J. oral Path. 1972:1: 244-248

Scanning electron microscopy ofcalcium hydroxide induced bridges

M. ULMANSKY*, J. SELA* AND M . SELA**

Departments of Pathology* and Oral Diagnosis**, The Hebrew UniversityHadassah Medical School and Hadassah Scliool of Dental Medicine, Jerusalem, Israel

Abstract. Calxyl, a commercial prcparalion of calcium hydroxide, induces the formation of acalcified bridge on the denial pulp after pulpolomy. Since Ihe quality of such bridges is not al-ways the same, it was felt necessary to study bridge structure by means of the scanning eteclronmicroscope.

The present results are observations made wilh tho aid of scanning microscopy on three speci-mens which revealed that calcium hydroxide induced bridges present large defects and a paiticulartopography.

Received 27 September, aeeepted for publication 31 October 1972

Calxyl, (Otto and Co., Frankfurt on Main,Germany), a commercial preparation ofcalcium hydroxide, itiduces the formationof a calcified bridge on the dental pulpafter pulpotomy (Glass & Zander 1949, Cas-tagnola & Orlay 1950, Brindsen 1955, Ny-borg 1955, 1958, Mitchell 1961, Ulmansky& Langer 1967, Langer, Ulmansky & Sela1970, Ulmansky et al. 1971).

In a previous study (Langer et al. 1970)it was found that Calxyl induced bridgeformation in all the teeth studied. Thesewere found to consist either of osteodentinor tubular dentin. Although two-thirds ofthe bridges induced by Calxyl were of thetubular type, structural defects were ob-served.

In order to obtain more informatioti onthe structure of calcium hydroxide inducedbridges, scanning electron microscopy wasemployed.

Materials and methods

This study was performed on three soundmandibular third molars of different adultpatients whose teeth were scheduled forextraction because of repeated episodes ofpericoronitis. Pulpotomy was performed intwo of them using the technique previouslydescribed by Langer et al. (1970). In thethird specimen, the pulp was exposed byperforating the roof of the pulp chamber.Following the surgical procedure, pulps ofall three teeth were dressed with Calxyl®which was then covered by a layer of zinc-oxide-eugenol cement. Care was taken toavoid any pressure on the pulp. A silveramalgam completed the treatment. Theteeth were extracted five weeks later. Radio-graphs of the tooth were taken before andafter treatment, before extraction and,finally, after extraction. The teeth were

ELECTRON MICROSCOPY OF INDUCED BRIDGES 245

sectioned horizontally at two different levels,one coronal and the other apical to thebridge (Fig. 1). The location of the cuts wasbased on infonnation derived from the roent-genographs. In each of the two specimenswhich were subjected to pulpotomy, one ofthe lateral walls surrounding the dentinalbridge was removed by fracture for the pur-pose of cross-sectional studies. Organic ma-terial was removed from the specimens byimmersion in a solution of Bio-Or soap(Shemen Co., Haifa, Israel). Bio-Or soap is

: a commercially available enzyme containingdetergent which in pilot studies proved tobe effective in eliminating organic material•without any corrosive effects on the calci-fied dentinal structure. The specimens werecoated with gold by means of a vacuumcoating device having a tilting-rotary jig(Ivlicroprep 300 Coating Unit, NanotechLtd . , Urmston, Lancshire, England) after•which they were examined with a S4 Stereo-s c a n (Cambridge Instrument Co. Ltd., Cam-bridge, England).

Lettering is common lo all figures as follows:(A) apical side of tiridge, (G) peripheralgroove, (H) pulp horn, (DB) dentinal bridge,(D VV) dentinal wall, (RC) radicular canal,(PCR) pulp chamber roof.

A >

ZOE

C I

B r

and 2

fo r

Amalg«n

• Zinc«ug«

Cal xyl

n

OKide-n o l

Br idge

: StctI

spfc imton planesn prrparation

The study was made on the apical andcoronal faces of the bridges as well as onthe fractured cross-sectional surfaces.

Findings

The apical surfaces of the bridges werefound to be convex, with evenly distributed.

Fig. 2. Lateral-coronal view of the bridge ofone of the teeth after pulpolomy. X 21.

Fig. 1. Diagram showing treatment given andspecimen preparation.

F/i,'. 3. Higher magnification of lateral-coronalview of bridge of Eig. 2. Note the wide defectsin the bridge structure (arrows). X 55.

246 ULMANSKY, SELA AND SELA

smooth, round prominences (Figs. 2-4).Tubular endings were concentrated ingroups. The tubules were irregular in size,ranging between 2 and 5 mj.i in diameter(Fig. 5). A well defined groove delineated the

bridges at their attachment to the detitinwail (Figs. 2-4 and 6). Large defects wereobserved in the structure of the bridges,especially in the vicinity of the peripheralgrooves (Figs. 4 and 6). The defects were

Fig. 4. View of apical side of bridge of molarin which a perforation was done on the roofof the pulp chamber. The peripheral grooveis pointed to by an arrow. X 16.

Fig. 6. Higher magnification of peripheralgroove and defects of the dentinal bridge ofFig. 4. Arrows point toward defects. X 405.

Fig. 5. Aptcal surface ol dentin bridge fromprevious figuie Note variability in shape anddistribution of dentinal endings. Arrows pointtowards small tubular concentrations. X 405.

Fig. 7. Corono-lateral view of the bridge fromthe second pulpotomized tooth. Note theperipheral defects and funnel shape. X 95.

ELECTRON MICROSCOPY OF INDUCED BRIDGES 247

generally round or elliptic and varied insize, averaging 25 mj i in diameter. Exami-nation of fractured cross-sectional surfacesrevealed a cribiform appearance of thebridges with defects communicating be-tween tbe coronal and apical surfaces.These were irregular in shape, distribution

I a n d orientation (Fig. 3).

Fig. 8. Higher magnification of a peripherala rea of bridge from Fig. 7. Arrows point to-ward the large defects. X 475.

The coronal faces of the bridges wereconcave or flat and merged obliquely attheir peripheries into the dentinal walls re-sulting in a funnel shape (Fig. 7). Thisperipheral oblique wall contained large de-feets similar to tbose of the peripheralgroove on the apical side, but they averaged45-50 m|.i in diameter (Figs. 8 and 9) .

Fig. 9. High power view of an area of theprevious figure. Note size and shape of thedefects. X 950.

Discussion

Although the present work is based on onlya small number of speeimens, eertain gen-eral conclusions may be drawn. The calciumhydroxide indueed bridges are funnel-sbaped, their convexity apically oriented.Large defects occur in the bridges. Thesedefects are concentrated at their peripheries.The coronal and apical surfaces of thebridge present irregular groups of tubularendings. These findings are in keeping withthose of Schroder & Granath (1972).

The fractured eross-sectional surfaces re-vealed that the bridges contain many de-fects which give it a sponge-like appear-ance. This indicates an irregular appositionof the dentin.

The observation that the defects on thecoronal surface are larger than those onthe apical surface suggests that the qualityof the bridge improves as tbe odontoblastsmigrate apieally with the apposition of den-tin. The direct clinical consequence of thisobservation is that, with time, the bridgeshould become tbicker and less porous,tbus lowering the thermal, ehemical andelectrical conductivity of the bridge as wellas increasing its mechanical strength to re-sist pressure exerted during filling conden-sation.

Acknowledgment

We would like to express our thanks toMr. Talmon Arad who helped us in the useof the scanning electron rnicroscope.

248 ULMANSKY, SELA AND SELA

Editor's note

The editor wishes to express regret that anagent "Bio-Or soap" was employed for seien-tifie investigations inasmuch as constituents ofthe soap are a trade secret. Hopefully, the useof reagents of unknown content for seientificinvestigations will remain minimal. In re-sponse to a query from tlie editor, the follow-ing information was obtained from the au-thors:

The Bio-Or soap is a local (Israel] commer-cially available enzyme-containing powdersoap. According to the manufacturers, itcontains sodium carbonate, sodium bicarbo-nate, silica, didodecylbenzene-sulfonate, 3-poly-phosphate and a mixture of proteolytieenzymes manufactured by Proctor and Gani-bel. The types of enzymes and their constitu-ents are a trade secret. We used this soap as iteliminated the organic matter without cor-roding the surface of the dentin. The digestionwas carried out in 30 % aqueous solution forsix hours at a temperature of 37° C. The pHof the solution was 9.7.

References

Brindsen, G. I. (1955) Study of the rcparativepowers of the mature dental pulp followingpartial amputation as a treatment for ex-posure by dental caries. Northwestern Uni-versity Bulletin, Dental Research and Gra-duate Study 56, 4.

Castagnola, L. & Orlay, H. G. (1950) Direetcapping of the pulp and vital amputation.British Dental Journal 88, 324-330.

Glass, R. & Zander, H. A. (1949) Pulp heahng.Journal of Dental Research 28, 97-107.

Langer, M., Ulmansky, M. & Sela, J. (1970)Behaviour of human dental pulp to Calxylwith or without zine-oxide-eugenol. Archivesof Oral Biology 15, 189-194.

Mitchell, D. F. (1961) Pulp reaction to com-monly used capping materials. Journal ofDentistry for Children 28, 150-153-

Nyborg, H. (1955) Healing processes in thepulp on capping. Acta Odontologiea Scan-dinavica 13, suppl. 16, 106.

Nyborg, H. (1958) Capping of the pulp, theprocesses involved and their outcome. Odon-tologisk Tidsskrift 66, suppl. 4, 296.

Schroder, U.& Granath, L. E. (1972) Scanningelectron microscopy of hard tissue barrierfollowing experimental pulpotomy of in-tact human teeth and capping with calciumhydroxide. Odonlotogisk Revy 23, 211-220.

Ulmansky, M. & Langer, M. (1967) Reactionof dental pulp to Ledermix and Calxyl.Israel Journal of Medieal Sciences 3, 739-746.

Ulmansky, M., Sela, .1., Langer, M. & Yaari,A. (1971) Response of pulpotomy wounds innormal human teeth to successively appliedLedermix and Calxyl. Archives of Oral Bio-logy 16, 1393-1398.

Address:Professor M. UlmanskyDept. of PathologyHadasxah Medical SchoolPOB 1172Jerusalem, Israel