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Pulpal reaction to polycarboxylate and zinc phosphate cements used with inlays in deep cavity preparations
H is to lo g ie analysis of the pu lp u n d e r 78 deep inlays experim enta lly cem ented w ith e ither a p o lycarboxyla te o r a zin c phosphate cem ent revealed th a t n e ith e r o f the cem ents had irritated the pulp. Pulpal reactions reported in previous studies seem to have been a ttrib u ta b le to in fe ctio n . The results em phasize th e im p o rta n ce of rem oving g rin d in g debris and bacteria fro m th e prepared surfaces before cem entation.
Pulpal reaction to polycarboxylate and zinc phosphate cements used with inlays in deep cavity preparations Martin Brànnstrôm, DDS, PhD, S to c k h o lm Hilding Nyborg, DDS, PhD, A rvika, S weden Polycarboxylate cem ent is a new product de scribed by S m ith.1 H e found this cem ent to have no significant effect on the pulp. O ther investi gators who have used polycarboxylate cem ent as a filling m aterial or liner have arrived at the sam e conclusion.2'6 An insignificant inflamma tory reaction of the pulp has been noted in some cases, but as a rule, polycarboxylate cem ent is regarded as less irritating to the pulp than zinc phosphate cem ent. From a biologic point of view, then, the form er type of cem ent should be preferred. Z inc phosphate cem ent has long been known to have an irritating effect on the pulp, presum ably because of its acidity. Fifteen years ago, we studied in experim ents the reactions of pulp un d er inlays cem ented with this m aterial and found that notable reactions som etimes occurred if the pulp had not been protected with a polystyrene lin er.7 In this investigation the cavity prepara tions w ere cleaned with w ater only. In a later series o f the sam e experim ents in which the prep arations w ere cleaned with a surface-active and m icrobicidal solution, practically no pulpal reac tions w ere ob served.8 In view of this unexpect ed result with 20 inlays cem ented with zinc phosphate cem ent, a new experim ental series was started with the use of the sam e method. T he purpose was to carry out a com parative in vestigation on contralateral pairs of teeth with zinc phosphate cem ent and polycarboxylate cem ent. 308 ■ JADA, Vol. 94, February 1977
M a te ria ls a n d m e th o d s
F orty-one pairs o f young prem olars extracted for orthodontic reasons w ere used. Uniform cav ities w ere prepared on the buccal surfaces, first with a diam ond stone through the enamel and then round tungsten carbide burs. Each prepara tion was com pleted with a cylindrical bur. The resulting cavity had a diam eter of 2 mm and a depth of about 2.5 mm. T he cavity was cut at 6,000 rpm under a w ater coolant. A lead inlay with a rim o f the sam e dim ensions was trimmed to fit each cavity preparation. Before cem enta tion of the inlays, the cavity preparations were cleaned with w ater spray and then air dried for five seconds; this was followed by rubbing of the cavity walls for a few seconds with a pellet soaked in a surface-active and m icrobicidal sol ution.* T he solution was then left in the cavity for one m inute before th e preparation was dried with com pressed air for five seconds. In one of the cavity preparations of each pair (decided by lot), the inlay was cem ented with a zinc phosphate ce m e n t,t and the inlay in the oth er tooth was cem ented with a polycarboxylate ce m e n t.t T he cem ent was prepared according to the m anufacturer’s instructions for the powderliquid ratio and the mixing time (for zinc phos phate cem ent, 80 seconds), and then the cem ent, in a thin, drop consistency, was applied to the cavity. On cem entation, the inlay was burnished
flush with the enam el to provide as reliable a seal as possible. T hirteen pairs of teeth were extract ed after seven to ten days and 28 pairs after four to six weeks. T he histologic preparation of the teeth has been described earlier.8-9 T he exam iners of the sections w ere not aw are of the type of cem ent used.
F in d in g s
T he shortest distance, m easured along the den tinal tubules, betw een the pulp and the floor of the cavity preparation in which the inlay had been cem ented with phosphate cem ent was 0 (lesion) to 1 mm (mean 0.42). T he corresponding values for teeth in which the polycarboxylate cem ent was used w ere 0 to 0.9 mm (mean 0.44). Pulpal lesions w ere found under four inlays. B acterial deposit was found on the floor of only 1 of the 82 cavity preparations. In this particular tooth, the inlay had been cem ented with zinc phosphate cem ent. N o signs of pulpal inflammation were seen in 76 of the 78 teeth. O f these 76, zinc phosphate cem ent had been used in 37 (Illustration) and polycarboxylate cem ent in 39. Only in tw o teeth did the pulps show a m oderate infiltration of in flam m atory cells. One of the teeth was the one in which bacteria had been observed on the floor of the preparation. T he inlays in both teeth had been cem ented with zinc phosphate cement. In the teeth with pulpal lesions, two of the in lays had been fixed with one type of cem ent and tw o with the other. A mild to m oderate infiltra tion of inflam m atory cells was found. T hree of these teeth had been extracted after seven to ten days. A reduced num ber of odontoblasts was seen in 17 teeth in which zinc phosphate cem ent had been used and in 6 in which polycarboxylate cem ent had been used. Aspiration of cell nuclei into the dentinal tubules was found in ten teeth with inlays cem ented with phosphate cem ent, but only in one in which the inlay had been fixed with carboxylate cement.
D is c u s s io n
T he results of this investigation indicate that zinc phosphate cem ent used as a cementing me dium does not cause inflammation of the pulp (detectable by histologic examination) after one
Inlay cemented with zinc phosphate cement. Follow -up period, fo u r weeks. Distance to pulp 0.1 mm. No exudate cells in pulp. (Original m agnification, x120.)
to six w eeks, despite the thinness of the dentin layer. It is obvious that polycarboxylate cem ent does not irritate the pulp either. Beneath only 2 of the 39 inlays cem ented with phosphate cem ent w ere inflam m atory reactions found. If the reaction w ere caused by irritation of the cem ent, it would be difficult to explain why no such reaction occurred under the other 37 inlays. On the other hand, it is not difficult to explain the reaction under the tw o inlays. T he floor of one of the cavity preparations was cov ered by a layer of bacteria, possibly as a result of unsatisfactory cleaning of the cavity preparation or contam ination after the preparation had been disinfected. In the other tooth, bacteria may also have entered but may have been rem oved together with the inlay before the tooth was sec tioned. Occasionally we have observed bacterial deposits on a restoration rem oved from a cavity after décalcification of the tooth (B rânnstrôm and N ordenvall, unpublished data). T he results agree with those o f our earlier in vestigation. In that series o f 20 inlays cem ented with phosphate cem ent in cavity preparations cleaned of grinding debris and bacteria, inflam m atory reaction was seen in the pulps beneath only two of the inlays.8 T he present com parative investigation suggests that, from a biologic point of view, there is no reason to prefer polycarboxy late cem ent to phosphate cem ent. A lso, results obtained in retention tests with these cem ents suggest that when the dentin is properly freed from grinding debris, retention of crowns is largely the same with use of either cem ent.10 Pulpal inflammation observed in earlier inves tigations, particularly when zinc phosphate ce ment has been used, can apparently be explained by two factors: first, deficient cleansing of the cavity preparation and, therefore, incom plete B rannstróm — Nyborg: PULPAL REACTION TO CEMENTS ■ 309
removal of grinding debris with bacteria; and, second, the effect of the cement on the pulp, re sulting in a contraction gap between the cement and dentin sufficient to permit ingrowth of bac teria from the surface of the tooth. This has been examined experimentally, usually by filling of the entire cavity preparation with cement. O ur findings emphasize the importance of cleaning the prepared surfaces from grinding de bris and bacteria before cementation. This im proves not only retention of the cemented restor ation, but also greatly reduces the risk of pulpal irritation. It also seems important to avoid thick layers of the cement, which might contribute to a contraction gap between the cement and the dentin. Bacteria present might increase in num ber and completely fill such a gap. Zinc oxide-eugenol cement has been recom mended as a cementing medium particularly be cause it has barely any effect on the pulp. In a recent experimental investigation of this cement, we found a mild to moderate inflammatory reac tion in the pulp beneath 51 of 63 restorations.11 This observation agrees also with the findings of Pohto and Scheinin.12 A comparison with the present results suggests that a zinc oxide-eugenol cement may be more irritating to the pulp than zinc phosphate cement.
Summary The purpose of the present investigation was to compare histologically pulpal reactions be neath inlays cemented with either a zinc phos phate or a polycarboxylate cement. N o inflammatory reaction was seen beneath any of the 39 deep cavity preparations in teeth without pulpal lesions and with an inlay cement ed with polycarboxylate cement. In the contralateral teeth, under 39 inlays cem ented with zinc phosphate cement, an inflamma tory reaction was seen beneath two cavity prep arations. In one, bacteria were found on the floor of the preparation. On the basis of this result and the findings of
310 ■ JADA, Vol. 94, February 1977
our earlier investigations, it may be warranted to conclude that neither the polycarboxylate cement nor the zinc phosphate cement has any notable irritating effect on the pulp. If the irrita tion occurs after cementation of the restoration, it may be caused by debris containing bacteria and left behind on the prepared surfaces by bac terial growth from the surface of the tooth. The findings underline the importance of removing grinding debris and bacteria before cementation of the restoration.
Dr. Brannstrom is associate professor in the department of oral pathology at the Karolinska Instltutet, School of Dentistry, Box 3207, S-103 64 Stockholm 3, Sweden. Dr. Nyborg, now re tired, was with the department of endodontics, Dental School, U m e i Sweden. Address requests for reprints to Dr. Brannstrom. *Tubulicid, Dental Therapeutics AB, Ektorp, Sweden. tTenazinc, De Trey AG, Zurich, Switzerland. t3M Brand polycarboxylate cement, Minnesota Mining & Mfg. Co., St. Paul, 55101. 1. Smith, D.C. A new dental cement. Br Dent J 124:381 Nov 1968. 2. Beardsley, S.H.; Auvenshlne, R.C.; and Eames, W.B. Pulpal response to composite resin and polycarboxylate cement. Ab stracted, IADR Program & Abstracts no. 37 March 1973. 3. Safer, D.S.; Avery, J.K.; and Cox, C.F. Histopathologic eval uation of the effects of new polycarboxylate cements on monkey pulps. Oral Surg 33:966 June 1972. 4. Racette, W.A., and others. Pulpal responses to newly form ulated polycarboxylate liner. J Dent Res 53 (special issue):193 abstract no. 553 Feb 1974. 5. Van Leeuwen, M., and others. A comparison of polycarbox ylate to two other dental cements. J Dent Res 53 (special issue): 191 abstract no. 546 Feb 1974. 6. El-Kafrawy, A.H., and others. Pulp reaction to a polycar boxylate cement in monkeys. J Dent Res 53:15 Jan-Feb 1974. 7. Brannstrom, M., and Nyborg, H. Dentinal and pulpal re sponse. IV. Pulp reaction to zinc oxyphosphate cement— a mor phologic study on dog and man. Odont Revy 11:37 No. 1, 1960. 8. Brannstrom, M., and Nyborg, H. Bacterial growth and pulpal changes under inlays cemented with zinc phosphate cement and Epoxylite CBA 9080. J Prosthet Dent 3 1 :556 May 1974. 9. Brannstrom, M., and Nyborg, H. Points in the experimental study of pulpal response to restorative materials. Odont Tidskr 77:421 No. 5-6, 1969. 10. Glantz, P.O. The retention of crowns cemented under various conditions. Symposium Swedish Dental Society Meeting, March 1973. 11. Brannstrom, M„ and Nyborg, H. Pulpal reaction to a tem porary zinc oxide-eugenol cement. J Prosthet Dent 35:185 Feb 1976. 12. Pohto, M., and Scheinin, A. Mikroskoplska undersokningar av levande tandpulpa. Odont Tidskr 69:86 No. 1, 1961.
Pulpal reaction to polycarboxylate and zinc phosphate cements used with inlays in deep cavity preparations Martin Brànnstrôm, DDS, PhD, S to c k h o lm Hilding Nyborg, DDS, PhD, A rvika, S weden Polycarboxylate cem ent is a new product de scribed by S m ith.1 H e found this cem ent to have no significant effect on the pulp. O ther investi gators who have used polycarboxylate cem ent as a filling m aterial or liner have arrived at the sam e conclusion.2'6 An insignificant inflamma tory reaction of the pulp has been noted in some cases, but as a rule, polycarboxylate cem ent is regarded as less irritating to the pulp than zinc phosphate cem ent. From a biologic point of view, then, the form er type of cem ent should be preferred. Z inc phosphate cem ent has long been known to have an irritating effect on the pulp, presum ably because of its acidity. Fifteen years ago, we studied in experim ents the reactions of pulp un d er inlays cem ented with this m aterial and found that notable reactions som etimes occurred if the pulp had not been protected with a polystyrene lin er.7 In this investigation the cavity prepara tions w ere cleaned with w ater only. In a later series o f the sam e experim ents in which the prep arations w ere cleaned with a surface-active and m icrobicidal solution, practically no pulpal reac tions w ere ob served.8 In view of this unexpect ed result with 20 inlays cem ented with zinc phosphate cem ent, a new experim ental series was started with the use of the sam e method. T he purpose was to carry out a com parative in vestigation on contralateral pairs of teeth with zinc phosphate cem ent and polycarboxylate cem ent. 308 ■ JADA, Vol. 94, February 1977
M a te ria ls a n d m e th o d s
F orty-one pairs o f young prem olars extracted for orthodontic reasons w ere used. Uniform cav ities w ere prepared on the buccal surfaces, first with a diam ond stone through the enamel and then round tungsten carbide burs. Each prepara tion was com pleted with a cylindrical bur. The resulting cavity had a diam eter of 2 mm and a depth of about 2.5 mm. T he cavity was cut at 6,000 rpm under a w ater coolant. A lead inlay with a rim o f the sam e dim ensions was trimmed to fit each cavity preparation. Before cem enta tion of the inlays, the cavity preparations were cleaned with w ater spray and then air dried for five seconds; this was followed by rubbing of the cavity walls for a few seconds with a pellet soaked in a surface-active and m icrobicidal sol ution.* T he solution was then left in the cavity for one m inute before th e preparation was dried with com pressed air for five seconds. In one of the cavity preparations of each pair (decided by lot), the inlay was cem ented with a zinc phosphate ce m e n t,t and the inlay in the oth er tooth was cem ented with a polycarboxylate ce m e n t.t T he cem ent was prepared according to the m anufacturer’s instructions for the powderliquid ratio and the mixing time (for zinc phos phate cem ent, 80 seconds), and then the cem ent, in a thin, drop consistency, was applied to the cavity. On cem entation, the inlay was burnished
flush with the enam el to provide as reliable a seal as possible. T hirteen pairs of teeth were extract ed after seven to ten days and 28 pairs after four to six weeks. T he histologic preparation of the teeth has been described earlier.8-9 T he exam iners of the sections w ere not aw are of the type of cem ent used.
F in d in g s
T he shortest distance, m easured along the den tinal tubules, betw een the pulp and the floor of the cavity preparation in which the inlay had been cem ented with phosphate cem ent was 0 (lesion) to 1 mm (mean 0.42). T he corresponding values for teeth in which the polycarboxylate cem ent was used w ere 0 to 0.9 mm (mean 0.44). Pulpal lesions w ere found under four inlays. B acterial deposit was found on the floor of only 1 of the 82 cavity preparations. In this particular tooth, the inlay had been cem ented with zinc phosphate cem ent. N o signs of pulpal inflammation were seen in 76 of the 78 teeth. O f these 76, zinc phosphate cem ent had been used in 37 (Illustration) and polycarboxylate cem ent in 39. Only in tw o teeth did the pulps show a m oderate infiltration of in flam m atory cells. One of the teeth was the one in which bacteria had been observed on the floor of the preparation. T he inlays in both teeth had been cem ented with zinc phosphate cement. In the teeth with pulpal lesions, two of the in lays had been fixed with one type of cem ent and tw o with the other. A mild to m oderate infiltra tion of inflam m atory cells was found. T hree of these teeth had been extracted after seven to ten days. A reduced num ber of odontoblasts was seen in 17 teeth in which zinc phosphate cem ent had been used and in 6 in which polycarboxylate cem ent had been used. Aspiration of cell nuclei into the dentinal tubules was found in ten teeth with inlays cem ented with phosphate cem ent, but only in one in which the inlay had been fixed with carboxylate cement.
D is c u s s io n
T he results of this investigation indicate that zinc phosphate cem ent used as a cementing me dium does not cause inflammation of the pulp (detectable by histologic examination) after one
Inlay cemented with zinc phosphate cement. Follow -up period, fo u r weeks. Distance to pulp 0.1 mm. No exudate cells in pulp. (Original m agnification, x120.)
to six w eeks, despite the thinness of the dentin layer. It is obvious that polycarboxylate cem ent does not irritate the pulp either. Beneath only 2 of the 39 inlays cem ented with phosphate cem ent w ere inflam m atory reactions found. If the reaction w ere caused by irritation of the cem ent, it would be difficult to explain why no such reaction occurred under the other 37 inlays. On the other hand, it is not difficult to explain the reaction under the tw o inlays. T he floor of one of the cavity preparations was cov ered by a layer of bacteria, possibly as a result of unsatisfactory cleaning of the cavity preparation or contam ination after the preparation had been disinfected. In the other tooth, bacteria may also have entered but may have been rem oved together with the inlay before the tooth was sec tioned. Occasionally we have observed bacterial deposits on a restoration rem oved from a cavity after décalcification of the tooth (B rânnstrôm and N ordenvall, unpublished data). T he results agree with those o f our earlier in vestigation. In that series o f 20 inlays cem ented with phosphate cem ent in cavity preparations cleaned of grinding debris and bacteria, inflam m atory reaction was seen in the pulps beneath only two of the inlays.8 T he present com parative investigation suggests that, from a biologic point of view, there is no reason to prefer polycarboxy late cem ent to phosphate cem ent. A lso, results obtained in retention tests with these cem ents suggest that when the dentin is properly freed from grinding debris, retention of crowns is largely the same with use of either cem ent.10 Pulpal inflammation observed in earlier inves tigations, particularly when zinc phosphate ce ment has been used, can apparently be explained by two factors: first, deficient cleansing of the cavity preparation and, therefore, incom plete B rannstróm — Nyborg: PULPAL REACTION TO CEMENTS ■ 309
removal of grinding debris with bacteria; and, second, the effect of the cement on the pulp, re sulting in a contraction gap between the cement and dentin sufficient to permit ingrowth of bac teria from the surface of the tooth. This has been examined experimentally, usually by filling of the entire cavity preparation with cement. O ur findings emphasize the importance of cleaning the prepared surfaces from grinding de bris and bacteria before cementation. This im proves not only retention of the cemented restor ation, but also greatly reduces the risk of pulpal irritation. It also seems important to avoid thick layers of the cement, which might contribute to a contraction gap between the cement and the dentin. Bacteria present might increase in num ber and completely fill such a gap. Zinc oxide-eugenol cement has been recom mended as a cementing medium particularly be cause it has barely any effect on the pulp. In a recent experimental investigation of this cement, we found a mild to moderate inflammatory reac tion in the pulp beneath 51 of 63 restorations.11 This observation agrees also with the findings of Pohto and Scheinin.12 A comparison with the present results suggests that a zinc oxide-eugenol cement may be more irritating to the pulp than zinc phosphate cement.
Summary The purpose of the present investigation was to compare histologically pulpal reactions be neath inlays cemented with either a zinc phos phate or a polycarboxylate cement. N o inflammatory reaction was seen beneath any of the 39 deep cavity preparations in teeth without pulpal lesions and with an inlay cement ed with polycarboxylate cement. In the contralateral teeth, under 39 inlays cem ented with zinc phosphate cement, an inflamma tory reaction was seen beneath two cavity prep arations. In one, bacteria were found on the floor of the preparation. On the basis of this result and the findings of
310 ■ JADA, Vol. 94, February 1977
our earlier investigations, it may be warranted to conclude that neither the polycarboxylate cement nor the zinc phosphate cement has any notable irritating effect on the pulp. If the irrita tion occurs after cementation of the restoration, it may be caused by debris containing bacteria and left behind on the prepared surfaces by bac terial growth from the surface of the tooth. The findings underline the importance of removing grinding debris and bacteria before cementation of the restoration.
Dr. Brannstrom is associate professor in the department of oral pathology at the Karolinska Instltutet, School of Dentistry, Box 3207, S-103 64 Stockholm 3, Sweden. Dr. Nyborg, now re tired, was with the department of endodontics, Dental School, U m e i Sweden. Address requests for reprints to Dr. Brannstrom. *Tubulicid, Dental Therapeutics AB, Ektorp, Sweden. tTenazinc, De Trey AG, Zurich, Switzerland. t3M Brand polycarboxylate cement, Minnesota Mining & Mfg. Co., St. Paul, 55101. 1. Smith, D.C. A new dental cement. Br Dent J 124:381 Nov 1968. 2. Beardsley, S.H.; Auvenshlne, R.C.; and Eames, W.B. Pulpal response to composite resin and polycarboxylate cement. Ab stracted, IADR Program & Abstracts no. 37 March 1973. 3. Safer, D.S.; Avery, J.K.; and Cox, C.F. Histopathologic eval uation of the effects of new polycarboxylate cements on monkey pulps. Oral Surg 33:966 June 1972. 4. Racette, W.A., and others. Pulpal responses to newly form ulated polycarboxylate liner. J Dent Res 53 (special issue):193 abstract no. 553 Feb 1974. 5. Van Leeuwen, M., and others. A comparison of polycarbox ylate to two other dental cements. J Dent Res 53 (special issue): 191 abstract no. 546 Feb 1974. 6. El-Kafrawy, A.H., and others. Pulp reaction to a polycar boxylate cement in monkeys. J Dent Res 53:15 Jan-Feb 1974. 7. Brannstrom, M., and Nyborg, H. Dentinal and pulpal re sponse. IV. Pulp reaction to zinc oxyphosphate cement— a mor phologic study on dog and man. Odont Revy 11:37 No. 1, 1960. 8. Brannstrom, M., and Nyborg, H. Bacterial growth and pulpal changes under inlays cemented with zinc phosphate cement and Epoxylite CBA 9080. J Prosthet Dent 3 1 :556 May 1974. 9. Brannstrom, M., and Nyborg, H. Points in the experimental study of pulpal response to restorative materials. Odont Tidskr 77:421 No. 5-6, 1969. 10. Glantz, P.O. The retention of crowns cemented under various conditions. Symposium Swedish Dental Society Meeting, March 1973. 11. Brannstrom, M„ and Nyborg, H. Pulpal reaction to a tem porary zinc oxide-eugenol cement. J Prosthet Dent 35:185 Feb 1976. 12. Pohto, M., and Scheinin, A. Mikroskoplska undersokningar av levande tandpulpa. Odont Tidskr 69:86 No. 1, 1961.