Pulpal reaction to composite resin restorations

Pulpal reaction

to composite

resin restorations

Martin Brtinnstriim, Odont. Dr.,* and Hilding Nyborg, Odont. Dr.** Karolinska Institutet, Stockholm, Sweden, and University of Umea”, School of Dentistry, Umea”, Sweden

A report of their \/ omposite resin materials appear to be gaining in popularity. physical properties implied that they are superior to silicate cement and the coldcuring acrylic resins. In somesituations composite resin materials are suitable for use in the restoration of posterior teeth.l Histologic studies of the effect of composite resin materials on the pulp are few and are concerned mainly with Addent 35t-the first such material to appear on the market. It has been suggested that the pulp reaction to this resin may be slightly less “severe” than to other cold-curing materials, and it was apparently difficult to find an effective liner that would prevent reactions to the Addent 35.* Stanley, Swerdlow, and Buonocore3 found that without a liner this material gave a mild response at first but that it increased in intensity with time. They considered that the proved polyvinyl cavity liner recommended for Addent 35 did not always provide adequate protection of the p~lp.~ In another study conducted by Baume and FioreDonno, pulp injury was found to be particularly severe under deep cavities with Addent 35, and the polyvinyl liner recommended by the manufacturer did not protect the pulp, though calcium hydroxide paste did. Sayegh and Reed5 studied the response beneath 36 Blendantl fillings in human teeth and, as a rule, found a mild response. No histologic examinations of the effect on the pulp of the new materials Addent 12 and Adaptics appear to have been published. The question of whether these materials are acceptable from the biologic aspect remains unanswered, and this applies to whatever kind of protection is used should damage to the pulp occur. In a separate study, 6 bacteria were detected on the walls of 56 of 66 unlined cavities restored with Adaptic, Addent 12, or DFR.11 Under 19 of these restorations, bacteria were observed in the dentinal tubules and in the pulps of three teeth. Only with *Department **Department tAddent

of Oral Histopathology. of Endodontics. 35 : Minnesota

$ Johnson

& Johnson,

§Kerr

Manufacturing

jjDFR:

Surgident

Mining New

Company, Otro,

and

Mfg.

Brunswick,

Surgident

Co., St. Paul,

Minx

N. J.

Detroit, Ltd.,

Mich. Los Angeles,

Calif.

181

182

Briinnstriim

J. Prosthet.

and Nyborg

February,

Dent.

1972

Addent 12 were there no bacteria present under 10 fillings. Beneath none of the lined cavities in the contralateral teeth were bacteria seen in the tubules or on the cavity walls. The objectives of the present study were (1) to ascertain whether there is likely to be pulp reaction under the composite resins Adaptic, Addent 12, and DFR, when such fillings are placed in deep cavities, and (2) to ascertain whether a particular polystyrene liner, Tubulitec,” may provide an effective protection. MATERIAL

AND METHOD

The study was performed on 66 pairs of contralateral permanent teeth from young patients. The teeth were to be extracted for orthodontic purposes. Uniform cavities, 2 mm. in diameter and about 2.5 mm. deep, were prepared on the intact buccal surfaces. To obtain the greatest clinical relevance, the cavities were made AS deep as possible, since in clinical practice, the remaining dentin may be extremely thin without the dentist being aware of it. It is important to know the pulp response to restorations in deep cavity preparations and, if pulp injury is likely to appear, how the risk can be eliminated. If no injury occurs under deep cavity preparations, there is no need to provide protection in shallow ones. After the cavities werr prepared in each pair of teeth, the one to receive the cavity liner was randomly chosen. This cavity was flushed with water, and dried with absorbent paper and a 5 second air blast. A drop of Tubulitec liner was deposited in the cavity and immediately spread with compressed air, a technique that has been found to give a thin film of the liner about 5 microns thick.? A second drop of the liner was placed in the cavity, and allowed to evaporate under a gentle air blast. The second layer formed a layer about 20 microns thick on the cavity floor. The barely discernible film deposited on the margin of the cavity was not removed. The lining material was chosen on the basis of earlier results, which showed that this polystyrene liner is inert and provides adequate protection under phosphate cement, amalgam, and silicate.‘, 8 If the liner is to act as an efficient chemical barrier, all of the dentin with the tubules leading to the pulp must be covered. The same holds true if the cause of puIp damage is poor adaptation. The lining should cover the entire dentin surface and remain adherent to the dentin if the restorative rnatprial contracts. The cavity in the contralateral tooth remained unlined. The filling material to be used was mixed in accordance with the manufacturer’s instructions and placed in the cavity with excess. Then the matrix$ was applied with light pressure for a few seconds and trimmed on both sides, after which it remained in place untouched. No finger pressure was used during setting, as any resulting movement of the matrix might impair the adaptation. After 10 and 20 minutes, any excess was gently ground away by slowly running a diamond wheel along the margin while applying a water spray. The teeth were extracted after 1 to 2 weeks and 4 to 8 weeks. Prolonged observation times to see *Tubulitec: Brooklyn, N. Y. tG.

Forssbergs

Johnson:

*Hawe’s

Buccal

Personal Matrix

Dental

AB,

communication. No.

73 C.

Stockholm,

Sweden;

Buffalo

Dental

Magn.

Company,

Pulp

reaction

to composite

resin restorations

Fig. 1. Microorganisms between a DFR restoration and the dentin. The organisms the dentinal tubules and the decomposed pulp. The same tooth as Fig. 2. Table

I. The distribution

of the number

of pairs with different

Postoperative 1-2

Adaptic Addent 12 DFR Total

weeks

restorative

183

also entered

materials

period 4-8

weeks 18

Total

14 8 6

10 10

32 18 16

28

38

66

whether the pulp survives are of little value in experiments of this kind.” It should suffice if the condition of the pulp can be reliably demonstrated after a short interval; if injury is then detected, the suspected material should be avoided or suitable protection should be provided. The distribution of tooth pairs by filling material and follow-up period is given in Table I. Adaptic was more often used because it may have physical properties superior to the other available materia1s.l) lo After extraction, two thirds of the root was cut off, the tooth was fixed in neutral formalin and decalcified in EDTA (ethylene diamine tetra-acetic acid). About 100 serial sections were cut through the center of the cavity and the pulp. All but six sections of each tooth were stained with hematoxylin and eosin; these six were stained with Brown and Brenn’P modification of Gram’s technique for microorganisms. The results from the examination of these sections have been reported elsewhere.6 The sections were examined without knowledge of the filling material

184

Briinnstrijm

Fig. 2. An unlined directly

beneath

Fig. 3. Lined period

J. Prosthet. February,

and Nyborg

DFR the cavity

DFR was 4 weeks.

restoration 4 weeks (C) . (x300.)

after

restoration in the contralateral There was loss of odontoblasts

insertion. tooth beneath

used or which cavity (of a pair) had been lined. in previous experiments by the authors.‘*, In

There

is an abscess

to that in the cavity

These principles

Fig. (C).

2. The (x300.)

in

Dent. 1972

the pulp

observation

have been applied

RESULTS The changes observed in the pulp and the mean distances from the cavity floor to the pulp are given in Tables II to IV. In 58 of the pairs (out of 66), of unlined cavities, there was inflammation. In 6 pairs, there was no infiltration in either tooth, and in 3 pairs, such cells occurred under both lined and unlined cavities. The 3 lined cavities showed evidence of negligible infiltration, with only a few scattered exudative cells (Figs. 1 to 7).

Volume Number

27 2

Pulp reaction to composite

Fig. 4. Unlined Adaptic restoration cells in the pulp beneath the bottom wall. The odontoblasts are reduced ness. (x36.) Fig. 5. Lined Adaptic observation period was of odontoblasts. (x36.)

Table II. DFR:

restoration 4 weeks.

32 restorations.

in the contralateral Beneath the deepest

Pulpal

tooth to that shown in Fig. 1. The part of the cavity there is a reduction

changes beneath

unlined Pulp

I-2

distance

from

floor

to pulp

185

4 weeks after insertion. There are numerous exudative of the cavity and the area corresponding to the cervical in number and the predentin slightly increased in thick-

I

Mean

resin restorations

(mm.)

and lined

cavities

changes

weeks

4-8

weeks

Unlined (n = 6)

Lined (n = 6)

Unlined (n = 10)

Lined (n = 10)

0.44

0.33

0.36

0.18

Exudative cells : Few Numerous

4 1

-

2 5

2 -

Reduced Increased Reduced

3 3 6

2

2 9 9

3 2

predentin predentin odontoblasts

186

Briinnstriim

and Nyhorg

J. t’rostbet. February.

Dent. 197?

Fig. 6. Unlined Addent 12 restoration. The observation prriod was 1 week, There are numerator exudative cells in the pulp beneath the cavity. The predentin and the number of odontoblasts are reduced. Aspirated cell nuclei are present in the dentinal tubules. (~1?!0.) Fig. 7. Lined Addent 12 restoration in the contralateral tooth to that shown in Fig. 6. The observation period was 1 week. The number of odontoblasts in the area of the cavity are Wduced. (x120.) Apart from these findings, and those reported in the tables, aspirated nuclei ~VCI‘O observed under 22 unlined and 3 lined cavities. In all but one of the teeth, this feature was found only in teeth extracted after one or two weeks (Fig. 6). DISCUSSION The most striking finding was the high frequency of bacteria fillingsF It is interesting to examine the possible causes of the pulp under the composite resins in this study. The two main factors to chemical irritation by the material and poor adaptation. Injury to odontoblasts have been reported as the chief potential source of

beneath unlined changes observed be considered are and aspiration of pulpal irritation.”

Vdume Number

27 2

Pulp

Table III. Adaptic

: 64 restorations.

reaction Pulpal

to composite

changes beneath

resin

restorations

unlined

and lined

187

cavities Pulp 1-2

Mean

distance

from

floor

to pulp

(mm.)

Exudative cells : Few Numerous Reduced predentin Increased Reduced

Table IV. Addent

12 : 36 restorations.

4-8

weeks

Unlined (n = 14)

Lined (n = 14)

Unlined (n = 18)

Lined (n = 18)

0.28

0.23

0.34

0.34

4 9 12 14

predentin odontoblasts

changes

weeks

Pulpal

-

-

9 9 2 17 13

8

changes beneath

unlined

1 10

and lined

cavities

I

Pulp 1-2

Unlined 1 (n=8) Mean

distance

from

floor

to pulp

(mm.)

0.19

Exudative cells: Few Numerous

3 4

Reduced Increased Reduced

3 7

predentin predentin odontoblasts

changes

weeks

4-8

1 Lined 1 (n= 8) 0.21

5

Unlined 1 (n = 10)

weeks 1 Lined ) (n= 10)

0.34

0.29

7 1

1 -

3 9 5

2 2 3

It seems logical to suppose, however, that this aspiration phenomenon may be an outcome of poor adaptation, since the tubules were open at the distal ends and the centrifugal flow may transport cells and cell remnants into the tubules.14 In addition, dehydration due to the filling material can increase the centrifugal flow.15 Dehydration during dentin removal will have the same effect. The aspiration phenomenon may, however, be disregarded as a source of pulpitis.lG Perhaps poor adaptation represents a more serious threat to the pulp than irritation by the actual material. So far as microleakage is concerned, it has been pointed out that composite resins are probably not superior to the conventional resins.l’ This view finds support in observations on Adaptic; a space of from 0.5 to 5 microns was measured between the filling and cavity at the cervical and occlusal walls, and between 2 and 20 microns at the pulpal wall. I8 There is reason to suppose that this space, which appears through shrinkage during polymerization, provides a route for the capillary flow of liquid, especially from the oral cavity. Bacteria or other irritants may be present in the cavity before the application of the filling material, but they may also gain entry through the capillary flow of saliva into the space. Our previous

188

Briinnstr6m

and

Nyborg

J. Prosthet. FPbruary,

Dent. 1972

observations of a thick dense layer of bacteria, at many places in an even film having a thickness similar to that of the width of the space, suggest that the space may be largely filled with bacteria (Fig. 1) . Bacteria can reach the pulp via the dentinal tubules and, moreover, bacterial products can easily diffuse to the pulp where the dentin is thin. Under unlined silicate cement restorations, we have found a similar thick layer of bacteria and penetration of these bacteria to the p~lp.~ Perhaps the most serious threat to the pulp, even under these fillings, is constituted by the space which ma) be filled with bacteria. If the tested composite resins in general exert any irritant effect, this would apply also to Addent 12 and to the same degree. However, the pulp reaction observed in our study was less marked for Addent 12 than for the others. From the previous study, we noticed that beneath Addent 12 there were no bacteria found in 10 cavities in 18 teeth; with the other materials, there were bacteria in all of the unlined cavities. The reason for this difference is obscure, but it is possible that Addent 12, more than Adaptic and DFR, undergoes expansion on absorption of water, with the result that the space between the filling and the cavity walls is reduced.* The liner we used gave good protection for the pulp and also prevented bacterial invasion (Figs. 3, 5, and 7). One explanation of this may be that this liner adheres to the dentin rather than to the restorative material. The fluid would enter between the lining and the restoration rather than between the liner and the tooth. In addition, the cavity liner contains bacteriostatic components, and bacteria already present might presumably be rendered innocuous by the lining material. In the pulp of the unlined teeth in 57 of the 66 pairs, cells of exudate were observed (Figs. 2, 4, and 7). Infiltration was not found in either tooth in each of 6 pairs and was found in both teeth in 3 pairs. CONCLUSIONS We conclude that a suitable liner must be used beneath these new composite resins for the same reason as for silicate cement and other materials where spaces may form between the filling and the cavity walls. References 1.

Lee, H. L., Jr., Swartz, M. L., and Smith, F. F.: Physical Properties of Four Thermosetting Dental Restorative Resins, J. Dent. Res. 48: 526-535, 1969. 2. Langeland, L. K., Guttuso, J., Jerome, D. R., and Langeland, K.: Histologic and Clinical Comparison of Addent with Silicate Cements and Cold-Curing Materials, J. Am. Dent, Assoc. 72: 373-385, 1966. 3. Stanley, H. R., Swerdlow, H., and Buonocore, M. G.: Pulp Reactions to Anterior Restorative Materials, J. Am. Dent. Assoc. 75: 132-141, 1967. of the Human Pulp to a New Restorative 4.. Baume, L. J., and Fiore-Donno, G.: Response Material, J. Am. Dent. Assoc. 76: 1016-1022, 1968. 5. Sayegh, F. S., and Reed, A. J.: Tissue Reactions to a New Restorative Material, J. ‘PROSTHET. DENT. 22: 468-478, 1969. 6. BrPnnstrijm, M., and Nyborg, H.: The Presence of Bacteria in Cavities Filled With Silicate Cement and Composite Resin Material, Swed. Dent. J. 64: 149-155, 1971. 7. BrHnnstriim, M., and Nyborg, H.: Dentinal and Pulpal Response. IV. Pulp Reaction to Zinc Oxyphosphate Cement, Odontol. Revy 11: 37-50, 1960. *K.

D. Jorgensen:

personal

communication.

Volume Number 8. 9. 10. 11. 12.

13. 14. 15. 16. 17. 18.

27 2

Pulp reaction to composite

resin restorations

189

of Pulpal Effect of Two Liners, Acta Odont. Brfnnstrijm, M., and Nyborg, H.: Comparison Stand. 27: 433-451, 1969. Shroff, F. R.: Effects of Filling Materials on the Dental Pulp. A Critical Review, J. Dent. Educ. 16: 246-259, 1952. Lee, H. L., Jr., and Swartz, M. L.: Scanning Electron Microscope Study of Composite Restorative Materials, J. Dent. Res. 49: 149-158, 1970. Brown, J. H., and Brenn, L.: Method for Differential Staining of Gram-Positive and Gram-Negative Bacteria in Tissue Sections, Bull. Johns Hopkins Hosp. 48: 69-73, 193 1. Brannstrom, M.: Physio-Pathological Aspects of Dentinal and Pulpal Response to Irritants, in: Symons, N. B. B., Editor: Dentine and Pulp, Edinburgh and London, 1968, E. & S. Livingstone, Ltd., pp. 231-246. Brannstriim, M., and Nyborg, H.: Points in the Experimental Study of Pulpal Response to Restorative Materials, Odontol. Tidskr. 77: 421-426, 1969. Johnson, G., O:gart, L., and Brannstriim, M.: The Centrifugal Liquid Flow in Dentinal Tubules Due to a Physiologic Pressure Gradient. To be published. Johnson, G., and Brlnnstrom, M.: Dehydration of Dentin by Some Restorative Materials, J. PROSTHET. DENT. 26: 307-313, 1971. BrgnnstrBm, M.: The Effect of Dentin Desiccation and Aspirated Odontoblasts on the Pulp, J. PROSTHET. DENT. 20: 165-171, 1968. Phillips, R. W.: Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry, J. PROSTHET. DENT. 23: 665-690, 1970. Measurement of the Space Between Composite Resin Bergvall, O., and BrHnnstrijm, M.: Filling Materials and the Cavity Walls, Swed. Dent. J. 64: 217-226, 1971. DR. BRXNNSTRSM: DEPT. OF ORAL HISTOPATHOLOCY, KAROLINSKA INSTITUTET, Box 3207, S-103 64 STOCKHOLM 3 SWEDEN DR. NYBORG: DEPARTMENT OF ENDODONTICS, UNIVERSITY OF UME.& SCHOOL OF DENTISTRY, S-901 87 UMEA, SWEDEN