MTA usado en cubrimiento pulpar

1996;127;1491-1494J Am Dent Assoc and SP KariyawasamTR Ford, M Torabinejad, HR Abedi, LK Baklandpulp-capping materialUsing mineral trioxide aggregate as a

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ARTICLE 1

USING MINERALTRIOXIDEAGGREGATEAS A PULP-CAPPING MATERIAL

THOMAS R. PITT FORD, B.D.S., PH.D.; MAHMOUD TORABINEJAD, D.M.D., M.S.D., PH.D.; HAMID R.ABEDI, B.D.S.; LEIF K. BAKLAND, D.D.S.; STALIN P. KARIYAWASAM

Gentists have long recognizedthat traumatic exposures of thedental pulp can be successfullycapped with calcium hydroxidepreparations that produce cal-cific bridges across the woundsurface.'4 Several investigatorshave demonstrated that the ex-posed dental pulp has the ca-pacity to heal when microleak-age and bacterial contaminationare prevented.356 Therefore, itappears that an effective pulp-capping material should be bio-compatible, provide a biologicalseal and prevent bacterial leak-age.An experimental material,

mineral trioxide aggregate, orMTA (Loma Linda University),has recently been shown in a se-ries of investigations to be bio-compatible and to seal pathwaysof communication between theroot canal system and the exter-nal surface of the teeth.7'-4 Dyeand bacterial leakage studies78have shown the sealing abilityof MTA to be superior to that ofamalgam- or zinc oxide-eugenol-, or ZOE, based materi-als. The biocompatibility ofMTA is equal or superior to thatof these materials.1011

Furthermore, the use ofMTAas a root-end filling material indogs and monkeys, as well asfurcation repair material indogs, has led to superior resultscompared with amalgam.12-'4

3 -

This study examined the dental

pulp responses in monkeys to

mineral trioxide aggregate, or

MTA, and a calcium hydroxide

preparation when used as pulp-

capping materials. After the

pulps of 12 mandibular incisors

were exposed with a No. I round

bur, they were capped with ei-

ther MTA or the calcium hydrox-

ide preparation. After five

months, the authors noted no

pulpal inflammation in five of six

samples capped with MTA, and

all six pulps in this group had a

complete dentin bridge. In con-

trast, all of the pulps capped with

the calcium hydroxide prepara-

tion showed pulpal inflammation,

and bridge formation occurred in

only two samples. Based on

these results, it appears that

MTA has the potential to be used

as a pulp-capping material during

vital pulp therapy.

Histologic examination of speci-mens in these experimentsshowed formation of new ce-

mentum over MTA when it wasused as a root-end filling mate-rial'2"13 or as a repair material inexperimentally perforated fur-cation of mandibular premolarsof dogs.'4

The purpose of this studywas to compare the dental pulpresponses in monkeys afterMTA or a calcium hydroxidepreparation (Dycal, L.D. Caulk)was applied as a pulp-cappingmaterial.

MIVATERIALS ANDMETHODS

We used 12 mandibular incisorsin four healthy 4-year-oldcynomolgus monkeys in this ex-periment. General anesthesiawas achieved with an intramus-cular injection of 20 milligramsper kilogram of ketamine. Weisolated the teeth with a rubberdam and, using a No. 1 roundbur in a high-speed handpiecewith copious water spray, creat-ed standardized pulp exposures(1 millimeter in diameter)through a lingual access open-ing. We controlled bleeding withsterile cotton pellets beforeplacing the pulp-capping mate-rials.

The materials used were ei-ther a calcium hydroxide prepa-ration or MTA. The calcium hy-droxide preparation was mixedaccording to the manufacturer'sdirections and applied to the ex-

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RESEARCH-

posure site; the remainder ofthe cavity was filled with amal-gam. The MTA powder wasmixed with sterile saline (at a3:1 powder-saline ratio) andpacked into the entire accesscavity.

Five months later, we surgi-cally removed the teeth andtheir surrounding tissues fromthe jaws after killing the ani-mals and perfusing them withformalin. The specimens wereprocessed for histologic exami-nation. The sections werestained with hematoxylin andeosin as well as by the Brownand Brenn method for identifi-cation of bacteria in the sam-ples. Two of the investigators(T.P.F. and H.A.) assessed thesections jointly for the presenceof dentin bridge, inflammationand bacteria on the cavitywalls.

RESULTS

All of the pulps capped withMTA showed dentin bridge for-mation (Figure 1), and all butone were free of inflammation.The bridge that formed adjacentto the MTA was thick and con-tinuous with the original

dentin. In contrast, only twodental pulps capped with thecalcium hydroxide preparationhad dentin bridges, and all sixhad pulpal inflammation(Figure 2), which was severeand dominated by polymor-phonuclear leukocytes. We didnot observe bacteria on cavity

All of the pulpscapped with MTAshowed dentin bridgeformation and all butone were free of in-flammation.

walls in any tooth filled withMTA, but did detect bacteria inone sample filled with the calci-um hydroxide preparation andamalgam.

DISCUSSION

The favorable tissue responsesto MTA as a pulp-capping mate-rial mirror those observed inthe cuspids of beagle dogs.15Abedi and associates15 createdstandardized pulp exposures inthe cuspids of six beagle dogs

and examined the amount ofhard tissue formation and de-gree of inflammation adjacentto the MTA and calcium hy-droxide preparation.Histomorphometric analysis oftheir data after two monthsshowed a significantly higherfrequency of calcific bridge for-mation and less inflammationin the MTA group comparedwith the calcium hydroxidegroup.We observed a thick dentin

bridge in all pulps capped withMTA. The bridge was continu-ous with the adjacent dentin,and dentinal tubules were ob-served in the bridge, particular-ly close to the pulp. The dentinbridge under the MTA showedirregularities in some sections,although no tunnel defects orsoft-tissue inclusions werenoted. Cox and associates6 andPitt Ford and Roberts4 reportedthe presence of tunnel defects inthe dentin bridge after directpulp capping with various calci-um hydroxide preparations.These authors speculated thatthese defects can act as path-ways for microleakage and in-flammatory changes in pulp.

Figure 1. Histologic section demonstrating the pul- Figure 2. Histologic section demonstrating thepal response to pulp capping with mineral trioxide pulpal response to pulp capping with a calciumaggregate (Loma Linda University). A dentin bridge hydroxide preparation (Dycal, L.D. Caulk). Thehas formed a complete barrier at the exposure site pulp is inflamed and no dentin bridge has formedand the pulp is free of inflammation (original mag- (original magnification X50, hematoxylin and eosinnification X50, hematoxylin and eosin stain). stain).

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The formation of dentin adja-cent to MTA could be due to itssealing ability,7'8 biocompatibili-ty,""1 alkalinity9 or other prop-erties associated with this ma-terial. Recent in vitroinvestigation has demonstratedthe ability of MTA to stimulatecytokine release from bonecells,16 indicating that it activelypromotes hard tissue formationrather than being inert, as aremany dental materials.17

The unsatisfactory pulpal re-sponses to the calcium hydrox-ide preparation covered byamalgam could be due to thefact that amalgam did not pro-vide a bacterial-tight seal, andnot the result of the prepara-tion's lack of biocompatibility.The lack of chronic inflammato-ry cells and presence of poly-morphonuclear leukocytes inpulps capped with the calciumhydroxide preparation indicateactive microleakage through theinterface between amalgam andtooth structure. Many investi-gators have implicated bacterialmicroleakage at restorationmargins as the cause of pulpalinflammation.'1120 However,staining bacteria in histologicsections is often difficult andmay not show the bacteria de-spite their presence in the sam-ples.21 Pitt Ford and Roberts4have shown that the calciumhydroxide preparation producesdentin bridge successfully inthe absence of infection.

The importance of avoidingbacterial contamination afterpulp capping was shown by Coxand associates,17 who used ZOEcement to prevent bacterialleakage. Translating these find-ings to clinical practice has al-ways been difficult becauseZOE-based cements cannot beused as permanent restorativematerials. In addition, use of a

ZOE-based cement under com-posite resin is contraindicated.22MTA appears to meet the re-

quirements for pulp-cappingmaterials. It stimulates dentinbridge formation and preventsmicroleakage.7' The materialsets slowly9 but, far from beinga disadvantage, this slow set-ting time prevents settingshrinkage, which is a feature ofmost dental cements and couldbe one of the reasons for leak-age associated with these mate-rials.

I It appears that MTAseals the pathways ofcommunication be-tween the root canalsystem and the exter-nal surfaces of theteeth. Therefore, it issuitable as a pulp-capping material dur-ing vital pulp therapy.

Once set, MTA has a com-pressive strength that equalssome of the fortified ZOEbases,9 and it can be trimmedback with a bur to place a per-manent overlying restoration.Unlike calcium hydroxide ce-ment bases, which may dis-solve, MTA has negligible solu-bility.9 An in vitro study byRehfeld and associates23 andclinical observations of Barnesand Kidd24 and Lewin25 indicatethat calcium hydroxide dis-solves under amalgam restora-tions. These investigators24'25 at-tributed the disappearance ofcalcium hydroxide to microleak-age of restorative materialsplaced over the calcium hydrox-ide preparations. Because MTAsets hard and has neglible solu-

bility, its use as a pulp-cappingmaterial should prevent recon-tamination of dental pulp,which can occur with calciumhydroxide preparations, asshown by Cox and associates.6

CONCLUSION

Based on the results of thisstudy and the propertiesdemonstrated when MTA wasused as a root-end filling mate-rial and for repair of iatrogenicroot perforation,12"'4 it appearsthat MTA seals the pathways ofcommunication between theroot canal system and the exter-nal surfaces of the teeth.Therefore, it is suitable as apulp-capping material duringvital pulp therapy. Future stud-ies with larger sample sizes areneeded to confirm the results ofthe present investigation. .

Dr. Pitt Ford is a senior lecturer in theDepartment of Conservative Dentistry,United Medical and Dental Schools of Guy'sand St. Thomas' Hospitals, University ofLondon, England.

Dr. Torabinejad is a professor of endodon-tics and director, Graduate Endodontics,Department of Endodontics, School ofDentistry, Loma Linda University, LomaLinda, Calif. 92350. Address reprint requeststo Dr. Torabinejad.

Dr. Abedi is an assistant professor,Department of Endodontics, School ofDentistry, Loma Linda University, LomaLinda, Calif.

Dr. Bakland is an associate dean and chair-man, Department of Endodontics, School ofDentistry, Loma Linda University, LomaLinda, Calif.

Mr. Kariyawasam is a member ofAnatomyand Cell Biology, United Medical and DentalSchools of Guy's and St. Thomas' Hospitals,University of London, England.

None of the authors has any financial inter-est in the materials tested. Loma LindaUniversity will receive general research sup-port from royalties generated.

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2. Tronstad L. Reaction of the exposed pulpto Dycal treatment. Oral Surg Oral Med OralPathol 1974;38(6):945-53.

3. Cvek M, Granath L, Cleaton-Jones P,Austin J. Hard tissue barrier formation inpulpotomized monkey teeth capped with

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cyanoacrylate or calcium hydroxide for 10 and60 minutes. J Dent Res 1987;66(6):1166-74.

4. Pitt Ford TR, Roberts GJ. Immediate anddelayed direct pulp capping with the use of anew visible light-cured calcium hydroxidepreparation. Oral Surg Oral Med Oral Pathol1991;71(3):338-42.

5. Cox CF, Bergenholtz G, Fitzgerald M, etal. Capping of the dental pulp mechanicallyexposed to the oral microflora-a 5-week ob-servation of wound healing in the monkey. JOral Pathol 1982;11(4):327-39.

6. Cox CF, Bergenholtz G, Heys DR, SyedSA, Fitzgerald M, Heys RJ. Pulp capping ofdental pulp mechanically exposed to oral mi-croflora: a 1-2 year observation ofwoundhealing in the monkey. J Oral Pathol1985;14(2):156-68.

7. Torabinejad M, Watson TF, Pitt Ford TR.Sealing ability of a mineral trioxide aggregatewhen used as a root end filling material. JEndod 1993;19(12):591-5.

8. Torabinejad M, Rastegar AF, KetteringJD, Pitt Ford TR. Bacterial leakage of miner-al trioxide aggregate as a root-end filling ma-terial. J Endod 1995;21(3):109-12.

9. Torabinejad M, Hong CU, McDonald F,Pitt Ford TR. Physical and chemical proper-ties of a new root-end filling material. JEndod 1995;21(7):349-53.

10. Torabinejad M, Hong CU, Pitt Ford TR,Kettering JD. Cytotoxicity of four root endfilling materials. J Endod 1995;21(10):489-92.

11. Torabinejad M, Hong CU, Pitt Ford TR,Kariyawasam SP. Tissue reaction to implant-ed SuperEBA and mineral trioxide aggregatein the mandible of guinea pigs: a preliminaryreport. J Endod 1995;21(11):569-71.

12. Torabinejad M, Hong CU, Lee SJ,Monsef M, Pitt Ford TR. Investigation of min-eral trioxide aggregate for root-end filling indogs. J Endod 1995;21(12):603-8.

13. Torabinejad M, Pitt Ford TR, McKendryDJ, Abedi HR, Miller DA, Kariyawasam SP.Histologic assessment of mineral trioxide ag-

gregate as root end filling in monkeys. JEndod (In press).

14. Pitt Ford TR, Torabinejad M, McKendryDJ, Hong CU, Kariyawasam SP. Use of min-eral trioxide aggregate for repair of furcalperforations. Oral Surg Oral Med Oral PatholOral Radiol Endod 1995;79(6):756-62.

15. Abedi HR, Torabinejad M, Pitt Ford TR,Bakland LK. The use of mineral trioxide ag-gregate cement (MTA) as a direct pulp cap-ping agent (Abstract no. 44). J Endod1996;22(4):199.

16. Koh ET, Pitt Ford TR, Torabinejad M,McDonald F. Mineral trioxide aggregate stim-ulates cytokine production in human os-

teoblasts. J Bone Min Res 1995;10S:S406.17. Cox CF, Keall CL, Keall HJ, Ostro E,

Bergenholtz G. Biocompatibility of surfacesealed dental materials against exposedpulps. J Prosthet Dent 1987;57(1):1-8.

18. Watts A. Bacterial contamination andthe toxicity of silicate and zinc phosphate ce-ments. Br Dent J 1979;146(1):7-13.

19. Cox CF. Biocompatibility of dental ma-terials in the absence of bacterial infection.Oper Dent 1987;12(4):147-52.

20. Browne RM, Tobias RS, Crombie IK,Plant CG. Bacterial miocroleakage and pulpalinflammation in experimental cavities. IntEndod J 1983;16(4):147-55.

21. Mjor IA. Histologic demonstration ofbacteria subjacent to dental restorations.Scand J Dent Res 1977;85(3):169-74.

22. Smith BGN, Wright TS, Brown D. Theclinical handling of dental materials. 2nd ed.Oxford, England: Butterworth-Heinemann;1994:139-40.23. Rehfeld RL, Mazer RB, Leinfelder KF,

Russell CM. Evaluation of various forms ofcalcium hydroxide in the monitoring of mi-croleakage. Dent Mater 1991;7(3):202-5.

24. Barnes IE, Kidd EAM. DisappearingDycal: an opinion. Br Dent J 1979;147(5):111.

25. Lewin DA. Disappearing Dycal. Br DentJ 1980;148(2):32.

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