## 1 Introduction  
Implant rehabilitation in cases of monoedentulism in the esthetic area is a challenge for the clinician [1]. Indeed, the increase in the patients' esthetic expectations and the emotional and social implications that the loss of an incisor generates require extremely precise and accurate treatments. In these cases, to solve the edentulism with implant-supported prostheses that replace the esthetic and function of the natural teeth is mandatory [2]. In the esthetic area, the bone profile of the maxillary alveolar process and the incisor's inclination make immediate or delayed implant placement more difficult [3, 4]. Consequently, an extremely precise implant placement is critical in order to maintain an adequate bone tissue volume around the implant and a soft tissue architecture comparable to that of the adjacent natural teeth [5, 6, 7]. Implant osteectomies should be prepared in the centre of the edentulous space, with a minimum distance of 1.5 mm from adjacent teeth and preserving a thickness of about 2 mm of the buccal cortical bone to protect the implant [8]. The inclination of implant insertion should coincide with the ideal loading axis in order to expose the implant bone system to compressive forces that stimulate the formation of reactive bone tissue [9; 10]. Structural integrity and thickness of the vestibular cortical bone are key factors in predicting the extent of bone resorption and dehiscence of the soft tissue lining [11]. In fact, for bone thicknesses > 1 mm, the success rates of dental implants placed both immediately and after complete soft tissue healing (4-8 weeks after extraction) are higher [12]. On the contrary, for buccal cortical bone thickness < 1 mm, the formation of greater bone and mucosal defects has been observed and, in these cases, the application of bone augmentation techniques is necessary [13]. For these reasons, an accurate implant placement, considering implant axis and the residual bone volume, is mandatory to avoid esthetic complications, both in the short and medium term [14]. In order to obtain an accurate implant insertion, a careful preoperative planning that considers both the volume of the hard tissues and the positioning of the future prosthesis is necessary [15; 16]. Subsequently, an appliance to transfer the planning information to the operating field is required to obtain predictable and reproducible implant insertion on the patients. Several prosthetically guided implant placement techniques are described in the literature. A review conducted by [PERSON] et al. differentiates between static and dynamic guided techniques. Static technique concerns the stereolithographic process, which involves the development of a 3D printed template from digital planning performed on software with CT data importation. Dynamic technique makes use of computer-navigated surgery, which allows the surgical instrument to be tracked as it is used, thanks to optical tracking technology [17]. A review by [PERSON] et al. analyzed the advantages and the disadvantages of computer-guided therapeutic protocol. They reported a reduction of intraoperative times, especially in the most complex cases and the possibility to perform a flapless procedure, decreasing the postoperative discomfort of the patient. However, an increase in preoperative times and costs were revealed. In addition, each additional step during the preoperative planning can be associated with an increased risk of deviation in implant placement if compared with the ideal implant positioning [18]. There are also different protocols in the literature concerning the timing of implant insertion. Immediate (or posttextractive) implants are defined as those placed in a fresh extraction socket just after tooth extraction, immediate-delayed implants are those placed in an extraction socket within 8 weeks after tooth extraction, and delayed implants are any implants placed at least 2 months after tooth extraction [19].