Three-dimensional comparison of the maxillary surfaces through ICP-Type algorithm: accuracy evaluation of CAD/CAM technologies in orthognathic surgery

Purpose: This retrospective study aims to compare the accuracy of two different CAD/CAM systems in orthognathic surgery. The novelty of this work lies in the method of evaluating the accuracy, i.e., using an Iterative Closest Point (ICP) algorithm, which matches a pair of 2D or 3D point clouds with unknown dependencies of the transition from scan s(k) to scan s(k+1). Methods: The study population was composed of ten patients who presented to the Maxillofacial Surgery Department of the University “Sapienza” of Rome for the evaluation and management of skeletal malocclusions. The patients were divided into two groups, depending on the technique used: group 1: splintless group (custom-made cutting guide and plates); group 2: splint group (using a 3D-printed splint). STL files were imported into Geomagic® Control X™ software, which allows for comparison and analysis using an ICP algorithm. The RMSE parameter (3D error) was used to calculate the accuracy. In addition, data were compared in two different patient subgroups. The first subgroup only underwent a monobloc Le Fort I osteotomy (p-value = 0.02), and the second subgroup underwent a Le Fort I osteotomy associated with a segmental osteotomy of the maxilla (p-value = 0.23). Results: Group 1 showed a 3D error of 1.22 mm ± SD 0.456, while group 2 showed a 3D error of 1.63 mm ± SD 0.303. These results have allowed us to compare the accuracy of the two CAD/CAM systems (p-value = 0.09). Conclusions: The ICP algorithm provided a reproducible method of comparison. The splintless method would seem more accurate (p-value = 0.02) in transferring the surgical programming into the operating room when only a Le Fort I osteotomy is to be performed

STUDY ON THE OVERSTRENGTH OF HEA EBFS LINKS BY FEM SIMULATIONS

In this paper, numerical analyses of detailed finite element models (FEM) have been carried out to verify the combined influence of link length, boundary conditions and stiffener spacing on the plastic overstrength of “I shaped” HEA links for eccentrically braced frames. Parametric analysis has been carried out by means of FEM simulations under cycling loading where the accuracy of the model is validated on the bases of experimental tests. From the results, it has been observed that the axial boundary conditions play an important rule on the increment of the overstrength factor of HEA links. It has also been pointed out as, in presence of axial restraints, the link member never yields for axial load

Method to evaluate the need to perform a reconfiguration step of two or more photovoltaic panels

Over the recent years, new oral anticoagulant agents have been developed and entered the clinical arena, the non-vtamin K or direct oral anticoagulants (NOACs). Although more expensive, these agents have been proven as equivalent or superior to vitamin K antagonists in the treatment of non-valvular atrial fibrillation (AF) and venous thrombo-embolism with a lower incidence of intracerebral hemorrhage. Nevertheless, occurrence of major or life-threatening bleeding events is still quite possible. Thus, there is a major concern regarding the lack of a specific antidote and rapid reversal agent in such disastrous situations. Fortunately, the development of effective specific NOAC antidotes has recently made great advances, which are herein briefly reviewed

Reconstruction of the mandibular symphysis: pilot study compares three different flaps

BACKGROUND: Restoration of mandibular continuity, functionality and attempting to return patients to their premorbid state is the ultimate goal of reconstruction. Some studies compare different flaps but the reconstructed portions vary and there is little consensus on the best option for a particular defect. METHODS: This pilot study compares three different reconstructive options with free flap. We will analyze the accuracy of the reconstruction, the post-operative complications related to the reconstruction, the morbidity of the donor site. This pilot study compares three different reconstructive options with free flap in the reconstruction of the mandibular symphysis: iliac crest, scapula and fibula. RESULTS: In our sample the morbidity of the donor site was overlapping, as for all three choices free from complications. In post resection edentulous patients, the fibula seems to guarantee better positioning, while in patients with residual occlusion the iliac crest (figure n.4 and n.5) seems to allow a more congruous repositioning. The fibula seems to have a superiority over the other flaps in terms of accuracy in all types of patient. CONCLUSIONS: Contrary to the most recent work on the accuracy of CAD / CAM, we have analyzed the error in the reconstruction of a specific segment and in the repositioning of the residual mandibular component without the use of guided computer programming