0099-2399/90/1605-0214/$02.00/0 JOURNAL OF ENDODONTICS Copyright 9 1990 by The Arnerican Association of Endodontists
Printed in U.S.A.
VOL. 16, No. 5, MAY 1990
A Comparison of Techniques for Cleaning Endodontic Files after Usage: A Quantitative Scanning Electron Microscopic Study Carlos Alberto Ferreira Murgel, CD, Richard E. Walton, DDS, MS, Barry Rittman, PhD, and Jesus Djalma Pecora, CD, MC
care and attention both for initial instrument preparation and for appropriate time of usage. However, the effectiveness of ultrasonic cleaning of used files has not been investigated. In the clinical situation endodontic files are generally cleaned at the conclusion of the appointment or even at the end of the day. This delay may decrease the efficacy of removal once the debris has dried, although this delay factor has not been tested. The objective of this study was to quantitate and compare debris remaining on endodontic files after one of three techniques of cleaning: (a) sponge soaked with alcohol, (b) gauze soaked with alcohol, or (c) ultrasonic bath. Also compared were two time periods: (a) immediately after use and (b) 1-h after use.
One-hundred ten new endodontic files were used to prepare canals and were then cleaned using three different techniques: (a) gauze soaked with alcohol, (b) sponge soaked with alcohol, and (c) ultrasonic bath. The cleaning ability of each of these techniques immediately after use and after 1 h of delay were compared. Identical areas on each file were examined by using a custommade jig. Morphornetric analysis of debris was carried out using a Bioquant image analysis system. Sponge/alcohol was the worst cleaning method; this was significantly different from the other two techniques. The gauze/alcohol and ultrasonic bath were similar. The l-h delay before instrument cleaning did not affect the ability of any of the techniques tested. None of the methods tested were able to totally clean the files.
Materials and Methods Materials
One-hundred ten new #25 K-Flex endodontic files (Kerr Co., Romulus, MI) of 21 m m in length were used. To ensure that all of the files were clean prior to usage, they were placed in boiling water for 5 min; this was followed by 5 min in a Unity Model LU Ultrasonic Bath (L & R Manufacturing Co., Kearny, N J) containing a Dri-Clave cleaning solution (Columbus Dental, St. Louis, MO). These procedures were to remove any plastic or other debris which frequently remain on new files from the manufacturing process (8, 9). The files were randomly divided in eight groups: Group A (control) consisted of negative (no usage, no cleaning), l0 files, and positive (usage, no cleaning), l0 files. Group B (experimental) consisted of immediate cleaning: gauze/alcohol, 15 files; sponge/alcohol, 15 files; ultrasonic bath, 15 files and l-h delay: gauze/alcohol, 15 files; sponge/alcohol, 15 files; ultrasonic bath, 15 files.
During root canal instrumentation all types of debris are produced and encountered: necrotic and vital tissue, bacteria, dentin chips, blood by-products, and other potential irritants. The exchange of this debris via instruments from one patient to another is undesirable as these can act as antigens, infecting agents, or nonspecific irritants. Endodontic files are cleaned and sterilized to prevent this cross-infection or cross-contamination. Organic debris remaining on files may interfere with sterilization (1) and may also decrease the cutting ability of the life, with a consequent predisposition to fracture (2). Various methods for cleaning endodontic instruments have been proposed. Cotton rolls and gauze are used dry or soaked with antiseptic substances such as alcohol (3-5). Sponges have been used as an mechanical cleanser alone or combined with a detergent or antiseptic solution (6, 7). Hand brushes and rubber dam have also been suggested. Disadvantages of these are that the brushes are time consuming, operator sensitive, and tend to produce metal spurs, while the rubber dam leaves remnants of rubber on the files (8). Ultrasonic cleaners have the advantage of being faster and easier in cleaning dental instruments but presumably require
Methods
In all of the groups (except negative control), files were used for 4 min in a filing action in the canals of 40 humidified extracted teeth. During the instrumentation, 2 ml of distilled water was used as an irrigant solution simulating the irrigation
214
Cleaning Files after Usage
Vol. 16, No. 5, May 1990
done normally during root canal instrumentation. Each minute, 0.5 ml of distilled water was injected inside the canal with a syringe with a 27-gauge needle. The penetration of the needle was as deep as possible as in the clinical situation. The same operator irrigated and prepared all canals with a standardized instrumentation stroke. In all cases, only one side of the files was used to plane the canal wall with the location of the planing side identified with a mark on the plastic handle. Following instrumentation, all files (except positive controls) were submitted to one of three methods of cleaning: (a) sponge (Red Poly Sponge; IDL, Carlstad, NJ) with alcohol; (b) gauze with alcohol, or (c) ultrasonic bath vibration containing a Dri-Clave cleaning solution (Columbus Dental, St. Louis, MO) for 5 min. The number of strokes that the files were inserted into the sponge (two thrusts), and also the number of wipes when the gauze was used were standardized at two times for each instrument. All of the cleaning methods were carried out by the same operator to reduce variability. Cleaning methods were tested under two conditions: (a) immediately after usage and (b) after 1 h of delay. The hypothesis was that, with time the debris would dry and adhere to the file, making removal less effective.
215
RESULTS The data obtained are summarized in Table 1 and Fig. 2. The unused negative control files were very clean (Fig. 3). In spite of the clean appearance of the files in the negative control group, they were not completely free of debris. Statistical analysis showed no significant differences between the negative control group and the used files which were then cleaned by gauze or by ultrasonic vibration (Table 1). The type of debris present on the files was predominantly plastic and metal particles. The group demonstrating a statistically significant high debris score (Table l) was the positive control files, which were used but not cleaned. The flutes accumulated considerable debris over the entire surface (Fig. 4). None of the cleaning techniques, whether used immediately or l h after canal preparation consistently removed all of the debris from the flutes (Fig. 5). Two techniques were superior. The ultrasonic cleaning and the gauze/alcohol were statistically similar; both were significantly more effective in removal of debris from files than the sponge/alcohol method (Table 1). There were no significant differences (p < 0.05) between cleaning immediately or after a l-h delay (Table l).
Evaluation
DISCUSSION All files were examined using an A M R A Y 1820 scanning electron microscope. In order to standardize the area of observation, a special file holder jig was made with acrylic (Fig. 1). Three regions o f each file, each 0.6 m m in length, from the apical, middle, and cervical portions of the instruments were examined. Photomicrographs were made to include the entire region. On each photomicrograph, the area of debris was measured with the Bioquant (R & M Biometrics Inc., Nashville, TN). Then, the area of debris from the three regions (Fig. 1) was combined to give a total for each instrument. Means were calculated for each control and instrument cleaning group. Comparisons were made between groups and between times of cleaning (immediately versus 1 h of delay) using analysis of variance (p < 0.05) and Duncan's multiple range test (a < 0.05).
The necessity for an efficient as well as an effective method for cleaning endodontic files is well documented in the literature (1-9). Files have a complicated design. Debris accumulates between the flutes in an area which is relatively inaccessible for cleaning. Manual debridement techniques are time consuming, have considerable operator error, and risk additional contamination. Even with the care that was given to cleaning the instruments in our study, debris still remained. Therefore it is possible, even likely, that contaminants frequently are transferred from one patient to another via unclean files. As a single technique, the ultrasonic bath and gauze/alcohol cleaning were found to be the best methods for removal of debris from the files. Despite the fact that there were no statistical differences between gauze/alcohol and the ultrasonic vibration (in conjunction with a cleaning solution), the latter may be suggested as the method of choice for cleaning files. It is not as time consuming (particularly when cleaning several files) or as technique sensitive; also, the risk of contamination during instrument manipulation is very low. Another
TABLE 1. Duncan's multiple range test (a = 0.05)
FIG 1. Instrument holder developed to stabilize and standardize the areas to be examined, The side of the file used against the canal walls would always face upward, The a r r o w s show the three regions (0.6-mm each) that were viewed and evaluated under the SEM.
Group
Mean Areas (ram2)
Duncan's grouping*
Positive control Sponge Sponge + 1 h Gauze Gauze + 1 h Ultrasonic Ultrasonic + 1 h Negative control
8.7686 0.9284 0.7262 0.2263 0.1773 0.1193 0.1538 0.0259
A B B C C C C C
9 Means with the same letter are not s,,gniflcantly different from each other.
216
Journal of Endodontics
Murgel et al. Amount
of Debris
Remaining
9.0-
t~
r - ~ Positivecontrol Sponge ~ Sponge+ 1 hour ~ Gauze ~ Gauze+ 1 hour ~ Ultra ~'~ U l t r a + 1 hour m Negativecontrol
8.5-
E E 1.0 N\\N~
I1)
Q ,\\N\ ,N\\\
2
0.5 '
o:u_,:
'\\\~: \\\\,
_~:::::
N\\\ ~
:::',_-~::: :~:5::::
:::~J:l:l
,\\\\ N\\N~
:,'-_::::::; ~,'_-,'-_: :::::.~::: :::;::::::~
Groups FiG 2. The X axis is the cleaning techniques/times. The Y axis is the combined debris measurements from the viewed regions from each file.
consideration is that a combination of gauze/alcohol (or perhaps hand brushing) followed by ultrasonic cleaning might be superior to any single technique, but this combination has not been examined. Further research is necessary to evaluate this combination of techniques. The gauze/alcohol technique may be used as an immediate chairside method of cleaning files during root canal preparation. However, this is time consuming, operator sensitive, and also at risk for contamination during the cleaning procedure. Another important disadvantage is that cotton fibers occasionally are retained on the file surface (5) during the cleaning procedure (Fig. 6) and may contain bacteria or other contaminants that could be introduced into the canal or periapex. An interesting finding was that the delay of 1 h did not affect the ability to clean the files; i.e. in all groups there were no significant differences between the two time periods. This is important in the clinical situation, where the instruments are generally cleaned at the end of the appointment or even later in the day. Sponge/alcohol was the worst method for file cleaning
FrG 5. Experimental group (sponge/alcohol). Some debris (arrow) clings to the surface (original magnification x150). FIG 3. Negative control file (unused, cleaned). A clean surface but with a small metallic fragment (original magnification x150).
FIG 4. Positive control file (used, uncleaned). The surface is covered with debris (original magnification x 150).
FIG 6. Gauze/alcohol experimental group. Debris is adherent to the instrument. Also, there appear to be cotton fibers, probably from the gauze (original magnification x150).
Vol. 16, No. 5, May 1990
Cleaning Files after Usage
m~m ~
217
As an additional observation, instruments that have defects on the surface may increase debris retention (Fig. 7). Such defects and damaged flutes may be created during canal preparation and by operator manipulation such as in precurving the instruments (l 0). Not only would these defects weaken the file, they create areas for debris retention ( l 1). The authors woold like to thank Jane Jakobsen for her advice with the statistical analysis and John Laffooo and Chades Lesch for their technical support.
FIG 7. Note surface defects with debris accumulated in the same area. The defect contributes to the debris retention (original magnification x150).
whether used immediately or after 1 h. This may be due to the sponge being soft. When the file penetrates, there is not enough force to promote an intimate contact between the flutes of the files and the sponge; consequently, the debris is not physically loosened sufficiently to allow easy removal. Organic solvents and disinfectants are usually combined in hopes of increasing the cleaning effect. But, in our study, if alcohol was the mosl important factor in cleaning, the gauze and sponge would have been equivalent. However, because the gauze was superior, this suggests that a mechanical rather than a chemical action was the key factor. The presence of plastic debris and metal spurs on new files were also found, although all new instruments were placed in an ultrasonic bath prior to use in canals. These findings are in agreement with those o f Segall et al. (8). New files should therefore not be used in patients without being first subjected to cleaning and sterilization to minimize manufacturer's debris. Better quality control over instrument fabrication and handling to prevent contamination and debris deposition would eliminate or diminish this problem.
Dr. Murgel is a visiting fellow, Department of Endodontics, College of Dentistry, University of Iowa, Iowa City, Iowa. Dr. Walton is professor and head, Department of Endodontics, College of Dentistry, University of Iowa. Dr. Rittman is associate professor, Department of Endodontics and Dows Institute for Dental Research, College of Dentistry, University of Iowa. Dr. P~3ora is assistant professor, Mestre da Disciplina de Endodontia, Faculty of Odontology, University of S&o Paulo. Ribe~r&o Preto, Brazil.
References 1. Perkins JJ. Principles and methods of sterilization. Springfield, IL: Charles C Thomas. 1956:129. 2. Grossman LI. Fate of endodontically treated teeth with fractured root canal instruments. J Br Ended Soc 1968;2:35-7. 3. Greene HG. Simplified eododontic file and reamer cleaner. J Am Dent Assoc 1965;70:79-82. 4. Grossman LI. Prevention of fracture of root canal instruments. Oral Surg 1969;28:746-52. 5. Segall Re, Del Rio CE, Brady JM, Ayer WA. Evaluation of debridernent techniques for endodontics instruments. Oral Surg 1977;44:786-91. 6. Buchbinder M. A sponge rubber chemical stedlizer for endodontic instruments. NY J Dent 1954;26:116-9. 7. Curson I. Root canal instruments and their sterilization. Br Dent J 1966;121:289-95. 8. Segall Re, De( Rio CE, Brady JM, Ayer WA. Evaluation of endodontic instruments as received from the manufacture: the demand for quality control. Oral Surg 1977;44:463-67. 9. Gutierrez JH, Gigoux C, Sanhueza I. Physical and chemical deterioration of endodontic reamers during mechanical preparation. Oral Surg 1969;28:394403. 10. Yesilsoy C, Koran I..Z, Bo4anos Re, Morse DR. A scanning e(ectron microscopic examination of surface changes obtained from two variable methods of precurving files: a clinical observation. J Endodon 1986;12:408-13. 11. Scott GL, Walton RE Ultrasonic endodontics: the wear of instruments. J Endodon 1986;12:279-83.
Printed in U.S.A.
VOL. 16, No. 5, MAY 1990
A Comparison of Techniques for Cleaning Endodontic Files after Usage: A Quantitative Scanning Electron Microscopic Study Carlos Alberto Ferreira Murgel, CD, Richard E. Walton, DDS, MS, Barry Rittman, PhD, and Jesus Djalma Pecora, CD, MC
care and attention both for initial instrument preparation and for appropriate time of usage. However, the effectiveness of ultrasonic cleaning of used files has not been investigated. In the clinical situation endodontic files are generally cleaned at the conclusion of the appointment or even at the end of the day. This delay may decrease the efficacy of removal once the debris has dried, although this delay factor has not been tested. The objective of this study was to quantitate and compare debris remaining on endodontic files after one of three techniques of cleaning: (a) sponge soaked with alcohol, (b) gauze soaked with alcohol, or (c) ultrasonic bath. Also compared were two time periods: (a) immediately after use and (b) 1-h after use.
One-hundred ten new endodontic files were used to prepare canals and were then cleaned using three different techniques: (a) gauze soaked with alcohol, (b) sponge soaked with alcohol, and (c) ultrasonic bath. The cleaning ability of each of these techniques immediately after use and after 1 h of delay were compared. Identical areas on each file were examined by using a custommade jig. Morphornetric analysis of debris was carried out using a Bioquant image analysis system. Sponge/alcohol was the worst cleaning method; this was significantly different from the other two techniques. The gauze/alcohol and ultrasonic bath were similar. The l-h delay before instrument cleaning did not affect the ability of any of the techniques tested. None of the methods tested were able to totally clean the files.
Materials and Methods Materials
One-hundred ten new #25 K-Flex endodontic files (Kerr Co., Romulus, MI) of 21 m m in length were used. To ensure that all of the files were clean prior to usage, they were placed in boiling water for 5 min; this was followed by 5 min in a Unity Model LU Ultrasonic Bath (L & R Manufacturing Co., Kearny, N J) containing a Dri-Clave cleaning solution (Columbus Dental, St. Louis, MO). These procedures were to remove any plastic or other debris which frequently remain on new files from the manufacturing process (8, 9). The files were randomly divided in eight groups: Group A (control) consisted of negative (no usage, no cleaning), l0 files, and positive (usage, no cleaning), l0 files. Group B (experimental) consisted of immediate cleaning: gauze/alcohol, 15 files; sponge/alcohol, 15 files; ultrasonic bath, 15 files and l-h delay: gauze/alcohol, 15 files; sponge/alcohol, 15 files; ultrasonic bath, 15 files.
During root canal instrumentation all types of debris are produced and encountered: necrotic and vital tissue, bacteria, dentin chips, blood by-products, and other potential irritants. The exchange of this debris via instruments from one patient to another is undesirable as these can act as antigens, infecting agents, or nonspecific irritants. Endodontic files are cleaned and sterilized to prevent this cross-infection or cross-contamination. Organic debris remaining on files may interfere with sterilization (1) and may also decrease the cutting ability of the life, with a consequent predisposition to fracture (2). Various methods for cleaning endodontic instruments have been proposed. Cotton rolls and gauze are used dry or soaked with antiseptic substances such as alcohol (3-5). Sponges have been used as an mechanical cleanser alone or combined with a detergent or antiseptic solution (6, 7). Hand brushes and rubber dam have also been suggested. Disadvantages of these are that the brushes are time consuming, operator sensitive, and tend to produce metal spurs, while the rubber dam leaves remnants of rubber on the files (8). Ultrasonic cleaners have the advantage of being faster and easier in cleaning dental instruments but presumably require
Methods
In all of the groups (except negative control), files were used for 4 min in a filing action in the canals of 40 humidified extracted teeth. During the instrumentation, 2 ml of distilled water was used as an irrigant solution simulating the irrigation
214
Cleaning Files after Usage
Vol. 16, No. 5, May 1990
done normally during root canal instrumentation. Each minute, 0.5 ml of distilled water was injected inside the canal with a syringe with a 27-gauge needle. The penetration of the needle was as deep as possible as in the clinical situation. The same operator irrigated and prepared all canals with a standardized instrumentation stroke. In all cases, only one side of the files was used to plane the canal wall with the location of the planing side identified with a mark on the plastic handle. Following instrumentation, all files (except positive controls) were submitted to one of three methods of cleaning: (a) sponge (Red Poly Sponge; IDL, Carlstad, NJ) with alcohol; (b) gauze with alcohol, or (c) ultrasonic bath vibration containing a Dri-Clave cleaning solution (Columbus Dental, St. Louis, MO) for 5 min. The number of strokes that the files were inserted into the sponge (two thrusts), and also the number of wipes when the gauze was used were standardized at two times for each instrument. All of the cleaning methods were carried out by the same operator to reduce variability. Cleaning methods were tested under two conditions: (a) immediately after usage and (b) after 1 h of delay. The hypothesis was that, with time the debris would dry and adhere to the file, making removal less effective.
215
RESULTS The data obtained are summarized in Table 1 and Fig. 2. The unused negative control files were very clean (Fig. 3). In spite of the clean appearance of the files in the negative control group, they were not completely free of debris. Statistical analysis showed no significant differences between the negative control group and the used files which were then cleaned by gauze or by ultrasonic vibration (Table 1). The type of debris present on the files was predominantly plastic and metal particles. The group demonstrating a statistically significant high debris score (Table l) was the positive control files, which were used but not cleaned. The flutes accumulated considerable debris over the entire surface (Fig. 4). None of the cleaning techniques, whether used immediately or l h after canal preparation consistently removed all of the debris from the flutes (Fig. 5). Two techniques were superior. The ultrasonic cleaning and the gauze/alcohol were statistically similar; both were significantly more effective in removal of debris from files than the sponge/alcohol method (Table 1). There were no significant differences (p < 0.05) between cleaning immediately or after a l-h delay (Table l).
Evaluation
DISCUSSION All files were examined using an A M R A Y 1820 scanning electron microscope. In order to standardize the area of observation, a special file holder jig was made with acrylic (Fig. 1). Three regions o f each file, each 0.6 m m in length, from the apical, middle, and cervical portions of the instruments were examined. Photomicrographs were made to include the entire region. On each photomicrograph, the area of debris was measured with the Bioquant (R & M Biometrics Inc., Nashville, TN). Then, the area of debris from the three regions (Fig. 1) was combined to give a total for each instrument. Means were calculated for each control and instrument cleaning group. Comparisons were made between groups and between times of cleaning (immediately versus 1 h of delay) using analysis of variance (p < 0.05) and Duncan's multiple range test (a < 0.05).
The necessity for an efficient as well as an effective method for cleaning endodontic files is well documented in the literature (1-9). Files have a complicated design. Debris accumulates between the flutes in an area which is relatively inaccessible for cleaning. Manual debridement techniques are time consuming, have considerable operator error, and risk additional contamination. Even with the care that was given to cleaning the instruments in our study, debris still remained. Therefore it is possible, even likely, that contaminants frequently are transferred from one patient to another via unclean files. As a single technique, the ultrasonic bath and gauze/alcohol cleaning were found to be the best methods for removal of debris from the files. Despite the fact that there were no statistical differences between gauze/alcohol and the ultrasonic vibration (in conjunction with a cleaning solution), the latter may be suggested as the method of choice for cleaning files. It is not as time consuming (particularly when cleaning several files) or as technique sensitive; also, the risk of contamination during instrument manipulation is very low. Another
TABLE 1. Duncan's multiple range test (a = 0.05)
FIG 1. Instrument holder developed to stabilize and standardize the areas to be examined, The side of the file used against the canal walls would always face upward, The a r r o w s show the three regions (0.6-mm each) that were viewed and evaluated under the SEM.
Group
Mean Areas (ram2)
Duncan's grouping*
Positive control Sponge Sponge + 1 h Gauze Gauze + 1 h Ultrasonic Ultrasonic + 1 h Negative control
8.7686 0.9284 0.7262 0.2263 0.1773 0.1193 0.1538 0.0259
A B B C C C C C
9 Means with the same letter are not s,,gniflcantly different from each other.
216
Journal of Endodontics
Murgel et al. Amount
of Debris
Remaining
9.0-
t~
r - ~ Positivecontrol Sponge ~ Sponge+ 1 hour ~ Gauze ~ Gauze+ 1 hour ~ Ultra ~'~ U l t r a + 1 hour m Negativecontrol
8.5-
E E 1.0 N\\N~
I1)
Q ,\\N\ ,N\\\
2
0.5 '
o:u_,:
'\\\~: \\\\,
_~:::::
N\\\ ~
:::',_-~::: :~:5::::
:::~J:l:l
,\\\\ N\\N~
:,'-_::::::; ~,'_-,'-_: :::::.~::: :::;::::::~
Groups FiG 2. The X axis is the cleaning techniques/times. The Y axis is the combined debris measurements from the viewed regions from each file.
consideration is that a combination of gauze/alcohol (or perhaps hand brushing) followed by ultrasonic cleaning might be superior to any single technique, but this combination has not been examined. Further research is necessary to evaluate this combination of techniques. The gauze/alcohol technique may be used as an immediate chairside method of cleaning files during root canal preparation. However, this is time consuming, operator sensitive, and also at risk for contamination during the cleaning procedure. Another important disadvantage is that cotton fibers occasionally are retained on the file surface (5) during the cleaning procedure (Fig. 6) and may contain bacteria or other contaminants that could be introduced into the canal or periapex. An interesting finding was that the delay of 1 h did not affect the ability to clean the files; i.e. in all groups there were no significant differences between the two time periods. This is important in the clinical situation, where the instruments are generally cleaned at the end of the appointment or even later in the day. Sponge/alcohol was the worst method for file cleaning
FrG 5. Experimental group (sponge/alcohol). Some debris (arrow) clings to the surface (original magnification x150). FIG 3. Negative control file (unused, cleaned). A clean surface but with a small metallic fragment (original magnification x150).
FIG 4. Positive control file (used, uncleaned). The surface is covered with debris (original magnification x 150).
FIG 6. Gauze/alcohol experimental group. Debris is adherent to the instrument. Also, there appear to be cotton fibers, probably from the gauze (original magnification x150).
Vol. 16, No. 5, May 1990
Cleaning Files after Usage
m~m ~
217
As an additional observation, instruments that have defects on the surface may increase debris retention (Fig. 7). Such defects and damaged flutes may be created during canal preparation and by operator manipulation such as in precurving the instruments (l 0). Not only would these defects weaken the file, they create areas for debris retention ( l 1). The authors woold like to thank Jane Jakobsen for her advice with the statistical analysis and John Laffooo and Chades Lesch for their technical support.
FIG 7. Note surface defects with debris accumulated in the same area. The defect contributes to the debris retention (original magnification x150).
whether used immediately or after 1 h. This may be due to the sponge being soft. When the file penetrates, there is not enough force to promote an intimate contact between the flutes of the files and the sponge; consequently, the debris is not physically loosened sufficiently to allow easy removal. Organic solvents and disinfectants are usually combined in hopes of increasing the cleaning effect. But, in our study, if alcohol was the mosl important factor in cleaning, the gauze and sponge would have been equivalent. However, because the gauze was superior, this suggests that a mechanical rather than a chemical action was the key factor. The presence of plastic debris and metal spurs on new files were also found, although all new instruments were placed in an ultrasonic bath prior to use in canals. These findings are in agreement with those o f Segall et al. (8). New files should therefore not be used in patients without being first subjected to cleaning and sterilization to minimize manufacturer's debris. Better quality control over instrument fabrication and handling to prevent contamination and debris deposition would eliminate or diminish this problem.
Dr. Murgel is a visiting fellow, Department of Endodontics, College of Dentistry, University of Iowa, Iowa City, Iowa. Dr. Walton is professor and head, Department of Endodontics, College of Dentistry, University of Iowa. Dr. Rittman is associate professor, Department of Endodontics and Dows Institute for Dental Research, College of Dentistry, University of Iowa. Dr. P~3ora is assistant professor, Mestre da Disciplina de Endodontia, Faculty of Odontology, University of S&o Paulo. Ribe~r&o Preto, Brazil.
References 1. Perkins JJ. Principles and methods of sterilization. Springfield, IL: Charles C Thomas. 1956:129. 2. Grossman LI. Fate of endodontically treated teeth with fractured root canal instruments. J Br Ended Soc 1968;2:35-7. 3. Greene HG. Simplified eododontic file and reamer cleaner. J Am Dent Assoc 1965;70:79-82. 4. Grossman LI. Prevention of fracture of root canal instruments. Oral Surg 1969;28:746-52. 5. Segall Re, Del Rio CE, Brady JM, Ayer WA. Evaluation of debridernent techniques for endodontics instruments. Oral Surg 1977;44:786-91. 6. Buchbinder M. A sponge rubber chemical stedlizer for endodontic instruments. NY J Dent 1954;26:116-9. 7. Curson I. Root canal instruments and their sterilization. Br Dent J 1966;121:289-95. 8. Segall Re, De( Rio CE, Brady JM, Ayer WA. Evaluation of endodontic instruments as received from the manufacture: the demand for quality control. Oral Surg 1977;44:463-67. 9. Gutierrez JH, Gigoux C, Sanhueza I. Physical and chemical deterioration of endodontic reamers during mechanical preparation. Oral Surg 1969;28:394403. 10. Yesilsoy C, Koran I..Z, Bo4anos Re, Morse DR. A scanning e(ectron microscopic examination of surface changes obtained from two variable methods of precurving files: a clinical observation. J Endodon 1986;12:408-13. 11. Scott GL, Walton RE Ultrasonic endodontics: the wear of instruments. J Endodon 1986;12:279-83.
