Abstract
The interest in using titanium to fabricate removable partial denture (RPD) frameworks has increased, but there are few studies evaluating the effects of casting methods on clasp behavior.ObjectiveThis study compared the occurrence of porosities and the retentive force of commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) removable partial denture circumferential clasps cast by induction/centrifugation and plasma/vacuum-pressure.Material and Methods72 frameworks were cast from CP Ti (n=36) and Co-Cr alloy (n=36; control group). For each material, 18 frameworks were casted by electromagnetic induction and injected by centrifugation, whereas the other 18 were casted by plasma and injected by vacuum-pressure. For each casting method, three subgroups (n=6) were formed: 0.25 mm, 0.50 mm, and 0.75 mm undercuts. The specimens were radiographed and subjected to an insertion/removal test simulating 5 years of framework use. Data were analyzed by ANOVA and Tukey's to compare materials and cast methods (α=0.05).ResultsThree of 18 specimens of the induction/centrifugation group and 9 of 18 specimens of plasma/vacuum-pressure cast presented porosities, but only 1 and 7 specimens, respectively, were rejected for simulation test. For Co-Cr alloy, no defects were found. Comparing the casting methods, statistically significant differences (p<0.05) were observed only for the Co-Cr alloy with 0.25 mm and 0.50 mm undercuts. Significant differences were found for the 0.25 mm and 0.75 mm undercuts dependent on the material used. For the 0.50 mm undercut, significant differences were found when the materials were induction casted.ConclusionAlthough both casting methods produced satisfactory CP Ti RPD frameworks, the occurrence of porosities was greater in the plasma/vacuum-pressure than in the induction/centrifugation method, the latter resulting in higher clasp rigidity, generating higher retention force values.
Highlights
Over the past decade, studies have reported the advantages of commercially pure titanium (CP Ti) and its alloys, and have investigated the possibility of its use in the fabrication of removable partial denture (RPD) metal frameworks[2,13,15,16,20].Characteristics like low density, high melting temperature and reactivity at high temperatures DUH IDFWRUV WKDW LQFUHDVH GLI¿FXOWLHV LQ WKH &3 7L casting process, limiting its use . 8,10,14,17,18,22 Despite new casting machines for CP Ti, some technological problems, such as porosity and LQDGHTXDWH PROG ¿OOLQJ UHPDLQV5-7,9.Because of metal low density, porosities can EH LGHQWL¿HG LQ &3 7L E\ FRQYHQWLRQDO UDGLRJUDSKLFJ Appl Oral Sci. 487 2010;18(5):[487-92]imaging, permitting to control framework quality[4,21]
The present study investigated the hypothesis that the casting method (1- electric arc plasma in a vacuum and argon-inert atmosphere with injection of the metal/alloy into the mold by vacuum pressure; and 2- induction in a vacuum and argoninert atmosphere with injection by centrifugation) GRHV QRW LQÀXHQFH WKH RFFXUUHQFH RI SRURVLWLHV DQG the retentive force of titanium clasps to be used in RPD frameworks
Comparison between the cast methods by Tukey’s post-hoc test revealed that Co-Cr alloy VSHFLPHQV SUHVHQWHG VLJQL¿FDQW GLIIHUHQFHV (p
Summary
Studies have reported the advantages of commercially pure titanium (CP Ti) and its alloys, and have investigated the possibility of its use in the fabrication of removable partial denture (RPD) metal frameworks[2,13,15,16,20].Characteristics like low density, high melting temperature and reactivity at high temperatures DUH IDFWRUV WKDW LQFUHDVH GLI¿FXOWLHV LQ WKH &3 7L casting process, limiting its use . 8,10,14,17,18,22 Despite new casting machines for CP Ti, some technological problems, such as porosity and LQDGHTXDWH PROG ¿OOLQJ UHPDLQV5-7,9.Because of metal low density, porosities can EH LGHQWL¿HG LQ &3 7L E\ FRQYHQWLRQDO UDGLRJUDSKLFJ Appl Oral Sci. 487 2010;18(5):[487-92]imaging, permitting to control framework quality[4,21]. Studies have reported the advantages of commercially pure titanium (CP Ti) and its alloys, and have investigated the possibility of its use in the fabrication of removable partial denture (RPD) metal frameworks[2,13,15,16,20]. Characteristics like low density, high melting temperature and reactivity at high temperatures DUH IDFWRUV WKDW LQFUHDVH GLI¿FXOWLHV LQ WKH &3 7L casting process, limiting its use . This control is extremely important, since voids and pores may affect fatigue resistance of RPD frameworks subjected to repeated load cycles during chewing and to frequent insertion and removal. There are few studies about the different CP Ti casting methods[7,17]. The correlation between casting methods and RPD mechanical properties is yet to be studied
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