0099-2399/91/1707-0346/$03,00/0 JOURNAL OF ENDODONTICS Copyright 9 1991 by The American Association of Endodontists
Printed in U.S.A.
VOL. 17, NO. 7, JULY 1991
Lack of Corrosion of Stainless Steel Instruments In Vivo by Scanning Electron Microscope and Microprobe Analysis P. D. Eleazer, DDS, MS
Two clinical cases are presented which show no corrosion of broken stainless steel endodontic instruments. Corrosion of a silver endodontic filling cone is demonstrated.
Several authors have commented on the problems associated with carbon steel instruments broken in root canals (1, 2). The fact that stainless steel instruments do not corrode like those made of carbon steel is often not appreciated. Stainless steel is frequently intentionally placed in the body with no deleterious effects, e.g. orthopedic devices, heart valves, aneurysm clips, etc. Crump and Natkin (3) found good success after instrument failure, regardless of pretreatment condition of pulp or periapical tissues. Fox et al. (4) accidentally or intentionally used endodontic instruments to fill root canal spaces in over 300 teeth with good clinical results. The purpose of this article is to report on two endodontic cases which failed after root canal instruments were broken in the root canals. Scanning electron microscope and microprobe analyses of the broken fragments were made. The scanning electron microscopic examination provided a picture of the surface of the materials, revealing the presence or absence of corrosion pits, cavitations, or craters. X-ray microprobe analysis with back-scattered electron images was then used to locate, analyze, and identify the various elements on the surfaces of the materials.
FiG 1. Case 1 : preoperative radiograph,
CASE 1 The patient presented with an acute periapical abscess of the mandibular left first molar 61 months after endodontic treatment had been performed by a general practitioner. The mesial canals exhibited silver cone root fillings; a broken instrument was found in a distal canal, apparently containing gutta-percha (Fig. 1). The pulp chamber contained purulent material in contact with the stainless steel instrument. The silver cones were removed easily, one being accidentally suctioned away; the other, markedly covered with black material, was retrieved for analysis. An untreated distobuccal canal, which was filled with necrotic tissue and pus, was discovered
FIG 2. Case 1 : instrument measurement radiograph, showing second distal canal.
(Fig. 2). The fragment of stainless steel instrument was easily removed from the distolingual canal, packaged separately, and submitted for analysis. No discoloration was noted on gross examination. No corrosion was seen on the stainless steel instrument when examined with a scanning electron microscope (Fig. 3). The microprobe analysis showed normal
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Vol. 17, No. 7, July 1991
No Corrosion on Stainless Instruments
FIG 3. Case 1 : scanning electron micrograph of broken stainless steel instrument.
FtG 4. Case 1 : microprobe analysis of stainless steel instrument.
components of stainless steel with no elements indicative of corrosion (Fig. 4). The scanning electron micrograph of the silver cone showed areas of corrosion along with tooling marks from manufacture (Fig. 5). Microprobe analysis showed the presence of elements which are indicative of amalgam (silver, mercury, and zinc) (Fig. 6). A sulfur peak, indicative of corrosion was also detected in another analysis. CASE 2 The maxillary right first molar of this patient was treated
347
FtG 5. Case 1 : scanning electron micrograph of silver cone.
Fta 6. Case 1 : microprobe analysis of silver cone.
endodontically by the author 21 months earlier because of pulpitis secondary to periodontal disease. During treatment, a #30 Hedstrom file was accidentally broken in the distobuccal canal. Normal instrumentation force was used (Fig. 7). Clinically, the canal appeared to be clean at the time of instrument failure. This tooth was removed by the general dentist because of progression of the periodontal disease with severe furcation involvement. The tooth was submitted in Formalin. The root was fractured by the author: the instrument was removed and presented for analysis. Scanning electron micrographs revealed no corrosion (Fig. 8). Fracture lines in the metal indicated a flaw in the metal, explaining the ease of fracture (Fig. 9).
348
Eleazer
Journal of Endodontics
FiG 9. Higher magnification shows metal defect. FIG 7. Case 1 : postoperative radiograph.
FiG 8. Case 2: scanning electron micrograph of broken instrument.
Microprobe analysis showed the presence of the normal elements of stainless steel. These included iron, chromium, magnesium, and nickel (Fig. 10). Calcium and phosphorus were also detected, likely due to dentin filings and/or Sealapex root canal sealer which was used for obturation of the canal coronal to the instrument. DISCUSSION No corrosion products were found on the broken stainless steel instruments, which had been present in vivo for many months. By comparison, corrosion of a silver root canal filling cone was found. Treatment failure specifically related to corrosion of broken stainless steel endodontic instruments should be of no major concern because of their relatively inert nature. The concern is minimized if the fragment is within the canal and the canal has been debrided at the time of instrument failure. This report has shown no corrosion with stainless steel instruments contrasted with significant corrosion on a silver cone.
FIG 10. Case 2: microprobe analysis of stainless steel instrument.
In our current litigious society, it would probably be wise to retain the remainder of the broken instrument, should it be necessary to determine if a fault due to manufacturing error were the cause of failure. Furthermore, current practice requires that the patient be informed of the instrument problem. This explanation should include the information that most stainless steel implants are innocuous. The author's opinion is that some patients may be better treated by not being informed, in cases in which excessive patient concern has the potential for becoming a psychological problem. It must also be acknowledged that it is possible for small instrument fragments to be left in canals without the practitioner's knowledge. When stainless steel instrument fragments are
Vol. 17, No. 7, July 1991
present in root canal spaces, it is reasonable not to expect failure of treatment due to corrosion products. The author gratefully acknowledges the assistance of Dr. Samuel Seltzer in SEM and microprobe analyses and for advice in manuscript preparation. Dr. Eleazer is assistant clinical professor at the Medical College of Virginia, Richmond, VA, and is in private practice in Albany, GA. Address requests for reprints to Dr. Paul Eleazer, 1503 Third Avenue, Albany, GA 31707.
No Corrosion on Stainless Instruments
349
References 1. Eichner MA, Schoen DM, Goldman M, Kronman JH. Effect of protein and sodium hypochlorite on endodontic instruments. J Endodon 1976;2:3358. 2. Oliet S, Sorrin SM. Inhibition of the corrosive effect of sodium hypochlorite on carbon steel endodontic instruments. J Endodon 1978;4:12-6. 3. Crump MC, Natkin E. Relationship of broken root canal instruments to endodontic case prognosis. J Am Dent Assoc 1970;80:1341-7. 4. Fox J, Moodnik RM, Greenfield E, Atkinson JS. Filling root canals with files. NY State Dent J 1972;38:154-7.
You Might Be Interested to Know State pride was in evidence when someone named a new polyene antifungal agent in honor of the great state of New York. Nystatin was discovered by the New York State Health Laboratory. John Smith
Printed in U.S.A.
VOL. 17, NO. 7, JULY 1991
Lack of Corrosion of Stainless Steel Instruments In Vivo by Scanning Electron Microscope and Microprobe Analysis P. D. Eleazer, DDS, MS
Two clinical cases are presented which show no corrosion of broken stainless steel endodontic instruments. Corrosion of a silver endodontic filling cone is demonstrated.
Several authors have commented on the problems associated with carbon steel instruments broken in root canals (1, 2). The fact that stainless steel instruments do not corrode like those made of carbon steel is often not appreciated. Stainless steel is frequently intentionally placed in the body with no deleterious effects, e.g. orthopedic devices, heart valves, aneurysm clips, etc. Crump and Natkin (3) found good success after instrument failure, regardless of pretreatment condition of pulp or periapical tissues. Fox et al. (4) accidentally or intentionally used endodontic instruments to fill root canal spaces in over 300 teeth with good clinical results. The purpose of this article is to report on two endodontic cases which failed after root canal instruments were broken in the root canals. Scanning electron microscope and microprobe analyses of the broken fragments were made. The scanning electron microscopic examination provided a picture of the surface of the materials, revealing the presence or absence of corrosion pits, cavitations, or craters. X-ray microprobe analysis with back-scattered electron images was then used to locate, analyze, and identify the various elements on the surfaces of the materials.
FiG 1. Case 1 : preoperative radiograph,
CASE 1 The patient presented with an acute periapical abscess of the mandibular left first molar 61 months after endodontic treatment had been performed by a general practitioner. The mesial canals exhibited silver cone root fillings; a broken instrument was found in a distal canal, apparently containing gutta-percha (Fig. 1). The pulp chamber contained purulent material in contact with the stainless steel instrument. The silver cones were removed easily, one being accidentally suctioned away; the other, markedly covered with black material, was retrieved for analysis. An untreated distobuccal canal, which was filled with necrotic tissue and pus, was discovered
FIG 2. Case 1 : instrument measurement radiograph, showing second distal canal.
(Fig. 2). The fragment of stainless steel instrument was easily removed from the distolingual canal, packaged separately, and submitted for analysis. No discoloration was noted on gross examination. No corrosion was seen on the stainless steel instrument when examined with a scanning electron microscope (Fig. 3). The microprobe analysis showed normal
346
Vol. 17, No. 7, July 1991
No Corrosion on Stainless Instruments
FIG 3. Case 1 : scanning electron micrograph of broken stainless steel instrument.
FtG 4. Case 1 : microprobe analysis of stainless steel instrument.
components of stainless steel with no elements indicative of corrosion (Fig. 4). The scanning electron micrograph of the silver cone showed areas of corrosion along with tooling marks from manufacture (Fig. 5). Microprobe analysis showed the presence of elements which are indicative of amalgam (silver, mercury, and zinc) (Fig. 6). A sulfur peak, indicative of corrosion was also detected in another analysis. CASE 2 The maxillary right first molar of this patient was treated
347
FtG 5. Case 1 : scanning electron micrograph of silver cone.
Fta 6. Case 1 : microprobe analysis of silver cone.
endodontically by the author 21 months earlier because of pulpitis secondary to periodontal disease. During treatment, a #30 Hedstrom file was accidentally broken in the distobuccal canal. Normal instrumentation force was used (Fig. 7). Clinically, the canal appeared to be clean at the time of instrument failure. This tooth was removed by the general dentist because of progression of the periodontal disease with severe furcation involvement. The tooth was submitted in Formalin. The root was fractured by the author: the instrument was removed and presented for analysis. Scanning electron micrographs revealed no corrosion (Fig. 8). Fracture lines in the metal indicated a flaw in the metal, explaining the ease of fracture (Fig. 9).
348
Eleazer
Journal of Endodontics
FiG 9. Higher magnification shows metal defect. FIG 7. Case 1 : postoperative radiograph.
FiG 8. Case 2: scanning electron micrograph of broken instrument.
Microprobe analysis showed the presence of the normal elements of stainless steel. These included iron, chromium, magnesium, and nickel (Fig. 10). Calcium and phosphorus were also detected, likely due to dentin filings and/or Sealapex root canal sealer which was used for obturation of the canal coronal to the instrument. DISCUSSION No corrosion products were found on the broken stainless steel instruments, which had been present in vivo for many months. By comparison, corrosion of a silver root canal filling cone was found. Treatment failure specifically related to corrosion of broken stainless steel endodontic instruments should be of no major concern because of their relatively inert nature. The concern is minimized if the fragment is within the canal and the canal has been debrided at the time of instrument failure. This report has shown no corrosion with stainless steel instruments contrasted with significant corrosion on a silver cone.
FIG 10. Case 2: microprobe analysis of stainless steel instrument.
In our current litigious society, it would probably be wise to retain the remainder of the broken instrument, should it be necessary to determine if a fault due to manufacturing error were the cause of failure. Furthermore, current practice requires that the patient be informed of the instrument problem. This explanation should include the information that most stainless steel implants are innocuous. The author's opinion is that some patients may be better treated by not being informed, in cases in which excessive patient concern has the potential for becoming a psychological problem. It must also be acknowledged that it is possible for small instrument fragments to be left in canals without the practitioner's knowledge. When stainless steel instrument fragments are
Vol. 17, No. 7, July 1991
present in root canal spaces, it is reasonable not to expect failure of treatment due to corrosion products. The author gratefully acknowledges the assistance of Dr. Samuel Seltzer in SEM and microprobe analyses and for advice in manuscript preparation. Dr. Eleazer is assistant clinical professor at the Medical College of Virginia, Richmond, VA, and is in private practice in Albany, GA. Address requests for reprints to Dr. Paul Eleazer, 1503 Third Avenue, Albany, GA 31707.
No Corrosion on Stainless Instruments
349
References 1. Eichner MA, Schoen DM, Goldman M, Kronman JH. Effect of protein and sodium hypochlorite on endodontic instruments. J Endodon 1976;2:3358. 2. Oliet S, Sorrin SM. Inhibition of the corrosive effect of sodium hypochlorite on carbon steel endodontic instruments. J Endodon 1978;4:12-6. 3. Crump MC, Natkin E. Relationship of broken root canal instruments to endodontic case prognosis. J Am Dent Assoc 1970;80:1341-7. 4. Fox J, Moodnik RM, Greenfield E, Atkinson JS. Filling root canals with files. NY State Dent J 1972;38:154-7.
You Might Be Interested to Know State pride was in evidence when someone named a new polyene antifungal agent in honor of the great state of New York. Nystatin was discovered by the New York State Health Laboratory. John Smith
