## 1 Introduction  
Dental implants are widely used nowadays for the rehabilitation of edentulous jaws [1]. One of the most important aims of implant rehabilitation is implant stability [1]. This can be obtained from the mechanical relationship between the fixture and the surrounding bone at implant placement (primary implant stability), or from the biological oseeedensification process that occurs in the subsequent healing stages of the implant site (secondary implant stability) [1, 2]. Primary implant stability (PS) is influenced by several variables, such as the implant shape, the surgical procedure used and the bone quantity and quality [3, 4], whereas secondary stability is negatively conditioned by systemic factors such as age, smoking, autoimmune disease, metabolic disease, neoplasms and drug-related pathologies [5, 6, 7]. A good PS is required to enable an immediate-loading protocol and to achieve long-term stability [8]. Over the years, immediate loading of dental fixtures has been exploited due to the reduction in treatment time and trauma, and to considerations of aesthetics and the psychological wellness of the patient [8; 9].  
Many authors have noted that PS is achieved when implant micro-motion has thresholds lower than 50 to 150 \(\upmu\)m before osseointegration occurs [10]. Usually PS is easily obtainable in jaw areas that have a greater amount of mineralized bone, such as the symphysis region. Over the years, many studies have shown that the highest implant failure rates were found in the posterior areas of the jaws and that surgery plays a main role in the rehabilitation of these zones [11; 12]. The frequent lack of PS in these areas has led to the development of numerous surgical protocols that help to increase primary stability [13]. While the most common method for implant site preparation is bone drilling, this protocol increases PS only in soft bone due to under-preparation of the implant bed.  
Over the years, researchers have analyzed the shape of the implant used in addition to the surgical technique. Several authors have focused on the advantage of using a specific implant design over others in the search for primary stability. In particular, it has been highlighted that the apical portion of an implant can play a fundamental role in the osseointegration process [14; 15].  
Several surgical techniques have been developed to increase the amount of bone surrounding the fixture. In particular, researchers have aimed to modify bone quality close to the implant threads. The osseodensification drill (OD) technique uses universal tapered drills (OD) that can operate in a clockwise or counterclockwise direction, cutting or expanding the trabecular bone. These drills used in a counterclockwise direction can produce an osseous densification all along the implant site, causing plastic bone compaction [3; 16]. Recently, a manual osteotomy protocol was introduced by B&B dental implant (San Benedetto, BO, Italy), which uses customized manual bone compactors (BC) to improve bone density. This surgical protocol involves the lateral spread of the bone walls of the implant site, taking advantage of bone elasticity to deform the trabeculae slowly [17]. To analyze PS, several parameters have been proposed in the literature; among these, peak insertion torque (PIT), peak removal torque (PRT) and implant stability quotient (ISQ) are the main methods to successfully investigate the implant stability [18]. The aim of the present study was to analyze any differences between the bone compaction and osseodensification techniques and to investigate how the bone compaction technique could influence primary implant stability (PS) in cancellous bone (type III and IV). The authors hypothesized no difference exists in PS values among the procedures.