Biomechanics Optimum Analysis And Selection Of Dental Implant Diameter And Length According To The Classifications Of Jaw Bone Abstract

With the outstanding advantages of the implant denture, the implant restoration has been improved dramatically in the recent decades. And more and more patients prefer to choose this new prosthodontics. Most of the studies have shown multiyear success rates of more than 90% for implants placed in patients. However implant failures were reported occasionally, including the implant fracture, loose, till the falling off. And one of main causes of implant failure is excessive load on the interface of implant and bone caused by stress centralizing, which induces the absorption of the bone around implant. To maximize the chance for long-term implant stability and function, the design and selection of dental implant should base on better biomechanics compatibility except better biocompatibility. Lots of researches have demonstrated that the factors influencing implant biomechanics transmission of occlusal forces include implant material, shape, macrostructure, anatomy shape of jaw bone, biomechanics characteristic of jaw bone and complex forces loading. And implant diameter, implant length, and jaw bone quality play a more important role in implant biomechanics transmission than other factors.Many of the previous studies examined the effect of implant diameter and length discretely and independently. So the information about the two implant parameters was not accurate and some important information was lost. The main aim of the present study, through the Pro/E and Ansys Workbench mechanical engineering optimum technology, was to systematically optimize implant diameter and length in different bone qualities by biomechanical consideration. And this study also provided us the theoretical references for the clinical optimum selection of dental implant.Experiment 1: 3D models of thread dental implant , cortical bone, cancellous bone and superstructure were constructed by Pro/E software. And the implant-bone complexes were assembled based on implant parameters by self-adapting assembled programme of Pro/E. Then the models were imported to Ansys Workbench software by bidirectional parameters transmitting of the two softwares. Self-adapting assembled 3D finite element analysis (FEA) models of dental implant-bone complexes were rebuild and the accuracy of the models was also evaluated. The self-adapting assembled models provide the technical platform for further implant optimum design and analysis.Experiment 2: In type I bone, implant diameter (D) and implant length (L) were set as DV. D ranged from 3.0mm to 5.0mm, and L ranged from 6.0mm to 16.0mm. The Max EQV stresses in jaw bone and Max displacements in implant-abutment complex were set as OBJ. The effect of DV to OBJ and the sensitivities of the OBJ to DV were evaluated. The results showed that, under AX load, the Max EQV stresses in cortical and cancellous bones decreased by 54.5% and 70.2% respectively with D and L increasing. And under BL load, those decreased by 73.5% and 75.1% respectively. The Max displacement of implant-abutment complex decreased by 51.4% and 73.8% under AX and BL load respectively. When D exceeded 3.8mm and L exceeded 9.0mm, the tangent slope rate of OBJ response curves ranged from -1 to 0. The OBJ were more sensitive to D than to L. The results imply that the stresses in jaw bone and stability of implant are affected more easily by implant diameter than implant length. Implant diameter exceeding 3.8mm and implant length exceeding 9.0mm are optimal selection for a cylinder implant in type I bone.Experiment 3: In type II bone, DV, OBJ settings and evaluation were same as experiment 2. The results showed that, under AX load, the Max EQV stresses in cortical and cancellous bones decreased by 67.9% and 75.0% respectively with D and L increasing. And under BL load, those decreased by 64.9% and 65.4% respectively. The Max displacement of implant-abutment complex decreased by 53.7% and 73.7% under AX and BL load respectively. When D exceeded 3.85mm and L exceeded 9.0mm, the tangent slope rate of OBJ response curves ranged from -1 to 0. The OBJ were more sensitive to D than to L. The results imply that the stresses in jaw bone and stability of implant are affected more easily by implant diameter than implant length. Implant diameter exceeding 3.85mm and implant length exceeding 9.0mm are optimal selection for a cylinder implant in type II bone.Experiment 4: In type III bone, DV, OBJ settings and evaluation were same as experiment 2. The results showed that, under AX load, the Max EQV stresses in cortical and cancellous bones decreased by 65.3% and 76.8% respectively with D and L increasing. And under BL load, those decreased by 76.1% and 78.0% respectively. The Max displacement of implant-abutment complex decreased by 60.6% and 77.0% under AX and BL load respectively. When D exceeded 3.95mm and L exceeded 10.5mm, the tangent slope rate of OBJ response curves ranged from -1 to 0. The OBJ were more sensitive to D than to L. The results imply that the stresses in jaw bone and stability of implant are affected by implant diameter than implant length similarly. Implant diameter exceeding 3.95mm and implant length exceeding 10.5mm are optimal selection for a cylinder implant in type III bone.Experiment 5: In type IV bone, DV, OBJ settings and evaluation were same as experiment 2. The results showed that, under AX load, the Max EQV stresses in cortical and cancellous bones decreased by 63.9% and 87.9% respectively with D and L increasing. And under BL load, those decreased by 76.2% and 92.7% respectively. The Max displacement of implant-abutment complex decreased by 63.6% and 74.7% under AX and BL load respectively. When D exceeded 4.0mm and L exceeded 11.0mm, the tangent slope rate of OBJ response curves ranged from -1 to 0. The OBJ were more sensitive to D than to L. The results imply that the stresses in jaw bone and stability of implant are affected by implant diameter than implant length similarly. Implant diameter exceeding 4.0mm and implant length exceeding 11.0mm are optimal selection for a cylinder implant in type IV bone.To conclude, stresses of jaw bone and displacement of implant increased with the changing of jaw bone qualities from type I to type IV. The influence of the implant diameter to decrease bone stress and improve implant stablity decreased, and the influence of the implant length increased. The ranges of optimum selection of implant diameter and length in different bone qualities are: in type I bone, implant diameter exceeding 3.80mm, length exceeding 9.0mm; in type II bone, implant diameter exceeding 3.85mm, length exceeding 9.0mm; in type III bone, implant diameter exceeding 3.95mm, length exceeding 10.5mm; in type IV bone, implant diameter exceeding 4.0mm, length exceeding 11.0mm.