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OBJECTIVE: This study aimed to develop a deep learning model to predict skeletal malocclusions with an acceptable level of accuracy using airway and cephalometric landmark values obtained from analyzing different CBCT images. BACKGROUND: In orthodontics, multitudinous studies have reported the correlation between orthodontic treatment and changes in the anatomy as well as the functioning of the airway. Typically, the values obtained from various measurements of cephalometric landmarks are used to determine skeletal class based on the interpretation an orthodontist experiences, which sometimes may not be accurate. METHODS: Samples of skeletal anatomical data were retrospectively obtained and recorded in Digital Imaging and Communications in Medicine (DICOM) file format. The DICOM files were used to reconstruct 3D models using 3DSlicer (slicer.org) by thresholding airway regions to build up 3D polygon models of airway regions for each sample. The 3D models were measured for different landmarks that included measurements across the nasopharynx, the oropharynx, and the hypopharynx. Male and female subjects were combined as one data set to develop supervised learning models. These measurements were utilized to build 7 artificial intelligence-based supervised learning models. RESULTS: The supervised learning model with the best accuracy was Random Forest, with a value of 0.74. All the other models were lower in terms of their accuracy. The recall scores for Class I, II, and III malocclusions were 0.71, 0.69, and 0.77, respectively, which represented the total number of actual positive cases predicted correctly, making the sensitivity of the model high. CONCLUSION: In this study, it is observed that the Random Forest model was the most accurate model for predicting the skeletal malocclusion based on various airway and cephalometric landmarks.

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This study evaluated the biomechanical performance of narrow-diameter implant (NDI) treatment in atrophic maxillary posterior teeth in aging patients by finite element analysis. The upper left posterior bone segment with first and second premolar teeth missing obtained from a patient's cone beam computed tomography data was simulated with cortical bone thicknesses of 0.5 and 1.0 mm. Three model groups were analyzed. The Regimen group had NDIs of 3.3 × 10 mm in length with non-splinted crowns. Experimental-1 group had NDIs of 3.0 × 10 mm in length with non-splinted crowns and Experimental-2 group had NDIs of 3.0 × 10 mm in length with splinted crowns. The applied load was 56.9 N in three directions: axial (along the implant axis), oblique at 30° (30° to the bucco-palatal plane compared to the vertical axis of the tooth), and lateral load at 90° (90° in the bucco-palatal plane compared to the vertical axis of the tooth). The results of the von Mises stress on the implant fixture, the elastic strain, and principal value of stress on the crestal marginal bone were analyzed. The axial load direction was comparable in the von Mises stress values in all groups, which indicated it was not necessary to use splinted crowns. The elastic strain values in the axial and oblique directions were within the limits of Frost's mechanostat theory. The principal value of stress in all groups were under the threshold of the compressive stress and tensile strength of cortical bone. In the oblique and lateral directions, the splinted crown showed better results for both the von Mises stress, elastic strain, and principal value of stress than the non-splinted crown. In conclusion, category 2 NDIs can be used in the upper premolar region of aging patients in the case of insufficient bone for category 3 NDI restorations.

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OBJECTIVES: This study aimed to investigate the stress distribution pattern of the palatal slope bone-borne expander on the maxillary area according to a different anteroposterior position of anchored miniscrews using finite element analysis. MATERIALS AND METHODS: Nasomaxillary stereolithography files with three different anteroposterior anchored miniscrew positions of the palatal slope bone-borne expander were determined as model A, B, and C. Each model consists of four supported miniscrews. Model A: two anterior miniscrews were located between the maxillary canine and the first premolar, and two posteriors between the second premolar and the first molar. Model B: two anteriors were between the lateral incisor and the canine, and two posteriors were the same as in model A. Model C: two anteriors were the same as in model A, and two posteriors were distal to the first molar. One turn of expander screws was applied. Maximum principal stress, equivalent elastic strain, equivalent von Mises stress, and transverse displacement were evaluated. RESULTS: The maximum principal stress was mostly found at the bone-miniscrew interface. Model A exhibited an intersecting area of stress between the supported miniscrews. The highest value of principal stress was in model B, while model C showed a uniform distribution pattern. The elastic strain pattern was similar to the principal stress in all models. The highest value of equivalent von Mises stress was located on the expander screw. The largest amount of transverse displacement of teeth was in model A, while model C exhibited a more consistent transverse displacement than other models. Vertical displacement of posterior teeth was also noticed. CONCLUSION: Based on the result, it revealed that the various anteroposterior miniscrew placements of the palatal slope bone-borne expander had various patterns of stress distribution and resulted in various outcomes. It may be inferred that model A's miniscrew location was advantageous for obtaining expansion quantities, but model C's miniscrew position was advantageous for maintaining consistent biomechanics.

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Due to the disadvantage of maxillomandibular fixation, the semi-rigid and rigid internal fixations have been employed to provide early mouth motion. To find the proper fixation and adequate stability, the biomechanical performance of these systems was assessed using Finite Element (FE) method. The 3D mandible model with a symphyseal fracture, teeth, periodontal ligament, and fixation devices were created for the FE analyzes. The bone structure was determined as a transverse isotropic whereas the fixation devices were titanium. The load includes Masseter, Medial Pterygoid, and Temporalis muscular forces as well as the occlusal forces acting on first molars, canines, and incisors. The maximum stress occurs at the center of fixation devices at symphyseal fracture. The maximum stress values were 877.4 MPa for the reconstruction plate and 646.8 MPa for the mini-plates. The plates maintained the fracture width at mid-region better than superior and inferior. The maximum fracture gap were 1.10 and 0.78 mm for reconstruction plate and mini-plates, respectively. The fracture site's elastic strain stabilized with the reconstruction plate was 1089.0 microstrains and with the mini-plates was 399.6 microstrains. The treatment of a mandibular symphyseal fracture using a mini-plates provides more adequate fracture stability for new bone formation and mechanically safer than locking reconstruction plate. Mini-plates fixation was able to control the fracture gap better than the reconstruction plate. Mini-plates technique was considered as the first choice of internal fixation, however, a reconstruction plate can also be used in case of unavailability and complication related to mini-plating.

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This study investigated the effects of miniscrew location on biomechanical performance of bone-borne rapid palatal expander (B-RPE) to midpalatal suture, using finite element (FE). Three cases of B-RPE with different miniscrew locations (3 and 6 mm from midpalatal suture and palatal interdental site) were simulated activations in partly ossified midpalatal suture maturation. This study compared the expansion amount and pattern along the suture line. Equivalent von Mises (EQV) stresses at appliance, miniscrew, midpalatal sutures, and elastic strain at the bone around miniscrew were evaluated. In all cases, they could not break the midpalatal suture of palatine bone. However, midpalatal suture at the maxilla was expanded. The expansion amount and unparallel expanding pattern were increased when miniscrews were positioned away from the suture. The interdental miniscrew position extended the suture more than the other 2 cases, but the pattern was unparallel. When the miniscrews were positioned away from the suture, the EQV stress at the appliance and elastic strain at the bone around the miniscrew were reduced. In the case of the palatal interdental miniscrew, all parameters were of lower magnitude. All cases could expand the partly ossified midpalatal suture maturation. The distance between the midpalatal suture and the miniscrew influenced appliance EQV stress, elastic strain at the bone around the miniscrew, and expansion characteristics.

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A novel modification of the Low Z plasty (NM-Low Z) technique for bilateral sagittal split osteotomy was recently proposed. The osteotomy line was modified more inferiorly than in the conventional Hunsuck-Epker (HE) approach. The NM-Low Z technique enhances the mandibular setback distance and degree of rotation in severe skeletal discrepancies. This study aimed to investigate the biomechanical behavior under simulated forces, and to compare the NM-Low Z and HE techniques on the mandible with Class III skeletal deformity at 1 week, 3 weeks, and 6 weeks post-operation. Physiological muscular and occlusal loads were simulated using the finite element (FE) method. Stresses on the miniplate, screws, and bone were observed and compared between the two models. The elastic strain at the fracture site was observed for the optimal bone-healing capacity. The NM-Low Z model exhibited a lower stress than the HE model at every stage post-operation. Both models demonstrated elastic strains within the normal range for bone healing. In summary, the biomechanical behavior of the NM-Low Z technique is comparable to that of the conventional EH technique. NM-Low Z could facilitate post-operation skeletal stability by reducing the stress on fixation materials during bone healing.

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PURPOSE: The biomechanical performance of a novel engineered porous-structure implant (EPSI) with various porosities and a conventional solid-structure implant (CSSI) was investigated and compared. MATERIALS AND METHODS: The three-dimensional finite element method was applied to titanium dental implant models placed in a block of bone that included both cortical and medullary bone. Five different pore sizes and porosities of the EPSI (58% porosity [PSI-58], 62% porosity [PSI-62], 71% porosity [PSI-71], 75% porosity [PSI-75], and 79% porosity [PSI-79]), were compared with the CSSI. Equivalent von Mises (EQV) stress, strain energy density, and displacement were examined for each implant design. RESULTS: The maximum EQV stresses exhibited in cortical bone of the EPSI models were lower than those of the CSSI model. Higher EPSI porosity tended to increase the EQV stress. The EPSI appeared to share the load with the cortical bone, as evidenced by lower strain energy density in the cortical bone of EPSI models. High values for displacement were observed at the coronal part of the implant in all models. Slight differences in maximum displacement values were seen between EPSI and CSSI models. CONCLUSION: The EPSI effectively reduced the maximum EQV stress in the cortical bone and enhanced the load-sharing capacity. A significant amount of energy was absorbed by the implant instead of being transferred to the surrounding cortical bone. Varying the porosity of an implant had less effect on implant displacement.

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Tissue engineering scaffold is a biological substitute that aims to restore, to maintain, or to improve tissue functions. Currently available manufacturing technology, that is, additive manufacturing is essentially applied to fabricate the scaffold according to the predefined computer aided design (CAD) model. To develop scaffold CAD libraries, the polyhedrons could be used in the scaffold libraries development. In this present study, one hundred and nineteen polyhedron models were evaluated according to the established criteria. The proposed criteria included considerations on geometry, manufacturing feasibility, and mechanical strength of these polyhedrons. CAD and finite element (FE) method were employed as tools in evaluation. The result of evaluation revealed that the close-cellular scaffold included truncated octahedron, rhombicuboctahedron, and rhombitruncated cuboctahedron. In addition, the suitable polyhedrons for using as open-cellular scaffold libraries included hexahedron, truncated octahedron, truncated hexahedron, cuboctahedron, rhombicuboctahedron, and rhombitruncated cuboctahedron. However, not all pore size to beam thickness ratios (PO:BT) were good for making the open-cellular scaffold. The PO:BT ratio of each library, generating the enclosed pore inside the scaffold, was excluded to avoid the impossibility of material removal after the fabrication. The close-cellular libraries presented the constant porosity which is irrespective to the different pore sizes. The relationship between PO:BT ratio and porosity of open-cellular scaffold libraries was displayed in the form of Logistic Power function. The possibility of merging two different types of libraries to produce the composite structure was geometrically evaluated in terms of the intersection index and was mechanically evaluated by means of FE analysis to observe the stress level. The couples of polyhedrons presenting low intersection index and high stress level were excluded. Good couples for producing the reinforced scaffold were hexahedron-truncated hexahedron and cuboctahedron-rhombitruncated cuboctahedron.

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The purpose of this study was to investigate the biomechanical effects of graft stiffness and progression of marginal bone loss (MBL) in the bone surrounding an implant placed in a maxillary grafted sinus based on the finite element method. The simulating model of graft stiffness as well as depth of MBL was varied to simulate nine different clinical scenarios. The results showed that the high-level strain distributions in peri-implant tissue increased with the increase in MBL depth when the stiffness of the graft was less than that of the cancellous bone (less stiffness graft models). The strain energy density (SED) value showed that a slight MBL depth (1.3 mm) with medium stiffness of grafted bone can reach the optimal load sharing due to the exhibited similar values of SED in the crestal cortical, cancellous, and grafted bone. With progression of MBL and the decrease in graft quality, maximal displacement of the implant increased considerably. Our results demonstrated that the effects of the two investigated factors (progression of MBL and graft stiffness) on the biomechanical adaptation are likely to be interrelated. The results also reveal that for clinical situations with poor grafted bone quality and progression of MBL, it is critical to consider implant stability.

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