone (mandible symphysis); D2, cortical and dense trabecular bone tissue (mandible and anterior maxilla); D3, thin cortical and trabecular bone (mandible and anterior/posterior maxilla); D4, poor/absent cortical and thin trabecular tissues (posterior maxilla) [13]. [PERSON] et al. [4] conducted an in vitro study using polyurethane blocks with low-density rated at 10 and 20 pounds per cubic foot (PCF) to assess the IT, Removal Torque (RT), and Implant Stability Quotient (ISQ) of implants with two different micro-geometries. In all tested groups, implants initially placed in the 10 PCF density blocks exhibited relatively low stability. However, the employment of undersized osteectomies notably increased the measured values in all 20 PCF density blocks. These authors reported that even with a modified (undersized) osteotomy technique, implants inserted into the low-quality bone (Type IV bone) can pose challenges to achieve osseointegration due to their limited initial stability and resistance from the bone. Modifications to the implant macro-geometry, such as the incorporation of healing chambers, resulted in increased bone presence on the implant surface following pullout testing. In 2023, the same authors [14] conducted a clinical study involving 70 patients and 100 implants featuring two different micro-geometries, some with healing chambers and some without.