Date Published: April 15, 2019
Publisher: Public Library of Science
Author(s): C. C. Stoop, K. Chatzivasileiou, W. E. R. Berkhout, D. Wismeijer, Hermann Agis.
Recent improvements in additive manufacturing technologies may facilitate the use of customized 3D printed grafts for horizontal and vertical augmentation of the atrophic alveolar ridge. The accurate fit of such grafts could reduce the clinical treatment time and contribute optimal bone regeneration. The aim of this in vitro study was to evaluate the marginal and internal fit of 3D printed resin grafts as they could be used for alveolar ridge augmentation. Alveolar ridge morphologic data were derived from the Cone Beam Computed Tomography (CBCT) scans of six patients with alveolar bone defects. These data were transferred to a segmentation program to produce virtual 3D reconstructions of the alveolar ridge models. Using a Computer Aided Design (CAD) program, the alveolar bone defects were defined and customized grafts were designed and both the defects as well as the grafts generated (CAM) as 3D projects. These projects were imported into a 3D printer and were manufactured in resin. Hereafter, the grafts were fitted to the defect sites of the corresponding models and new CBCT scans were performed. Based on these scans, measurements were made at the marginal and internal part of the fitted grafts to evaluate the marginal and internal fit, respectively. The statistical analysis revealed that the mean marginal fit was significantly better (P < 0.05) than the mean internal fit. The fit of the grafts was dependent on the shape and on the size of the grafts. Specifically, the total void surface between the fitted graft and the corresponding defect site was significantly larger in the large-defect grafts than the small-defect grafts (P < 0.05). Within the limitations of the study, it could be demonstrated that it is possible to fabricate 3D printed resin grafts with acceptable fit in customized shapes, when combining CBCT scans and computer aided design and 3D printing techniques.
The rehabilitation of partial and fully edentulous patients with implant supported restorations has become a common treatment modality in the past few decades, showing reliable long-term results . It has been demonstrated that implant supported prostheses may have a significant impact on patient’s satisfaction and masticatory performance . One of the crucial aspects in implant treatment is the availability of bone volume for implant placement and the long-term support of functioning implant restorations .
In the present study, we evaluated the marginal and internal fit of customized 3D printed grafts for alveolar ridge augmentation in vitro. Current literature has shown only milled bone grafts and not 3D printed bone grafts, even without mentioning the values of fitting . In the present study, all grafts were manufactured and analysed using a digital workflow. In contrast with other studies, the 3D printed grafts matched the defect area, large-defect grafts without the need of further manipulation and small-defect grafts after manually smoothing the undercuts located on the model. Most studies based on milled grafts showed that bone grafts or the alveolar ridge need to be prepared prior to placing the graft [25, 26].
This study has demonstrated the possibility to fabricate customized CAD/CAM grafts in resin. The grafts were digitally designed based on CBCT scans of partially dentate patients and manufactured using 3D printing technology. When analysed with CBCT, it was shown that the CAD/CAM resin grafts could fit on the recipient sites. The marginal fit of the grafts was better than the internal fit, while the average void dimensions seemed to be correlated to the defect type of the graft. Further in vitro studies with 3D printable bone substitutes are needed for the validation of this digital workflow for alveolar bone augmentation.