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An evaluation of a new mechanized endodontic device: The Endolift
An evaluation of a new mechanized endodontic device : The Endolift Joseph W. Lehman, III, MARQUETTE
UNIVERSITY
D. D.S., * and Harold Gerstein, B.S., D. D.S.,** Milwaukee, SCHOOL
Wis.
OF DENTISTRY
Four methods of canal preparation are tested: hand instrumentation with preflaring and step back, Giromatic, Union Broach Endo Angle, and the Kerr Endolift. The preparations are analyzed with plastic blocks and extracted human teeth. Hand instrumentation with preflaring and step-back is superior to and safer than the mechanized endodontic devices. With proper care and technique, some mechanized endodontic devices can produce adequate canal preparations.
N ext to proper diagnosis, the most important phase of endodontic treatment is proper canal
The opinions or assertions contained herein are those of the authors and are not to be construed as official or reflecting the views of the Department of the Navy. *Commander (DC) U. S. Navy, in civilian residency training and second year resident in Endodontics. **Professor and Chairman, Department of Endodontics.
endodontic devices. Frank’ and Klayman and Brilliants reported on the use of the Giromatic. O’Connell and BraytonY reported on the use of the Giromatic and W. and H. Endodontic Contra Angle. All the investigators concluded that hand instrumentation is superior to the mechanized instrumentation. The purpose of this study is to analyze a new mechanized endodontic instrument, the Endolift. In 1975 Weine, Kelly, and Lie” reported on the use of simulated canals in clear casting resin blocks. Similar blocks are used in this study to show the effect that canal preparation procedures have on the original canal shape. In this report we attempt to look at the character of the root canal preparation in the apical third (to note zipping or elliptication). The abilities of the instruments tested to negotiate tight canals, fracture potential, ledging, and perforation potential are
Giromatic handpiecewith Hedstromdesignfile.
Fig. 2. Union Broach Endo Angle handpiece with K fype file in test handle holder.
preparation.‘. 2 Proper biomechanical instrumentation of the root canal is the primary method of eliminating toxic products in the canaL3,4 The root canal must be properly shaped and cleansed to be properly 0bturated.j When the debris of the root canal system has been sufficiently reduced and an adequate area provided for a filling made with the preparation, a variety of filling techniques may be utilized to obtain a successful result.” Previous studies have been made on mechanized
Fig.
1.
417
418
Lehman and Gerstein
reviewed. Attention is also paid to the time involved with the various preparations and the speed at which to use the mechanized devices. Findings, with a clinical case in which the Endolift was used, are also presented. METHODS
AND MATERIALS
Four methods of canal preparation in this study: (1) hand instrumentation ing and step-back, (2) Giromatic* Flg. 4. Endo-Vu mented.
Model
001 plastic
block
uninstru-
are analyzed with preflar(instrument
*Micro Mega Export. 3 rue de la Mairie CH-1211 Geneve 6. Switzerland.
Volume 53 Number 4
New mechanized endodontic device: Endolift
419
Fig. 7. Effectof varied speedson the Giromaticpreparation. A, Giromatic preparation slow speed;B, giromatic preparation at higher speeds; arrow denotes neck of “hour-glasseffect” type of preparation.
designed to rotate a quarter turn in alternate directions’-Fig. I), (3) Union Broach Endo Angle* (designed to rotate alternate quarter-turn movement continuous speed to 3,000 r.p.m.-Fig. 2) and (4) Kerr Endolift-1 (up-and-down motion with a slight turning motion-Fig. 3). The study is divided into two phases: a plastic block phase and an extracted human teeth phase. Endo-Vu model 001x curved plastic blocks are
used (Fig. 4). In the first phase of the block study, 12 plastic blocks are instrumented. Three plastic blocks are instrumented for each of the four methods analyzed. An independent examiner grades the blocks on a scale of 0 to 4 (0 being least, 4 being most) for degree of zip and degree of transfer. Union Broach K-type files* are used in the hand method with preflaring and step-back, Endolift and Endo Angle. Medidentia (Hedstrom design)? plastic-headed files are used in the Giromatic. Thirteen plastic blocks are prepared with the three mechanized endodontic devices. With these blocks, speeds are varied during the preparations. In the human teeth phase, 20 extracted teeth with a moderate degree of root curvature are instrumented with the four methods of preparation. Five teeth are prepared for each method. Radiographs of each tooth are taken from two views: buccal lingual and mesial distal--before preparation. Working distance is determined by passing a No.
*Union Broach, 36-40 37th St.. Long Island City, N. Y. 11101. tKerr, Romulus, Mich. 48 174. $Endo-Vu, 2348 N. Lewis, Waukegan, Ill. 60085.
*Union Broach, 36-40 37th St., Long Island City, N.Y. lI101. TMicro Mega Export, 3 rue de la Mairie CH-1211 Geneve 6. Switzerland.
Fig. 6. Giromatic preparationof the curved canal in the plastic block.
420
Lehman and Gerstein
Oral April.
Surg IWI
Fig. 9. Effect of varied speeds on the Endolift preparation. A. Endolift preparation at slow speed: B. Endolift preparation at higher speeds.
Fig. 8. Endolift preparation of the curved canal in the plastic block.
10 or 15 file out the apex and then working 1 mm. short of this distance. The teeth are then filed until clean white shavings are produced. Measured amounts of tap water are used as irrigation material (0.5 C.C. for each tile size). When the canal is prepared to the proper size, a No. 15 file is passed out the apex to make sure the canal is patent. Renovist II* is used as a radiopaque medium. A 15 *E. R. Squibb & Sons,Inc., Princeton,N. J. 08540.
gauge needle attached to the dental suction apparatUS is placed over the apex of the tooth, the Renovist solution is injected in the occlusal opening, and the material is suctioned through the root canal system. A radiograph is made: two views are recorded as with the pretreatment radiographs. The canal form and preparation in the apical third are examined by an independent examiner and the degree of zip and degree of transfer are rated on the scale 0 to 4, as in the block study. RESULTS Plastic block phase
Hand instrumentation, using the step-back with preflaring technique, packs the least amount of debris and is the fastest of the methods used. In the block, hand instrumentation shows the least zipping (Fig. 5). Giromatic is the second fastest method of preparation. When run on slow speed, the Giromatic shows only slightly more zipping and transfer then the hand method (Fig. 6). The Giromatic is similar
Volume 53 Number 4
New mechanized endodontic device: Endoiift
42 1
Fig. 11. Effect of varied speedson the Union Broach Endo Angle. A, Union BroachEndo Angle preparationat slow speed;B, Union BroachEndo Angle preparation at higher speeds; arrow denotes gross elliptication.
Fig. 10. Union Broach Endo Angle preparation of the curved canal in a plastic block.
to the Endolift in this respect. At higher speeds a great deal of zipping and transfer is noted (Fig. 7). The Hedstrom files cut rapidly. Once marked elliptication or transfer starts it is difficult-if not impossible-to renegotiate the original canal, even with small instruments. The Endolift shows more zipping than the hand method but is similar to the Giromatic (Fig. 8). The Endolift shows less of a tendency to cut apically and its cutting efficiency is less than the Giromatic. The Endolift is more time-consuming to use than the hand method or the Giromatic. Best results are
obtained with a serial step-back technique with the Endolift run at slow speeds (Fig. 9). The Union Broach Endo Angle device is the most time-consuming to use. Test handle attachments are required, and the handles permit instrumentation of the canal only up to a size 40. The Endo Angle shows marked tendency toward zipping and transfer, with a great tendency to show an hour-glass effect on canal configuration (Fig. 10). Even when this device is run at slow speeds, a lack of uniform taper and noticeable zipping are apparent (Fig. 11). Extracted
human teeth phase
Hand instrumentation with the preflaring and step-back is the most rapid method and shows the best cutting efficiency. The least zipping and transfer occur in the hand instrumentation regimen (Fig. 12). Giromatic is the second fastest method of prepa-
422
Lehman and Gerstein
Oral Surg.
April. 19X?
Fig. 12. Hand tooth.
instrumentation
in
extracted
human
ration. The Giromatic shows more zipping and transfer than found in the hand and Endolift prepared teeth (Fig. 13). Clinically, tactile sensation is lacking. It is difficult to keep an apical stop and the instrument will cut too far apically. Even with great care and attention to the details or working length, it is possible to overinstrument the canal apically. The Endolift is more time-consuming to use than the aromatic or hand method and is not as efficient in cutting, but it does not appear to cut apically easily. It shows some tendency to pack more debris in the apical areas and out the apex. It zips and transfers more readily than the hand method (Fig. 14). The Union Broach Endo Angle is extremely time-consuming to use. More material is forced out
Fig. 13. Giromatic tooth.
instrumentation
in extracted human
the apex with the Endo Angle than with the other methods used. There is a marked increase in the amount of zipping and transfer with the use of the Endo Angle (Fig. 15). No tactile senseis noted with the Endo Angle. DISCUSSION
This is too subjective a study and involves too small a sample size for statistical analysis. The block and extracted human teeth are instrumented by a second-year endodontics resident (an operator with considerable endodontic skill). Careful attention is paid to working length to minimize possible deleterious effects of the method used to prepare the canals. At no time was there any attempt to try to perforate or zip.
Volume Number
New mechanized endodontic device: Endolift
53 4
Fig. 14. Kerr Endolift human tooth.
instrumentation
423
in extracted
Fig. 15. Union Broach Endo Angle instrumentation in extracted human tooth.
The operator was much more familiar with the use of hand instrumentation than with the automated devices. This factor should be considered in the evaluation of the time involved with each of the tested methods. At no time during the study was there any instrument breakage. Mechanical instruments do not break easily. Hand instrumentation with flies, with the use of step-back and preflaring, produces a better canal preparation. This finding supports the reports of Klayman and Brilliant” and Weine and associates.‘O When slow speed is used and care taken to keep the working length constant, the Giromatic and Endolift devices produce an acceptable canal preparation. All the mechanized devices are more time-
consuming to use in this operator’s hands. Working length is more difficult to maintain in the Endodontic devices and their over-all size appears to make them difficult to use in the posterior regions of the mouth. A mandibular second molar was instrumented on a patient by means of the Endolift device. The patient complained of the vibrations produced. At times the instrument would bind and lock until lifted out of the canal slightly. Clinically it appeared that this action could force material down the canal. The Endolift cuts best when the entire pulp chamber is flooded with sodium hypochlorite. The instrument appeared to follow the canal adequately, but in this operator’s hands it was very time-consuming. The over-all head and instrument size make it difficult to operate in the second molar area.
424
Oral Surg. April, 19X2
Lehman and Gerstein
CONCLUSION
1. Hand instrumentation with preflaring and step-back is better and safer than the mechanized devices tested. 2. When slow speed is used and care taken to keep working lengths constant, the Giromatic and Endohft devices produce an acceptable preparation, though less nearly ideal. 3. Over-all size of the mechanized devices make them difficult to the use in the posterior areas of the mouth. 4. It may be possible to develop a technique for the use of the Endolift and Giromatic in anterior teeth which will be a safe method to produce adequate root canal preparations. The authors thank Jeffrey F. Seipel for his technical assistanceand Dana Fuys for her assistancein preparing this study for publication. REFERENCES 1. Heuer, M. A.: The Biomechanics of Endodontic Therapy Dent. Clin. North Am. 13: 341-359, 1963. 2. Weine. F. S.: Endodontic Therapy. St. Louis, 1972. The C. V. Mosby Company, p. 191.
6.
I. 8.
9.
10.
Stewart. G. S.: Importance ofChemomechanica1 Preparatmn of the Root Canal, ORAL SURG. 8: 933-937. 1955. Auerbach. M. B.: Antibiotics vs. Instrumentation in Endodontics. N. Y. .I. Dent. 19: 255-288. 1953. Ingle, J. I.: Standardized Endodontic Technique Utilizing Newly Designed Instruments and Fillins Materials, ORAL SURG. 14: 83-91. 1961. Weine, F. S.. Kelly. R. F.. and Lio. P. J.: The Effect of Preparation on Ori$nal Canal Shape and on Apical Foramen Shane. J. Endod. 1: 255-262. 1975. Frank. A’. L.: An Evaluation of the Giromatic Endodontic Handpiece, ORAL SURG. 24: 419-421, 1967. Klayman, S. M., and Brilliant D. J.: A Comparison of the Efficacy of Serial Preparation Versus Giromatic Preparation J. Endod., 1: 334-337, 1975. O’Connell D. T.. and Brayton, S. M.: Evaluation of Root Canal Preparation With Two Automated Endodontic Handpieces, ORAL SURG. 29: 298-303, 1975. Weine, F. S., Kelly. R. F.. and Bray, K. E.: Effect of Preparation With Endodontic Handpieces on Original Canal Shape. J. Endod. 2: 298-303. 1976.
Reprint requests to: Dr. Harold Gerstein Marquette University School of Dentistry Department of Endodontic 604 N. 16th St. Milwaukee. Wis. 53233
UNIVERSITY
D. D.S., * and Harold Gerstein, B.S., D. D.S.,** Milwaukee, SCHOOL
Wis.
OF DENTISTRY
Four methods of canal preparation are tested: hand instrumentation with preflaring and step back, Giromatic, Union Broach Endo Angle, and the Kerr Endolift. The preparations are analyzed with plastic blocks and extracted human teeth. Hand instrumentation with preflaring and step-back is superior to and safer than the mechanized endodontic devices. With proper care and technique, some mechanized endodontic devices can produce adequate canal preparations.
N ext to proper diagnosis, the most important phase of endodontic treatment is proper canal
The opinions or assertions contained herein are those of the authors and are not to be construed as official or reflecting the views of the Department of the Navy. *Commander (DC) U. S. Navy, in civilian residency training and second year resident in Endodontics. **Professor and Chairman, Department of Endodontics.
endodontic devices. Frank’ and Klayman and Brilliants reported on the use of the Giromatic. O’Connell and BraytonY reported on the use of the Giromatic and W. and H. Endodontic Contra Angle. All the investigators concluded that hand instrumentation is superior to the mechanized instrumentation. The purpose of this study is to analyze a new mechanized endodontic instrument, the Endolift. In 1975 Weine, Kelly, and Lie” reported on the use of simulated canals in clear casting resin blocks. Similar blocks are used in this study to show the effect that canal preparation procedures have on the original canal shape. In this report we attempt to look at the character of the root canal preparation in the apical third (to note zipping or elliptication). The abilities of the instruments tested to negotiate tight canals, fracture potential, ledging, and perforation potential are
Giromatic handpiecewith Hedstromdesignfile.
Fig. 2. Union Broach Endo Angle handpiece with K fype file in test handle holder.
preparation.‘. 2 Proper biomechanical instrumentation of the root canal is the primary method of eliminating toxic products in the canaL3,4 The root canal must be properly shaped and cleansed to be properly 0bturated.j When the debris of the root canal system has been sufficiently reduced and an adequate area provided for a filling made with the preparation, a variety of filling techniques may be utilized to obtain a successful result.” Previous studies have been made on mechanized
Fig.
1.
417
418
Lehman and Gerstein
reviewed. Attention is also paid to the time involved with the various preparations and the speed at which to use the mechanized devices. Findings, with a clinical case in which the Endolift was used, are also presented. METHODS
AND MATERIALS
Four methods of canal preparation in this study: (1) hand instrumentation ing and step-back, (2) Giromatic* Flg. 4. Endo-Vu mented.
Model
001 plastic
block
uninstru-
are analyzed with preflar(instrument
*Micro Mega Export. 3 rue de la Mairie CH-1211 Geneve 6. Switzerland.
Volume 53 Number 4
New mechanized endodontic device: Endolift
419
Fig. 7. Effectof varied speedson the Giromaticpreparation. A, Giromatic preparation slow speed;B, giromatic preparation at higher speeds; arrow denotes neck of “hour-glasseffect” type of preparation.
designed to rotate a quarter turn in alternate directions’-Fig. I), (3) Union Broach Endo Angle* (designed to rotate alternate quarter-turn movement continuous speed to 3,000 r.p.m.-Fig. 2) and (4) Kerr Endolift-1 (up-and-down motion with a slight turning motion-Fig. 3). The study is divided into two phases: a plastic block phase and an extracted human teeth phase. Endo-Vu model 001x curved plastic blocks are
used (Fig. 4). In the first phase of the block study, 12 plastic blocks are instrumented. Three plastic blocks are instrumented for each of the four methods analyzed. An independent examiner grades the blocks on a scale of 0 to 4 (0 being least, 4 being most) for degree of zip and degree of transfer. Union Broach K-type files* are used in the hand method with preflaring and step-back, Endolift and Endo Angle. Medidentia (Hedstrom design)? plastic-headed files are used in the Giromatic. Thirteen plastic blocks are prepared with the three mechanized endodontic devices. With these blocks, speeds are varied during the preparations. In the human teeth phase, 20 extracted teeth with a moderate degree of root curvature are instrumented with the four methods of preparation. Five teeth are prepared for each method. Radiographs of each tooth are taken from two views: buccal lingual and mesial distal--before preparation. Working distance is determined by passing a No.
*Union Broach, 36-40 37th St.. Long Island City, N. Y. 11101. tKerr, Romulus, Mich. 48 174. $Endo-Vu, 2348 N. Lewis, Waukegan, Ill. 60085.
*Union Broach, 36-40 37th St., Long Island City, N.Y. lI101. TMicro Mega Export, 3 rue de la Mairie CH-1211 Geneve 6. Switzerland.
Fig. 6. Giromatic preparationof the curved canal in the plastic block.
420
Lehman and Gerstein
Oral April.
Surg IWI
Fig. 9. Effect of varied speeds on the Endolift preparation. A. Endolift preparation at slow speed: B. Endolift preparation at higher speeds.
Fig. 8. Endolift preparation of the curved canal in the plastic block.
10 or 15 file out the apex and then working 1 mm. short of this distance. The teeth are then filed until clean white shavings are produced. Measured amounts of tap water are used as irrigation material (0.5 C.C. for each tile size). When the canal is prepared to the proper size, a No. 15 file is passed out the apex to make sure the canal is patent. Renovist II* is used as a radiopaque medium. A 15 *E. R. Squibb & Sons,Inc., Princeton,N. J. 08540.
gauge needle attached to the dental suction apparatUS is placed over the apex of the tooth, the Renovist solution is injected in the occlusal opening, and the material is suctioned through the root canal system. A radiograph is made: two views are recorded as with the pretreatment radiographs. The canal form and preparation in the apical third are examined by an independent examiner and the degree of zip and degree of transfer are rated on the scale 0 to 4, as in the block study. RESULTS Plastic block phase
Hand instrumentation, using the step-back with preflaring technique, packs the least amount of debris and is the fastest of the methods used. In the block, hand instrumentation shows the least zipping (Fig. 5). Giromatic is the second fastest method of preparation. When run on slow speed, the Giromatic shows only slightly more zipping and transfer then the hand method (Fig. 6). The Giromatic is similar
Volume 53 Number 4
New mechanized endodontic device: Endoiift
42 1
Fig. 11. Effect of varied speedson the Union Broach Endo Angle. A, Union BroachEndo Angle preparationat slow speed;B, Union BroachEndo Angle preparation at higher speeds; arrow denotes gross elliptication.
Fig. 10. Union Broach Endo Angle preparation of the curved canal in a plastic block.
to the Endolift in this respect. At higher speeds a great deal of zipping and transfer is noted (Fig. 7). The Hedstrom files cut rapidly. Once marked elliptication or transfer starts it is difficult-if not impossible-to renegotiate the original canal, even with small instruments. The Endolift shows more zipping than the hand method but is similar to the Giromatic (Fig. 8). The Endolift shows less of a tendency to cut apically and its cutting efficiency is less than the Giromatic. The Endolift is more time-consuming to use than the hand method or the Giromatic. Best results are
obtained with a serial step-back technique with the Endolift run at slow speeds (Fig. 9). The Union Broach Endo Angle device is the most time-consuming to use. Test handle attachments are required, and the handles permit instrumentation of the canal only up to a size 40. The Endo Angle shows marked tendency toward zipping and transfer, with a great tendency to show an hour-glass effect on canal configuration (Fig. 10). Even when this device is run at slow speeds, a lack of uniform taper and noticeable zipping are apparent (Fig. 11). Extracted
human teeth phase
Hand instrumentation with the preflaring and step-back is the most rapid method and shows the best cutting efficiency. The least zipping and transfer occur in the hand instrumentation regimen (Fig. 12). Giromatic is the second fastest method of prepa-
422
Lehman and Gerstein
Oral Surg.
April. 19X?
Fig. 12. Hand tooth.
instrumentation
in
extracted
human
ration. The Giromatic shows more zipping and transfer than found in the hand and Endolift prepared teeth (Fig. 13). Clinically, tactile sensation is lacking. It is difficult to keep an apical stop and the instrument will cut too far apically. Even with great care and attention to the details or working length, it is possible to overinstrument the canal apically. The Endolift is more time-consuming to use than the aromatic or hand method and is not as efficient in cutting, but it does not appear to cut apically easily. It shows some tendency to pack more debris in the apical areas and out the apex. It zips and transfers more readily than the hand method (Fig. 14). The Union Broach Endo Angle is extremely time-consuming to use. More material is forced out
Fig. 13. Giromatic tooth.
instrumentation
in extracted human
the apex with the Endo Angle than with the other methods used. There is a marked increase in the amount of zipping and transfer with the use of the Endo Angle (Fig. 15). No tactile senseis noted with the Endo Angle. DISCUSSION
This is too subjective a study and involves too small a sample size for statistical analysis. The block and extracted human teeth are instrumented by a second-year endodontics resident (an operator with considerable endodontic skill). Careful attention is paid to working length to minimize possible deleterious effects of the method used to prepare the canals. At no time was there any attempt to try to perforate or zip.
Volume Number
New mechanized endodontic device: Endolift
53 4
Fig. 14. Kerr Endolift human tooth.
instrumentation
423
in extracted
Fig. 15. Union Broach Endo Angle instrumentation in extracted human tooth.
The operator was much more familiar with the use of hand instrumentation than with the automated devices. This factor should be considered in the evaluation of the time involved with each of the tested methods. At no time during the study was there any instrument breakage. Mechanical instruments do not break easily. Hand instrumentation with flies, with the use of step-back and preflaring, produces a better canal preparation. This finding supports the reports of Klayman and Brilliant” and Weine and associates.‘O When slow speed is used and care taken to keep the working length constant, the Giromatic and Endolift devices produce an acceptable canal preparation. All the mechanized devices are more time-
consuming to use in this operator’s hands. Working length is more difficult to maintain in the Endodontic devices and their over-all size appears to make them difficult to use in the posterior regions of the mouth. A mandibular second molar was instrumented on a patient by means of the Endolift device. The patient complained of the vibrations produced. At times the instrument would bind and lock until lifted out of the canal slightly. Clinically it appeared that this action could force material down the canal. The Endolift cuts best when the entire pulp chamber is flooded with sodium hypochlorite. The instrument appeared to follow the canal adequately, but in this operator’s hands it was very time-consuming. The over-all head and instrument size make it difficult to operate in the second molar area.
424
Oral Surg. April, 19X2
Lehman and Gerstein
CONCLUSION
1. Hand instrumentation with preflaring and step-back is better and safer than the mechanized devices tested. 2. When slow speed is used and care taken to keep working lengths constant, the Giromatic and Endohft devices produce an acceptable preparation, though less nearly ideal. 3. Over-all size of the mechanized devices make them difficult to the use in the posterior areas of the mouth. 4. It may be possible to develop a technique for the use of the Endolift and Giromatic in anterior teeth which will be a safe method to produce adequate root canal preparations. The authors thank Jeffrey F. Seipel for his technical assistanceand Dana Fuys for her assistancein preparing this study for publication. REFERENCES 1. Heuer, M. A.: The Biomechanics of Endodontic Therapy Dent. Clin. North Am. 13: 341-359, 1963. 2. Weine. F. S.: Endodontic Therapy. St. Louis, 1972. The C. V. Mosby Company, p. 191.
6.
I. 8.
9.
10.
Stewart. G. S.: Importance ofChemomechanica1 Preparatmn of the Root Canal, ORAL SURG. 8: 933-937. 1955. Auerbach. M. B.: Antibiotics vs. Instrumentation in Endodontics. N. Y. .I. Dent. 19: 255-288. 1953. Ingle, J. I.: Standardized Endodontic Technique Utilizing Newly Designed Instruments and Fillins Materials, ORAL SURG. 14: 83-91. 1961. Weine, F. S.. Kelly. R. F.. and Lio. P. J.: The Effect of Preparation on Ori$nal Canal Shape and on Apical Foramen Shane. J. Endod. 1: 255-262. 1975. Frank. A’. L.: An Evaluation of the Giromatic Endodontic Handpiece, ORAL SURG. 24: 419-421, 1967. Klayman, S. M., and Brilliant D. J.: A Comparison of the Efficacy of Serial Preparation Versus Giromatic Preparation J. Endod., 1: 334-337, 1975. O’Connell D. T.. and Brayton, S. M.: Evaluation of Root Canal Preparation With Two Automated Endodontic Handpieces, ORAL SURG. 29: 298-303, 1975. Weine, F. S., Kelly. R. F.. and Bray, K. E.: Effect of Preparation With Endodontic Handpieces on Original Canal Shape. J. Endod. 2: 298-303. 1976.
Reprint requests to: Dr. Harold Gerstein Marquette University School of Dentistry Department of Endodontic 604 N. 16th St. Milwaukee. Wis. 53233