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Solubility and absorbability in endodontics: need for clarification of terminology
Solubility and absorbability in endodontics: need for clarification of terminology
Martin Greenberg, D.D.S., Ithaca, N.Y.
The progress of endodontics has been hindered by confusion of the terms, re sorbable, absorbable and soluble and their negatives. Proof exists that nonabsorbable sealer actually does absorb. An ideal sealer must be a good sealing agent, well toler ated, radiopaque and rapidly absorbed. Since zinc oxide-eugenol cement comes close to this, an ideal sealer probably will be formulated soon.
Accuracy in terminology is extremely im portant in every facet of human endeavor. Inaccurate definitions have been a stum bling block to progress in an important phase of dentistry— endodontics. In the United States the final filling for root canals almost always consists of materials which are referred to as non absorbable, nonresorbable or insoluble. M uch endodontic treatment in Europe is performed with a soluble or, as it is often called, a resorbable paste as the final filling material. This article will attempt to show that the terms, resorbable, absorbable and sol uble, and the negatives of these terms, are used incorrectly and inaccurately. This loose terminology hinders progress.
TYPES OF SEALERS
In this article dated March 1958, Gross man1 called attention to various types of root canal sealers and stated as follows (italics throughout are my own) : T h ey may be o f the oxyphosphate type, w hich is not used in this country; they may be o f the absorbable, or absorbable-nonabsorbable type used in Europe and South Am erica, or they may be o f the nonabsorbable type used m ore com m only in this country and elsewhere. T h e nonabsorbable type o f root canal ce ment is essentially a com bination o f zinc oxide, resin and precipitated silver. A cem ent o f this type, K err’s sealer, I foun d to set too rapidly and developed a slower setting cement consist ing o f zinc oxide, Staybelite resin and silver.
Most of the leading endodontists attest to the insolubility of sealers which fit Grossman’ s definition. In their text on root canal therapy, Sommer, Ostrander and Crowley,2 when describing the sealer marketed by Kerr, stated: Rickert and D ixon demonstrated that this sealer is well tolerated by the tissues. It does not absorb moisture after it is set, is a non conductor o f thermal change, is insoluble in tissue fluids and does not change form after it is inserted into the tooth.
Harry J. Healey,3 in his text on endo dontics, described Kerr’s sealer as having
GREENBERG . . . VOLUME 68, M A Y 1964 • 77/691
Fig. I • In te grity o f sealer in ro o t canal. Top: P a tient I in M a y I960 (a) and in O c to b e r 1963 (b ). M id d le : Patient 2 in O c t o ber 1961 (a ) and in M a y 1963 (b ). R igh t: Patient 3 in June 1962 (a ) and in A u g u s t 1963 (b )
all the basic attributes of a good filling material including its being “ dimensionally stable” and “ unaffected by tissue fluids.” Sommer, Ostrander and Crowley4 showed their confidence in the tissue tol erance, sealing ability and insolubility of
Kerr’ s root-canal sealer by advocating its use in a “ blunderbuss” canal as the mate rial contacting the periapical tissues, and they described their technic under the heading, “ Careful Manipulation of Sealer Ahead of a Rolled Point.” They then wrote:
78/692 • THE JO URNAL OF THE A M E R IC A N DENTAL A SSO C IA T IO N
Fig. 2 • A b so r p tio n o f zinc o xid e -e u ge n ol resin seale r (G ro ssm a n 's fo rm u la ) from a p ic a l tissues. Left ab o ve : Patient 4 in M a y 1961 (a ) an d in S e p te m b e r 1963 ( b ) . Left below : Patient 5 in M a r c h 1962 (a ) and in A u g u s t 1963 ( b ) . A b o v e : Patient 6 in J a n u a ry 1963 (a) an d in A u g u s t 1963 (b )
Another technique involves the use o f a rolled point and sealer o f different consistency. W hen the point is about to be sealed into the canal, the sealer is m ixed to its usual creamy consistency and spread around the point. Another mix o f sealer is made to a very thick consistency. After placing a drop o f the thick m ix at the end o f the rolled point, it is care fully carried into position. T h e thick mix of sealer will settle and com pletely fill the funnel portion o f the canal.
M y own endodontic studies5 using a root-canal syringe confirm the insolubility o f the zinc oxide-eugenol resin-silver sealer. In Figure 1 the sealer can be seen without the interfering factor o f a gutta percha or silver point. There is little doubt that well-mixed
GREENBERG . . . VOLUME 68, M A Y 1964 • 79/493
sealers answering Grossman’s definition are insoluble in the confines of the tooth. But are they nonabsorbable? Nowhere in the articles and texts quoted was any reference made to the ab sorption of excess paste in the periapical region. References to dimensional stabil ity, insolubility in tissue fluid and use of the word “ nonabsorbable” lead to an as sumption that such sealers remain un changed in tooth and bone. Indications o f the phenomenon o f ab sorption of a sealer, which answers Gross man’s description of a nonabsorbable sealer inasmuch as it is a combination of zinc oxide, resin and eugenol, is described by McElroy and Wach.6 They referred to their zinc-oxide, Canada balsam filling material as “ the plastic filling material” and stated: In the series o f patients treated, radiolucent areas were resolved, and there was com plete resorption o f the plastic filling material and the gutta percha points in the instances in which there had been pronounced overfilling of the root canal. T h e process o f resorption seems to cease when the filling material has been resorbed to the apex o f the root. T h e age o f the patient seems to be a factor. It was observed that the younger the patient the earlier healing and resorption took place.
The reference to resorption of the sealer is diluted by their inclusion of the resorption of gutta-percha. This latter ob servation could be challenged. Since their fillings consisted of gutta-percha and sealer at the apex, the behavior of the sealer alone cannot be observed in their studies. The use o f a pressure syringe5,7 has af forded me the opportunity to observe the absorption o f sealer from the periapical tissue without the interfering factor of a hard core material. Figure 2 shows that the so-called “ nonabsorbable” sealers are consistently and completely absorbed from the periapical tissues. It also reveals that there is a high incidence of accessory canals and that both the main and acces sory canals remain effectively sealed.
It is apparent that insolubility in tissue fluids and nonabsorbability are not synon ymous terms. An explanation o f the dis tinction is that absorption o f the sealers depends on cellular and, more specifically, on vascular elements which ingest and re move the sealer as they would any harm less, particulate foreign body. Once the sealer is removed from the apical tissues to the level of the apical foramen, it no longer falls in the category o f a foreign body, and absorption ceases. The consequences of confusing insolu bility and nonabsorbability have been the following: 1. A great deal has been written about the precise position of a root-canal filling in respect to the apical foramen. If an absorbable-insoluble sealer is used as the prime filling material, this becomes purely an academic question since excess sealer will be well tolerated and subsequently will be absorbed from the periapical re gion to the proper level at the apex. 2. The use of amalgam for retrograde fillings, a material which is difficult and messy to handle, can be dispensed with in favor of a zinc oxide-resin eugenol paste. E. Nichols,8 a Britisher, has stated: I, personally, prefer a fast-setting zinc oxideeugenol com pound for retrograde filling. This com pound requires considerably less skill in handling and control than does amalgam, and the postoperative results have been just as satisfactory.
3. The formulators o f the various zinc oxide-eugenol resin sealers, Rickert, Gross man and W ach were seeking a nonab sorbable material because they equated nonabsorbability with insolubility. They succeeded in formulating a slowly absorb able material, and some of the ingredients are transiently irritating9 and stain tooth structure. The ideal sealer will be not only a good sealing agent, well tolerated and radio paque, but also rapidly absorbed by the tissues. Since zinc oxide-eugenol cement is a moderately good sealing agent, insol uble and rapidly absorbed from the tis
80/694 • THE JO U R N A L OF THE A M E R IC A N DENTAL A SSO C IA T IO N
sues, I am certain that an ideal sealer soon will be formulated. SUMMARY
1. G rossm an, Louis I. A n im prove d root canal cement. J .A .D .A . 56:381 M a rc h 1958. 2. Som m er, R. F.; O strander, F. D., and C row ley, M . C . C lin ic a l e n dod ontics. Philadelphia, W . B. S a u n d e rs C o ., 1956, p. 163. 3. H ealey, H a rry J. Endodontics. M o s b y C o., I960, p. 158.
The term “ nonabsorbable root canal sealer” needs to be redefined. There is proof that the nonabsorbable sealer actu ally does absorb. There is further evidence that the sealer does not absorb, dissolve or disintegrate in the confines of the tooth. Use of the dual properties of insolu bility and absorbability of a zinc oxideeugenol resin cement can simplify and insure successful endodontic therapy. 326 North Geneva Street
St.
Louis,
C.
V.
4. Som m er, R. F.; O strander, F. D., and C row ley, M . C . C lin ic a l e n dod ontics. Philadelphia, W . B. S a u n d ers Co., 1956, p. 300. 5. G re e n b e rg , M artin . F illing root canals o f d e c id u ous teeth by an injection technique. D. D ige st 67:574 Dec. 1961. 6. M c E lro y, D o n ald L., and W a ch , Edw ard C . E n d o d o n tic treatm ent with a zinc o x id e -C a n a d a b a lsa m fill in g m aterial. J .A .D .A . 56:801 June 1958. 7. G re e n b e rg, M a rtin . Filling root canals b y an in jection technique. D. D ige st 69:61 Feb. 1963. 8. N ichols, E. R e tro g ra d e fillin g of the ro o t canal. O ra l Surg., O ra l M e d . & O ra l Path. 15:463 A p r il 1962. 9. G uttuso, Jam e s. H isto p a th o lo g ic study o f rat c o n nective tissue responses to e n d o d o n tic m aterials. O ra l Surg., O ra l M e d . & O ra l Path. 16:713 June 1963.
For golfers attending the annual session in San Fran cisco this year, plans are now being made for a “ Day o f G olf” at the O cean Course, O lym pic Club, Lake side, for Friday, Novem ber 6th. R egister now, the first 144 w ho register will be the participants. W rite to: Dr. W ilbur Parker, G o lf Chairman, 450 Sutter Street, San Francisco, California. Inform ation on fees and particulars w ill follow .
Martin Greenberg, D.D.S., Ithaca, N.Y.
The progress of endodontics has been hindered by confusion of the terms, re sorbable, absorbable and soluble and their negatives. Proof exists that nonabsorbable sealer actually does absorb. An ideal sealer must be a good sealing agent, well toler ated, radiopaque and rapidly absorbed. Since zinc oxide-eugenol cement comes close to this, an ideal sealer probably will be formulated soon.
Accuracy in terminology is extremely im portant in every facet of human endeavor. Inaccurate definitions have been a stum bling block to progress in an important phase of dentistry— endodontics. In the United States the final filling for root canals almost always consists of materials which are referred to as non absorbable, nonresorbable or insoluble. M uch endodontic treatment in Europe is performed with a soluble or, as it is often called, a resorbable paste as the final filling material. This article will attempt to show that the terms, resorbable, absorbable and sol uble, and the negatives of these terms, are used incorrectly and inaccurately. This loose terminology hinders progress.
TYPES OF SEALERS
In this article dated March 1958, Gross man1 called attention to various types of root canal sealers and stated as follows (italics throughout are my own) : T h ey may be o f the oxyphosphate type, w hich is not used in this country; they may be o f the absorbable, or absorbable-nonabsorbable type used in Europe and South Am erica, or they may be o f the nonabsorbable type used m ore com m only in this country and elsewhere. T h e nonabsorbable type o f root canal ce ment is essentially a com bination o f zinc oxide, resin and precipitated silver. A cem ent o f this type, K err’s sealer, I foun d to set too rapidly and developed a slower setting cement consist ing o f zinc oxide, Staybelite resin and silver.
Most of the leading endodontists attest to the insolubility of sealers which fit Grossman’ s definition. In their text on root canal therapy, Sommer, Ostrander and Crowley,2 when describing the sealer marketed by Kerr, stated: Rickert and D ixon demonstrated that this sealer is well tolerated by the tissues. It does not absorb moisture after it is set, is a non conductor o f thermal change, is insoluble in tissue fluids and does not change form after it is inserted into the tooth.
Harry J. Healey,3 in his text on endo dontics, described Kerr’s sealer as having
GREENBERG . . . VOLUME 68, M A Y 1964 • 77/691
Fig. I • In te grity o f sealer in ro o t canal. Top: P a tient I in M a y I960 (a) and in O c to b e r 1963 (b ). M id d le : Patient 2 in O c t o ber 1961 (a ) and in M a y 1963 (b ). R igh t: Patient 3 in June 1962 (a ) and in A u g u s t 1963 (b )
all the basic attributes of a good filling material including its being “ dimensionally stable” and “ unaffected by tissue fluids.” Sommer, Ostrander and Crowley4 showed their confidence in the tissue tol erance, sealing ability and insolubility of
Kerr’ s root-canal sealer by advocating its use in a “ blunderbuss” canal as the mate rial contacting the periapical tissues, and they described their technic under the heading, “ Careful Manipulation of Sealer Ahead of a Rolled Point.” They then wrote:
78/692 • THE JO URNAL OF THE A M E R IC A N DENTAL A SSO C IA T IO N
Fig. 2 • A b so r p tio n o f zinc o xid e -e u ge n ol resin seale r (G ro ssm a n 's fo rm u la ) from a p ic a l tissues. Left ab o ve : Patient 4 in M a y 1961 (a ) an d in S e p te m b e r 1963 ( b ) . Left below : Patient 5 in M a r c h 1962 (a ) and in A u g u s t 1963 ( b ) . A b o v e : Patient 6 in J a n u a ry 1963 (a) an d in A u g u s t 1963 (b )
Another technique involves the use o f a rolled point and sealer o f different consistency. W hen the point is about to be sealed into the canal, the sealer is m ixed to its usual creamy consistency and spread around the point. Another mix o f sealer is made to a very thick consistency. After placing a drop o f the thick m ix at the end o f the rolled point, it is care fully carried into position. T h e thick mix of sealer will settle and com pletely fill the funnel portion o f the canal.
M y own endodontic studies5 using a root-canal syringe confirm the insolubility o f the zinc oxide-eugenol resin-silver sealer. In Figure 1 the sealer can be seen without the interfering factor o f a gutta percha or silver point. There is little doubt that well-mixed
GREENBERG . . . VOLUME 68, M A Y 1964 • 79/493
sealers answering Grossman’s definition are insoluble in the confines of the tooth. But are they nonabsorbable? Nowhere in the articles and texts quoted was any reference made to the ab sorption of excess paste in the periapical region. References to dimensional stabil ity, insolubility in tissue fluid and use of the word “ nonabsorbable” lead to an as sumption that such sealers remain un changed in tooth and bone. Indications o f the phenomenon o f ab sorption of a sealer, which answers Gross man’s description of a nonabsorbable sealer inasmuch as it is a combination of zinc oxide, resin and eugenol, is described by McElroy and Wach.6 They referred to their zinc-oxide, Canada balsam filling material as “ the plastic filling material” and stated: In the series o f patients treated, radiolucent areas were resolved, and there was com plete resorption o f the plastic filling material and the gutta percha points in the instances in which there had been pronounced overfilling of the root canal. T h e process o f resorption seems to cease when the filling material has been resorbed to the apex o f the root. T h e age o f the patient seems to be a factor. It was observed that the younger the patient the earlier healing and resorption took place.
The reference to resorption of the sealer is diluted by their inclusion of the resorption of gutta-percha. This latter ob servation could be challenged. Since their fillings consisted of gutta-percha and sealer at the apex, the behavior of the sealer alone cannot be observed in their studies. The use o f a pressure syringe5,7 has af forded me the opportunity to observe the absorption o f sealer from the periapical tissue without the interfering factor of a hard core material. Figure 2 shows that the so-called “ nonabsorbable” sealers are consistently and completely absorbed from the periapical tissues. It also reveals that there is a high incidence of accessory canals and that both the main and acces sory canals remain effectively sealed.
It is apparent that insolubility in tissue fluids and nonabsorbability are not synon ymous terms. An explanation o f the dis tinction is that absorption o f the sealers depends on cellular and, more specifically, on vascular elements which ingest and re move the sealer as they would any harm less, particulate foreign body. Once the sealer is removed from the apical tissues to the level of the apical foramen, it no longer falls in the category o f a foreign body, and absorption ceases. The consequences of confusing insolu bility and nonabsorbability have been the following: 1. A great deal has been written about the precise position of a root-canal filling in respect to the apical foramen. If an absorbable-insoluble sealer is used as the prime filling material, this becomes purely an academic question since excess sealer will be well tolerated and subsequently will be absorbed from the periapical re gion to the proper level at the apex. 2. The use of amalgam for retrograde fillings, a material which is difficult and messy to handle, can be dispensed with in favor of a zinc oxide-resin eugenol paste. E. Nichols,8 a Britisher, has stated: I, personally, prefer a fast-setting zinc oxideeugenol com pound for retrograde filling. This com pound requires considerably less skill in handling and control than does amalgam, and the postoperative results have been just as satisfactory.
3. The formulators o f the various zinc oxide-eugenol resin sealers, Rickert, Gross man and W ach were seeking a nonab sorbable material because they equated nonabsorbability with insolubility. They succeeded in formulating a slowly absorb able material, and some of the ingredients are transiently irritating9 and stain tooth structure. The ideal sealer will be not only a good sealing agent, well tolerated and radio paque, but also rapidly absorbed by the tissues. Since zinc oxide-eugenol cement is a moderately good sealing agent, insol uble and rapidly absorbed from the tis
80/694 • THE JO U R N A L OF THE A M E R IC A N DENTAL A SSO C IA T IO N
sues, I am certain that an ideal sealer soon will be formulated. SUMMARY
1. G rossm an, Louis I. A n im prove d root canal cement. J .A .D .A . 56:381 M a rc h 1958. 2. Som m er, R. F.; O strander, F. D., and C row ley, M . C . C lin ic a l e n dod ontics. Philadelphia, W . B. S a u n d e rs C o ., 1956, p. 163. 3. H ealey, H a rry J. Endodontics. M o s b y C o., I960, p. 158.
The term “ nonabsorbable root canal sealer” needs to be redefined. There is proof that the nonabsorbable sealer actu ally does absorb. There is further evidence that the sealer does not absorb, dissolve or disintegrate in the confines of the tooth. Use of the dual properties of insolu bility and absorbability of a zinc oxideeugenol resin cement can simplify and insure successful endodontic therapy. 326 North Geneva Street
St.
Louis,
C.
V.
4. Som m er, R. F.; O strander, F. D., and C row ley, M . C . C lin ic a l e n dod ontics. Philadelphia, W . B. S a u n d ers Co., 1956, p. 300. 5. G re e n b e rg , M artin . F illing root canals o f d e c id u ous teeth by an injection technique. D. D ige st 67:574 Dec. 1961. 6. M c E lro y, D o n ald L., and W a ch , Edw ard C . E n d o d o n tic treatm ent with a zinc o x id e -C a n a d a b a lsa m fill in g m aterial. J .A .D .A . 56:801 June 1958. 7. G re e n b e rg, M a rtin . Filling root canals b y an in jection technique. D. D ige st 69:61 Feb. 1963. 8. N ichols, E. R e tro g ra d e fillin g of the ro o t canal. O ra l Surg., O ra l M e d . & O ra l Path. 15:463 A p r il 1962. 9. G uttuso, Jam e s. H isto p a th o lo g ic study o f rat c o n nective tissue responses to e n d o d o n tic m aterials. O ra l Surg., O ra l M e d . & O ra l Path. 16:713 June 1963.
For golfers attending the annual session in San Fran cisco this year, plans are now being made for a “ Day o f G olf” at the O cean Course, O lym pic Club, Lake side, for Friday, Novem ber 6th. R egister now, the first 144 w ho register will be the participants. W rite to: Dr. W ilbur Parker, G o lf Chairman, 450 Sutter Street, San Francisco, California. Inform ation on fees and particulars w ill follow .