Human pulpal response to bleaching procedures on vital teeth

SCIENTIFIC ARTICLES

Human Pulpal Response to Bleaching Procedures on Vital Teeth Steven C. C o h e n , DDS, Chevy Chase, M d

F i f t y - o n e h u m a n t o o t h p u l p s w e r e e v a l u a t e d h i s t o l o g i c a l l y to d e t e r m i n e the effect of b l e a c h i n g p r o c e d u r e s o n vital teeth. T h e r m o s t a t i c a l l y c o n t r o l l e d h e a t a n d 35% h y d r o g e n p e r o x i d e w e r e a p p l i e d e x t e r n a l l y to p r e m o l a r s i n d i c a t e d for o r t h o d o n t i c extraction. T h e t r e a t m e n t c o n s i s t e d of t h r e e visits of 30 m i n u t e s ' d u r a t i o n each. T h e t e e t h w e r e t h e n e x t r a c t e d a f t e r p o s t o p e r a t i v e intervals of a n hour, t h r e e days, 15 days, a n d 30 days. H i s t o l o g i c o b s e r v a t i o n s of the e x p e r i m e n t a l g r o u p s w e r e c o n s i s t e n t with t h o s e of the c o n t r o l group. U n d e r the c o n d i t i o n s of this s t u d y , the b l e a c h i n g o f vital teeth m a y be c o n s i d e r e d h a r m l e s s to p u l p a l tissue.

Bleaching of nonvital teeth with the use of chemicals and heat is an acceptable and successful clinical procedure. ~~ However, because intact dentin and enamel are porous tissues, "~'~bleaching procedures have also been applied to vital teeth with intrinsic staining. Because previous evaluation of this procedure has been limited to studying the reduction of stains or the elimination of the patient's discomfort, evidence of its effect on intact pulpal tissue is lacking. Previous studies on the bleaching of vital teeth have reported the use of the Bleaching Tool,* with 30% hydrogen peroxide, ~ a solid-state heating device," the Bleaching Tool with a rheostatf a rheostat-controlled bleaching instrument, 8 and a wood burner tool plus 30% hydrogen peroxide" to bleach vital teeth. Results of these clinical studies show significant reduction of stains with no lasting discomfort to the patient. The application of heat to vital pulps has been questioned by some

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investigators. Nyborg and Brannstrom 1~ have shown that heat m a y cause pulpal death. They found that, the stronger the heat source and the lesser the distance between it and the pulp, the greater the chance of pulpal death. Therefore, a thorough evaluation of the effect of accepted bleaching procedures on pulpal tissues is justified. The aim of this study was to determine if any histopathologic changes occur after vital teeth are treated with use of thermostatically controlled heat and Superoxol]" and to determine whether these changes are transitory or permanent. MATERIALS AND METHODS The study consisted of three parts: part one, evaluation of the temperature scale on the bleaching instrument; part two, treatment of vital premolars with heat and Superoxol; and part three, microscopic examination of the pulpal tissue within the experimental and control teeth.

Part 1 The Union Broach Bleaching Instrument,~ a rheostat-controlled heating device, was used. A temperature probew lubricated with silicone was used to ascertain the accuracy of the temperature scale. The time necessary to reach an equilibrium temperature was determined by choosing several arbitrary points on the scale and recording the temperature at each point. All readings were made at a constant room temperature of 71 F. Because the original heating tip was too large for use on the teeth chosen for the study, a smaller, recontoured tip was made. The preceding experimental series was repeated to ensure that the heat source would be the same.

Part 2 Fifty-one intact, cariesfree premolars were treated using a standardized procedure. ~'~ Eight adolescent girls, ten adolescent boys, and one

JOURNAL OF ENDODONTICS I VOL 5, NO 5, MAY 1979

man, a total of 19 patients, participated in the study. V i t a l i t y tests using the electric p u l p tester]] a n d ice were done on each tooth at the beginning of the p r o c e d u r e a n d j u s t before extraction. T h e e x p e r i m e n t a l teeth were isolated with a r u b b e r d a m a n d were ligated with d e n t a l floss. T h e adjacent tissues were p r o t e c t e d with p e t r o l e u m jelly. P r o p h y l a x i s was done, a n d the teeth were rinsed with warm w a t e r a n d alcohol, a n d then were dried. Small cotton pledgets saturated with Superoxol were placed over the l a b i a l a n d lingual surfaces of each e x p e r i m e n t a l tooth. At the first a p p o i n t m e n t , the teeth were subjected to increasing temperatures until the p a t i e n t responded. The t e m p e r a t u r e control was then set on the next lowest setting a n d used t h r o u g h o u t the t r e a t m e n t . Total t r e a t m e n t time was 30 minutes per tooth (15 m i n u t e s per surface).

After t r e a t m e n t , the teeth were washed with w a r m w a t e r a n d dried. T h e p a t i e n t s were advised to avoid cold foods a n d liquids for a p p r o x i m a t e l y 24 hours. This p r o c e d u r e was r e p e a t e d on two other occasions, at one-week intervals. O n e tooth from each of the 19 patients served as a control. T h e t r e a t e d teeth were e x t r a c t e d with forceps after an hour, three days, 15 days, a n d 30 days, while the p a t i e n t was u n d e r local anesthesia consisting of 2% lidocaine with e p i n e p h r i n e at a c o n c e n t r a t i o n of 1 : 100,000. I m m e d i a t e l y after extraction, each tooth was severed with a wire cutter, a n d the coronal two thirds were placed in a solution of 10% neu-tral buffered f o r m a l i n for at least 48 hours. 11 T h e teeth were decalcified in a m i x t u r e of 5% formic a c i d - s o d i u m citrate, a n d were split l o n g i t u d i n a l l y ; six m i c r o n sections were stained with h e m a t o x y l i n a n d

eosin for h i s t o p a t h o l o g i c e x a m i n a tion. Part 3 T h e slides were e x a m i n e d by two m e m b e r s of the d e p a r t m e n t of oral p a t h o l o g y , B a l t i m o r e College of D e n t a l Surgery, a n d b y the author. T h r e e m e t h o d s were used. First, the slides were observed at r a n d o m , with no knowledge of which teeth were e x p e r i m e n t a l or control, or to which time period the teeth belonge.d. Second, the slides were g r o u p e d according to p o s t o p e r a t i v e time intervals a n d c o m p a r e d with the control group. T h i r d , each experim e n t a l tooth was c o m p a r e d with the control tooth from the same individual. T h e histologic e x a m i n a t i o n inc l u d e d observation of the following: the shape of cells, presence a n d location of nuclei, a n d variations in the o d o n t o b l a s t i c layer; the presence or

Table 1 9 Data concerning patients in bleaching experiment.

Age

Sex

Number of teeth treated

14 14 12 14 15 11 13 13 13 24 13 12 9 12 14 12 13 13 14

M F M M F F M F F M M M F M M F F M M

3 3 3 3 3 3 3 3 3 I 3 3 3 3 3 3 3 1 1

Bleaching temperature (F)

Postoperative interval

Posttreatment response of patient*

129 129 123 129 115 126 123 126 135 129 135 132 129 132 126 129 129 132 135

30 days 30 days 30 days 30 days 30 days 15 days 15 days 15 days 15 days 3 days 3 days 3 days 3 days 3 days 1 hr 1 hr 1 hr 1 hr I hr

1 1 1 l 2 1 0 0 0 1 1 0 1 1 1 1 0 1 1

*0 = no t h e r m a l sensitivity; I = scns~tlv|ty to cold and intermittent spontaneous pare at 2 i hours or less. 2 = senqltlvlt~, to cold a n d m t e H n l t t e n t s p o n t a n e o u s pain at ~,8 hours or less,

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JOURNAL OF ENDODONTICS I VOL 5, NO 5, MAY 1979

Table 2 * Distribution of teeth with respect to posttreatment responses.

Total number of patients

Number of patients with no symptoms

Number of patients with symptoms up to 24 hours

Number of patients with symptoms up to 48 hours

19

4 (22%)

14 (73%)

1 (5%)

Table 3 * Histologic comparisons between control and experimental teeth.

Odontoblastic layer Control Intact Aspiration of nuclei Total number of teeth

At one hour

At three days

At 15 days

At 30 days

13 6 (32%)

7 4 (36%)

10 3 (23%)

8 4 (33%)

7 8 (53%)

19

11

13

12

15

absence of a distinct Weil's cell-free zone; the presence of any inflammatory cells in the cell-rich layer and in the central part of the pulp; and the presence of extravascular erythrocytes and condition of blood vessels in the central part of the pulp.

treatment response to ice was normal in all groups, except for the group whose teeth were extracted an hour after treatment; all treated teeth in these patients were abnormally sensitive to cold.

prescribed. Four patients (22%) reported no posttreatment pain (Table 2). All experimental teeth remained vital to the electric pulp tester throughout the treatment. T h e post-

RESULTS Part 1

,.

O n evaluation, the temperature scale on the bleaching instrument proved to be inaccurate, necessitating establishment of a new temperature scale. In addition, 15 minutes were required to reach an equilibrium temperature from one point to another. The recontoured heating tip was determined to be as accurate as the original.

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Part 2

Clinically, all treated teeth became lighter in color, which was evident for as long as 30 days after treatment. The treatment temperatures ranged from 115 F to 135 F, with 129 F as the average temperature (Table 1). During treatment, m a n y of the patients reported sensitivity to cold and intermittent spontaneous pain. S y m p t o m s lasted for 24 hours or less in 14 patients (73%). O n e patient (5%) reported symptoms that lasted for 48 hours; a mild analgesic was

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Fig 1--Photomicrographs of normal pulp tissue from tooth extracted at 30 days. Top." congested vessels resulting from mjury with forceps (orig mag X 10). Bottom." note distinct cell layers (orig mag • 50).

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JOURNAL OF ENDODONTICS ] VOL 5, NO 5, MAY 1979

DISCUSSION

Fig 2--Photomzcrograph of tooth extracted hour after treatment shows aspzration of odontoblasOc nuclei mto dentmal tubules at level of cementoenameljunctzon (ong mag X 50). "

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Part 3 The general histologic picture was consistent in all teeth and conformed to that accepted as normal pulpal tissue"-' (Fig 1). The control group consisted of 19 teeth, one from each patient. Thirteen teeth had an intact odontoblastic layer, whereas six teeth showed aspiration of odontoblastic nuclei into the dentinal tubules at the level of the cementoenamel junction (CEJ). In all cases, the cell-free zone was present, inflammatory cells were not observed in the remaining tissue layers, and a moderate amount of vasodilation and congestion was seen in the central portion of the pulp (Table 3). Of the 11 teeth that had been extracted an hour after treatment, seven teeth had an intact odontoblastic layer, whereas four teeth showed aspiration of odontoblastic nuclei into the dentinal tubules at the level of the CEJ (Fig 2). All remaining tissue layers were consistent with the control group. In the group of teeth extracted three days after treatment (13 teeth), ten teeth had an intact odontoblastic layer, whereas three teeth showed

,D

aspiration of odontoblastic nuclei into the dentinal tubules at the level of the CEJ. All remaining tissue layers were consistent with the control group. O f the 12 teeth extracted at 15 days, eight teeth were observed with an intact odontoblastic layer, whereas four teeth showed aspiration of odontoblastic nuclei into the dentinal tubules. All remaining tissue layers were consistent with the control group. O f the 15 teeth extracted at 30 days, seven teeth had an intact odontoblastic layer, and eight teeth were observed with aspiration of odontoblastic nuclei into the dentinal tubules. All remaining tissue layers were consistent with the control group.

Statistical Analysis The chi-square test of significance was done to evaluate statistical differences between the control and experimental groups in the aspiration of odontobtastic nuclei. It was determined that X" = 2~98 with d f = 4; therefore, the differences were not statistically significant.

Preliminary investigations have suggested that controlled heat and 35% hydrogen peroxide are effective in removing intrinsic stains in vital teeth? ~' However, no histologic studies have been reported that examine the possible permanent damage to vital teeth that are treated in this manner. This was the aim of this study. In preparing the material "for histologic observation, longitudinal sections were used so that, in reporting the status of the pulp, a representative area of the entire tooth would be observed. The results shown in Table 3 indicate that there were no gross differences between the control and experimental groups. Aspiration of odontoblastic nuclei into the dentinal tubules can occur with an increase in intrapulpal pressure?' This may be due to inflammation or injury with forceps during extraction2 ~ Because there was no inflammation associated with the aspiration of odontoblastic nuclei, this finding can be attributed to injury with forceps during extraction. Weil's cell-free zone was intact, and no inflammatory cells appeared in the cell-rich layer or in the central portion of the pulp in any of the experimental teeth. All teeth that were extracted with the patient under local anesthesia showed a moderate amount of vasodilation and congestion. Because previous investigators have shown that there are no differences between teeth extracted with use of local and general anesthesia, '4~6 the vasodilation and congestion observed in this study can be attributed to trauma during extraction? ~ Finally, if no histopathologic

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JOURNAL OF ENDODONTICS I VOL 5, NO 5, MAY 1979

c h a n g e s were o b s e r v e d , w h y d i d 15 (78%) o f the 19 p a t i e n t s h a v e p a i n ? D i s c o m f o r t e x p e r i e n c e d by these p a t i e n t s m a y h a v e b e e n d u e to an increase in i n t r a p u l p a l pressure c a u s e d b y the a p p l i c a t i o n o f h e a t ? ~ ,s W h e n the i n t r a p u l p a l pressure ret u r n e d to n o r m a l , t h e s y m p t o m s subsidedY ~

SUMMARY A N D CONCLUSIONS T h e p u r p o s e of this s t u d y was to d e t e r m i n e if a n y h i s t o p a t h o l o g i c c h a n g e s o c c u r after v i t a l t e e t h are s u b j e c t e d to c l i n i c a l l y a c c e p t a b l e b l e a c h i n g procedures. F i f t y - o n e prem o l a r s p l a n n e d for o r t h o d o n t i c ext r a c t i o n w e r e t r e a t e d for 30 m i n u t e s e a c h o n t h r e e s e p a r a t e occasions, a n d e x t r a c t e d at i n t e r v a l s o f a n h o u r , t h r e e days, 15 days, a n d 30 days. Histologic examination showed t h a t t h e p u l p a l c o n d i t i o n o f the e x p e r i m e n t a l g r o u p was consistent w i t h t h e p u l p a l c o n d i t i o n of the control group. The odontoblastic l a y e r was i n t a c t e x c e p t for areas l o c a t e d at the C E J in a p p r o x i m a t e l y 36% of t h e t e e t h o b s e r v e d . I n these areas, t h e r e was a s p i r a t i o n of o d o n t o blastic n u c l e i i n t o t h e d e n t i n a l tubules. It c a n be c o n c l u d e d t h a t u n d e r the c o n d i t i o n s of this s t u d y , t h e treatm e n t of v i t a l t e e t h w i t h h e a t a n d 35% h y d r o g e n p e r o x i d e m a y be c o n s i d e r e d h a r m l e s s to p u l p a l tissue.

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*Fluoroted Co., Davis, Calif. ~35% Hydrogen Peroxide, Union Broach Co., Long Island, NY. ~Union Broach Bleaching Instrument, Union Broach Co., Long Island, NY. w Multimeter with Temperature Probe, Model DM501, Tektronix, Inc., Beaverton, Ore. ]lPelton & Crane, Charlotte, NC. This paper was submitted in partial fulfillment of the reqmrements for certification in endodontics at the Baltimore College of Dental Surgery, Dental School, University of Maryland at Baltimore. The author thanks Drs. Stanley Andrews, David August, James Gutmann, and Stanley Klein, department of endodonties, for their suggestions and assistance; Drs. Martin Lunin and Todd Beckerman, department of oral pathology, for their assistance in histologic examination: and Dr. Van Thompson, department of basic dental science, for his assistance in calibration of the bleaching tool. Dr. Cohen is in private practice limited to endodontics, Chevy Chase, Md, and is assistant clinical professor of endodontics, Baltimore College of Dental Surgery, Dental School, University of Maryland at Baltimore. Requests for reprints should be directed to Dr. Cohen, 5454 Wisconsin Ave, Suite 1355, Chevy Chase, Md 20015. References 1. Ingle, J. Endodontics. Philadelphia, Lea & Febiger, 1965, p 607. 2. Grossman, L. Endodontic practice, ed 6. Philadelphia, Lea & Febiger, 1965, p 440. 3. Bevlander, G., and Amler, M.H. Radioactive phosphate absorption by dentin and enamel. J Dent Res 24(1):45-51, 1945. 4. Wainwright, W., and Lemoine, F.A. Rapid diffuse penetration of intact enamel and dentin by carbon~Mabeled urea. JADA 41(2):135-145, 1950. 5. Cald~ell, C.B. Bleaching vital or nonvi-

tal teeth. J Calif Dent Assoc 42(3):234-235, 1966. 6. Hodosh, M.; Mirman, M.; Shklar, G.; and Povar, M. A new method of bleaching discolored teeth by the use of a solid state direct heating device. Dent Dig 76:344-346, 1970. 7. Cohen, S., and Parkms, F. Bleaching tetracycline-stained vital teeth. Oral Surg 29(3)'465-471, 1970. 8. Arens, D.; Rich, J.; and Healy, H. A practical method of bleaching tetracyclinestamed teeth. Oral Surg 34(5):812-817, 1972. 9. Corcoran,J., and Zillich, R. Bleaching of vital tetracycline-stained teeth. J Mich Dent Assoc 56(12):340-343, 1974. 10. Nyborg, H., and Brannstrom, M. Pulp reaction to heat. J Prosthet Dent 19:605-612, 1968. 11. Stanley, H.R., and Weaver, K. A technique for the preparation of human pulpal tissues. In: Biology of the dental pulp organ, a symposium. Finn, S.B. (ed.). Birmingham, University of Alabama Press, 1968, p 1. 12. Provenza, DJ. Oral histology. Philadelphia, J. B. Lippincott Co, 1964, pp 259-278. 13. Stanley, H., and Swerdlow, H. Aspiration of cells into dentina] tubules? Oral Surg 11(9):1007-1017, 1958. 14. Langeland, K. Tissue changes in the dental pulp. Odontol Tids 65:239, 1957. 15. Provenza, V. Comparative morphology of the pulp vascular system In: Biology of the dental pulp organ, a symposium. Finn, S.B. (ed.) Birmingham, University of Alabama Press, 1968, p 353. 16. Langeland, K. Effects of local anesthetics on pulp tissue. Dent Prog 3:13-18, 1962. 17. Beveridge, E.E., and Brown, A.C. Measurement of human dental intrapulpal pressure and its response to clinical variables. Oral Surg 19(5):655-668, 1965. 18. Van Hassel, HJ., and Brown, A.C. Effect of temperature changes on intrapulpal pressure and hydraulic permeabihty in dogs. Arch Oral Biol 14:301-315, 1969. 19. Andrews, S.S. The correlation between intrapulpal pressure and sensory response in pulpal pathosis. Master's thesis, University of Washington, Seattle, 1971, p 49.