Influence of calcium hydroxide intracanal medication on apical seal
http://endodonticsjournal.com/articles/76/1/Influence-of-calcium-hydroxide-intracanal-medication-on-apical-seal/Page1.html
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Published on 07/15/2002
S. K. Kim & Y. O. Kim
Department of Conservative Dentistry, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea.
Aim.
The aim of this study was to determine the influence of calcium hydroxide intracanal medication and various techniques for its removal on the sealing ability of gutta-percha root fillings with a zinc oxide-eugenol sealer.
Conclusion.
Under the condition of this study, calcium hydroxide medicated canals showed significantly more apical dye-leakage than the non-medicated ones.
Department of Conservative Dentistry, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea.
Aim.
The aim of this study was to determine the influence of calcium hydroxide intracanal medication and various techniques for its removal on the sealing ability of gutta-percha root fillings with a zinc oxide-eugenol sealer.
Conclusion.
Under the condition of this study, calcium hydroxide medicated canals showed significantly more apical dye-leakage than the non-medicated ones.
Introduction - Materials and methods.
S. K. Kim & Y. O. Kim
Department of Conservative Dentistry, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea.
Introduction.
Effective cleaning and shaping is the foundation of successful root-canal treatment. However, because of the complexity of root-canal systems, complete cleaning and shaping with presently available irrigants and instruments is difficult. When sufficient bacteria remain within the system, they can proliferate and reinfect the root-canal space (Bystrom & Sundqvist 1981).
Intracanal medication has been advocated to further reduce the number of microorganisms between appointments. A wide range of chemicals have been used to disinfect the root-canal system including formocresol, cresatin, phenolic compounds, aldehydes, antibiotics, steroids, and calcium hydroxide.
Calcium hydroxide has been widely used as an intracanal medicament. Calcium hydroxide should be removed before root-canal filling, however, its complete removal is problematic, and some calcium hydroxide may be retained in the apical area (Guignes et al. 1991, Margelos et al.1997, Lambrianidis et al.1999).
Recently, Margelos et al. (1997) reported a possible problem caused by the interaction between calciumhydroxide and zinc oxide-eugenol sealers. There is a concern that, at the time of root-canal filling, the retention of calciumhydroxide on the canal wall might affect the quality of the seal and influence the prognosis of treatment. A few studies have reported on this problem with inconsistent findings. An apical leakage study (Porkaew et al. 1990) in teeth filled using lateral condensation demonstrated that teeth dressed with calcium hydroxide had significantly less leakage than those not medicated. A further study (Holland et al.1995) supported this finding. However, these studies also noted that when calcium hydroxide dressing was retained in the canal, apical leakage increased with time. Recently, other studies (Kontakiotis et al. 1997, Wu et al. 1998) have described the possibility of false positive results occurring with previous dye-leakage studies using methylene blue dye, because it may loose its colour in contact with calcium hydroxide.
The purpose of this study was to determine the influence of calcium hydroxide intracanal medication, and various techniques for its removal on the apical sealing ability of gutta-percha root fillings when a zinc oxide- eugenol sealer was used.
Materials and methods.
Preparation of specimens.
Eighty extracted multi-rooted human mandibular molars were used. Calculus and soft tissue debris was removed with scalers and each tooth was sectioned vertically with a disc to separate each root. After access cavity preparation, size 10-20 K-files were introduced to determine working lengths and apical foramen sizes.
Three separate roots with similar canal configuration were matched in a set, and 25 sets of roots were selected from 80 teeth; the remaining roots were discarded. The roots in each set were randomly divided into three groups A, B, and C of 25 roots each, so that the three groups had a similar root-canal configuration (Table 1). An additional six roots were used for negative and positive leakage controls.
All the root canals were prepared by one operator. Working lengths were established1mmshort of the apical foramen, and size 10-20 K-files were used as initial apical files (IAF). The coronal one-third was flared with size 4-2 Gates Glidden burs and the apical two-thirds of the canals were instrumented sequentially with size 40-25, 0.06 ProFiles (Dentsply Maillefer, Ballaigues, Switzerland) at a constant speed of 300 r.p.m. in a crown-down manner. The apical region was then enlarged with size 20-30, 0.06 ProFiles until the master apical file (MAF) size was three sizes larger than the size of the IAF. Root canals were irrigated after each instrument, and 5 mL of15% EDTA and 5 mL of 2.5% sodium hypochlorite (NaOCl) solutions were used alternately with a 25-gauge needle.
After removing the temporary coronal restoration, two different techniques were used to remove the calcium hydroxide. In group A, after irrigation with 2.5 mL of 2.5%NaOCland 5.0 mL of15%EDTAsolutions, canals were cleaned to the working length with a K-file one size larger than the MAF size with reaming motion, and step-back preparation was completed up to four sizes larger than the first file (Holland et al.1995). Canals were irrigated again with 2.5 mL of 2.5% NaOCl. In group B, after irrigation with 2.5 mL of 2.5% NaOCl and 5.0 mL of distifilled water, canals were instrumented to the working length with a K-file of MAF size (Margelos et al. 1997). Canals were irrigated again with 2.5 mL of 2.5% NaOCl. In group C, no irrigation or filing was completed.
After the canals were dried with paper points, a zinc oxide-eugenol sealer, Tubli-seal (Kerr, Romulus, MI, USA) was applied and the canals obturated by lateral condensation of gutta-percha (DiaDent1 gutta-percha points, DiaDent Group International Inc., Chongju, Korea) with the exception of three positive leakage controls. Buccolingual and mesiodistal radiographs were taken in order to confirm the root-canal fillings were at length and were dense.
Dye-leakage test.
The access cavity of each root was filled with a lightcuring composite resin (Metafil CX, Sun Medical Co. Ltd., Moriyama, Japan). All the specimens, except the negative leakage controls, were coated with nail varnish on all but a 1-mm area around the apex. Three roots of the negative leakage controls were completely coated with nail varnish. All the roots were suspended on base-plate wax and the apical 3 mm of each was dipped in India ink (Winsor & Newton Ink, London, UK) and incubated at 37 8C and100% humidity for14 days.
Evaluation of apical leakage.
All the specimens were sectioned horizontally at 1,2,3,4, and 5 mm from the root apex with a microtome (Isomet, Buehler, Lake Bluff, IL, USA).
Linear measurements of apical leakage were recorded with a stereomicroscope (SZ40, Olympus Optical Co. Ltd., Tokyo, Japan) to evaluate the dye-penetration depth. The number of specimens with leakage was counted at each section level.
Statistical analysis
Fisher’s exact test was used to determine the difference of the number of specimens at each leakage level amongst the three groups. Duncan’s multiple range test was also adapted for a post hoc test. Correspofinding P-values less than 0.05 were considered significant.
Department of Conservative Dentistry, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea.
Introduction.
Effective cleaning and shaping is the foundation of successful root-canal treatment. However, because of the complexity of root-canal systems, complete cleaning and shaping with presently available irrigants and instruments is difficult. When sufficient bacteria remain within the system, they can proliferate and reinfect the root-canal space (Bystrom & Sundqvist 1981).
Intracanal medication has been advocated to further reduce the number of microorganisms between appointments. A wide range of chemicals have been used to disinfect the root-canal system including formocresol, cresatin, phenolic compounds, aldehydes, antibiotics, steroids, and calcium hydroxide.
Calcium hydroxide has been widely used as an intracanal medicament. Calcium hydroxide should be removed before root-canal filling, however, its complete removal is problematic, and some calcium hydroxide may be retained in the apical area (Guignes et al. 1991, Margelos et al.1997, Lambrianidis et al.1999).
Recently, Margelos et al. (1997) reported a possible problem caused by the interaction between calciumhydroxide and zinc oxide-eugenol sealers. There is a concern that, at the time of root-canal filling, the retention of calciumhydroxide on the canal wall might affect the quality of the seal and influence the prognosis of treatment. A few studies have reported on this problem with inconsistent findings. An apical leakage study (Porkaew et al. 1990) in teeth filled using lateral condensation demonstrated that teeth dressed with calcium hydroxide had significantly less leakage than those not medicated. A further study (Holland et al.1995) supported this finding. However, these studies also noted that when calcium hydroxide dressing was retained in the canal, apical leakage increased with time. Recently, other studies (Kontakiotis et al. 1997, Wu et al. 1998) have described the possibility of false positive results occurring with previous dye-leakage studies using methylene blue dye, because it may loose its colour in contact with calcium hydroxide.
The purpose of this study was to determine the influence of calcium hydroxide intracanal medication, and various techniques for its removal on the apical sealing ability of gutta-percha root fillings when a zinc oxide- eugenol sealer was used.
Materials and methods.
Preparation of specimens.
Eighty extracted multi-rooted human mandibular molars were used. Calculus and soft tissue debris was removed with scalers and each tooth was sectioned vertically with a disc to separate each root. After access cavity preparation, size 10-20 K-files were introduced to determine working lengths and apical foramen sizes.
Three separate roots with similar canal configuration were matched in a set, and 25 sets of roots were selected from 80 teeth; the remaining roots were discarded. The roots in each set were randomly divided into three groups A, B, and C of 25 roots each, so that the three groups had a similar root-canal configuration (Table 1). An additional six roots were used for negative and positive leakage controls.
All the root canals were prepared by one operator. Working lengths were established1mmshort of the apical foramen, and size 10-20 K-files were used as initial apical files (IAF). The coronal one-third was flared with size 4-2 Gates Glidden burs and the apical two-thirds of the canals were instrumented sequentially with size 40-25, 0.06 ProFiles (Dentsply Maillefer, Ballaigues, Switzerland) at a constant speed of 300 r.p.m. in a crown-down manner. The apical region was then enlarged with size 20-30, 0.06 ProFiles until the master apical file (MAF) size was three sizes larger than the size of the IAF. Root canals were irrigated after each instrument, and 5 mL of15% EDTA and 5 mL of 2.5% sodium hypochlorite (NaOCl) solutions were used alternately with a 25-gauge needle.
Table 1. Root-canal configurations of specimens in each group.
After removing the temporary coronal restoration, two different techniques were used to remove the calcium hydroxide. In group A, after irrigation with 2.5 mL of 2.5%NaOCland 5.0 mL of15%EDTAsolutions, canals were cleaned to the working length with a K-file one size larger than the MAF size with reaming motion, and step-back preparation was completed up to four sizes larger than the first file (Holland et al.1995). Canals were irrigated again with 2.5 mL of 2.5% NaOCl. In group B, after irrigation with 2.5 mL of 2.5% NaOCl and 5.0 mL of distifilled water, canals were instrumented to the working length with a K-file of MAF size (Margelos et al. 1997). Canals were irrigated again with 2.5 mL of 2.5% NaOCl. In group C, no irrigation or filing was completed.
After the canals were dried with paper points, a zinc oxide-eugenol sealer, Tubli-seal (Kerr, Romulus, MI, USA) was applied and the canals obturated by lateral condensation of gutta-percha (DiaDent1 gutta-percha points, DiaDent Group International Inc., Chongju, Korea) with the exception of three positive leakage controls. Buccolingual and mesiodistal radiographs were taken in order to confirm the root-canal fillings were at length and were dense.
Dye-leakage test.
The access cavity of each root was filled with a lightcuring composite resin (Metafil CX, Sun Medical Co. Ltd., Moriyama, Japan). All the specimens, except the negative leakage controls, were coated with nail varnish on all but a 1-mm area around the apex. Three roots of the negative leakage controls were completely coated with nail varnish. All the roots were suspended on base-plate wax and the apical 3 mm of each was dipped in India ink (Winsor & Newton Ink, London, UK) and incubated at 37 8C and100% humidity for14 days.
Evaluation of apical leakage.
All the specimens were sectioned horizontally at 1,2,3,4, and 5 mm from the root apex with a microtome (Isomet, Buehler, Lake Bluff, IL, USA).
Linear measurements of apical leakage were recorded with a stereomicroscope (SZ40, Olympus Optical Co. Ltd., Tokyo, Japan) to evaluate the dye-penetration depth. The number of specimens with leakage was counted at each section level.
Statistical analysis
Fisher’s exact test was used to determine the difference of the number of specimens at each leakage level amongst the three groups. Duncan’s multiple range test was also adapted for a post hoc test. Correspofinding P-values less than 0.05 were considered significant.
Results.
Thirty specimens from10 sets that had cracks in one or more of the three roots were excluded from the results.
The number of specimen with leakage at each level is shown in Table 2. Specimens in calciumhydroxide medicated groups A and B, had the greatest frequency of apical leakage at the 2 mm level, whilst group C, the control group, had greatest frequency at1mmlevel. Calciumhydroxide- medicated groups A and B, were shown to induce significantly more apical leakage than the non-medicated control group C (P < 0.05). However, there was no statistical difference between group A, the EDTA and NaOCl irrigation group; and group B, the NaOCl irrigation group.
Calcium hydroxide-medicated canals had sealer of uneven thickness and non-homogenous appearance whilst non-medicated ones had set sealer of relatively even thickness and homogenous appearance (Fig. 1). Microscopic views showed some cracks and voids in the sealer around the gutta-percha canal filling in the calcium hydroxide-medicated groups.
The number of specimen with leakage at each level is shown in Table 2. Specimens in calciumhydroxide medicated groups A and B, had the greatest frequency of apical leakage at the 2 mm level, whilst group C, the control group, had greatest frequency at1mmlevel. Calciumhydroxide- medicated groups A and B, were shown to induce significantly more apical leakage than the non-medicated control group C (P < 0.05). However, there was no statistical difference between group A, the EDTA and NaOCl irrigation group; and group B, the NaOCl irrigation group.
Calcium hydroxide-medicated canals had sealer of uneven thickness and non-homogenous appearance whilst non-medicated ones had set sealer of relatively even thickness and homogenous appearance (Fig. 1). Microscopic views showed some cracks and voids in the sealer around the gutta-percha canal filling in the calcium hydroxide-medicated groups.
Table 2. Number of specimens with leakage at each level.
Figure 1. Stereomicroscopic appearances of specimens.
A: a 3-mm level specimen from group A; 
a 5-mm level specimen from group B;
a 3-mm level specimen from group C.
Specimens from groups A and B show uneven thickness and non-homogenous appearances of set root-canal cement. Root-canal cement (c) between primary gutta-percha cone (p) and canal wall opposite side of secondary cone (s) appears thicker in calciumhydroxide medicated canals (A, B) than in control (C).
Discussion - References.
Discussion.
In the present study, extracted whole mandibular molar roots were used as the experimental model. Because root-canal morphology can affect the application and removal of calciumhydroxide and canal obturation, distribution of roots with each group was made on the basis of root and canal shape.
Because it is difficult to remove calcium hydroxide paste completely from the root canal (Guignes et al. 1991, Margelos et al.1997, Lambrianidis et al.1999), there is a need to determine whether the remaining calcium hydroxide paste has any beneficial or adverse effect on the filling. There have been several studies regarding the influence of remaining calciumhydroxide on the apical seal of root-canal fillings. Porkaew et al. (1990) and Holland et al. (1995) reported that apical leakage was less in teeth that received calcium hydroxide dressings than in non-medicated control teeth. Holland et al. (1995) explained the reduced leakage in calcium hydroxide medicated teeth on the basis that the residual calcium hydroxide was incorporated into the sealer during obturation, which caused a decrease in the permeability of the sealer itself or that calcium hydroxide was transported or mechanically forced into the dentinal tubules, blocking them off and decreasing dentinal permeability. They also suggested that the improved seal with plugs of calcium hydroxide was due to the fact that the plug provides a stop or matrix against which the gutta-percha and sealer may be condensed more effectively.
However, in the present study, calcium hydroxide medicated root canals showed significantly more apical leakage than ones without medication. Because calcium hydroxide cannot be removed completely from the canal, it is likely that the remaining calcium hydroxide may interfere with the sealability of fillings when a zinc oxide-eugenol sealer is used. A number of explanations may account for the difference between the present study and those of Holland et al. (1995). Firstly, it is not likely that a decrease in dentinal permeability will lead to a decrease in apical leakage. Leakage at the apex occurs between the root-canal wall and the sealer, between the sealer and the gutta-percha, or within the sealer itself. In the present apical-leakage study, all the specimens were coated with nail varnish on their root surface to exclude any possible leakage through the dentine surface to leave only apical pathways. Secondly, when calcium hydroxide was mixed with zinc oxide-eugenol sealer, a calcium hydroxide-eugenol compound was reported to be produced, which was more soluble, less sealing had a thicker film-thickness and higher water sorption value than the original sealer (Park et al. 1999). In another study (Park 1999), calcium hydroxide and zinc oxide-eugenol were shown to form calcium eugenolate, or that calcium bonds to eugenol by an ionic bond which can be broken when water is present. These reports imply that, when a zinc oxide-eugenol sealer is used, calcium eugenolate is formed which weakens the sealer in the long term.
Even though there is no reported technique that can remove calcium hydroxide completely from the canal (Lambrianidis et al. 1999), root-canal irrigation with NaOCl and EDTA solutions have given better results than NaOCl alone (Margelos et al. 1997, Calt & Serper 1999). However, in the present study, there was no significant difference in leakage between these two groups. A combined approach to remove calcium hydroxide from the canal with irrigation and an instrumentation demonstrated no difference in the apical seal between K-files one size larger than the MAF, and K-files of the same size as the MAF. Holland et al. (1995) also reported similar results with size 40-70 files.
Calcium hydroxide has been reported to have a decolourizing effect on methylene blue dye (Kontakiotis et al. 1997). Wu et al. (1998) also studied the decolourizing effect of six dental filling materials on1%methylene blue dye, and found that calciumhydroxide had decolourized the dye by 74%. The decolourizing effect of calcium hydroxide is related to it’s high alkalinity and this varies according to its form, that is, paste, cone or sealer (Esberard et al.1996,Wu et al.1998, Calt et al.1999, Economides et al. 1999). On the contrary, India ink was not shown to be decolourized by calcium hydroxide (Caliskan et al. 1998). This might be one of the possible explanations for the results of the present study using India ink being different from previous studies with methylene blue (Porkaew et al.1990, Holland et al.1995).
India ink particles are known to be much larger than methylene blue, but are still small enough to penetrate cracks within root-canal sealers (Yoshikawa et al. 1997). Ahlberg et al. (1995) compared linear leakage patterns of methylene blue and India ink, and showed that methylene blue penetrated more deeply and with more variance. This penetration-depth difference between methylene blue dye and India ink might be another possible explanation for differences between the present study using India ink and previous studies using methylene blue.
In the present study, the set sealer showed relatively uneven thickness, some cracks and voids in the calcium hydroxide-medicated canals. These appearances are in agreement with other studies (Margelos et al.1997, Park et al.1999) and can be explained by the report (Margelos et al. 1997) that a faster setting of sealer prevented full sealing of gutta-percha, and this may be related to the thicker appearance of the sealer in the present study. The present appearance of a thicker sealer is also in accordance with the finding of Calt & Serper (1999) that when calcium hydroxide was left on the root-canal surface, the sealer could not penetrate into dentinal tubules.
In the present study, extracted whole mandibular molar roots were used as the experimental model. Because root-canal morphology can affect the application and removal of calciumhydroxide and canal obturation, distribution of roots with each group was made on the basis of root and canal shape.
Because it is difficult to remove calcium hydroxide paste completely from the root canal (Guignes et al. 1991, Margelos et al.1997, Lambrianidis et al.1999), there is a need to determine whether the remaining calcium hydroxide paste has any beneficial or adverse effect on the filling. There have been several studies regarding the influence of remaining calciumhydroxide on the apical seal of root-canal fillings. Porkaew et al. (1990) and Holland et al. (1995) reported that apical leakage was less in teeth that received calcium hydroxide dressings than in non-medicated control teeth. Holland et al. (1995) explained the reduced leakage in calcium hydroxide medicated teeth on the basis that the residual calcium hydroxide was incorporated into the sealer during obturation, which caused a decrease in the permeability of the sealer itself or that calcium hydroxide was transported or mechanically forced into the dentinal tubules, blocking them off and decreasing dentinal permeability. They also suggested that the improved seal with plugs of calcium hydroxide was due to the fact that the plug provides a stop or matrix against which the gutta-percha and sealer may be condensed more effectively.
However, in the present study, calcium hydroxide medicated root canals showed significantly more apical leakage than ones without medication. Because calcium hydroxide cannot be removed completely from the canal, it is likely that the remaining calcium hydroxide may interfere with the sealability of fillings when a zinc oxide-eugenol sealer is used. A number of explanations may account for the difference between the present study and those of Holland et al. (1995). Firstly, it is not likely that a decrease in dentinal permeability will lead to a decrease in apical leakage. Leakage at the apex occurs between the root-canal wall and the sealer, between the sealer and the gutta-percha, or within the sealer itself. In the present apical-leakage study, all the specimens were coated with nail varnish on their root surface to exclude any possible leakage through the dentine surface to leave only apical pathways. Secondly, when calcium hydroxide was mixed with zinc oxide-eugenol sealer, a calcium hydroxide-eugenol compound was reported to be produced, which was more soluble, less sealing had a thicker film-thickness and higher water sorption value than the original sealer (Park et al. 1999). In another study (Park 1999), calcium hydroxide and zinc oxide-eugenol were shown to form calcium eugenolate, or that calcium bonds to eugenol by an ionic bond which can be broken when water is present. These reports imply that, when a zinc oxide-eugenol sealer is used, calcium eugenolate is formed which weakens the sealer in the long term.
Even though there is no reported technique that can remove calcium hydroxide completely from the canal (Lambrianidis et al. 1999), root-canal irrigation with NaOCl and EDTA solutions have given better results than NaOCl alone (Margelos et al. 1997, Calt & Serper 1999). However, in the present study, there was no significant difference in leakage between these two groups. A combined approach to remove calcium hydroxide from the canal with irrigation and an instrumentation demonstrated no difference in the apical seal between K-files one size larger than the MAF, and K-files of the same size as the MAF. Holland et al. (1995) also reported similar results with size 40-70 files.
Calcium hydroxide has been reported to have a decolourizing effect on methylene blue dye (Kontakiotis et al. 1997). Wu et al. (1998) also studied the decolourizing effect of six dental filling materials on1%methylene blue dye, and found that calciumhydroxide had decolourized the dye by 74%. The decolourizing effect of calcium hydroxide is related to it’s high alkalinity and this varies according to its form, that is, paste, cone or sealer (Esberard et al.1996,Wu et al.1998, Calt et al.1999, Economides et al. 1999). On the contrary, India ink was not shown to be decolourized by calcium hydroxide (Caliskan et al. 1998). This might be one of the possible explanations for the results of the present study using India ink being different from previous studies with methylene blue (Porkaew et al.1990, Holland et al.1995).
India ink particles are known to be much larger than methylene blue, but are still small enough to penetrate cracks within root-canal sealers (Yoshikawa et al. 1997). Ahlberg et al. (1995) compared linear leakage patterns of methylene blue and India ink, and showed that methylene blue penetrated more deeply and with more variance. This penetration-depth difference between methylene blue dye and India ink might be another possible explanation for differences between the present study using India ink and previous studies using methylene blue.
In the present study, the set sealer showed relatively uneven thickness, some cracks and voids in the calcium hydroxide-medicated canals. These appearances are in agreement with other studies (Margelos et al.1997, Park et al.1999) and can be explained by the report (Margelos et al. 1997) that a faster setting of sealer prevented full sealing of gutta-percha, and this may be related to the thicker appearance of the sealer in the present study. The present appearance of a thicker sealer is also in accordance with the finding of Calt & Serper (1999) that when calcium hydroxide was left on the root-canal surface, the sealer could not penetrate into dentinal tubules.
References.
Ahlberg KMF, Assavanop P,Tay WM (1995) A comparison of the apical dye penetration patterns shown by methylene blue and India ink in root filled teeth. International Endodontic Journal 28, 30-4.
Bystrom A, Sundqvist G (1981) Bacteriologic evaluation of the efficacy of mechanical root canal instrumentation in endodontic therapy. Scandinavian Journal of Dental Research 89, 321-8.
Caliskan MK, Turkun L, Turkun LS (1998) Effect of calcium hydroxide as an intracanal dressing on apical leakage. International Endodontic Journal 31, 173-7.
Calt S, Serper A (1999) Dentinal tubule penetration of root canal sealers after root canal dressing with calcium hydroxide. Journal of Endodontics 25, 431-3.
Calt S, Serper A, Ozcelik B, Dalat MD (1999) pH changes and calcium ion diffusion from calcium hydroxide dressing materials through root dentin. Journal of Endodontics 25, 329-31.
Economides N, Koulaouzidou EA, Beltes P, Kortsaris AH (1999) In vitro release of hydroxyl ions from calcium hydroxide gutta-percha points. Journal of Endodontics 25, 481-2.
Esberard RM, Carnes DL, del Rio CE (1996) pH changes at the surface of root dentin when using root canal sealers containing calcium hydroxide. Journal of Endodontics 22, 399-401.
Guignes P, Brunel F, MauretteA (1991) Removal of two calcium hydroxide preparations: S.E.M. study. Review of French Endodontics 10 (4), 29-35.
Holland R, AlexandreAC, Murata SS, Dos Santos CA, Junior ED (1995) Apical leakage following root canal dressing with calcium hydroxide. Endodontics and Dental Traumatology 11, 261-3.
Kontakiotis EG,Wu M-K,Wesselink PR (1997) Effect of calcium hydroxide dressing on seal of permanent root filling. Endodontics and Dental Traumatology13, 281-4.
Lambrianidis T, Margelos J, Beltes P (1999) Removal efficiency of calcium hydroxide dressing from the root canal. Journal of Endodontics 25, 85-8.
Margelos J, Eliades G, Verdelis C, Palaghias G (1997) Interaction of calcium hydroxide with zinc oxide-eugenol type sealers: a potential clinical problem. Journal of Endodontics 23, 43-8.
Park JC, Kwon TK, Kim SK (1999) Properties of calcium hydroxide- eugenol compound. Journal of Korean Academy of Conservative Dentistry 24, 408-15.
Park SH (1999) Chemical Investigation on The Reaction Between Calcium Hydroxide Medicament and Zinc Oxide-Eugenol, PhD Thesis. Daegu, Korea: Kyungpook National University.
Porkaew P, Retief DH, Bareld RD, Lace?field WR, Soong S (1990) Effects of calcium hydroxide paste as an intracanal medicament on apical seal. Journal of Endodontics 16, 369-74.
WuM-K, Kontakiotis EG, Wesselink PR (1998) Decoloration of 1% methylene blue solution in contact with dental filling materials. Journal of Dentistry 26, 585-9.
Yoshikawa M, Noguchi K, Toda T (1997) Effect of particle sizes in india inkon it suse in evaluation of apical seal. Journal of Osaka Dental University 31, 67-70.