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Physical properties of root canal cements
JOURNAL OF ENDODONTICS [ VOL 2, NO 6, JUNE 1976
P h y s i c a l p r o p e r t i e s of root canal c e m e n t s
Louis I. Grossman, DDS, DMD, Philadelphia
AH26, Diaket, Kerr sealer, Mynol, N2, N2 no-lead, Procosol, Roth 801, Roth 811, RC2B, Tubliseal, a n d zinc oxide-eugenol cement were e x a m i n e d for particle size, flow, setting time, adhesion, a n d peripheral leakage. The results varied in a wide range. An examination of the d a t a should help the generalist or the endodontist t o w a r d a better understandinq of the material he is using, a n d should suqqest to manufacturers opportunities for improving their products.
While the biologic properties of root canal cements have been studied extensively, the physical properties of these materials have been investigated less thoroughly. This paper will deal with some of the physical properties of root canal cements---namely particle size, flow, setting time, adhesion, and dimensional change. Particle size was evaluated to determine its effect on setting time and flow. Flow, or the consistency of the mixed cement enabling it to enter narrow irregularities in the dentin, is an important factor in the filling of lateral or accessory canals. The setting time was studied to determine whether the operator would have enough time to adjust the gutta-percha or silver cone(s) in the root canal(s) if it should become necessary to do so. This is particularly important when obturating multirooted teeth. Adhesion, or the physical attachment of the cement to the canal wall, was determined because it is a desirable property of a cement. Finally, the
166
dimensional change of the cement was determined as exemplified by leakage of a dye around it.
MATERIALS AND METHODS The materials studied were AH26,* Diaket,t Kerr sealer,$ Mynol,w N2,[] N2 no-lead, l[ Procosol (nonstaining), RC2B,# Roth 801,** Roth 811,** Tubliseal,$ and zinc oxide-eugenol cement.t t Pm'ticle Size The size of the particles in the cement powder was measured indirectly. Microscopic measurement of particle size was not determined because of the variation in linear dimension of the various components of a root canal cement powder. Instead, particle size was determined by means of a series of sieves, with the particles first passing through the finest sieve (200 mesh or 74p.m) openings (Figs 1 and 2). Ten milligrams of the powder was weighed on a Mettler H37 balance$$
and transferred to a 200-mesh sieve. The sieve was vibrated on an E-Z Flow vibrators at medium setting for 20 seconds over weighing paper, and the powder that passed through the sieve was weighed. This amount was deducted from the original amount and served as an index of the fineness of the powder. This procedure was repeated ten times for each cement powder and then averaged. Next, 20 mg of the powder was treated as above for 60 seconds, and that which passed through the sieve was allowed to drop into the collecting dish of the 200-mesh sieve. The dish was weighed before and after the procedure because some powders clung electrostatically to the dish and could not be poured out. The difference in weight was an indication of the fineness of the powder. Each test was repeated ten times and then averaged.
Flow The mixed cement,
which con-
JOURNAL OF ENDODONTICS [ VOL 2, NO 9, JUNE 1976
Fig 2--Le/t, particles greater than 741.tm held back by sieve. Right, particles that passed through 741zm openings in sieve and dropped into collecting dish. Fig I - - T w o hundred-mesh sieve on vibrator used to determine particle size.
sisted of three drops of liquid and enough powder to pass the three tests of consistency, was gathered up from the mixing slab and transferred to a small area on a polished glass plate measuring 30 • 26 • 0.6 cm. The glass plate had been previously cleaned thoroughly with equal parts of ethyl alcohol and ether. The glass plate then was stood vertically and held in this position by a clamp on a ring stand. The extent of flow was measured in centimeters after 24 hours (Fig 3). Each test was repeated a~ minimum of ten times and then averaged. Setting Time
Fig
3~Top,
/low o/
cements at ambient temperature o/ 72 F and low humidity. Bottom, /low o/ same cements at ambient temperature o/ 84 F and high humidity.
Each cement was mixed according to the manufacturer's directions when given, or else the cement had to pass a threefold test: offer some resistance to spatulation; not drop off the spatula in 12 to 15 seconds when the spatula was held vertically; and string out for at least 2.5 cm before breaking when the spatula, held horizontally against the mixed cement, was slowly moved away from the slab. Three drops of liquid, which ordinarily would be used for a multirooted tooth, with the required amount of powder, was used for each test with the exception of zinc oxide-eugenol, which required double the amount of liquid. Two kinds of tests were used. In the first test, Dormann spacing washersw167 0.8 m m thick, which have an outside diameter of 16 mm and an inside diameter of 6 mm, were attached to a polished glass plate by means of a sliver of clay. The cement was dropped into the opening from a spatula until the open space was filled. Excess was removed by means of a knife edge passed over the surface of the spacers (Fig 4). The setting time was tested on the half hour, hour, and successive hours until a Gillmore needlell I1 made no inden167
JOURNAL OF ENDODONTICS [ VOL 2, NO 6. JUNE 1971
Adhesion
Fig 4--Cements in duplicate or triplicate being tested for setting time, using Dormann spacing washers.
Fig 5---Close-up view o[ cylinders [illed with cement and with ball chain and O-shaped stop to prevent chain from coming in contact with glass slide. Notice wall of clay to prevent cement from leaking out of cylinders. tation on the cement. Each test was repeated a minimum of ten times and then averaged. In the second test, a three-drop mixture of cement was placed on a glass plate similar to the one used in the flow study, and the thin layer of cement that flowed down on the surface of the plate was tested hourly for indentation and ultimately hardness with a blunt, stiff wire.
168
Microscope glass slides were sandblasted to create a rough surface somewhat similar to that of the prepared canal. The slide was thoroughly cleaned with equal parts of ethyl alcohol and ether. A thoroughly clean stainless steel tube (penicyIinders) measuring 1 cm in length and having an internal diameter of 6 m m was placed on the surface of the glass slide. Each tube had a collar of clay around it that rested on the slide and whose purpose was to prevent leakage of the cement between the tube and the slide. The freshly mixed cement was then dropped from the spatula into the tube until it was about two-thirds full. Two links of a ball chain were carefully pressed down into the cement. A stop attached to the chain limited the depth of insertion of the chain and prevented it from coming in contact with the slide (Fig 5). Two tubes were filled in this manner at each end of the glass slide, and the slide was placed in an incubator at 37 C and I 0 0 % relative humidity for one week to give the cement maximum time to harden. The slide then was placed in a retaining slot, and the upper part of the chain was attached to the main length of chain, which was looped over a 10-cm nylon pulley. A t the other end of the chain a metal breaker was attached to receive weights ranging from I00 to 1,000 gm (Fig 6). The weights were applied in 100gin increments at about 10- to 15second intervals until the tube containing the cement was dislodged from the slide. The tests were repeated 20 times and then averaged.
Dimensional Change Glass tubes 82182 having a capacity of 20/zl were filled for a distance of 6 to 8 mm with freshly mixed cement. The tubes were placed in aqueous safranin dye, or they were kept
at room temperature for five to seven days to allow adequate time for the cement to harden and then placed in the dye. They were removed, washed off with tap water to remove excess dye on the surface, dried, and examined for evidence of penetration of the dye laterally between the cement and the glass wall (Fig 7). All tubes were exposed to the dye for 24 hours before being examined.
RESULTS Particle Size There was relatively little difference in determining particle size whether 10 mg of the powder was vibrated in the 200-mesh sieve for 20 seconds or 20 mg of powder was used in the test for 60 seconds. If the results of the 20-rag samples are divided in half, comparison with the 10-rag samples is facilitated. While the differences are small, they are generally in favor of the larger sample. The sequence of the degree of fineness, beginning with the finest, is as follows: AH26, Roth 811, Kerr sealer, Roth 801, Mynol, RC2B, N2, N2 no-lead, Procosol, zinc oxide-eugenol, and Diaket. Because Tubliseal is a paste, it could not be tested for particle size. The sequence is the same for the 10- and the 20-mg groups, except that Kerr sealer and Roth 811 exchange places in the degree of fineness. The average weight loss, that is, the difference between the original amount of powder and the amount recovered, was an average of 0.5 nag for the 10-rag group and 0.7 mg for the 20-rag group. The actual results, each representing five tests, are shown in Table 1 and Chart 1.
Flow F r o m the standpoint of flow, the cements arrange themselves conveniently into three groups: rapid, mod-
JOURNAL OF ENDODONTICS ] VOL 2, NO 6, JUNE 1976
Fig 7 - - G r o u p of microliter tubes [illed with cements tested for leakage. Notice flotation o / c e m e n t s in some tubes.
Fig 6 Apparatus used for testing adhesion of cements. Fourteen cylinders on seven glass slides, in background, to be tested; one slide is inserted in slot. Left, beaker is suspended from ball chain to receive weights at right. erate, and no flow. While there were some divergences among the ten tests for each cement, owing to differences in the mixes made on different days (which were affected by varying temperature and humidity), the flow patterns were singularly uniform. AH26, Mynol, Roth 801, and Roth 811 are in the rapid-flow group. K e r r sealer, Procosol, and Tubliseal are in the moderate category. Diaket, N2, N2 no-lead, RC2B, and zinc oxide-eugenol had no flow. (Table 2, Chart 2). There was no correlation between particle size and flow rate.
Settinq Time Both high temperature and high humidity decreased the setting time. Some cements set within the hour
while others took days to set. The range of setting time for the different cements is very wide, the spread being from 1 to 40 hours at ambient temperature. The time from indentation (a depression in the cement that remained after the Gillmore needle was applied) to hard setting of the cement also varied. F o r example, it took 1 89 hours from indentation to hard setting for Mynol cement, and 17 hours for zinc oxide-eugenol. Sequence of the cements in the order of setting time from fast to slow is as follows: K e r r sealer, Tubliseal, Mynol, RC2B, N2, N2 no-lead, Diaket, Roth 811, Roth 801, zinc oxideeugenoI, AH26, and Procosol (Table 3, Chart 3). Because the cement films that flowed down on the glass plate were thicker than those in the Dormann spacing washers, it took longer for the cement to attain hardness. Essentially, however, the sequence was the same, with Kerr sealer and Tubliseal taking the lead, followed by Mynol, RC2B, N2, N2 no-lead, Roth 811, Roth 801, AH26, Procosol, Diaket, and zinc oxide-eugenol.
Adhesion
showed superior adhesive properties on the roughened surface of the glass slide. None of the other cements approached their ability to remain attached to the slides. They resisted dislodgement even when weights up to 1,200 gm were used. Occasionally it required 800 gm to dislodge a zincoxide-type resin cement, but this did not occur often. The order of sequence in ability of the cements to resist dislodgement, from most adhesive to least adhesive, is as follows: AH26, Diaket, Mynol, Roth 801, Roth 811, K e r r sealer, Procosol, Tubliseal, N2, N 2 no-lead, RC2B. Zinc oxide-eugenol cement showed no adhesion even after setting for a week at 37 C and 100% relative humidity. The average of 20 tests for each cement and the range are given in Table 4 and Chart 4.
Dimensional Change The determination of dimensional change, or peripheral leakage, was very difficult because shrinkage did not occur uniformly in the tubes. The degree of shrinkage also varied slightly with different batches of the cement that were prepared at different times under varying conditions of
The two plastics, AH26 and Diaket,
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JOURNAL OF ENDODONTICS I VOL 2, NO 6, JUNE 1976
temperature and humidity, similar to those in clinical practice. One might compare the cement-glass junction in the microliter tubes to the location of the cementodentinal junction near the apical foramen, which may vary as much as 1 mm when one surface is compared with another. Nevertheless, a general deduction can be made that some cements showed more leakage than others in repeated tests. Diaket, Kerr sealer, Procosol, Tubliseal, Roth 80t, Roth 811, and RC2B showed the least amount of dimensional change when immersed in the dye immediately after being mixed, showing less than 1 mm of penetration of the dye. N2, N2 nolead, AH26, Mynol and zinc oxideeugenol showed greater leakage than the aforementioned, in that order, with the last showing the greatest dimensional change (Table 5, Chart 5). All of the root canal cements displayed a greater degree of leakage when set at room temperature for from five to seven days as compared with the freshly mixed cements, which is indicative of contraction with the passage of time. A t times the leakage of the dye around the cement occurred very irregularly, either linearly along one wall of the tube for a longer or shorter distance, or spirally, so that it was difficult to measure the distance the dye had penetrated. In a few samples the bulk of the cement was floated up into the tube by the dye (Table 5, Chart 5).
Table 1 9 Particle size (74 #m of cements).
Average mg recovered from I0 nag 9.r (20 secs)
Average mg recovered from 20 mg (60 secs) 17.3
6.8
2.8
0.5 6~2 4.5 2~6 2.8
16.9 9.6 5.5 5.5 3.5 12.7 12.9 8.0 NT 3.0
i.8
6.2 6.7 3.7
811
S\
DISCUSSION
":
i!i iiii!, ii i'i i
:
i i84 :::...... ii! i
"" ....... ~
0
.....
~
number of:milligrams recovered from 2 0 g m (top) !:iO gm (bottom) of cement powders illustrates particle size.
170
N o r m a n and others t found a direct relationship between particle size and setting time of zinc oxide-eugenol-type cements. The complexity in composition and formulation of root canal cements affects and determines the setting time. In most cases, not more than 50% to 60% of the cement powder is composed of zinc oxide. Almost all contain a certain
JOURNAL OF ENDODONTICS [ VOL 2, NO 6, JUNE 1976
Table 2 9 A v e r a g e flow of cements In centimeters.
Cement AH 26 Diaket Kerr sealer Mynol N2 N2 no-lead Procosol Roth 801 Roth 811 RC2B Tubliseal Zinc oxide-eugenol
Centimeters
Range
22.3 NF* 4.1 17.7 NF NF 15.1 20.0 16.2 NF 4.5 NF
19.2-25.5 NF 2.2-5.3 10.8-22.8 NF NF 12.3-20.2 14.0-25.0 12.2-19.0 NF 2.5-6.3 NF
20
15
i:~:!:~:~:.~ 10
*No glow. percentage of synthetic resin or natural rosin; some contain bismuth subnitrate to accelerate the setting of the cement while others contain sodium borate to retard it; and still others contain both of these ingredients to bring about a balance between too rapid or too slow a setting time. In this study there was no correlation between particle size and setting time. F o r example, although Diaket contains the coarsest particles in the powder, it set in much less time than AH26, which has the finest powder and set next to the longest time of any of the cements. Even if we compare zinc oxide-eugenol-type cements we find that although K e r r sealer and Roth 801 have the same particle size, the former sets in an hour while the latter has a setting time of about 20 hours. Particle size is an important factor, however, in the actual mixing of the cement. The smaller the particle size, the easier it is to mix the cement, the less time it takes, and the mixed cement is likely to be smoother and flow better. Although Procosol and Roth 811 are made of nearly the same formula, the latter mixes more easily and has greater flow. There was considerable variation in flow, from AH26, which continued its flow almost to the bottom of the
"I"
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>.
0
~ 0
~ 0
~0
Chart 2----Average flow o[ cements in centimeters. polished glass plate (22.3 cm), to Diaket, N2, N2 no-lead, RC2B, and zinc oxide-eugenol, which did not flow at all. Flow is not dependent on consistency because all cements were mixed to about the same consistency, nor is it related entirely to particle size, although this would appear to be a factor in some cases. The flow properties of a cement depend partly on the ingredients composing the cement and partly on setting time. This is particularly pertinent to flow of cements in the root canal where the setting time is greatly accelerated compared with the setting time on the glass slab. Flow can be improved by pressure. Weisman 2 has aptly pointed out that a cement which does not have much flow is less likely to fill in the nooks and crannies along the canal surface while one that flows too freely is likely to overshoot the apical f o r a m e n . U s i n g another method in this study from that of Weisman to
determine flow, there is both agreement and disagreement in some of the results obtained. Wiener and Schilder a determined the effect of temperature and humidity on setting time and found that both of these factors affected the rate of setting of the cement. As temperature and humidity were increased, setting time was decreased. Their findings have been confirmed in this study. Commercial zinc oxide variably affects the setting time of root canal cements, depending on the method of chemical preparation and on the s o u r c e - - w h e t h e r from zinc ore or zinc blend. Smith 4 found a differential of between 14 and 55 minutes setting time of zinc oxide-eugenol cement, depending on the process of manufacturing the zinc oxide. Absorption of moisture from the air by either zinc oxide or root canal cement will accelerate the setting time. 171
JOURNAL OF ENDODONTICS [ VOL 2, NO 6, JUNE 1976
Higginbotham 5 found that Diaket, Kerr sealer, and Tubliseal hardened in from 20 to 24 minutes while Procosol did not harden at all for the duration of the tests. Wiener and Schilder3 also found that Procosol had a prolonged setting time. Curson and Kirk 6 determined the setting time of several root canal cements. Converting their figures to the nearest half hour, they are as follows: AH26, 43 hours; Diaket, 2~/~ hours; Kerr sealer, 1 hour; Procosol, 1 hour; Tubliseal, one half hour; and zinc oxide-eugenol, 5 hours. The setting time of Procosol given by these investigators differs from most others. The setting time of a mixture of root canal cement on a slab bears no relationship to the setting time in the root canal. N o t only does the temperature and humidity of the mouth
accelerate the rate of setting of the cement in the root canal, but also the thinness of the film of cement plays an important role. One has only to test a thin film of cement on the slab compared to the bulk of a two-orthree-drop mixture to find that the film sets in a comparatively short time. The setting time is probably controlled by oxidation, as well as chelation, in forming a zinc eugenate. It is well known that moisture hastens the setting of zinc oxide-eugenol-type cements. F r o m a clinical standpoint, the root canal should therefore be carefully dried so that it will not interfere with the flow as well as the natural setting of the cement. Unlike other cements that are used in operative dentistry and set within a very narrow range of time, the setting time of the root canal ce-
ments investigated in this study varied in a rather broad range, namely from 1 hour (Kerr sealer and Tubliseal) to 40 hours (Procosol). A cement that hardens in the root canal within a few minutes may handicap the operator who has taken a radiograph and finds that the gutta-percha or silver cone may need adjustment. On the other hand, a very slow-setting cement may irritate the periapical tissue because of an excess of eugenol that results in incomplete chelation or may be instrumental in causing shrinkage of the cement. The ideal setting time, if there is an ideal, has not been determined. Perhaps it is one that begins to set in the root canal in 15 minutes to give an operator who works slowly time to check the obturation of a molar by taking a radiograph and to make the necessary ad-
c~
6C
r
~il/84184 ~
::ii:!~i:Chart3--Average
172
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JOURNAL OF ENDODONTICS I VOL 2, NO 6, JUNE 1976
Table 4 9 Adhesion of cements.
Average number of grams
Cement A H 26 Diaket Kerr sealer Mynol N2 N2 no-lead Procosol Roth 801 Roth 811 RC2B Tubliseal Zinc oxide-eugenol
Range
1,000 1,000 500 600 200 200 500 600 600 200 400 0
1,000 + 1,000 + 200-800 500-800 100-300 100-300 200-700 300-800 400-800 100-400 300-500 0-0
1,000
800
600
400
200
6 -r"
t~
~
>,
<
i5
,-
:~
~
~
o~
=
.c
0
0
0
~-
,,"
,,-
oo
.~
,,"
~-
Chart 4--Average displacement weight o/ cements in grams illustrates adhesion properties. justment, but doesn't hard-set in the root canal until an hour or two. Adhesion is the physical attachment of the cement to the canal wall. A moderate degree of flow in a root canal cement is a desirable property because it facilitates good con-
tact with the canal wall. Regardless of the type of root canal cement, whether it be a zinc oxide type or a plastic, bonding with dentin will not take place. The plastic cements, A H 2 6 and Diaket, did adhere better in the tests than the zinc-oxide-type cements. It
should be borne in mind, however, that the attachment was to a dry, irregularly surfaced glass slide and not to dentin, which contains about 5% moisture. The presence of moisture in the root canal or on the canal wall interferes with the normal setting of the plastic so that its adhesion is mechanical rather than chemical. The adhesion test is useful only for comparing the various zinc-oxide-type cements. These varied from 200 to 600 gm in the tests, with the exception of zinc oxide-eugenol, which showed, no adhesion. This suggests thnt adhesive properties, within limitations, are im, parted to a root canal cement by the resin or the rosin component. The claim by Sargenti (in a written communication on Aug 13, 1975) that the lead in N2 imparts adhesive properties to the cement is not borne out by these tests because there was no difference between N2 and N2 nolead. The cements can be placed arbitrarily into four categories: strongly adhesive: A H 2 6 and Diaket; moderately adhesive: Mynol, Roth 801, Roth 811, K e r r sealer, Procosol, and Tubliseal; weakly adhesive: N2, N 2 no-lead, and RC2B; and no adhesion: zinc oxide-eugenol cement. The degree of contraction of the cements, or leakage, was difficult to measure. Wiener and Schilder 3 also found quantitation of dimensional change difficult. Examination under the microscope was attempted but was unsatisfactory. A x 8 magnifying lens with a built-in millimeter r u l e # # in 0.2-mm divisions was helpful in measuring the degree of dimensional change. Methylene blue was used at first as an indicator of contraction of the cement along the microliter tube wall, but it was replaced by safranin, which produced a more distinct color. While there were some slight discrepancies in the degree of leakage from one mix of cement to
173
JOURNAL OF ENDODONTICS I VOL 2, NO $, JUNE 1976
another, on the whole, the cement being tested came within certain narrow limits except for an occasional "sport." As an example, even though the range for Mynol cement was from 0.2 to 4.0 mml the degree of leakage was mostly near the average of 1.8 mm. AI! cements showed evidence of contraction when exposed to room temperature for five to seven days. Whether less contraction would have occurred if the microtubes had been kept at 37 C and 100% humidity rather than at room temperature is speculative. N2, N2 no-lead, and RC2B showed less contraction than the other cements because they were mixed, not as a cementing medium, but to a thicker consistency as specified by the Sargenti r technique. Curson and Kirk, 6 Grieve, s and Kapsimalis and Evans 9 used various methods for testing leakage of root canal cements. Because of different methods of testing, different results were obtained that may be due to differences in the consistency of the mixed cement and differences in ambience, as well as the physical characteristics of the cement. While the physical properties of a root canal cement are important from a standpoint of clinical usage, the biologic properties are equally, if not even more, important. No matter how well a cement mixes, flows, sets, or adheres, it must also pass a rigorous test in contact with living tissue. This is the ultimate test, but an examination of the biologic properties of root canal cements is not within the purview of this paper. SUMMARY
Twelve commercial root canal cements were tested for particle size, flow; setting time, adhesion, and peripheral leakage. The results varied in a rather wide range. A n examination of the data should help the gen174
Table 5 9 Dimensional change of cements (peripheral leakage of dye in millimeters).
Freshly mixed cement Set cement Cement AH26 Diaket Kerr sealer Mynol N2 N2 no-lead Procosol Roth 801 Roth 811 RC2B Tubliseal Zinc oxide-eugenol
Average
Range
Average
Range
1.5 0.2 0.2 1.8 1.I 1.1 0.2 0.6 0.6 0.6 0.5 1.9
0.9-3.2 0.1-0.2 0.1-0.5 0.2-4.0 1.0-2.1 1.0-1.8 0.1-0.2 0.2-0.9 0.1-0.8 0.1-0.8 0.1-3.0 0.6-4.0
2.1 0.3 1.4 2.9"$ 1.5 1.5 1.8t 2.0t 1.5t 1.0 1.8t 2.1t
1.0-3.0 0.1-0.8 0.1-4.2 2.0-4.6"$ 1.2-1.8 1.2-1.8 0.8-3.9t 0.1-0.4t 0.5-3.6t 0.8-1.4 0.1-4.0t 1.9-3.6r
*Floated by dye up into tube in some tests. tlrregularly along wall of tube.
2.0
1.5
1.0
0.5
~
~
~
o
~
~:
oO =
~
.~ _
+
o4 Z
Chart 5--Dimensional change o/ /reshly mixed cements; average leakage o/ dye in millimeters.
JOURNAl. OF ENDODONTICS I VOI. 2, NO 6, JUNE 1976
eral dentist or the endodontist toward a better understanding of the material he is using, and should suggest to manufacturers opportunities for improving their products. *Claudius Ash, Inc., Niagara Falls, NY'. tPremier Dental Products Co., Philadelphia, *Kerr Mfg. Co., Emeryville, Calif. w Co., Broomall, Pa. [ISupplied through courtesy of Dr. Angelo Sargenti, Locarno, Switzerland. 1lStar Dental Mfg. Co., Conshohocken, Pa. #Supplied through courtesy of Dr. Ramon Werts, Fullerton, Calif. **Roth Drug Co., Chicago. ttAmend Drug and Chemical Co., Irvington, NJ. **Arthur H. Thomas Co., Philadelphia. w167 Supply Co., Philadelphia. I[ I[Supplied through courtesy of S. S. White Dental Products International,
King of Prussia, Pa. 1182 Scientific Co., Broomall, Pa. ##Simmons Omega Co., Woodside, NY. Dr. Grossman is emeritus professor of oral medicine (endodontics) in the School of Den,tal Medicine, University of Pennsylvania, Philadelphia. Requests for reprints should be directed to: Dr. Louis I. Grossman, School of Dental Medicine, University of Pennsylvania, 4001 Spruce St, Philadelphia, 19104. References
1. Norman, R.D.; Swartz, M.L.; Frankiewicz, T.; and Phillips, R.W. Effect of particle size on the physical properties of zinc-oxide-eugenol mixtures. J Dent Res 43:252 March-April 1964. 2. Weisman, M.I. A study of the flow rate of ten root canal sealers. Oral Surg 29:255 Feb 1970. 3, Wiener, B.H. and Schilder, H. A comparative study of important physical
properties of various root canal sealers. Evaluation of setting ,times. Oral Surg 32:768 Nov 1971. 4. Smith, D.C. Setting of zinc oxide/ eugenol mixtures. Br Dent J 105-313 Nov 4, 1958. 5. Higginbotham, T.L. A comparative study of the physical properties of five commonly used root canal sealers. Oral Surg 24:89 July 1967. 6. Curson, I., and Kirk, E.E. An assessment of root canal-sealing cements. Oral Surg 26:229 Aug 1968. 7. Sargenti, A. Endodontics. Locarno, Switzerland, The Author, distributed by Endodontic Educational Service, 1973, p 69. 8. Grieve, A.R. Sealing properties of cements used in root filling. Br Dent J 132:19 Jan 4, 1972. 9. Kapsimalis, P., and Evans, R. Sealing properties of endodontic filling materials using radioactive polar and nonpolar isotopes. Oral Surg 22:386 Sept 1966.
175
P h y s i c a l p r o p e r t i e s of root canal c e m e n t s
Louis I. Grossman, DDS, DMD, Philadelphia
AH26, Diaket, Kerr sealer, Mynol, N2, N2 no-lead, Procosol, Roth 801, Roth 811, RC2B, Tubliseal, a n d zinc oxide-eugenol cement were e x a m i n e d for particle size, flow, setting time, adhesion, a n d peripheral leakage. The results varied in a wide range. An examination of the d a t a should help the generalist or the endodontist t o w a r d a better understandinq of the material he is using, a n d should suqqest to manufacturers opportunities for improving their products.
While the biologic properties of root canal cements have been studied extensively, the physical properties of these materials have been investigated less thoroughly. This paper will deal with some of the physical properties of root canal cements---namely particle size, flow, setting time, adhesion, and dimensional change. Particle size was evaluated to determine its effect on setting time and flow. Flow, or the consistency of the mixed cement enabling it to enter narrow irregularities in the dentin, is an important factor in the filling of lateral or accessory canals. The setting time was studied to determine whether the operator would have enough time to adjust the gutta-percha or silver cone(s) in the root canal(s) if it should become necessary to do so. This is particularly important when obturating multirooted teeth. Adhesion, or the physical attachment of the cement to the canal wall, was determined because it is a desirable property of a cement. Finally, the
166
dimensional change of the cement was determined as exemplified by leakage of a dye around it.
MATERIALS AND METHODS The materials studied were AH26,* Diaket,t Kerr sealer,$ Mynol,w N2,[] N2 no-lead, l[ Procosol (nonstaining), RC2B,# Roth 801,** Roth 811,** Tubliseal,$ and zinc oxide-eugenol cement.t t Pm'ticle Size The size of the particles in the cement powder was measured indirectly. Microscopic measurement of particle size was not determined because of the variation in linear dimension of the various components of a root canal cement powder. Instead, particle size was determined by means of a series of sieves, with the particles first passing through the finest sieve (200 mesh or 74p.m) openings (Figs 1 and 2). Ten milligrams of the powder was weighed on a Mettler H37 balance$$
and transferred to a 200-mesh sieve. The sieve was vibrated on an E-Z Flow vibrators at medium setting for 20 seconds over weighing paper, and the powder that passed through the sieve was weighed. This amount was deducted from the original amount and served as an index of the fineness of the powder. This procedure was repeated ten times for each cement powder and then averaged. Next, 20 mg of the powder was treated as above for 60 seconds, and that which passed through the sieve was allowed to drop into the collecting dish of the 200-mesh sieve. The dish was weighed before and after the procedure because some powders clung electrostatically to the dish and could not be poured out. The difference in weight was an indication of the fineness of the powder. Each test was repeated ten times and then averaged.
Flow The mixed cement,
which con-
JOURNAL OF ENDODONTICS [ VOL 2, NO 9, JUNE 1976
Fig 2--Le/t, particles greater than 741.tm held back by sieve. Right, particles that passed through 741zm openings in sieve and dropped into collecting dish. Fig I - - T w o hundred-mesh sieve on vibrator used to determine particle size.
sisted of three drops of liquid and enough powder to pass the three tests of consistency, was gathered up from the mixing slab and transferred to a small area on a polished glass plate measuring 30 • 26 • 0.6 cm. The glass plate had been previously cleaned thoroughly with equal parts of ethyl alcohol and ether. The glass plate then was stood vertically and held in this position by a clamp on a ring stand. The extent of flow was measured in centimeters after 24 hours (Fig 3). Each test was repeated a~ minimum of ten times and then averaged. Setting Time
Fig
3~Top,
/low o/
cements at ambient temperature o/ 72 F and low humidity. Bottom, /low o/ same cements at ambient temperature o/ 84 F and high humidity.
Each cement was mixed according to the manufacturer's directions when given, or else the cement had to pass a threefold test: offer some resistance to spatulation; not drop off the spatula in 12 to 15 seconds when the spatula was held vertically; and string out for at least 2.5 cm before breaking when the spatula, held horizontally against the mixed cement, was slowly moved away from the slab. Three drops of liquid, which ordinarily would be used for a multirooted tooth, with the required amount of powder, was used for each test with the exception of zinc oxide-eugenol, which required double the amount of liquid. Two kinds of tests were used. In the first test, Dormann spacing washersw167 0.8 m m thick, which have an outside diameter of 16 mm and an inside diameter of 6 mm, were attached to a polished glass plate by means of a sliver of clay. The cement was dropped into the opening from a spatula until the open space was filled. Excess was removed by means of a knife edge passed over the surface of the spacers (Fig 4). The setting time was tested on the half hour, hour, and successive hours until a Gillmore needlell I1 made no inden167
JOURNAL OF ENDODONTICS [ VOL 2, NO 6. JUNE 1971
Adhesion
Fig 4--Cements in duplicate or triplicate being tested for setting time, using Dormann spacing washers.
Fig 5---Close-up view o[ cylinders [illed with cement and with ball chain and O-shaped stop to prevent chain from coming in contact with glass slide. Notice wall of clay to prevent cement from leaking out of cylinders. tation on the cement. Each test was repeated a minimum of ten times and then averaged. In the second test, a three-drop mixture of cement was placed on a glass plate similar to the one used in the flow study, and the thin layer of cement that flowed down on the surface of the plate was tested hourly for indentation and ultimately hardness with a blunt, stiff wire.
168
Microscope glass slides were sandblasted to create a rough surface somewhat similar to that of the prepared canal. The slide was thoroughly cleaned with equal parts of ethyl alcohol and ether. A thoroughly clean stainless steel tube (penicyIinders) measuring 1 cm in length and having an internal diameter of 6 m m was placed on the surface of the glass slide. Each tube had a collar of clay around it that rested on the slide and whose purpose was to prevent leakage of the cement between the tube and the slide. The freshly mixed cement was then dropped from the spatula into the tube until it was about two-thirds full. Two links of a ball chain were carefully pressed down into the cement. A stop attached to the chain limited the depth of insertion of the chain and prevented it from coming in contact with the slide (Fig 5). Two tubes were filled in this manner at each end of the glass slide, and the slide was placed in an incubator at 37 C and I 0 0 % relative humidity for one week to give the cement maximum time to harden. The slide then was placed in a retaining slot, and the upper part of the chain was attached to the main length of chain, which was looped over a 10-cm nylon pulley. A t the other end of the chain a metal breaker was attached to receive weights ranging from I00 to 1,000 gm (Fig 6). The weights were applied in 100gin increments at about 10- to 15second intervals until the tube containing the cement was dislodged from the slide. The tests were repeated 20 times and then averaged.
Dimensional Change Glass tubes 82182 having a capacity of 20/zl were filled for a distance of 6 to 8 mm with freshly mixed cement. The tubes were placed in aqueous safranin dye, or they were kept
at room temperature for five to seven days to allow adequate time for the cement to harden and then placed in the dye. They were removed, washed off with tap water to remove excess dye on the surface, dried, and examined for evidence of penetration of the dye laterally between the cement and the glass wall (Fig 7). All tubes were exposed to the dye for 24 hours before being examined.
RESULTS Particle Size There was relatively little difference in determining particle size whether 10 mg of the powder was vibrated in the 200-mesh sieve for 20 seconds or 20 mg of powder was used in the test for 60 seconds. If the results of the 20-rag samples are divided in half, comparison with the 10-rag samples is facilitated. While the differences are small, they are generally in favor of the larger sample. The sequence of the degree of fineness, beginning with the finest, is as follows: AH26, Roth 811, Kerr sealer, Roth 801, Mynol, RC2B, N2, N2 no-lead, Procosol, zinc oxide-eugenol, and Diaket. Because Tubliseal is a paste, it could not be tested for particle size. The sequence is the same for the 10- and the 20-mg groups, except that Kerr sealer and Roth 811 exchange places in the degree of fineness. The average weight loss, that is, the difference between the original amount of powder and the amount recovered, was an average of 0.5 nag for the 10-rag group and 0.7 mg for the 20-rag group. The actual results, each representing five tests, are shown in Table 1 and Chart 1.
Flow F r o m the standpoint of flow, the cements arrange themselves conveniently into three groups: rapid, mod-
JOURNAL OF ENDODONTICS ] VOL 2, NO 6, JUNE 1976
Fig 7 - - G r o u p of microliter tubes [illed with cements tested for leakage. Notice flotation o / c e m e n t s in some tubes.
Fig 6 Apparatus used for testing adhesion of cements. Fourteen cylinders on seven glass slides, in background, to be tested; one slide is inserted in slot. Left, beaker is suspended from ball chain to receive weights at right. erate, and no flow. While there were some divergences among the ten tests for each cement, owing to differences in the mixes made on different days (which were affected by varying temperature and humidity), the flow patterns were singularly uniform. AH26, Mynol, Roth 801, and Roth 811 are in the rapid-flow group. K e r r sealer, Procosol, and Tubliseal are in the moderate category. Diaket, N2, N2 no-lead, RC2B, and zinc oxide-eugenol had no flow. (Table 2, Chart 2). There was no correlation between particle size and flow rate.
Settinq Time Both high temperature and high humidity decreased the setting time. Some cements set within the hour
while others took days to set. The range of setting time for the different cements is very wide, the spread being from 1 to 40 hours at ambient temperature. The time from indentation (a depression in the cement that remained after the Gillmore needle was applied) to hard setting of the cement also varied. F o r example, it took 1 89 hours from indentation to hard setting for Mynol cement, and 17 hours for zinc oxide-eugenol. Sequence of the cements in the order of setting time from fast to slow is as follows: K e r r sealer, Tubliseal, Mynol, RC2B, N2, N2 no-lead, Diaket, Roth 811, Roth 801, zinc oxideeugenoI, AH26, and Procosol (Table 3, Chart 3). Because the cement films that flowed down on the glass plate were thicker than those in the Dormann spacing washers, it took longer for the cement to attain hardness. Essentially, however, the sequence was the same, with Kerr sealer and Tubliseal taking the lead, followed by Mynol, RC2B, N2, N2 no-lead, Roth 811, Roth 801, AH26, Procosol, Diaket, and zinc oxide-eugenol.
Adhesion
showed superior adhesive properties on the roughened surface of the glass slide. None of the other cements approached their ability to remain attached to the slides. They resisted dislodgement even when weights up to 1,200 gm were used. Occasionally it required 800 gm to dislodge a zincoxide-type resin cement, but this did not occur often. The order of sequence in ability of the cements to resist dislodgement, from most adhesive to least adhesive, is as follows: AH26, Diaket, Mynol, Roth 801, Roth 811, K e r r sealer, Procosol, Tubliseal, N2, N 2 no-lead, RC2B. Zinc oxide-eugenol cement showed no adhesion even after setting for a week at 37 C and 100% relative humidity. The average of 20 tests for each cement and the range are given in Table 4 and Chart 4.
Dimensional Change The determination of dimensional change, or peripheral leakage, was very difficult because shrinkage did not occur uniformly in the tubes. The degree of shrinkage also varied slightly with different batches of the cement that were prepared at different times under varying conditions of
The two plastics, AH26 and Diaket,
169
JOURNAL OF ENDODONTICS I VOL 2, NO 6, JUNE 1976
temperature and humidity, similar to those in clinical practice. One might compare the cement-glass junction in the microliter tubes to the location of the cementodentinal junction near the apical foramen, which may vary as much as 1 mm when one surface is compared with another. Nevertheless, a general deduction can be made that some cements showed more leakage than others in repeated tests. Diaket, Kerr sealer, Procosol, Tubliseal, Roth 80t, Roth 811, and RC2B showed the least amount of dimensional change when immersed in the dye immediately after being mixed, showing less than 1 mm of penetration of the dye. N2, N2 nolead, AH26, Mynol and zinc oxideeugenol showed greater leakage than the aforementioned, in that order, with the last showing the greatest dimensional change (Table 5, Chart 5). All of the root canal cements displayed a greater degree of leakage when set at room temperature for from five to seven days as compared with the freshly mixed cements, which is indicative of contraction with the passage of time. A t times the leakage of the dye around the cement occurred very irregularly, either linearly along one wall of the tube for a longer or shorter distance, or spirally, so that it was difficult to measure the distance the dye had penetrated. In a few samples the bulk of the cement was floated up into the tube by the dye (Table 5, Chart 5).
Table 1 9 Particle size (74 #m of cements).
Average mg recovered from I0 nag 9.r (20 secs)
Average mg recovered from 20 mg (60 secs) 17.3
6.8
2.8
0.5 6~2 4.5 2~6 2.8
16.9 9.6 5.5 5.5 3.5 12.7 12.9 8.0 NT 3.0
i.8
6.2 6.7 3.7
811
S\
DISCUSSION
":
i!i iiii!, ii i'i i
:
i i84 :::...... ii! i
"" ....... ~
0
.....
~
number of:milligrams recovered from 2 0 g m (top) !:iO gm (bottom) of cement powders illustrates particle size.
170
N o r m a n and others t found a direct relationship between particle size and setting time of zinc oxide-eugenol-type cements. The complexity in composition and formulation of root canal cements affects and determines the setting time. In most cases, not more than 50% to 60% of the cement powder is composed of zinc oxide. Almost all contain a certain
JOURNAL OF ENDODONTICS [ VOL 2, NO 6, JUNE 1976
Table 2 9 A v e r a g e flow of cements In centimeters.
Cement AH 26 Diaket Kerr sealer Mynol N2 N2 no-lead Procosol Roth 801 Roth 811 RC2B Tubliseal Zinc oxide-eugenol
Centimeters
Range
22.3 NF* 4.1 17.7 NF NF 15.1 20.0 16.2 NF 4.5 NF
19.2-25.5 NF 2.2-5.3 10.8-22.8 NF NF 12.3-20.2 14.0-25.0 12.2-19.0 NF 2.5-6.3 NF
20
15
i:~:!:~:~:.~ 10
*No glow. percentage of synthetic resin or natural rosin; some contain bismuth subnitrate to accelerate the setting of the cement while others contain sodium borate to retard it; and still others contain both of these ingredients to bring about a balance between too rapid or too slow a setting time. In this study there was no correlation between particle size and setting time. F o r example, although Diaket contains the coarsest particles in the powder, it set in much less time than AH26, which has the finest powder and set next to the longest time of any of the cements. Even if we compare zinc oxide-eugenol-type cements we find that although K e r r sealer and Roth 801 have the same particle size, the former sets in an hour while the latter has a setting time of about 20 hours. Particle size is an important factor, however, in the actual mixing of the cement. The smaller the particle size, the easier it is to mix the cement, the less time it takes, and the mixed cement is likely to be smoother and flow better. Although Procosol and Roth 811 are made of nearly the same formula, the latter mixes more easily and has greater flow. There was considerable variation in flow, from AH26, which continued its flow almost to the bottom of the
"I"
Q)
>.
0
~ 0
~ 0
~0
Chart 2----Average flow o[ cements in centimeters. polished glass plate (22.3 cm), to Diaket, N2, N2 no-lead, RC2B, and zinc oxide-eugenol, which did not flow at all. Flow is not dependent on consistency because all cements were mixed to about the same consistency, nor is it related entirely to particle size, although this would appear to be a factor in some cases. The flow properties of a cement depend partly on the ingredients composing the cement and partly on setting time. This is particularly pertinent to flow of cements in the root canal where the setting time is greatly accelerated compared with the setting time on the glass slab. Flow can be improved by pressure. Weisman 2 has aptly pointed out that a cement which does not have much flow is less likely to fill in the nooks and crannies along the canal surface while one that flows too freely is likely to overshoot the apical f o r a m e n . U s i n g another method in this study from that of Weisman to
determine flow, there is both agreement and disagreement in some of the results obtained. Wiener and Schilder a determined the effect of temperature and humidity on setting time and found that both of these factors affected the rate of setting of the cement. As temperature and humidity were increased, setting time was decreased. Their findings have been confirmed in this study. Commercial zinc oxide variably affects the setting time of root canal cements, depending on the method of chemical preparation and on the s o u r c e - - w h e t h e r from zinc ore or zinc blend. Smith 4 found a differential of between 14 and 55 minutes setting time of zinc oxide-eugenol cement, depending on the process of manufacturing the zinc oxide. Absorption of moisture from the air by either zinc oxide or root canal cement will accelerate the setting time. 171
JOURNAL OF ENDODONTICS [ VOL 2, NO 6, JUNE 1976
Higginbotham 5 found that Diaket, Kerr sealer, and Tubliseal hardened in from 20 to 24 minutes while Procosol did not harden at all for the duration of the tests. Wiener and Schilder3 also found that Procosol had a prolonged setting time. Curson and Kirk 6 determined the setting time of several root canal cements. Converting their figures to the nearest half hour, they are as follows: AH26, 43 hours; Diaket, 2~/~ hours; Kerr sealer, 1 hour; Procosol, 1 hour; Tubliseal, one half hour; and zinc oxide-eugenol, 5 hours. The setting time of Procosol given by these investigators differs from most others. The setting time of a mixture of root canal cement on a slab bears no relationship to the setting time in the root canal. N o t only does the temperature and humidity of the mouth
accelerate the rate of setting of the cement in the root canal, but also the thinness of the film of cement plays an important role. One has only to test a thin film of cement on the slab compared to the bulk of a two-orthree-drop mixture to find that the film sets in a comparatively short time. The setting time is probably controlled by oxidation, as well as chelation, in forming a zinc eugenate. It is well known that moisture hastens the setting of zinc oxide-eugenol-type cements. F r o m a clinical standpoint, the root canal should therefore be carefully dried so that it will not interfere with the flow as well as the natural setting of the cement. Unlike other cements that are used in operative dentistry and set within a very narrow range of time, the setting time of the root canal ce-
ments investigated in this study varied in a rather broad range, namely from 1 hour (Kerr sealer and Tubliseal) to 40 hours (Procosol). A cement that hardens in the root canal within a few minutes may handicap the operator who has taken a radiograph and finds that the gutta-percha or silver cone may need adjustment. On the other hand, a very slow-setting cement may irritate the periapical tissue because of an excess of eugenol that results in incomplete chelation or may be instrumental in causing shrinkage of the cement. The ideal setting time, if there is an ideal, has not been determined. Perhaps it is one that begins to set in the root canal in 15 minutes to give an operator who works slowly time to check the obturation of a molar by taking a radiograph and to make the necessary ad-
c~
6C
r
~il/84184 ~
::ii:!~i:Chart3--Average
172
:tnh
*t-
JOURNAL OF ENDODONTICS I VOL 2, NO 6, JUNE 1976
Table 4 9 Adhesion of cements.
Average number of grams
Cement A H 26 Diaket Kerr sealer Mynol N2 N2 no-lead Procosol Roth 801 Roth 811 RC2B Tubliseal Zinc oxide-eugenol
Range
1,000 1,000 500 600 200 200 500 600 600 200 400 0
1,000 + 1,000 + 200-800 500-800 100-300 100-300 200-700 300-800 400-800 100-400 300-500 0-0
1,000
800
600
400
200
6 -r"
t~
~
>,
<
i5
,-
:~
~
~
o~
=
.c
0
0
0
~-
,,"
,,-
oo
.~
,,"
~-
Chart 4--Average displacement weight o/ cements in grams illustrates adhesion properties. justment, but doesn't hard-set in the root canal until an hour or two. Adhesion is the physical attachment of the cement to the canal wall. A moderate degree of flow in a root canal cement is a desirable property because it facilitates good con-
tact with the canal wall. Regardless of the type of root canal cement, whether it be a zinc oxide type or a plastic, bonding with dentin will not take place. The plastic cements, A H 2 6 and Diaket, did adhere better in the tests than the zinc-oxide-type cements. It
should be borne in mind, however, that the attachment was to a dry, irregularly surfaced glass slide and not to dentin, which contains about 5% moisture. The presence of moisture in the root canal or on the canal wall interferes with the normal setting of the plastic so that its adhesion is mechanical rather than chemical. The adhesion test is useful only for comparing the various zinc-oxide-type cements. These varied from 200 to 600 gm in the tests, with the exception of zinc oxide-eugenol, which showed, no adhesion. This suggests thnt adhesive properties, within limitations, are im, parted to a root canal cement by the resin or the rosin component. The claim by Sargenti (in a written communication on Aug 13, 1975) that the lead in N2 imparts adhesive properties to the cement is not borne out by these tests because there was no difference between N2 and N2 nolead. The cements can be placed arbitrarily into four categories: strongly adhesive: A H 2 6 and Diaket; moderately adhesive: Mynol, Roth 801, Roth 811, K e r r sealer, Procosol, and Tubliseal; weakly adhesive: N2, N 2 no-lead, and RC2B; and no adhesion: zinc oxide-eugenol cement. The degree of contraction of the cements, or leakage, was difficult to measure. Wiener and Schilder 3 also found quantitation of dimensional change difficult. Examination under the microscope was attempted but was unsatisfactory. A x 8 magnifying lens with a built-in millimeter r u l e # # in 0.2-mm divisions was helpful in measuring the degree of dimensional change. Methylene blue was used at first as an indicator of contraction of the cement along the microliter tube wall, but it was replaced by safranin, which produced a more distinct color. While there were some slight discrepancies in the degree of leakage from one mix of cement to
173
JOURNAL OF ENDODONTICS I VOL 2, NO $, JUNE 1976
another, on the whole, the cement being tested came within certain narrow limits except for an occasional "sport." As an example, even though the range for Mynol cement was from 0.2 to 4.0 mml the degree of leakage was mostly near the average of 1.8 mm. AI! cements showed evidence of contraction when exposed to room temperature for five to seven days. Whether less contraction would have occurred if the microtubes had been kept at 37 C and 100% humidity rather than at room temperature is speculative. N2, N2 no-lead, and RC2B showed less contraction than the other cements because they were mixed, not as a cementing medium, but to a thicker consistency as specified by the Sargenti r technique. Curson and Kirk, 6 Grieve, s and Kapsimalis and Evans 9 used various methods for testing leakage of root canal cements. Because of different methods of testing, different results were obtained that may be due to differences in the consistency of the mixed cement and differences in ambience, as well as the physical characteristics of the cement. While the physical properties of a root canal cement are important from a standpoint of clinical usage, the biologic properties are equally, if not even more, important. No matter how well a cement mixes, flows, sets, or adheres, it must also pass a rigorous test in contact with living tissue. This is the ultimate test, but an examination of the biologic properties of root canal cements is not within the purview of this paper. SUMMARY
Twelve commercial root canal cements were tested for particle size, flow; setting time, adhesion, and peripheral leakage. The results varied in a rather wide range. A n examination of the data should help the gen174
Table 5 9 Dimensional change of cements (peripheral leakage of dye in millimeters).
Freshly mixed cement Set cement Cement AH26 Diaket Kerr sealer Mynol N2 N2 no-lead Procosol Roth 801 Roth 811 RC2B Tubliseal Zinc oxide-eugenol
Average
Range
Average
Range
1.5 0.2 0.2 1.8 1.I 1.1 0.2 0.6 0.6 0.6 0.5 1.9
0.9-3.2 0.1-0.2 0.1-0.5 0.2-4.0 1.0-2.1 1.0-1.8 0.1-0.2 0.2-0.9 0.1-0.8 0.1-0.8 0.1-3.0 0.6-4.0
2.1 0.3 1.4 2.9"$ 1.5 1.5 1.8t 2.0t 1.5t 1.0 1.8t 2.1t
1.0-3.0 0.1-0.8 0.1-4.2 2.0-4.6"$ 1.2-1.8 1.2-1.8 0.8-3.9t 0.1-0.4t 0.5-3.6t 0.8-1.4 0.1-4.0t 1.9-3.6r
*Floated by dye up into tube in some tests. tlrregularly along wall of tube.
2.0
1.5
1.0
0.5
~
~
~
o
~
~:
oO =
~
.~ _
+
o4 Z
Chart 5--Dimensional change o/ /reshly mixed cements; average leakage o/ dye in millimeters.
JOURNAl. OF ENDODONTICS I VOI. 2, NO 6, JUNE 1976
eral dentist or the endodontist toward a better understanding of the material he is using, and should suggest to manufacturers opportunities for improving their products. *Claudius Ash, Inc., Niagara Falls, NY'. tPremier Dental Products Co., Philadelphia, *Kerr Mfg. Co., Emeryville, Calif. w Co., Broomall, Pa. [ISupplied through courtesy of Dr. Angelo Sargenti, Locarno, Switzerland. 1lStar Dental Mfg. Co., Conshohocken, Pa. #Supplied through courtesy of Dr. Ramon Werts, Fullerton, Calif. **Roth Drug Co., Chicago. ttAmend Drug and Chemical Co., Irvington, NJ. **Arthur H. Thomas Co., Philadelphia. w167 Supply Co., Philadelphia. I[ I[Supplied through courtesy of S. S. White Dental Products International,
King of Prussia, Pa. 1182 Scientific Co., Broomall, Pa. ##Simmons Omega Co., Woodside, NY. Dr. Grossman is emeritus professor of oral medicine (endodontics) in the School of Den,tal Medicine, University of Pennsylvania, Philadelphia. Requests for reprints should be directed to: Dr. Louis I. Grossman, School of Dental Medicine, University of Pennsylvania, 4001 Spruce St, Philadelphia, 19104. References
1. Norman, R.D.; Swartz, M.L.; Frankiewicz, T.; and Phillips, R.W. Effect of particle size on the physical properties of zinc-oxide-eugenol mixtures. J Dent Res 43:252 March-April 1964. 2. Weisman, M.I. A study of the flow rate of ten root canal sealers. Oral Surg 29:255 Feb 1970. 3, Wiener, B.H. and Schilder, H. A comparative study of important physical
properties of various root canal sealers. Evaluation of setting ,times. Oral Surg 32:768 Nov 1971. 4. Smith, D.C. Setting of zinc oxide/ eugenol mixtures. Br Dent J 105-313 Nov 4, 1958. 5. Higginbotham, T.L. A comparative study of the physical properties of five commonly used root canal sealers. Oral Surg 24:89 July 1967. 6. Curson, I., and Kirk, E.E. An assessment of root canal-sealing cements. Oral Surg 26:229 Aug 1968. 7. Sargenti, A. Endodontics. Locarno, Switzerland, The Author, distributed by Endodontic Educational Service, 1973, p 69. 8. Grieve, A.R. Sealing properties of cements used in root filling. Br Dent J 132:19 Jan 4, 1972. 9. Kapsimalis, P., and Evans, R. Sealing properties of endodontic filling materials using radioactive polar and nonpolar isotopes. Oral Surg 22:386 Sept 1966.
175