Preliminary Study Of The Palatal Subperiosteal Implants Supporting Obturator To Restore The Defective Maxillae

Part 1:Feasibility study of the palatal subpeiosteal implants supporting a maxillary obturator to restore a animal maxillary defect modelObjective To rehabilitate a maxillary defect model by means of palatal subperiosteal implantation and evaluate the outcome.Methods Following the placement of two customized subperiosteal implants on the remaining palate 6 weeks before,a special implant-supported maxillary obturator had been inserted in the oral cavity of a pig with a defective maxillae,with which the masticatory performance of the obturator could be measured weekly during the 5-week follow-up.Detaching forces were measured and scanning electron microscopy was used to determine the mechanical property and the kinds of implant-tissue integration after sacrifice.Results The masticatory performance significantly increased by 121%at 1 week and 84%at 3 weeks after implantation(P＜0.01). The pull-out loads of the two subperiosteal implants were 108N and 61N respectively.SEM examination revealed identical fibrous integration of the subperiosteal implants.Conclusion The palatal subperiosteal implant is recommended as a promising means in the prosthetic rehabilitation of maxillary defect for edentulous patients by this pilot study.Part 2:Comparative evaluation of tissue integration of the SIs with two different shapesObjective To compare the tissue integration of the SIs with two different shapes so that to choos the better design of the palatal SI.Methods Six pigs were divided into 2 groups,with 3 pigs in each group,and a total of 24 SIs,2 lattice and 2 mesh shapes,were fabricated and impanted on the calvarium of each pig.The pigs were sacrificed after 4 weeks,and the integration of the implants was evaluated biomechanically using pull-out test,histologically by light microscope,scanning electron microscope and X-ray energy dispersive analysis.Results Of the 18 SIs who healed normally,2 were osseointegration and 7 were fibrointegration in each kinds of SIs.The pull-out force of the mesh-shape SI was higher than that of the grid-shape SI by 29%(P＜0.05)while there was no difference in implant-tissue attachment strength(P＞0.05).Conlusion With the same implant area,the mesh-shape SI will present a greater implant-tissue attachment force because of the less void in its figure.Part 3:Effect of loading opportunity on integration of the subperiosteal implants on hard palateObjective To evaluate the effect of loading opportunity on integration of the subperiosteal implants on hard palate.Methods Six pigs were divided into 3 groups,with 2 pigs in each group.A total of 24,four subperiosteal implants were fabricated on the hard palate of each pig.A downward of 9.8N force was applied on each implant at 4 weeks,8 weeks and 12 weeks respectively after implantation. The pigs were killed 4 weeks after the force application,and the integration of the implants was evaluated biomechanically using pull-out test,histologically by light microscope,scanning electron microscope and X-ray energy dispersive analysis. Results Twenty-one palatal subperiosteal implants were integrated with the surrounding tissue.The pull-out forces of the 3 groups of implants were 41.550(4.75)N,50.800(14.675)N and 52.800(17.65)N.Three patterns of integrations were observed in each group:fibrointegration with inflammation, fibrointegration and osseointegration,by which order the corresponding pull-out force increased.Conclusions After a healing period of 1 month,loading opportunity does not influence markedly on the result of integration of a palatal subperiosteal implant.The pattern of integration plays a key role in the strength of integration.Part 4:Construction of the three-dimensional finite element model of a defective edentulous cranial-maxillary complex rehabilitated by a palatal-subperiosteal-implant-supported obturatorObjective To construct a three-dimensional finite element model of a defective edentulous cranial-maxillary complex rehabilitated by a palatal-subperiosteal-implant-supported abturator.Method A primary 3D model of cranial-maxillary complex was created with Mimics software based on CT scanning data,and then was fitted the Non-Uniform Rational B-Splines surface with Geomagic software,by which the model of subperiolsteal implant was designed and constituted using Pro-E software.All the parts were modified and integrated into the definitive model with Ansys soft ware.Result A three-dimensional finite element model of a defective edentulous cranial-maxillary complex and an abturator supported by palatal subperiosteal implant,having tetrahedron 225,073 units and 76,682 nodes,was established. Conclusion the three-dimensional finite element model representing a complicated actual system like this study can be constructed satisfactorily with combination of the above software.Part 5:Analysis of three-dimensional finite element in the abutment design of the palatal subperiosteal implant in the rehabilitation of the unilateral edentulous maxillary defectObjective To optimize the abutment design of the palatal subperiosteal implant in the rehabilitation of the unilateral edentulous maxillary defect.Methods A three-dimensional finite element model of the rehabilitated right defective maxillae using palatal subperiosteal implant was constructed.Fifteen implants with from 2 to 6 abutments were designed.Bilateral loads on the denture of the obturator were simulated and the maximal von Mises stress values in the cortical bone of six sites of the left maxillae were investigated.The maximal dislocating forces applied on the left abutments of every implant were evaluated using a simplified model.Results The stress values usually increased with the decrease of abutments.There was no marked difference in bone stress value between 6-abutment and 5-abutment implants.Relatively lower stress values of implantⅣb,Ⅲa andⅡa were observed in the 4-abutment,3-abutment and 2-abutment implants respectively.No effect of the abutment number on the maximal dislocating force was found.The maximal dislocating forces on anterior abutments were higher than those on posterior abutments.Conclusion The model ofⅢa are more suitable in the rehabilitation of the unilateral defective edentulous maxillae.