Effect of continuous vs sequential chelation on the mechanical properties of root dentin: An ex vivo study.

OBJECTIVES: To evaluate the mechanical properties of root canal dentin treated with sodium hypochlorite (NaOCl) in combination with hydroxyethylidene diphosphonic acid (HEDP) or ethylenediaminetetraacetic acid (EDTA). METHODS: For testing fracture resistance, 45 single-rooted teeth were instrumented and irrigated with NaOCl/HEDP, NaOCl/EDTA, or distilled water. Fifteen untreated teeth served as control. After obturation, specimens from the experimental groups were thermocycled, dynamically-loaded, and then statically-loaded in a universal testing machine until failure. For flexural strength analysis, 15 teeth were instrumented and irrigated with NaOCl/HEDP or NaOCl/EDTA. Root segments were sectioned into dentin bars and tested for flexural strength using a universal testing machine. For microhardness evaluation, 20 teeth were instrumented and irrigated with NaOCl/HEDP or NaOCl/EDTA. Dentin disks from the coronal-third of each root segment were prepared, one before and one after irrigation, for microhardness testing with a Knoop hardness tester. RESULTS: The highest fracture resistance was recorded in the untreated group, and the lowest in the EDTA group. Although the HEDP group had higher fracture resistance than the EDTA group, the distilled water group demonstrated even greater fracture resistance than the HEDP group. Specimens treated with HEDP had significantly higher flexural strength and microhardness values when compared with those treated with EDTA. CONCLUSION: The fracture resistance, flexural strength, and microhardness of root canal dentin were higher when root canals were irrigated with NaOCl/HEDP, when compared with NaOCl/EDTA. CLINICAL SIGNIFICANCE: Irrigating root canals with NaOCl combined with HEDP significantly improves the mechanical integrity of root canal dentin compared to the use of NaOCl with EDTA.

Dislodgement resistance and structural changes of tricalcium silicate-based cements after exposure to different chelating agents.

This study aimed to evaluate the dislodgement resistance and structural changes of different mineral trioxide aggregate cements (MTA) like Pro-Root MTA, Ortho MTA, and Retro MTA after exposure to sodium hypochlorite (NaOCl), NaOCl-Ethylenediaminetetraacetic acid (EDTA), 1-hydroxyethylidene-1, 1-bisphosphonate (Dual Rinse HEDP), and NaOCl-Maleic acid (MA). The root canal spaces of 150 dentine slices were obturated using tricalcium silicate cements and divided into 3 groups (n = 50): Group1: ProRoot MTA, Group2: Retro MTA, and Group3: Ortho MTA. The samples in each group were further subdivided into four experimental (n = 10) and one control groups (n = 10): 2.5% NaOCl-17% EDTA, Dual Rinse HEDP, 2.5% NaOCl-7% Maleic acid, 2.5% NaOCl, distilled water (control). The dislodgement resistance and structural changes of cements were measured. Use of DR HEDP resulted in higher dislodgement resistance compared to17% EDTA and 7% MA in the samples obturated with Ortho MTA and Pro-Root MTA (p<0.001). In Retro MTA group, samples treated with DR HEDP and 17% EDTA had higher dislodgment resistance compared to 7% MA (p<0.001). On microstructural and elemental analysis of all the three MTA cements, samples treated with 17% EDTA and 7% MA were more amorphous and granular when compared to DR HEDP, which was pettle shaped. Calcium level was decreased more in samples treated with 17% EDTA and 7% MA when compared to DR HEDP.

Biological and chemical properties of 2-in-1 calcium-chelating and antibacterial root canal irrigants.

OBJECTIVES: To evaluate the capacity of canal wall smear layer removal, precipitation caused by irrigant interaction, antibacterial activity and cytotoxicity of three 2-in-1 root canal irrigating solutions. METHODS: Forty single-rooted teeth were mechanically instrumented and irrigated with QMix, SmearOFF, Irritrol or 0.9% saline. Each tooth was evaluated for smear layer removal using scanning electron microscopy. Precipitation after interaction of the irrigating solutions with sodium hypochlorite (NaOCl) was evaluated with 1H nuclear magnetic resonance and mass spectroscopy. Confocal laser scanning microscopy was used to evaluate the antimicrobial activity of the irrigants against Enterococcus faecalis biofilms. Neutral red and clonogenic assays were performed on Chinese hamster V79 cells to evaluate the short-term and long-term cytotoxicity of the irrigants. RESULTS: There was no significant difference between QMix and SmearOFF in eliminating smear layers from the coronal-third and middle-third of the canal spaces. In the apical-third, SmearOFF removed smear layers effectively. Irritrol incompletely removed smear layers from all the canal-thirds. When mixed with NaOCl, precipitation was evident only with Irritrol. QMix demonstrated a higher E. faecalis cell death percentage and a smaller biovolume. SmearOFF exhibited a larger decrease in biovolume compared with Irritrol, although Irritrol had a higher death percentage. Irritrol was more cytotoxic than the other irrigants on a short-term interval. In terms of long-term cytotoxicity, both Irritrol and QMix were cytotoxic. CONCLUSION: QMix and SmearOFF performed better in smear layer removal and antimicrobial activity. QMix and Irritrol were cytotoxic when compared to SmearOFF. Irritrol was associated with precipitation after interacting with NaOCl. CLINICAL SIGNIFICANCE: Evaluation of the smear layer removal capability, antibacterial activity and cytotoxicity of 2-in-1 root canal irrigants is necessary to ensure that they are safe to use during root canal treatment.

Effect of Maleic Acid Root Conditioning on Release of Transforming Growth Factor Beta 1 from Infected Root Canal Dentin.

INTRODUCTION: Chemically released growth factors play a vital role in regenerative endodontics. Transforming growth factor beta 1 (TGF-ß1) is 1 of the most extensively studied bioactive molecules that promotes cell proliferation, differentiation, and chemotaxis. The goal of the current research was to analyze the effect of 7% maleic acid (MA) root conditioning of an infected root canal on the release of TGF-ß1. METHODS: Single-rooted human teeth were decoronated, and the canals were enlarged with a Peeso reamer. The samples were divided into biofilm and nonbiofilm groups. Subsequently, all the samples of both groups were flushed with 10 mL of each irrigant, namely, 1.5% sodium hypochlorite (NaOCl), 7% MA, 17% EDTA, and a combination of 1.5% NaOCl with 17% EDTA or 7% MA, for 10 minutes each. TGF-ß1 was estimated quantitatively using an enzyme-linked immunosorbent assay kit. RESULTS: TGF-ß1 release was lowest among the biofilm samples compared with nonbiofilm among all the groups. MA 7% with 1.5% NaOCl rendered higher amounts of growth factor release in contrast to the combination of 17% EDTA and 1.5% NaOCl in both the biofilm and nonbiofilm groups (P < .048). The nonbiofilm samples treated with 7% MA alone illustrated higher growth factor release compared with 17% EDTA only (P < .006), but there was no significant difference in growth factor release among the biofilm samples treated with 7% MA and 17% EDTA. CONCLUSIONS: Bacterial biofilms modified the release of TGF-ß1. MA 7% was observed to be significantly more efficacious than 17% EDTA in TGF-ß1 growth factor release from radicular dentin.