## 1 Introduction  
Achieving primary stability is still a major goal in dental implant surgery for ensuring osseointegration [1, 2]. Alveolar bone quality present in a specific site, the properties of the implant system as well as the surgical technique used constitute the major determinants of primary implant stability [1; 3].  
In the past, maximizing primary stability was considered as being advantageous, especially for employing immediate or early loading protocols [4]. This was often achieved by undersizing the osteotomy relative to the implant diameter [5] and by using tapered implant macrodesigns [6], leading to compression of alveolar bone, particularly in the cortical layer. An extensive literature review [7] described initial bone resorption as occurring as a consequence of damage accumulation during implant surgery caused by thermal damage [8], underpreparation of an osteotomy [9], or by using a tapered implant compressing cortical bone [5]. At least in part, this may be seen as the reason for marginal bone level change [2; 10] around freshly installed dental implants prior to prosthetic restoration in conventional loading protocols [11; 12]. In extreme cases, the resulting high bone strains during implant installation [13] may even lead to fractures of the esthetically relevant buccal bone plate (Figure 1).  
In order to overcome the problem of mechanically overloading cortical bone, the industry started offering implants which at least in the cervical region show a triangular/trioval cross-section [14; 15]. This was done in order to reduce the stress generated in the buccal lamella of alveolar bone when the implant is placed in such a way that a flat surface of the implant coincides with the buccal aspect. However, with those implants having been in clinical use, initial reports suggest no significant difference compared to conventionally round implants [16].  
As an alternative solution, a novel implant design with sharp, cutting threads in the apical and cervical portions but blunt, condensing threads in the middle portion of the implant body, coinciding with a shift in the core diameter of the implant, has been introduced [17]. This implant has been shown to require maximum insertion torque when its bulky portion passes the cortical layer of bone and primary stability is derived from compacting trabecular bone [18; 19]. Based on two in vitro studies [17; 20], this design results in reduced buccal bone deformation during the insertion process, while at the same time, greater stability can be gained in advanced clinical situations such as sinus lifting and immediate implant placement [20]. A recent animal trial has shown that the novel implant designs allow for better maintenance of existing alveolar bone, i.e., greater undersizing of  
Figure 1: (**a**) Patient situation with an implant freshly installed in the area of the upper right canine. In this case, undersizing of the osteotomy for gaining implant stability led to a fracture of the esthetically relevant buccal bone lamella (yellow arrow). (**b**) Postoperative panoramic X-ray with two dental implants installed.  
osteotomies while not overstressing bone during the insertion process and hence leading to less marginal bone level change [21].  
Finite element analysis (FEA) is an established numerical technique in engineering and materials science and has been extensively applied for addressing biomechanical problems in implant dentistry [22; 23]. FEA allows for determining magnitudes of local stress, strain, and damage that occur during the insertion process and masticatory loading [24], thereby giving criteria to improve both implant design and insertion protocols. It was the goal of this finite element analysis to compare the novel implant design [17] to a conventional tapered implant design with respect to stress and strain generation during the insertion process. In addition, the amount of bone cut and transported during implant insertion has been quantified as an indicator of primary stability.