The effect of dentin desiccation and aspirated odontoblasts on the pulp

Operative dentistry

The effect of dentin odontoblasts

desiccation

and aspirated

on the pulp

M. BriinnstrSm, Odont. Dr.* Karolinska Institutet, School of Dentistry,

Stockholm,

Sweden

1 n t h e a b sence of a water or spray coolant, tooth reduction incurs not only the risk of heat trauma but, also, of desiccation of the dentin and aspiration of odontoblasts into the dentinal tubu1es.l These effects followed an air-cooled cavity preparaheat generated durtion and the prolonged application of an air blast. l, 2 Frictional ing tooth reduction causes evaporation and expansion of the tissue fluid in dentin. These phenomena suggest a loss of tissue fluid at the surface of exposed dentin and an outward capillary flo~.~ Any strong dehydrating agent may produce the same effect.3 A dry cavity preparation lasting only a few seconds or an air blast of more than 20 seconds may induce aspiration of cells into the tubules. After making this observation, Kramer4 named the outward flow aspiration, which implies the passive drawing of cells into the tubules. Aspiration is more appropriate than migration, which implies displacement from cellular activity. Both desiccation and aspiration of odontoblasts may have clinical meaning to the dentist. Aspiration, associated with a marked reduction of these formative cells, may also cause an insult to the pulp. I>ry preparation, irrespective of r.p.m., air cooling, or prolonged air drying, is an undesirable technique in dental practice. The pulpal effects of aspirated odontoblasts and of desiccation of dentin have occupied the attention of few investigators. Langelandl exposed the dentin of 20 teeth for a period of time or inserted a sugar solution, spongostan, or saline in the cavities and then restored the teeth with amalgam. He observed cell nuclei in the tubules under the cavities and inflarnmation in the pulp. He concluded that the degeneration of the cells in the tubules caused the pulpitis. BrannstrGm5 prepared cavities in 29 contralateral pairs of teeth. One tooth of each pair constituted the control; the other was dried with forced air for 5 minutes, All teeth were restored with amalgam. The inflammatory responses were the same in test and control teeth. Cotton’ exposed 16 experimental cavities to forced air for 30 seconds. An equal number of controls received the same treatment without the forced air. All teeth *Department

of Oral Histopathology. 165

166

J. PIOS. Dent. August, 1968

Briinnstri;tn

were restored with amalgam. Inflammation was found in the pulp more often iI1 cavities exposed to the forced air, and this suggested a relationship between aspirated odontoblastic nuclei and inflammation. Hamilton and Kramrr7 prepared 7 1 cavitk under a water spray: Xi wercx then dehydrated with an intermittent air blast ~OI 7 to 10 minutes. The cavity \vas lincti \jith noncoheskr gold foil and fillrd with Pulprotex. Specimens taken after 1 to 30 days showt:tl a11 inflammatory rcsponsc in 21 per cent of those teeth prepared with a water coolant and in 30 to 40 per ccllt of those exposed to the air blast. The object of this study was to seek answers to the following: i 1) How rapidly after the application of an air blast do aspirated odontoblasts disappear from the dentinal tubules, (2 i does the degeneration of aspirated cells in the tubules produce inflammation, and (:3! how does the aspiration of cells alrect the adjacent pulp and predentin 3 METHODS

AND

MATERIALS

All preparations were rnade using a previously employed standard technique. For instance, the cavities were preparcd at about 5,000 r.p.m. with intermittently applied slight pressure under a water coolant. The cavities were 2 mm. in diameter and 2 mm. deep. Previous experience shows that this technique should cause a slight disturbance, such as disappearance of the pulpodentinal membrane and increased basophilia in the odontoblasts.’ After 1 week and 1 month, no a.ppreciablc change occurred in the pulps of the teeth.‘, !’ Class V cavities were pr’pared on 44 contralateral pairs of teeth in patients ranging from 10 to 16 years of age. Most of the teeth were sound; a few had occlusal pit amalgam restorations. When possible, the teeth were isolated with a rubber dam before the experiment began. All preparations were completed under a water coolant, dried with absorbent paper, and forced-air dried for 2 minutes. The cavities were lined with a polystyrene varnish containing calcium hydroxide and zinc oxide. Teeth to be sacrificed within 10 minutes were not restored ; the 12 pairs to be sacrificed in less than a week Iverc restored with Cavit and the remainder with amalgam. The only variable introduced in each pair of teeth was the postoperative period. Each tooth in each pair \,vas extracted at a preplanned and different time. The

Table

I. Postoperative

periods

for pairs of teeth

!

No. of

pairs

Time Tooth

No.

10 min. 6 6 24 48 1 I I

hr. hr. hr. hr. wk. wk. wk.

I

beriods Tooth 24 24 1 1 1 1 2 3

No. hr. hr. wk. wk. wk. mo. mo. mo.

2

Volume Number

20 2

Effects

of

dentin

desiccation

and

aspirated

odontoblasts

167

selection of pairs to meet the time requirement was chosen by random drawing (Table I). The specimens were formalin fixecl, decalcified in either 5 per cent nitric acid or EDTA, and processed for serial histologic sections; the sections were stained with hemalum and eosin.

RESULTS The shortest distances from the cavity to the pulp measured along the dentinal tubules ranged from 0.1 to 1.7 mm. with a mean of 0.9 mm. The pulps of all the teeth, especially those with a minimal postoperative period, showed a marked reduction of odontoblasts in the area of cut tubules (Fig. 1). The cell-rich zone was unchanged (Figs. 1 and 3). The 9 teeth extracted at the 10 minute postoperative period had numerous cell nuclei in the dentinal tubules. The maximal movement of nuclei into dentin was 0.1 mm. Only 2 of the corresponding contralateral teeth extracted at 24 hours had nuclei in the tubules. The other groups, having postoperative periods ranging from 6 hours to 1 week showed no differences between the teeth of the pairs. For instance, 2 teeth extracted after 6 hours had no nuclei in the dentin but showed a marked reduction of odontoblasts in the area of the cavity preparation; on the other hand, one of the contralateral teeth extracted after 24 hours presented more than 50 nuclei per section. In general, there were only a few aspirated nuclei in the 65 teeth extracted between 6 hours and 1 week after cavity preparation (Fig. 1). In teeth decalcified with EDTA, aspirated nuclear remnants were observed more than 1 mm. from the pulp; sometimes they were situated quite near the axial wall of the cavity (Fig. 2). Table II presents an estimate of the number of nuclei in a representative section for each of 74 teeth with postoperative periods ranging from 10 minutes to 1 week. With one exception, there were no nuclei in the tubules of specimens extracted after 1 month. A mild pulpitis occurred in only 14 teeth. The inflammatory cells consisted of leukocytes spread along the dentinopulpal wall. The number of leukocytes per sec-

Fig.

1. Dentin tubules B, The tubules

A, The

and pulp beneath a cavity occlusal to the cavity are leading to the cervical wall

which was air-dried unaffected, and the of the cavity contain

24 hours before extraction. odontoblastic layer is intact. few nuclei.

A

Fig. wall

3. .4nother section from thr tooth in Fig. and a few nuclei in the tubules. The cell-rich

tion varied from 5 to The localized pulpitis of 6 hours to 1 week I ) 2, and 3 months had Table IV describes in thickness after 24 months.

1. Thrw arc zone is fairly

a few iwkocytcs intz1c.t.

ai the d~ntinal

15: they were unrelated to filled capillaries (Figs. 1 and 3 1. occurred in about a third of the teeth extracted at periods (Table III). The pulps of teeth extracted at 10 minutes and no inflammatory cells. the changes found in the predentin. ‘I’he predentin reduced hours and increased or presented reparative dentin after 2

DISCUSSION Obviously, a 2 minute exposure to forced-air drying caused an immediate and strong aspiration of odontoblasts. However, teeth extracted either 6 or 24 hours

Volume

20

kmber

2

Table

II. Nuclei

Efects or remnants

of dentin

and postoperative Time

No. of nuclei or remnants*

10 min.

100 50 to 100 50 None

Table

made

aspirated

odontoblasts

169

periods periods

24 hr.

1

48 hr.

I wk.

Totals

1 2 4 2

1

0

-

4 7 9

1

1

13

3

11

15 9 25 25

s

9

21

5

30

7-i

in one section.

periods

periods 6 24 48 1

1

and

4 2

Ill. Postoperative Time

6 hr.

9

Totals “Counts

desiccation

and leukocytes Leukocytes

present

hr. hr. hr. wk.

Leukocytes

not

present

6 15 4 26

3 6 1 4

-i-4

Table

IV. Predentin Time

periods

24 to 48 hr. 1 wk. 1 mo. 2 mo. 3 mo.

Totals

changes Reduction 5 14 3 1 -

3

Increase

or reparative

dentin

2 3 4

-G

after desiccation exhibited only a few aspirated nuclei or fragments of nuclei. This study projects that the aspirated cells underwent autolysis soon after aspiration. Also, specimens examined after 6 hours showed that the cell fragments extended more than 1 mm. into the dentin. The increased penetration suggests that the autolysis was accompanied by an outward movement of the tubular contents. If the liner and restoration had not provided a hermetic seal, there may have been an increase in hydrostatic pressure in the pulp which would have caused the outward flow. An outward flow can occur under intact enamel.3 Since cells aspirated at the time of dentin desiccation disappear from the tubules after 6 to 24 hours, the presence of cells at later intervals suggests a secondary aspiration which may result from leaky restorations and an outward flow of tissue fluid. The absence of nuclei in the tubules after 1 month suggests a reduction in the outward flow with time. It is also possible that after a few weeks the tubules became occluded or that the formation of reparative dentin caused the formation of dead

References 1.

I~aqgcland~

K.: Tissue Changes in the Dental Pulp, Odont. tidskr. 65: 239-385, 1957. M.: Dental and Pulpal Response. II. iZpplication of an Air Stream to Exposed Dentin. Short Observation Period, Acta odont. scandinav. 18: 17-28, 1960, 3. BrZnnstriim, 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. I,ivin,qstonr Ltd.. pp. ‘31-246. 4. Kramer. I. R. 11.: The Rrlationship Between Dentin Sensitivity and Movements in the Contents of thr Dentinal Tubules. Brit. D. J. 98: 391-392, 1955.

2. RriinnstrSrn.

Volumr Number 5. 6. 7. 8. 9. 10. 11. 12. 13.

14. 15. 16. 17. 18.

20 2

Effects

of

dentin

desiccation

and

aspirated

odontoblasts

171

Brannstrom, M.: Dental and Pulpal Response, III, Application of an Air Stream to Exposed Dentin. Long Observation Periods, Acta odont. scandinav. 18: 234-252, 1960. Cotton, W. R.: Pulp Response to an Air Stream Directed Into Human Cavity Preparations, 0. Surg. 24: 78, 1967. Hamilton, A. I., and Kramer, I. R. H.: Cavity Preparation With and Without Waterspray, Brit. D. J. 123: 281, 1967. Brannstrom, M., and Nyborg, H.: Dentinal and Pulpal Response. IV. Pulp Reaction to Zinc Oxyphosphate Cement, Odont. Revy 11: 37-50, 1960. Brinnstrom, M.: Reaction of the Pulp to Amalgam Fillings, Odont. Revy 14: 244-253, 1963. Lefkowitz, W.: The “Vitality” of the Calcified Dental Tissues, J. D. Res. 21: 423, 1942. Lefkowitz, W.: Further Observations of Dental Lymph in the Dentin, J. D. Res. 22: 287, 1943. Berggren, Ii.: Permeability of Enamel and Dentin, Svensk tandl. tidskr. 40: lB, 1947. Wainwright, W. W., and Belgorod, II. H.: Time Studies of the Penetration of Extracted Human Teeth by Radioactive Nicotinamide, Urea, Thiourea, and Acetamide. II. Penetration of Dentin From the Pulp Chamber, J. D. Res. 34: 28-37, 1955. Williamson, J. J.: Chemotactic Migration of Polymorphonuclear Leukocytes Along Dentinal Tubules, J. D. Res. 46: 1280, 1967 (abstr.). Ostrom, C. A.: The Trauma of Cooling in Operative Dentistry, D. Prog. 3: 138144, 1963. Gottlieb, B.: The Formation of Secondary Dentin and Related Problems, J. D. Res. 25: 29, 1946. El-Kafrawy, A. H., and Mitchell, D. F.: Pulp Reactions to Open Cavities Later Restored With Silicate Cement, J. D. Res. 42: 874-884, 1963. Robinson, H. B. G., and Lefkowitz, W.: Operative Dentistry and the Pulp, J, PROS. DENT. 12: 985-1001, 1962. Box 3207 103 64, STOCKHOLM SWEDEN

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