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Effect of sonic versus ultrasonic instrumentation on canal preparation
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Printed m U S.A 15. No 6 J,c'~t 1989
SCIENTIFIC ARTICLES Effect of Sonic versus Ultrasonic Instrumentation on Canal Preparation Abdulla S. Yahya, BDS, MS, and Mahmoud E. EIDeeb, BDS, MS
~ a) s. ()nt, is bx lilt ~ ibralor.~ motion of the instru mt,nl ~ hich x~hen nlo~cd up and down ill Ihc r(x)t c;,lna[ ~ill ahrade tile tool canal ~alls. ('a~ itation and ;.lcouslK" slreeaming art` other prolx'rlies of ultrasound (14). ('a~ itatiun is tile formation of cavitit,s ill tilt, liquid and Iht,ir suh~'quent collapst,, which is ;icconlplisht,d h~ inlt,n~ h.~drat, lic shrieks strong t,nough to dt,slro', rnetal obiecls. Tile cax ilalion ill tile root canal, as clalimcd h~ Martin and ( ' u n n i n g h a m . was silmvn not to take place x~tlen lilt, ('ax i-I(ndo unit x~as used (14), W i l i l tilt, l{nac u l l r a m n i c s)slenl, c';.ixilalion can IX" gcnt,ralt`d; htmcvt,r, it is d o u b l f u l if it pla)s all imlx)rtanl rdt` ill inslrunlentation ( 15 l. Acou*,tic strt`aming is lilt" rapid movt`nlcnl of tluid particles ill xurtex-Iikt, motion aix)tlt a vii+rating ohiect. Atlnlad el al. (1-1- l f+) denlonstralcd tilt, pri~.iuclion of acoustic slreaming ~ i t l l I'x)til tilt" ('a~i-l{ndo and lilt, l{n:lc u l l r a m n i c de~ice~,. l h c ) condudt,d ih:,t the l)PC of irrigating v~lulion u.',~d. ~.ls ~wll as the gt`neralccd streaming, c;.in pn~lucc significantl)
The instrumentation time, and the resulting root canal angulation change and shape after using ultrasonic, sonic, and hand instrumentation techniques were studied in the mesial canals of 55 extracted human mandibular first and second molars. After instrumentation, the roots were sectioned horizontally in the apical, middle, and coronal thirds and evaluated for shape, mesial and distal canal widths, and canal diameter. MM3000 and hand were significantly faster than the other techniques (p < 0.005). MM3000 resulted in less angulation change than the Enac (p < 0.005). Hand instrumentation was judged to have given the best shape (p < 0.01).
clt'allt,r lOtit canals+
Pt,dicord t`t al, (17)c'oml+art`d instrutnt,ntatitm time and lilt" s l l a l , of tht` canal aflcr instrtinlcnlalion x~ith all ultrasonic dt`~ it-co <('a~ i - l m d o l and Iland inslrunlccnls, t "itrasa)nic instrun l c n l a l i o n relx)rlt,dl) pn~Juccd lllorc irrt,gulari) sllalt-tt camils ill the middle and c-ortmal thirds+ l land instltinlcntation was also signilicanll) tastt,r titan ultrasonic" inslrunlcnlation. \Valsh (i14) n.'ix)rled no ,,ignifk'ant difft`rcilcc.s rt,garding canal size and shal x" ~ ht,n lit, compart,d tilt, l{nac ullrasonic' inslrumr,hi ~dtll hand i n s l r u n l e n t a l i o n . . , \ n t ) l h t ' r Stl.ld} (lc)} shinned that ullramnic" inslrunlentation aplx'ars to Ix." cctl]cieilt iiild vile for silaping curxt`d canals. I~ut c;.inal Shal. ~as not t,~alu;iit`d. Wdlt,r t`l at. {2()) ,,lllmed Ihat uhrasonicalion is a u~-i'ul adjunct Io eenth~tonlic debridcnlcnl tx)til ill tiinc and etlMeency. Rob noids t,l all. ( 21 ) t,~ aluatt,d instrumented c'urx ed canals for rcnlaining li,~sue and dt,bris, as ~wll as prcctlt,ntin and dentin i't'nloval ahmg the canal walls. +lht`b shinned tland instrumentation IO Ix.. nlort` eett"t`cli~t` than Iht` l{ndo.~lar 5 ;.uld ('avi-l{ntlo tlt,~ ices ill tt,rlns of increasing canal si/ee, removing predcntin and tlt,hris, and planing canal ~ail% Rc'~ it`x~ of lilt: literature shm~+ed a lack i)t sludic',i c-onlparing the different sonic and u l l r a m n i c tcchniqut,s as Io their t`ffecls on canal sllalX', l h i s studb compart,d runic I.MM3(RI(), l{ndoSt;.ir 51 and ullra~mic I('a~i-l{ndo, l';nac) devicc.'s ~dth
Even though inslrunlentation is not dircctlb rt,lalcd to tilling Iht, canal, tile silalk" gi~ t,n It) tile canal during cnlargccnlt,nl is vitall) imlk~rtant lu lilt" tlualil) of ohturation of l i l t canal ( 1, 2). Nt,w l')rt~itlt-ts and illstrtlnlt`nts art` aplx'aring x~+l+ic-tlclaim to m a b : endt~hmlic instrunlt,lll;,llkin N~Ih i].ister ;,ind Ix'ttt,r than more con~ cnlional treatment. l ilt,~ ne~,, dc~iccs rllusl bc criticall.~ t,~aluatt,d Ix'fore the) are rt,conlmt,ndt,d to tht, dt,ntal c o n l n l u n i t % . R K ' t l n l a n (,~) ~,~,;.ls tilt, first to l'ccl'K)rl o n using uitrcimnics ill cndodonlics it1 1957. Marlin and ('unningham did a st`rit,s of sttidics (4.5, ()--121 l'rtllll 197s to 1982 on ultrasound and its applications ill ench~dontics ~ hich It,ad It) lile commercial production of tile ('a~i-i{ndo .,,;)slcm ill 19142 as the first uilra.~mic instrunlt,nlation unit, The ('a~il-ndo {1., i). ('aulk. l)i~ision of lX'ntspl) Intl,. Milthrd, [)I.) anti l{nac (()sada Hcciric ('o., Inc., I.os ,,%ngelcs, (".X) s)slemS x~ilich i.l.~ tlllr;i~onic cnt,rg~ to eenlargt, lilt, root canal and tilt, l{ndoSlar 5 (S.vntcx I)ental Pn~.tucts. Inc.. %allc.~ i o r g e , I>.X) and I%,i.~|.t(){R) (Medidcnla Intl. ('o., \ g t ~ l s i d c , N ' l ) ~shicll use ~xmic ~ibrator 3 cnt,rg~ art` :.lnlong ttle~, nc~', devices. Adv(x:ales of t h e ~ syslems claim that file instrumentation timt, ix significanll) dcc-rt,a',;t`d (4, 5, 1.t1, tile canal is dt,brided Ix'tier If,. 7), t~acteria are killt,d rt,adily (F,-I()), ;,ind Iht,re is It,~s tx~StOlx:ralive tli~'omf~wl (11. 12). I h c ultrasunic energ) is utili/cd Io ell,an and sllalx." rool canals, rcnlo~ t, debris, and disinfecl all in ont, olx'ralion. l h i s is accomplishccd ill different
lland i n s t r u n l c n t a l i o n in tt,lnls o f sllalk" o f lilt" c;.inai, t-h;.ingc
hi Ihcc curx aturc of tilt, canal, and tile in,,trunlc.nlalion linlc',
235
236
Journal of Endodontics
Yahya and EIDeeb
MATERIALS AND METHODS
Selection and Preparation of Test Teeth Access openings were made in a collection of extracted human mandibular first and second molars. Radiographs were taken with a # l0 file in the mesial canals to confirm that the mesial canals (traced by the files) did not join at the apex. Only teeth with separate mesiobuccal and mesiolingual canals were considered acceptable. One-hundred ten (110) mesial canals of 55 molars were selected for instrumentation. Teeth were embedded in clear plastic casting resin and a groove was cut in the resin on the buccal side for orientation. Using a #10 or #15 K-Flex file inserted into one mesial canal and the X-ray beam directed at right angles to the buccal side of the resin block, working lengths were measured and recorded for each mesial canal (0.5 to 1 m m short of the radiographic apex). Separate radiographs were taken for each canal. The canals were ordered according to degree of curvature and randomly assigned to the following instrumentation techniques: group 1, MM3000; G r o u p 2, Cavi-Endo; group 3, Endostar 5; group 4, Enac; and group 5, hand.
these two lines formed an angle which could be measured with a protractor (25). By recording and comparing the measured angles of the canal in each set of pre- and postinstrumentation radiographs, any change in the original angulation of the canal such as straightening of the curvature could be noticed (Fig. 1).
Sectioning of the Mesial Roots and Measurements of Minimal Remaining Root Thickness and Maximum Canal Diameter The apices of the specimens were ground down to the working lengths. After this, each specimen was sectioned using a sectioning disc on a lathe at the apical, middle, and the coronal thirds. This yielded three sections for evaluation of the canal shape in each instrumented root canal. Each crosssection was examined using a microscope with a camera lucida attachment at a magnification of x20, and outlines were carefully traced onto a piece of paper. The tracings were used to record measurements of minimal remaining root thickness from the canal to the root surfaces in both mesial and distal directions and also for measuring the mesiodistal canal diameter (Fig. 2).
Canal Instrumentation With hand instrumentation, the canals were filed to a #25 with K-Flex files 0.5 to 1.0 m m from the radiographic apex. The canals were irrigated with 1 ml of water between file sizes and the coronal two thirds were flared using Gates Glidden # 1 and 2 burs. The instrumentation and flaring for the sonic and ultrasonic groups was done as recommended by each manufacturer (22-24). The canals were first enlarged up to # 15 using K-Flex files and hand instrumentation. Canal instrumentation was considered complete when a #30 Hedstrom file could be inserted to working length, and the appropriate flaring technique for each group was done as per the manufacturer's recommendations (22-24).
Measurement of Instrumentation Time A stopwatch was used to record the instrumentation time for each canal. The measurement includes the time elapsed from the use of a # 15 file to the final flaring for all of the techniques. All files for all of the techniques were discarded after use in two canals. Instances of lost length, broken files, and other procedural problems were recorded.
FIG 1. Diagram illustrating method of measuring pre- and postinstrumentation curvatures.
DISTAL Angulation Change Measurements After enlarge[nent of all of the canals, a master apical file radiograph was taken for each canal with the same angulation which was used for the length determination radiograph. Using tracing paper and a pencil, an outline of the mesial root with a file within was traced for each radiograph. The file was used as an indicator of canal direction and orientation throughout the length of the root. The vertical angulation of each canal in each radiograph was determined by tracing a straight line through the outline of the file in the coronal root one third, and another straight line through the outline of the file in the apical 3 to 4 m m of the canal. The intersection of
~'~MB) ~.(Canal Outline . ) / ~~~'Canal ~L~I~Wid~~h) ~_ ~ )
~
~
NESIAJ.
F~a 2. Tracing of root and canal outlines that was used for recording minimal remaining root thickness and maximum canal diameter.
Sonic versus Ultrasonic Instrumentation
Vol. 15, No. 6, June 1989
Assessment of Canal Shape Three examiners, two endodontists and a second-year graduate student, were asked to judge the drawings of all of the specimens. None of the examiners knew which instrumentation technique had been used in each canal. The tracings were evaluated for canal shape (rated as round, oval, or irregular) at the apical, middle, and coronal levels.
237
are shown in Table 4. ANOVA was used to compare the different techniques with each other at the different levels. No significant differences were found in canal diameter among the instrumentation groups at the different levels. When the different instrumentation groups were compared with the uninstrumented controls, a statistically significant difference was found (p < 0.01).
Canal Shape Statistical Analysis All results were submitted for statistical analysis. Unpaired t tests were used to evaluate the instrumentation times, change in angulation, and measured distances from the canal walls to the root surfaces. One-way analysis of variance (ANOVA) test was used to compare the different techniques. MannWhitney Utest was used for intergroup comparisons regarding the shape of the canal.
The incidence (and percentages) of canal shapes in the different groups are shown in Table 5. Mann-Whitney U test was used for comparisons among the groups. In general, there was no significant difference regarding which method produced the best shape at the apical and middle thirds. At the coronal level, hand instrumentation was significantly better than all of the different instrumentation techniques (p < 0.01). There were no irregular shapes produced by hand instrumentation at the coronal level (Figs. 4 and 5).
RESULTS
Procedural Problems Instrumentation Time The means and ranges of instrumentation time for the different techniques are shown in Table 1. A N O V A showed a statistically significant difference (p < 0.05). Unpaired t tests were used for statistical comparisons. Hand instrumentation and MM3000 were significantly faster than the other techniques (p < 0.005).
Canal Angulation Change The means and ranges of the change in canal angulation for all of the techniques are presented in Table 2. An example of pre- and postinstrumentation radiographs that were used to measure change in canal curvature are shown in Fig. 3. Instrumentation using the Enac ultrasonic instrument resulted in t h e highest mean change in angulation (16 degrees), while MM3000 resulted in the least amount of straightening of canals (8 degrees). A N O V A and t tests were used for statistical comparisons of the angulation change among the instrumentation groups. The only significant difference was between MM3000 and Enac (p < 0.005).
Measurement of Minimal Remaining Mesial and Distal Root Thickness
The incidence of procedural problems during instrumentation was low. There were four perforations, two ledgings, and one broken instrument. There was no trend for these to occur in any particular instrumentation group.
TABLE 1. Instrumentation time Technique
Mean 4- SEM
MM3000 Cavi-Endo EndoStar 5 Enac Hand
4.13 5.68 5.03 5.03 4.25
_ 0.327 - 0.402 4- 0.310 4- 0.437 4- 0.203
Range (min) 2.2-8.4 3.0-10.1 3.2-8.0 2.5-10.4 2.4-5.7
TABLE 2. Postinstrumentation angulation change Technique MM3000 Cavi-Endo EndoStar 5 Enac Hand
Mean + SEM 7.6 11.9 10.3 15.4 10.7
+ 1.329 + 1.819 4- 1.988 + 2.371 _+ 1.722
Range (oc) 0-21 0-23 0-32 0-37 0-28
Table 3 shows the means and ranges of the m i n i m u m remaining mesial and distal distances from the canal wall to the root surface in the apical, middle, and coronal one thirds of all groups. ANOVA showed no statistically significant difference among the instrumentation groups at the three levels. All instrumentation groups were, however, significantly different from the uninstrumented controls (p < 0.01).
Measurement of Maximum Canal Diameter The means of the m a x i m u m mesiodistal canal diameters at the apical, middle, and coronal thirds of all of the groups
FIG 3. Pre- and postinstrumentation radiographs for measuring change in canal angulation (a more curved example).
238
Yahya and EIDeeb
Journal of Endodontics
TAeLE 3. M e a n + standard error: minimal mesial and distal tooth structure at different levels Apical Technique
Middle
Mesial (mm)
MM3000 Cavi-Endo EndoStar 5 Enac Hand Control
0.78 0.72 0.75 0.59 0.62 0.91
Distal (mm)
___0.05 + 0.06 _+ 0.04 _+ 0.06 --_ 0.05 _+ 0.11
0.68 0.71 0.77 0,70 0,64 0.71
Mesial (mm)
-+ 0.5 _+ 0.04 + 0.04 4- 0.04 4- 0.05 _+ 0.07
0.98 0.92 1.07 0.94 0.99 1.14
TABLE 4. Mean --+ standard error of mean of the maximum canal diameter at different levels Technique MM3000 Cavi-Endo EndoStar 5 Enac Hand Control
Apical (mm) 0.55 0.63 0.48 0.58 0.53 0.32
-+ 0.07 _+ 0.06 _+ 0.04 _+ 0.05 -+ 0.05 + 0.02
Middle (mm) 0.62 0.66 0.59 0.69 0.58 0.39
-+ 0.03 _+ 0.04 _4-0.02 _+ 0.05 + 0.02 _+ 0.05
Coronal (ram) 0.80 0.85 0.80 0.87 0.91 0.50
_+ 0.04 + 0.04 + 0.03 _+ 0.04 _+ 0.02 + 0.06
DISCUSSION In the present study instrumentation time, the shape given to the root canal during instrumentation, and the change in the curvature of the canal were evaluated comparing the different sonic and ultrasonic instruments available with hand instrumentation and with each other. The sonic instruments used were MM3000 and EndoStar 5 and the ultrasonic instruments used were the Enac and Cavi-Endo. In general, instrumentation time was greatly influenced by the nature of the canal being instrumented. During instrumentation of straight or short canals, a #30 Hedstrom file was easily advanced to working length following the use of #15 files. These canals were instrumented in minimal time (2.09 min). As the canal curvature and/or length increased, the use of progressive sizes of files was necessary to achieve canal enlargement to working length equivalent to a #30 Hedstrom file. These instances occurred regardless of the technique used, except with hand instrumentation, where sequential use of instrument sizes was generally needed to accomplish the desired canal enlargement. Hand and MM3000 instrumentations were significantly faster than the other techniques (p < 0.005). This finding is contrary to the claims of the manufacturers of the other instruments and some investigators (4, 5, 18). In the first two studies (4, 5) the authors used 4-mm root sections that had the original canal e.nIarged by a #557 bur before instrumentation was begun. ~he method used in the present study to compare instrumentation times is more applicable to a true clinical situation, and so it is a truer comparison of the real time involved with each technique. In the third study, there was no flaring done to the middle and coronal third portions of the canal. It agrees with the findings of Pedicord et al (17); however, the mean instrumentation time in that study was higher than that of the present study, which might be due to the differences between operators.
Coronal Distal (mm)
_+ 0.12 _+ 0.06 _+ 0.05 _+ 0.04 4- 0.03 _+ 0.09
0.84 0.80 0.91 0.73 0.72 1.01
+ 0.06 -+ 0.05 _+ 0.05 _+ 0.05 _+ 0.04 _+ 0.05
Mesial (mm) 1.29 1.17 1.27 1.18 1.18 1.32
_+ 0.05 _+0.05 _+ 0.07 + 0.05 4- 0.03 _+ 0.11
Distal (ram) 0.88 0.66 0.91 0.66 0.81 1.11
_ 0.07 _+ 0.05 ___0.06 _+ 0.06 _+ 0.08 _+ 0.12
Angulation change (canal straightening) occurred in all of the different techniques. Enac ultrasonic instrument resulted in the highest mean change in angulation (16 degrees), while MM3000 resulted in the least amount of straightening of canals (8 degrees). When the different techniques were compared with each other, there were no statistical significant differences, except between MM3000 and Enac (p < 0.005). The measured minimal mesial and distal root widths and maximum canal diameter measurements of the cross-sectioned root tracings at the three levels were done to see if the direction and/or amount of shifting of the canal position varied among techniques, and to evaluate the size of the instrumented canal. All of the different techniques showed less remaining tooth structure on both sides of the canal and increased canal diameters when compared with the control group, which is an evidence of dentin removal. But when the different groups were compared with each other, there was no statistically significant difference at any of the three levels. The judgments of the cross-sectional drawings of instrumented canal shape showed no statistically significant differences among any of the different groups at the apical and middle levels, but at the coronal level, hand instrumentation was significantly better (produced more round canals) than any of the other techniques of instrumentation (p < 0.01). Although all of the techniques had some irregular shapes at all three levels, hand instrumentation did not show any irregular shapes at the coronal level. This finding is probably due to the use of Gates Glidden drills in flaring of the coronal portion of the canals in the hand group. CONCLUSIONS 1. Instrumentation using MM3000 and hand were significantly faster than the other techniques (p < 0.005). 2. The only significant difference in the angulation change was between MM3000 and Enac; MM3000 produced fewer changes (p < 0.005). 3. There was no significant difference in the working length change. 4. There was no statistically significant difference between groups regarding the size or change in mesiodistal canal location. 5. Hand instrumentation resulted in the best shape at the coronal level (p < 0.01). There was no statistically significant difference among the other groups at the different levels. Dr. Yohya is a former graduate student and presently a lecturer of endodontics, Department of Restorative Dentistry, Dental School, King Saud Uni-
Vol. 15, No. 6, June 1989
Sonic versus Ultrasonic Instrumentation
239
TABLE 5. Incidence and (percentage) of canal shape in different groups at *different levels Apical Technique
Round MM3000 Cavi-Endo EndoStar 5 Enac Hand Control
Middle
Coronal
No. 20 20 20 20 20 10
5 1 3 4 3 2
(25) (5) (15) (20) (15) (20)
Oval 11 13 12 11 14 7
(55) (65) (60) (55) (70) (70)
Irregular 4 6 5 5 3 1
Round
(20) (30) (25) (25) (15) (10)
4 2 1 3 7 3
(20) (10) (5) (15) (35) (30)
13 15 15 13 11 7
(65) (75) (75) (65) (55) (20)
Irregular 3 3 4 4 2 0
(15) (15) (20) (20) (10) (0)
Round 3 6 1 3 14 5
(15) (30) (5) (15) (70) (50)
Oval 25 9 13 15 6 4
(75) (45) (65) (75) (30) (40)
Irregular 2 5 6 2 0 1
(10) (25) (30) (10) (0) (10)
References
I i
84
L~NGUA ~L
1. Schilder H. Cleaning and shaping the root canal. Dent Clin North Am 1974;4:269-96. 2. Heuer M. The biomechanics of endodontic therapy. Dent Clin North Amer 1963;6:341-59. 3. Richman MJ. The use of ultrasonic in root canal therapy and root resection. J Dent Med 1957;12:12-8. 4. Martin H, Cunningham W, Norris JP. A quantitative comparison of the ability of diamond and K-type files to remove dentin. Oral Surg 1980;50:5668. 5. Martin H, Cunnigham W, Norris JP, Cotton W. Ultrasonic versus hand filing of dentin: a quantitative study. Oral Surg 1980;49:79-81. 6. Cunningham W, Martin H, Forrest W. Evaluation of root canal debridement by endosonic synergistic system. Oral Surg 1982;53:401-4. 7. Martin H, Cunningham W. A scanning electron microscope evaluation of root canal debridement with endosonic synergistic system. Oral Surg 1982;53:527-31. 8. Cunningham W, Joseph S. Effect of temperature on the bacteriocidal action of sodium hypochlorite endodontic irrigant. Oral Surg 1980;50:569-71. 9. Cunningham W, Martin H, Pellen G, Stoops D. A comparison of antimicrobial effectiveness of endosonic and hand root canal therapy. Oral Surg 1982;54:238-41. 10. Martin H. Ultrasonic disinfection of the root canal Oral Surg 1976;42:92-9. 11. Martin H, Cunningham W. An evaluation of post-operative pain incidence following endosonic and conventional root canal therapy. Oral Surg 1982;54:74-6. 12. Martin H, Cunningham W. The effect of endosonic and hand manipulation on the amount of root canal material extruded. Oral Surg 1982;53:6113. 13. The Dentsply| | Cavi-Endor Unit. Form No. 3607-D, Copyright 1984, Dentsply International. 14. Ahmad M, Pitt Ford TR, Crum LA. Ultrasonic debridement of root canals: an insight into the mechanisms involved. J Endodon 1987;13:93-101. 15. Ahmad M, Pitt Ford TR, Crum LA. Acoustic cavitation and its implications an ultrasonic root canal debridement [Abstract 14]. J Endodon 1987;13:131. 16. Ahmad M, Pitt Ford TR, Crum LA. Ultrasonic debridement of root canals: streaming and its possible role. J Endodon 1987;13:490-9. 17. Pedicord D, EIDeeb ME, Messer HH. Hand versus ultrasonic instrumentation: its effect on canal shape and instrumentation time. J Endodon 1986;12:375-81. 18. Walsh CL. A comparison of hand and ultrasonic endodontic instrumentation. Master's Thesis, University of Minnesota, 1987. 19. 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 Endedon 1983;9:327-31. 20. Weller NR, Brady JM, Bernier WE. Efficacy of ultrasonic cleaning. J Endodon 1980;6:740-3. 21. Reynolds MR, Madison S, Walton RE, Krell KV, Rittman BRJ. An in vitro histological comparison of the step-back, sonic, and ultrasonic instrumentation techniques in small, curved root canals. J Endodon 1987;13:307-14. 22. Osada Er,ac Ultra-Endo Instrument System (instructions), Osada Electric Co., CNO8504-30. 23. Sonic Air MM3000 Endo System (instructions), Medidenta International, Inc. 24. The Endostar 5 Sonic System, Syntex Dental Products, Valley Forge, PA. 25. Schneider S. A comparison of canal preparations in straight and curved root canals. Oral Surg 1971 ;32:271-5.
BUCCAL
FiG 4. Tracing and photograph of postinstrumentation cross-section illustrating canal shape. Left canal is from the hand instrumentation group, while the right is from the Enac group.
HESIM.
BUCC ~AL
Oval
L N IGUAL
FIG 5. Tracing and photograph of postinstrumentation cross-section illustrating canal shape (note stripping perforation). The left and right canals are from the Cavi-Endo and EndoStar 5 groups, respectively. versity, Riyadh, Saudi Arabia. Dr. EIDeeb is associate professor and director of the Graduate Program, Department of Endodontics, School of Dentistry, University of Minnesota, Minneapolis, MN.
Voi
Printed m U S.A 15. No 6 J,c'~t 1989
SCIENTIFIC ARTICLES Effect of Sonic versus Ultrasonic Instrumentation on Canal Preparation Abdulla S. Yahya, BDS, MS, and Mahmoud E. EIDeeb, BDS, MS
~ a) s. ()nt, is bx lilt ~ ibralor.~ motion of the instru mt,nl ~ hich x~hen nlo~cd up and down ill Ihc r(x)t c;,lna[ ~ill ahrade tile tool canal ~alls. ('a~ itation and ;.lcouslK" slreeaming art` other prolx'rlies of ultrasound (14). ('a~ itatiun is tile formation of cavitit,s ill tilt, liquid and Iht,ir suh~'quent collapst,, which is ;icconlplisht,d h~ inlt,n~ h.~drat, lic shrieks strong t,nough to dt,slro', rnetal obiecls. Tile cax ilalion ill tile root canal, as clalimcd h~ Martin and ( ' u n n i n g h a m . was silmvn not to take place x~tlen lilt, ('ax i-I(ndo unit x~as used (14), W i l i l tilt, l{nac u l l r a m n i c s)slenl, c';.ixilalion can IX" gcnt,ralt`d; htmcvt,r, it is d o u b l f u l if it pla)s all imlx)rtanl rdt` ill inslrunlentation ( 15 l. Acou*,tic strt`aming is lilt" rapid movt`nlcnl of tluid particles ill xurtex-Iikt, motion aix)tlt a vii+rating ohiect. Atlnlad el al. (1-1- l f+) denlonstralcd tilt, pri~.iuclion of acoustic slreaming ~ i t l l I'x)til tilt" ('a~i-l{ndo and lilt, l{n:lc u l l r a m n i c de~ice~,. l h c ) condudt,d ih:,t the l)PC of irrigating v~lulion u.',~d. ~.ls ~wll as the gt`neralccd streaming, c;.in pn~lucc significantl)
The instrumentation time, and the resulting root canal angulation change and shape after using ultrasonic, sonic, and hand instrumentation techniques were studied in the mesial canals of 55 extracted human mandibular first and second molars. After instrumentation, the roots were sectioned horizontally in the apical, middle, and coronal thirds and evaluated for shape, mesial and distal canal widths, and canal diameter. MM3000 and hand were significantly faster than the other techniques (p < 0.005). MM3000 resulted in less angulation change than the Enac (p < 0.005). Hand instrumentation was judged to have given the best shape (p < 0.01).
clt'allt,r lOtit canals+
Pt,dicord t`t al, (17)c'oml+art`d instrutnt,ntatitm time and lilt" s l l a l , of tht` canal aflcr instrtinlcnlalion x~ith all ultrasonic dt`~ it-co <('a~ i - l m d o l and Iland inslrunlccnls, t "itrasa)nic instrun l c n l a l i o n relx)rlt,dl) pn~Juccd lllorc irrt,gulari) sllalt-tt camils ill the middle and c-ortmal thirds+ l land instltinlcntation was also signilicanll) tastt,r titan ultrasonic" inslrunlcnlation. \Valsh (i14) n.'ix)rled no ,,ignifk'ant difft`rcilcc.s rt,garding canal size and shal x" ~ ht,n lit, compart,d tilt, l{nac ullrasonic' inslrumr,hi ~dtll hand i n s l r u n l e n t a l i o n . . , \ n t ) l h t ' r Stl.ld} (lc)} shinned that ullramnic" inslrunlentation aplx'ars to Ix." cctl]cieilt iiild vile for silaping curxt`d canals. I~ut c;.inal Shal. ~as not t,~alu;iit`d. Wdlt,r t`l at. {2()) ,,lllmed Ihat uhrasonicalion is a u~-i'ul adjunct Io eenth~tonlic debridcnlcnl tx)til ill tiinc and etlMeency. Rob noids t,l all. ( 21 ) t,~ aluatt,d instrumented c'urx ed canals for rcnlaining li,~sue and dt,bris, as ~wll as prcctlt,ntin and dentin i't'nloval ahmg the canal walls. +lht`b shinned tland instrumentation IO Ix.. nlort` eett"t`cli~t` than Iht` l{ndo.~lar 5 ;.uld ('avi-l{ntlo tlt,~ ices ill tt,rlns of increasing canal si/ee, removing predcntin and tlt,hris, and planing canal ~ail% Rc'~ it`x~ of lilt: literature shm~+ed a lack i)t sludic',i c-onlparing the different sonic and u l l r a m n i c tcchniqut,s as Io their t`ffecls on canal sllalX', l h i s studb compart,d runic I.MM3(RI(), l{ndoSt;.ir 51 and ullra~mic I('a~i-l{ndo, l';nac) devicc.'s ~dth
Even though inslrunlentation is not dircctlb rt,lalcd to tilling Iht, canal, tile silalk" gi~ t,n It) tile canal during cnlargccnlt,nl is vitall) imlk~rtant lu lilt" tlualil) of ohturation of l i l t canal ( 1, 2). Nt,w l')rt~itlt-ts and illstrtlnlt`nts art` aplx'aring x~+l+ic-tlclaim to m a b : endt~hmlic instrunlt,lll;,llkin N~Ih i].ister ;,ind Ix'ttt,r than more con~ cnlional treatment. l ilt,~ ne~,, dc~iccs rllusl bc criticall.~ t,~aluatt,d Ix'fore the) are rt,conlmt,ndt,d to tht, dt,ntal c o n l n l u n i t % . R K ' t l n l a n (,~) ~,~,;.ls tilt, first to l'ccl'K)rl o n using uitrcimnics ill cndodonlics it1 1957. Marlin and ('unningham did a st`rit,s of sttidics (4.5, ()--121 l'rtllll 197s to 1982 on ultrasound and its applications ill ench~dontics ~ hich It,ad It) lile commercial production of tile ('a~i-i{ndo .,,;)slcm ill 19142 as the first uilra.~mic instrunlt,nlation unit, The ('a~il-ndo {1., i). ('aulk. l)i~ision of lX'ntspl) Intl,. Milthrd, [)I.) anti l{nac (()sada Hcciric ('o., Inc., I.os ,,%ngelcs, (".X) s)slemS x~ilich i.l.~ tlllr;i~onic cnt,rg~ to eenlargt, lilt, root canal and tilt, l{ndoSlar 5 (S.vntcx I)ental Pn~.tucts. Inc.. %allc.~ i o r g e , I>.X) and I%,i.~|.t(){R) (Medidcnla Intl. ('o., \ g t ~ l s i d c , N ' l ) ~shicll use ~xmic ~ibrator 3 cnt,rg~ art` :.lnlong ttle~, nc~', devices. Adv(x:ales of t h e ~ syslems claim that file instrumentation timt, ix significanll) dcc-rt,a',;t`d (4, 5, 1.t1, tile canal is dt,brided Ix'tier If,. 7), t~acteria are killt,d rt,adily (F,-I()), ;,ind Iht,re is It,~s tx~StOlx:ralive tli~'omf~wl (11. 12). I h c ultrasunic energ) is utili/cd Io ell,an and sllalx." rool canals, rcnlo~ t, debris, and disinfecl all in ont, olx'ralion. l h i s is accomplishccd ill different
lland i n s t r u n l c n t a l i o n in tt,lnls o f sllalk" o f lilt" c;.inai, t-h;.ingc
hi Ihcc curx aturc of tilt, canal, and tile in,,trunlc.nlalion linlc',
235
236
Journal of Endodontics
Yahya and EIDeeb
MATERIALS AND METHODS
Selection and Preparation of Test Teeth Access openings were made in a collection of extracted human mandibular first and second molars. Radiographs were taken with a # l0 file in the mesial canals to confirm that the mesial canals (traced by the files) did not join at the apex. Only teeth with separate mesiobuccal and mesiolingual canals were considered acceptable. One-hundred ten (110) mesial canals of 55 molars were selected for instrumentation. Teeth were embedded in clear plastic casting resin and a groove was cut in the resin on the buccal side for orientation. Using a #10 or #15 K-Flex file inserted into one mesial canal and the X-ray beam directed at right angles to the buccal side of the resin block, working lengths were measured and recorded for each mesial canal (0.5 to 1 m m short of the radiographic apex). Separate radiographs were taken for each canal. The canals were ordered according to degree of curvature and randomly assigned to the following instrumentation techniques: group 1, MM3000; G r o u p 2, Cavi-Endo; group 3, Endostar 5; group 4, Enac; and group 5, hand.
these two lines formed an angle which could be measured with a protractor (25). By recording and comparing the measured angles of the canal in each set of pre- and postinstrumentation radiographs, any change in the original angulation of the canal such as straightening of the curvature could be noticed (Fig. 1).
Sectioning of the Mesial Roots and Measurements of Minimal Remaining Root Thickness and Maximum Canal Diameter The apices of the specimens were ground down to the working lengths. After this, each specimen was sectioned using a sectioning disc on a lathe at the apical, middle, and the coronal thirds. This yielded three sections for evaluation of the canal shape in each instrumented root canal. Each crosssection was examined using a microscope with a camera lucida attachment at a magnification of x20, and outlines were carefully traced onto a piece of paper. The tracings were used to record measurements of minimal remaining root thickness from the canal to the root surfaces in both mesial and distal directions and also for measuring the mesiodistal canal diameter (Fig. 2).
Canal Instrumentation With hand instrumentation, the canals were filed to a #25 with K-Flex files 0.5 to 1.0 m m from the radiographic apex. The canals were irrigated with 1 ml of water between file sizes and the coronal two thirds were flared using Gates Glidden # 1 and 2 burs. The instrumentation and flaring for the sonic and ultrasonic groups was done as recommended by each manufacturer (22-24). The canals were first enlarged up to # 15 using K-Flex files and hand instrumentation. Canal instrumentation was considered complete when a #30 Hedstrom file could be inserted to working length, and the appropriate flaring technique for each group was done as per the manufacturer's recommendations (22-24).
Measurement of Instrumentation Time A stopwatch was used to record the instrumentation time for each canal. The measurement includes the time elapsed from the use of a # 15 file to the final flaring for all of the techniques. All files for all of the techniques were discarded after use in two canals. Instances of lost length, broken files, and other procedural problems were recorded.
FIG 1. Diagram illustrating method of measuring pre- and postinstrumentation curvatures.
DISTAL Angulation Change Measurements After enlarge[nent of all of the canals, a master apical file radiograph was taken for each canal with the same angulation which was used for the length determination radiograph. Using tracing paper and a pencil, an outline of the mesial root with a file within was traced for each radiograph. The file was used as an indicator of canal direction and orientation throughout the length of the root. The vertical angulation of each canal in each radiograph was determined by tracing a straight line through the outline of the file in the coronal root one third, and another straight line through the outline of the file in the apical 3 to 4 m m of the canal. The intersection of
~'~MB) ~.(Canal Outline . ) / ~~~'Canal ~L~I~Wid~~h) ~_ ~ )
~
~
NESIAJ.
F~a 2. Tracing of root and canal outlines that was used for recording minimal remaining root thickness and maximum canal diameter.
Sonic versus Ultrasonic Instrumentation
Vol. 15, No. 6, June 1989
Assessment of Canal Shape Three examiners, two endodontists and a second-year graduate student, were asked to judge the drawings of all of the specimens. None of the examiners knew which instrumentation technique had been used in each canal. The tracings were evaluated for canal shape (rated as round, oval, or irregular) at the apical, middle, and coronal levels.
237
are shown in Table 4. ANOVA was used to compare the different techniques with each other at the different levels. No significant differences were found in canal diameter among the instrumentation groups at the different levels. When the different instrumentation groups were compared with the uninstrumented controls, a statistically significant difference was found (p < 0.01).
Canal Shape Statistical Analysis All results were submitted for statistical analysis. Unpaired t tests were used to evaluate the instrumentation times, change in angulation, and measured distances from the canal walls to the root surfaces. One-way analysis of variance (ANOVA) test was used to compare the different techniques. MannWhitney Utest was used for intergroup comparisons regarding the shape of the canal.
The incidence (and percentages) of canal shapes in the different groups are shown in Table 5. Mann-Whitney U test was used for comparisons among the groups. In general, there was no significant difference regarding which method produced the best shape at the apical and middle thirds. At the coronal level, hand instrumentation was significantly better than all of the different instrumentation techniques (p < 0.01). There were no irregular shapes produced by hand instrumentation at the coronal level (Figs. 4 and 5).
RESULTS
Procedural Problems Instrumentation Time The means and ranges of instrumentation time for the different techniques are shown in Table 1. A N O V A showed a statistically significant difference (p < 0.05). Unpaired t tests were used for statistical comparisons. Hand instrumentation and MM3000 were significantly faster than the other techniques (p < 0.005).
Canal Angulation Change The means and ranges of the change in canal angulation for all of the techniques are presented in Table 2. An example of pre- and postinstrumentation radiographs that were used to measure change in canal curvature are shown in Fig. 3. Instrumentation using the Enac ultrasonic instrument resulted in t h e highest mean change in angulation (16 degrees), while MM3000 resulted in the least amount of straightening of canals (8 degrees). A N O V A and t tests were used for statistical comparisons of the angulation change among the instrumentation groups. The only significant difference was between MM3000 and Enac (p < 0.005).
Measurement of Minimal Remaining Mesial and Distal Root Thickness
The incidence of procedural problems during instrumentation was low. There were four perforations, two ledgings, and one broken instrument. There was no trend for these to occur in any particular instrumentation group.
TABLE 1. Instrumentation time Technique
Mean 4- SEM
MM3000 Cavi-Endo EndoStar 5 Enac Hand
4.13 5.68 5.03 5.03 4.25
_ 0.327 - 0.402 4- 0.310 4- 0.437 4- 0.203
Range (min) 2.2-8.4 3.0-10.1 3.2-8.0 2.5-10.4 2.4-5.7
TABLE 2. Postinstrumentation angulation change Technique MM3000 Cavi-Endo EndoStar 5 Enac Hand
Mean + SEM 7.6 11.9 10.3 15.4 10.7
+ 1.329 + 1.819 4- 1.988 + 2.371 _+ 1.722
Range (oc) 0-21 0-23 0-32 0-37 0-28
Table 3 shows the means and ranges of the m i n i m u m remaining mesial and distal distances from the canal wall to the root surface in the apical, middle, and coronal one thirds of all groups. ANOVA showed no statistically significant difference among the instrumentation groups at the three levels. All instrumentation groups were, however, significantly different from the uninstrumented controls (p < 0.01).
Measurement of Maximum Canal Diameter The means of the m a x i m u m mesiodistal canal diameters at the apical, middle, and coronal thirds of all of the groups
FIG 3. Pre- and postinstrumentation radiographs for measuring change in canal angulation (a more curved example).
238
Yahya and EIDeeb
Journal of Endodontics
TAeLE 3. M e a n + standard error: minimal mesial and distal tooth structure at different levels Apical Technique
Middle
Mesial (mm)
MM3000 Cavi-Endo EndoStar 5 Enac Hand Control
0.78 0.72 0.75 0.59 0.62 0.91
Distal (mm)
___0.05 + 0.06 _+ 0.04 _+ 0.06 --_ 0.05 _+ 0.11
0.68 0.71 0.77 0,70 0,64 0.71
Mesial (mm)
-+ 0.5 _+ 0.04 + 0.04 4- 0.04 4- 0.05 _+ 0.07
0.98 0.92 1.07 0.94 0.99 1.14
TABLE 4. Mean --+ standard error of mean of the maximum canal diameter at different levels Technique MM3000 Cavi-Endo EndoStar 5 Enac Hand Control
Apical (mm) 0.55 0.63 0.48 0.58 0.53 0.32
-+ 0.07 _+ 0.06 _+ 0.04 _+ 0.05 -+ 0.05 + 0.02
Middle (mm) 0.62 0.66 0.59 0.69 0.58 0.39
-+ 0.03 _+ 0.04 _4-0.02 _+ 0.05 + 0.02 _+ 0.05
Coronal (ram) 0.80 0.85 0.80 0.87 0.91 0.50
_+ 0.04 + 0.04 + 0.03 _+ 0.04 _+ 0.02 + 0.06
DISCUSSION In the present study instrumentation time, the shape given to the root canal during instrumentation, and the change in the curvature of the canal were evaluated comparing the different sonic and ultrasonic instruments available with hand instrumentation and with each other. The sonic instruments used were MM3000 and EndoStar 5 and the ultrasonic instruments used were the Enac and Cavi-Endo. In general, instrumentation time was greatly influenced by the nature of the canal being instrumented. During instrumentation of straight or short canals, a #30 Hedstrom file was easily advanced to working length following the use of #15 files. These canals were instrumented in minimal time (2.09 min). As the canal curvature and/or length increased, the use of progressive sizes of files was necessary to achieve canal enlargement to working length equivalent to a #30 Hedstrom file. These instances occurred regardless of the technique used, except with hand instrumentation, where sequential use of instrument sizes was generally needed to accomplish the desired canal enlargement. Hand and MM3000 instrumentations were significantly faster than the other techniques (p < 0.005). This finding is contrary to the claims of the manufacturers of the other instruments and some investigators (4, 5, 18). In the first two studies (4, 5) the authors used 4-mm root sections that had the original canal e.nIarged by a #557 bur before instrumentation was begun. ~he method used in the present study to compare instrumentation times is more applicable to a true clinical situation, and so it is a truer comparison of the real time involved with each technique. In the third study, there was no flaring done to the middle and coronal third portions of the canal. It agrees with the findings of Pedicord et al (17); however, the mean instrumentation time in that study was higher than that of the present study, which might be due to the differences between operators.
Coronal Distal (mm)
_+ 0.12 _+ 0.06 _+ 0.05 _+ 0.04 4- 0.03 _+ 0.09
0.84 0.80 0.91 0.73 0.72 1.01
+ 0.06 -+ 0.05 _+ 0.05 _+ 0.05 _+ 0.04 _+ 0.05
Mesial (mm) 1.29 1.17 1.27 1.18 1.18 1.32
_+ 0.05 _+0.05 _+ 0.07 + 0.05 4- 0.03 _+ 0.11
Distal (ram) 0.88 0.66 0.91 0.66 0.81 1.11
_ 0.07 _+ 0.05 ___0.06 _+ 0.06 _+ 0.08 _+ 0.12
Angulation change (canal straightening) occurred in all of the different techniques. Enac ultrasonic instrument resulted in the highest mean change in angulation (16 degrees), while MM3000 resulted in the least amount of straightening of canals (8 degrees). When the different techniques were compared with each other, there were no statistical significant differences, except between MM3000 and Enac (p < 0.005). The measured minimal mesial and distal root widths and maximum canal diameter measurements of the cross-sectioned root tracings at the three levels were done to see if the direction and/or amount of shifting of the canal position varied among techniques, and to evaluate the size of the instrumented canal. All of the different techniques showed less remaining tooth structure on both sides of the canal and increased canal diameters when compared with the control group, which is an evidence of dentin removal. But when the different groups were compared with each other, there was no statistically significant difference at any of the three levels. The judgments of the cross-sectional drawings of instrumented canal shape showed no statistically significant differences among any of the different groups at the apical and middle levels, but at the coronal level, hand instrumentation was significantly better (produced more round canals) than any of the other techniques of instrumentation (p < 0.01). Although all of the techniques had some irregular shapes at all three levels, hand instrumentation did not show any irregular shapes at the coronal level. This finding is probably due to the use of Gates Glidden drills in flaring of the coronal portion of the canals in the hand group. CONCLUSIONS 1. Instrumentation using MM3000 and hand were significantly faster than the other techniques (p < 0.005). 2. The only significant difference in the angulation change was between MM3000 and Enac; MM3000 produced fewer changes (p < 0.005). 3. There was no significant difference in the working length change. 4. There was no statistically significant difference between groups regarding the size or change in mesiodistal canal location. 5. Hand instrumentation resulted in the best shape at the coronal level (p < 0.01). There was no statistically significant difference among the other groups at the different levels. Dr. Yohya is a former graduate student and presently a lecturer of endodontics, Department of Restorative Dentistry, Dental School, King Saud Uni-
Vol. 15, No. 6, June 1989
Sonic versus Ultrasonic Instrumentation
239
TABLE 5. Incidence and (percentage) of canal shape in different groups at *different levels Apical Technique
Round MM3000 Cavi-Endo EndoStar 5 Enac Hand Control
Middle
Coronal
No. 20 20 20 20 20 10
5 1 3 4 3 2
(25) (5) (15) (20) (15) (20)
Oval 11 13 12 11 14 7
(55) (65) (60) (55) (70) (70)
Irregular 4 6 5 5 3 1
Round
(20) (30) (25) (25) (15) (10)
4 2 1 3 7 3
(20) (10) (5) (15) (35) (30)
13 15 15 13 11 7
(65) (75) (75) (65) (55) (20)
Irregular 3 3 4 4 2 0
(15) (15) (20) (20) (10) (0)
Round 3 6 1 3 14 5
(15) (30) (5) (15) (70) (50)
Oval 25 9 13 15 6 4
(75) (45) (65) (75) (30) (40)
Irregular 2 5 6 2 0 1
(10) (25) (30) (10) (0) (10)
References
I i
84
L~NGUA ~L
1. Schilder H. Cleaning and shaping the root canal. Dent Clin North Am 1974;4:269-96. 2. Heuer M. The biomechanics of endodontic therapy. Dent Clin North Amer 1963;6:341-59. 3. Richman MJ. The use of ultrasonic in root canal therapy and root resection. J Dent Med 1957;12:12-8. 4. Martin H, Cunningham W, Norris JP. A quantitative comparison of the ability of diamond and K-type files to remove dentin. Oral Surg 1980;50:5668. 5. Martin H, Cunnigham W, Norris JP, Cotton W. Ultrasonic versus hand filing of dentin: a quantitative study. Oral Surg 1980;49:79-81. 6. Cunningham W, Martin H, Forrest W. Evaluation of root canal debridement by endosonic synergistic system. Oral Surg 1982;53:401-4. 7. Martin H, Cunningham W. A scanning electron microscope evaluation of root canal debridement with endosonic synergistic system. Oral Surg 1982;53:527-31. 8. Cunningham W, Joseph S. Effect of temperature on the bacteriocidal action of sodium hypochlorite endodontic irrigant. Oral Surg 1980;50:569-71. 9. Cunningham W, Martin H, Pellen G, Stoops D. A comparison of antimicrobial effectiveness of endosonic and hand root canal therapy. Oral Surg 1982;54:238-41. 10. Martin H. Ultrasonic disinfection of the root canal Oral Surg 1976;42:92-9. 11. Martin H, Cunningham W. An evaluation of post-operative pain incidence following endosonic and conventional root canal therapy. Oral Surg 1982;54:74-6. 12. Martin H, Cunningham W. The effect of endosonic and hand manipulation on the amount of root canal material extruded. Oral Surg 1982;53:6113. 13. The Dentsply| | Cavi-Endor Unit. Form No. 3607-D, Copyright 1984, Dentsply International. 14. Ahmad M, Pitt Ford TR, Crum LA. Ultrasonic debridement of root canals: an insight into the mechanisms involved. J Endodon 1987;13:93-101. 15. Ahmad M, Pitt Ford TR, Crum LA. Acoustic cavitation and its implications an ultrasonic root canal debridement [Abstract 14]. J Endodon 1987;13:131. 16. Ahmad M, Pitt Ford TR, Crum LA. Ultrasonic debridement of root canals: streaming and its possible role. J Endodon 1987;13:490-9. 17. Pedicord D, EIDeeb ME, Messer HH. Hand versus ultrasonic instrumentation: its effect on canal shape and instrumentation time. J Endodon 1986;12:375-81. 18. Walsh CL. A comparison of hand and ultrasonic endodontic instrumentation. Master's Thesis, University of Minnesota, 1987. 19. 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 Endedon 1983;9:327-31. 20. Weller NR, Brady JM, Bernier WE. Efficacy of ultrasonic cleaning. J Endodon 1980;6:740-3. 21. Reynolds MR, Madison S, Walton RE, Krell KV, Rittman BRJ. An in vitro histological comparison of the step-back, sonic, and ultrasonic instrumentation techniques in small, curved root canals. J Endodon 1987;13:307-14. 22. Osada Er,ac Ultra-Endo Instrument System (instructions), Osada Electric Co., CNO8504-30. 23. Sonic Air MM3000 Endo System (instructions), Medidenta International, Inc. 24. The Endostar 5 Sonic System, Syntex Dental Products, Valley Forge, PA. 25. Schneider S. A comparison of canal preparations in straight and curved root canals. Oral Surg 1971 ;32:271-5.
BUCCAL
FiG 4. Tracing and photograph of postinstrumentation cross-section illustrating canal shape. Left canal is from the hand instrumentation group, while the right is from the Enac group.
HESIM.
BUCC ~AL
Oval
L N IGUAL
FIG 5. Tracing and photograph of postinstrumentation cross-section illustrating canal shape (note stripping perforation). The left and right canals are from the Cavi-Endo and EndoStar 5 groups, respectively. versity, Riyadh, Saudi Arabia. Dr. EIDeeb is associate professor and director of the Graduate Program, Department of Endodontics, School of Dentistry, University of Minnesota, Minneapolis, MN.