Accuracy and Technical Predictability of Computer Guided Bone Harvesting from the Mandible: A Cone-Beam CT Analysis in 22 Consecutive Patients

Abstract

This study assesses the accuracy and technical predictability of a computer-guided procedure for harvesting bone from the external oblique ridge using a patient-specific cutting guide. Twenty-two patients needing bone augmentation for implant placement were subjected to mandibular osteotomy employing a case-specific stereolithographic surgical guide generated through computer aided design. Differences between planned and real cut planes were measured comparing pre- and post-operative Cone Beam Computed Tomography images of the donor site according to six validated angular and displacement indexes. Accuracy and technical predictability were assessed for 119 osteotomy planes over the study population. Three different guide fitting approaches were compared. An average root-mean-square discrepancy of 0.52 (0.30–0.97) mm was detected. The accuracy of apical and medial planes was higher than the mesial and distal planes due to occasional antero-posterior guide shift. Fitting the guide with an extra reference point on the closest tooth performed better than using only the bone surface, with two indexes significantly lower and less disperse. The study showed that the surgical plan was actualized with a 1 mm safety margin, allowing effective nerve preservation and reducing technical variability. When possible, surgical guide design should allow fitting on the closest tooth based on both radiological and/or intra-oral scan data.

Computer-Guided Bone Lid Technique for Surgical Extraction of Deeply Impacted Mandibular Third Molars: A Technical Report

“…As previously recommended for computer-guided bone harvesting from the posterior mandible using the same workflow as in the present investigation [33], it seems preferable to produce a template with an extra reference point on the closest tooth rather than a complete bone-borne cutting guide. Indeed, CBCT images taken before and immediately after surgery revealed an average root-mean-square discrepancy of 0.52 mm (0.30-0.97), with enhanced values recorded in the presence of an additional reference point on the nearest tooth, independently of whether it was designed considering preoperative CBCT or intraoral scan data [33]. Furthermore, the highest displacement discrepancies were registered in the mesial and distal osteotomies owing to the inaccurate placement of the template in the antero-posterior direction [33].…”

“…Computer-guided osteotomies have also been proposed for bone harvesting from various intraoral and extraoral districts with excellent results in terms of harvesting precision in relation to the planning of the desired volume of the graft and duration of the procedure [33,[35][36][37][38].…”

“…In recent years, computer-guided surgery using piezoelectric devices has been proposed for a variety of applications, including minor [28,[41][42][43][44] and major orthognathic surgery [45][46][47], extractions [29,31], endodontic surgery [34,48,49], and mandibular lesion resection [26,50], as well as cranial vault resection and reconstruction [35]. With regard to the material of the guides, several materials have been employed so far, including titanium [45], polyethylene perephthalate glycol (aka PETG) [47], polymethyl methacrylate (PMMA) [28], and polyamide [33,46], as in the current study.…”

“…By using the approach reported in the present article, case-specific stereolithographic surgical guides can be designed during the preoperative surgical planning on CBCT 3D images using dedicated software, and then manufactured through a CAM process. The position, angulation, direction, and depth of the osteotomy can be controlled during the planning phase, optimising the bone lid design [33]. The digital planning procedure allows the creation and selection of different designs.…”

“…In the context of personalised dentistry and minimally invasive oral surgery, digital planning and 3D printed surgical guides are becoming essential tools to perform accurate and predictable osteotomies in terms of location, angulation, and cutting depth. The application of computer-assisted osteotomy guides has been associated with favourable outcomes for several indications, including the removal of alveolar bone pathologies [26], orthognathic surgeries [27], corticotomy [28], tooth extraction [29][30][31], inferior alveolar nerve lateralisation [32], bone harvesting [33], and apical surgery [34].…”