The Research Of Welding Condition In Bar Attachment Applied To Implant-supported Overdenture By Pulsed Nd:YAG Laser

Along with technological development, an increasing number of edentulous patients opted for Implant - supported overdenture which retained with bar-clip attachment or magnetic. Through this method successfully solved the problem of denture retention and improved the quality of life of patients. However, most of bar-clip attachment in overdentures supported by implants previous were the Casting the whole of linkages by Titanium and Co-Cr alloy .There are inadequate in the precision and contraction. But the dental laser welding technology made up for this drawback . The dental laser welding technology for the production of bar-clip attachment obtained satisfactory results, but also appeared welding surface fracture in the clinical application . At present, there are not special study on the laser welding of bar-clip attachment in Implant - supported overdenture . Yamagishi, Chai, Liu have done research in laser welding of titanium, but its use of experimental materials are casting titanium and less than 2 mm thickness. In addition, Each person's findings are different . The purpose of this study is to evaluate the mechanical properties of laser-welded titanium frameworks applied to implant-supported overdenture under different laser welding conditions and using AutoCAD workstation carry out expert analysis of fracture surface on laser-welded samples to find the optimal welding parametersSubject objectives:The first part of the study through simulation ITI implant system leveraged attachment specifications in accordance with the four different Nd: YAG laser welding of titanium welding production of 30 specimens, as well as evaluation of mechanical properties through the scanning electron microscope, and exploring welding parameters on the welding surface mechanical properties of the impact of clinical application seeking to meet the production requirements of the welding parameters on this basis. On the partⅡ, using the same welding parameters on the two groups of different welding rod shape titanium ring interface specimens were 18, through mechanical performance evaluation, scanning electron microscopy. There was no statistically significant difference on the interface bar attachment welding rod surface mechanical properties. The third part of the study, we will examine the image of welding recorded in the first and second part of the scanning electron microscope; after converting into AutoCAD graphics workstations; calculating of welding and welding of weld depth exactly, and Seeking the impact of welding depth and welding area about welding parameters and the shape of the interface-lap . Methods and Results:Part I: Simulating bar attachment in ITI system, the CNC machine tool will cut a piece TA2 titanium plate into 40 mm×3 mm×2 mm titanium rod. After polishing, the rods were randomly divided into five groups, including four groups for the experimental group (A,B,C,D group), one group for the control group, each of the six samples. Welding specimen were cleaning in acetone for 15 min , and then distilled for 10 min in ultrasonic cleaning, then will be welded after drying, seamless gripping coaxial-based experiments in a special fixture. With fixed screws locking ; DESKTOP dental laser welding machine welded production specimen using four different welding parameters. welding overlap each group were all 2 / 3, single-pulse, double-sided welding. All welding operations are the same mechanics operation.After the specimen production, and through the eye observation and mechanical properties testing, scanning electron microscopy observed each weld fracture, recorded scanned images, and compared with the control group. SPSS 13.0 statistical software for statistical analysis.The results showed that:(1)Groups showed the silver-white weld, smooth surface without coloring, no crack, weld district sag slightly.(2)The test group specimen fracture sites are in the welding area, the control group Parent metal fracture sites are in the central part. Elongation rate of the experimental group are lower than the Parent metal group, we can see that the welding brittle increased significantly. A group of welding exists significant difference Parent and B, C, D experimental group on the tensile strength (P <0.05); there were no significant differences between B, C, D experimental groups and Parent metal on the tensile strength ( P> 0.05). Mechanical properties of the control group results Conforms to the GB/713810-1997 national standards, achieves the clinical use standard.(3) In low scanning electron microscopy ,observed each group were not completely fracture permeability welding, welding area assumes the circle shape and no found apparent porosity defects such as Blowhole , Welds the region edge to assume the wave shape, no necking phenomenon. In the high-power microscope welding honeycomb structure is shallow compared with the control group, the pilot group not significantly different.Experimental results showed that when the laser welding machine voltage between 305 to 330 v, pulse width of 10 ms or 12 ms, spot diameter of 1 mm, laser welding rod attachment close to Parent metal meet on the tensile strength, achieving the clinical use standard.Part II: Simulating bar attachment in ITI system, processing 6 mm×4mm×1mm titanium ring and use same rod in the first experiments batch of 40 mm×3mm×2mm,;a total of 18 were divided into two groups, The experimental group connection is the arc surface, curved surface for the control group ; Welding specimen were cleaning in acetone for 15 min , and then distilled for 10 min in ultrasonic cleaning, then will be welded after drying, seamless gripping coaxial-based experiments in a special fixture. Vernier caliper measured control group-circle clearance and recorded. DESKTOP dental laser welding machine welded production specimen using the same welding parameters (the same with the parameters established by the first part). Welding overlap each group were all 2 / 3, single-pulse, double-sided welding. All welding operations are the same mechanics operation.After the specimen production, and through the eye observation and mechanical properties testing, scanning electron microscopy observed each weld fracture, recorded scanned images, and compared with the control group. SPSS 13.0 statistical software for statistical analysis.The results showed that:(1) Face-gap welding interface specimens were less than 0.5 mm(2)Groups showed the silver-white weld, smooth surface without coloring, no crack, weld district sag slightly(3)The mechanical properties test results: two groups fracture site are in the welding, there are no significant difference on elongation, tensile strength (P> 0.05).(4)In low scanning electron microscopy ,observed each group were not completely fracture permeability welding, welding area assumes the circle shape and no found apparent porosity defects such as Blowhole , Welds the region edge to assume the wave shape, no necking phenomenon. In the high-power microscope welding honeycomb structure is shallow compared with the control group, the pilot group not significantly different.The experimental results show that: When welding interval less then 0.5 mm and with the same welding parameters (meet welding parameters: voltage between 305 to 330 v, pulse width of 10 ms or 12 ms, spot diameter of 1 mm), two different interfaces-lap Forms are no significant impact on the welding surface mechanical properties.Part III: images recorded by scanning electron microscopy in the Part I and part II ; first using CorelDRAW software gathering picture edge graph, then inducted the AutoCAD workstations, Surveyed each face of weld the greatest depth and the welding area, and Computation mean value. SPSS 13.0 statistical software for statistical analysis. The results showed that: (1) In Part I , group A in the experimental exist significant difference on the mechanical properties with other experimental group. It also were significant difference with other experimental group in the experimental on the maximum depth of welding and welding area (P <0.05), and other experimental groups has not seen significant statistics difference (P> 0.05).(2) In Part II , there is no significant difference between the experimental group and control group on the greatest depth and welding area mean (P> 0.05).(3) Tensile load, welding area and welding depth of the relations curves in Part I, show that the depth of welding and welding area exists approximate ratio, the relationship with the welding parameters, welding area and tensile strength is a positive correlation . In Part II, tensile load, welding and welding depth of the relations curve in the same welding parameters; welding area and welding depth has always maintained approximate ratio. Under two different Connections, there was no significant effect occurred on welding depth and welding area in two group.Conclusion:(1) when the Nd:YAG laser welding machine voltage between 305 to 330 v, pulse width of 10 ms or 12 ms, spot diameter of 1 mm, laser welding rod attachment close to Parent metal meet on the tensile strength, achieving the clinical use standard.(2)When welding interval less then 0.5 mm and with the same welding parameters (meet welding parameters: voltage between 305 to 330 v, pulse width of 10 ms or 12 ms, spot diameter of 1 mm), two different interfaces-lap Forms are no significant impact on the welding surface mechanical properties(3)The welding depth and the welding area existence approximate proportional relationship, this relations change along with the welding parameter; Between the welding depth, the welding area and the Tensile strength have the correlational dependence.(4)To the attachment leveraged laser welding, the incomplete welding does not affect normal application.