Simple metallic compounds as pulp-capping agents A. Watts, B.D.S., DEPARTMENT

and R. C. Paterson,

OF CONSERVATIVE

A study is described in which tested as pulp-capping agents cupric oxide, ferric oxide, and favorable results and is being

DENTAL

M.D.S.,

London,

England

SURGERY, GUY’S HOSPITAL

six metallic compounds identified in a previous pilot experiment were using the exposed rat molar. Barium sulfate, calcium carbonate, heavy magnesium oxide gave poor results. Stannic oxide gave more studied further.

1n a previous

report’ a pilot study was described in which a range of simple compounds were screened as pulp-capping agents. Twelve compounds were selected from a range of topical medicaments in use in general medical practice. Six of these compounds were considered to merit further study -barium sulfate, calcium carbonate, cupric oxide, ferric oxide, heavy magnesium oxide, and stannic oxide. In the pilot study four rat molar teeth were treated with each medicament. In this more detailed experiment a minimum of twentytwo teeth were examined per compound. METHODS

Ph.D.,

AND MATERIALS

were stained with hematoxylin and eosin and examined under low and high magnifications for: 1. Inflammation and/or necrosis in (a) the coronal pulp, (b) the root canal, and (c) the apical tissues. 2. Calcification as (a) a bridge at the exposure site, (b) calcification in the coronal pulp, and (c) calcification in the root canal. A bridge was scored only where 75 percent of the sections examined had calcific material at the exposure site. This system of scoring was first described by Rowe3 and allows simple comparison of numerical data. RESULTS

Albino rats, 8 weeks old, of the Fischer strain,* were used in this study. They were anesthetized with a Fluothane-oxygen mixture for both induction and maintenance, as described by Paterson and Rowe.’ Cavities were prepared in the first and second maxillary molar teeth with a No. 33% inverted-cone bur. The pulps were exposed, irrigated, and dried with paper points. The test medicaments were mixed to a thick slurry with distilled water and lightly tamped down with a damp paper point into contact with the exposed pulp. A Dycalt lining was placed and the cavities were sealed with silver amalgam. The animals were killed after 28 days, and the maxillary molar teeth were dissected out in blocks which were decalcified and processed for wax-embedding in the usual manner. Serial sections 8 microns thick were cut in a mesiodistal plane through the molar teeth. They

Only teeth in which the amalgam fillings were retained were scored and included in the results. A summary of the numerical data is given in Table I. Also included in Table I are results obtained for Dycal and zinc oxide obtained previously by similar methods. Stannic oxide gave the best results of the compounds tested, with seventeen of the twenty-four teeth examined having dentin bridges present. There was, however, some evidence of necrosis in the coronal pulp adjacent to the material, which in some specimens extended into the root canal immediately beneath the exposure site. All of the other materials tested produced extensive necrosis, and less than half of the treated teeth had dentin bridges present.

Based on a paper presented at the British Division, International Association for Dental Research, Liverpool, UK, 1974. *Charles River Breeding Laboratories, Wilmington, Mass. tL. D. Caulk Co., Ontario, Canada.

The results from this study provide further support for our view that the rat molar provides a suitable model for the initial screening of pulp response to base and lining materials. Once again, careful examination

0030~9220/79/120561+03$00.30/00 1979The C. V. Mosby Co.

DISCUSSION

561

562

Watts and Paterson

Oral Surg. December, 1979

Table I. Results Calcijicafion

InjZammationiNecrosis

No. of teeth

Coronal pulp

Root

Apical tissues

Calcium carbonate Barium sulfate Cupric oxide Ferric oxide Heavy magnesium

26 24 23 25 27

25 24 23 25 27

25 22 28 23 26

3 I 4 5 3

12 II 8 9 13

I5 13 8 8 I3

8 9 8 9 8

oxide Stannic oxide

24

24

18

2

17

II

6

Previous data reported by Paterso@ Dycal Zinc oxide

24 24

19 6

7 3

2 0

20 20

Material

of serial sections of teeth was found to be essential to detect inflammation, necrosis, and defects in dentin bridges. It was not unusual to find that superficial sections demonstrated an apparently favorable result but that deeper sections from the same tooth showed a poor response. In these trials the response has been examined after 28 days only. This time interval was chosen because in our experience calcific repair has usually occurred in the rat molar by 21 days and, as Rowe3 has reported, it is difficult to maintain retention of amalgam fillings in rat molars for longer than 30 days. There is some disagreement in the literature regarding the significance of the various tissue changes such as those observed in this trial. Some authors consider tissue necrosis at the wound surface to be a necessary precursor of tissue repair. Previous studies4-6 have shown the presence of persistent chronic inflammation in the pulp even where calcific repair has occurred. In trials of this type, an attempt is being made to give a long-term prognosis for the pulp following specific therapeutic regimes, on the basis of the observed response after a given time interval. Much remains to be elucidated about the significance of inflammation in the pulp. Naidorf7 stated that without inflammation, healing could not occur. We do not regard a limited amount of superficial necrosis of pulp tissues in contact with a medicament as necessarily being indicative of a poor prognosis. The assessment of the significance of calcification of the dystrophic or amorphous types presents difficulties. In most examples where a dentin bridge was present, irregular calcification was present at the exposure site as described by Massler.R In many examples where there was extensive necrosis of the coronal pulp, large amounts of amorphous calcific material were present in the root canals. The presence of reparative dentin is regarded as an indicator of good prognosis, since odontoblasts are delicate cells requiring optimal conditions to function.

Bridge

crown

0 I

Root

9 2

We believe that by detailed testing of simple metalliccompounds an understanding of the action of the more complex pulp-capping products in general clinical use can be achieved. However, it must be remembered that the method employed constitutes a severe test, in that the pulpal response to direct contact with the pure compounds is being observed. This may provide an explanation of the poor results obtained in the pilot study with titanium dioxide, which is a constituent of Dycal. The manufacturer’s formula states that 45.1 percent of the base is titanium dioxide but that it is combined with calcium sulfate in a ratio of 1 :2.s It is interesting that in this trial the only really favorable responses were observed with stannic oxide. Data included from previous reports4. 5 shows that similar results were obtained with another simple metallic oxide, namely, zinc oxide mixed with water. Both of these compounds appeared to have success rates similar to that of Dycal. Further studies are in progress in which Dycal, stannit oxide, and zinc oxide, which have produced a favorable tissue response in the rat, are being tested in the dog. In order to give further indication of the comparability of the results between the two species, titanium dioxide, which gave a poor response in the rat, is also being tested in the dog. CONCLUSIONS

Detailed examination of the response of the rat molar pulp to six simple metallic compounds showed that a favorable response was obtained only with stannic oxide. We wish to thank the Endowments Committee of Guy’s Hospital Medical School for a grant for technical support. We gratefully acknowledge the continued support of Professor A. H. R. Rowe, Departmentof ConservativeDental Surgery, for the researchprogram of which this report forms a part. We would also like to thank Professor M. N. Naylor and Mr.

Simple metallic

Volume 48 Number 6 R. F. Wilson of the Dental Clinical Research Unit, Guy’s Hospital, for generous provision of facilities. REFERENCES

I. Watts, A., and Paterson, R. C.: Simple Metallic Compoundsas Pulp Capping Agents, ORALSURG.44: 285-292, 1977. 2. Paterson, R. C., and Rowe, A. H. R.: Surgical Anaesthesiain Conventional and Gnotobiotic Rats, Lab. Anim. 6: 147.152, 1972. 3. Rowe, A. H. R.: The Reaction of the Rat Molar Pulp to Various Materials, Br. Dent. J. 122: 291.300, 1967. 4. Paterson,R. C.: Bacterial Contamination and the Exposed Pulp, Br. Dent. J. 140: 231-236, 1976.

5. Paterson,R. C.: The Reaction of the Rat Molar Pulp to Various Materials, Br. Dent. J. 140: 93-96, 1976.

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agents

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6. Nyborg, H.: Healing Processesin the Pulp on Capping, Acta Odontol. Stand. 13: Suppl. 16, 1955. 7. Naidorf, I. J.: Correlation of the Inflammatory responsewith Immunological and Clinical Events, J. Endodont. 3: 223-228, 1977. 8. Massler, M.: Pulpotomy: A Re-Appraisal. Transactions3rd International Conference on Endodontics, University of Pennsylvania, 1963, pp. l-29.

9. Fisher, F. J., and McCabe, J. F.: Calcium Hydroxide Base Materials, Br. Dent. J. 144: 341-344. 1978. Reprint reqursr.~ to:

Dr. A. Watts Department of Conservative Dental Surgery Guy’s Hospital

London SE1 9RT, England

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Simple metallic compounds as pulp-capping agents.

Simple metallic compounds as pulp-capping agents A. Watts, B.D.S., DEPARTMENT and R. C. Paterson, OF CONSERVATIVE A study is described in which tes...
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