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Setting time of selected essential oils with a standard root canal cement powder
JOURNAL OF ENDODONTICS [ VOL 8, NO 6, JUNE 1982
Setting time of selected essential oils with a standard root canal cement powder L o u i s I. G r o s s m a n , DDS, Dr Med Dent
F o u r e s s e n t i a l oils, w h i c h are b i o l o g i c a l l y less i r r i t a t i n g t h a n e u g e n o l , were mixed with a standard root canal cement powder, and the s e t t i n g t i m e s of t h e s e c e m e n t s w a s d e t e r m i n e d . O f t h e f o u r c e m e n t s tested, o n l y t h e c e m e n t u s i n g oil of p i m e n t a leaf h a d a s e t t i n g t i m e c o m p a r a b l e to t h a t of r o o t c a n a l c e m e n t p o w d e r m i x e d w i t h e u g e n o l .
The setting time of eugenolate root canal cements has been studied by Wiener and Schilder, 1 Grossman, z and Benatti and others? Eugenolate cements are oxides of metals, such as zinc oxide, in corfibination with eugenol. Certain essential oils are less irritating than eugenol, 4 such as anethole, anise, eucalyptol, and pimenta leaf. The purpose of this study was to determine the setting time of root canal cements after each of these oils was combined with a standard root canal cement powder. The formula for the powder s is as follows: zinc oxide, 42 parts; staybelite resin, 27 parts; bismuth subcarbonate, 15 parts; barium sulphate, 15 parts; sodium borate, 1 part; all parts by weight.
MATERIALS AND
METHODS
Dormann spacers have an outside diameter of 16 ram, an inside diameter of 6 mm, and are 0.8 mm thick; the spacers were attached with two pin-
heads of sticky wax to the top surface of plastic petri plates. A comparison had been made of the setting time of the control cement when glass or plastic petri plates were used. No difference was observed. Only two spacers were used on each plate; the spacers were filled with cement, and the plates were immediately placed in an incubator at 37 C, with 100% relative humidity. The control powder for the cement was freshly prepared in a mortar using a pestle and passed through a 100mesh sieve. A quantity of the powder, weighing approximately 0.12 gm, was mixed with 0.07 gm of the essential oil. The powder and eugenol in the prescribed amounts were mixed to form a cement that was used as a control. The powder was incorporated into the essential oil in small amounts on a glass slab 15 X7.5 • 1.5 cm with a stainless steel spatula until the cement mass met the following criteria: resistance was felt to spatulation; half of the cement mix took from 12 to 15 seconds to drop off the spatula as it was held edgewise;
and after the spatula was placed flat against the collected cement mass and was slowly lifted, the cement strung out for at least an inch without breaking. The mixing time took approximately five minutes to thoroughly incorporate the powder into the liquid and to make a smooth cement. The cement was then collected at the tip of the spatula and allowed to drop slowly from the spatula into the opening of the Dormann spacer. Each opening was filled level with the top surface of the spacer, and any excess was removed. The length of time the cement was placed in the spacer opening was recorded. When both spacers were filled with cement, the plate was placed in an incubator at 37 C with 100% relative humidity. No more than two cement mixes were placed on each plate to subject the cement to the predetermined temperature and humidity as soon as possible. The cements were tested for setting time (hardness) every half hour during the first three hours, then hourly for six hours when possible, and observed
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JOURNAL OF ENDODONTICS JVOL 8, NO 6, JUNE 1982
again the next morning. If the cement was already set at the end of the first hour, observations were made every ten minutes for subsequent mixes. The method of testing included the use of a modified Gilmore needle made by attaching a no. 70 reamer to a 100-gin weight (Fig 1). T h e instrument was held between thumb and finger and lowered into the cement. The setting stages of the cement were recorded according to the following descriptions: soft, the needle met with no resistance; doughy, the needle met with some resistance, but pulled a bit of cement with it as the needle was being withdrawn (Fig 2); indented, the needle, after being pulled out of the cement, left a clean hole (Fig 3); hard, the needle left no mark on the completely hard cement (Fig 4). Eugenol, mixed with the same powder, was used as a control.
Fzg l--Modified Gilmore needle made by attaching 770. 70 reamer to lO0-gm weight for testing setting times of root canal cements.
Fig 2--Stages in setting of root canal cements. Doughy, the cement follows modified Gffmore needle as it is being removed from cement, leaving a hillock above surface of cement.
Fig 3--Indented, Gilmore needle penetrated cement and left clean hollow on removal.
Fig d--Hard, no indentation was made on sample of cement.
278
RESULTS
T h e control cement, prepared in the laboratory, had set after one hour at 37 C with 100% relative humidity. All cements mixed with essential oils remained soft after one or 1 V2 hours, with the exception of the cement mixed with oil of pimenta leaf, which set in l lA hours. At two hours, anethole, anise, and eucalyptol were doughy. At three and five hours, they were still either in a doughy stage or were being indented by the modified Gilmore needle. Only cement mixed with eugenol or oil of pimenta leaf had hardened within a reasonable time, namely, one to 11/z hours. The formula of the cement powder was, therefore, modified in an effort to accelerate the setting time of the other cements. Sodium borate, which retards setting time, was omitted from the formula; and bismuth subnitrate,
J O U R N A L OF E N D O D O N T I C S I V O L 8, NO 6, JUNE 1982
which accelerates setting, was substituted for bismuth subcarbonate. This substitution had the effect of accelerating the setting time of the cement made with eugenol, and the cement mixed with oil of pimenta leaf which set in one hour. However, it had little effect on the other oils, which required five or more hours to harden. Tests were performed also with cements mixed according to the formulas previously described at ambient room temperature, 22 C, and in an incubator at 37 C with 100% humidity for purposes of comparison. Those cements kept at room temperature took longer to harden.
DISCUSSION The method of testing the setting time used by Wiener and Schilder ~ was to place a spatula weighing 46 gm on the surface of a cement mix, and if no indentation resulted, the cement was considered set. The size or weight of the cement mass was not given. The masses of cement were assumed to be uniform throughout the experiment, because the greater the mass the longer the setting time. Observations were made at intervals of two minutes to several hours according to the rapidity of setting. To provide a uniform mass of cement, Grossman 2 filled the opening in each Dormann spacer, which has uniform dimensions. Tests for hardness or set of the cement were made with a Gilmore needle, which consists of a pointed rod attached to a 154 gm weight. The needle was placed on the surface of the cement from time to time, and the cement was considered set when the needle left no indentation. Observations were made to 40 hours. Benatti and others 3 used a circular mold, which had a diameter of 20 mm
and a height of 3 mm, to achieve a uniform mass of cement; they tested the setting time by "penetration with needles" from a 50-gin load. However, how often or how long the cements were tested was not discussed. In the current study, the amount of cement mass was uniform, in that it was limited by the Dormann spacers, and a modified Gilmore needle attached to a 100-gm weight was used to determine the setting time of the cements. Observations were made at half-hour intervals to five hours or longer, unless the cement set within an hour, then tests were made at tenminute intervals. In the course of testing the cements, it was observed that they went through four states: soft, this stage was sometimes quite prolonged and would give an indication within the first half hour or hour as to whether the cement would set within a reasonable time or would set slowly; doughy, the cement would cling to the needle and drop off in the initial setting stage; indented, the cement did not follow the needle, and the needle left a crater as it was removed; hard, the needle left no mark on the cement, and the cement felt hard. Cement will harden in the root canal much faster than on a slab because there is less bulk in the root canal; for example, a thin layer of cement in the root canal compared with the 0.8-mm thick test specimen used in this study. Therefore, if too much time elapses in developing a radiograph that shows an overfilled canal, some setting of the cement has already occurred, and considerable resistance may be encountered in removing the gutta-percha cone to make the necessary adjustment. A slow operator may, therefore, prefer a cement that hardens slowly. A cement that hardens within one to 189 hours at
37 C and 100% humidity might be considered satisfactory. A setting time that is too slow may result in a weak cement, especially if the cement is in contact with periapical exudate; whereas a setting time that is too fast would not give the operator enough time to correct the fit of the core in the root canal.
SUMMARY AND CONCLUSIONS The purpose of this study was to determine the setting time of root canal cements composed of anethole, anise, eucalyptol, and oil of pimenta leaf, mixed with a standard root canal cement powder compared with the setting time of a root canal cement with eugenol. It was found that the setting time of a root canal cement made with oil of pimenta leaf was the only one of the four cements tested that compared favorably with a cement containing eugenol. Therefore, oil of pimenta leaf could be considered a substitute for eugenol in a standard root canal cement formula. Dr. Grossman is professor emeritus, School of Dental Medicine, University of Pennsylvania, Philadelphia, 19104.
References 1. Wiener, B.H., and Schilder, H. A comparative study of important physical properties of various root canal sealers. Oral Surg 32:768777, 1971. 2. Grossman, L.I. Physical properties of root canal cements. J Endod 2:166-175, 1976. 3. Benatti, O., Stolf, W.L.; and Ruhnke, L.A. Verification of the consistency, setting time and dimensional changes of root canal filling materials. Oral Surg 46:107-113, 1978. 4. Grossman, L.I., and Lally, E. Assessment of irritation potential of essential oils for root canal cement. J Endod 8~'~) 208-212, 1982, 5. Grossman, L.I. Endodontic practice, ed 10. Lea & Febiger, Philadelphia, 1981, p 297.
279
Setting time of selected essential oils with a standard root canal cement powder L o u i s I. G r o s s m a n , DDS, Dr Med Dent
F o u r e s s e n t i a l oils, w h i c h are b i o l o g i c a l l y less i r r i t a t i n g t h a n e u g e n o l , were mixed with a standard root canal cement powder, and the s e t t i n g t i m e s of t h e s e c e m e n t s w a s d e t e r m i n e d . O f t h e f o u r c e m e n t s tested, o n l y t h e c e m e n t u s i n g oil of p i m e n t a leaf h a d a s e t t i n g t i m e c o m p a r a b l e to t h a t of r o o t c a n a l c e m e n t p o w d e r m i x e d w i t h e u g e n o l .
The setting time of eugenolate root canal cements has been studied by Wiener and Schilder, 1 Grossman, z and Benatti and others? Eugenolate cements are oxides of metals, such as zinc oxide, in corfibination with eugenol. Certain essential oils are less irritating than eugenol, 4 such as anethole, anise, eucalyptol, and pimenta leaf. The purpose of this study was to determine the setting time of root canal cements after each of these oils was combined with a standard root canal cement powder. The formula for the powder s is as follows: zinc oxide, 42 parts; staybelite resin, 27 parts; bismuth subcarbonate, 15 parts; barium sulphate, 15 parts; sodium borate, 1 part; all parts by weight.
MATERIALS AND
METHODS
Dormann spacers have an outside diameter of 16 ram, an inside diameter of 6 mm, and are 0.8 mm thick; the spacers were attached with two pin-
heads of sticky wax to the top surface of plastic petri plates. A comparison had been made of the setting time of the control cement when glass or plastic petri plates were used. No difference was observed. Only two spacers were used on each plate; the spacers were filled with cement, and the plates were immediately placed in an incubator at 37 C, with 100% relative humidity. The control powder for the cement was freshly prepared in a mortar using a pestle and passed through a 100mesh sieve. A quantity of the powder, weighing approximately 0.12 gm, was mixed with 0.07 gm of the essential oil. The powder and eugenol in the prescribed amounts were mixed to form a cement that was used as a control. The powder was incorporated into the essential oil in small amounts on a glass slab 15 X7.5 • 1.5 cm with a stainless steel spatula until the cement mass met the following criteria: resistance was felt to spatulation; half of the cement mix took from 12 to 15 seconds to drop off the spatula as it was held edgewise;
and after the spatula was placed flat against the collected cement mass and was slowly lifted, the cement strung out for at least an inch without breaking. The mixing time took approximately five minutes to thoroughly incorporate the powder into the liquid and to make a smooth cement. The cement was then collected at the tip of the spatula and allowed to drop slowly from the spatula into the opening of the Dormann spacer. Each opening was filled level with the top surface of the spacer, and any excess was removed. The length of time the cement was placed in the spacer opening was recorded. When both spacers were filled with cement, the plate was placed in an incubator at 37 C with 100% relative humidity. No more than two cement mixes were placed on each plate to subject the cement to the predetermined temperature and humidity as soon as possible. The cements were tested for setting time (hardness) every half hour during the first three hours, then hourly for six hours when possible, and observed
277
JOURNAL OF ENDODONTICS JVOL 8, NO 6, JUNE 1982
again the next morning. If the cement was already set at the end of the first hour, observations were made every ten minutes for subsequent mixes. The method of testing included the use of a modified Gilmore needle made by attaching a no. 70 reamer to a 100-gin weight (Fig 1). T h e instrument was held between thumb and finger and lowered into the cement. The setting stages of the cement were recorded according to the following descriptions: soft, the needle met with no resistance; doughy, the needle met with some resistance, but pulled a bit of cement with it as the needle was being withdrawn (Fig 2); indented, the needle, after being pulled out of the cement, left a clean hole (Fig 3); hard, the needle left no mark on the completely hard cement (Fig 4). Eugenol, mixed with the same powder, was used as a control.
Fzg l--Modified Gilmore needle made by attaching 770. 70 reamer to lO0-gm weight for testing setting times of root canal cements.
Fig 2--Stages in setting of root canal cements. Doughy, the cement follows modified Gffmore needle as it is being removed from cement, leaving a hillock above surface of cement.
Fig 3--Indented, Gilmore needle penetrated cement and left clean hollow on removal.
Fig d--Hard, no indentation was made on sample of cement.
278
RESULTS
T h e control cement, prepared in the laboratory, had set after one hour at 37 C with 100% relative humidity. All cements mixed with essential oils remained soft after one or 1 V2 hours, with the exception of the cement mixed with oil of pimenta leaf, which set in l lA hours. At two hours, anethole, anise, and eucalyptol were doughy. At three and five hours, they were still either in a doughy stage or were being indented by the modified Gilmore needle. Only cement mixed with eugenol or oil of pimenta leaf had hardened within a reasonable time, namely, one to 11/z hours. The formula of the cement powder was, therefore, modified in an effort to accelerate the setting time of the other cements. Sodium borate, which retards setting time, was omitted from the formula; and bismuth subnitrate,
J O U R N A L OF E N D O D O N T I C S I V O L 8, NO 6, JUNE 1982
which accelerates setting, was substituted for bismuth subcarbonate. This substitution had the effect of accelerating the setting time of the cement made with eugenol, and the cement mixed with oil of pimenta leaf which set in one hour. However, it had little effect on the other oils, which required five or more hours to harden. Tests were performed also with cements mixed according to the formulas previously described at ambient room temperature, 22 C, and in an incubator at 37 C with 100% humidity for purposes of comparison. Those cements kept at room temperature took longer to harden.
DISCUSSION The method of testing the setting time used by Wiener and Schilder ~ was to place a spatula weighing 46 gm on the surface of a cement mix, and if no indentation resulted, the cement was considered set. The size or weight of the cement mass was not given. The masses of cement were assumed to be uniform throughout the experiment, because the greater the mass the longer the setting time. Observations were made at intervals of two minutes to several hours according to the rapidity of setting. To provide a uniform mass of cement, Grossman 2 filled the opening in each Dormann spacer, which has uniform dimensions. Tests for hardness or set of the cement were made with a Gilmore needle, which consists of a pointed rod attached to a 154 gm weight. The needle was placed on the surface of the cement from time to time, and the cement was considered set when the needle left no indentation. Observations were made to 40 hours. Benatti and others 3 used a circular mold, which had a diameter of 20 mm
and a height of 3 mm, to achieve a uniform mass of cement; they tested the setting time by "penetration with needles" from a 50-gin load. However, how often or how long the cements were tested was not discussed. In the current study, the amount of cement mass was uniform, in that it was limited by the Dormann spacers, and a modified Gilmore needle attached to a 100-gm weight was used to determine the setting time of the cements. Observations were made at half-hour intervals to five hours or longer, unless the cement set within an hour, then tests were made at tenminute intervals. In the course of testing the cements, it was observed that they went through four states: soft, this stage was sometimes quite prolonged and would give an indication within the first half hour or hour as to whether the cement would set within a reasonable time or would set slowly; doughy, the cement would cling to the needle and drop off in the initial setting stage; indented, the cement did not follow the needle, and the needle left a crater as it was removed; hard, the needle left no mark on the cement, and the cement felt hard. Cement will harden in the root canal much faster than on a slab because there is less bulk in the root canal; for example, a thin layer of cement in the root canal compared with the 0.8-mm thick test specimen used in this study. Therefore, if too much time elapses in developing a radiograph that shows an overfilled canal, some setting of the cement has already occurred, and considerable resistance may be encountered in removing the gutta-percha cone to make the necessary adjustment. A slow operator may, therefore, prefer a cement that hardens slowly. A cement that hardens within one to 189 hours at
37 C and 100% humidity might be considered satisfactory. A setting time that is too slow may result in a weak cement, especially if the cement is in contact with periapical exudate; whereas a setting time that is too fast would not give the operator enough time to correct the fit of the core in the root canal.
SUMMARY AND CONCLUSIONS The purpose of this study was to determine the setting time of root canal cements composed of anethole, anise, eucalyptol, and oil of pimenta leaf, mixed with a standard root canal cement powder compared with the setting time of a root canal cement with eugenol. It was found that the setting time of a root canal cement made with oil of pimenta leaf was the only one of the four cements tested that compared favorably with a cement containing eugenol. Therefore, oil of pimenta leaf could be considered a substitute for eugenol in a standard root canal cement formula. Dr. Grossman is professor emeritus, School of Dental Medicine, University of Pennsylvania, Philadelphia, 19104.
References 1. Wiener, B.H., and Schilder, H. A comparative study of important physical properties of various root canal sealers. Oral Surg 32:768777, 1971. 2. Grossman, L.I. Physical properties of root canal cements. J Endod 2:166-175, 1976. 3. Benatti, O., Stolf, W.L.; and Ruhnke, L.A. Verification of the consistency, setting time and dimensional changes of root canal filling materials. Oral Surg 46:107-113, 1978. 4. Grossman, L.I., and Lally, E. Assessment of irritation potential of essential oils for root canal cement. J Endod 8~'~) 208-212, 1982, 5. Grossman, L.I. Endodontic practice, ed 10. Lea & Febiger, Philadelphia, 1981, p 297.
279