- Email: [email protected]
OR 7 Corrosion in stainless steel and nickel titanium files
Vol. 23, No. 4, April 1997
O7~
Corrosion in Stainless Steel and Nickel Titanium Files O.W. STOKES*, P.M. DIFIORE, J.T. BARSS,
J.L.GILBERT and E.P. LAUTENSCHLAGEK Northwestern University Dental School, Chicago IL It has been observed in previom studies that ~ m e endodomic fileso f a similar type aad ~ c r tead to corrode while others do not. Occurrence of corrosion may be earned by differences in the structure of the metal alloy and/or diffmmcei in the mmmfactming process. The purpose of this study was to evaluate the corrosion susceptibility 8rid consisteatcy of five different endodontic files. For each, Kerr K-Flex,Caulk Flex-OFiles,Union Broach Flex-R-Film (stainless steel), plug Union Broach NiTi Files and Tulsa Profile NiTi Files, the cuttin8 flutes of twenty-four ISO size 20 files were immersed into 5.25% NaOCI; and their open circuit potemial (OCP) was recorded for one hour on a strip chart. The OCP was ~ with a high
impedance voltmeter and a standard calomel electrode (SCE) referenoe. It was discovered that those files which corroded were readily detected by this method since they exhibited unstable
OCP's with many, large, irrati¢ jumps of several hundred millivolts during the one hour monitoring. On the other hand, non-corroding ties rose to a plateau level of sevtn'al hundred millivolts and stabily remained there. The frequencies of corrosion were detected as follows: K-Flex(2/24), ~exO(10/24), Flex-R(2/2A), UBNiTi(2/24) and Tulm NiTi(2/24). Obviously, alltypes ~ o w e d some corrosion and both corroding and non-corroding files within the same package. These results deanomtrated that Flex-O-Fd~ exhibited the most f r m u m t corrosion for these oarticular test conditions: and that corrosion
susceotibilitv can be easily and oulcldv detected with OCP.
O~9 R
Effect of sterilization on cyclic fatigue of NiTi instruments. Mize SB% Clement DJ, Carues DL, Pruett JP. University of Texas Health Science Center, San Antonio. Phase changes in Ni-Ti alloy induced by heat treatment may return the alloy to its original, unstressed state. The purpose of this study was to determine if sterilization would extend the life expectancy ef rotary NbTi instruments. Root canals were simulated by stainless steel guide tubes with radii of curvature of 2ram and gram. A dynamometer applied a load ef I0 gm-cm to instruments while cycled to failure at 300 rpm using an electrical handpiece. Instruments were cycled to failure(100%), or to 75%, 50% or 25% of failure. Half of the partially cycled instruments were autoclaved, then all instruments were cycled to failure. Partially cycled instruments in 5ram canals fractured as predicted, while instruments in 2mm canals fractured at values less than predicted. 95% confidence intervals determined by muiticomparlson analysis (ANOVA) using Tukey's procedure post hoe indicated that there were no significant differences between groups when partially cycled at the same radius. Therefore. stcrillz0ti0n 9f NiTi instruments did not enhance oerformauee re2ardle_.. of radius of curvature, This stu4y shows that stedliTln~Ni-Ti in~(ruments between uses h~O no effect on nrolonslnE their clinical life exnectancv or alterJn2 cvcl;~ fatJEue characteristics. This research was supported by an Endodontic Resident Grant (SBM) from the AAE.
Journal of Endodonticu 4p 251 In Vitro Biacomlmtihility Analysis of Boron-Implanted Nickel-Titanium..I.Ngnyen*, T. Serene anti G. T.-J. Huang (UCI,A School of Dentistry, Los Angeles, California, USA) Boron-imphmted nickel-titanium (NiTJ) that has a 0.2 micron thick layer of heron added to the NiTi surface has shown to increase the surface hardness by twu-fnld (Lee et ul., J. Endodnn., 1996). This device appears to he useful to improve the cutting efficiency of nickel-titanium (NiTi) enilodontic files. To assure the biocompatibJlity of this modified NiTi instrument, in case separation occurred heyond the root caual system into the periapical tissue, we aimed to evaluate the cytotoxicity of this new endodontic instrmnent. Primary culture of human pulpal fihroblasts were obt,lined frmn feeshly extracted, soft-tissue impacted, caries-free third molars. Boron-implanted NiTi, stainless steel, titanium, nickel-titanium and nickel metal rods were cocultured with huntan pulpal fihrohlasts at 80% suhconlluency. The nickel was used as a positive control for its known cytotoxicity in ctllttn'e. At different time I)oints, cell vi.'d)ility was measured with trypan-blue dye exclusion tests. The results showed tlr4t, at 8, 24, and 48 h, the viahility of cells incubated with Imron-Jmplanted metal had na signific:|nt difference fl'Onl those incuhated with st:ll;dess steel, titanium, or nickel-titanlum metals. Nickel
showed significant ¢liffe1"ellCe in cytotoxicity from cells alone Ineg;ilJve control) mid cells with other metals at all time intervals. At dill"ercnt time points, ceil viahility was me:isu,'ed with trYl)an-hlue dye exclusion tests. At 72 h, the control cells alone exhihited less than 85% of cell viahility, therefl~re no comparison was made after 48 h time point. The t-test (p ;it 0.05 loved was used to statistically compare all experimental groups. W~..t;on¢lude th~at boron-imphmled NiTi endodonlic files have it similar tissue Compatibility to olhee currently used e n d o d o n t i ¢ instrttmenls. Thus. I)oron-imnhmted NiTi files may b~ ~1 valuahle ¢lidodonljc insll'ulnenl based on imnruved calliper elliciency and Ifiocompalil~ilily.. This study was supported in I m r l hy Ihe American AssocJ:dion of Enflodonlists
Foundation, (;r-re]el:tieStndelll Awar(I.
%
SEM Study of Different Irrigating Solutions on Dentinal Walls after NiTi Rotary Instrumentation. B. Karabucak*, R.Wong, Claire Pypen, Robert Weber, S. Kim (U. of Pennsylvania, SDM, Philadelphia) ( U. of Vienna Dent Sell Vienna, Austria). Chemical debridernent of the root canal system with Sodium Hypoehlorite (NaOCI) and Ethylenediarninetetraacetic acid (EDTA) has been shown to be highly effective in removing the smear layer and opening dentmal tubules after thorough debridernent of the root canal system. However, studies never introduced the use of Nickel Titanium (NiTi) rotary instrumentation for these cleaning and shaping procedures. Therefore, the purpose of our study was to compare the use of EDTA and NaOCI on the dentinal surface of the root canal system after thorough cleaning and shaping with NiTi rotary instrumentation. Forty mandibular molars were selected with straight canals. Thirty teeth were instrumented with Profiles and Quantec rotary instruments while 10 teeth were instrumented with hand K files. Each canal was flushed with 5cc of 5.25% NaOC1 after every file and ultimately dried prior to final flushing procedures. Upon completion of instnnnentationto a size 27.9 (Profile #5) or ISO 30 by hand, the teeth were separated into four groups. Group I hand instrumentation with NaOCl, Group It rotary with NaOC1, Group HI rotmy with 10co flush 15% EDTA followed by 10cc flush 5.25% NaOCI, Group IV rotary with 5on flush 15% EDTA and a five minute soaking period followed by a 10cc flush of 5.25% NaOCl. All teeth were then sectioned and examined under SEM. The results showed that rotary instrumentation (Gr II) when compared with hand instrumentation (Gr I) showed a marked increase in dentinal debris Group IV when compared with Croup 1, II, or IiI had the best overall debris removal and most open tubules (13<0.01, Fisher). Thus it appears that irrigating with 15% EDTA for five minutes followed by a 10cc flush..of 5.25% NaOCl are ..most effective for debris removal and opening dentmal tubules after cleaning and shaping procedures with rotary insmbm_ents.
O7~
Corrosion in Stainless Steel and Nickel Titanium Files O.W. STOKES*, P.M. DIFIORE, J.T. BARSS,
J.L.GILBERT and E.P. LAUTENSCHLAGEK Northwestern University Dental School, Chicago IL It has been observed in previom studies that ~ m e endodomic fileso f a similar type aad ~ c r tead to corrode while others do not. Occurrence of corrosion may be earned by differences in the structure of the metal alloy and/or diffmmcei in the mmmfactming process. The purpose of this study was to evaluate the corrosion susceptibility 8rid consisteatcy of five different endodontic files. For each, Kerr K-Flex,Caulk Flex-OFiles,Union Broach Flex-R-Film (stainless steel), plug Union Broach NiTi Files and Tulsa Profile NiTi Files, the cuttin8 flutes of twenty-four ISO size 20 files were immersed into 5.25% NaOCI; and their open circuit potemial (OCP) was recorded for one hour on a strip chart. The OCP was ~ with a high
impedance voltmeter and a standard calomel electrode (SCE) referenoe. It was discovered that those files which corroded were readily detected by this method since they exhibited unstable
OCP's with many, large, irrati¢ jumps of several hundred millivolts during the one hour monitoring. On the other hand, non-corroding ties rose to a plateau level of sevtn'al hundred millivolts and stabily remained there. The frequencies of corrosion were detected as follows: K-Flex(2/24), ~exO(10/24), Flex-R(2/2A), UBNiTi(2/24) and Tulm NiTi(2/24). Obviously, alltypes ~ o w e d some corrosion and both corroding and non-corroding files within the same package. These results deanomtrated that Flex-O-Fd~ exhibited the most f r m u m t corrosion for these oarticular test conditions: and that corrosion
susceotibilitv can be easily and oulcldv detected with OCP.
O~9 R
Effect of sterilization on cyclic fatigue of NiTi instruments. Mize SB% Clement DJ, Carues DL, Pruett JP. University of Texas Health Science Center, San Antonio. Phase changes in Ni-Ti alloy induced by heat treatment may return the alloy to its original, unstressed state. The purpose of this study was to determine if sterilization would extend the life expectancy ef rotary NbTi instruments. Root canals were simulated by stainless steel guide tubes with radii of curvature of 2ram and gram. A dynamometer applied a load ef I0 gm-cm to instruments while cycled to failure at 300 rpm using an electrical handpiece. Instruments were cycled to failure(100%), or to 75%, 50% or 25% of failure. Half of the partially cycled instruments were autoclaved, then all instruments were cycled to failure. Partially cycled instruments in 5ram canals fractured as predicted, while instruments in 2mm canals fractured at values less than predicted. 95% confidence intervals determined by muiticomparlson analysis (ANOVA) using Tukey's procedure post hoe indicated that there were no significant differences between groups when partially cycled at the same radius. Therefore. stcrillz0ti0n 9f NiTi instruments did not enhance oerformauee re2ardle_.. of radius of curvature, This stu4y shows that stedliTln~Ni-Ti in~(ruments between uses h~O no effect on nrolonslnE their clinical life exnectancv or alterJn2 cvcl;~ fatJEue characteristics. This research was supported by an Endodontic Resident Grant (SBM) from the AAE.
Journal of Endodonticu 4p 251 In Vitro Biacomlmtihility Analysis of Boron-Implanted Nickel-Titanium..I.Ngnyen*, T. Serene anti G. T.-J. Huang (UCI,A School of Dentistry, Los Angeles, California, USA) Boron-imphmted nickel-titanium (NiTJ) that has a 0.2 micron thick layer of heron added to the NiTi surface has shown to increase the surface hardness by twu-fnld (Lee et ul., J. Endodnn., 1996). This device appears to he useful to improve the cutting efficiency of nickel-titanium (NiTi) enilodontic files. To assure the biocompatibJlity of this modified NiTi instrument, in case separation occurred heyond the root caual system into the periapical tissue, we aimed to evaluate the cytotoxicity of this new endodontic instrmnent. Primary culture of human pulpal fihroblasts were obt,lined frmn feeshly extracted, soft-tissue impacted, caries-free third molars. Boron-implanted NiTi, stainless steel, titanium, nickel-titanium and nickel metal rods were cocultured with huntan pulpal fihrohlasts at 80% suhconlluency. The nickel was used as a positive control for its known cytotoxicity in ctllttn'e. At different time I)oints, cell vi.'d)ility was measured with trypan-blue dye exclusion tests. The results showed tlr4t, at 8, 24, and 48 h, the viahility of cells incubated with Imron-Jmplanted metal had na signific:|nt difference fl'Onl those incuhated with st:ll;dess steel, titanium, or nickel-titanlum metals. Nickel
showed significant ¢liffe1"ellCe in cytotoxicity from cells alone Ineg;ilJve control) mid cells with other metals at all time intervals. At dill"ercnt time points, ceil viahility was me:isu,'ed with trYl)an-hlue dye exclusion tests. At 72 h, the control cells alone exhihited less than 85% of cell viahility, therefl~re no comparison was made after 48 h time point. The t-test (p ;it 0.05 loved was used to statistically compare all experimental groups. W~..t;on¢lude th~at boron-imphmled NiTi endodonlic files have it similar tissue Compatibility to olhee currently used e n d o d o n t i ¢ instrttmenls. Thus. I)oron-imnhmted NiTi files may b~ ~1 valuahle ¢lidodonljc insll'ulnenl based on imnruved calliper elliciency and Ifiocompalil~ilily.. This study was supported in I m r l hy Ihe American AssocJ:dion of Enflodonlists
Foundation, (;r-re]el:tieStndelll Awar(I.
%
SEM Study of Different Irrigating Solutions on Dentinal Walls after NiTi Rotary Instrumentation. B. Karabucak*, R.Wong, Claire Pypen, Robert Weber, S. Kim (U. of Pennsylvania, SDM, Philadelphia) ( U. of Vienna Dent Sell Vienna, Austria). Chemical debridernent of the root canal system with Sodium Hypoehlorite (NaOCI) and Ethylenediarninetetraacetic acid (EDTA) has been shown to be highly effective in removing the smear layer and opening dentmal tubules after thorough debridernent of the root canal system. However, studies never introduced the use of Nickel Titanium (NiTi) rotary instrumentation for these cleaning and shaping procedures. Therefore, the purpose of our study was to compare the use of EDTA and NaOCI on the dentinal surface of the root canal system after thorough cleaning and shaping with NiTi rotary instrumentation. Forty mandibular molars were selected with straight canals. Thirty teeth were instrumented with Profiles and Quantec rotary instruments while 10 teeth were instrumented with hand K files. Each canal was flushed with 5cc of 5.25% NaOC1 after every file and ultimately dried prior to final flushing procedures. Upon completion of instnnnentationto a size 27.9 (Profile #5) or ISO 30 by hand, the teeth were separated into four groups. Group I hand instrumentation with NaOCl, Group It rotary with NaOC1, Group HI rotmy with 10co flush 15% EDTA followed by 10cc flush 5.25% NaOCI, Group IV rotary with 5on flush 15% EDTA and a five minute soaking period followed by a 10cc flush of 5.25% NaOCl. All teeth were then sectioned and examined under SEM. The results showed that rotary instrumentation (Gr II) when compared with hand instrumentation (Gr I) showed a marked increase in dentinal debris Group IV when compared with Croup 1, II, or IiI had the best overall debris removal and most open tubules (13<0.01, Fisher). Thus it appears that irrigating with 15% EDTA for five minutes followed by a 10cc flush..of 5.25% NaOCl are ..most effective for debris removal and opening dentmal tubules after cleaning and shaping procedures with rotary insmbm_ents.