Machha Sujesh, Kumar M Vasanth, Rangarajan V
Department of Prosthodontics, Mamata Dental College and Hospitals, Khammam, Andhra Pradesh, India.
Indian J Dent Res. 2011 Jul-Aug;22(4):614. doi: 10.4103/0970-9290.90326.
Alloys have been considered to be of paramount importance in the field of prosthodontics. Long span prosthesis may often require joining of one or more individual castings to obtain better fit, occlusal harmony and esthetics in comparison to one-piece casting.
This study was undertaken to evaluate the mechanical properties of base metal alloys joined by two different techniques, namely, gas oxygen torch soldering and laser fusion, compared to a one-piece casting. Mechanical properties evaluated were tensile strength, percentage of elongation and hardness of the solder joint. In addition, corrosion properties and scanning electron microscopic appearance of the joints were also evaluated.
The samples were prepared according to American Society for Testing Materials specifications (ASTM, E8). Specimens were made with self-cure acrylic and then invested in phosphate-bonded investment material. Casting was done in induction casting machine. Thirty specimens were thus prepared for each group and compared with 30 specimens of the one-piece casting group.
SPSS software (version 10.0, Chicago, IL, USA) was used for statistical analysis. ANOVA and Benferroni post hoc tests were done for multiple comparisons between the groups and within the groups for mean difference and standard error.
Results showed that tensile strength of the one-piece casting was higher than laser fused and gas oxygen torch soldered joints. Laser fused joints exhibited higher hardness values compared to that of gas oxygen torch soldered joints. Scanning electron microscopic examination revealed greater porosity in the gas oxygen torch soldered joints. This contributed to the reduction in the strength of the joint. Gas oxygen torch soldered joints showed less corrosion resistance when compared to laser fused joints and one-piece casting.
Laser fusion, which is a recent introduction to the field of prosthodontics, produces joints which have properties between those of one-piece casting and the gas oxygen torch soldering.
合金在口腔修复学领域一直被认为至关重要。与整体铸造相比，长跨度修复体通常需要连接一个或多个单独铸件，以获得更好的贴合度、咬合协调性和美观性。
本研究旨在评估通过两种不同技术（即气体氧气焊炬焊接和激光熔合）连接的贱金属合金与整体铸造相比的机械性能。评估的机械性能包括焊点的拉伸强度、伸长率百分比和硬度。此外，还评估了接头的腐蚀性能和扫描电子显微镜外观。
样品根据美国材料与试验协会规范（ASTM，E8）制备。用自凝丙烯酸树脂制作标本，然后用磷酸盐粘结包埋材料包埋。在感应铸造机中进行铸造。每组制备30个标本，并与整体铸造组的30个标本进行比较。
使用SPSS软件（版本10.0，美国伊利诺伊州芝加哥）进行统计分析。进行方差分析和Bonferroni事后检验，以对组间和组内的均值差异和标准误差进行多重比较。
结果表明，整体铸造的拉伸强度高于激光熔合和气体氧气焊炬焊接的接头。与气体氧气焊炬焊接的接头相比，激光熔合的接头表现出更高的硬度值。扫描电子显微镜检查显示，气体氧气焊炬焊接的接头孔隙率更大。这导致接头强度降低。与激光熔合接头和整体铸造相比，气体氧气焊炬焊接的接头耐腐蚀性较差。
激光熔合是口腔修复学领域最近引入的技术，其产生的接头性能介于整体铸造和气体氧气焊炬焊接之间。
