A short review on guided implant surgery and its efficiency

Ideal implant placement may reduce surgical complications, such as nerve injury and lingual cortical plate perforation, and minimize the likelihood of functional and prosthetic compromises. Guided implant surgery [GIS] has been used as the means to achieve ideal implant placement. GIS refers to the process of digital planning, custom-guide fabrication, and implant placement using the custom guide and an implant system–specific guided surgery kit. GIS includes numerous additional steps beyond the initial prosthetic diagnosis, treatment planning, and fabrication of surgical guides. Substantial errors can occur at each of these individual steps and can accumulate, significantly impacting the final accuracy of the process with potentially disastrous deviations from proper implant placement. Pertinent overall strategies to reduce or eliminate these risks can be summarized as follows: complete understanding of the possible risks is fundamental; knowledge of the systems and tools used is essential; consistent verification of both diagnostic and surgical procedures after each step is crucial; proper training and surgical experience are critical. This review article summarizes information on the accuracy and efficacy of GIS, provides insight on the potential risks and problems associated with each procedural step, and offers clinically relevant recommendations to minimize or eliminate these risks.

impacting the final accuracy of the process with potentially disastrous deviations from proper implant placement. Pertinent overall strategies to reduce or eliminate these risks can be summarized as follows: complete understanding of the possible risks is fundamental; knowledge of the systems and tools used is essential; consistent verification of both diagnostic and surgical procedures after each step is crucial; proper training and surgical experience are critical. This review article summarizes information on the accuracy and efficacy of GIS, provides insight on the potential risks and problems associated with each procedural step, and offers clinically relevant recommendations to minimize or eliminate these risks.

Background:
The placement of osseointegrated dental implants is nowadays a common procedure in periodontal clinical practice. Implant therapy is driven by the patients' restorative needs and steered by the esthetic and functional demands of each case; concurrently, implant therapy can be limited by anatomic constraints. Therefore, correct implant positioning is critical if an esthetically and functionally acceptable restoration that can be maintained through proper oral hygiene is to be achieved. Furthermore, implant placement must respect the various critical anatomic elements often present in the vicinity of a restoratively dictated implant site. Consequently, during diagnosis and treatment planning, the implant surgeon must pay close attention to both restorative and anatomic restrictions while selecting an alveolar bone site of adequate quality and quantity to ensure both appropriate and safe implant placement. Implant therapy diagnosis and treatment planning during the early years of osseointegration was based on clinical examination, study casts, and radiographs (periapical and panoramic). The inherent limitations of these two-dimensional radiographic techniques were overcome with the adoption of digital computed tomography, and, subsequently, the more widespread use of dental cone beam computed tomography that has allowed the detailed and precise three-dimensional evaluation of osseous topography [1]. Guided implant surgery refers to the process of digital planning, custom-guide fabrication, and implant placement using the custom guide and an implant system-specific guided surgery kit. It is evident from the aforementioned description that guided implant surgery includes numerous steps beyond the initial prosthetic diagnosis and treatment planning and fabrication of prosthetic radiographic guide: patient scanning, conversion of digital imaging files and importation into a software program, completion of virtual implant treatment planning, integration of a virtual model of the teeth (derived from an intraoral surface scan or an extraoral scan of stone casts) with the cone beam computed tomography model, selection and fabrication of surgical guide, and implant placement using the fabricated surgical guide [2]. In cases of immediate loading, the process typically also includes connection of the prepared provisional restoration to the implant before the patient visit is completed. The preparation of the osteotomy during static surgery is aided by patient-specific surgical guides created to transmit the virtual. Implant placement to the patient and re-create the perfect implant placement in terms of position, angle and depth [3-10]. Surgical guides can be made with the help of models, fast prototyping, or stereolithographic technologies. Model-based guides are milled or digitally printed in the lab or processed utilizing computer aided design/computerassisted manufacturing. Photopolymerization techniques based on three-dimensional imagery and design are used to create stereolithographic guides. This review aims to summarize information on the accuracy and efficacy of static guided implant surgery with special emphasis on the risks and potential problems of every step in the process. In addition, recommendations and procedures to prevent or eliminate these risks will be addressed.

Steps in guided implant surgery:
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Guided implant surgery outcomes compared to conventional implant placement:
In totally edentulous patients, the successful use of guided implant surgery combined with the simultaneous delivery of a prefabricated prosthesis for the rapid replacement of missing teeth has been described.
The use of guided implant surgery in partially edentulous patients has also been evaluated; out of 250 implants (102 patients), 58% were placed flapless, one planned implant had to be changed to a shorter one, and in four posterior cases the limited interocclusal distance presented challenges during drilling; in eight cases, implant placement had to be delayed (guides could not be used) because of required bone augmentation, and for nine of the implants the final angle differed from the planned one, without any resulting clinical consequences. When guided implant surgery with bone supported guides (n = 16) or mucosa supported guides (flapless, n = 15) was directly compared with the conventional implant placement protocol (n = 21), flapless procedures lasted significantly less time and resulted in less postoperative pain, analgesic consumption,

Clinical implications:
When using guided implant surgery the most important inaccuracy is in the vertical dimension (osteotomy depth), with inaccuracy in mesio-distal or bucco-lingual direction being clearly less. This is possibly due to the presence of debris in the implant cavity so that the implant cannot reach its final position, the resilience of the mucosal tissues in mucosa-supported guides, the setting of the gray values during segmentation, the blockage of the implant holders in the sleeves or by the crestal bone, and the deformation of the guide during surgery [45-47].

Conclusion:
Guided implant surgery can be an accurate and clinically advantageous procedure when implant therapy is called for. However, substantial errors can occur at each individual step and can accumulate, significantly impacting the final accuracy of the process with potentially disastrous deviations from ideal implant placement. It is possible to eliminate or reduce these risks, provided that complete understanding of the guided implant surgery process, thorough and careful surgical technique, advanced comprehensive training, and adequate case preparation are always in place.