Virtual planning and 3D-printed guides for mandibular reconstruction: Factors impacting accuracy

Evaluation of the Dimensional Accuracy of Robot-Guided Laser Osteotomy in Reconstruction with Patient-Specific Implants-An Accuracy Study of Digital High-Tech Procedures

Background/Objective: With the rapid advancement in surgical technologies, new workflows for mandibular reconstruction are constantly being evaluated. Cutting guides are extensively employed for defining osteotomy planes but are prone to errors during fabrication and positioning. A virtually defined osteotomy plane and drilling holes in robotic surgery minimize potential sources of error and yield highly accurate outcomes. Methods: Ten mandibular replicas were evaluated after cutting-guided saw osteotomy and robot-guided laser osteotomy following reconstruction with patient-specific implants. The descriptive data analysis summarizes the mean, standard deviation (SD), median, minimum, maximum, and root mean square (RMS) values of the surface comparison for 3D printed models regarding trueness and precision. Results: The saw group had a median trueness RMS value of 2.0 mm (SD ± 1.7) and a precision of 1.6 mm (SD ± 1.4). The laser group had a median trueness RMS value of 1.2 mm (SD ± 1.1) and an equal precision of 1.6 mm (SD ± 1.4). These results indicate that robot-guided laser osteotomies have a comparable accuracy to cutting-guided saw osteotomies, even though there was a lack of statistical significance. Conclusions: Despite the limited sample size, this digital high-tech procedure has been shown to be potentially equivalent to the conventional osteotomy method. Robotic surgery and laser osteotomy offers enormous advantages, as they enable the seamless integration of precise virtual preoperative planning and exact execution in the human body, eliminating the need for surgical guides in the future.

Accuracy of the modified tooth-supported 3D printing surgical guides based on CT, CBCT, and intraoral scanning in maxillofacial region: A comparison study

BACKGROUND

Tooth-supported surgical guides have demonstrated superior accuracy compared with bone-supported guides. This study aimed to modify the fabrication of tooth-supported guides for compatibility with tumor resection procedures and investigate their accuracy.

METHODS

Patients with tumors who underwent osteotomy with the assistance of modified tooth- or bone-supported surgical guides were included. Virtual surgical planning (VSP) was employed to align three dimensional (3D) models extracted from intraoperative computed tomography (CT) images. The distances and angular deviations between the actual osteotomy plane and preoperative plane were recorded. A comparative analysis of osteotomy discrepancies between tooth-supported and bone-supported guides, as well as among tooth-supported guides based on CT, cone-beam CT (CBCT), or intraoral scanner (IOS) was conducted. The factors influencing the precision of the guides were analyzed.

RESULTS

Sixty patients with 81 resection planes were included in this study. In the tooth-supported group, the mean deviations in the osteotomy plane and angle were 1.39 mm and 4.30°, respectively, whereas those of the bone-supported group were 2.16 mm and 4.95°. In the tooth-supported isotype guide groups, the mean deviations of the osteotomy plane were 1.39 mm, 1.47 mm, 1.23 mm across CT, CBCT, and IOS, respectively. The accuracy of the modified tooth-supported guides remained consistent regardless of number and position of the teeth supporting the guide and location of the osteotomy lines.

CONCLUSIONS

The findings indicate that the modified tooth-supported surgical guides demonstrated high accuracy in the maxillofacial region, contributing to a reduction in the amount of surgically detached soft tissue.

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

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.