Sealing abil ity of a n e w root

canal f i l l ing material

Sawsan R. AI. Rafei, DDS, MS; F. S. Sayegh DMD, MS, PhD;

and Gary Wright DDS

The function of a root canal filling is to seal the canal hermetically and eliminate any entry to the periapical tissue. ~ More than 100 different tech- niques and almost 270 materials have been used for filling root canals} Gut- ta-percha and silver cones with sealers are the most popular materials. Both materials have their proponents and opponents among endodontists. Gutta- percha is not always introduced easily into the root canal; however, silver cones produce corrosive products that are highly cytotoxic? A combination technique using both materials was proposed to overcome the disadvan- tages of both materials--covering sil- ver cones with a thin layer of gutta- percha. 4

The fact that many different materials have been used to obturate the rt• canal space indicates that the ideal material has not been found. Grossman 1 listed ten requirements for the ideal root canal filling material. It should: be introduced easily into a root canal; seal the canal laterally as well as apically; not shrink after being inserted; be impervious to moisture; possess bacteriostatic properties, or discourage bacterial growth; be radi- opaque; not stain tooth structure; not irritate periapical tissue; be sterile, or be quickly sterilized immediately before insertion; and be easily removed from the root canal.

Gutta-percha has long been the pre- ferred filling material for many endo- dontists, and appears to best meet Grossman's requirements. However, gutta-percha is not always easily intro- duced into the canal, especially into narrow, curved canals, and it does not always seal the canal laterally even when it does seal apically.

The purpose of this study is to determine the sealing qualities, both

apically and laterally, of a new root canal filling material. This material can be used either as a filling or as a sealant, in combination with other materials to facilitate introduction into the canal, especially into narrow, curved canals.

M A T E R I A L S

A N D M E T H O D S

The experimental material (Lee Pharmaceutical, South El Monte, Calif) is a silicone root canal filler/ sealer that consists of a paste-type base and a liquid catalyst. The base con- tains siloxanes and silicones (medical grade), inert pigments, and barium sulfate. The catalyst contains silicones and silicates. The material is radi- opaque, can be passed through a 30- gauge needle, is odorless, and has a light pink color. The shelf life of the material is approximately two years.

A total of 96 freshly extracted human permanent, single-rooted teeth with completely formed apexes were collected and stored in saline solution immediately after extraction. Sixty-six teeth were used for the experimental material, and 30 teeth were used as controls. The following procedure was used to prepare the teeth mechanically before filling them with both the con- trol and experimental materials.

Access to the pulp chamber was made with a round bur in a high-speed handpiece under a copious flow of water. The canal length was estab- lished with a guide file, and all canals were enlarged to two instrument sizes larger than the first instrument that was used at the apex? Each canal was irrigated with distilled water and dried with paper points.

The experimental material was pre- pared by mixing two drops of the

catalyst to I gm of the base for one minute. Using a pressure syringe (Special Products, Inc), the material was introduced into the canals of the prepared teeth. It was injected until it extruded through the apex. The chain. ber of the tooth was filled completely with the material, and the excess at both ends was wiped off with a moist cotton pellet. The control teeth were obturated by cementing a master cone of gutta-percha, using Grossman's Formula Cement as a sealer, and then laterally condensing gutta-percha. The access cavity was filled with gut- ta-percha. The access cavity was not filled with any filling material, to study the adaptability of both materials to the pulp chamber and the ability of the filling material to absorb the dye. The roots of all the teeth were coated with sticky wax, leaving only the apical 2 mm, and the access open- ing exposed.

The teeth were placed in 1% meth- ylene blue dye immediately after being filled. A third of the teeth from both the control, and experimental groups were removed from the dye after inter- vals of 1 day, 1 week, and I month. The teeth were washed with water and sectioned longitudinally for examina- tion under the dissecting microscope. The leakage was graded as follows: complete, for complete penetration of the dye between the filling material and tooth surfaces; partial, for partial penetration of the dye; and none, when no penetration was seen.

R E S U L T S

The Table shows the number of teeth and the degree of dye penetration for both the control material (gutta- percha) and the experimental material for I day, 1 week, and 1 month. There was no leakage of the dye between the tooth surface, and any of the filling materials that were examined under the microscope. The adaptation of the experimental material was fairly good (Fig 1). Small air bubbles were found throughout the bulk of the experimen- tal material. The experimental materi- al was examined for dye penetration through the material itself. It was found that the experimental material did not absorb the dye and still retained the same color of dye treat-

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Table �9 Results of dye penetration and number of teeth used for both experimental and control groups.

Type of No. of Dye Penetration Time material teeth Complete Partial None

One day Control 10 0 0 10 l'xperimental 22 0 0 20

One week Control 10 0 0 10 Experimental 22 0 0 20

Three weeks Control 10 0 0 10 Experimental 22 0 0 20

~aent. The adaptation of the material to the tooth surface was excellent because there were no air bubbles or unfilled voids at the interface of the filling with the tooth surface. Figure 2 shows the experimental material (left) and the control material (right). The experimental material fills the narrow canal of a lower incisor more com- pletely.

D I S C U S S I O N

In endodontic therapy, success is determined when the canal is com- pletely sealed with the filling material. Until a sealing technique provides molecular bonding of the filling mate- rial to tooth structure, total obturation of the root canal against microleakage will probably be impossible/' t lowev- er, the closer the adaptation of the filling material to the canal, the better the seal to the tooth surface.

The dyes were'used in many studies to examine the sealing ability of differ- ent filling materials currently used. <7,s The wide use of the dye technique is probably due to its simplicity and reliability. In many studies, the gutta- pereha cones were used either as an experimental or control material, and it showed a high percentage of success in preventing microleakage. '~'6s In another study by Younis and Hem- bree, 8 gutta-percha showed no leakage during a three-week period. The slight variation in the results of different studies 4's's is probably due to different dyes and different concentrations. The high percentage of success with gutta- percha in preventing the dye penetra- tion was confirmed in this study. The experimental material proved equally effective in sealing the apexes of the experimental teeth. The other advan- tages are the ability to penetrate nar- row canals and to adapt well to the

canal walls; an adequate viscosity that allows it to be easily injected through a line gauge needle; enough working time before setting; and the simplicity of the technique. It seems to meet most of Grossman's criteria for the ideal root canal filling material. Additional investigations are currently in progress to evaluate its tissue toxicity and bacte- riostatic properties.

S U M M A R Y

An in vitro study was made to test the adaptation of a new material designed to be used with the pressure syringe. The study used the dye pene- tration technique, gutta-percha was used as a control material. It was found that the adaptation and sealing ability of both materials were the same for 1 day, 1 week, and 3 weeks.

"['h[s work was partially supported by grants Irom [acuhy residents funds, Ihc RMnehardt lind the Lee Pharmacemicai Co.

l)r. AI. Rafei is associate professnr, conserva- tive department, University of Baghdad, lraq. l)r. Sayegh is professor ar, d chairman, histoh)gy department, and Dr. Wright is assistant profes- sor, endodontic department, University of Mis- souri Dental School. Requests [ 'or reprmts should be directed to I)r. Sayegh, University of Missouri-Kansas City, School of l)entistry, 650 E 25th St, Kansas City, Mn 64108.

References I. (;rossman, L.I. En(lodontic practice. Phil-

adelphia, Lea & Febiger, 1978. 2. Kuuler, Yury. Analysis and cnmparis(m of

root canal lilling tedmique. Oral Surg 48:153- J59, 1979.

3. Seltzer, J., and others. . \ scannin~ electron nlicroscope examinatit)n of sil,,er cones removed from endodontica[l':, u'ealed teeth. Oral Surg 33:589-605, 1972.

Fig 1- Photomicrograph of experimental materml (fil/er/.re(d~'r). N,te cl(~se adap- laDon qf c.x-p,,rinlental material l , root ca- flat.

Fig 2 t~holograp]l .~how,r experzmental roarerm/ (filh'r .waler2 with control mate- rzal. I.CI?, expcrlnlental, and right, control tooth.

4. Megam M.M.: Grant, A.A.; Co, robe, E.C. .k rtewly de,;igned rnot canal Idling material. Br Dcnt,] 1189-11, 1980.

5. t:ot~cl, B.B. A cnnnparative study <.f live material'.: h,r use in Iillin~ rooE ,.anal spaces. Oral Sun'g 43:284-2<)9. 1977.

6 . . \1 Rafei, S.. and Moore, I). Marginal pel'lell'illiOl'l ot ,.'lm'q)osite leSin restoriltioDs a s

indi<awd hy a tracer tire. ,J Prosflwt Dent 34:435--139, 1<)75.

7 . . \ in ley, J.F. Fluorometric assay of the apical seal of root <'anal lillings. Oral Surg 29:733-762, 197().

8. Younis, {)., and I lembree, ,I.H. Leakage . f diilerent root canal sealants. Oral Surg 41:777-784, 1976.

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