ABSTRACT
Objective: To investigate the stress and stress distribution generated on each component of implant prosthodontic system and surrounding cortical bone when different diameters of screw-access hole (SAH) were prepared on molar crown. Methods: A fimite element(FE) model of partial mandible without first molar was set up, and an Bego implant was insert into it. A total of 5 models of the crown were computer-simulated by varying the diameter (Φ = 0-4 mm) of the SAH. The loading forces were 200 N axially (0°) and 100 N obliquely (45°) respectively on occlusive surface. The FE analysis was performed by computer. Results: Φ ≤3 mm: stress on occlusal surface of crown was almost unchanged and mainly distributed in the loading area. Φ = 4 mm, stress appeared an obvious rise and reached the maximum, the stress concentration under vertical load was changed to the hole margin. In vertical loading, screw could remain at a relatively low stress level when diameter did not exceed 1 mm. No changes on other components was observed. Conclusion: SAH diameter of 1 mm is recommended when a cement-and screw-retained crown is used in posterior region.
ABSTRACT
Objective:To study the influences of angled abutments connected with small diameter implants in anterior maxilla restora-tion.Methods:Simulation models of angled abutment with small diameter restoration in anterior maxilla were established,the biome-chanical properties of the models were studied by finite element method(FEM)analysis.Results:Following the increase of the abut-ment angle,the stress and strain of all parts increased linearly and more concentrated,while appropriate prosthetic crown could share some load.Cortical bone elastic deformation exceeded the threshold when the abutment angle was bigger than 8 °.Conclusion:With abutment angle increase,stresses and strains will increase and will be more concentrated,which is unfavorable for load conduction.Ap-propriate crown can reduce the adverse effects of angled abutment.Angled abutment should not be used for d 3.5 implant.
ABSTRACT
Objective To explore the effects of angled abutments on the anterior maxilla implant restoration. Methods We analyzed the biomechanical properties of implants of different sizes (Φ3.5 mm,4.0 mm and 4.5 mm in diameter;L11.5 mm and L13 mm in length)after connecting different angled abutments (0°,10°,20°,and 30°) using finite element method.Results The stresses and strains of loading parts of restorations increased and their distribution became more concentrated as the angle of abutment increased.Cortical bone of Φ3 .5 implants with smaller angle (10°or less)andΦ4.0 implants with abutments had the risk of overpassing the bone elastic threshold when the angle approached 30°.However,the cortical bone elastic deformation was within a safe range at all angles inΦ4.5 group.Conclusion We should consider the diameter of the implant when selecting angled abutments.The angled abutments are not suitable for small diameter implants.The bite force should be under control when needed. The larger angled abutments can be applied in the standard and major diameter implants and it is necessary to avoid occlusal overloading.
ABSTRACT
Objective:To measure the bioelectrical impedance around the dental implants with bone defects.Methods:Bilateral maxillar second premolar were extracted in 6 native mongrel dogs,implants were placed immediately with or without bone defect of corresponding alveolar bene.Impedance value(IV)between the implant and contralateral mouth corner was measured by LCR TEST-ER.IVs were compared and analyzed by SPSS.Results:IVs of bone defect group were bigger than that of control group(P <0.05), in largger defect group were smaller than that in smaller group(P <0.05).Conclusion:Bioelectrical impedance can be used as an evaluation of peri-implant bone defects and the size of bone defect.
ABSTRACT
Objective:To evaluate the clinical effect and safety of piezoelectric osteotomy in lateral sinus floor augmentation.Meth-ods:53 implants were placed in 30 sites after lateral sinus floor augmentation(LSFA)in 29 patients by piezoelectric osteotomy.47 implants were placed simultaneously with LSFA,6 were delayed.6-8 months after implantation,the final fixed prostheses were per-formed.The patients were followed-up at 3,6,and 12th months after restoration.Results:The mean residual bone height(RBH) was 4.46 mm before operation.The mean height of sinus elevation was 7.34 mm after operation.No membrane perforation occurred. Peri-implantitis,peri-implant mucositis and implant mobility were not found during follow-up.X-ray examination showed good os-seointegration in the interface between the implants and bones.The implant survival rate and the operation success rate were 100%. Conclusion:The application of piezosurgery is safe and reliable in lateral sinus floor augmentation.
ABSTRACT
Objective: To compare JGW with autogenous bone when used as grafting material in maxillary sinus floor augmentation.Methods: A study was conducted by performing a bilateral maxillary sinus floor augmentation with autogenous bone and JGW(Jin Gu Wei,Golden Bone,bone substitute,Shanghai Xiaobo Tec.) on rabbits.The process of bone formation was evaluated during different periods by imageology and histomorphology methods.Results: At 2nd week the gray scale of JGW was very lower than that of autogenous bone,but no significant difference was found at 12th week.The number of osteoblasts decreased with the time,no significant difference was found at 12th week.The degradation of JGW was relatively faster.Conclusion: JGW is feasible in maxillary sinus floor augmentation.