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Pulp capping in deciduous and newly erupted permanent teeth of monkeys
Pulp capping in deciduous and newly erupted permanent teeth of monkeys Marvin Chicago,
B. Weiss, D.D.S.,” and Kjell B,jormf~r, Z).D.R.,“* Ill., ad Bergen, No~wny
P
ulp capping has been used for many years as a means of maintaining pill{) vitality in teeth injured by caries attack. The majority of reports in the Iitentture have been based on clinical experience and the use of negative, subjective criteria, such as “absence of pain,” “ no evidence of radiographic changes,” “no patient complaints,” etc., rat,her than objective and measurable criteria based upon histologic research. This is particularly true in the case of deciduous ant1 young adult teeth, for human research material is not easily available in this area. The present study was undertaken to investigate methods of pulp prot.ti+ tion in young teeth by using deciduous and young adult teeth of MW~IC(I rr~~lotf~ (rhesus) monkeys, whose dentition is similar to t,hat of lll:ln. MATERIAL
AND
METHODS
Four monkeys were used. Three had mixed dentitions and one had n&. erupted permanent teeth. The animals were operateti on under general mc+ thesia (phencyclidine hydrochloride, 0.3 mg. per kilogram of body wcightt 1. The teeth were isolated with cotton rolls, and the occlusal surfaces of tfrn posterior teeth were prepared with a No. 557 bur in a low-speed handpit~c~tt without a coolant. When the occlusal preparation approached the pulp, an (LXposure was made w&h either a very small round bnr or an explorer. Seven IO nine teeth were operated on in each animal, making a total of thirty-one techt.11. linoperated teeth were used as controls. Following the pulp exposure, bleedirlg was controlled with cotton pellets. The exposures wc’rc then co~:cretl with on<’ 0-l four pulp-capping materials: calcium hydroxide mixed to a paste nith st,erilc water, Dyeal,+ CresatinS mixed with calcium hr:d~*osidc. or a fast-scttit\g. This study was supported in part by Public Health Service Grant D-1.320. *Univcrsit,y of Illinois at the Medical Center, College of Dentistry, Chicago, Ill. **De Odontologiske Institutter, Arstadveien, 5000 Bergen, Sorway. tsernylan, Parke, Davis $ Company, Detroit, Mich. $Dycnl (I,. D. Caulk Co., Milford, Del.), pulp-capping agent ; active ingredient, enlciunl hydroxide. GCresatiu-metacresylacetate (Merck Sharp 65 Dohme, West Point, Pa.), mixed with calcium hydroxide to consistency of wet sand. Surplus liquid is removed with cotton l)ellct after application on pulp exposure.
769
770
Weiss and Bjorvatn
Oral Burg. May, 1970
Table I Capping
material
Nwmber deciduous
Calcium hydroxide (in sterile water) Dycal Cresatin and calcium hydroxide ZOE Untreated controls
of teeth
Number permanent
of
teeth
Total of
nwmber teeth
5
3
8
ii 3 3
.: 3 4
134 6 7
hardened zinc oxide-eugenol cement (Weiss formula) .*I The remainder of the occlusal preparation was restored with modified zinc oxide and eugenol (ZOE) cement. The animals were killed after 1, 2, 4, and 5 weeks. The distribution of the treated teeth is shown in Table I. In one animal the experimental teeth were extracted and sectioned. In the other three, the teeth were cut out in blocks, including portions of the supporting bone, after the animals had been killed. The teeth were fixed in 10 per cent neutral formalin, decalcified in formic acid-sodium citrate solution, embedded in colloidin, sectioned serially at 10 microns; and stained with hematoxylin and eosin and Mallory’s triple connective tissue stain. FINDINGS
Most of the teeth retained the covering ZOE filling during the experimental period and did not develop any radiographic or histologically visible periapical pathosis. One tooth did lose the ZOE filling, and it developed necrosis of the pulp, but seemingly without periapical involvement. The pulpal reaction to each capping material was found to be different and characteristic for each of the medicaments used. Cresatin and calcium hydroxide. This group showed the most favorable healing in the pulp. Sections showed a well-marked border of fibrotic cells between the medicament and the normal pulp tissue after 1 week. There was only a narrow necrotic zone under the pulp-capping material and a thin border of “fixed” cells between the necrobiotic zone and the normal pulp (Fig. 1). After 4 to 5 weeks, this thin border became a definite calcified bridge of reparative dentine, separating the medicament and the vital pulp, with a line-up of normal odontoblasts on the pulpal side of the dentine bridge (Fig. 2). Calcium hydroxide (in sterile water) and Dycal. The results under these two medicaments were very similar. The specimens sectioned after the short experimental period demonstrated a wide zone of necrosis between the medicament and the vital pulp (Fig. 3). Specimens from the longer experimental period showed varied results, ranging from a thin fibrous bridging to a very heavy deposit of calcified material (Fig. 4). *Modified polystyrene.
zinc oxide-eugenol
(Weiss)
contains
zinc acetate,
bismuth
subcarbonate,
and
Volumc~ 5) Numljw 3
Fig. 1. One week. Cresatin stain.) Fig. 2. Five weeks. Cresatin
and calcium and calcium
hydroxide. hydroxide.
(Mallory’s (Hematoxylin
triple
connective
and eosin stain.)
tissue
772
Weiss and Bjorvatn
Oral Surg. May, 1970
4
Fig. stain.) Fig.
3. Seven weeks. 4. Five
Calcium
weeks. Calcium
hydroxide
hydroxide
and water. and water.
(Mallory’s
(Hematoxylin
triple
connective
and eosin stain.)
tissue
Volume Number
29 5
Fig. ii. Seven weeks. Zinc oxide and eugenol. (Hematoxylin Fig. 6. Four weeks. Zinc oxide and eugenol. (Mallory’s
and oosin stain.) triple counectivf!
tissue
staill.1
774
Weiss and Rjorvatn
Oral Surg. May, 1970
The bridging occurred later than under the Cresatin-calcium hydroxide mixture. Zinc oxide and eugenol. These specimens showed an almost complete lack of necrosis of the pulp with vital cells in direct contact with the medicament. There was little, if any, ordinary bridging between the medicament and the vital pulp. However, if there were any dentine chips in the pulp incident to the mechanical exposure, these chips were “cemented” together by calcified material, and this served as a barrier between the vital pulp and the exposure (Figs. 5 and 6). There was no difference in the pulpal reactions in deciduous and permanent teeth in the specimens examined in this study. DISCUSSION
The histologic evidence as observed in the teeth of monkeys supports the premise that the dental pulp has a great capacity to survive surgical trauma and undergo repair.2, 3 However, the experimental period was comparatively short and the long-range results can only be assumed from the histologic status of the pulp after 4 to 5 weeks. According to Swusch,4 the critical period for success or failure of pulp capping in human patients is between 6 and 12 months after the operation. When a definite thick dentine bridge is found to cover the amputated pulp area of monkeys’ teeth after 4 weeks, it may be concluded that the damage to the pulp has been repaired. This study has shown that there is a great variance in the “bridging” ol the pulp, especially under calcium hydroxide (mixed with water). The concept that a well-defined calcified bridge, as revealed by radiographs, is the best criterion for successful pulp capping should be examined more critically. For example, pulp capping with ZOE appears histologically to be just as successful as capping with the other medicaments. Although there was little or no calcific bridging, the pulp remains vital, even when in direct contact with the medicament. An interesting phenomenon is the role of dentinal chips in the repair of pulp exposure. Our observations are in accord with findings of Baker and Mitchell” and suggest that powdered dentine might be a good pulp-capping material. SUMMARY
Thirty-one monkey teeth were subjected to surgical pulp exposures. The exposures were capped with one of four medicaments and covered with modified ZOE cement. The biologic analysis of the teeth suggests the following conclusions : 1. Cresatin mixed with calcium hydroxide, used as a pulp-capping material, produced initial bridging after 1 week with only a small necrobiotic zone separating the medicament and the vital pulp. A period of 30 days was required to form a well-calcified dentine bridge covering the pulp exposure. 2. Calcium hydroxide (mixed with sterile water) and Dycal resulted in similar pulpal reactions. The initial reaction was a large zone of necrosis separating the medicament and the vital pulp. The bridging that occurred at a later
Volume Number
29 5
Pulp
capping
in monkey teeth
775
date was not consistent and varied from a thin fibrous barrier to a heavy amorphous calcified zone. 3. Zinc oxide and eugenol cement stimulated very little bridge formation but was well tolerated by the vital pulp in direct contact with the medicament. When dentine chips were present, they would form a calcific barrier by being cemented with a calcified material. 4. There was no a,pparent difference in the pulpal reactions of deciduous and permanent teeth. REFERENCES
1. Weiss, M. B.: An Improved Zinc Oxide and Eugenol Cement, Illinois Dent. J. 27: %I271 1958 2. Mafssler, ‘M.: Pulpal Reaction to Dental Caries, InL Dent. J. 17: 441-460, 1967. New York Dent. J. 32: 451-457, 1966. 3. Weiss, M. B.: Pulp Capping in Older Patients, 4. Swusch, R. H.: Dycal Capping of Exposed Pulps in Primary Teeth, J. Dent. Child. 30: 141-149, 1963. Antibiotic Treatment of Infected Dental 5. Baker,. 0. R., and Mitchell, D. F.: Topical Pulps In Monkeys, J. Dent. Res. 48: 351-355, 1969.
B. Weiss, D.D.S.,” and Kjell B,jormf~r, Z).D.R.,“* Ill., ad Bergen, No~wny
P
ulp capping has been used for many years as a means of maintaining pill{) vitality in teeth injured by caries attack. The majority of reports in the Iitentture have been based on clinical experience and the use of negative, subjective criteria, such as “absence of pain,” “ no evidence of radiographic changes,” “no patient complaints,” etc., rat,her than objective and measurable criteria based upon histologic research. This is particularly true in the case of deciduous ant1 young adult teeth, for human research material is not easily available in this area. The present study was undertaken to investigate methods of pulp prot.ti+ tion in young teeth by using deciduous and young adult teeth of MW~IC(I rr~~lotf~ (rhesus) monkeys, whose dentition is similar to t,hat of lll:ln. MATERIAL
AND
METHODS
Four monkeys were used. Three had mixed dentitions and one had n&. erupted permanent teeth. The animals were operateti on under general mc+ thesia (phencyclidine hydrochloride, 0.3 mg. per kilogram of body wcightt 1. The teeth were isolated with cotton rolls, and the occlusal surfaces of tfrn posterior teeth were prepared with a No. 557 bur in a low-speed handpit~c~tt without a coolant. When the occlusal preparation approached the pulp, an (LXposure was made w&h either a very small round bnr or an explorer. Seven IO nine teeth were operated on in each animal, making a total of thirty-one techt.11. linoperated teeth were used as controls. Following the pulp exposure, bleedirlg was controlled with cotton pellets. The exposures wc’rc then co~:cretl with on<’ 0-l four pulp-capping materials: calcium hydroxide mixed to a paste nith st,erilc water, Dyeal,+ CresatinS mixed with calcium hr:d~*osidc. or a fast-scttit\g. This study was supported in part by Public Health Service Grant D-1.320. *Univcrsit,y of Illinois at the Medical Center, College of Dentistry, Chicago, Ill. **De Odontologiske Institutter, Arstadveien, 5000 Bergen, Sorway. tsernylan, Parke, Davis $ Company, Detroit, Mich. $Dycnl (I,. D. Caulk Co., Milford, Del.), pulp-capping agent ; active ingredient, enlciunl hydroxide. GCresatiu-metacresylacetate (Merck Sharp 65 Dohme, West Point, Pa.), mixed with calcium hydroxide to consistency of wet sand. Surplus liquid is removed with cotton l)ellct after application on pulp exposure.
769
770
Weiss and Bjorvatn
Oral Burg. May, 1970
Table I Capping
material
Nwmber deciduous
Calcium hydroxide (in sterile water) Dycal Cresatin and calcium hydroxide ZOE Untreated controls
of teeth
Number permanent
of
teeth
Total of
nwmber teeth
5
3
8
ii 3 3
.: 3 4
134 6 7
hardened zinc oxide-eugenol cement (Weiss formula) .*I The remainder of the occlusal preparation was restored with modified zinc oxide and eugenol (ZOE) cement. The animals were killed after 1, 2, 4, and 5 weeks. The distribution of the treated teeth is shown in Table I. In one animal the experimental teeth were extracted and sectioned. In the other three, the teeth were cut out in blocks, including portions of the supporting bone, after the animals had been killed. The teeth were fixed in 10 per cent neutral formalin, decalcified in formic acid-sodium citrate solution, embedded in colloidin, sectioned serially at 10 microns; and stained with hematoxylin and eosin and Mallory’s triple connective tissue stain. FINDINGS
Most of the teeth retained the covering ZOE filling during the experimental period and did not develop any radiographic or histologically visible periapical pathosis. One tooth did lose the ZOE filling, and it developed necrosis of the pulp, but seemingly without periapical involvement. The pulpal reaction to each capping material was found to be different and characteristic for each of the medicaments used. Cresatin and calcium hydroxide. This group showed the most favorable healing in the pulp. Sections showed a well-marked border of fibrotic cells between the medicament and the normal pulp tissue after 1 week. There was only a narrow necrotic zone under the pulp-capping material and a thin border of “fixed” cells between the necrobiotic zone and the normal pulp (Fig. 1). After 4 to 5 weeks, this thin border became a definite calcified bridge of reparative dentine, separating the medicament and the vital pulp, with a line-up of normal odontoblasts on the pulpal side of the dentine bridge (Fig. 2). Calcium hydroxide (in sterile water) and Dycal. The results under these two medicaments were very similar. The specimens sectioned after the short experimental period demonstrated a wide zone of necrosis between the medicament and the vital pulp (Fig. 3). Specimens from the longer experimental period showed varied results, ranging from a thin fibrous bridging to a very heavy deposit of calcified material (Fig. 4). *Modified polystyrene.
zinc oxide-eugenol
(Weiss)
contains
zinc acetate,
bismuth
subcarbonate,
and
Volumc~ 5) Numljw 3
Fig. 1. One week. Cresatin stain.) Fig. 2. Five weeks. Cresatin
and calcium and calcium
hydroxide. hydroxide.
(Mallory’s (Hematoxylin
triple
connective
and eosin stain.)
tissue
772
Weiss and Bjorvatn
Oral Surg. May, 1970
4
Fig. stain.) Fig.
3. Seven weeks. 4. Five
Calcium
weeks. Calcium
hydroxide
hydroxide
and water. and water.
(Mallory’s
(Hematoxylin
triple
connective
and eosin stain.)
tissue
Volume Number
29 5
Fig. ii. Seven weeks. Zinc oxide and eugenol. (Hematoxylin Fig. 6. Four weeks. Zinc oxide and eugenol. (Mallory’s
and oosin stain.) triple counectivf!
tissue
staill.1
774
Weiss and Rjorvatn
Oral Surg. May, 1970
The bridging occurred later than under the Cresatin-calcium hydroxide mixture. Zinc oxide and eugenol. These specimens showed an almost complete lack of necrosis of the pulp with vital cells in direct contact with the medicament. There was little, if any, ordinary bridging between the medicament and the vital pulp. However, if there were any dentine chips in the pulp incident to the mechanical exposure, these chips were “cemented” together by calcified material, and this served as a barrier between the vital pulp and the exposure (Figs. 5 and 6). There was no difference in the pulpal reactions in deciduous and permanent teeth in the specimens examined in this study. DISCUSSION
The histologic evidence as observed in the teeth of monkeys supports the premise that the dental pulp has a great capacity to survive surgical trauma and undergo repair.2, 3 However, the experimental period was comparatively short and the long-range results can only be assumed from the histologic status of the pulp after 4 to 5 weeks. According to Swusch,4 the critical period for success or failure of pulp capping in human patients is between 6 and 12 months after the operation. When a definite thick dentine bridge is found to cover the amputated pulp area of monkeys’ teeth after 4 weeks, it may be concluded that the damage to the pulp has been repaired. This study has shown that there is a great variance in the “bridging” ol the pulp, especially under calcium hydroxide (mixed with water). The concept that a well-defined calcified bridge, as revealed by radiographs, is the best criterion for successful pulp capping should be examined more critically. For example, pulp capping with ZOE appears histologically to be just as successful as capping with the other medicaments. Although there was little or no calcific bridging, the pulp remains vital, even when in direct contact with the medicament. An interesting phenomenon is the role of dentinal chips in the repair of pulp exposure. Our observations are in accord with findings of Baker and Mitchell” and suggest that powdered dentine might be a good pulp-capping material. SUMMARY
Thirty-one monkey teeth were subjected to surgical pulp exposures. The exposures were capped with one of four medicaments and covered with modified ZOE cement. The biologic analysis of the teeth suggests the following conclusions : 1. Cresatin mixed with calcium hydroxide, used as a pulp-capping material, produced initial bridging after 1 week with only a small necrobiotic zone separating the medicament and the vital pulp. A period of 30 days was required to form a well-calcified dentine bridge covering the pulp exposure. 2. Calcium hydroxide (mixed with sterile water) and Dycal resulted in similar pulpal reactions. The initial reaction was a large zone of necrosis separating the medicament and the vital pulp. The bridging that occurred at a later
Volume Number
29 5
Pulp
capping
in monkey teeth
775
date was not consistent and varied from a thin fibrous barrier to a heavy amorphous calcified zone. 3. Zinc oxide and eugenol cement stimulated very little bridge formation but was well tolerated by the vital pulp in direct contact with the medicament. When dentine chips were present, they would form a calcific barrier by being cemented with a calcified material. 4. There was no a,pparent difference in the pulpal reactions of deciduous and permanent teeth. REFERENCES
1. Weiss, M. B.: An Improved Zinc Oxide and Eugenol Cement, Illinois Dent. J. 27: %I271 1958 2. Mafssler, ‘M.: Pulpal Reaction to Dental Caries, InL Dent. J. 17: 441-460, 1967. New York Dent. J. 32: 451-457, 1966. 3. Weiss, M. B.: Pulp Capping in Older Patients, 4. Swusch, R. H.: Dycal Capping of Exposed Pulps in Primary Teeth, J. Dent. Child. 30: 141-149, 1963. Antibiotic Treatment of Infected Dental 5. Baker,. 0. R., and Mitchell, D. F.: Topical Pulps In Monkeys, J. Dent. Res. 48: 351-355, 1969.