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Ultrasonic compared with hand instrumentation: A scanning electron microscope study
0099-2399/8811409-0435/$02,00/0 JOURNAL OF ENDODONTICS Copyright 9 1988 by The American Association of Endodontists
Printed in U.S.A.
VOL. 14, NO, 9, SEPTEMBER1988
Ultrasonic Compared with Hand Instrumentation: A Scanning Electron Microscope Study Mark C. Baker, DDS, Shahid H. Ashrafi, PhD, PhO, DSc, Joseph E. Van Cura, DDS, and Nijole A. Remeikis, DDS
Scanning electron micrographs were used to compare the effectiveness of two methods of cleansing, shaping, and enlarging root canals of human teeth. Eleven extracted maxillary central incisors were instrumented by ultrasonically activated K files and diamond files with a constant high volume of 2.625% NaOCI irrigation. Another 11 maxillary central incisors were hand instrumented with conventional endodontic K files with a high volume of 2.625% NaOCI irrigation. Scanning electron micrographic photographs of the prepared canal walls were made at three levels in the root and were evaluated both quantitatively and qualitatively. On the basis of remaining debris, presence of a smear layer, and patency of dentinal tubules, no significant difference between the two methods was found at the apical or coronal level of the root canal. At the miu-level hand instrumentation produced significantly cleaner canal walls. A smear layer remained on the canal wall after both methods.
A new device for cleansing and shaping root canals has been recently introduced utilizing ultrasonically vibrating stainless steel and diamond files which plane the root canal walls while the entire root canal system is flushed with a high volume of ultrasonically "activated" irrigating solution. The inventors of this device, called the ultrasonic endosonic synergistic system (Caulk-Dentsply Cavi-Endo machine; Dentsply, Milford, DE) performed a number of preliminary tests before releasing it for general use. They found postoperative pain to be no greater than with conventional hand filing techniques (1). They noted the device warmed the irrigating solution (2.6% sodium hypochlorite) in the root canal from room temperature to body temperature. The warmed solution was just as effective at dissolving collagen as room temperature irrigating solution of double the concentration (2). Warmed irrigating solution also killed viable bacteria more rapidly than did the room temperature solution (3). Ultrasonically activated K-type files removed root canal dentin more rapidly than hand-manipulated files (4), and diamond files removed dentin more rapidly than K-type files (5). The ultrasonic device caused less extrusion of root canal material beyond the tooth apex than conventional hand filing (6). The effectiveness of ultrasonic instrumentation in removing pulpal remnants and debris from the root canal space has also been tested. Cunningham et al. (7) compared the new technique with conventional hand filing using the light microscope to analyze transverse sections of the root for the presence of remaining debris. Although ultrasonic instrumentation proved to be superior to hand instrumentation, many of the variables that relate to canal preparation were not mentioned in this study. Was a flared hand-filed technique used? How much irrigation was used between each file size? To what depth did the irrigating needle penetrate? Only 3 min were allowed for instrumentation of the teeth which may have been insufficient for adequate hand preparation. Similar questions can be raised about a study by Cunningham and Martin (8) who used the scanning electron microscope to compare hand instrumentation with ultrasonic instrumentation. Using the scanning electrom microscope, Cymerman et al. (9) also evaluated the two techniques of canal preparation. As opposed to the previous studies, the conditions of this study were noted in detail. They found no difference in canal cleanliness between the two techniques. Unfortunately they did not have access to the ultrasonic device introduced by Cunningham and Martin but constructed a similar machine. They allowed 2 min for ultrasonic instrumentation but an
Endodontic texts identify three factors necessary for successful root canal therapy. The first, cleansing and shaping, removes remaining pulp tissue, necrotic debris, bacteria and their products, and alters the shape of the canal to receive the final filling material. The second, microbial control, is achieved primarily by cleansing and shaping the canal. Bacteria and their necrotic substrate are mechanically removed with endodontic instruments and flushed out with antimicrobial irrigating solutions. The final factor, obturation and sealing of the root canal space, is achieved by the filling material and sealer. The three factors are equally important and research continues to be done to improve their effectiveness. In an effort to improve the effectiveness of the cleansing and shaping phase of root canal therapy, many aspects of canal debridement have been examined. Cross-sectional shape of files has been variously altered to develop the most effective cutting instruments. Root canal preparation by engine-driven instruments has been compared with preparation by hand instruments. Irrigating solutions used as adjuncts to mechanical preparation have been extensively tested. 435
436
Baker et al.
Journal of Endodontic4
unspecified amount of time was allowed for hand preparation. Ultrasonic preparation was made completely with a #30 K file while the commercially available ultrasonic instructions call for sequential filing and flaring with stainless steel and diamond files. These deviations from the recommended protocol for using the ultrasonic device may have had a significant bearing on their findings. This study compared the effectiveness of the ultrasonic endosonic synergistic system with a conventional hand-filed and flared technique. The ultrasonic device was used according to the manufacturer's directions and the experimental procedure was noted in detail. Sufficient time was allowed in both techniques to thoroughly instrument the canals. Every effort was made to do the best possible job of cleansing and shaping the root canals with each of the two techniques. PURPOSE Preliminary investigations have shown that ultrasonic root canal instrumentation may be superior to hand instrumentation in the removal of debris and smear layer from root canals of human teeth (7, 8). The purpose of this study was to evaluate the cleanliness of dentin walls of root canals prepared by hand instrumentation and by ultrasonic instrumentation. Scanning electron microscopy was utilized to examine the root canal walls of teeth prepared by these two methods. MATERIALS AND METHODS Twenty-four recently extracted maxillary central incisors were divided into two experimental groups of l I teeth each plus two uninstrumented but irrigated control teeth. All teeth were stored in normal saline solution throughout the experiment. Standard endodontic access preparations were made in all crowns. Working lengths were established 1 m m short of the foramina by visually identifying a # l0 or #15 file at the foramina and subtracting I mm. Sodium hypochlorite (2.625%) irrigant was used in all cases. Following instrumentation the canals were dried with sterile paper points, dry cotton pellets were placed in the pulp chambers, and the access openings were sealed with Cavit (Premier, Norristown, PA). Root canals of hand instrumented teeth were enlarged using standard K files in a normal filing, rasping, and one-quarter turn pull motion (_10). Canals were hand filed wet and flushed with 3 ml of irrigant after each file size. Irrigant was introduced into the canals through a 25-gauge irrigation needle placed apicaUy as far as possible without binding. A final post instrumentation flush o f 6 ml ofirrigant was made. All handfiled teeth were enlarged to a size dependent upon the original canal (at least three sizes larger than the first instrument that bound at the apex) and flared four additional sizes. The 11 ultrasonically prepared teeth were instrumented in accordance with the manufacturer's instructions using a constant 27 ml per rain irrigant flow and a power setting o f 9 on a scale of 10. When necessary as in the case of narrow calcified canals the teeth were first hand instrumented to a # 15 file. The teeth were then ultrasonically instrumented sequentially with #15, 20, and 25 stainless steel files to working length and subsequently flared with ultrasonically energized safe-ended #25, 35, and 45 diamond files manufactured specifically for
use with this machine. During actual canal enlargement, the energized files were rested gently against the canal walls and moved in an up and down and circumferential motion. Irrigant flow rate was monitored by measuring the irrigant volume collected after 1 min of machine operation. The flow rate was checked periodically during ultrasonic instrumentation of the teeth and the actual volume of irrigant used in each tooth recorded. The uninstrumented control teeth had standard coronal accesses prepared. They were irrigated with 12 ml of solution, dried with paper points, and sealed in the manner previously described.
Preparation for Scanning Electron Microscope The 24 specimens were dehydrated in a series of graded concentrations of ethyl alcohol. Crowns were removed at the cementoenameljunction and the roots were grooved vertically on their labial and lingual surfaces with a diamond separating disk and cracked longitudinally with a mallet and chisel. The pieces were dried for 48 h in a 46"C oven and one-half of each tooth was chosen for mounting. Because the teeth did not always split into two equal halves the prepared canal wall was usually more easily visualized in one of the halves. That half was selected for mounting. Mounted specimens were coated with a 20-nm thick film of gold and viewed with a scanning electron microscope at magnifications of • to x2,000. Scanning micrographs were made on Polaroid Type 55 Land film (Polaroid Corp., Cambridge, MA).
Analysis Scanning micrographs taken at x500 at three different levels (apical, middle, and incisal) were examined individually by three endodontists experienced in scanning electron microscope evaluation. Micrographs were rated on a scale of 1 to 4 for overall cleanliness, presence of debris, and presence of open and clean dentinal tubules (1 = least debris or cleanest, 4 = most debris or dirtiest). Evaluators were not aware of which group any sample was taken from. Scores were averaged to obtain an overall cleanliness rating for each of the three levels for both experimental groups. Interrater reliability was found to be high with a l-digit difference 25% of the timt and a 2-digit difference only 2% of the time. Scores weft TAaLE 1. Irrigant volume per tooth (milliliter), 2.625% NaOQ Tooth
Ultrasonic instrumentation (ml)
Hand instrumentation (ml)
1 2 3 4 5 6 7 8 9 10 11
178 165 115 140 119 120 145 158 125 141 150
30 36 39 33 36 33 36 36 36 33 36
Average
141
35
Vol. 14, No. 9, September 1988
Ultrasonic versus Hand Instrumentation
statistically evaluated using unpaired t tests to determine whether a quantitative difference in cleanliness existed between the hand instrumented and ultrasonically instrumented teeth at any of the three levels. Scanning micrographs at magnifications ranging from x20 to x2,000 were qualitatively evaluated for patency ofdentinal tubules, presence of debris, and presence of a smear layer. Finally, a statement was made concerning the overall effectiveness of instrumentation in each experimental group using both the qualitative and quantitative data.
437
amounts of hard tissue debris were present at all levels (Figs. 1 and 2). The enlarging instrument left some walls untouched (Fig. 3). Untouched walls were irregular and bumpy with no smear layer (Fig. 4). Untouched walls were covered with varying amounts of hard tissue debris and sometimes contained open dentinal tubules. H A N D I N S T R U M E N T E D TEETH Instrumented walls were generally very smooth (Figs. 5 and 6). Slightly less debris was found at the middle level.
RESULTS The volume of irrigant used in each tooth was recorded (Table 1).
ULTRASONICALLY INSTRUMENTED TEETH Walls were rough, especially at the middle and occlusal levels (Fig. 7). Superficial vertical scratches, nicks, and gashes
Quantitative Analysis Differences between ultrasonic and hand instrumentation were not significant at the apical and coronal levels. At the mid-root level hand filing was significantly better (Table 2).
Qualitative Descriptive Analysis FEATURES C O M M O N TO BOTH EXPERIMENTAL GROUPS Instrumented dentinal walls at all levels were covered with a smear layer which obscured the dentinal tubules. Various TABLE 2. Quantitative rating of canal cleanliness (1 = best, 4 = worst)
Method Level
Apical Level
Middle Level
Coronal Level
Hand Ultrasonic
2.33 2.55
2.09 2.70
2.18 2.55
~Middle level significant at p < 0.01.
FiG1. Hand-filed canal wall, apical third of root. Smear layer obscures dentinal tubules. Much superficial inorganic debris present (dentin chips) (original magnification x500).
FIG 2. Ultrasonically filed canal wall, apical third of root. Similar to Fig. 1 with dentinal tubules obscured by the smear layer and much superficial inorganic debris (original magnification x500).
F~a 3. Hand-filed canal wall, incisal third of root. Arrows indicate part of the canal wall not actually touched by the flies (original magnification x20).
438
Baker et al.
Journal of Endodontics
' ~ ? ~ K_
7"= ~
F~G 4. Ultrasonically filed canal wall, middle third of root. The files did not touch this portion of the canal wall but soft tissue pulpal remnants and predentin have been removed by the sodium hypochlorite irrigation. Calcified dentin with scattered superficial debris remains. Compare this with Fig. 10 in which organic pulpal remnants and predentin remain covering the rough inorganic walls of the canal. Untouched canal walls of hand-instrumented teeth appear the same (original ~agnification x500).
..
".~
'~/',,~,:
". ~
'
~
~
~'~=, ,~ -~,~ ..~
9
9
_ ,. ".?
FIG 6. Hand-filed canal wall, incisal third of root. A smear layer obscures the dentinal tubules. Arrows indicate residual inorganic debris (dentin chips) (original magnification x200).
FIG 7. Ultrasonically filed canal wall, incisal third of root. Note vertical scratches and numerous small nicks (original magnification x20).
DISCUSSION FUG5. Hand-filed canal wall, incisal third of root. Wall appears smooth with a small amount of scattered inorganic debris. Crack probably occurred during splitting of the root (original magnification x20).
could be noticed at lower magnification and at high magnification patches of open dentinal tubules were found in these irregularities (Fig. 8). Slightly more debris was found at the middle level. U N I N S T R U M E N T E D TEETH (CONTROLS) Walls appeared to be uniformly irregular and bumpy with overlying web-like structures (Figs. 9 and 10). Dentin debris was not present and tubules were not visible.
Scanning micrographs and quantitative results indicate a surprisingly large a m o u n t of hard tissue debris remaining at all levels of the root canals despite the high volume of irrigating solution used (Figs. 1, 2, and 8). Total irrigant volume ranged from 119 to 178 ml for ultrasonically prepared teeth and from 30 to 39 ml for the hand-instrumented teeth. The outside diameter of the irrigating needle (<0.55 mm) clearly allowed the irrigant to be delivered to the apical third in the hand-instrumented teeth. It may have been this apical delivery of irrigating solution which resulted in significantly less hard tissue debris at the mid-root level in the hand-instrumented teeth. Even though ultrasonic preparation delivered at least three times as much irrigation volume, the solution flowed down the outside o f the file and may not have been readily
Vol. 14, No. 9, September 1988
FIG 8. Ultrasonically filed canal wall, incisa! third of root. A smear layer covers most of the wall obscuring the dentinal tubules. Numerous nicks are present in the smear layer. Arrows indicate a patch o f open dentinal tubules at the base o f one of the nicks. A moderate amount of superficial inorganic debris is present (original magnification x200).
Ultrasonic versus Hand Instrumentation
439
FIG 10. Uninstrumented canal wall, middle third o f root. Same tooth as in Fig. 9. Wall is covered with web-like soft tissue remains of pulp and predentin (original magnification x500).
would be a breakthrough in the biomechanical instrumentation phase of root canal therapy. Ultrasonic instrumentation has been shown to be effective in these areas (7). In this study both methods of irrigation were effective at removing soft tissue remnants from the uninstrumented canal walls (Fig. 4). In some instances open dentinal tubules were visible. In others, moderate amounts of dentin debris were noted. But compared with the canal walls of the two uninstrumented teeth (Fig. 10), organic soft tissue remnants were effectively removed from the untouched walls by both methods of cleansing. CONCLUSIONS The results of the study indicate that ultrasonic instrumentation is not superior to conventional hand filing and flaring in canal debridement. At mid-level of the root, hand filing was significantly more effective.
FiG 9. Uninstrumented canal wall, middle third of root (original magnification x20).
interchanged at the apex. Martin (11) claims that the ultrasonic motion of the file causes stirring and mixing of the solution within the tooth and that the irrigant flows down the file to the apex even in curved canals. This has not been experimentally verified. Even in the straight canals of maxillary central incisors, some walls were left untouched by enlarging instruments (Fig. 3). This was observed and allowed a comparison to be made between ultrasonically "activated" irrigation and normal irrigation with regard to removal of organic and inorganic debris from these untouched areas. The ability to effectively remove pulpal remnants, bacteria, and other debris from these areas
This study was supported in part by research funding from the AAE Endowment and Memorial Foundation and the Edward C. Wach Research Fund, University of Illinois School of Dentistry. This article is from a thesis submitted by Dr. Baker in partial fulfillment of the requirements for a certificate in endodontics at the University of Illinois at Chicago, College of Dentistry. Dr. Baker is assistant professor, Department of Endodontics, University of Illinois at Chicago, Chicago, IL. Dr. Ashrafi is associate professor, Oral Pathology, Histology, and Pathology Departments, University of Illinois at Chicago. Dr. Van Cura is professor and director, Postdoctoral Endodontics, University of Illinois at Chicago. Dr. Remeikis is professor and head, Endodontics Department, University of Illinois at Chicago. Address requests for reprints to Dr. Mark C. Baker, Department of Endodontics, College of Dentistry, University of Illinois at Chicago, 801 South Paulina Street, Chicago, IL 60612.
References 1. Martin H, Cunningham WT. An evaluation of postoperative pain incidence following endosonic and conventional root canal therapy. Oral Surg 1982;54:74-6. 2. Cunningham WT, Balekjian AY. Effect of temperature on collagen dis-
440
Baker et al.
solving ability of sodium hypochlorite endodontic irrigant. Oral Surg 1980;49:175-7. 3. Cunningham w r , Joseph SW. Effect of temperature on the bactericidal action of sodium hypochlorite endodontic irngant. Oral Surg 1980;50:569-71. 4. Martin H, Cunningham WT, Norris JP, Cotton WR. Ultrasonic versus hand filing of dentin: a quantitative study. Oral Surg 1980;49:79-81. 5. Martin H, Cunningham WT, Norris JP. A quantitative comparison of the ability of diamond and K-type files to remove dentin. Oral Surg 1980;50:5668. 6. Martin H, Gunningham WT. The effect of endosonic and hand manipulation on the amount of root canal rnaterial extruded. Oral Surg 1982;53:6113. 7. Cunningham WT, Martin H, Forrest WR. Evaluation of root canal debride-
Joumal of Endodontics ment by the endosonic ultrasonic synergistic system. Oral Surg 1982;53:401_ 4. 8. Cunningham WT, Martin H. A scanning electron microscope evaluation of root canal debridement with the ultrasonic synergistic system. Oral Surg 1982;53:527-31. 9. Cymerman JJ, Jerome LA, Moodnik RM. A scanning electron microscope study comparing the efficacy of hand instrumentation with ultrasonic instrumentation of the root canal. J Endodon 1983;9:327-31. 10. Walton RG. Histologic evaluation of different methods of enlarging the pulp canal space. J Endodon 1976;2:304-11. 11. Martin H. American Association of Endodontists tape recording of ultrasonic endodontic presentation at AAE Meeting in Hollywood, FL, April 1983.
Printed in U.S.A.
VOL. 14, NO, 9, SEPTEMBER1988
Ultrasonic Compared with Hand Instrumentation: A Scanning Electron Microscope Study Mark C. Baker, DDS, Shahid H. Ashrafi, PhD, PhO, DSc, Joseph E. Van Cura, DDS, and Nijole A. Remeikis, DDS
Scanning electron micrographs were used to compare the effectiveness of two methods of cleansing, shaping, and enlarging root canals of human teeth. Eleven extracted maxillary central incisors were instrumented by ultrasonically activated K files and diamond files with a constant high volume of 2.625% NaOCI irrigation. Another 11 maxillary central incisors were hand instrumented with conventional endodontic K files with a high volume of 2.625% NaOCI irrigation. Scanning electron micrographic photographs of the prepared canal walls were made at three levels in the root and were evaluated both quantitatively and qualitatively. On the basis of remaining debris, presence of a smear layer, and patency of dentinal tubules, no significant difference between the two methods was found at the apical or coronal level of the root canal. At the miu-level hand instrumentation produced significantly cleaner canal walls. A smear layer remained on the canal wall after both methods.
A new device for cleansing and shaping root canals has been recently introduced utilizing ultrasonically vibrating stainless steel and diamond files which plane the root canal walls while the entire root canal system is flushed with a high volume of ultrasonically "activated" irrigating solution. The inventors of this device, called the ultrasonic endosonic synergistic system (Caulk-Dentsply Cavi-Endo machine; Dentsply, Milford, DE) performed a number of preliminary tests before releasing it for general use. They found postoperative pain to be no greater than with conventional hand filing techniques (1). They noted the device warmed the irrigating solution (2.6% sodium hypochlorite) in the root canal from room temperature to body temperature. The warmed solution was just as effective at dissolving collagen as room temperature irrigating solution of double the concentration (2). Warmed irrigating solution also killed viable bacteria more rapidly than did the room temperature solution (3). Ultrasonically activated K-type files removed root canal dentin more rapidly than hand-manipulated files (4), and diamond files removed dentin more rapidly than K-type files (5). The ultrasonic device caused less extrusion of root canal material beyond the tooth apex than conventional hand filing (6). The effectiveness of ultrasonic instrumentation in removing pulpal remnants and debris from the root canal space has also been tested. Cunningham et al. (7) compared the new technique with conventional hand filing using the light microscope to analyze transverse sections of the root for the presence of remaining debris. Although ultrasonic instrumentation proved to be superior to hand instrumentation, many of the variables that relate to canal preparation were not mentioned in this study. Was a flared hand-filed technique used? How much irrigation was used between each file size? To what depth did the irrigating needle penetrate? Only 3 min were allowed for instrumentation of the teeth which may have been insufficient for adequate hand preparation. Similar questions can be raised about a study by Cunningham and Martin (8) who used the scanning electron microscope to compare hand instrumentation with ultrasonic instrumentation. Using the scanning electrom microscope, Cymerman et al. (9) also evaluated the two techniques of canal preparation. As opposed to the previous studies, the conditions of this study were noted in detail. They found no difference in canal cleanliness between the two techniques. Unfortunately they did not have access to the ultrasonic device introduced by Cunningham and Martin but constructed a similar machine. They allowed 2 min for ultrasonic instrumentation but an
Endodontic texts identify three factors necessary for successful root canal therapy. The first, cleansing and shaping, removes remaining pulp tissue, necrotic debris, bacteria and their products, and alters the shape of the canal to receive the final filling material. The second, microbial control, is achieved primarily by cleansing and shaping the canal. Bacteria and their necrotic substrate are mechanically removed with endodontic instruments and flushed out with antimicrobial irrigating solutions. The final factor, obturation and sealing of the root canal space, is achieved by the filling material and sealer. The three factors are equally important and research continues to be done to improve their effectiveness. In an effort to improve the effectiveness of the cleansing and shaping phase of root canal therapy, many aspects of canal debridement have been examined. Cross-sectional shape of files has been variously altered to develop the most effective cutting instruments. Root canal preparation by engine-driven instruments has been compared with preparation by hand instruments. Irrigating solutions used as adjuncts to mechanical preparation have been extensively tested. 435
436
Baker et al.
Journal of Endodontic4
unspecified amount of time was allowed for hand preparation. Ultrasonic preparation was made completely with a #30 K file while the commercially available ultrasonic instructions call for sequential filing and flaring with stainless steel and diamond files. These deviations from the recommended protocol for using the ultrasonic device may have had a significant bearing on their findings. This study compared the effectiveness of the ultrasonic endosonic synergistic system with a conventional hand-filed and flared technique. The ultrasonic device was used according to the manufacturer's directions and the experimental procedure was noted in detail. Sufficient time was allowed in both techniques to thoroughly instrument the canals. Every effort was made to do the best possible job of cleansing and shaping the root canals with each of the two techniques. PURPOSE Preliminary investigations have shown that ultrasonic root canal instrumentation may be superior to hand instrumentation in the removal of debris and smear layer from root canals of human teeth (7, 8). The purpose of this study was to evaluate the cleanliness of dentin walls of root canals prepared by hand instrumentation and by ultrasonic instrumentation. Scanning electron microscopy was utilized to examine the root canal walls of teeth prepared by these two methods. MATERIALS AND METHODS Twenty-four recently extracted maxillary central incisors were divided into two experimental groups of l I teeth each plus two uninstrumented but irrigated control teeth. All teeth were stored in normal saline solution throughout the experiment. Standard endodontic access preparations were made in all crowns. Working lengths were established 1 m m short of the foramina by visually identifying a # l0 or #15 file at the foramina and subtracting I mm. Sodium hypochlorite (2.625%) irrigant was used in all cases. Following instrumentation the canals were dried with sterile paper points, dry cotton pellets were placed in the pulp chambers, and the access openings were sealed with Cavit (Premier, Norristown, PA). Root canals of hand instrumented teeth were enlarged using standard K files in a normal filing, rasping, and one-quarter turn pull motion (_10). Canals were hand filed wet and flushed with 3 ml of irrigant after each file size. Irrigant was introduced into the canals through a 25-gauge irrigation needle placed apicaUy as far as possible without binding. A final post instrumentation flush o f 6 ml ofirrigant was made. All handfiled teeth were enlarged to a size dependent upon the original canal (at least three sizes larger than the first instrument that bound at the apex) and flared four additional sizes. The 11 ultrasonically prepared teeth were instrumented in accordance with the manufacturer's instructions using a constant 27 ml per rain irrigant flow and a power setting o f 9 on a scale of 10. When necessary as in the case of narrow calcified canals the teeth were first hand instrumented to a # 15 file. The teeth were then ultrasonically instrumented sequentially with #15, 20, and 25 stainless steel files to working length and subsequently flared with ultrasonically energized safe-ended #25, 35, and 45 diamond files manufactured specifically for
use with this machine. During actual canal enlargement, the energized files were rested gently against the canal walls and moved in an up and down and circumferential motion. Irrigant flow rate was monitored by measuring the irrigant volume collected after 1 min of machine operation. The flow rate was checked periodically during ultrasonic instrumentation of the teeth and the actual volume of irrigant used in each tooth recorded. The uninstrumented control teeth had standard coronal accesses prepared. They were irrigated with 12 ml of solution, dried with paper points, and sealed in the manner previously described.
Preparation for Scanning Electron Microscope The 24 specimens were dehydrated in a series of graded concentrations of ethyl alcohol. Crowns were removed at the cementoenameljunction and the roots were grooved vertically on their labial and lingual surfaces with a diamond separating disk and cracked longitudinally with a mallet and chisel. The pieces were dried for 48 h in a 46"C oven and one-half of each tooth was chosen for mounting. Because the teeth did not always split into two equal halves the prepared canal wall was usually more easily visualized in one of the halves. That half was selected for mounting. Mounted specimens were coated with a 20-nm thick film of gold and viewed with a scanning electron microscope at magnifications of • to x2,000. Scanning micrographs were made on Polaroid Type 55 Land film (Polaroid Corp., Cambridge, MA).
Analysis Scanning micrographs taken at x500 at three different levels (apical, middle, and incisal) were examined individually by three endodontists experienced in scanning electron microscope evaluation. Micrographs were rated on a scale of 1 to 4 for overall cleanliness, presence of debris, and presence of open and clean dentinal tubules (1 = least debris or cleanest, 4 = most debris or dirtiest). Evaluators were not aware of which group any sample was taken from. Scores were averaged to obtain an overall cleanliness rating for each of the three levels for both experimental groups. Interrater reliability was found to be high with a l-digit difference 25% of the timt and a 2-digit difference only 2% of the time. Scores weft TAaLE 1. Irrigant volume per tooth (milliliter), 2.625% NaOQ Tooth
Ultrasonic instrumentation (ml)
Hand instrumentation (ml)
1 2 3 4 5 6 7 8 9 10 11
178 165 115 140 119 120 145 158 125 141 150
30 36 39 33 36 33 36 36 36 33 36
Average
141
35
Vol. 14, No. 9, September 1988
Ultrasonic versus Hand Instrumentation
statistically evaluated using unpaired t tests to determine whether a quantitative difference in cleanliness existed between the hand instrumented and ultrasonically instrumented teeth at any of the three levels. Scanning micrographs at magnifications ranging from x20 to x2,000 were qualitatively evaluated for patency ofdentinal tubules, presence of debris, and presence of a smear layer. Finally, a statement was made concerning the overall effectiveness of instrumentation in each experimental group using both the qualitative and quantitative data.
437
amounts of hard tissue debris were present at all levels (Figs. 1 and 2). The enlarging instrument left some walls untouched (Fig. 3). Untouched walls were irregular and bumpy with no smear layer (Fig. 4). Untouched walls were covered with varying amounts of hard tissue debris and sometimes contained open dentinal tubules. H A N D I N S T R U M E N T E D TEETH Instrumented walls were generally very smooth (Figs. 5 and 6). Slightly less debris was found at the middle level.
RESULTS The volume of irrigant used in each tooth was recorded (Table 1).
ULTRASONICALLY INSTRUMENTED TEETH Walls were rough, especially at the middle and occlusal levels (Fig. 7). Superficial vertical scratches, nicks, and gashes
Quantitative Analysis Differences between ultrasonic and hand instrumentation were not significant at the apical and coronal levels. At the mid-root level hand filing was significantly better (Table 2).
Qualitative Descriptive Analysis FEATURES C O M M O N TO BOTH EXPERIMENTAL GROUPS Instrumented dentinal walls at all levels were covered with a smear layer which obscured the dentinal tubules. Various TABLE 2. Quantitative rating of canal cleanliness (1 = best, 4 = worst)
Method Level
Apical Level
Middle Level
Coronal Level
Hand Ultrasonic
2.33 2.55
2.09 2.70
2.18 2.55
~Middle level significant at p < 0.01.
FiG1. Hand-filed canal wall, apical third of root. Smear layer obscures dentinal tubules. Much superficial inorganic debris present (dentin chips) (original magnification x500).
FIG 2. Ultrasonically filed canal wall, apical third of root. Similar to Fig. 1 with dentinal tubules obscured by the smear layer and much superficial inorganic debris (original magnification x500).
F~a 3. Hand-filed canal wall, incisal third of root. Arrows indicate part of the canal wall not actually touched by the flies (original magnification x20).
438
Baker et al.
Journal of Endodontics
' ~ ? ~ K_
7"= ~
F~G 4. Ultrasonically filed canal wall, middle third of root. The files did not touch this portion of the canal wall but soft tissue pulpal remnants and predentin have been removed by the sodium hypochlorite irrigation. Calcified dentin with scattered superficial debris remains. Compare this with Fig. 10 in which organic pulpal remnants and predentin remain covering the rough inorganic walls of the canal. Untouched canal walls of hand-instrumented teeth appear the same (original ~agnification x500).
..
".~
'~/',,~,:
". ~
'
~
~
~'~=, ,~ -~,~ ..~
9
9
_ ,. ".?
FIG 6. Hand-filed canal wall, incisal third of root. A smear layer obscures the dentinal tubules. Arrows indicate residual inorganic debris (dentin chips) (original magnification x200).
FIG 7. Ultrasonically filed canal wall, incisal third of root. Note vertical scratches and numerous small nicks (original magnification x20).
DISCUSSION FUG5. Hand-filed canal wall, incisal third of root. Wall appears smooth with a small amount of scattered inorganic debris. Crack probably occurred during splitting of the root (original magnification x20).
could be noticed at lower magnification and at high magnification patches of open dentinal tubules were found in these irregularities (Fig. 8). Slightly more debris was found at the middle level. U N I N S T R U M E N T E D TEETH (CONTROLS) Walls appeared to be uniformly irregular and bumpy with overlying web-like structures (Figs. 9 and 10). Dentin debris was not present and tubules were not visible.
Scanning micrographs and quantitative results indicate a surprisingly large a m o u n t of hard tissue debris remaining at all levels of the root canals despite the high volume of irrigating solution used (Figs. 1, 2, and 8). Total irrigant volume ranged from 119 to 178 ml for ultrasonically prepared teeth and from 30 to 39 ml for the hand-instrumented teeth. The outside diameter of the irrigating needle (<0.55 mm) clearly allowed the irrigant to be delivered to the apical third in the hand-instrumented teeth. It may have been this apical delivery of irrigating solution which resulted in significantly less hard tissue debris at the mid-root level in the hand-instrumented teeth. Even though ultrasonic preparation delivered at least three times as much irrigation volume, the solution flowed down the outside o f the file and may not have been readily
Vol. 14, No. 9, September 1988
FIG 8. Ultrasonically filed canal wall, incisa! third of root. A smear layer covers most of the wall obscuring the dentinal tubules. Numerous nicks are present in the smear layer. Arrows indicate a patch o f open dentinal tubules at the base o f one of the nicks. A moderate amount of superficial inorganic debris is present (original magnification x200).
Ultrasonic versus Hand Instrumentation
439
FIG 10. Uninstrumented canal wall, middle third o f root. Same tooth as in Fig. 9. Wall is covered with web-like soft tissue remains of pulp and predentin (original magnification x500).
would be a breakthrough in the biomechanical instrumentation phase of root canal therapy. Ultrasonic instrumentation has been shown to be effective in these areas (7). In this study both methods of irrigation were effective at removing soft tissue remnants from the uninstrumented canal walls (Fig. 4). In some instances open dentinal tubules were visible. In others, moderate amounts of dentin debris were noted. But compared with the canal walls of the two uninstrumented teeth (Fig. 10), organic soft tissue remnants were effectively removed from the untouched walls by both methods of cleansing. CONCLUSIONS The results of the study indicate that ultrasonic instrumentation is not superior to conventional hand filing and flaring in canal debridement. At mid-level of the root, hand filing was significantly more effective.
FiG 9. Uninstrumented canal wall, middle third of root (original magnification x20).
interchanged at the apex. Martin (11) claims that the ultrasonic motion of the file causes stirring and mixing of the solution within the tooth and that the irrigant flows down the file to the apex even in curved canals. This has not been experimentally verified. Even in the straight canals of maxillary central incisors, some walls were left untouched by enlarging instruments (Fig. 3). This was observed and allowed a comparison to be made between ultrasonically "activated" irrigation and normal irrigation with regard to removal of organic and inorganic debris from these untouched areas. The ability to effectively remove pulpal remnants, bacteria, and other debris from these areas
This study was supported in part by research funding from the AAE Endowment and Memorial Foundation and the Edward C. Wach Research Fund, University of Illinois School of Dentistry. This article is from a thesis submitted by Dr. Baker in partial fulfillment of the requirements for a certificate in endodontics at the University of Illinois at Chicago, College of Dentistry. Dr. Baker is assistant professor, Department of Endodontics, University of Illinois at Chicago, Chicago, IL. Dr. Ashrafi is associate professor, Oral Pathology, Histology, and Pathology Departments, University of Illinois at Chicago. Dr. Van Cura is professor and director, Postdoctoral Endodontics, University of Illinois at Chicago. Dr. Remeikis is professor and head, Endodontics Department, University of Illinois at Chicago. Address requests for reprints to Dr. Mark C. Baker, Department of Endodontics, College of Dentistry, University of Illinois at Chicago, 801 South Paulina Street, Chicago, IL 60612.
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solving ability of sodium hypochlorite endodontic irrigant. Oral Surg 1980;49:175-7. 3. Cunningham w r , Joseph SW. Effect of temperature on the bactericidal action of sodium hypochlorite endodontic irngant. Oral Surg 1980;50:569-71. 4. Martin H, Cunningham WT, Norris JP, Cotton WR. Ultrasonic versus hand filing of dentin: a quantitative study. Oral Surg 1980;49:79-81. 5. Martin H, Cunningham WT, Norris JP. A quantitative comparison of the ability of diamond and K-type files to remove dentin. Oral Surg 1980;50:5668. 6. Martin H, Gunningham WT. The effect of endosonic and hand manipulation on the amount of root canal rnaterial extruded. Oral Surg 1982;53:6113. 7. Cunningham WT, Martin H, Forrest WR. Evaluation of root canal debride-
Joumal of Endodontics ment by the endosonic ultrasonic synergistic system. Oral Surg 1982;53:401_ 4. 8. Cunningham WT, Martin H. A scanning electron microscope evaluation of root canal debridement with the ultrasonic synergistic system. Oral Surg 1982;53:527-31. 9. Cymerman JJ, Jerome LA, Moodnik RM. A scanning electron microscope study comparing the efficacy of hand instrumentation with ultrasonic instrumentation of the root canal. J Endodon 1983;9:327-31. 10. Walton RG. Histologic evaluation of different methods of enlarging the pulp canal space. J Endodon 1976;2:304-11. 11. Martin H. American Association of Endodontists tape recording of ultrasonic endodontic presentation at AAE Meeting in Hollywood, FL, April 1983.