Fully guided implant surgery using Magnetic Resonance Imaging – An in vitro study on accuracy in human mandibles

Objectives: The objective of this in vitro study was to assess the accuracy of fully guided implant placement following virtual implant planning based on MRI. Material and methods: Sixteen human cadaver hemimandibles with single missing teeth (n = 3), partially edentulous (n = 6) and edentulous situations (n = 7) were imaged using MRI. MRI and optical scans obtained with an intraoral scanner, were imported into an implant planning software. Virtual prosthetic and implant planning were performed regarding hard- and soft-tissue anatomy. Drill guides were manufactured, and fully guided implant placement was performed. Buccal and lingual bone and implant nerve distance were measured by three examiners in preoperative MRI and postoperative CBCT. The implant position was assessed using a software for deviation of implant positions displayed in CBCT and optical scans, respectively. Results: MRI displayed relevant structures for implant planning such as cortical and cancellous bone, inferior alveolar nerve and neighboring teeth. Implant planning, CAD/CAM of drill guides and guided implant placement were performed. Deviations between planned and actual implant positions in postoperative CBCT and optical scans were 1.34 mm (SD 0.84 mm) and 1.03 mm (SD 0.46 mm) at implant shoulder; 1.41 mm (SD 0.88 mm) and 1.28 mm (SD 0.52 mm) at implant apex, and 4.84° (SD 3.18°) and 4.21° (SD 2.01°). Measurements in preoperative MRI and postoperative CBCT confirmed the compliance with minimum distances of implants to anatomical structures. Conclusions: Relevant anatomical structures for imaging diagnostics in implant dentistry are displayed with MRI. The accuracy of MRI-based fully guided implant placement in vitro is comparable to the workflow using CBCT

The impact of teeth and dental restorations on gray value distribution in cone-beam computer tomography: a pilot study

Abstract Purpose To investigate the influence of teeth and dental restorations on the facial skeleton's gray value distributions in cone-beam computed tomography (CBCT). Methods Gray value selection for the upper and lower jaw segmentation was performed in 40 patients. In total, CBCT data of 20 maxillae and 20 mandibles, ten partial edentulous and ten fully edentulous in each jaw, respectively, were evaluated using two different gray value selection procedures: manual lower threshold selection and automated lower threshold selection. Two sample t tests, linear regression models, linear mixed models, and Pearson's correlation coefficients were computed to evaluate the influence of teeth, dental restorations, and threshold selection procedures on gray value distributions. Results Manual threshold selection resulted in significantly different gray values in the fully and partially edentulous mandible. (p = 0.015, difference 123). In automated threshold selection, only tendencies to different gray values in fully edentulous compared to partially edentulous jaws were observed (difference: 58–75). Significantly different gray values were evaluated for threshold selection approaches, independent of the dental situation of the analyzed jaw. No significant correlation between the number of teeth and gray values was assessed, but a trend towards higher gray values in patients with more teeth was noted. Conclusions Standard gray values derived from CT imaging do not apply for threshold-based bone segmentation in CBCT. Teeth influence gray values and segmentation results. Inaccurate bone segmentation may result in ill-fitting surgical guides produced on CBCT data and misinterpreting bone density, which is crucial for selecting surgical protocols. Graphical Abstract Created with BioRender.co

Accuracy of Three-Dimensional Printed Templates for Guided Implant Placement Based on Matching a Surface Scan with CBCT

BACKGROUND Reference elements are necessary to transfer a virtual planning into reality for guided implant placement. New systems allow matching optical scans with three-dimensional radiographic images. PURPOSE To test whether digitally designed three-dimensional printed templates (D-temp) fabricated by matching surface scans and cone beam computed tomography (CBCT) images differ from the templates fabricated in-lab (L-temp) by using a physical transfer device for the positioning of the guiding sleeves. MATERIALS AND METHODS L-temp were fabricated for eight human lower cadaver-jaws applying a digital planning software program (smop, Swissmeda AG, Zürich, Switzerland) using a Lego® (Lego Group, KIRKBI A/S, Billund, Denmark) brick as reference element and the respective transfer device (X1-table). Additionally, digital templates (D-temp) using the identical planning data sets and software were virtually designed and three-dimensional printed, after matching a surface scan with CBCT data. The accuracy of both templates for each planning was evaluated determining the estimated coronal, apical, and angular deviation if templates were used for implant placement. RESULTS Mean coronal deviations for L-temp were 0.31 mm (mesial/distal), 0.32 mm (lingual/buccal), and 0.16 mm and 0.23 mm for D-temp, respectively. The mean apical deviations for L-temp were 0.50 mm (mesial/distal), 0.50 mm (lingual/buccal). and 0.25 mm and 0.34 mm for the D-temp, respectively. Differences between both devices were statistically significant (p < .05). CONCLUSIONS A higher accuracy of implant placement can be achieved by using three-dimensional printed templates produced by matching a surface scan and CBCT as compared with templates which use physical elements transferring the virtual planning into reality

Recommendations for implant-supported full-arch rehabilitations in edentulous patients: the oral reconstruction foundation consensus report

The tasks of Working Groups 1 to 6 at the 4th Consensus Meeting of the Oral Reconstruction Foundation were to elucidate clinical recommendations for implant-supported full-arch rehabilitations in edentulous patients. Six systematic/narrative reviews were prepared to address the following subtopics: (1) the influence of medical and geriatric factors on implant survival; (2) the prevalence of peri-implant diseases; (3) the influence of material selection, attachment type, interarch space, and opposing dentition; (4) different interventions for rehabilitation of the edentulous maxilla; (5) different interventions for rehabilitation of the edentulous mandible; and (6) treatment choice and decision-making in elderly patients. Consensus statements, clinical recommendations, and implications for future research were determined based on structured group discussions and plenary session approval