Antimicrobial Effect of Nano-Calcium Hydroxide on the Four- and Six-Week-Old Intra-Canal Enterococcus Faecalis Biofilm.

Statement of the Problem: Enterococcus faecalis (E. faecalis) is one of the most important microorganisms in the evaluation of the antibacterial effects of intra-canal medications due to its ability to penetrate dentinal tubules and form biofilms. Calcium hydroxide, as the most common intra-canal medication, has little effect on this bacterial species. In contrast, it is hypothesized that nano scale hydroxide particles are more effective due to their smaller size and higher surface-to-volume ratio. Purpose: This study aimed to investigate the antimicrobial effect of nano-calcium hydroxide on the four- and six-week-old intra-canal E. faecalis biofilms. Materials and Method: In this in vitro study, seventy maxillary single-canal premolar teeth were used. After cleaning and preparing the root canals, the samples were placed in vials containing E. faecalis solution in which the culture medium was changed daily. Each group was divided into three subgroups (n=20) in terms of the antimicrobial material used as the intra-canal medication including subgroup 1: nano-calcium hydroxide, subgroup 2: calcium hydroxide, and subgroup 3: phosphate-buffered saline solution (control group). The antimicrobial property was measured by counting colony-forming units (CFU). The data were analyzed with Mann-Whitney U and Kruskal-Wallis tests. Statistical significance was set at p< 0.05. Results: The mean CFU in the six-week-old biofilm group was significantly higher than that in the four-week-old biofilm (p= 0.003). A comparison between the subgroups showed a significant decrease in CFU in the six-week-old biofilm in the nano-calcium hydroxide subgroup compared to that in the calcium hydroxide subgroup (p= 0.002). However, the decrease was not significant in the four-week-old biofilm group (p= 0.06). Conclusion: Under the limitations of the present study, the antimicrobial properties of nano-calcium hydroxide were higher than conventional calcium hydroxide on mature biofilm, whereas the antimicrobial properties were not clinically and significantly different on immature biofilm.

Effects of Different Powder to liquid Ratios on the Push out Bond Strength of CEM Cement on Simulated Perforations in the Furcal Area.

BACKGROUND: Proper bond strength to dentin is one of the properties of biomaterials used for therapeutic purposes such as repair of furcal perforations. The aim of the present study to evaluate the effects of different powder to liquid ratios of Calcium-enriched mixture (CEM) on the push-out bond strengths in simulated perforations in the furcal area and compare it with Mineral trioxide aggregate (MTA). MATERIAL AND METHODS: Furcal perforations, measuring 1.3 mm in diameter and 2 mm in height, were prepared in 120 mandibular first molars. Then the samples were randomly assigned to two groups (n=60). MTA and CEM cement were used for the repair of perforations in groups 1 and 2, respectively. Each group was divided into 3 subgroups based on the powder to liquid rations as follows: subgroup 1 (W/P) , 1:2; subgroup 2, 1:3; and subgroup 3, 1:4. After mixing and placing the materials in the perforation area, the samples were placed in closed containers at 37°C and 100% relative humidity for one week. A universal testing machine was used to determine the bond strength values. After recording the standard deviations, data were analyzed with two-way ANOVA. Statistical significance was set at P<0.05. RESULTS: In the MTA and CEM groups the highest push-out bond strength values were recorded in the third (W/P: 1:4) and first (W/P: 1:2) subgroups, respectively. There were significant differences in both groups between the ratios mentioned above and the other ratios (P<0.05). CONCLUSIONS: Under the limitations of the present study, an increase in the powder-to-liquid ratio in CEM cement resulted in a decrease in bond strength, contrary to MTA. Key words:CEM, Perforation, Powder-to-liquid ratio, push-out bond strength, MTA.

Effects of different intra canal medicaments on the push out bond strength of endodontic sealers.

BACKGROUND: One of the essential properties of the root canal sealers is the adhesion to root canal dentin and their higher bond strength decreases the microleakage. The aim of the present study was to compare the effect of Different Intracanal medicaments on the push out bond strength of AH26 and MTA Fillapex sealers. MATERIAL AND METHODS: A total of 104 one-rooted extracted human teeth were divided into 4 (n=26) experimental groups. After the cleaning and shaping, the root canals were filled with Ca(OH)2, triantibiotic paste (TAP), Metapex or 2% chlorhexidine gel for two weeks. Then, intracanal medicaments were rinsed away and the samples in the sub-groups were obturated with gutta-percha and AH26 or MTA Fillapex sealers. After two weeks incubation, 2-mm-thick middle section of each root was then subjected to push-out testing. Data were analyzed with two-way ANOVA and LSD test. RESULTS: With all the intracanal medicaments, the overall mean of bond strength values were significantly higher with AH26 compared to MTA Fillapex (p<0.05). With the use of MTA Fillapex the maximum and minimum means of bond strength values were recorded with CHX and Metapex and for AH26 were recorded with Ca(OH)2 and chlorhexidine, respectively. CONCLUSIONS: The bond strengths of sealers to dentin are under the influence of pre-treatment with intracanal medicaments. Under the limitations of the present study, the effect of TAP on the bond strength of endodontic sealers was not negative. Key words:AH26, medicament, MTA Fillapex, push-out bond.

Smear layer removal evaluation of different protocol of Bio Race file and XP- endo Finisher file in corporation with EDTA 17% and NaOCl.

BACKGROUND: The aim of the present study was to compare the amount of the smear layer remaining in prepared root canals with different protocols of Bio RaCe files and XP-endo Finisher file (XPF) in association with 17% EDTA and sodium hypochlorite solution. MATERIAL AND METHODS: A total of 68 extracted single-rooted teeth were randomly divided into 4 experimental groups (n=14) and two control groups (n=6). The root canals were prepared with Bio RaCe files (FKG Dentaire, Switzerland) using the crown-down technique based on manufacturer's instructions and irrigated according to the following irrigation techniques: Group 1: XPF with 2 mL of 2.5% NaOCl for 1 minute. Group 2:, XPF with 1 mL of 17% EDTA for one minute. Group 3: XPF was used for 1 minute in association with normal saline solution. Group 4: XP-endo Finisher file for 30 seconds in association with 2.5% NaOCl and 17% EDTA for 30 seconds. The negative control group: NaOCl (2.5%) was used during root canal preparation, followed by irrigation with 17% EDTA at the end of root canal preparation. The positive control group: Normal saline solution was used for irrigation during root canal preparation. In all the groups, during preparation of the root canals with Bio RaCe file, 20 mL of 2.5% NaOCl was used for root canal irrigation and at the end of the procedural steps 20 mL of normal saline solution was used as a final irrigant. The samples were analyzed under SEM at ×1000‒2000 magnification and evaluated using Torabinejad scoring system. Data were analyzed with non-parametric Kruskal-Wallis test and post hoc Mann-Whitney U test, using SPSS. Statistical significant was defined at P<0.05. RESULTS: The results of the study showed the least amount of the smear layer at coronal, middle and apical thirds of the root canals in groups 2, which was not significantly different from the negative control group (P<0.5). CONCLUSIONS: Under the limitations of the present study, use of a combination of NaOCl and EDTA in association with XPF exhibited the best efficacy for the removal of the smear layer. Key words:Smear layer, XP-endo Finisher file, EDTA, Sodium hypochlorite.

Comparing the Coronal Seal of Different Thicknesses of MTA with Gutta-Percha after Post Space Preparation.

INTRODUCTION: The aim of this study was to compare the coronal seal of different thicknesses of MTA with gutta-percha after post space preparation. MATERIALS AND METHODS: A total of 50 maxillary central incisors randomly divided into 5 experimental groups (n = 8). After preparation of the root canals with step back technique, in groups 1 and 2, post spaces were prepared and 4 or 5 mm gutta-percha remained in the apical, respectively. In groups 3, 4, and 5, there was 1-2 and 3 mm MTA in the apical, respectively. The ten teeth serve as control groups. The teeth were connected to a bacterial microleakage evaluation system. The study period was 120 days and the samples were evaluated on ten-day intervals; Meier-Kaplan technique was used for estimation of the mean time of microleakage to occur. Log-rank test was used for comparison of microleakage. RESULTS: Number of samples exhibiting microleakage in MTA was less than those of gutta-percha at all intervals. Means of days with no microleakage were maximum and minimum with 3 mm MTA and 4 mm gutta-percha, respectively. CONCLUSION: Obturation of root canals using the MTA technique provides a proper seal with the minimum thickness of MTA in teeth requiring post space preparation.

Evaluation of apical leakage in root canals obturated with three different sealers in presence or absence of smear layer.

INTRODUCTION: Microleakage can result in failure of endodontic treatment. An important characteristic of endodontic sealer is sealing ability. The aim of this experimental study was to compare the apical leakage of teeth obturated with gutta-percha and three different sealers (resin- and zinc oxide eugenol-based) with/without smear layer (SL). MATERIALS AND METHODS: In this study, 100 single-rooted teeth were used after cutting off their crowns. Cleaning and shaping was carried out with step-back technique and the samples were randomly divided into three groups (n=30) which were then divided into two subgroups (n=15) according to the presence/absence of SL. Two negative and positive control groups (n=5) were also prepared. In the various groups, the canals were obturated with gutta-percha and either of the test sealers (AH-26, Adseal or Endofill). The samples were submerged in India ink for 72 h. Then they were longitudinally sectioned and observed under a stereomicroscope at 20× magnification. Data were analyzed with descriptive statistical methods and one-way ANOVA. The significance level was set at 0.05. RESULTS: The mean penetration length of dye in AH-26, Adseal and Endofill samples were 2.53, 2.76 and 3.03 mm, respectively. The differences between three groups were not significant (P>0.05); also, the mean dye penetration in AH-26, Adseal and Endofill samples in presence or absence of the SL was not significantly different. CONCLUSION: AH-26, Adseal and Endofill were similarly effective in prevention of apical microleakage. Differences in the mean dye penetration between the groups with/without the SL were not statistically significant.

Root canal therapy of a mandibular first molar with five root canals: a case report.

A mandibular first molar requiring root canal therapy was found with five canals, three mesial canals, and two distal canals. Initially, four canals (mesiobuccal, mesiolingual, distobuccal, and distolingual) were identified. The mesiobuccal and mesiolingual canals were found in their normal locations, and a fifth canal was noted between these two. This case demonstrates a rare anatomical configuration and supplements previous reports of the existence of such configurations in mandibular first molars.