JOURNAL OF ENDODONTICS I VOL 4, NO 5, MAY 1978
Vital Pulp Tissue Response to Sodium Hypochlorite
Edward F. Rosenfeld, DMD, MS; Garth A. James, DDS, MS; and Buckner S. Burch, DDS, MS, Lincoln, N e b
I n s t r u m e n t e d a n d n o n i n s t r u m e n t e d teeth in o r t h o d o n t i c patients w e r e irrigated with Clorox* or p h y s i o l o g i c saline s o l u t i o n a n d e v a l u a t e d histologically. T h e findings a d d e d to a n d s u p p o r t e d p r e v i o u s l y p u b l i s h e d data that C l o r o x exerts a nonspecific, n o n c o a g u l a t i n g digestive effect o n vital, y o u n g , h e a l t h y h u m a n p u l p tissue a n d t h a t the solvent effect was r e s t r i c t e d b y the size of the l u m e n .
Sodium hypochlorite (NaOC1) has been widely recommended as an irrigant to aid in the chemomechanical debridement of root canals because of its reported action as a solvent for exudate, necrotic tissue, and other organic debris and its ability to act as a mild antiseptic. 1-4 The 5.25% NaOC1 solution has been shown to be significantly more effective than weaker dilutions in its ability to digest necrotic tissue? The solvent effect of this chemical assumes greater importance when one considers the complex nature of the root canal system. 6 Except for an unsupported statement in a recent study that a 5% solution of NaOC1 nonselectively dissolves vital as well as necrotic tissue, 7 the bulk of the dental literature has focused its attention on the solvent effect of NaOC1 on necrotic
140
tissue with no mention of its effect on vital tissue left within the root canal. 8-11 These studies used gross examination, the light microscope, and the scanning electron microscope to show that NaOG1 of various strengths may have either no effect or a moderate ability to dissolve devitalized pulp tissue. This solvent effect was limited by cul-de-sacs and proximity to the apex. Only two studies examined the solvent effect of NaOC1 on vital pulp tissue, and these were within instrumented teeth. Grey '2 instrumented 33 vital teeth with saline solution or NaOC1 for one hour or two 45minute sessions. Examination by the light microscope disclosed little or no debridement of the vital pulp tissue within the main canal or accessory canals. The author concluded that
the vascularity of the vital tissue resisted the action of NaOC1. McComb and others '3 used the scanning electron microscope in a similar study and arrived at essentially the same conclusions. Fifteen milliliters of a 1% and 2.5% NaOC1 solution was less effective than a neutralized EDTA solution and was ineffective in narrow and curved canals. To our knowledge, no study has examined the effect of NaOC1 on pulp tissue alone without the mechanical effect of instrumentation. The purpose of this study was to evaluate the solvent action of 5.25% NaOC1 on vital human pulp tissue that had not been disturbed by instrumentation. Also evaluated was its effect on the canal walls, residual tissue, accessory canals, and the apical pulp stump of instrumented teeth.
JOURNAL OF ENDODONTICS ] VOL 4, NO 5, MAY 1978
MATERIALS AND METHODS Forty-two vital, virgin premolars were obtained from young adult orthodontic patients. An informed consent was obtained from each patient after the nature of the procedure and possible discomfort and risk had been fully explained. The medical history was reviewed for each patient; all the teeth to be treated were pulp tested by thermal and electrical methods and radiographs were examined for any sign of pathologic conditions. If there were any abnormal findings, the teeth were eliminated from the study. Two teeth served as controls for the operative and histologic methods. The remaining 40 teeth were arbitrarily placed into two groups of 20 teeth each. The first group, A, was used to determine the solvent action of a 5.25% NaOC1 solution on the uninstrumented vital coronal pulp tissue. Teeth in group B were instrumented while irrigating with NaOC1 to determine its effect on the canal walls, residual tissue, accessory canals, and the apical pulp stump. In each group, ten teeth served as controls with application of saline mlution. Each tooth selected for treatment was anesthetized with lidocaine, which contained a vasoconstrictor. The rubber dam was applied, and access to the pulp chamber was obtained with a high-speed straight cut fissure bur under a water spray. A similar method has been shown to produce minimal trauma to the pulp." A dentin shelf was created to aerve as a reference point to indicate the original level of the cut pulpal SUrface. After preparation for access, teeth in group A were irrigated intermit-
tently for 15 minutes with 5 ml of either full-strength (5.25%) Clorox or physiologic saline solution. The solutions were directed onto the pulp tissue from the needle of the irrigation syringe while using light plunger pressure. Excess solution was absorbed onto a cotton pellet, with care taken not to touch the pulp. A small, dry pledget of cotton was placed in the chamber and Cavity" was used to seal the tooth until it was extracted. Group B teeth were instrumented with K-type files to a size 40 in maxillary teeth and a size 60 in mandibular teeth to a depth of approximately 5 mm from the apex. An attempt was made to sever the pulp at this level and to create a ledge to serve as a reference point. Instrumentation and intermittent irrigation with 5 ml of either fullstrength Clorox or physiologic saline solution were performed for a total of 15 minutes. Light plunger pressure was again used. At the end of the period, the teeth were sealed as described previously. All extractions were performed by undergraduate dental students within 45 minutes after completion of the irrigating procedures. Immediately after extraction, the Cavit and cotton were removed and the teeth were placed in 10% neutral-buffered Formalin under vacuum for 24 hours. After decalcification in Cal-Ex~ solution and routine processing, the specimens were embedded in paraffin, sectioned at 6 to 7/z, stained with either hematoxylin and eosin or Masson's trichrome connective tissue stain, and examined with a light microscope. Two examiners independently examined the specimens without knowing which irrigant was used.
Both examiners evaluated the microscopic sections on the basis of the following criteria: the pulpal level in millimeters below the cut surface; the presence or absence of residual tissue on canal walls and the effect of the solutions on this tissue; the presence or absence of an apical plug of dentin, pulpal debris, predentin, a surface coagulum, surface tissue compression or hemorrhage; and any change in erythrocyte, odontoblast, and dentin morphology or alteration of the collagen, cells, and ground substance in deeper pulpal levels.
RESULTS Control Teeth The tooth that was extracted intact did not show any adverse pulpal changes as a result of the processing technique. The tooth in which access was obtained, but in which no solutions were applied, demonstrated a concavity at the pulpal surface with the adherent remains of a blood clot (Fig 1, left). A slight amount of surface tissue compression was noticed with some slight damage to the immediate subsurface pulp from the operative procedure. Noninstrumented (Group A)
Teeth
The presence of a surface concavity in the control specimen was also seen in teeth irrigated with saline solution. In addition, a compression band was present in almost all samples (Fig 1, right), and it appeared to be more distinct and wider than that seen in the control specimen (Fig 1, left). A slight amount of surface hemorrhage was seen with no alteration in the morphology of the red cells or the 141
IOURNAL OF ENDODONTICS I VOL 4, NO 5, MAY 1978
Fig 1--Left, control specimen. Routine access established and allowed to bleedfor 15 minutes (H&E, orig mag • 37). Right, saline specimen, noninstrumented (H&E, orig mag X 37).
Fig 2--Noninstrumented saline specimen showing pulp surface (H&E, orig mag X578).
cells in the subsurface layers (Fig 2). The mean level of the pulp below the cut surface was 0.5 ram. When NaOC1 was used as an irrigant, it seemed to have a digestive effect on vital pulp tissue within the noninstrumented teeth (Fig 3, left). 142
This action was limited by access and diameter of the canal. In teeth with small canals, the pulpal level was generally higher than those specimens with wider canals. The solvent and tissue-necrotizing activity was nonspecific and noncoagulating. So-
dium hypochlorite acted only at the surface with miminal effects on deeper pulpal tissue (Fig 3, right). Immediately below the surface, there was some loss of staining characteristics but only to a level of approximately three to five cells deep (Fig 4). Hemorrhage was greater than in the saline control sections and the surface vessels responsible for the hemorrhage were observed (Fig 4). Predentin was absent in almost all instances and, where it remained, it persisted as small patches. The destruction of predentin was the most consistent finding. The predentin appeared to be labile to the action of NaOC1 (Fig 5). The NaOC1 solution had dissolved the predentin lining that exposed the underlying irregular surface of the calcified dentin. The calcified dentin did not appear to have been significantly altered. Although the pulpal surface was concave, there was no evidence of any surface compression except in two specimens. Pulpal levels varied from 0.5 to 3.0 m m below the cut surface, with a mean level of 1.7 mm. This finding is statistically significant at the 95% probability level when compared to saline-treated teeth. The Kalmogorov-Smirnov two-sample test was used. 15 The nuclei of the odontoblasts in the immediate subsurface area were paler stained, the chromatin appeared clumped and more granular, and the cytoplasm stained less distinct. Collagen fibers just below the surface were slightly paler stained; however, the fibers at the surface of the pulp were basophilir and hyalinized (Fig 4). Masson's trichrome stain did not disclose any more information than the slides that were stained with hematoxylin and eosin. The fibroblasts appeared
Fig 3-Left, noninstrumented Clorox specimen. Note pulpal level well below cut surface (H&E, orig mag • 16). Right, noninstrumented Clorox specimen (H&E, orig mag • 88).
Fig 4-Noninstrumented Clorox specimen showing bleeding vessel at pulpal surface (H&E, orig mag X578).
to be smudged and the nuclei and cytoplasm pale and indistinct. In some cases, the nuclei of the fibroblasts were hyperchromatic and dispersed (Fig 4). The affected red blood cells were pale and basophilic with an indistinct cell membrane. Some appeared brownish and some appeared crenated, while others, presumably from fresh hemorrhage, appeared normal. Changes in the erythrocytes were also observed in deeper vessels. All changev in the remainder of the pulp were limited to the immediate subsurface.
Instrumented Teeth (Group B) Instrumentation with saline solution did not remove all of the predentin in any of the ten specimens and, in most cases, some residual tissue remained along canal walls and in accessory canals (Fig 6; 7, left). There was no extensive hemorrhage in any specimen. Four sections showed changes in the red blood cells. A plug of dentin filings was present in most specimens above the twisted, corn-
Fig 6--1nstrumented sahne specimen. Hemorrhage and tissue are present at orifice of lateral canal (H&E, orzg mag X 228).
Fig 5-Noninstrumented Clorox specimen showing progressive digestion of predentin. Note undisturbed irregular surface of the calcified dentin (H&E, orig mag X 228).
143
Fig 7--Left, instrumented saline specimen with residual tissue along canal wall (H&E, orig mag • 88). Right, instrumented saline specimen (H&E, orig mag • 16).
Fig 8-Left, instrumented saline specimen. Note plug of dentin filings (H&E, orig mag • 228). Right, instrumented Clorox specimen. Note absence of predentin and apical plug of dentin filings (H&E, orig mag
x16).
pressed pulp stump. This pulp tissue was too distorted to allow for the study of any cellular effects other than normal nuclear staining (Fig 7, right; 8, left). In almost all cases, instrumentation with NaOC1 removed all the predentin from areas that were both touched and untouched by the instruments (Fig 8, right). In one instance, a small amount of predentin was not removed. There was a 144
blue-staining line at the pulpal surface of four specimens (Fig 9), although none of the control teeth had this finding. There seemed to be no apparent difference in hemorrhage when compared to the controls. In almost all cases, residual tissue was removed from the walls of the root canal in teeth that were treated with NaOCI; the small piece that remained in one specimen had undergone digestive changes.
Changes in the morphology of the red blood cells were similar to the changes in group A. Fewer of the NaOCl-treated teeth than the salinetreated teeth contained an apical plug of loose dentin filings that rested on the residual pulp (Fig 8, right). In the few cases where this plug was missing, the residual tissue resembled that of group A (Fig 9). Lateral canals were affected by NaOC1 only in the region immedi-
JOURNAL OF E N D O D O N T I C S I VOL 4, NO 5, MAY 1978
Fig 9--Instrumented Clorox specimen. Note distinct line at pulpal surface (H&E, orig ,nag x578).
Measurements were made from the apical extent of instrumentation to the surface of the dentin plug or residual tissue. The mean value of 0.57 mm, compared to the mean value from the control group (0.50 ram), was not statistically significant. DISCUSSION
Fig lO--Instrumented Clorox specimen with contents of dentinal tubules removed (H&E, orig mag • 228).
ately adjacent to the main canal where some solvent action was noticed. The contents of the dentinal tubules were digested by the NaOC1 in 50% of the experimental groups and in none of the saline controls (Fig 10).
Measurements of the pulpal level indicate a strong solvent action of full-strength Clorox on the vital noninstrumented teeth. The limited solvent effect in the apical region may be attributed to the barrier of the apical plug of dentin filings, narrow lumen, and the fibrous nature of the apical pulp tissue? 8 The short time factor is probably most responsible for the absence of inflammatory cells in any of the specimens. The most consistent changes occurred in the predentin that was dissolved by the NaOC1. Orban ~7 reported that the predentin is essentially uncalcified dentin composed of bundles of Korffs' fibers (collagen),
smaller collagen fibrils, and ground substance composed of acid mucopolysaccharides. Predentin also contains nerve fibers and odontoblastic processes? 6 The loss of the predentin was not the result of instrumentation because the irregular surface of the calcified dentin had not been removed. Because these fragile areas of the calcified dentin remained, we have evidence of a solvent effect on predentin and also evidence that NaOC1 does not readily dissolve calcified tissue. The clinical significance of the effect on predentin and the contents of dentinal tubules becomes apparent when one considers previous studies showing that most bacteria are limited to the predentin and adjacent dentin of infected teeth? s It is reasonable to assume that compression of the pulpaI surface in NaOCl-treated teeth probably formed initially on application of irrigating pressure but was gradually digested by the NaOC1 during the remainder of the procedure. Because the tissue immediately below the distinct line at the surface of the NaOCl-treated teeth appeared norma!, we assumed that the solvent effect Of NaOC1 was greater than its necrotizing effect and any destroyed tissue was immediately removed. The hemorrhage was thought to be the result of progressive, indiscriminate tissue destruction by the NaOC1 with continuous exposure of deeper vessels. Of all the cells, the red blood cells seemed to be the most sensitive to the action of NaOC1. This study supports previously published works that reported the limited ability of NaOC1 to dissolve pulp tissue in confined areas. '~ However, in nonconfined areas, it is apparent that NaOC1 has a strong, 145
JOURNAL OF ENDODONTICS VOL 4, NO 5, MAY 1978
nonspecific, s u r f a c e - a c t i n g s o l v e n t a c t i o n o n vital, i n t a c t , y o u n g , p u l p tissue. In contradiction to a n o t h e r s t u d y , ~1 o u r results s h o w e d t h a t w i t h t h e e x c e p t i o n of t h e r e s t r i c t e d areas, t h e solvent a c t i o n o f N a O C 1 is g r e a t e r t h a n t h a t o f saline solution. O u r results also d o n o t a g r e e w i t h t h e results of o t h e r r e s e a r c h e r s w h o r e p o r t e d t h a t l i v i n g tissue will n o t be affected by this d r u g or t h a t a n i n t a c t c i r c u l a t i o n resists s o l v e n t action. 1~ T h e m a j o r b a r r i e r to be o v e r c o m e in t h e clinical use o f this p o p u l a r i r r i g a n t is its i n a b i l i t y to p e n e t r a t e c o n f i n e d areas. W h e n this p r o b l e m is solved it will e n h a n c e t h e success of endodontic procedures.
SUMMARY A N D CONCLUSIONS S o d i u m h y p o c h l o r i t e was c o m p a r e d to p h y s i o l o g i c saline s o l u t i o n in its a b i l i t y to dissolve v i t a l h u m a n p u l p tissue in 40 n o n i n s t r u m e n t e d and instrumented premolars. Microscopic e x a m i n a t i o n s h o w e d t h a t 5.25% N a O C 1 was m o r e effective t h a n saline s o l u t i o n a n d e x e r t e d a nonspecific, s u r f a c e - a c t i n g solvent a c t i o n on i n t a c t v i t a l p u l p tissue. T h e p r e d e n t i n a n d red b l o o d cells w e r e t h e most labile e l e m e n t s . T h e solvent effect was l i m i t e d b y a s m a l l
146
l u m e n a n d was m o s t effective in t h e m i d d l e a n d occlusal thirds. *Clorox, Clorox Co., Oakland, Calif. J'Cavit, Premier Dental Products, Philadelphia. ~Cal-Ex, Fisher Scientific Co., Fair Lawn,
nJ. Dr. Rosenfeld, former graduate student, University of Nebraska College of Dentistry, Lincoln, is currently in the practice of endodontics, Denver, Colo. Dr. James is professor and chairman of endodontics, University of Nebraska College of Dentistry, Lincoln. Dr. Burch, former associate professor of oral biology, University of Nebraska College of Dentistry, Lincoln, is currently professor of oral diagnosis and pathology at Creighton School of Dentistry, Omaha. Requests for reprints should be directed to Dr. Rosenfeld, 3525 S Tamarac Ct, Suite 240, Denver, Colo 80237.
References 1. Grossman, L. Endodontic practice, ed 7. Philadelphia, Lea & Febiger, 1970, pp 229239, 2. Luebke, R.G. Pulp cavity debridement and disinfection. Dent Clin N Am 11:603 Nov 1967. 3. Seltzer, S. Endodontology: biologic considerations in endodontic procedures. New York, McGraw-Hill, Inc., 1971, p 248. 4. Weine, F. Endodontic therapy. St. Louis, C. V. Mosby Co., 1972, pp 216-217. 5. Hand, R.E.; Smith, M.; and Harrison, J.W. Analysis of the effect of dilution on the necrotic tissue dissolution property of sodium hypochlorite. J Endod 4:60 Feb 1978. 6. Davis, S.R.; Brayton, S.M.; and Goldman, M. The morphology of the prepared root canal: a study utilizing injectable silicone. Oral Surg 34:642 Oct 1972.
7. Spangberg, L.; Engstrom, B.; and Langeland, K. Biologic effects of dental materials. 3. Toxicity and antimicrobial effect of endodontic antiseptics in vitro. Oral Surg 36:856 Dec 1973. 8. Grossman, L., and Meiman, B. Solution of pulp tissue by chemical agents. JADA 28:233 Feb 1941. 9. Gutierrez, J.H., and Garcia, J. Microscopic and macroscopic investigation on results of mechanical preparation of root canals. Oral Surg 25:108 Jan 1968. 10. Senia, E.; Marshall, F.; and Rosen, S. The solvent action of sodium hypochlorite on pulp tissue of extracted teeth. Oral Surg 31:96 Jan 1971. 11. Baker, N.A., and others. Scanning electron microscopic study of the efficacy of various irrigating solutions. J Endod 1:127 April 1975. 12. Grey, G.C. The capabilities of sodium hypochlorite to digest organic debris from root canals with emphasis on accessory canals, thesis. Boston University, 1970. 13. McComb, D.; Smith, D.C.; and Beagrie, G.S. The results of in vivo endodontie chemomechanical instrumentation-a scanning electron microscopic study. J Brit Endod Soc 9:11 Jan 1976. 14. Granath, L., and Hagman, G. Experimental pulpotomy in human bicuspids with reference to cutting technique. Acta Odontol Scand 29:155, 1971. 15. Siegel, S. Nonparametric statistics for the behavioral sciences. New York, McGraw Hill Co., 1956, pp 127-136, 278. 16. Seltzer, S., and Bender, I. The dental pulp. Biologic considerations in dental procedures. Philadelphia, J.B. Lippincott Go., 1965, pp 25, 75, 188. 17. Sicher, H. (ed.). Orban's oral histology and embryology, ed 6. St. Louis, G. V. Mosby Co., 1966, pp 118-123. 18. Bence, R., and others. A microbiologic evaluation of endodontic instrumentation in pulpless teeth. Oral Surg 35:676 May 1973.
Vital Pulp Tissue Response to Sodium Hypochlorite
Edward F. Rosenfeld, DMD, MS; Garth A. James, DDS, MS; and Buckner S. Burch, DDS, MS, Lincoln, N e b
I n s t r u m e n t e d a n d n o n i n s t r u m e n t e d teeth in o r t h o d o n t i c patients w e r e irrigated with Clorox* or p h y s i o l o g i c saline s o l u t i o n a n d e v a l u a t e d histologically. T h e findings a d d e d to a n d s u p p o r t e d p r e v i o u s l y p u b l i s h e d data that C l o r o x exerts a nonspecific, n o n c o a g u l a t i n g digestive effect o n vital, y o u n g , h e a l t h y h u m a n p u l p tissue a n d t h a t the solvent effect was r e s t r i c t e d b y the size of the l u m e n .
Sodium hypochlorite (NaOC1) has been widely recommended as an irrigant to aid in the chemomechanical debridement of root canals because of its reported action as a solvent for exudate, necrotic tissue, and other organic debris and its ability to act as a mild antiseptic. 1-4 The 5.25% NaOC1 solution has been shown to be significantly more effective than weaker dilutions in its ability to digest necrotic tissue? The solvent effect of this chemical assumes greater importance when one considers the complex nature of the root canal system. 6 Except for an unsupported statement in a recent study that a 5% solution of NaOC1 nonselectively dissolves vital as well as necrotic tissue, 7 the bulk of the dental literature has focused its attention on the solvent effect of NaOC1 on necrotic
140
tissue with no mention of its effect on vital tissue left within the root canal. 8-11 These studies used gross examination, the light microscope, and the scanning electron microscope to show that NaOG1 of various strengths may have either no effect or a moderate ability to dissolve devitalized pulp tissue. This solvent effect was limited by cul-de-sacs and proximity to the apex. Only two studies examined the solvent effect of NaOC1 on vital pulp tissue, and these were within instrumented teeth. Grey '2 instrumented 33 vital teeth with saline solution or NaOC1 for one hour or two 45minute sessions. Examination by the light microscope disclosed little or no debridement of the vital pulp tissue within the main canal or accessory canals. The author concluded that
the vascularity of the vital tissue resisted the action of NaOC1. McComb and others '3 used the scanning electron microscope in a similar study and arrived at essentially the same conclusions. Fifteen milliliters of a 1% and 2.5% NaOC1 solution was less effective than a neutralized EDTA solution and was ineffective in narrow and curved canals. To our knowledge, no study has examined the effect of NaOC1 on pulp tissue alone without the mechanical effect of instrumentation. The purpose of this study was to evaluate the solvent action of 5.25% NaOC1 on vital human pulp tissue that had not been disturbed by instrumentation. Also evaluated was its effect on the canal walls, residual tissue, accessory canals, and the apical pulp stump of instrumented teeth.
JOURNAL OF ENDODONTICS ] VOL 4, NO 5, MAY 1978
MATERIALS AND METHODS Forty-two vital, virgin premolars were obtained from young adult orthodontic patients. An informed consent was obtained from each patient after the nature of the procedure and possible discomfort and risk had been fully explained. The medical history was reviewed for each patient; all the teeth to be treated were pulp tested by thermal and electrical methods and radiographs were examined for any sign of pathologic conditions. If there were any abnormal findings, the teeth were eliminated from the study. Two teeth served as controls for the operative and histologic methods. The remaining 40 teeth were arbitrarily placed into two groups of 20 teeth each. The first group, A, was used to determine the solvent action of a 5.25% NaOC1 solution on the uninstrumented vital coronal pulp tissue. Teeth in group B were instrumented while irrigating with NaOC1 to determine its effect on the canal walls, residual tissue, accessory canals, and the apical pulp stump. In each group, ten teeth served as controls with application of saline mlution. Each tooth selected for treatment was anesthetized with lidocaine, which contained a vasoconstrictor. The rubber dam was applied, and access to the pulp chamber was obtained with a high-speed straight cut fissure bur under a water spray. A similar method has been shown to produce minimal trauma to the pulp." A dentin shelf was created to aerve as a reference point to indicate the original level of the cut pulpal SUrface. After preparation for access, teeth in group A were irrigated intermit-
tently for 15 minutes with 5 ml of either full-strength (5.25%) Clorox or physiologic saline solution. The solutions were directed onto the pulp tissue from the needle of the irrigation syringe while using light plunger pressure. Excess solution was absorbed onto a cotton pellet, with care taken not to touch the pulp. A small, dry pledget of cotton was placed in the chamber and Cavity" was used to seal the tooth until it was extracted. Group B teeth were instrumented with K-type files to a size 40 in maxillary teeth and a size 60 in mandibular teeth to a depth of approximately 5 mm from the apex. An attempt was made to sever the pulp at this level and to create a ledge to serve as a reference point. Instrumentation and intermittent irrigation with 5 ml of either fullstrength Clorox or physiologic saline solution were performed for a total of 15 minutes. Light plunger pressure was again used. At the end of the period, the teeth were sealed as described previously. All extractions were performed by undergraduate dental students within 45 minutes after completion of the irrigating procedures. Immediately after extraction, the Cavit and cotton were removed and the teeth were placed in 10% neutral-buffered Formalin under vacuum for 24 hours. After decalcification in Cal-Ex~ solution and routine processing, the specimens were embedded in paraffin, sectioned at 6 to 7/z, stained with either hematoxylin and eosin or Masson's trichrome connective tissue stain, and examined with a light microscope. Two examiners independently examined the specimens without knowing which irrigant was used.
Both examiners evaluated the microscopic sections on the basis of the following criteria: the pulpal level in millimeters below the cut surface; the presence or absence of residual tissue on canal walls and the effect of the solutions on this tissue; the presence or absence of an apical plug of dentin, pulpal debris, predentin, a surface coagulum, surface tissue compression or hemorrhage; and any change in erythrocyte, odontoblast, and dentin morphology or alteration of the collagen, cells, and ground substance in deeper pulpal levels.
RESULTS Control Teeth The tooth that was extracted intact did not show any adverse pulpal changes as a result of the processing technique. The tooth in which access was obtained, but in which no solutions were applied, demonstrated a concavity at the pulpal surface with the adherent remains of a blood clot (Fig 1, left). A slight amount of surface tissue compression was noticed with some slight damage to the immediate subsurface pulp from the operative procedure. Noninstrumented (Group A)
Teeth
The presence of a surface concavity in the control specimen was also seen in teeth irrigated with saline solution. In addition, a compression band was present in almost all samples (Fig 1, right), and it appeared to be more distinct and wider than that seen in the control specimen (Fig 1, left). A slight amount of surface hemorrhage was seen with no alteration in the morphology of the red cells or the 141
IOURNAL OF ENDODONTICS I VOL 4, NO 5, MAY 1978
Fig 1--Left, control specimen. Routine access established and allowed to bleedfor 15 minutes (H&E, orig mag • 37). Right, saline specimen, noninstrumented (H&E, orig mag X 37).
Fig 2--Noninstrumented saline specimen showing pulp surface (H&E, orig mag X578).
cells in the subsurface layers (Fig 2). The mean level of the pulp below the cut surface was 0.5 ram. When NaOC1 was used as an irrigant, it seemed to have a digestive effect on vital pulp tissue within the noninstrumented teeth (Fig 3, left). 142
This action was limited by access and diameter of the canal. In teeth with small canals, the pulpal level was generally higher than those specimens with wider canals. The solvent and tissue-necrotizing activity was nonspecific and noncoagulating. So-
dium hypochlorite acted only at the surface with miminal effects on deeper pulpal tissue (Fig 3, right). Immediately below the surface, there was some loss of staining characteristics but only to a level of approximately three to five cells deep (Fig 4). Hemorrhage was greater than in the saline control sections and the surface vessels responsible for the hemorrhage were observed (Fig 4). Predentin was absent in almost all instances and, where it remained, it persisted as small patches. The destruction of predentin was the most consistent finding. The predentin appeared to be labile to the action of NaOC1 (Fig 5). The NaOC1 solution had dissolved the predentin lining that exposed the underlying irregular surface of the calcified dentin. The calcified dentin did not appear to have been significantly altered. Although the pulpal surface was concave, there was no evidence of any surface compression except in two specimens. Pulpal levels varied from 0.5 to 3.0 m m below the cut surface, with a mean level of 1.7 mm. This finding is statistically significant at the 95% probability level when compared to saline-treated teeth. The Kalmogorov-Smirnov two-sample test was used. 15 The nuclei of the odontoblasts in the immediate subsurface area were paler stained, the chromatin appeared clumped and more granular, and the cytoplasm stained less distinct. Collagen fibers just below the surface were slightly paler stained; however, the fibers at the surface of the pulp were basophilir and hyalinized (Fig 4). Masson's trichrome stain did not disclose any more information than the slides that were stained with hematoxylin and eosin. The fibroblasts appeared
Fig 3-Left, noninstrumented Clorox specimen. Note pulpal level well below cut surface (H&E, orig mag • 16). Right, noninstrumented Clorox specimen (H&E, orig mag • 88).
Fig 4-Noninstrumented Clorox specimen showing bleeding vessel at pulpal surface (H&E, orig mag X578).
to be smudged and the nuclei and cytoplasm pale and indistinct. In some cases, the nuclei of the fibroblasts were hyperchromatic and dispersed (Fig 4). The affected red blood cells were pale and basophilic with an indistinct cell membrane. Some appeared brownish and some appeared crenated, while others, presumably from fresh hemorrhage, appeared normal. Changes in the erythrocytes were also observed in deeper vessels. All changev in the remainder of the pulp were limited to the immediate subsurface.
Instrumented Teeth (Group B) Instrumentation with saline solution did not remove all of the predentin in any of the ten specimens and, in most cases, some residual tissue remained along canal walls and in accessory canals (Fig 6; 7, left). There was no extensive hemorrhage in any specimen. Four sections showed changes in the red blood cells. A plug of dentin filings was present in most specimens above the twisted, corn-
Fig 6--1nstrumented sahne specimen. Hemorrhage and tissue are present at orifice of lateral canal (H&E, orzg mag X 228).
Fig 5-Noninstrumented Clorox specimen showing progressive digestion of predentin. Note undisturbed irregular surface of the calcified dentin (H&E, orig mag X 228).
143
Fig 7--Left, instrumented saline specimen with residual tissue along canal wall (H&E, orig mag • 88). Right, instrumented saline specimen (H&E, orig mag • 16).
Fig 8-Left, instrumented saline specimen. Note plug of dentin filings (H&E, orig mag • 228). Right, instrumented Clorox specimen. Note absence of predentin and apical plug of dentin filings (H&E, orig mag
x16).
pressed pulp stump. This pulp tissue was too distorted to allow for the study of any cellular effects other than normal nuclear staining (Fig 7, right; 8, left). In almost all cases, instrumentation with NaOC1 removed all the predentin from areas that were both touched and untouched by the instruments (Fig 8, right). In one instance, a small amount of predentin was not removed. There was a 144
blue-staining line at the pulpal surface of four specimens (Fig 9), although none of the control teeth had this finding. There seemed to be no apparent difference in hemorrhage when compared to the controls. In almost all cases, residual tissue was removed from the walls of the root canal in teeth that were treated with NaOCI; the small piece that remained in one specimen had undergone digestive changes.
Changes in the morphology of the red blood cells were similar to the changes in group A. Fewer of the NaOCl-treated teeth than the salinetreated teeth contained an apical plug of loose dentin filings that rested on the residual pulp (Fig 8, right). In the few cases where this plug was missing, the residual tissue resembled that of group A (Fig 9). Lateral canals were affected by NaOC1 only in the region immedi-
JOURNAL OF E N D O D O N T I C S I VOL 4, NO 5, MAY 1978
Fig 9--Instrumented Clorox specimen. Note distinct line at pulpal surface (H&E, orig ,nag x578).
Measurements were made from the apical extent of instrumentation to the surface of the dentin plug or residual tissue. The mean value of 0.57 mm, compared to the mean value from the control group (0.50 ram), was not statistically significant. DISCUSSION
Fig lO--Instrumented Clorox specimen with contents of dentinal tubules removed (H&E, orig mag • 228).
ately adjacent to the main canal where some solvent action was noticed. The contents of the dentinal tubules were digested by the NaOC1 in 50% of the experimental groups and in none of the saline controls (Fig 10).
Measurements of the pulpal level indicate a strong solvent action of full-strength Clorox on the vital noninstrumented teeth. The limited solvent effect in the apical region may be attributed to the barrier of the apical plug of dentin filings, narrow lumen, and the fibrous nature of the apical pulp tissue? 8 The short time factor is probably most responsible for the absence of inflammatory cells in any of the specimens. The most consistent changes occurred in the predentin that was dissolved by the NaOC1. Orban ~7 reported that the predentin is essentially uncalcified dentin composed of bundles of Korffs' fibers (collagen),
smaller collagen fibrils, and ground substance composed of acid mucopolysaccharides. Predentin also contains nerve fibers and odontoblastic processes? 6 The loss of the predentin was not the result of instrumentation because the irregular surface of the calcified dentin had not been removed. Because these fragile areas of the calcified dentin remained, we have evidence of a solvent effect on predentin and also evidence that NaOC1 does not readily dissolve calcified tissue. The clinical significance of the effect on predentin and the contents of dentinal tubules becomes apparent when one considers previous studies showing that most bacteria are limited to the predentin and adjacent dentin of infected teeth? s It is reasonable to assume that compression of the pulpaI surface in NaOCl-treated teeth probably formed initially on application of irrigating pressure but was gradually digested by the NaOC1 during the remainder of the procedure. Because the tissue immediately below the distinct line at the surface of the NaOCl-treated teeth appeared norma!, we assumed that the solvent effect Of NaOC1 was greater than its necrotizing effect and any destroyed tissue was immediately removed. The hemorrhage was thought to be the result of progressive, indiscriminate tissue destruction by the NaOC1 with continuous exposure of deeper vessels. Of all the cells, the red blood cells seemed to be the most sensitive to the action of NaOC1. This study supports previously published works that reported the limited ability of NaOC1 to dissolve pulp tissue in confined areas. '~ However, in nonconfined areas, it is apparent that NaOC1 has a strong, 145
JOURNAL OF ENDODONTICS VOL 4, NO 5, MAY 1978
nonspecific, s u r f a c e - a c t i n g s o l v e n t a c t i o n o n vital, i n t a c t , y o u n g , p u l p tissue. In contradiction to a n o t h e r s t u d y , ~1 o u r results s h o w e d t h a t w i t h t h e e x c e p t i o n of t h e r e s t r i c t e d areas, t h e solvent a c t i o n o f N a O C 1 is g r e a t e r t h a n t h a t o f saline solution. O u r results also d o n o t a g r e e w i t h t h e results of o t h e r r e s e a r c h e r s w h o r e p o r t e d t h a t l i v i n g tissue will n o t be affected by this d r u g or t h a t a n i n t a c t c i r c u l a t i o n resists s o l v e n t action. 1~ T h e m a j o r b a r r i e r to be o v e r c o m e in t h e clinical use o f this p o p u l a r i r r i g a n t is its i n a b i l i t y to p e n e t r a t e c o n f i n e d areas. W h e n this p r o b l e m is solved it will e n h a n c e t h e success of endodontic procedures.
SUMMARY A N D CONCLUSIONS S o d i u m h y p o c h l o r i t e was c o m p a r e d to p h y s i o l o g i c saline s o l u t i o n in its a b i l i t y to dissolve v i t a l h u m a n p u l p tissue in 40 n o n i n s t r u m e n t e d and instrumented premolars. Microscopic e x a m i n a t i o n s h o w e d t h a t 5.25% N a O C 1 was m o r e effective t h a n saline s o l u t i o n a n d e x e r t e d a nonspecific, s u r f a c e - a c t i n g solvent a c t i o n on i n t a c t v i t a l p u l p tissue. T h e p r e d e n t i n a n d red b l o o d cells w e r e t h e most labile e l e m e n t s . T h e solvent effect was l i m i t e d b y a s m a l l
146
l u m e n a n d was m o s t effective in t h e m i d d l e a n d occlusal thirds. *Clorox, Clorox Co., Oakland, Calif. J'Cavit, Premier Dental Products, Philadelphia. ~Cal-Ex, Fisher Scientific Co., Fair Lawn,
nJ. Dr. Rosenfeld, former graduate student, University of Nebraska College of Dentistry, Lincoln, is currently in the practice of endodontics, Denver, Colo. Dr. James is professor and chairman of endodontics, University of Nebraska College of Dentistry, Lincoln. Dr. Burch, former associate professor of oral biology, University of Nebraska College of Dentistry, Lincoln, is currently professor of oral diagnosis and pathology at Creighton School of Dentistry, Omaha. Requests for reprints should be directed to Dr. Rosenfeld, 3525 S Tamarac Ct, Suite 240, Denver, Colo 80237.
References 1. Grossman, L. Endodontic practice, ed 7. Philadelphia, Lea & Febiger, 1970, pp 229239, 2. Luebke, R.G. Pulp cavity debridement and disinfection. Dent Clin N Am 11:603 Nov 1967. 3. Seltzer, S. Endodontology: biologic considerations in endodontic procedures. New York, McGraw-Hill, Inc., 1971, p 248. 4. Weine, F. Endodontic therapy. St. Louis, C. V. Mosby Co., 1972, pp 216-217. 5. Hand, R.E.; Smith, M.; and Harrison, J.W. Analysis of the effect of dilution on the necrotic tissue dissolution property of sodium hypochlorite. J Endod 4:60 Feb 1978. 6. Davis, S.R.; Brayton, S.M.; and Goldman, M. The morphology of the prepared root canal: a study utilizing injectable silicone. Oral Surg 34:642 Oct 1972.
7. Spangberg, L.; Engstrom, B.; and Langeland, K. Biologic effects of dental materials. 3. Toxicity and antimicrobial effect of endodontic antiseptics in vitro. Oral Surg 36:856 Dec 1973. 8. Grossman, L., and Meiman, B. Solution of pulp tissue by chemical agents. JADA 28:233 Feb 1941. 9. Gutierrez, J.H., and Garcia, J. Microscopic and macroscopic investigation on results of mechanical preparation of root canals. Oral Surg 25:108 Jan 1968. 10. Senia, E.; Marshall, F.; and Rosen, S. The solvent action of sodium hypochlorite on pulp tissue of extracted teeth. Oral Surg 31:96 Jan 1971. 11. Baker, N.A., and others. Scanning electron microscopic study of the efficacy of various irrigating solutions. J Endod 1:127 April 1975. 12. Grey, G.C. The capabilities of sodium hypochlorite to digest organic debris from root canals with emphasis on accessory canals, thesis. Boston University, 1970. 13. McComb, D.; Smith, D.C.; and Beagrie, G.S. The results of in vivo endodontie chemomechanical instrumentation-a scanning electron microscopic study. J Brit Endod Soc 9:11 Jan 1976. 14. Granath, L., and Hagman, G. Experimental pulpotomy in human bicuspids with reference to cutting technique. Acta Odontol Scand 29:155, 1971. 15. Siegel, S. Nonparametric statistics for the behavioral sciences. New York, McGraw Hill Co., 1956, pp 127-136, 278. 16. Seltzer, S., and Bender, I. The dental pulp. Biologic considerations in dental procedures. Philadelphia, J.B. Lippincott Go., 1965, pp 25, 75, 188. 17. Sicher, H. (ed.). Orban's oral histology and embryology, ed 6. St. Louis, G. V. Mosby Co., 1966, pp 118-123. 18. Bence, R., and others. A microbiologic evaluation of endodontic instrumentation in pulpless teeth. Oral Surg 35:676 May 1973.
