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<p><b>OBJECTIVE</b>The objective of this study was to investigate the tarnish induced by Streptococcus sobrinus serotype g on Co-Cr, Ni-Cr and casting titanium alloys.</p><p><b>METHODS</b>Co-Cr, Ni-Co and casting titanium alloys were respectively machined into a size of 10 mm x 10 mm x 1 mm in tablets, and totally 90 specimens with 30 of each were prepared for the test. The 30 specimens of each alloy were randomly and equally divided into three subgroups, including the blank control group, the media control group and the inoculated media group. Under the aerobic condition, the surfaces of the sucrose agar media were inoculated with Streptococcus sobrinus serotype g. The labeled sterile specimens were placed on the surface of the media for 10 weeks. The specimens were changed to a new sucrose media with bacteria each week. The specimens were removed after 10 weeks of incubation, immersed in 0.05% glutaraldehyde solution to eliminate AaY4, rinsed with distilled water. After 2 weeks, the specimens were removed and observed visually or examined by MINOLTA CR-100 color apparatus.</p><p><b>RESULTS</b>Compared with the blank control, the control media without bacteria did not influence the alloy specimens (P > 0.05). Streptococcus sobrinus serotype g caused tarnish on specimens. There was significant difference between the control media group and the blank control group with inoculated media group on all the specimens (P < 0.05).</p><p><b>CONCLUSION</b>Streptococcus sobrinus serotype g affects the color of Co-Cr, Ni-Cr and casting titanium alloys, but the color does not change from yellow-green range to red-yellow range.</p>
Subject(s)
Chromium Alloys , Chemistry , Cobalt , Chemistry , Color , Dental Alloys , Chemistry , Dental Casting Technique , Dental Clasps , Dental Stress Analysis , Denture Design , Denture Retention , Denture, Partial, Removable , Materials Testing , Nickel , Chemistry , Streptococcus sobrinus , Classification , Physiology , Surface Properties , Tensile Strength , Titanium , ChemistryABSTRACT
<p><b>OBJECTIVE</b>To study the precise stress distribution of the apical foramen area of endodontic endosseous implant, in order to improve the prosthetics of endodontic endosseous implant.</p><p><b>METHODS</b>After analysis of the two-dimensional endodontic endosseous implants model with finite element method, left and right areas beside the apical foramen were selected as infinite domains to calculate. D-N interactive method was used to connect the finite and infinite domains.</p><p><b>RESULTS</b>Under 45 degrees axial right oblique loading, the stress concentration occurred in both infinite domains of the apical foramen. The infinite domain nearing the load side was tension stress concentration, but the other side was compressive stress concentration. Two stress concentration points were just at the central points, which were intersections between implant and dentin. The stress reduced in all directions from these two stress concentration points, but in the ligament, the result was contrary.</p><p><b>CONCLUSIONS</b>The change of the tooth rotational center is helpful to the tooth stability and carrying capacity after restoration. In the implant area, the diameter of implant at the apical foramen of root shall not be reduced to protect root in clinical work. It is very important to preserve the tissue of periodontal ligament for endodontic endosseous implants.</p>
Subject(s)
Humans , Dental Implantation, Endosseous , Models, Dental , Dental Stress Analysis , MethodsABSTRACT
Objective: To study the implant-bone interface remodelin g after loading of submerged and nonsubmerged implant denture.Methods: 8 adult beagle dogs were used to build the animal model. Submerged and nons ubmerged implants were implanted into the bilateral mandible. Fixed metal full c rown was used to carry out the submerged and nonsubmerged implant denture. The b eagle dogs were sacrificed by steps after loading of the dentures. HE staining t echnique was used to observe the dynamic remodeling process of implant-bone int erface.Results:2 weeks after loading of implant denture, a major ity of the implant surface attached to bone tissue directly, however, at the int erface, especially at the top of the screw thread, bone tissues were absorbed an d substituted by fibrous tissues. 4 weeks after loading, fine attachment was fou nd at the implant-bone interface and the previouly observed fibrous tissue at t he interface was gradually remodeled to form new bone. 8 weeks after loading, i mplant directly attached to bone tissues by osteo-interface, and the cellular c omponents and capillaries were decreased at the interface.12 weeks after loading , all implants attached to bone tissues by osteo-interface with high combinatio n level, typical Havers system was observed at the interface.No obvious differen ce in the interface remodeling was observed between the submerged and nonsubmerg ed implant denture. Conclusion:There is no distinct difference i n the implant-bone interface remodeling after the loading of submerged and nons ubmerged implant denture.
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砄bjective: To establish two dimensional infinite model for endodontic endosseous implants in order to set up infinite element method and study the stress distribution of the apical foramen area of endodontic endosseous implant. Methods: Based on the analysis of two dimensional endodontic endosseous implants model with finite element method, left and right areas beside the apical foramen were selected as infinite domains including implant dentin and ligament sections. D N interactive method was used to connect the finite and infinite domains. Results: After ten times interaction between finite and infinite domains with D N interactive method, the outcome approached to a stable numerical value close to the displacement of both domains. Conclusion: The infinite model of two dimensional endodontic endosseous implants established by D N interactive method is efficient and accurate.
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Objective: To establish a Beagle dog model for the study of the mechanism of implant-bone interface remodeling following the restoration of submerged and nonsubmerged implant denture. Methods: 8 adult purebred beagle dogs were used to build the animal model. Fixed metal full crown was used to carry out submerged and nonsubmerged implant denture in the dogs to mimic the normal chewing status in animal models. Results: The submerged and nonsubmerged implant dentures were made successfully. After the implant denture restoration, all experimental dogs were fed with granular horniness forage to guarantee enough biting stimulation. The chewing fashion of experimental dogs was not changed obviously during the experiment process. Although the horniness forage may result in fairly bigger bite force, no visble biting hurt was found 12 weeks after loading and the fixed implant dentures were all preserved. Conclusion: The beagle dog model can preferably mimic the normal chewing fashion and the models are both availability and credibility.
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0.05). The standard deviation of the distance of 6 to 6 in the water/powder ratio of 33∶10 was extraordinary big(s=0.206).②The time of pouring generated dimensional shrink(P
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Objective: To study the precise stress distribution in the apical foramen area of endodontic endosseous implant. Methods:After analysis of the two-dimensional endodontic endosseous implants model with finite element method, left and right areas beside the apical foramen were selected as infinite domains for calculation. Results:Under 45? axial right oblique loading, the stress concentration occurred in both infinite domains of the apical foramen. The tension stress concentrated in the infinite domain near the load side,but the other side was compress concentrated. Two stress concentration points were just at the central points, which were intersections between implant and dentin. In the implant and dentin section, the stress reduced in all directions from two stress concentration points, but in the ligament section, the result was contrary. Conclusion:It is helpful to keep the root stable when the fulcrum of the root changed to lower part after restoration. In the implant area,the diameter of implant at the apical foramen of root shouldn't be reduced for the protection of root in clinical work;It is very important to preserve the tissue of periodental ligament for endodontic endosseous implants.
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?Objective: To evaluate the mechanical properties of low noble alloy Au Pd and Ag Pd developed by Stomatological College,Fourth Millitaly Medical University and Xi'an University of Architecture & Techuology. Methods:The two low noble alloys were cast by means of a centrifugal induction furnace into the tensile bars whose dimensions accorded with the standards of China for Dental Casting Precious Metal Alloys. Tensile properties (?b)were determined by means of a conventional testing machine. The 0.2% offset yield strength(?0.2), elongation(?) and microhardness (HV)were determined in a conventional manner. All data were the average of four specimens of each alloy. Results:?b(MPa),?0.2(MPa),?(%) and HV of Au Pd were 485?12.9,365 ?14.8,7.8?1.1 and 220?14.3;those of Ag Pd 550?9.5,435?8.2,13.5?5.4 and 245?15.1,respectivey.Conclusion:The mechanical properties of the two low noble alloys meet the demands of standards and have lower microhardness than natural tooth enamel.
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砄bjective:To determine the effect of Arg Gly Asp(RGD) containing peptide on the expression of osteocalcin mRNA expression in mouse calvarial osteoblasts.Method:Titanium samples were coated with pure golden and then immersed into Arg Gly Asp Cys (RGDC) solution (2 mmol/L) for overnight.The materials coated with Arg Gly Asp Cys (RDGC) or without treatment were used as controls.Mouse calvarial osteoblasts were isolated and seeded on the surfaces and harvested in 10,15,and 21 d respectively.Osteocalcin mRNA was detected by Northernblot hybridization.Results:Osteocalcin expresion was found in the cells on RGDC coated surface on day 15,while that was found in the cells in other groups at same level on day 21.Conclusion: RGD peptide can promote the osteocalcin expression in mouse osteoblasts.
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Objective: To study the stress in bone implant interface, dentin and periodontal ligament while an endodontic endosseous implant is placed through a centeral incisor with periodontal compromises. Methods: Two dimension finite element analysis method was used and finite element analysis (FEA) model of the Chinese adult central incisor with II degree looseness according the data from literature was established. A load of 100 N was applied vertically or at 45?to vertical. The stress in bone implant interface, dentin and periodontal ligament was measured and analysed with Super sap(1991 edition) FEA software in a IBM PC(PIII 550).Results: The mobility of the tooth was decreased by endodontic endosseous implant with periodontal compromises, and lower stress was observed at the alveolar crest and periodontal membrane after implantation with inclined load. High stress concentration on the implant/bone interface was produced below the canal orifice and implant apex, and at root apex within dentin.Conclusion: Endodontic endosseous implant can be used to stabilize the tooth with periodontal compromises, and to improve the stress distribution around the root.
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objective: To generate 3 D model of teeth for finite element method(FEM) analysis by computer. Methods: On the basis of 3 D model created by 3D Max, the 3 D FEM model of teeth was generated by using of CAE software. Boundary condition was set in the part of teeth root with elastic constraint. The elastic modulus was chosen as the modulus of periodontium. Results: Generated right inciser model comprised of 25 386 units and 5 111 nodal points. Conclusion: 3 D FEM model of tooth can be generated by CAE software.
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Objective:To study the effects of adhesive peptide arginlie-glycine-aspartic acid(RGD) on the attachment and spreading of osteoblast on the surface of dental implant materials. Methods: RGDC peptides were covalently immobilized on the surface of dental implant materials by SAMs. Rat osteoblasts were isolated and cultured on the materials. The attachment and spreading behavior of the cells were analyzed by cell counting and FITC-conjugated immunofluorsescent assay. Results: On the RGD coated surface, cell attachment was increased by 50% (P
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Using eccentric wheel and spring, an instrument was developed in this study. Relative information of the instrument were clearly explained, including its structure and running principle. The instrument can be widely used in fatigue measurement of fixed prostheses and capability of resisting break, and provide the experimental gist of the using of prostheses.