Biomechanics Optimum Design And Analysis Of Dental Implant Macrostructure In Type B/2 Bone

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 macrostructure plays a more important role in implant biomechanics transmission than other factor and it is more easily controlled and selected in clinical experience.At present, the mainstream implant systems are imported from abroad in the domestic market primarily and limit their application to a great extent for their high price. It is imperative that domestic researchers and manufacturers develop high quality implant products but with the lower price. Previous implant design and development researches mainly concentrated on implant materials, shape, macrostructure, surface microstructure, and implant-superstructure connection. Lots of domestic and foreign scholars have conducted massive studies in these domains. Nevertheless, many of the studies about biomechanics characteristic of implant macrostructure were discrete and independent. And these findings were insufficient to instruct us to develop and design implant with exhaustive parameters.The main aim of the present study, through the Pro/E and Ansys Workbench mechanical engineering optimum technology, was to systematically optimize implant macrostructure parameters (such as implant diameter, length, taper, thread height, thread width, thread pitch, neck taper, end filet, transgingival height) in type B/2 bone by biomechanics consideration. And this study was also to make us a better understanding about the role and effect order of each implant macrostructure parameter in biomechanics transmission. At the same time, present study was designed to provide us the detailed macrostructure parameters that were necessary to develop implant product and provided us the theoretical references for the clinical design and selection of dental implant.In 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 software. 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.In experiment 2, 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 77.4% and 68.4% respectively with D and L increasing. And under BL load, those decreased by 64.9% and 82.8% respectively. The Max displacement of implant-abutment complex decreased by 56.9% and 78.2% under AX and BL load respectively. When D exceeded 3.9mm and L exceeded 9.5mm, 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 more easily by implant diameter than implant length. Implant diameter exceeding 3.9mm and implant length exceeding 9.5mm are optimal selection for a cylinder implant.In experiment 3, implant taper (T) was set as DV. T ranged from 0°to 2.5°. OBJ setting 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 11.1% and 22.2% respectively with T decreasing. And under BL load, those decreased by 12.0% and 16.6% respectively. The Max displacement of implant-abutment complex decreased by 12.6% and 12.4% under AX and BL load respectively. When T was less than 1.2°, the tangent slope rate of OBJ response curves ranged from -1 to 0. The results imply that implant taper less than 1.2°is optimal selection for dental implant.In experiment 4, implant neck taper (T) and end fillet (R) were set as DV. T ranged from 45°to 75°, and R ranged from 0.5mm to 1.5mm. OBJ setting 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 71.6% and 11.0% respectively with T and R variation. And under BL load, those decreased by 69.2% and 14.8% respectively. The Max displacement of implant-abutment complex decreased by 9.1% and 22.8% under AX and BL load respectively. When T ranged from 64°to 73°and R exceeded 0.8mm, the tangent slope rate of OBJ response curves ranged from -1 to 1. The OBJ were more sensitive to T than to R. The results imply that implant neck taper ranging from 64°to 73°and end fillet exceeding 0.8mm are optimal selection for a cylinder implant.In experiment 5, implant thread height (H) and thread width (W) of implant were set as DV. H ranged from 0.2mm to 0.6mm, and W ranged from 0.1mm to 0.4mm. OBJ setting 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 4.1% and 38.7% respectively with H and W variation. And under BL load, those decreased by 16.4% and 54.1% respectively. The Max displacement of implant-abutment complex decreased by 46.0% and 35.2% under AX and BL load respectively. When H ranged from 0.33mm to 0.48mm and W ranged from 0.18mm to 0.30mm, the tangent slope rate of OBJ response curves ranged from -1 to 1. The OBJ were more sensitive to H than to W. The results imply that the stresses in jaw bone and stability of implant are affected more easily by thread height than thread width. Thread height ranging from 0.33mm to 0.48mm and thread width ranging from 0.18mm to 0.30mm are optimal selection for a screwed implant.In experiment 6, thread pitch (P) was set as DV. P ranged from 0.5mm to 1.6mm. OBJ setting and evaluation were same as experiment 3. The results showed that, under AX load, the Max EQV stresses in cortical and cancellous bones decreased by 6.7% and 55.2% respectively with P variation. And under BL load, those decreased by 2.7% and 22.4% respectively. The Max displacement of implant-abutment complex decreased by 22.3% and 13.0% under AX and BL load respectively. When P exceeded 0.8mm, the tangent slope rate of OBJ response curves ranged from -1 to 1. The results imply that thread pitch exceeding 0.8mm is optimal selection for a screwed implant.In experiment 7, twelve 3D FEA models with an implant of different thread shape were created: three square designs (S), three V-shaped designs (V), three buttress designs (B), and three reverse buttress designs (R). The stress distributions in jaw bones and Max displacement of implant-abutment complex were compared. The results showed that, under AX load, S-2, V-3, B-3, R-1, R-2, and R-3 showed better stress distribution than others. And under BL load, S-1, S-2, V-3, B-3, R-2, and R-3 showed better stress distribution than others. The results imply that S-2, V-3, B-3, R-1, R-2, and R-3 thread shapes all appear to be suitable for use in a cylinder implant.In experiment 8, three 3D FEA models with an implant of single-thread, double-thread, and triple-thread were created. The Max EQV stresses in jaw bones and Max displacement of implant-abutment complex were compared. The results showed that, under AX load, the Max EQV stresses in cortical bone and cancellous bone of double-thread implant increased by 10.4% and 9.2% compared with that of single-thread implant respectively. Under BL load, the Max EQV stresses in cortical bone of double-thread implant increased by 9.1% and Max EQV stresses in cancellous bone of triple-thread implant decreased by 14.2% compared with that of single-thread implant respectively. The results imply that single-thread implant appears to be suitable for use in a screwed implant.In experiment 9, implant transgingival height (H) was set as DV. H ranged from 1.0mm to 0.4mm. OBJ setting and evaluation were same as experiment 3. The results showed that, under BL load, the Max EQV stresses in cortical and cancellous bones decreased by 17.3% and 18.5% respectively with H variation. And under AX load, the Max EQV stresses in cortical bone decreased by 4.7%. The Max displacement of implant-abutment complex decreased by 4.1% and 48.9% under AX and BL load respectively. When H ranged from 1.7mm to 2.8mm, the tangent slope rate of OBJ response curves ranged from -1 to 1. The results imply that implant transgingival height ranging from 1.7mm to 2.8mm is optimal selection for a cylinder implant.To conclude, the effect order of each implant macrostructure parameter in biomechanics transmission are shown as follows: implant diameter, length, thread height, neck taper, thread pitch, transgingival height, taper, thread width, end fillet. The range of optimum macrostructure parameters are: implant diameter exceeding 3.9mm, length exceeding 9.5mm, thread height ranging from 0.33mm to 0.48mm, neck taper ranging from 64°to 73°, thread pitch exceeding 0.8mm, transgingival height ranging from 1.7mm to 2.8mm, taper less than 1.2°, thread width ranging from 0.18mm to 0.30mm, and end fillet exceeding 0.8mm.