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Background : Edentulous posterior maxilla is often associated with placement of short plateau implants due to limited available bone. However, their usage results in higher stresses in crestal cortical bone, which leads to its overload and subsequent implant failure. Biomechanical evaluation of bone-implant conglomerate and influence of bone quality and implant size on bone stresses by finite element (FE) analysis allows to compare load-bearing capacity of various implants. Aim/Hypothesis : The aim of the study was to assess stress magnitudes in cortical bone of critical thickness to verify bone capability to withstand functional loading on short plateau implants. Materials and Methods : Two short Bicon Integra-CP ™ implants of minimal (4.5x5.0 mm) and maximal (6.0x5.0 mm) diameter were analyzed. Their 3D models were placed in posterior maxilla segment models with type III and IV bone and 0.2-1.5 crestal cortical bone thickness and were completely osseointegrated. These models were designed in Solidworks 2016 software using 4-node 3D FE. Implants and bone were assumed as linearly elastic and isotropic. Elasticity modulus of cortical bone was 13.7 GPa, cancellous bone-1.37 (type III) and 0.69 (type IV) GPa. Bone-implant assemblies were analyzed in FE software Solidworks Simulation. 120.92 N mean maximal oblique load (molar area) was applied to the center of 7 Series Low 0° abutment. Von Mises equivalent stresses (MESs) in surrounding bone were calculated and compared with 100 MPa cortical bone ultimate strength to determine the ultimate functional load (UFL) for both implants. UFL magnitudes were then correlated with 275 N maximum experimental load for molar site. Results : It was found that MESs maximal magnitudes were located in crestal cortical bone. The spectrum of maximal MESs was between 14.0 and 54.0 MPa. The highest MESs were found for 4.5x5.0 mm implant placed in type IV bone with 0.2 mm crestal cortical bone, while the smallest magnitudes were calculated for 6.0x5.0 mm implant in type III bone with 1.5 mm crestal cortical bone. UFL values were in range 222…860 N. For 6.0x5.0 mm implant, UFL magnitudes were higher than 275 N for the spectrum of bone parameters: 576 N/860 N and 448 N/712 N for type III and IV bone, 0.2 mm/1.5 mm cortical bone thickness. UFL difference between 0.2 and 1.5 mm corresponded to 33% and 37% for type III and IV bone. 4.5x5.0 mm implant produced much lower UFL values: 281 N/526 N and 222 N/466 N. In order to be successful, requires at least 0.2 mm cortical layer in type III bone and 0.7 mm in type IV bone. Cortical bone decrease to around 0 mm resulted in UFL drop to 550 and 432 N (6.0x5.0 mm), 270 and 216 N (4.5x5.0 mm). Conclusions and Clinical Implications : This FE study provides a rationale for appropriate implant selection. It generally approves the clinical success of plateau implants in posterior maxilla due to their low susceptibility to poor bone quality and cortical bone thickness. It also enhances perception of implant/bone system biomechanics. The proposed method is a...

Background : Bone turnover is regulated by bone strains, their excessive magnitudes result in implant failure. Higher bone strains are common for molar regions due to larger functional loads. In the maxilla, this area is often characterized by poor bone quality and quantity, so implant function may be initially challenging. Numerical simulation is usually applied to correlate bone and implant parameters with bone strain spectrum to evaluate bone turnover and to establish implant prognosis. Aim/Hypothesis : The aim of the study was to evaluate the impact of short finned implants and crestal cortical bone height on strain level in adjacent bone to describe the bone turnover in posterior maxilla. Materials and Methods : Six Bicon short implants (4.5x5.0, 4.5x6.0, 4.5x8.0, 6.0x5.0, 6.0x6.0, 6.0x8.0 mm) were investigated. Their 3D models were placed in posterior maxilla segment models with type III bone and 0.2…1.0 mm crestal cortical bone thickness. These models were designed in Solidworks 2016 software. Bone and implant materials were assumed as linearly elastic, isotropic, implants were fully osseointegrated. Young modulus of cortical/cancellous bone was 13.7/1.37 GPa. Numerical analysis of bone-implant models was carried out in FE software Solidworks Simulation with 4-node finite elements (FEs). 120.9 N mean experimental oblique load (molar area) was applied to the center of 7 Series Low 0° abutment. First principal strains (FPSs) were analyzed in bone-implant interface. Results : Safe 520…1320 microstrain maximal FPSs were found in the crestal cortical bone, besides 6.0 mm diameter implants caused 520-660 microstrain, while 4.5 mm-780-1320 microstrain. FPSs were dependent on both cortical bone thickness and implant length. The smallest FPSs were found for scenarios with 1 mm cortical bone thickness. 4.5 mm diameter implants were more prone to cortical bone thickness than 6.0 mm: its increase from 0.2 to 1.0 mm was 32% for 4.5x5.0 mm implant and 11% for 6.0x8.0 mm implant. Critical FPSs (up to 3250 microstrain) were located in the vicinity of the first fin of 4.5 mm diameter implants. This area around 6.0 mm diameter implants was characterized by FPSs of similar magnitude as in crestal cortical bone (400-730 microstrain). Conclusions and Clinical Implications : Bone strains were influenced by implant dimensions and cortical bone thickness. 6.0 mm diameter implants caused positive bone turnover for all investigated scenarios. 120.92 N functional loading of 4.5 mm diameter implants resulted in higher strains, especially in cancellous bone, where they slightly exceeded 3000 microstrain MESp threshold by Frost. These findings should be used when planning short finned implants in posterior maxilla.

Background : Additive Manufacturing (AM) in multimaterial printing allows to create anatomical models with different mechanical properties.However, a steep transition curve exists in the mechanical properties of 3D printed parts(bone to tendon) due to the homogeneous macrostructure of the printing material. Similarly, 3D printed skin model has a lower incision and tear resistance compared to the human skin with heterogeneous tissue composition. AM Macrostructure manipulation helps in material reinforcement.Aim/Hypothesis : To design and print a material with a potential to mimic the heterogeneous nature of human tissue and increase the bond strength between different 3D printed connective tissues. To verify if this modification helps to smoothen the transition of mechanical properties among different tissues.Material and Methods : The mechanical properties of the connection between two AM materials, representing the bone and tendon, were analysed by tensile test (ISO527) in 3 groups using a uniaxial universal test machine. The first group was formed by direct connection between hard and soft homogeneous material. The second and third groups were produced with structured transition formed by a cubic grid array with and without a smooth change between the two materials, respectively. This macrostructure consisted of parametrical cubic mesh in an STL

Background : Crestal cortical bone at the implant neck is the key structural element of the jaw, which withstands the functional loading. Bone loss progression results in overloading of ìsoftî cancellous bone with the risk of implant failure. Comparing to conventional ones, short implants should be more sensitive to this issue. Plateau implants reduce the impact of bone loss, but there is no quantitative confirmation to this.Aim/Hypothesis : The aim of this study was to assess the load-bearing ability of cancellous bone on several levels of bone loss after it propagates through the crestal cortical bone.Material and Methods : Cancellous bone von Mises stresses (MESs) were proposed to evaluate load-bearing ability of fully and partially osseointegrated 4.5 (N), 5.0 (M), 6.0 mm (W) diameter and 5.0 mm length Bicon SHORT® implant on 5 levels of bone loss from 1.2 to 2.0 mm. Implant 3D models were placed crestally and bicortically in posterior maxilla segment models with type III bone and 1.0 mm cortical crestal and sinus bone. Bone models were drawn in Solidworks 2016 software. Materials were assumed to be linearly elastic and isotropic. Elasticity moduli of cortical cancellous bone were 13.7 1.37 GPa. Bone-implant assemblies were analyzed in finite element (FE) software Solidworks Simulation. 4-node 3D FEs were generated with a total number of up to 2,516,000. 120.92 N oblique load was applied to the center of 7 Series Low 0° abutment. MESs were evaluated in cancellous bone-implant interface for fully and partially osseointegrated implant and were compared.