0099-2399/92/1812-0601/$03.00/0 JOURNAL OF ENDODONTICS Copyright © 1992 by The American Associ~ion of Endodontists
Printed in U.S.A.
VOL. 18, No. 12, DECEMBER1992
Dentin Removal Efficiency of Six Endodontic Systems: A Quantitative Comparison Martine Hennequin, DDS, PhD, Jean-Fred0ric Andre, DDS, and Germaine Botta, DDS
graphic measurements or overlays (6, 7). Other articles have compared sonics and ultrasonics on different bases: histological (8), amount of debris eliminated (9), apical deviation (10), canal transportation (11), canal shape (12), general appreciations (13), or using a weight loss method (14). The purpose of this study was to compare different endodontic devices under identical experimental conditions, using a weight loss method applied to the whole natural tooth root.
The dentin removal efficiency of current endodontic systems, based on the amount of dentin removed in 1 mm of canal axial length, was determined for working times of I and 2 min. Six endodontic systerns were compared: The Giromatic with Heli-Giro files, the Sonic-Air with Shapers, the Mecasonic with Shapers, the Cavi-Med with K files, the Cavi-Med with Shapers, the Excalibur with its own K files. Generally speaking, the efficiency of each device depends on the duration of instrumentation, on the type of file used, and on its mode of activation. For I min of instrumentation, the Mecasonic + Shaper was the most efficient system. For 2 min of instrumentation, the original adaptation of the Shaper on the Cavi-Med gave the highest activity. Concerning the files used in ultrasonics, the Shaper seems to be more efficient than the K file. As for the sonics, the Excalibur -I- file system gave results comparable to those of the Mecasonic + Shaper; both of these devices were twice as efficient as the Sonic-Air + Shaper.
MATERIALS AND METHODS One hundred seventy-five extracted human mandibular incisors were sectioned at the cementoenamel junction. A #15 K-type file was introduced into each canal until it appeared at the apical foramen. One millimeter was subtracted from this measurement to establish the working length, to which the canal was prepared using a #20 K-type file. Each tooth was stored in one sample container. Each pair of tooth and sample container was numbered and placed in a dessicator at 55°C. Each sample (sample container and tooth) was weighed daily to IAooth mg precision (Sartorius, Palaiseau, France) at room temperature, with Silica-Gel (Aldrich Chemical Co., Milwaukee, WI) to avoid the variations in moisture content. Daily weight measurements were taken for every sample. Immediately after it was taken out of the dessicator, the sample container was closed with its own cap in order to avoid rehydration of the tooth. Weighing was done 1 h later, when the weight of the sample container was stabilized after its own rehydration. The dessication cycle, with the daily weight measurements, was maintained for 3 wk in order to obtain a reference time for usable, steady weights. A mean constant weight (m0, was calculated from the daily weighing of the final week. Twenty-four hours before instrumentation, each sample container was filled with distilled water and seven groups of 25 teeth were randomly assigned: Group 1--controls; the teeth were not instrumented. Group 2--instrumented by the Giromatic with #20 Heli-Giro files (Micro Mega, Besanqon, France). Group 3--instrumented by the Sonic-Air (MM3000) with #20 Shapers (Micro Mega). Group 4--instrumented by the Mecasonic with #20 Shapers (Micro Mega). Group 5--instrumented by the Cavi-Med at the mean power setting with #20 K-type files (Detrey Dentsply, Bois Colombe, France). Group 6--instrumented by the Cavi-Med at the mean power with #20 Shapers. Simple removal of the plastic
With the appearance of new techniques in endodontics, many experiments have been carried out in order to determine or compare their efficiency in real or simulated root canals. Several factors have to be considered, such as the cutting efficiency of each instrument, the duration of instrumentation, the instrumentation technique, and the actual cleaning efficiency of each instrument. A general review of the literature tends to show that endosonics can improve upon conventional root canal therapy. Many different methods have been described to evaluate the efficiency of mechanized endodontic instruments, including rotating (1) and vibrating systems. Among these, scanning electron studies have compared hand and mechanized instrumented canal preparations in terms of shape and cleanliness (2, 3) while other studies have been undertaken in order to make bacteriological evaluations and comparisons (4). Neutronographic and microdensitometric experiments have also been carried out to evaluate canal shapes after hand and mechanized instrumentations (5) and several studies have evaluated filing ability with radio-
601
602
Hennequin et al.
Journal of Endodontics
(mg/mm) 0.1 FIRST MINUTE 0 mt,~j~ . . . . . .
SECOND MINUTE 0
-0. I
-0.1,
-0.2
-0.2
-0.3
-0.3
'
-0.4
-0.4
•
-0.5
41.5.
'
-0.6
-0.6
-0.7
-0.7 •
-0.8
-0.8
'
ns
TOTAL 0 -0.2 -0.4 -0.6 -0.8
I
I
-I
L
-I.2 -I.4
.!_
•
CONTROL
•
GIROMATIC*HELIGIROFILE
[ ] SONIC-AIR+SHAPER [ ] CAVI-MED*K-FILE [ ] MECA.SONIC÷SHAPER [ ] EXCALIEUR';'FILE [~1 CAVI-MED+SHAPER
F~G 1. Graphs showing the DRE values obtained for each endodontic system after the first, the second, and the 2 min of instrumentation. Significant differences, using Student's t test, are indicated by ,Sp > 0.005, *p < 0.005, **p < 0.01, ***p < 0.001.
TABLE 1. Ranking results after 1 min of instrumentation System Control Giromatic + Heli-Giro file Sonic-Air + Shaper Cavi-Med + K file Excalibur + file Cavi-Med + Shaper Mecasonic + Shaper
DRE __ SD (rag.ram-I) 0.02 -0.04 -0.18 -0.32 -0.47 -0.63 -0.76
_+ 0.02 _+ 0.02 + 0.02 _+ 0.02 __ 0.04 _+ 0.03 __ 0.05
TABLE 2. Results for the second minute of instrumentation System Control Giromatic + Heli-Giro file Mecasonic + Shaper Sonic-Air + Shaper Cavi-Med + K file Excalibur + file Cavi-Med + Shaper
DRE + SD (mg. mm -1) -0.07 -0.18 -0.26 -0.27 -0.47 -0.65 -0.75
_ 0.01 -+ 0.02 _ 0.02 + 0.02 + 0.03 -+ 0.04 _+ 0.04
head of the Shaper allows it to be mounted on the Cavi-Med unit. Group 7--instrumented by the Excalibur with special #20 Excalibur files (W. & H. Ergodental, Strasbourg, France.) During instrumentation, each tooth was held by an operator wearing surgical gloves. All instrumentation was performed by the same operator. Each tooth was assigned a new #20 instrument upon which the working length was marked. The instrument was passively introduced into the root canal
to the desired working length. It was first turned on for 20 s during which contacts with the canal walls were not intended. Then it was driven for 40 s according to the "contact shaping technique" (15). All instrumentation was carried out with continuous water irrigation. A syringe was used during the instrumentation of group 2 using the Giromatic which does not have an integrated irrigation system. The root canal was then rinsed with water and dried with an air spray. For the control group, the teeth were simply held by the operator and irrigated for 1 rain with water. After the first minute of instrumentation, each tooth was put back in its own sample container and all groups were placed in the dessicator to undergo another 3 wk of dessication with weight measurements taken daily, after which a second constant mean weight (m2) was determined from the final week's weighing. The weight loss was calculated for each sample in each group. In order to compensate for the variations in tooth length, the efficiency of each device was determined first for each tooth by dividing the weight loss by the root canal working length [(m2 - m J/L], and second for each group by averaging these results. This latter value was called dentin removal efficiency (DRE). A second minute of instrumentation was then carried out according to the contact shaping technique for 60 s, followed by a final 3-wk period of dessication with the daily weight measurements in order to determine a final mean weight (m3). The DRE of each instrument for the second minute [(m3 m2)/L] and for the 2 min of instrumentation [(m3 - ml)/L] were determined. The results gave a ranking of the DRE. Paired t tests were used to examine the significance of the difference between groups two by two.
RESULTS The DRE values of each instrument for the first minute, the second minute, and the 2 min of instrumentation are shown in Fig. 1. After the first minute of instrumentation, the results gave the ranking listed in Table 1. The Mecasonic's dentin removal ability was superior to all other devices. All sonics and ultrasonics removed more dentin than the rotating Giromatic, which was not significantly different from the control group. The efficiency of the Excalibur + file was greater than the Cavi-Med with K file and the Sonic-Air + Shaper. For the second minute of instrumentation, the highest efficiencies were obtained with the Cavi-Med + Shaper and the Excalibur + File. The results are given in Table 2. The shaper seemed to be more efficient on the ultrasonic device (Cavi-Med) than on the sonic ones (Sonic-Air and Mecasonic). All devices, except the Mecasonic, were more efficient during the second minute (p > 0.01 for the Sonic-Air + Shaper, Cavi-Med + Shaper and p > 0.001 for all other systems). Results for the 2 min of instrumentation are presented in Table 3. The original Cavi-Med + Shaper association was the most efficient device. The Excalibur + file was as efficient as the Mecasonic + Shaper.
Efficiency of Endodontic Systems
Vol. 18, No. 12, December 1992 TABLE 3. Two-minute instrumentation results System Control Giromatic + Heli-Giro file Sonic-Air + Shaper Cavi-Med + K file Mecasonic + Shaper Excalibur + file Cavi-Med + Shaper
DRE _+ SD (m9. mm_l) -0.05 -0.22 -0.45 -0.79 -1.02 -1.12 -1.38
__ 0.03 + 0.03 _+ 0.04 _+ 0.04 _+ 0.06 __ 0.07 _+ 0.05
DISCUSSION Desiccation cycles stabilize the sample's hydric concentration but can also induce cracks in the dentin and cause splinters to fall to the bottom of the sample container. Therefore, throughout the experiment our samples included the tooth and its own sample container, for weight reproducibility. The length of a desiccation cycle was fixed at 3 wk. The daily weight measurements started 2 days after the sample was placed in the dessicator, when all of the sample containers seemed to be clear of water. A possible source of error could have come from the reference time chosen for the weight loss measurements. The time course of the weight loss of the 175 teeth measured over the 3-wk dessication period was very irregular. The daily loss decreased progressively in the first week, the greatest loss occurring during the first days of measurement. The total weight loss of the third day of dessication was, for example, greater than the weight loss observed in some tested groups after instrumentation. In contrast, weight differences became alternatively, from day to day, negative and positive the second and third weeks when variations became negligible. Therefore, the third week was used to calculate the average weight of each sample at the end of the dessication cycle. The samples were rehydrated before instrumentation to bring them closer to clinical conditions, and so that the tooth splinters created by dessication stayed at the bottom of the sample container. Instrumentation was carried out according to the contact shaping technique, which presents the following advantages: the possibility of enlarging the canal immediately after catheterism with small instruments, the flexibility of which enables them to easily pass through elbows and other obstacles, the prevention of canal perforations since the instrument is activated once it has penetrated the canal to the full working length, and the control of the instrument's movement which is transmitted longitudinally by the operator. One minute of instrumentation is the time generally recommended for each step in the instrumental progression. During the first minute, the 20 s of passive activation is intended to eliminate interferences and to liberate the vibratory movement of the instrument in the canal. A second minute of instrumentation was suggested here for two reasons. First, lengthening the working time could increase the differences between the activity indices of the different groups, thus allowing a better understanding of the wearing possibilities for each instrument. Second, since the rapidity of the endodontic treatment remained our primary concern, increasing the working time with one file size may prove to be more efficient than following the classical
603
instrumental sequence and then could enable a reduction in the duration of treatment. Continuous irrigation is generally considered to be essential in endodontics (16). The choice of water as irrigant in our study was done deliberately to avoid the chemical effects obtained with the usual irrigants. Moreover, heat generation which occurs during the use of ultrasound units (17) could increase the effect of a chemical agent. Obviously, the most active endodontic instrument will not necessarily give the best results in terms of canal shape and cleanliness. This study classifies six endodontic devices according to their dentin removal efficiency only. Therefore, to be of use to the practitioner, these results must be used along with other factors such as root canal shape, cleanliness of the canal walls, thickness of the remaining canal walls, adaptability in the choice of irrigant, ease of file changing, depth control, portability, cost, etc. (13). The amount of dentin removed only characterizes the quantitative side of efficiency, but does not take into account the location on the canal walls of the removed dentinal volumes. For all systems tested, except the Mecasonic, the activity indices were higher for the second minute of instrumentation, which may be explained by the progressive liberation of the file's vibration as the canal was enlarged. A 2-min instrumentation time could be advised to users of these devices. Comparable results were obtained with the Cavi-Med + file for 2 min and the Mecasonic + Shaper for 1 rain. The Giromatic's performance was inferior to that of the sonics and ultrasonics for several reasons. First, the shape of the Heli-Giro file presents a low cutting potential compared with the Shaper. Another reason may be the lack of an integrated irrigation system. Insufficient elimination of dentinal debris in the canal, also caused in part by a limited enlargement after 1 rain of instrumentation, may have been responsible for the insignificant weight loss percentage. Therefore, a study including the new adapted Giromatic (Giromatic-S; Micro Mega) would be of interest. Sonic-Air and Mecasonic are two similar devices, but the Mecasonic is four times more efficient for 1 min of instrumentation. The shaper's vibration is generated by the excentric rotation of the handpiece's gearing axis, in both of these devices. However, the Sonic-Air is an air-powered device whereas the Mecasonic is electric; in the latter, the torque should be greater, increasing the Shaper's effect. The resulting excessive wear of the Shaper may be the reason for the reduced effects of the Mecasonic during the second minute of instrumentation. The Cavi-Med equipped with a Shaper removes almost twice as much dentin as that with a file. The shaper seems well adapted to ultrasonics. There is less wear when it is activated by the Cavi-Med rather than by the Mecasonic. Despite its seemingly less aggressive special file design, the Excalibur provides a cutting ability comparable to that of the Cavi-Med equipped with a Shaper for the second minute of instrumentation and equals the activity of the Mecasonic for a total instrumentation time of 2 min. For the endodontist, changing the incremented files during the enlargement sequence is a nuisance. We believe that the high 2-min activity of the three most efficient devices (Cavi-Med + Shaper, Excalibur + File, Mecasonic + Shaper) will allow the instrumentation sequence to be reduced. This may be particularly appreciable with highly mineralized teeth. The calculation of the DRE during canal preparation enables the quantification of the efficiency of endodontic instru-
604
Hennequin et al.
Journal of Endodontics
ments. The method described in the study could be adopted by manufacturers of dental equipment in order to give practitioners better information about instruments. This study should assist the endodontist in either the use of a device or in the choice of a new one. We thank the Brevard & Crozat (Romagnat, France) for the loan of material and A. M. Gaydier and S. Millien for their technical assistance. Dr. Hennequin and Dr. Andre are members of the Department of Restorative Dentistry and Endodontics, Faculty of Dentistry, Universit6 d'Auvergne, Clermont Ferrand, France. Dr. Botta is in private practice in La Farlede, France. Address requests for reprints to Dr. Martine Hennequin, Department de Recherche, Facult~ de Chirurgie Dentaire, 11 Bd Charles De Gaulle, 63000 Clermont Ferrand, France.
References 1. Harty FJ, Stock CJR. The giromatic system compared with hand instrumentation in endodontics. Br Dent J 1974;137:239-44. 2. Baker MC, Ashrafi H, Van Cura JE, Remeikis NA. Ultrasonic compared with hand instrumentation: a scanning electron microscopic study. J Endodon 1988;14:435-40. 3. Biffi JCG, Rodrigues HH. Ultrasound in endodontics: a quantitative and histological assessment using human teeth. Endod Dent Traumato11989;5:5562.
4. Denunzio MS, Hicks ML, Pelleu GB, Kingman A, Sauber JJ. A bacteriological comparison of ultrasonic and hand instrumentation of root canals in dogs. J Endodon 1989;15:290-93. 5. Vulcain JM, Pilven A, Espie JH, Bayon G. Activit6 ampliative des instruments endosoniques; ~tude par neutronographie et microdensitometrie. Rev Fr Endod 1987;6:13-20. 6. Ahmad M, Pitt Ford TR. A comparison using macroradiography of canal shapes in teeth instrumented ultrasonically and by hand. J Endodon 1989;15:339-44. 7. Chenail BL, Teplitsky PE. Endosonics in curved root canals. J Endodon 1985;11:369-74. 8. Walker TL, del Rio CE. Histological evaluation of ultrasonic and sonic instrumentation of curved root canals. J Endodon 1989;15:49-9. 9. Langeland K, Liao K, Pascon EA. Work-saving devices in endodontics: efficacy of sonic and ultrasonic techniques. J Endodon 1985;11:499-510. 10. Ahmad M, Pitt Ford TR. Comparison of two ultrasonic units in shaping simulated curved canals. J Endodon 1989;15:457-62. 11. Kielt LW, Montgomery S. The effect of endosonic instrumentation in simulated curved root canals. J Endodon 1987;13:215-19. 12. Loushine R, Weiler RN, Hartwell GR. Stereomicroscopic evaluation of canal shape following hand and ultrasonic instrumentation. J Endodon 1989; 15:417-21. 13. Pugh RJ, Goerig AC, Glaser CG, Luciano WJ. A comparison of four endodontic vibratory systems. Gen Dent 1989;37:296-301. 14. Martin H, Cunningham WT, Norris JP, Cotton WR. Ultrasonic versus hand filing of dentin: a quantitative study. Oral Surg 1980;49:79-81. 15. Laurichesse JM. La technique de rappui pari(~tal (T.A.P.) Rev Fr Ended 1985;4:19-37. 16. Stamos DE, Sadeighi EM, Haasch GC, Gerstein H. An in vitro comparison to quantitate the debridement ability of hand, sonic, and ultrasonic instrumentation. J Endodon 1987;13:434-40. 17. Cameron JA. The effect of ultrasonic endodontics on the temperature of the root canal wall. J Endodon 1988;14:554-9.
The Way It Was In Dodge City, Kansas, in 1875 about 82% of the population was male and about half the men were between the age of 20 and 29 (J Hist Med 46:463). No wonder there was so much feudin', fightin' and fussin'.
Cosby Newell
Printed in U.S.A.
VOL. 18, No. 12, DECEMBER1992
Dentin Removal Efficiency of Six Endodontic Systems: A Quantitative Comparison Martine Hennequin, DDS, PhD, Jean-Fred0ric Andre, DDS, and Germaine Botta, DDS
graphic measurements or overlays (6, 7). Other articles have compared sonics and ultrasonics on different bases: histological (8), amount of debris eliminated (9), apical deviation (10), canal transportation (11), canal shape (12), general appreciations (13), or using a weight loss method (14). The purpose of this study was to compare different endodontic devices under identical experimental conditions, using a weight loss method applied to the whole natural tooth root.
The dentin removal efficiency of current endodontic systems, based on the amount of dentin removed in 1 mm of canal axial length, was determined for working times of I and 2 min. Six endodontic systerns were compared: The Giromatic with Heli-Giro files, the Sonic-Air with Shapers, the Mecasonic with Shapers, the Cavi-Med with K files, the Cavi-Med with Shapers, the Excalibur with its own K files. Generally speaking, the efficiency of each device depends on the duration of instrumentation, on the type of file used, and on its mode of activation. For I min of instrumentation, the Mecasonic + Shaper was the most efficient system. For 2 min of instrumentation, the original adaptation of the Shaper on the Cavi-Med gave the highest activity. Concerning the files used in ultrasonics, the Shaper seems to be more efficient than the K file. As for the sonics, the Excalibur -I- file system gave results comparable to those of the Mecasonic + Shaper; both of these devices were twice as efficient as the Sonic-Air + Shaper.
MATERIALS AND METHODS One hundred seventy-five extracted human mandibular incisors were sectioned at the cementoenamel junction. A #15 K-type file was introduced into each canal until it appeared at the apical foramen. One millimeter was subtracted from this measurement to establish the working length, to which the canal was prepared using a #20 K-type file. Each tooth was stored in one sample container. Each pair of tooth and sample container was numbered and placed in a dessicator at 55°C. Each sample (sample container and tooth) was weighed daily to IAooth mg precision (Sartorius, Palaiseau, France) at room temperature, with Silica-Gel (Aldrich Chemical Co., Milwaukee, WI) to avoid the variations in moisture content. Daily weight measurements were taken for every sample. Immediately after it was taken out of the dessicator, the sample container was closed with its own cap in order to avoid rehydration of the tooth. Weighing was done 1 h later, when the weight of the sample container was stabilized after its own rehydration. The dessication cycle, with the daily weight measurements, was maintained for 3 wk in order to obtain a reference time for usable, steady weights. A mean constant weight (m0, was calculated from the daily weighing of the final week. Twenty-four hours before instrumentation, each sample container was filled with distilled water and seven groups of 25 teeth were randomly assigned: Group 1--controls; the teeth were not instrumented. Group 2--instrumented by the Giromatic with #20 Heli-Giro files (Micro Mega, Besanqon, France). Group 3--instrumented by the Sonic-Air (MM3000) with #20 Shapers (Micro Mega). Group 4--instrumented by the Mecasonic with #20 Shapers (Micro Mega). Group 5--instrumented by the Cavi-Med at the mean power setting with #20 K-type files (Detrey Dentsply, Bois Colombe, France). Group 6--instrumented by the Cavi-Med at the mean power with #20 Shapers. Simple removal of the plastic
With the appearance of new techniques in endodontics, many experiments have been carried out in order to determine or compare their efficiency in real or simulated root canals. Several factors have to be considered, such as the cutting efficiency of each instrument, the duration of instrumentation, the instrumentation technique, and the actual cleaning efficiency of each instrument. A general review of the literature tends to show that endosonics can improve upon conventional root canal therapy. Many different methods have been described to evaluate the efficiency of mechanized endodontic instruments, including rotating (1) and vibrating systems. Among these, scanning electron studies have compared hand and mechanized instrumented canal preparations in terms of shape and cleanliness (2, 3) while other studies have been undertaken in order to make bacteriological evaluations and comparisons (4). Neutronographic and microdensitometric experiments have also been carried out to evaluate canal shapes after hand and mechanized instrumentations (5) and several studies have evaluated filing ability with radio-
601
602
Hennequin et al.
Journal of Endodontics
(mg/mm) 0.1 FIRST MINUTE 0 mt,~j~ . . . . . .
SECOND MINUTE 0
-0. I
-0.1,
-0.2
-0.2
-0.3
-0.3
'
-0.4
-0.4
•
-0.5
41.5.
'
-0.6
-0.6
-0.7
-0.7 •
-0.8
-0.8
'
ns
TOTAL 0 -0.2 -0.4 -0.6 -0.8
I
I
-I
L
-I.2 -I.4
.!_
•
CONTROL
•
GIROMATIC*HELIGIROFILE
[ ] SONIC-AIR+SHAPER [ ] CAVI-MED*K-FILE [ ] MECA.SONIC÷SHAPER [ ] EXCALIEUR';'FILE [~1 CAVI-MED+SHAPER
F~G 1. Graphs showing the DRE values obtained for each endodontic system after the first, the second, and the 2 min of instrumentation. Significant differences, using Student's t test, are indicated by ,Sp > 0.005, *p < 0.005, **p < 0.01, ***p < 0.001.
TABLE 1. Ranking results after 1 min of instrumentation System Control Giromatic + Heli-Giro file Sonic-Air + Shaper Cavi-Med + K file Excalibur + file Cavi-Med + Shaper Mecasonic + Shaper
DRE __ SD (rag.ram-I) 0.02 -0.04 -0.18 -0.32 -0.47 -0.63 -0.76
_+ 0.02 _+ 0.02 + 0.02 _+ 0.02 __ 0.04 _+ 0.03 __ 0.05
TABLE 2. Results for the second minute of instrumentation System Control Giromatic + Heli-Giro file Mecasonic + Shaper Sonic-Air + Shaper Cavi-Med + K file Excalibur + file Cavi-Med + Shaper
DRE + SD (mg. mm -1) -0.07 -0.18 -0.26 -0.27 -0.47 -0.65 -0.75
_ 0.01 -+ 0.02 _ 0.02 + 0.02 + 0.03 -+ 0.04 _+ 0.04
head of the Shaper allows it to be mounted on the Cavi-Med unit. Group 7--instrumented by the Excalibur with special #20 Excalibur files (W. & H. Ergodental, Strasbourg, France.) During instrumentation, each tooth was held by an operator wearing surgical gloves. All instrumentation was performed by the same operator. Each tooth was assigned a new #20 instrument upon which the working length was marked. The instrument was passively introduced into the root canal
to the desired working length. It was first turned on for 20 s during which contacts with the canal walls were not intended. Then it was driven for 40 s according to the "contact shaping technique" (15). All instrumentation was carried out with continuous water irrigation. A syringe was used during the instrumentation of group 2 using the Giromatic which does not have an integrated irrigation system. The root canal was then rinsed with water and dried with an air spray. For the control group, the teeth were simply held by the operator and irrigated for 1 rain with water. After the first minute of instrumentation, each tooth was put back in its own sample container and all groups were placed in the dessicator to undergo another 3 wk of dessication with weight measurements taken daily, after which a second constant mean weight (m2) was determined from the final week's weighing. The weight loss was calculated for each sample in each group. In order to compensate for the variations in tooth length, the efficiency of each device was determined first for each tooth by dividing the weight loss by the root canal working length [(m2 - m J/L], and second for each group by averaging these results. This latter value was called dentin removal efficiency (DRE). A second minute of instrumentation was then carried out according to the contact shaping technique for 60 s, followed by a final 3-wk period of dessication with the daily weight measurements in order to determine a final mean weight (m3). The DRE of each instrument for the second minute [(m3 m2)/L] and for the 2 min of instrumentation [(m3 - ml)/L] were determined. The results gave a ranking of the DRE. Paired t tests were used to examine the significance of the difference between groups two by two.
RESULTS The DRE values of each instrument for the first minute, the second minute, and the 2 min of instrumentation are shown in Fig. 1. After the first minute of instrumentation, the results gave the ranking listed in Table 1. The Mecasonic's dentin removal ability was superior to all other devices. All sonics and ultrasonics removed more dentin than the rotating Giromatic, which was not significantly different from the control group. The efficiency of the Excalibur + file was greater than the Cavi-Med with K file and the Sonic-Air + Shaper. For the second minute of instrumentation, the highest efficiencies were obtained with the Cavi-Med + Shaper and the Excalibur + File. The results are given in Table 2. The shaper seemed to be more efficient on the ultrasonic device (Cavi-Med) than on the sonic ones (Sonic-Air and Mecasonic). All devices, except the Mecasonic, were more efficient during the second minute (p > 0.01 for the Sonic-Air + Shaper, Cavi-Med + Shaper and p > 0.001 for all other systems). Results for the 2 min of instrumentation are presented in Table 3. The original Cavi-Med + Shaper association was the most efficient device. The Excalibur + file was as efficient as the Mecasonic + Shaper.
Efficiency of Endodontic Systems
Vol. 18, No. 12, December 1992 TABLE 3. Two-minute instrumentation results System Control Giromatic + Heli-Giro file Sonic-Air + Shaper Cavi-Med + K file Mecasonic + Shaper Excalibur + file Cavi-Med + Shaper
DRE _+ SD (m9. mm_l) -0.05 -0.22 -0.45 -0.79 -1.02 -1.12 -1.38
__ 0.03 + 0.03 _+ 0.04 _+ 0.04 _+ 0.06 __ 0.07 _+ 0.05
DISCUSSION Desiccation cycles stabilize the sample's hydric concentration but can also induce cracks in the dentin and cause splinters to fall to the bottom of the sample container. Therefore, throughout the experiment our samples included the tooth and its own sample container, for weight reproducibility. The length of a desiccation cycle was fixed at 3 wk. The daily weight measurements started 2 days after the sample was placed in the dessicator, when all of the sample containers seemed to be clear of water. A possible source of error could have come from the reference time chosen for the weight loss measurements. The time course of the weight loss of the 175 teeth measured over the 3-wk dessication period was very irregular. The daily loss decreased progressively in the first week, the greatest loss occurring during the first days of measurement. The total weight loss of the third day of dessication was, for example, greater than the weight loss observed in some tested groups after instrumentation. In contrast, weight differences became alternatively, from day to day, negative and positive the second and third weeks when variations became negligible. Therefore, the third week was used to calculate the average weight of each sample at the end of the dessication cycle. The samples were rehydrated before instrumentation to bring them closer to clinical conditions, and so that the tooth splinters created by dessication stayed at the bottom of the sample container. Instrumentation was carried out according to the contact shaping technique, which presents the following advantages: the possibility of enlarging the canal immediately after catheterism with small instruments, the flexibility of which enables them to easily pass through elbows and other obstacles, the prevention of canal perforations since the instrument is activated once it has penetrated the canal to the full working length, and the control of the instrument's movement which is transmitted longitudinally by the operator. One minute of instrumentation is the time generally recommended for each step in the instrumental progression. During the first minute, the 20 s of passive activation is intended to eliminate interferences and to liberate the vibratory movement of the instrument in the canal. A second minute of instrumentation was suggested here for two reasons. First, lengthening the working time could increase the differences between the activity indices of the different groups, thus allowing a better understanding of the wearing possibilities for each instrument. Second, since the rapidity of the endodontic treatment remained our primary concern, increasing the working time with one file size may prove to be more efficient than following the classical
603
instrumental sequence and then could enable a reduction in the duration of treatment. Continuous irrigation is generally considered to be essential in endodontics (16). The choice of water as irrigant in our study was done deliberately to avoid the chemical effects obtained with the usual irrigants. Moreover, heat generation which occurs during the use of ultrasound units (17) could increase the effect of a chemical agent. Obviously, the most active endodontic instrument will not necessarily give the best results in terms of canal shape and cleanliness. This study classifies six endodontic devices according to their dentin removal efficiency only. Therefore, to be of use to the practitioner, these results must be used along with other factors such as root canal shape, cleanliness of the canal walls, thickness of the remaining canal walls, adaptability in the choice of irrigant, ease of file changing, depth control, portability, cost, etc. (13). The amount of dentin removed only characterizes the quantitative side of efficiency, but does not take into account the location on the canal walls of the removed dentinal volumes. For all systems tested, except the Mecasonic, the activity indices were higher for the second minute of instrumentation, which may be explained by the progressive liberation of the file's vibration as the canal was enlarged. A 2-min instrumentation time could be advised to users of these devices. Comparable results were obtained with the Cavi-Med + file for 2 min and the Mecasonic + Shaper for 1 rain. The Giromatic's performance was inferior to that of the sonics and ultrasonics for several reasons. First, the shape of the Heli-Giro file presents a low cutting potential compared with the Shaper. Another reason may be the lack of an integrated irrigation system. Insufficient elimination of dentinal debris in the canal, also caused in part by a limited enlargement after 1 rain of instrumentation, may have been responsible for the insignificant weight loss percentage. Therefore, a study including the new adapted Giromatic (Giromatic-S; Micro Mega) would be of interest. Sonic-Air and Mecasonic are two similar devices, but the Mecasonic is four times more efficient for 1 min of instrumentation. The shaper's vibration is generated by the excentric rotation of the handpiece's gearing axis, in both of these devices. However, the Sonic-Air is an air-powered device whereas the Mecasonic is electric; in the latter, the torque should be greater, increasing the Shaper's effect. The resulting excessive wear of the Shaper may be the reason for the reduced effects of the Mecasonic during the second minute of instrumentation. The Cavi-Med equipped with a Shaper removes almost twice as much dentin as that with a file. The shaper seems well adapted to ultrasonics. There is less wear when it is activated by the Cavi-Med rather than by the Mecasonic. Despite its seemingly less aggressive special file design, the Excalibur provides a cutting ability comparable to that of the Cavi-Med equipped with a Shaper for the second minute of instrumentation and equals the activity of the Mecasonic for a total instrumentation time of 2 min. For the endodontist, changing the incremented files during the enlargement sequence is a nuisance. We believe that the high 2-min activity of the three most efficient devices (Cavi-Med + Shaper, Excalibur + File, Mecasonic + Shaper) will allow the instrumentation sequence to be reduced. This may be particularly appreciable with highly mineralized teeth. The calculation of the DRE during canal preparation enables the quantification of the efficiency of endodontic instru-
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Journal of Endodontics
ments. The method described in the study could be adopted by manufacturers of dental equipment in order to give practitioners better information about instruments. This study should assist the endodontist in either the use of a device or in the choice of a new one. We thank the Brevard & Crozat (Romagnat, France) for the loan of material and A. M. Gaydier and S. Millien for their technical assistance. Dr. Hennequin and Dr. Andre are members of the Department of Restorative Dentistry and Endodontics, Faculty of Dentistry, Universit6 d'Auvergne, Clermont Ferrand, France. Dr. Botta is in private practice in La Farlede, France. Address requests for reprints to Dr. Martine Hennequin, Department de Recherche, Facult~ de Chirurgie Dentaire, 11 Bd Charles De Gaulle, 63000 Clermont Ferrand, France.
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4. Denunzio MS, Hicks ML, Pelleu GB, Kingman A, Sauber JJ. A bacteriological comparison of ultrasonic and hand instrumentation of root canals in dogs. J Endodon 1989;15:290-93. 5. Vulcain JM, Pilven A, Espie JH, Bayon G. Activit6 ampliative des instruments endosoniques; ~tude par neutronographie et microdensitometrie. Rev Fr Endod 1987;6:13-20. 6. Ahmad M, Pitt Ford TR. A comparison using macroradiography of canal shapes in teeth instrumented ultrasonically and by hand. J Endodon 1989;15:339-44. 7. Chenail BL, Teplitsky PE. Endosonics in curved root canals. J Endodon 1985;11:369-74. 8. Walker TL, del Rio CE. Histological evaluation of ultrasonic and sonic instrumentation of curved root canals. J Endodon 1989;15:49-9. 9. Langeland K, Liao K, Pascon EA. Work-saving devices in endodontics: efficacy of sonic and ultrasonic techniques. J Endodon 1985;11:499-510. 10. Ahmad M, Pitt Ford TR. Comparison of two ultrasonic units in shaping simulated curved canals. J Endodon 1989;15:457-62. 11. Kielt LW, Montgomery S. The effect of endosonic instrumentation in simulated curved root canals. J Endodon 1987;13:215-19. 12. Loushine R, Weiler RN, Hartwell GR. Stereomicroscopic evaluation of canal shape following hand and ultrasonic instrumentation. J Endodon 1989; 15:417-21. 13. Pugh RJ, Goerig AC, Glaser CG, Luciano WJ. A comparison of four endodontic vibratory systems. Gen Dent 1989;37:296-301. 14. Martin H, Cunningham WT, Norris JP, Cotton WR. Ultrasonic versus hand filing of dentin: a quantitative study. Oral Surg 1980;49:79-81. 15. Laurichesse JM. La technique de rappui pari(~tal (T.A.P.) Rev Fr Ended 1985;4:19-37. 16. Stamos DE, Sadeighi EM, Haasch GC, Gerstein H. An in vitro comparison to quantitate the debridement ability of hand, sonic, and ultrasonic instrumentation. J Endodon 1987;13:434-40. 17. Cameron JA. The effect of ultrasonic endodontics on the temperature of the root canal wall. J Endodon 1988;14:554-9.
The Way It Was In Dodge City, Kansas, in 1875 about 82% of the population was male and about half the men were between the age of 20 and 29 (J Hist Med 46:463). No wonder there was so much feudin', fightin' and fussin'.
Cosby Newell
