International Endodontic Journal 0991] 26, 301-305

The penetration of root canal sealers into dentinal tubules. Ascanning electron microscopic studyT, OKSAN, B, 0, AKTENER, B, H. 5EN& H. TEZELDepartment ofEndodontics, Ege Urtiversity Dciitoi Faculty, Bornom, Izmir, Turkey

Summary

The purpose of this study was to evaluate the effect ofsmear layer on penetration of four root canal sealers intodentinal tubules.

Sixty-four, recently extracted, human maxillar}' andmandibular incisors were used. Following removal ofthecrowns, the pulps were extirpated and the root canalsinstrumented. The teeth were then divided into twogroups, The teeth in the control group were irrigated withsaline solution and the experiment^ group treated withEDTA and NaOCI, Each main group was then divided intofour sub-groups and the root canals illed with Diaket, N2Universal, SPAD and Forfenan as recommended by themanufacturers. The teeth were split longitudinally andexamined using scanning electron microscopy, A quanti-tative assessment was made of sealer penetration Into thedentinal tubules in the coronal, middle and apicai partsof each root canal.

It was observed that the smear layer obstructed thepenetration of the tubules by the sealers. However, inthe experimental group, the penetration into dentinaltubules was better with Diaket, N2 and SPAD, than withForfenan (P< 0,01),

It was concluded thai this penetration could beaffected by physical and chemical properties of root canalilling materials.

Keywords; dentinal tubules, root canal sealers, scanningelectron microscopy, smear layer.

Introduction

The smear layer has been an important factor in rootcanal therapy since the report of McComb & Smith(1975), They reported that it was a layer of materialwhich covered the prepared canal walls and occludedthe dentinal tubules, Goldberg & Abramovich (1977),Wayman et al. {1979} and Berg et al (1986) suggested

Correspondence: Dr Bekir 0. Aktener, Ege Oniversitesi, Dl^hefciraligiFakultesi, Bomova Kampiisii, Izmir, Turkiye.

i'ig. 1. Longitudinal view of a specimen from the control group will:Diaket. Note the openings of dentinai tubules are obstructed witb -iziwcrmaterial (arrows) and the tisbules are empty (SEM magaification:

that the smear layer might prevent the penetration ofintracanal disinfectants and filling materials intodentinal tubules, Yamada ct al (1983) reported thatthis layer might interfere with the adaptation of fillingmaterials to the root canal wail, Abramovich & Goldberg(1976) showed poor penetration of AH26 and Diaket Ainto the dentinal tubules, but the presence of smear layerwas not considered in that study.

Irrigation of root canals ivith EDTA followed by NaOClsolution has been shoivnto be very effective in removingthe smear layer (Goldman et al. 1981, Yamada et al.1983, Baumgartner & Mader 1987), It has been statedthat removal of the smear layer might improve theobturation of gutta-percha cones with sealer and lateralcondensation (Kennedy et ai. 1986). White ct al. (1984)reported that two plastic root eanal filling materials wereable to enter into the dentinal tubules after removal ofthe smear layer.

301

302 T. Oksan et al.

Fig, 2. Longitudinal view ofa spedmen from the control group with N2Universal. Note the dentinal tubules nearbj' the filling material areempty fSEN-I magnification: xl 600) (fX = dentiaal tubules; S = sealer).

Fig. 3, Longitudinal riew of a spedmen from the control group withSPAD. Note the dentinal tubules nearb}- the Wiling material are empty(SBM magoification: x] 600).

This Study was performed in order to ei^aluate theeffect of smear layer on penetration of different rootcanal sealers into dentinal tubules.

Materials and tnethods

Sixty-four sound human, recently extracted, upperand lower incisors were used in this study. The crownswere removed at the amelo-cemental junction and thepulps extirpated with broaches. The roots w ere groovedlongitudinally on the buccal and lingual surfaces. A size15 file was then inserted into the root canal until it wasseen at the apical foramen; 1 mm was subtracted fromthis length in order to determine the working length.Standard instrumentation of the root canals was per-formed hy using size 1 5-50 K-type files with circumfer-ential filing (Weine 1989). Irrigation tvith 1 mlof5,25%NaOCI v 'as used between each instrument. After com-pletion of instrumentatioa, the teeth were randomlyapportioned into two main groups as control and exper-imental. The teeth in the control group were irrigatedwith 20 ml of saline solution by using a 2 5-gauge needleplaced up to tivo-thirds of the length of the root canai.The teeth in the experimental group ivere irrigated with10 ml of EDTA (disodium salt of EDTA, 1 7 g: 5 N sodiumhydroxide solution, 9.25 ml: distilled water, 100 ml)followed by 10 ml of 5.2 5 % N aOCl in the same manneras described for the control group. After irrigation, theroot canals were dried with paper points. Each maingroup was then divided into four sub-groups accordingto the sealer used.

The canals in sub-group ] were filled with DiaketlEspe Gmbh: Seefeld, Germany), sub-group 2 with N2Universal (Indrag Agsa SA, Losone, Switzerland), sub-group 3 with SPAD (SPAD, Quetigny, France) and sub-group 4 with Forfenan (Septodont, St Maur, France) byusing a spiral filler rotating at 5000 r,p,m, in a contra-angle handpiece. Manufacturers' recommendationswere followed during mixing and filling.

The access cav'ities were closed with Cavit (Espe Gmbh,Seefeld, Germany) and the filling materials were aliotvedto set for 48 h at 37°C and 100% humidity. The teethwere then split carefully into two halves with a hammerand chisel. The paired halves were prepared for scanningelectron microscopic evaluation. The specimens werevacuum-dried, coated with gold and viewed with aCambridge Stereoscan S-410 electron microscope(Cambridge, UK). The penetration of filling materials intodentinal tubuies was examined and an assessment madeas to whether the material in the dentinal tubules wassealer or smear plugs by comparing it with the bulk ofthesealer in the root canal.

All specimens were completely examined and photo-micrographs were taken from the coronal, middle andapical thirds at xlBOO magnification. The penetration

Penetration of sealers into derttinal tubules 303

Table I, Distribution of penetration scores in the experimental groups (n = 8)

Coronal Midtile Apicai

0

000K

I

0000

2

01J0

3

5750

4

3000

0

000

s

1

0030

2

0030

3

7640

4

1200

DiaketN2SPADForfenan

0 0 4 4 00 1 7 0 00 4 4 0 08 0 0 0 0

I'ig. 4, Uingitudinal view of a specimen from the e.\'per!mental groupuith Diaket. Difluse penetration ofthe filling material (arrows) can beclearlv seeti (SEM magnification: xl 6001.

• '':7WlB^WJ:M

Fig. 5. Another speciir.en Irc.iii iW e>:p;Ti:iu-i-.;j. group with Diaket.The orifices ofthe dentii-.ul tLic iiii's ;.re (i:;tT. v •::'. the fiUiog material(SEM magnification X,MI.1'.

into tubules in each third ofthe root canal was graded asfollows 0: no penetration: 1: 1-20 microns; 2: 2 1 ^ 0microns; 3; 41-60 microns; and 4; more than 60microns. The mean of 10 readings (representing maxi-mum penetration) was taken in each part of the rootcanal, A non-parametric ANOVA test (Kruskal-Wallis)was used to find the statistical differences among theresults obtained from sealer groups and different regions.

Results

ControJ groups

The teeth in these groups which were irrigated withsaline solution showed varying degrees of smear layerdepending on the contact of the instruments with

dentine walls. While penetration of smear layer into den-tinal tubules was observed in some areas, no penetrationof sealer could be seen (Figs 1-3).

Experimental groups

The experimental teeth, where the smear layer had beenremoved, showed penetration of tubules by the sealers(Table 1, Figs 4-7). The penetration of Forfenan wassignificantly less than other sealers in all areas (P < 0.01).While Diaket showed significantly deeper penetrationthan N2 Universal and SPAD in all thirds (P<0,05)except N2 Universal in the middle portion, there were nosignificant differences between the coronai and apicalthirds for N2 Universal and SPAD (P>0.05), Tubular

304 r, Oksan et al.

• ' . " - ^

. • . / ' • ' • : •' ^ v . . • • • • • : ? ^ ' ' - ^ ' ' j - '

' ' • '.'•.•• • ' • - ' - . - " . • • > •

I . . .

Fig, 6, A specimen from the experimental group with SPAD, Diffusepenetration of the filling material (arrows) can be dearly seen (SEMmagnification: xl600).

Fig, 7, A specimen fron, ;-i. . •!! ' u i , : : ,: I'l •i:;! " • thFor fenan . Thereis no penetrat ion of t'lv ,:i! i r ,'i..'i . ! • '•i?tina! tubules (SEMmagnification: x l 6 0 0 | .

penetration by Diaket, N2 Uni\'ersal and SPAD in theapicaj third region was also significantly less than thepenetration in the coronal third (P < 0,01).

Discussion

None of the sealers penetrated into dentinal tubules inthe control groups. This was expected as the smear layeroccludes the dentinal tubules. White et al (1984, 1987)found similar results with plastic filling materials. Theystated that the presence of smear layer prevented theentry of the filling materials into dentinal tubules. Afterroot filling with gutta-percha and zinc-oxide/eugenolsealer, Lester & Boyde (1977) observed that the sealercould not penetrate the tubules owing to the presence ofblocked dentinal tubules by smear material.

The irrigation with EDTA folioived by NaOCl removedsmear layer effectively io this study and confirmed otherstudies (Goldman et al. 1981, Yamada et al 1983,Baumgartner & Mader 1987), After removal of thislayer, Diaket, N2 Universal and SPAD showed tubularpenetration to some extent. Since Forfenan could notpenetrate into dentinal tubules, it was considered thatflow of this material was inefficient and its surface activitywas not low enough to enter Into the dentinal tubules.After studying with surface-active reagents, Aktener efaZ.(1989) concluded that root canal filling materials shouldhave low surface activity or an adequate surface-activereagent should be added to them io order to obtain opti-mum penetration, but using a paste or sealer only, rootfilling may have major disadvantages clinically (Ingle1985). If lateral or vertical condensation techniqueswith gutta-percha points had been used in this study, thepenetration of the sealers into deotinal tubules mighthave been improved.

The results ofthe study suggest that the chemical andphysical characteristics of root canal sealers may affecttubular penetration and adaptation of the material tothe root canal m'all following the removal ofsmear layer.As concluded by Cergneux e,i al (1987), increased sur-face contact between root canal wall and the sealer mayimprove the apical seal.

Conclusions

This study makes the following conclusions:(1) The presence of smear layer prevented the pen-

etration of root canal filling materials used in thisstudy into dentioal tubules.

(2) After the removal of smear layer, the penetrationinto dentinal tubules was better with Diaket, N2Universal and SPAD, but not with Forfenan

(3) Chemical and physical properties of the root canalfilling materials may aflect tubular penetration inthe absence of smear layer.

Penetration of sealers into dentinal tiAules 305

References

ABKAMOVICH A , GoUHiERG F (1976) Tbe relationdiip ot flie root canalsealer to the denllne waJl. An in vitro study using the scuiningelectron microscope, loumal of the British Eniodontic Society 9,81-86.

AKTENER BO, CENGIZ T, PisHN B (1989) The penetration of smearmateriai into dentinal tubuies during instrmnentation with surface-active reagents. A scanning electron microscopic study. Jotimai ofEndfflimtics 15, 588-90,

BAUMGAKTNKR JC, MADER CL (1987) A scanning electron microscopicevalaation of four root canal irrigation regimens. Jourrud of Endo-donfies 13,147-57.

BERG MS, JACOBSEN EL, BEGOLEEA, REMEUOS N A (1986) A comparison

of five irrigating solutions. A scanning electron microscopic study.Journal o/EnAjdontics 12,192-197.

CERGNEUX M, CinccHr B, Dreisou JM, HOLZ j (1987) The influenceof the smear layer on the sealing ability of canal obturation,IntermtiotMl Endodontic pumcH 20 ,228-32,

GoLDBEKG F, ABRAMOVICH A (19 7 7) Analysis of the effect of EDTAC onthe dentinal walls ofthe root canal, lourmi ofEndodontics 3 ,101-5.

GOLDMAN LB, GOLDMAN M, KRONMAN JH, LIN PS (1981) The

efficacy of several irrigating solutions for endodontics. A ScanningElectron Microscopic study. Oral Surgery. Oral Medicine and Ora!Pathology 52.197-204.

INGIE JI {1985) Endodontics. 3ni edn. Philadelphia: Lea and Febiger,p. 245.

KENNEDY, WA, WALKER WA GOUGH RW (1986) Smear layer removaleSects on apical leakage. Journal ofEndodontics 12,21-7,

LESTER KS, BOTOE A (1977) Scanning electron microscopy of instru-mented, irrigated and filial root canals. British Dental /ouma! 143,359-67.

McCoMB D, SMITH DC (1975) A [Heliminary scanning electron micro-scopic study of root canals after endodontic procedures. JourTial cfEi^odontics 1,238^2.

ROME WJ.DORANJE, WALKER WA (1985) The effectiveness of giy-ondeand sodium hypochlorite in preventing smear layer formation,loumsIofEnJodonticsll, 281-8.

WAYMAN BE, Koir WM, PINERO GJ, LAZZABI EP (1979) Citric andlactic acids as root canal irrigants in vitro. Joumet ofEndodontics 5,258-65.

WEINE PS (1989)Bndo<fc'nticTherap!(, 4th edn, St Louis: C. V, Mosby Co..pp. 278-9.

WHITE RR. GOLDMAN M, LIN PS (1984) The influence of the smearedlayer upon dentinal tubale penetration by plastic filling materials.joumai of Endodontics 10, 558-62.

WHrra RR, GOLDMAN M, LIN PS (1987) The influence of thesmeared layer upon dentinal tubule penetration by endodontic iillingmaterials. Part E. Joumai ofEndodontics 13, 369-74.

YAMADA RS, ARMAS A, GOUIMAN M , LIN PS (1983) A scan-

ning electron microscopic comparison of a high volume final flushwith several irrigating solutions. Part 3. Joumai of Endodontics 9,137-^2.