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Residual alveolar ridge resorption often occurs after tooth extraction, which causes issues requiring further prothesis rehabilitation. A treatment concept referred to as all-on-four, involving fixed dentures supported with four implants, was recently developed. The current study aimed to determine the effect of changing bone atrophy and implant length in all-on-four treatments on stress and strain in the surrounding bone of the implant. A three-dimensional finite element method was used in this research. The stress analysis was conducted with von Mises stress values. Two types of synthetic jawbone models with mild and moderate atrophy were used. Furthermore, two different implant lengths with a similar implant design and diameter were selected, and they were classified into eight models. Then, the bone model was assessed via a computed tomography (CT) scan and was transformed into a virtual model in Geomagic and SolidWorks with implant rebuilding. After modifying bone atrophy, the von Mises stresses in the surrounding bone of the implant were as follows: mild type 2 < mild type 3 < moderate type 3 < moderate type 4. The bone quantity change rate increased more than when bone conditions were limited. Compared with changes in implant lengths, the stresses in the peri-implant surrounding bone were generally higher in the 9 mm implant length group than in the 11.5 mm group. However, the results did not significantly differ. In conclusion, the von Mises stress and strain increased in the models with moderate atrophy and low-density trabecular bone. Hence, bone atrophy and its presurgical diagnosis in long-term implant prognosis are crucial. [ABSTRACT FROM AUTHOR]

Background: the clinical application of orthopedic or dental implants improves the quality of the lives of patients. However, the long-term use of implants may lead to implant loosening and related complications. The purpose of this study is to deposit titanium (Ti)-niobium (Nb)-zirconium (Zr)-tantalum (Ta) alloys on the surface of Ti-6Al-4V to increase structural strength and biocompatibility for the possible future application of implants. Materials and methods: Ti, Nb, Zr, and Ta served as the materials for the surface modification of the titanium alloy. TiNbZr and TiNbZrTa coatings were produced using cathodic arc evaporation, and a small amount of nitrogen was added to produce TiNbZrTa(N) film. Annealing and oxidation were then conducted to produce TiNbZrTa-O and TiNbZrTa(N)-O coatings. In this study, biological tests and finite element analyses of those five alloy films, as well as uncoated Ti-6Al-4V, were performed. Human osteosarcoma cells (MG-63) and mouse fibroblast cells (L-929) were used to analyze cytotoxicity, cell viability, and cell morphology, and the bone differentiation of MG-63 was evaluated in an alkaline phosphatase experiment. Furthermore, for measuring the gene expression level of L-929, reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) was conducted. The three-dimensional (3D) computational models of the coated and uncoated sample films were constructed using images of transmission electron microscopy and computer-aided design software and, then, the stress distributions of all models were evaluated by finite element analysis. Result: the cytotoxicity test revealed that the surface treatment had no significant cytotoxic effects on MG-63 and L-929 cells. According to the results of the cell viability of L-929, more cell activity was observed in the surface-treated experimental group than in the control group; for MG-63, the cell viability of the coated samples was similar to that of the uncoated samples. In the cell morphology analysis, both MG-63 and L-929 exhibited attached filopodia and lamellipodia, verifying that the cells were well attached. The alkaline phosphatase experiment demonstrated that the surface treatment did not affect the characteristics of early osteogenic differentiation, whereas RT-qPCR analysis showed that surface treatment can promote better performance of L-929 cells in collagen, type I, α1, and fibronectin 1. Finally, the results of the finite element analysis revealed that the coated TiNb interlayer can effectively reduce the stress concentration inside the layered coatings. Conclusions: TiNbZrTa series films deposited using cathodic arc evaporation had excellent biocompatibility with titanium alloys, particularly in regard to soft tissue cells, which exhibited an active performance. The finite element analysis verified that the TiNb interlayer can reduce the stress concentration inside TiNbZrTa series films, increasing their suitability for application in biomedical implants in the future. [ABSTRACT FROM AUTHOR]

Clinically, a reconstruction plate can be used for the facial repair of patients with mandibular segmental defects, but it cannot restore their chewing function. The main purpose of this research is to design a new three-dimensionally (3D) printed porous titanium mandibular implant with both facial restoration and oral chewing function reconstruction. Its biomechanical properties were examined using both finite element analysis (FEA) and in vitro experiments. Cone beam computed tomography images of the mandible of a patient with oral cancer were selected as a reference to create 3D computational models of the bone and of the 3D-printed porous implant. The pores of the porous implant were circles or hexagons of 1 or 2 mm in size. A nonporous implant was fabricated as a control model. For the FEA, two chewing modes, namely right unilateral molar clench and right group function, were set as loading conditions. Regarding the boundary condition, the displacement of both condyles was fixed in all directions. For the in vitro experiments, an occlusal force (100 N) was applied to the abutment of the 3D-printed mandibular implants with and without porous designs as the loading condition. The porous mandibular implants withstood higher stress and strain than the nonporous mandibular implant, but all stress values were lower than the yield strength of Ti-6Al-4V (800 MPa). The strain value of the bone surrounding the mandibular implant was affected not only by the shape and size of the pores but also by the chewing mode. According to Frost's mechanostat theory of bone, higher bone strain under the porous implants might help maintain or improve bone quality and bone strength. The findings of this study serve as a biomechanical reference for the design of 3D-printed titanium mandibular implants and require confirmation through clinical investigations.

Background: the clinical application of orthopedic or dental implants improves the quality of the lives of patients. However, the long-term use of implants may lead to implant loosening and related complications. The purpose of this study is to deposit titanium (Ti)-niobium (Nb)-zirconium (Zr)-tantalum (Ta) alloys on the surface of Ti-6Al-4V to increase structural strength and biocompatibility for the possible future application of implants., Materials and Methods: Ti, Nb, Zr, and Ta served as the materials for the surface modification of the titanium alloy. TiNbZr and TiNbZrTa coatings were produced using cathodic arc evaporation, and a small amount of nitrogen was added to produce TiNbZrTa(N) film. Annealing and oxidation were then conducted to produce TiNbZrTa-O and TiNbZrTa(N)-O coatings. In this study, biological tests and finite element analyses of those five alloy films, as well as uncoated Ti-6Al-4V, were performed. Human osteosarcoma cells (MG-63) and mouse fibroblast cells (L-929) were used to analyze cytotoxicity, cell viability, and cell morphology, and the bone differentiation of MG-63 was evaluated in an alkaline phosphatase experiment. Furthermore, for measuring the gene expression level of L-929, reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) was conducted. The three-dimensional (3D) computational models of the coated and uncoated sample films were constructed using images of transmission electron microscopy and computer-aided design software and, then, the stress distributions of all models were evaluated by finite element analysis., Result: the cytotoxicity test revealed that the surface treatment had no significant cytotoxic effects on MG-63 and L-929 cells. According to the results of the cell viability of L-929, more cell activity was observed in the surface-treated experimental group than in the control group; for MG-63, the cell viability of the coated samples was similar to that of the uncoated samples. In the cell morphology analysis, both MG-63 and L-929 exhibited attached filopodia and lamellipodia, verifying that the cells were well attached. The alkaline phosphatase experiment demonstrated that the surface treatment did not affect the characteristics of early osteogenic differentiation, whereas RT-qPCR analysis showed that surface treatment can promote better performance of L-929 cells in collagen, type I, α1, and fibronectin 1. Finally, the results of the finite element analysis revealed that the coated TiNb interlayer can effectively reduce the stress concentration inside the layered coatings., Conclusions: TiNbZrTa series films deposited using cathodic arc evaporation had excellent biocompatibility with titanium alloys, particularly in regard to soft tissue cells, which exhibited an active performance. The finite element analysis verified that the TiNb interlayer can reduce the stress concentration inside TiNbZrTa series films, increasing their suitability for application in biomedical implants in the future.