| Abstract|| |
Aim: To determine the time required for the recontamination of root canals medicated with four different materials.
Materials and Methods: A total of 60 intact, caries-free, human single-rooted teeth with straight roots were selected for this study. After chemo-mechanical preparation they must be changed in the specimens into seven groups: 10 teeth medicated with calcium hydroxide (Ca(OH) 2) + Camphorated paramonochlorophanol (CPMC) (G.1); 10 medicated with 2.5% Sodium hypochlorite (NaOCL) (G.2); 10 medicated with 2% Chlorhexidine gluconate (CHX) in gel (G.3); 10 medicated with 2% CHX in gel + Ca(OH) 2 (G.4); 10 without intracanal medicament and sealed with a coronal temporary filling (G.5). Five teeth were without intracanal medicament and coronally unsealed, used as the positive control group (PC) (G.6) and 5 teeth with intact crowns used as the negative control group (NC) (G.7). Glass vials with rubber stoppers were adjusted for use. The medicaments were prepared and injected into the root canals using sterile plastic syringes. An apparatus was used to evaluate for 30 days leakage. The chamber was filled with 3 ml of human saliva and Brain Heart Infusion (BHI) broth, incubated at 37°C and checked daily for the appearance of turbidity in the BHI broth.
Results: Recontamination was detected after an average time of 2.6 days in group 2, 15.9 days in group 3, 30 days in group 1, 27.6 days in group 4, 2.9 days in group 5, 1 day in the positive control, and there was no contamination in the negative control group.
Conclusion : The NaOCl group showed the highest worst average of recontamination; on the other hand, high averages were also shown by Ca(OH) 2 + CPMC and Ca(OH) 2 + 2% CHX in gel.
Keywords: Coronal leakage, coronal temporary filling, intracanal medications
|How to cite this article:|
Verissimo RD, Gurgel-Filho ED, De-Deus G, Coutinho-Filho T, de Souza-Filho FJ. Coronal leakage of four intracanal medications after exposure to human saliva in the presence of a temporary filling material. Indian J Dent Res 2010;21:35-9
Bacteria and their products are considered to be the primary etiological agents of pulpal necrosis and periapical lesions.  The main of root canal treatment is to eliminate the bacteria from an infected root canal and prevent reinfection. Cleaning, shaping, and irrigating the root canal greatly reduces the number of bacteria, allowing the organism to repair the lesion.  The remaining bacteria may multiply between appointments often reaching the same level that was observed at the beginning of treatment, in cases where the canal is not dressed with an antimicrobial agent between visits.  Thus, the use of an effective intracanal medication may assist in the disinfection of the root canal system. 
|How to cite this URL:|
Verissimo RD, Gurgel-Filho ED, De-Deus G, Coutinho-Filho T, de Souza-Filho FJ. Coronal leakage of four intracanal medications after exposure to human saliva in the presence of a temporary filling material. Indian J Dent Res [serial online] 2010 [cited 2019 Dec 10];21:35-9. Available from: http://www.ijdr.in/text.asp?2010/21/1/35/62808
Calcium hydroxide [Ca(OH) 2] has many properties of an ideal root canal dressing, and has become popular because of its antimicrobial properties. , In addition to acting as a physical barrier, a Ca(OH) 2 dressing may both prevent root canal reinfection and interrupt the nutrient supply to the remaining bacteria. Its high pH (12.5) has a destructive effect on cell membranes and protein structure. 
Sodium hypochlorite (NaOCl) has become the most popular agent for endodontic irrigation. It provides good tissue solvent action, and has a broad spectrum of antimicrobial activity. It also acts as a lubricant for instrumentation and can flush loose debris from root canals.  Its use has been suggested as an intracanal medication between appointments. ,,
Chlorhexidine gluconate (CHX) is a cationic bisguanin that has been widely used in dentistry as an antimicrobial rinse in periodontics and as an effective irrigant in endodontics. ,,,,
The association of CHX and Ca(OH) 2 has occurred to enhance the antimicrobial effectiveness of both, particularly against resistant microorganisms such as Enterococcus faecalis. 
The camphorated paramonochlorophanol (CPMC) is a phenolic compound widely used in endodontics and has a strong antibacterial effect in vitro. 
During root canal treatment, it is important to create a seal in the access cavity in order to prevent the entrance of saliva and microorganisms into the root canal system. ,
The aim of this in vitro study was to determine the time required for the recontamination of coronally sealed canals medicated with Ca(OH) 2 + CPMC, NaOCl, CHX in gel or CHX in gel + Ca(OH) 2 and the application of a coronal temporary filling.
| Materials and Methods|| |
Sixty intact, caries-free, human single-rooted teeth with straight roots were selected for this study. Conventional access was prepared in 55 teeth, and the coronal two-thirds of the canals were prepared using files up to size 25.
The specimens were then flared with a size 4 Gates-Glidden bur (Dentsply Maillefer, Ballaigues, Switzerland), followed by a size 3 and 2. A size 10 K-file (Dentsply Maillefer, Ballaigues, Switzerland) was introduced into each canal until it appeared at the apical foramen.
The working length was confirmed by subtracting 1 mm from this measurement. The same K-file was used to recapitulate the canal 1mm beyond its length between each file in order to preserve patency.
The root canals were prepared using the step-back technique with K-files. To standardize the diameter, the apical foramen was enlarged to a size 20 K-file.  Apical preparation was performed at the working length up to a size 40 K-file. Irrigation was carried out using 1 ml of a 2.5% NaOCl (Biodinamica, Ibipora, PR, Brazil) solution between files.
After preparation, the root canal was prepared with 17% EDTA (EDTA Trissodico, Biodinanima, Ibipora, PR, Brazil) for 3 minutes to remove the smear layer, and then with 1 ml 2.5% NaOCl.  5 ml of sterile saline were used as a final rinse to remove debris and the irrigants. After that, the root canals were dried with paper points.
The teeth were randomly divided according to the intracanal medication and coronal seal (Citodur, Dorident, Petropolis, RJ, Brazil), as follows:
The apparatus used to evaluate leakage was prepared as previously described by Siqueira et al.  [Figure 1]. Glass vials with rubber stoppers were adjusted for use. Using a high-speed handpiece, a hole was made through the centre of each rubber stopper in which each tooth was inserted under pressure up to its cemento-enamel junction, so that its crown was outside the vial and its root was within.
- Group 1: 10 teeth with Ca(OH) 2 + CPMC (Calen paste, SS White, Rio de Janeiro, RJ, Brazil) + cotton pellet + Citodur®.
- Group 2: 10 teeth with 2.5% NaOCl (Biodinamica, Ibipora, PR, Brazil) + cotton pellet + Citodur®.
- Group 3: 10 teeth with 2% CHX in gel (Endogel® , Itapetininga, SP, Brazil) + cotton pellet + Citodur®.
- Group 4: 10 teeth with Ca(OH) 2 (Biodinamica, Ibipora, PR, Brazil) (+2% CHX in gel (Endogel® ) (1:1) + cotton pellet + Citodur®.
- Group 5: 10 teeth without intracanal medicament + cotton pellet + Citodur®.
- Group 6: 5 teeth used as the positive control group (PC), without intra canal medicament and coronally unsealed.
- Group 7: 5 teeth used as the negative control group (NC), with intact crowns.
The flasks, the stoppers and the teeth were separately autoclaved at 121°C for 20 minutes and then adapted.  The flasks were filled with BHI broth (BHI, Oxoid, Basingstoke, UK).
The medicaments were prepared and injected into the root canals using sterile plastic syringes with 20 x 5.5 needles. The Calen® paste was injected with the manufacturer supplied syringes and a high needle (27G½" Becton Dickinson, Juiz de Fora, MG, Brazil). The depth of the cavity was approximately 4 mm from the canal orifice to the cavosurface margin. 
Cylinders prepared from 20 ml plastic syringes were adapted to the outer surface of the stoppers to create a chamber around the crown of the teeth.
Cyanocrylate and an epoxy adhesive were then applied to the interface between the tooth and the stopper and between the flask and the stopper to avoid saliva penetration into the BHI broth.
The teeth from groups 1-5 had their coronal access filled with Citodur® , a premixed zinc-oxide-based coronal temporary filling, in order to avoid saliva penetration into the canals.
Human saliva (20 ml) was collected from one individual at 9 am every three days. The volunteer did not brush or floss for at least 12 hours before collection. The chamber of each apparatus was filled with 3 ml of human saliva and BHI broth in a 1:3 proportion. The mixture was replaced every three days. The teeth were exposed for 30 days to the saliva penetration. The set time for samples preparations was approximately 1 hour for each one apparatus.
The whole apparatus was incubated at 37°C and checked daily for the appearance of turbidity in the BHI broth [Figure 2].
Leakage data were analyzed with qualitative statistics using categorical outcomes. The mean day of leakage for each preparation was estimated. Non-parametric Kaplan- Meier survival curves were constructed based on the leaking specimens over the experimental time. Leak-proof specimens were computed with an event time of 30 days as censored variables. Leakage survival was compared using the log-rank test (P < 0.05).
| Results|| |
Kaplan-Meyer curves [Figure 3] showed statistically significant differences among the groups (P < 0.0001).
All specimens of the positive control (PC) showed broth turbidity within 1 day of incubation. On the other hand, there was no evidence of broth turbidity in the negative control (NC) throughout the experiment.
The group 2 showed leakage after 2.6 days (SD = 0.51); G.3 after 15.9 days (SD = 10.4); G.1 after 30 days (SD = 0); G.4 after 27.6 days (SD = 6.9) and the group 5 showed recontamination after an average time of 2.9 days (SD = 0.31).
There was no statistically significant difference between group 2 and group 5 (P > 0.05), indicating no difference between canals medicated with 2.5% NaOCl or nothing. Additionally, the coronal temporary filling Citodur by itself did not prevent leakage of microorganisms as there was no statistically significant difference between the G. 5 and the positive control group (P > 0.05).
There was no statistically significant difference between group 3, 1 and 4 (P > 0.005), although 2% CHX in gel recontaminated more quickly than the other two intracanal medications.
| Discussion|| |
Leakage studies using bacterial cultures or saliva have been widely used to test intracanal medication. ,,, This method have a more biological and clinical relevance than the dye leakage test.  The results observed in the dye leakage methodology have been questioned.  Molecules of dye have a low molecular weight and can penetrate in sites where bacterial cells cannot.  Human saliva has more advantages when compared with bacterial cultures. It has several different bacterial species, high bacterial density and bacterial products. Natural saliva has enzymes and proteins not provided by culture media and dye leakage test. The saliva leakage test is a method close to the real clinical situation. 
The autoclave does not damage the experimental samples so there was no evidence of broth turbidity in the negative control. The same results was observed in others studies using the same method. ,
The apical foramen was enlarged to a size 20 K-file. , This apical enlargement allows a possibility to exclude teeth with blocked apical foramen and makes a uniform diameter to the bacterial progression to the BHI broth.
When an antimicrobial agent is not used between visits, bacteria may multiply inside the root canal, potentially reaching the same level of bacteria that was present at the beginning of the previous sessions.  To be an efficient antimicrobial agent, it has to be active between appointments, not losing its antimicrobial activity. 
It is important to seal the root canal access during the endodontic treatment to prevent the entrance of saliva into the root canal space. Studies have been done to determine the effectiveness of several materials as barriers to coronal leakage. ,,
Among the medicaments evaluated in this study, NaOCl showed the worst performance (recontaminated within an average of 2.6 days). This preparation has a good and fast antimicrobial activity, but it becomes ineffective in the root canal within a short period of time, loosing its antimicrobial activity, which could explain the same results observed in the group with no medication. Therefore, it is not a good choice to use NaOCl as an intracanal medicament, although its use has been suggested in the cases of partially prepared canals. ,
The use of 2% CHX in gel has been suggested as another option in the cases of partially prepared teeth.  In this study, the group 3 showed recontamination within an average of 15.9 days. This can be explained by its wide spectrum of antimicrobial activity with prolonged action (substantivity). It acts not only in the moment that it is used, but it has a prolonged action. , Its gel formulation is another advantage, because its viscosity maintains it in contact with the canal walls and offers resistance to bacterial penetration. [3,5]
Calcium hydroxide has been widely used in endodontic preparations associated with CHX and CPMC. These may be added to improve the physicochemical properties or antibacterial action of calcium hydroxide. 
The methodology used in the current study was the same used in previous studies. ,, Gomes et al.  evaluated the time required for recontamination of coronally sealed canals medicated with either calcium hydroxide, 2% CHX in gel or with a combination of both. The canals medicated with Ca(OH) 2 + IRM showed recontamination within 17.2 days versus 30 days observed in current study when associated with CPMC. The combination of CPMC with Ca(OH 2 ) increases the antibacterial spectrum of action than calcium hydroxide alone  which supported our results. The group with 2% CHX + IRM showed recontamination after 13.5 versus 15.9 days in the current study, while the group with CHX + Ca(OH) 2 + IRM showed contamination after 11.9 days versus 27.6 days in the current study. The group with no medication, but sealed with IRM, showed recontamination after an average of 8.7 days versus 2.9 days in the former versus the current studies, respectively.
In this present study, the average times of recontamination were better when compared with the study of Gomes et al.  The choice of the coronal temporary filling might have contributed to this.
During tooth sterilization, some specimens were crunched and cleaved. These teeth were excluded and replaced. The presence of detected fissures was not the cause of the bad performance in groups without medication and with 2.5% NaOCl.
The present results are not in accordance with an earlier study by Siqueira et al.  They instead of those authors evaluated the time required for bacteria from human saliva to penetrate and thoroughly recontaminate coronally unsealed root canals medicated with CPMC and showed entire recontamination within an average of 6.9 days. Canals filled with calcium hydroxide/saline paste were entirely recontaminated within an average of 14.7 days and the group in which the root canals were filled with Ca(OH) 2 / CPMC/glycerin paste recontaminated within an average of 16.5 days.
The group medicated with only CPMC showed an average time of recontamination after 6.9 days, indicating a high volatility of the material, so that, when it is applied on a cotton pellet in the pulp chamber, it is lost after approximately 24 hours. , Therefore, the use of volatile phenolic compounds applied on cotton pellets in the pulp chamber becomes questionable. 
The apparatus used in this study is a limited static model that does not simulate some conditions found in the oral cavity, such as temperature changes, diet influences and salivary flow. Thus, direct extrapolation of the results to the clinical situation must be done with caution.
| Conclusion|| |
From this study, it may be concluded that:
- The material used for the coronal seal did not prevent the leakage.
- 2.5% NaOCl showed the worst performance when used as an intracanal medicament.
- The longest time of coronal recontamination were presented in the groups: Ca (OH) 2 + CPMC, Ca(OH) 2 + 2% CHX and 2% CHX, with these followings averages: 30, 27.6, and 15.9 days.
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Eduardo Diogo Gurgel-Filho
Department of Endodontics, University of Fortaleza, UNIFOR, Fortaleza
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3]