Root Canal Sealers - A Seminar

INTRODUCTION

The Washington study of endodontic success and failure suggests percolation of periradicular exudates into the incompletely filled canal as the greatest cause of endodontic failure.

 So for success of the endodontic treatment proper obturation of the root canal space is very essential. And to fulfill this requirement obturating materials are so important. Among the various root canal obturating materials the root canal sealers are very important as they provide the hermetic seal required for the success of the endodontic treatment.

REQUIREMENTS OF IDEAL ROOT CANAL SEALERS

The requirements and characteristics of good root canal sealers are as listed below:

1. It should be tacky when mixed to provide good adhesion between it and the canal wall when set.
2. It should make a hermetic seal.
3. It should be radiopaque so that it can be visualized in the radiograph.
4. The particles of the powder should be very fine so that they can mix easily with the liquid.
5. It should not shrink upon setting.
6. It should not stain the tooth structure.
7. It should be bacteriostatic or atleast not encourage bacterial growth.
8. It should set slowly.
9. It should be insoluble in tissue fluids.
10. It should be tissue tolerant, i.e. nonirritating to periradicular tissues.
11. It should be soluble in common solvent if it is necessary to remove the root canal filling.
12. It should not provoke an immune response in periradicular tissue.
13. It should be neither mutagenic nor carcinogenic.

ZINC OXIDE CEMENTS

Most of the cements in common use contain zinc oxide as a base ingredient of the powder. Included in this group are Grossman’ cement, Kerr root canal sealer, Kerr Tubli seal, Kloroperka, N2 normal, Wachs cement and Endomethasone. The liquid usually consists of eugenol alone or in combination with other liquids such as Canada balsam, eucalyptol, beechwood creosote, or oil of sweet almond in varying amounts. Kloroperka is mixed with chloroform.

Grossman developed a non-staining cement that meets most of the ideal requirements for a root canal sealer. The formula is as follows:

Powder:-

Zinc oxide ------- 42 parts.

Staybellite -------- 27 parts.

Bismuth subcarbonate ------- 15 parts.

Barium sulphate ----------- 15 parts.

Sodium borate ------------- 1 part.

Liquid:-

Eugenol or oil of pimento leaf.

Grossman’s cement hardens in approximately 2 hours at 37 degree Celsius and 100% relative humidity. Its setting time in canal is less. It begins to set in the root canal within 10 – 30 minutes because of the moisture present in dentin. The setting time is also influenced by the quality of zinc oxide and the pH of the resin used, the care and technique used in mixing the cement to its proper consistency, the amount of humidity in the atmosphere, and the temperature and dryness of the mixing slab and spatula.

Studies by Hensten-Petterson and Helgland have shown that zinc-oxide eugenol when applied to cells in culture is decidedly cytotoxic.

Catanzaro and Persinoto demonstrated a large influx of macrophages

into the lesion with subcutaneous implantation of zinc-oxide eugenol for both short and long periods.

It has been reported that use of calcium hydroxide as temporary dressing reduces amount of leakage in zinc oxide eugenol sealer.

All ZOE cements have an extended working time but set faster in the tooth than on the slab because of the increased body temperature and humidity.

The main virtues of such a cement are its plasticity and slow setting time in the absence of moisture, together with good sealing potential because of small volumetric change on setting. Zinc eugenolate has the disadvantage of being decomposed by water through a continuous loss of eugenol. This makes ZOE a weak, unstable material.

Other zinc oxide type cements in use are Tubliseal, Wach’s cement and Nogenol.

TUBLISEAL: As Kerr’s cement fell into some disfavor because of staining, the company developed a non-staining sealer, Tubliseal. Marketed as two paste system, it is quick and easy to mix. It differs from Richert’s cement in that its zinc oxide base paste also contains barium sulphate as a radio-opacifier as well as mineral oil, cornstarch and lechitin. The catalyst is made up of a polypale resin, eugenol and thymol iodide. Its disadvantage has been its rapid set, especially in the presence of moisture. The company has reformulated the sealer to extended working time, and is now available as Sealapex regular or Sealapex EWT.

WACH’S CEMENT: It has a much complicated formula.

Its powder base consists of zinc oxide, with  bismuth subnitrate and Bismuth subiodide as radio-opacifier as well as magnesium oxide and calcium phosphate. The liquid consists of oil of clove along with eucalyptol, Canada balsam and beechwood creosote.

The advantage of Wach’s cement is a smooth consistency without heavy body. The Canada balsam makes the sealer tacky.

A disadvantage is the odor of the liquid—like that of old time dental office.

At one time, medicated variations of ZOE cement were very popular. N2 and its American counterpart, RC2B are the best examples along with Spad and Endomethasone in Europe. There is no evidence that these products seal canals better than or as well as other sealers. However, there is evidence that they dissolve in fluid and thus break the seal. The one common denominator of these medicated sealers is formaldehyde in one form or other. Since formalin is such a tissue destructive chemical, it is no wonder that every cytotoxic test list these sealers as the number one irritant.

It is the claim of their advocates that these sealers constantly release antimicrobial formalin. This appears to be true, but it is this dissolution that breaks the seal and leads to their destructive behavior.

NOGENOL: It was developed to overcome the irritating quality of eugenol. The product is an outgrowth of a noneugenol periodontal pack. The base is zinc oxide, with barium sulphate as radio-opacifier along with a vegetable oil. Set is accelerated by hydrogenated rosin, methyl abietate, lauric acid, chlorothymol and salicylic acid. Removing eugenol from Nogenol evidently does exert the sought after effect of reducing toxicity.

CALCIUM HYDROXIDE SEALERS

CALCIBIOTIC ROOT CANAL SEALER (CRCS): It is essentially a zinc oxide/ eucalyptol sealer to which calcium hydroxide has been added for its so called osteogenic effect. It takes 3 days to set fully in either dry or humid environment. It also shows very little water sorption. This means it is quite stable, which improves its sealant qualities, but brings into question its ability to actually stimulate cementum and/or bone formation. If calcium hydroxide is not released from the cement, it cannot exert an osteogenic effect and thus its intended role is negated.

SEALAPEX: It is also a calcium hydroxide containing sealer delivered as paste to paste in collapsible tubes. Its base is again zinc oxide, with calcium hydroxide as well as butyl benzene, sulphonamide and zinc stearate. The catalyst tube contains barium sulphate and titanium dioxide as radio-opacifiers as well as a propriety resin, isobutyl salicylate and aerocil. In 100% humidity it takes up to 3 weeks to reach a final set. In dry atmosphere it never sets. It is also the only sealer that expands on setting.

At Creighton university it was established that, in a limited surface area, such as in a minimal apical opening, a negligible amount of dissolution occurred.

Gutman and Fava found in vivo that extruded sealapex disappeared from the periapex in 4 months. This dissolution did not appear to delay healing. However, the authors suspected sealer dissolution may continue within the canal system as well, thus eventually breaking the seal.

If water sorption is possible indicator of dissolution, Sealapex showed a weight gain of 1.6% over 21 days in water. In contrast, CRCS gained less than 0.4%. the fluid sorption characteristic of Sealapex may be due to its porosity, which allows marked ingress of water.

LIFE: A calcium hydroxide liner and pulp capping agent similar in formulation to Sealapex, has also been suggested as a sealer.

VITAPEX: Japanese researchers have introduced a calcium hydroxide sealer that also contains 40% iodoform. Its other component appears to be silicone oil. Iodoform a known bactericide, is released from the sealer to suppress any lingering bacteria in the canal or the periapex.

One week following deposits in rats, vitapex, containing Ca labeled calcium hydroxide, was found throughout the skeletal system. This attests the dissolution and uptake of iodoform material. No evidence is given about the sealing or osteogenic capabilities about Vitapex.

PLASTIC AND RESIN SEALERS

Other sealers that enjoy favor worldwide are based more on resin chemistry than on essential oil catalysts.

DIAKET: First reported in 1951. a resin-reinforced chelate formed between zinc oxide and a small amount of plastic dissolved in B-diketone. A very tacky material. Contracts slightly on setting which is subsequently negated by uptake of water.

In a recent dye-penetration study, the sealing ability of diaket was similar to apexit but significantly better than Ketac-endo.

AH26: An epoxy resin based material. It is a glue, and its base is biphenol a-epoxy. The catalyst is hexamethylene-tetramine. It also contains 60% bismuth oxide foe radiographic contrast. As AH26 sets, traces of formaldehyde are temporarily released, which initially makes it antibacterial. AH 26 is not sensitive to moisture and will even set under water. It will not set however, if hydrogen peroxide is present. It sets slowly in 24 -36 hours. Manufacturers recommend that mixed AH26 be warmed on a glass slab over an alcohol flame which renders it less viscous.

Advantages of AH26 are high radiopacity, low solubility, slight shrinkage and biocompatibility.

Disadvantages are formaldehyde release, extended setting time and staining.

AH PLUS: Recognizing the advantages of AH26 the producers of AH26 set out to develop an improved product they renamed AH plus. They retained the epoxy resin glue of AH26 but added new amines to maintain the natural color of the tooth. Ah plus comes in a paste-paste system. It has a working time of 4 hours and a setting time of 89 hours, half the film thickness and half the solubility of regular Ah26.

In a comparative study, Ah plus was found to be less toxic than regular Ah 26.

GLASS IONOMER CEMENTS:

One of the is presently marketed as Ketac –endo. Saito appears to have been an early proponent of endodontic glass ionomers. He suggested using type I luting cement to fill the entire canal.

Pitt – ford recommended endodontic glass ionomers as early as 1976. However, he found the setting time too rapid.

At Temple University, 8 different formulations of Ketac cement were researched for the ease of manipulation, radiopacity, adaptation of the dentin-sealer interface and flow. Ray and Seltzer chose the sealer with the best physical qualities: the best bond to dentin, fewest voids, lowest surface tension, and the best flow. A method of triturating and injecting the cement into the canal was developed. Ketac- Endo was the outcome.

In a follow up study, the Temple group evaluated the efficacy of Ketac-Endo as a sealer in obturating 254 teeth in vivo. At the end of 6 months, they reported a success and failure rate comparable to that of the other studies using other sealers.

Their greatest concern was the problem of removal in the event of re-treatment since there is no known solvent for glass ionomers. A Toronto group reported, however, that Ketac-Endo sealer can be effectively removed by hand instruments and chloroform solvent followed by 1 minute with an ultrasonic no. 25 file.

Leakage studies compared Ketac-Endo with AH26 and Roth’s cement. US Navy researchers found Ketac-Endo allowed greater dye penetration than Roth’s cement and AH26. on the other hand, the Amsterdam group found AH26 leaked more than Ketac-Endo. They related the difference to the film thickness: 39 microns for AH26 and 22 microns for Ketac-Endo.

As far as toxicity is concerned, 2 Greek studies found Ketac-Endo to be very biocompatible material. The first study compared Ketac-Endo to Endion, which they found to be highly toxic, and the second study found only mild inflammation with Ketac-Endo, whereas Tubliseal caused necrosis and inflammation as long as 4 months later.

SEALER EFFICACY

Although all root canal sealers leak to some extent—there is probably a critical level of leakage that is unacceptable for healing, and therefore results in endodontic failure. This leakage may occur at the interface of the dentin and sealer, at the interface of the solid core and sealer, through the sealer itself or by the dissolution of the sealer.

In choosing a sealer, factors other than adhesion must be considered; setting time, ease of manipulation, antimicrobial effect, particle size, radiopacity, proclivity to staining, dissolubility, chemical contaminants, cytotoxicity, cementogenesis and osteogenesis.

ZINC OXIDE, CALCIUM HYDROXIDE TYPE SEALERS:

In a 2 year solubility study, Peters found that ZOE sealer was completely dissolved away.

On the basis of leakage studies alone one would be hard pressed to favor one of the ZOE or zinc oxide calcium hydroxide sealers over the others. Rickert’s sealer, Grossman’s sealer, Wach’s sealer, tubliseal, Nogenol, CRCS, Sealapex, Vtapex, Apexit or Life all appear to be a wash when numerous studies are examined.

The reports are not as favorable for the formaldehyde containing sealers N2, RC2B,Spad and Endomethasone. Yates and Hembree found N2 to be the least effective sealer when compared with Tubliseal or Diaket after 1 year.

Block and Langeland reported 50 failed cases treated with N2 or RC2B.

More recent studies relating to Zinc oxide base sealers have found essentially the same results for ZOE and calcium hydroxide sealer solubility, leakage and bacterial inhibition.

Despite their deficiencies, ZOE cements and their variations continue to be the most popular root canal sealer worldwide. But they are just that, sealers, and any attempt to depend on them wholly or in great part materially reduces long term success. That is the principal reason why silver points failed – too little solid core and too much cement in an ovoid canal.

 If the apical orifice can be blocked principally by solid core material, success is immeasurably improved over long term, if not for life time.

PLASTIC AND RESIN SEALERS:

It seems reasonable to assume that plastics, resins and glues should be more adhesive to dentin and less resorbable than the mineral oxide cements. But they have not proved to be dramatically so. In one study, AH26 was found to be comparable to ZOE sealer but better than 6 others.

In another study, AH26 and Diaket were found satisfactory as sealers along with other ZOE products.

In an Australian study, Ah26 was found to have better sealing capabilities than the 3 other cements: Apexit, Sealpex and Tubliseal. In Newzealand, however, Sealpex outperformed Ah26 upto the 12 week, but there was no significant difference afte that time.

As far as the glass ionomer cement , Ketac-Endo is concerned, Ray and Seltzer found it superior to Grossman’s sealer, but others found it difficult to remove from root canals in retreatment cases.

Dutch researchers found Ketac superior in sealing to Ah26. on the other hand, US Navy researchers found Roth’s sealer and AH26 superior to Ketac-Endo. Also, one Turkish group found Apexit and Diaket superior to Ketac but a second Turkish group found no difference.

TISSUE TOLERANCE OF ROOT CANAL SEALERS

Without question, all of the materials used at this juncture to seal the root canals irritate the periradicular tissues if allowed to escape from the canal. And if placed against a pulp stump, as in partial pulpectomy, they irritate the pulp tissue as well. The argument seems to be not whether the tissue is irritated when this happens but to what degree and for how long it is irritated, as well as which materials are tolerable irritants or which are intolerable irritants.

At present 4 approaches are being used to evaluate scientifically the toxic effects of endodontic materials: cytotoxic evaluation, subcutaneous implants, intraosseous implants and in vivo periradicular reactions.

CYTOTOXIC EVALUATION:

Cytotoxic studies are done by measuring leukocyte migration in a Boyden chamber, by measuring the effect that suspect materials or their extracts have on fibroblasts or HeLa cells in culture, or by using radioactively labeled tissue culture cells, or tissue culture agar overlay, or a fibroblast monolayer or Millipore filter disk.

The numerous cytotoxic evaluation may be summarized by stating that a disappointing number of today’s sealers are toxic to the very cells they have been compounded to protect. Some of them are toxic when first mixed, while they are setting over hours, days, weeks and some continue to ooze noxious elements for years. This is, of course caused by dissolution of the cement, thus releasing the irritants.

All of the zinc oxide type sealers gradually dissolve in fluid releasing eugenol, which is a phenolic compound and is irritating.

Zinc oxide and eugenol, even when the calcium hydroxide is added to the mixture, has been found universally to be a leading cytotoxic agent. Removing eugenol greatly reduces the toxicity.

Zinc oxide itself must also be indicted. Das found zinc oxide to be quite toxic.

Meryon reported that the cytotoxicity of ZOE cement may be based more on the possible toxic effects of zinc ions.

Maseki et al also indicted that zinc ions might be a major offender when they found that dilutions of eugenol released from set cement allowed viability of 75% of their test cells.

If one were to classify popular ZOE type sealers from worst to best as far as cytotoxicity studies are concerned, one would have to rank the pure ZOE sealers as worst ( Grossman’s and Richert’s) followed by Wach’s and Tubliseal, Sealapex, CRCS, and finally Nogenol. Although there is not a universal agreement on this total ranking.

Paraformaldehyde containing sealers not only contain zinc oxide and eugenol but they also contain 4.78-6.5% highly toxic paraformaldehyde. Virtually every cytotoxic study on N2, RC2B, Spad and Endomethasone finds these materials to be the most toxic of all the sealers on the market.

Cytotoxic studies on the plastics and resins reveal much the same results as with the ZOE type sealers. US Navy study found AH26 the least toxic . Swedish dentists reported a mild response using AH26.

In Buenos Aires, AH26 was found to have a moderate effect and Diaket a markedly toxic effect, both at the end of 1 hour. This was because AH26 releases formaldehyde as it sets. Both of these resin sealers were much less toxic than the ZOE controls.

 AH plus and Ketac-Endo have had cytotoxic and genotoxic studies done. Ah plus was compared with its original product, AH26, and in an in vitro test caused only slight to no cellular injuries and did not cause any genotoxicity or mutagenecity.

In a study done in Greece, Ketac-Endo proved to be a very biocompatible material.

SUBCUTANEOUS IMPLANTS:

Subcutaneous implants of the root canal sealers are done to test their toxic effects. These are done either by needle injection under the skin of animals, or by incision and actual insertion o f the product, either alone or in Teflon tubes or cups. Freshly mixed material may be implanted, allowing it to set in situ, or completely set material may be inserted to judge the long term effects.

The results are what one would expect from the cytotoxic studies. Eugenol, as all of the essential oils is a tissue irritant, particularly during initial set. The long term results were also not promising. Tagger and Tagger observed after 2 months, the more severe cutaneous reaction to the ZOE sealer was probably due to the instability of the material, which slowly disintegrated in contact with tissue moisture.

At Northwestern University Nogenol proved to be better tolerated initially than Tubliseal or Richert’s sealer, but at 6 months the effects of Tubliseal were worse and the effects of Richert’s and Nogenol were the same.

Initial inflammation surrounding implants of Sealapex and CRCS, the calcium hydroxide sealers, appears to be resolved in 90 days. Yesilsoy found Sealapex caused a less severe inflammatory reaction than did CRCS. Japanese researchers, announcing a new calcium hydroxide sealer, Vitapex, which also contains iodoform and silicone oil, stated that granulation tissue formed around the implanted material and a nidus of calcification then developed within the tissue.

Ah26 elicited no response at 35 days in one study and was well tolerated at 60 days in another.

Without question, N2 and other formaldehyde containing sealers are consistently the most toxic.

Tissue implantation ranking of the endodontic sealers would again have to list Nogenol, then AH26, Sealapex, and Tubliseal. CRCS, along with the ZOE sealers would rank higher in toxicity and formaldehyde cements rank as unacceptable.

OSSEOUS IMPLANT:

Surprisingly, sealers implanted directly into bone evoke less severe inflammatory response than these same cements evoke in soft tissue.

From Marseille comes a report of 2 ZOE sealers implanted into rabbit mandibles. At 4 weeks , both sealer implants showed slight to moderate reactions—no bone formation or bone resorption. At 12 weeks there were slight to very slight reactions—bone formation in direct contact with the sealer—and bone ingrowths into the implanted tubes. Part of the implanted sealers were absorbed and macrophages were loaded with the sealer.

When Deemer and Tsaknis over filled the tubes, the over fillings did not significantly compromise the healing of the rat intraosseous tissue. However, they noted the irritating properties of the Grossman’s sealer.

In Argentina, Zmener and Dominguez tested glass ionomer cements in dog tibias and stated that at 90 days the inflammatory picture had resolved with progressive new bone formation.

Again, the Para formaldehyde containing cements came off the second best.

IN VIVO TISSUE TOLERANCE EVALUATIONS:

There is no question that the ideal method of testing a substance is in vivo in a human subject. Unfortunately, human experimentation is often dangerous, costly and unethical and therefore, for the most part, animals are substituted. It can also be said that the closer one rises up the phylum tree to Homo sapiens, the more valid the experiment: monkeys are better than dogs and pigs are better than cats.

Erausquin and Muruzabal, working in Buenos Aires performed the seminal in vivo research on the tissue tolerance to sealers with hundreds of tests on techniques and materials. They concluded that all of the commercial root canal sealers were toxic, causing extensive to moderate tissue damage as soon as they escape through the foramen. In all honesty, the authors did believe that the periradicular necrosis may be due in part to an infarct caused by pressure obstruction of the region’s vessels. Necrosis of the DL provoked necrosis of the adjacent cementum and alveolar bone as well. In rats, the PDL regenerated within 7 days if toxic irritation did not continue.

In comparing the various sealers, they found that straight ZOE cement was highly irritating to the periradicular tissues and caused necrosis of the bone and cementum. Inflammation persisted fro 2 weeks or more. Finally the ZOE became encapsulated. Much the same inflammatory reaction was seen at the US National Bureau of Standards when monkey teeth were overfilled with ZOE cement.

In a further study, Erausquin and Muruzabal studied other ZOE based cements. All of the cements, if the canal was overfilled, showed a tendency to be resorbed by phagocytes. Grossman’s sealer and N2 both provoked severe inflammatory reactions, and Rickert’s sealer caused moderate infiltration.

Another South American group reported on dog periradicular specimens overfilled with Sealapex, CRCS and ZOE—all responded with chronic inflammation.

The least irritating of all the cements tested by Erausquin and Muruzabel were Diaket and AH26. following overfilling with these sealers, the inflammation was generally very mild. Diaket which showed a marked tendency to be projected beyond the apex, became readily encapsulated, on the other hand, AH26 was resorbed. The researchers observed that when a foreign body is not too irritating, it becomes either resorbed or encapsulated by the body. Both of these processes occurred in teeth filled with Diaket and AH26.

Norwegian researchers tested Ah26 against Endomethasone, Kloropercha and ZOE. At 6 months they concluded that periradicular reaction to the endodontic procedures and materials was limited. On the other hand, the University of Connecticut group found long term differences, ranking AH26 as mild irritant, ZOE as moderate and Kloropercha as severe.

One must conclude that periradicular tissue reaction to all cements will at first be inflammatory, but as the cement reach their final set, cellular repair takes place unless the cement continues to break down, releasing one or more of its toxic components.

RECENT ADVANCES IN ROOT CANAL SEALERS

In the never ending search for the perfect root canal sealers, new fields have been invaded, including resin chemistry, which is proving so successful in restorative dentistry, and calcium phosphate cements, which are a return to nature.

At Tufts University, a group experimented with Bis GMA unfilled resin as sealer. The new material was found to be biocompatible but impossible to remove in retreatment cases.

Low viscosity resins such as pit and fissure sealants have also been tried as sealers but would not seem suitable as root canal filling material. Close adaptation depends on smear layer removal, which is difficult to achieve in the apical third of the canal.

A polyamide varnish, Barrier, has also been tried as a sealer but was found to be less effective than ZOE sealers.

At the University of Minnesota, the efficacy of 4 different dentin bonding agents used as root canal sealers was tested. No leakage was measurable in 75% of the canals sealed with Scotchbond, in 70% of the canals sealed with Restodent, in 60% of the canals sealed with Dentin Adhesit and in only 30% of the canals sealed with Gluma. The same researchers reported the dramatic improvement in the quality of sealing root canals using dentin bonding agents.

It seems quite probable that dentin bonding agents will play a major role in sealant endodontics. Their ability to halt microleakage is a superb requisite for future investigations. The Minnesota study returned to single cone gutta percha filling with the adhesives, the cone inserted to spread the adhesive laterally and to occupy space to reduce shrinkage.

From Zagreb, Croatia, a group used 2 different compaction methods, vertical and lateral, to condense composite resin with a bonding agent as a total filling material. They first developed an apical plug with bonding agent and then photopolymerized layer on layer of composite resin with an argon laser as they compacted the composite with pluggers. They found fewer voids in their final filling than with lateral condensation.

From Siena, Italy, another group used dentin bonding agents, along with AH26 sealer and gutta percha laterally condensed, to obturate canals for leakage tests. They found less leakage in those cases in which the bonding agents were used along with AH26 versus Ah26 alone.

Some obvious obstacles must be overcome, before these bonding agents become endodontic sealers of choice. First is the preparation of the dentin to remove all of the smear layer. As Rawlinson pointed out, it is very difficult to remove all of the smear from the apical third canal, even if sodium hypochlorite and citric acid are used with ultrasonic debridement.

A second obstacle is radiopacity. Radiopaquing metal salts must be added to the adhesive, and this is sure to upset the delicate balance that leads to polymerization. All of the bonding agents are very technique sensitive, and many do not polymerize in the presence of moisture or hydrogen peroxide. The third problem is placement, to ensure a total, porosity free placement. A final obstacle is the removal in the event of failure. These resins polymerize very hard, all the more reason to place a gutta percha core allowing future entry down the canal.

CALCIUM PHOSPHATE OBTURATION:

The possibility that one could mix 2 dry powders with water, inject the mixture into a root canal and have it set up as hard as enamel within 5 minutes is exciting, to say atleast.

Developed and patented at the American Dental Association Paffenbarger Research Centre at the National Institute of Standards and Technology by Drs. W.E.Brown and L.C. Chow and their associates, calcium phosphate cements might well be the future ideal root canal sealer, long sought but never achieved.

In mixing 2 variations of calcium phosphate with water, Brown and Chow demonstrated that hydroxyapatite would form.

The early reports on calcium phosphate cements find them comparable to Sealapex but better sealants than the other ZOE sealers.

Studies emanating from the ADA, Paffenbarger center find calcium phosphate cements very praiseworthy for their sealing properties as well as for their tissue compatibility. In one study, they proved better sealants than a ZOE/gutta percha filling. In another study, researchers found that the apatite injectable material demonstrated a uniform and tight adaptation to the dentinal surfaces of the chambers and root canal walls. Calcium phosphate cements also infiltrated the dentinal tubules. Since these sealers set as hydroxyapatite, one must be aware that they are very difficult, but not impossible to remove from the canal.

GUTTA FLOW:

Gutta flow a cold flowable material which consists of polydimethylsiloxane—gutta percha has been introduced in the market. The ratio of gutta percha to sealer is 1:1. it also contains silicone oil, paraffin oil, platinum catalyst, zirconium dioxide, nano silver (preservative).

Consists of 2 components that are homogenously mixed in a mixing capsule. It has good flow properties and easily flows into lateral canals and dentinal tubules. It does not shrink, but expands slightly by 0.2%. working time is 10-15 minutes, which is decreased by increase in temperature. It has a setting time of 25-30 minutes. It is radiopaque, so can be seen on a radiograph. It is extremely biocompatible material, it is encapsulated and no inflammation occurs if it is extruded beyond the apex.

Used with a single cone of gutta percha, that makes the total content of gutta percha in the root filling as 98%.

In case of retreatment, the gutta flow can be removed using a round bur or gates glidden with contact to the canal wall. Solvents like chloroform should not be used to remove gutta flow.

Martha et al. reported that the use of gutta flow with a single gutta percha master cone creates an apical seal that is equivalent to that produced with gutta percha/AH plus sealer using warm vertical compaction.

Ashraf El Ayouti et al. Studied the homogeneity and adaptation of gutta flow to root canal walls and found that gutta flow completely filled the prepared root canal, but small voids were frequently present within the core of the filling material.

ENDOREZ:

Endorez is an endodontic sealer that is based on the urethane dimethylacrylate molecule. It has additives to make it hydrophilic so it can be used in the wet environment of the root canal system. It is very effective in penetrating the dentinal tubules and exhibits initial close adaptation to the dentin. However, gap formation results from polymerization shrinkage. It does not utilize a dentin bonding system. It has been recommended for a single gutta percha cone technique but can be used with other obturating methods.

Two studies showed it to be biocompatible, whereas another, utilizing a different test, reported it to be slightly cytotoxic. Very low bond strengths to dentin are reported for endorez. An d it performed poorly in leakage studies compared to other sealers. It also does not have antimicrobial properties.

A clinical study with endorez reported a 91.3% success rate at 14-24 months.

RESILION/EPIPHANY:

It is the only current resin based obturating system that utilizes a dentin adhesive. Manufacturer’s state that it is more effective than existing obturating materials because it utilizes a resinous obturating material and an adhesive sealer, creating a monoblock of dentin/adhesive/obturating material.

The resilion cones consists of a vinyl polyester material with methacrylate polymer, glass filler particles and opacifiers added. Its appearance and manipulation are similar to gutta percha.

Epiphany sealer consists of a self etching primer that is used with a lightly filled dual cured UDMA sealer/adhesive. Manufacturer states that this system can be used with any obturating method.

Williams et al. reported that neither resilion nor gutta percha has adequate stiffness to reinforce teeth. Tay et al. found no difference in microleakage with resilion system when compared with gutta percha and AH26. he also reported that resilion was susceptible to alkaline and enzymatic hydrolysis. Surface erosion was evident in resilion samples in as little as 20 minutes of immersion in an alkaline hydrolyzing agent.

Versiani et al. reported that epiphany was outside the acceptable range for solubility and dimensional stability, as described by the ANSI/ADA standards, but was within the acceptable range for setting time, flow and thickness.

Melker et al. reported that resilion was found to have no antimicrobial activity, despite the fact that bioactive glass is one of the components and is considered to have anti microbial properties.

Dr. Martin Trope reported that bond strengths of only 4 –n 6 MPa have been achieved between epiphany and dentin. This is similar to the bond strength reported for fibre posts and resin luting agents. Bond strengths of less than 2 MPa are reported between epiphany and resilion which is lower than the bond strengths between gutta percha and AH26.

CONCLUSION

The discussion on root canal sealers can be summarized by repeating a statement made more than 100 years ago by Dr. A.E. Webster of Toronto “it would seem that the dental profession has not yet decided upon a universal root canal filling material.”

Most root canal sealers are some type of zinc oxide eugenol cement or resin. To be an acceptable root canal sealer, the material must be capable of producing a seal while being well tolerated by periapical tissues. Al the sealers presently used appear to have good sealing abilities but none of them produce a leak proof seal. Also all of them produce some degree of periapical inflammation, ranging from mild to severe, in the initial few days after obturation. Fortunately, the inflammatory process does appear to resolve completely and healing follows.

Adhesive obturating materials are in the early stages of development. Although none of the current materials appear to offer a big advantage over traditional obturating materials, none are likely to come to a disastrous end. However, continued research and development is likely to result in improvements and in new, more effective materials.

REFRENCES

1. Endodontics: Ingle, obturation of radicular space.
2. Pathways of pulp: Cohen, obturation.
3. Endodontic therapy: Weine, canal filling with semisolid materials.
4. Endodontic practice: Grossman, obturation of the root canal.
5. Restorative dental materials: Craig, cements.
6. Dental materials: Philips, dental cements.
7. Richard S. Schwartz: adhesive dentistry and endodontics- a review, JOE, December 2006, 1125-1133.
8. Ashraf El Ayouti et al.: homogeneity and adaptation of a new gutta percha paste to the root canals, JOE, September 2005,687-690.