Aspects of glass and hybridization protocols for bonding of fiber posts to root dentine.

This study evaluated bond strength of glass fiber posts to root dentin using push-out (PO) and diametral compression (DC), testing glycolic acid as a conditioner and varying dentin moisture. An additional aim was to test whether DC can be an alternative test to PO for bond strength assessment. Eighty bovine teeth were divided into eight groups (n = 10) defined by the use of either 37% glycolic acid or 37% phosphoric acid (PA) on moist or wet dentin before bonding with either Adapter SingleBond/RelyX ARC or One Step Plus/Duo-Link Bisco. Each tooth provided discs with an internal diameter of 2 mm, external diameter of 5 mm, and height of 2 mm, which underwent PO and DC. Finite element analysis (FEA) was carried out on 3D models. When analyzing PO results through linear regression, the highest values of bond strength were observed using glycolic acid on wet dentin in the cervical and middle thirds of the teeth. Analyzing DC results, the only statistical influence on values was the dental thirds. The scatterplot of the DC results and the PO bond strength values indicated no relationship between the results of the two tests (r = 0.03; p = 0.64). PO test detected more sensitive changes in bond strength values than DC.

Antimicrobial activity of glycolic acid as a final irrigant solution for root canal preparation.

The objective of this study was to evaluate the antimicrobial capacity of glycolic acid (GA) at different concentrations as a final irrigant during the preparation of root canals. The sample consisted of 77 extracted single-rooted human teeth with complete root formation, no previous endodontic treatment, and a root length of at least 14 mm. The root canals were prepared in a standardized manner with a rotary file system. During this process, irrigation was performed with 2.5% sodium hypochlorite (NaOCl), and the final irrigant was 17% ethylenediaminetetraacetic acid (EDTA). After the root canal sterilization procedure, Enterococcus faecalis was cultured in a Petri dish, and 70 sterilized root canals were inoculated with a suspension containing 3.0 × 108 colony-forming units (CFUs) per milliliter. The roots were divided into 7 groups (n = 10) according to the following solutions: 0.9% sodium chloride (NaCl); 6% NaOCl; 17% EDTA; 10%, 17%, or 25% GA; or 17% citric acid (CA). The capacity of the different substances to reduce E faecalis was evaluated by counting the CFUs before and after treatment with the final irrigant solutions. Data were subjected to an analysis of variance and the Tukey test at a 5% significance level. The greatest bacterial reduction was observed in the group irrigated with NaOCl (P < 0.05). There were no statistically significant differences among the groups irrigated with GA in different concentrations (P > 0.05), but they all demonstrated greater disinfection capacity than CA and EDTA (P < 0.05). CA showed significantly greater antimicrobial capacity than EDTA (P < 0.05). EDTA showed significantly greater antimicrobial capacity only in relation to NaCl (P < 0.05). At different concentrations, GA demonstrated greater capacity to eliminate E faecalis from root canals than did EDTA.

Structural and biomechanical changes to dentin extracellular matrix following chemical removal of proteoglycans.

Proteoglycans are biomacromolecules with significant biomineralization and structural roles in the dentin extracellular matrix. This study comprehensively assessed the mechanical properties and morphology of the dentin extracellular matrix following chemical removal of proteoglycans to elucidate the structural roles of proteoglycans in dentin. Dentin extracellular matrix was prepared from extracted teeth after complete tissue demineralization. Chemical removal of proteoglycans was carried-out using guanidine hydrochloride for up to 10 days. The removal of proteoglycans was determined by dimethylmethylene blue colorimetric assay and histological staining analyses using transmission electron microscopy and optical microscopy. The modulus of elasticity of dentin matrix was determined by a 3-point bending test method. Partial removal of proteoglycans induced significant modifications to the dentin matrix, particularly to type I collagen. Removal of proteoglycans significantly decreased the modulus of elasticity of dentin extracellular matrix (p < 0.0001). In conclusion, the subtle disruption of proteoglycans induces pronounced changes to the collagen network packing and the bulk modulus of elasticity of dentin matrix.

Efficacy of Natural Collagen Crosslinkers on the Compromised Adhesive Bond Strength to NaOCl-treated Pulp Chamber Dentin.

PURPOSE: To evaluate the efficacy of natural collagen crosslinkers on compromised adhesive bond strength to NaOCl-treated pulp chamber dentin. MATERIALS AND METHODS: Mesial surfaces of the pulp chamber dentin of 120 extracted human molars were obtained. The dentin fragments were divided into six groups according to the protocols used: no treatment (negative control), sodium hypochlorite (NaOCl) for 30 min and final irrigation with 17% EDTA for 3 min (positive control). After treatment with NaOCl and EDTA, the dentin surfaces of the experimental groups were treated for 5 min with one of the following: grape seed extract (GSE), tannic acid (TA), green tea (GT), or n-acetyl cysteine (NAC). Half of the samples of each group were bonded with an etch-and-rinse (Single Bond; 3M Oral Care) and the other half using a self-etch (Scotchbond Universal; 3M Oral Care) adhesive. The restoration was completed with composite. The bonded specimens were sectioned to produce sticks and subjected to the microtensile bond strength test. Data were analyzed by two-way ANOVA and Tukey's HSD test (p < 0.05). RESULTS: Both adhesives had similar bond strengths (p > 0.05). The NaOCl-treated group had significantly lower bond strength than the negative control (p < 0.05). The application of NAC did not recover compromised bonding (p > 0.05). On the other hand, GSE, TA and GT had significant reversal effects of the bond strengths to NaOCl-treated dentin (p < 0.05). CONCLUSION: Compromised bonding of adhesives to NaOCl-treated dentin can be reversed by the application of either GSE, TA or GT.

Comparative evaluation of the retaining of QMix and chlorhexidine formulations on human dentin: a chemical analysis.

OBJECTIVES: The purpose of this study was to investigate, in vitro, the retaining of 2 % CHX gel, 2 % CHX liquid and QMix (an endodontic irrigant) within a root canal for 24 h, 30, 90, and 120 days by chemical analysis. METHODS: Eighty extracted human teeth were used for this study. The samples were divided into four groups (G1-G4), according to the chemical auxiliary substance used to perform the instrumentation: G1 (control): distilled water, G2: 2 % CHX gel, G3: 2 % CHX liquid, and G4: QMix. The roots were prepared up to the instrument #45 by serial instrumentation. Longitudinal grooves were carved on the free surfaces of the roots, providing 2 halves of each root and resulting in 40 samples per group. Each group was randomly divided into four subgroups (n = 10), and substantivity was evaluated after 24 h, 30, 90, and 120 days. The amount of 2 % CHX gel, 2 % CHX liquid, and QMix (in micrograms) was measured through reverse-phase high-performance liquid chromatography. Statistical analysis was performed by ANOVA and Games-Howell test for post-hoc comparisons (α = 0.05). RESULTS: CHX gel, CHX liquid, and QMix were retained in dentin up to 120 days. Significantly less substantivity was observed for QMix, irrespective of the period of time. Statistically significant higher values were observed for CHX gel after 24 h, while no differences were noted between CHX gel and CHX liquid after 30, 90, and 120 days of evaluation (p < 0.05). CONCLUSIONS: Two percent CHX (gel and liquid) and QMix are retained in root canal dentin for up to 120 days. CLINICAL RELEVANCE: This study proposes an alternative of auxiliary chemical substance to be used during the chemo-mechanical preparation.

Influence of Cement Type and Relining Procedure on Push-Out Bond Strength of Fiber Posts after Cyclic Loading.

PURPOSE: The aim of this study was to evaluate the influence of cement type and relining procedure on push-out bond strength of fiber posts (FPs) after cyclic loading. MATERIALS AND METHODS: Forty bovine incisor roots were divided into four groups: group 1, FP luting with RelyX Unicem; group 2, FP relined with resin composite (FPC) luting with RelyX Unicem; group 3, FP luting with RelyX ARC; group 4, FPC luting with RelyX ARC. Afterwards, half the specimens were exposed to 250,000 cycles in a controlled chewing simulator. With the other half of the specimens in each group, the push-out test was performed 24 hours after FP luting (immediate groups). All roots were sectioned transversely, producing 1-mm-thick slices, and the push-out test was performed. Statistical analysis was performed using ANOVA and the Tukey test for post hoc comparisons (α = 0.05). RESULTS: FPC had higher bond strengths than FP (p < 0.05). RelyX Unicem showed higher bond strength than RelyX ARC (p < 0.05). Cyclic loading did not significantly affect the bond strength value (p > 0.05). CONCLUSION: The relining procedure and the cement type are important factors for the bond strength of FPs to root dentin.

Effect of chlorhexidine and ethanol on push-out bond strength of fiber posts under cyclic loading.

PURPOSE: To investigate the effects of pretreatment with 2% chlorhexidine in a gel base (CHX) and 100% ethanol (EtOH) on the bond strength between fiber posts relined with resin composite and root dentin under cyclic loading. MATERIALS AND METHODS: Forty bovine incisor roots were divided into four groups after phosphoric acid etching: group 1 (control), irrigation with physiological saline solution; group 2, 5 min pretreatment with CHX; group 3, 1 min pretreatment with EtOH; group 4, 5 min pretreatment with CHX followed by 1 min with EtOH. Fiber posts relined with resin composite were cemented with RelyX ARC and the etch-and-rinse adhesive system Scotchbond Multi-Purpose. Each group was randomly divided into two subgroups: 24 h of storage (immediate groups) and cyclic loading (loading groups) with 250,000 cycles in a controlled chewing simulator. All roots were sectioned transversely and push-out tests were performed. Failure modes were observed and the bond strength means were analyzed using ANOVA and Tukey's test (a = 0.05). RESULTS: The mean values for the bond strength test (MPa) in immediate groups were: group 1, 5.44 ± 1.48; group 2, 5.57 ± 1.41; group 3, 5.49 ± 1.48; group 4, 5.57 ± 1.42. Immediate groups showed similar bond strength values (p > 0.05). In the cyclic loading groups, the bond strength values were: group 1, 2.80 ± 0.79; group 2, 4.02 (1.30); group 3, 4.50 ± 1.67; group 4, 4.97 ± 2.00. After cyclic loading, a significant decrease in the control group was observed (p < 0.05), while CHX pretreatment resulted in intermediate values (p < 0.05) and EtOH alone or associated with CHX preserved the bond strength values (p > 0.05). CONCLUSION: Chlorhexidine and/or ethanol pretreatment preserved the bond strength of the fiber post after cyclic loading.

Screw joint stability after the application of retorque in implant-supported dentures under simulated masticatory conditions.

STATEMENT OF PROBLEM: Screws can loosen through mechanisms that have not been clearly established. PURPOSE: The purpose of this study was to evaluate the influence of the tightening technique (the application of torque and retorque on the joint stability of titanium and gold prosthetic screws) in implant-supported dentures under different fit levels after 1 year of simulated masticatory function by means of mechanical cycling. MATERIAL AND METHODS: Ten mandibular implant-supported dentures were fabricated, and 20 cast models were prepared by using the dentures to create 2 fit levels: passive fit and created misfit. The tightening protocol was evaluated according to 4 distinct profiles: without retorque plus titanium screws, without retorque plus gold screws, retorque plus titanium screws, and retorque plus gold screws. In the retorque application, the screws were tightened to 10 Ncm and retightened to 10 Ncm after 10 minutes. The screw joint stability after 1 year of simulated clinical function was measured with a digital torque meter. Data were analyzed statistically by 2-way ANOVA and Tukey honestly significant difference (HSD) post hoc tests (α=.05). RESULTS: The factors of fit level and tightening technique as well as the interaction between the factors, were statistically significant. The misfit decreases the loosening torque. The retorque application increased joint stability independent of fit level or screw material, which suggests that this procedure should be performed routinely during the tightening of these devices. CONCLUSION: All tightening techniques revealed reduced loosening torque values that were significantly lower in misfit dentures than in passive fit dentures. However, the retorque application significantly increased the loosening torque when titanium and gold screws were used. Therefore, this procedure should be performed routinely during screw tightening.

Evaluation of Vickers hardness of different types of acrylic denture base resins with and without glass fibre reinforcement.

OBJECTIVE: To evaluate the Vickers hardness of different acrylic resins for denture bases with and without the addition of glass fibres. BACKGROUND: It has been suggested that different polymerisation methods, as well as the addition of glass fibre (FV) might improve the hardness of acrylic. MATERIALS AND METHODS: Five types of acrylic resin were tested: Vipi Wave (VW), microwave polymerisation; Vipi Flash (VF), auto-polymerisation; Lucitone (LT), QC20 (QC) and Vipi Cril (VC), conventional heat-polymerisation, all with or without glass fibre reinforcement (GFR) and distributed into 10 groups (n = 12). Specimens were then submitted to Vickers hardness testing with a 25-g load for 30 s. All data were submitted to anova and Tukey's HSD test. RESULTS: A significant statistical difference was observed with regard to the polymerisation method and the GFR (p < 0.05). Without the GFR, the acrylic resin VC presented the highest hardness values, and VF and LT presented the lowest. In the presence of GFR, VC resin still presented the highest Vickers hardness values, and VF and QC presented the lowest. CONCLUSIONS: The acrylic resin VC and VW presented higher hardness values than VF and QC resins. Moreover, GFR increased the Vickers hardness of resins VW, VC and LT.

Effect of glycolic acid and EDTA on dentin mechanical properties.

The aim of this study was to evaluate the effect of glycolic acid (GA) and EDTA on dentin mechanical properties. For the cohesive strength, flexural strength and fracture strength tests, the hourglass of root dentin, dentin sticks and roots standardised to 1 mm thickness were used respectively. ANOVA and Tukey tests were used for statistical analysis (P < 0.05). The results showed that EDTA and GA 17% reduced the cohesive strength values when compared to distilled water (control; P = 0.0022 and P = 0.0016 respectively), whereas the values for GA 10% group were similar to those of the control group (P = 0.093). No statistically significant difference was found among the groups for the flexural strength test (P = 0.1974). Fracture strength test showed that EDTA and GA 17% were statistically similar to each other (P = 0.7694) and statistically inferior to GA 10% (P = 0.0007 and P = 0.0004 respectively). It was concluded that 10% GA showed fewer negative effects on dentin mechanical properties.

Influence of photodynamic therapy, different final irrigants, and ultrasonic activation on the bond strength of glass fiber posts to root dentin.

OBJECTIVE: To evaluate the influence of photodynamic therapy (PDT), different final irrigants, and ultrasonic activation (US) on the bond strength of glass fiber posts (GFP) to root dentin. METHODS: One hundred twenty bovine roots were divided into 12 groups according to PDT application, the type of final endodontic irrigant, and US. The samples were divided into 12 groups (n = 10): G1-DW(distilled water); G2-DW+US; G3-17% EDTA; G4-17% EDTA+US; G5-17% GA (glycolic acid); G6-17% GA+US; G7-PDT+DW; G8-PDT+DW+US; G9-PDT+17% EDTA; G10-PDT+17% EDTA+US; G11-PDT+17% GA; G12-PDT+17% GA+US. After cementing the glass fiber posts with resin cement, roots were sectioned into 2-mm-thick slices. One slice from the cervical third and another from the middle third were used for the push out test (PO), and the other two for the diametral compression test (DC). Thus, 10 samples were obtained per third for each mechanical test (n = 10). Kruskal-Wallis and Student-Newman-Keuls tests were used to analyze PO and DC data, and Pearson's correlation test was used to verify the relationship between the variables. Failure patterns were analyzed with chi-square test. RESULTS: Significant differences were found in the PO test among the experimental groups (p < 0.001; power=1.00). PDT improved bond strength when using EDTA. PDT and US increased bond strength when using GA. Favorable failure patterns occurred more frequently in Group GA+US. There was no correlation between data obtained with PO and DC tests (r = 0.112; p = 0.729). CONCLUSION: PDT provided the highest bond strength values of GFP to root dentin when associated with GA and US or when associated only with EDTA.

Bond strength of fiber posts in different root thirds using resin cement.

PURPOSE: The aim of the study was to assess the in vitro bond strength (BS) of glass fiber posts (GF) and carbon fiber posts (CF) in the cervical, middle, and apical thirds of root canals cemented with RelyX-Unicem (RX) and Cement-Post (CP). MATERIALS AND METHODS: Forty maxillary canines were divided into 4 groups (n = 10) according to the cement and post used: group 1: GF and RX; group 2: CF and RX; group 3: GF and CP; group 4: CF and CP. The push-out test was applied in the cervical, middle and apical thirds of each specimen to assess bond strength of the cement/post complex to the root canal wall. The data obtained were submitted to ANOVA (Bonferroni test, p < 0.05), and fracture analysis was done with SEM. RESULTS: The GF posts presented the best results when cemented with RX and with CP (p < 0.05). RX presented the highest BS values for both GF and CF (p < 0.05). For all the groups, BS was higher in the cervical third, followed by the middle and apical thirds. Fracture analysis showed a predominance of cohesive fracture of posts for RX, and a predominance of adhesive fracture between dentin/cement, and mixed failure mode for CP. CONCLUSION: GF posts cemented with RX presented the highest BS values in all root thirds.

Effect of root-canal sealer on the bond strength of fiberglass post to root dentin.

OBJECTIVE: To evaluate the effects of different root-canal sealers on the bond strength of a fiberglass post cemented with self-adhesive resin cements. MATERIAL AND METHODS: Forty extracted maxillary single-rooted canines were prepared with the crown-down technique and randomly divided into four groups according to the tested sealer: Group 1: control group, gutta-percha cone only (no sealer); Group 2: EndoREZ; Group 3: Sealapex; Group 4: Endofill. The roots were obturated with the gutta-percha cone using the cold lateral compaction technique. Fiberglass posts were cemented into the prepared post spaces with the self-adhesive cement RelyX Unicem. Bonded specimens were sectioned into 1-mm thick slabs and a push-out test was performed in a universal machine. RESULTS: Data were subjected to ANOVA and Tukey tests (α = 0.05). No significant difference was detected between Groups 1-3 (P > 0.05). Group 4 showed a lower bond strength than the other sealers (P < 0.05). CONCLUSIONS: Endofill negatively interfered with the bond to root dentine; however, EndoRez and Sealapex did not affect the bond strength of the fiberglass post cemented with self-adhesive resin cements.

The effect of a 980 nm diode laser with different parameters of irradiation on the bond strength of fiberglass posts.

The aim of this study was to assess bond strength of fiberglass posts to root canal dentin irradiated with a 980 nm diode laser at different parameters of power and frequency. Fifty human maxillary canines were separated into five groups (n = 10) according to the following parameters of laser power and frequency: Group 1 (1.5 W/100 Hz), Group 2 (1.5 W/continuous wave [CW]), Group 3 (3.0 W/100 Hz), Group 4 (3.0 W/CW), and Group 5 (no irradiation). Following post cementation, samples underwent a push-out test (0.5 mm/min); next, fracture analysis was performed with a light microscope at 50x and 100x magnification. All of the irradiated groups had increased bond strength values compared to the nonirradiated group. Groups 1 and 2 demonstrated the highest bond strength values; however, statistically significant differences were observed for only the cervical third of Group 4 and the cervical/apical thirds of Group 5. Fracture analysis showed a predominance of mixed failures for Groups 1 and 2 and adhesive failures between dentin and cement for the other groups.

Influence of the apical limit of instrumentation and photodynamic therapy on the postoperative pain of lower molars with asymptomatic apical periodontitis.

INTRODUCTION: The aim of present study was to evaluate the influence of apical limit of instrumentation and PDT on the postoperative pain of lower molars with asymptomatic apical periodontitis. METHODS: Forty patients were included in the present study and were divided into 4 groups (n=10), according to apical limit of instrumentation and use of PDT: instrumentation at 0.0 measurement; instrumentation at 0.0 measurement+PDT; instrumentation 1mm beyond 0.0 measurement; instrumentation 1mm beyond 0.0 measurement+PDT. In the PDT, the root canals were filled with 0.01% methylene blue, remaining for 5 min. The low-intensity laser was used with 100 mW, 660-690 nm wavelength), using intra-canal fibre. Root canals were irradiated for 90 s, delivering total dose of 9 J and energy density of 320 J/cm2. After root canal preparation and PDT protocols, root canals were filled with gutta-percha and AH Plus endodontic sealer, being sealed with composite resin.The evaluation of postoperative pain was performed by visual analog scale after 24, 48, 72 hours and 7 days. Data were analysed by specific statistical tests, at level of 5%. RESULTS: No statistical significant difference was observed among experimental groups in all evaluation periods, as well as in the intragroup analysis over time, regarding postoperative pain and analgesic medication consumption (p>0.05). CONCLUSIONS: Apical limit of instrumentation and PDT have no influence on the postoperative pain of lower molars with asymptomatic apical periodontitis.

Glycolic acid: Characterization of a new final irrigant and effects on flexural strength and structural integrity of dentin.

The aim of this study was to characterize glycolic acid (GA) and examine its effects on powder and flexural strength of dentin. Particle size and energy-dispersive EDS in GA powder was performed for chemical analysis. Surface tension and pH levels of ethylenediaminetetraacetic acid (EDTA), citric acid (CA), and GA solutions were evaluated at different times and temperatures. Dentin powder and mineralized dentin beams were immersed for 1 min in EDTA, CA, or GA solutions and subjected to Fourier transform infrared spectroscopy for apatite/collagen ratio analysis and 3-point flexure test, respectively. GA showed the largest particle size (µm), and its surface tension was similar to that of EDTA and CA. Surface tension decreased in solutions of higher concentrations. GA showed pH stability at all times and temperatures evaluated. The apatite/collagen ratio reduced with increased GA concentrations, while flexural strength was not significantly affected by GA concentration. GA seems a good choice as a final irrigation solution after root canal preparation.

Antibacterial Efficacy of the Grape Seed Extract as an Irrigant for Root Canal Preparation.

Objective: The purpose of this research was to compare relative effectiveness of sodium hypochlorite 5.25% (NaOCl), 2% chlorhexidine gel (CHX) and 6.5 % grape seed extract (GSE) against Enterococcus faecalis using instrument Reciproc R25 in root canal preparation. Methods: Forty-five mesiobuccal root canals from extracted human maxillary molars were collected and infected with Enterococcus faecalis. The samples were divided into five groups according to the different types of irrigants: saline (positive control) (n=5); in the other groups were used 10 root canals for each group: NaOCl+EDTA; CHX gel+EDTA; GSE solution+EDTA; GSE gel+EDTA. All the groups were prepared with reciprocating instruments Reciproc R25. Bacterial reduction was measured by two-way ANOVA (P<0.001) followed by Tukey HSD post-hoc tests, from the counting of colony forming units (CFUs) from samples collected before instrumentation and after. The significance level established at 5% (P<0.05). Results: The group prepared with the NaOCl resulted in highest antimicrobial capacity among of all (P>0.05), followed by CHX and GSE gel (P<0.05). Control and GSE solution showed similar results (P<0.05) and resulted in the lowest percentage of the reduction of the microorganism into the root canals. Conclusion: NaOCl had the higher elimination capacity of Enterococcus faecalis than GSE and CHX.

Removal of water binding proteins from dentin increases the adhesion strength of low-hydrophilicity dental resins.

OBJECTIVES: To investigate the role of proteoglycans (PGs) on the physical properties of the dentin matrix and the bond strength of methacrylate resins with varying hydrophilicities. METHODS: Dentin were obtained from crowns of human molars. Enzymatic removal of PGs followed a standard protocol using 1 mg/mL trypsin (Try) for 24 h. Controls were incubated in ammonium bicarbonate buffer. Removal of PGs was assessed by visualization of glycosaminoglycan chains (GAGs) in dentin under transmission electron microscopy (TEM). The dentin matrix swelling ratio was estimated using fully demineralized dentin. Dentin wettability was assessed on wet, dry and re-wetted dentin surfaces through water contact angle measurements. Microtensile bond strength test (TBS) was performed with experimental adhesives containing 6% HEMA (H6) and 18% HEMA (H18) and a commercial dental adhesive. Data were statistically analyzed using ANOVA and post-hoc tests (α = 0.05). RESULTS: The enzymatic removal of PGs was confirmed by the absence and fragmentation of GAGs. There was statistically significant difference between the swelling ratio of Try-treated and control dentin (p < 0.001). Significantly lower contact angle was found for Try-treated on wet and dry dentin (p < 0.002). The contact angle on re-wet dentin was not recovered in Try-treated group (p = 0.9). Removal of PGs significantly improved the TBS of H6 (109% higher, p < 0.001) and H18 (29% higher, p = 0.002) when compared to control. The TBS of commercial adhesive was not affected by trypsin treatment (p = 0.9). SIGNIFICANCE: Changing the surface energy of dentin by PGs removal improved resin adhesion, likely due to more efficient water displacement, aiding to improved resin infiltration and polymerization.

Effect of a new irrigant solution containing glycolic acid on smear layer removal and chemical/mechanical properties of dentin.

The objective of this study was to evaluate the effects of glycolic acid (GA) (with pH 1.2 and 5) and ethylenediaminetetraacetic acid (EDTA) on the chemical and mechanical properties of dentin to investigate the potential use of GA as final irrigant in the root canal therapy. Specifically, changes in microhardness, smear layer removal, erosion, mineral content distribution, apatite/collagen ratio and flexural strength of mineralized dentin treated with GA were assessed. Saline solution was used as a negative control. Knoop microhardness (KHN) was measured on the root canal lumen of root segments. Dentin beams were used for 3-point flexural strength (σ) test. Scanning electron microscopy (SEM) images of root sections were obtained for evaluation of smear layer removal and dentin erosion on root segments and energy dispersive X-ray spectroscopy (EDS) was used for mineral content distribution. The apatite/collagen ratio (A/C) in dentin powder were examined by Fourier transform infrared (FTIR) spectroscopy. KHN, σ and A/C results were statistically analyzed with ANOVA and Tukey tests (α = 0.05). Smear layer and dentin erosion scores were analyzed with Kruskal-Wallis and Dunn tests (α = 0.05). Root dentin treated with EDTA and GA presented similar KHN regardless of the pH (p > 0.05). However, KHN was significantly reduced in EDTA and GA groups when compared to control group (p<0.001). GA showed the same ability to remove the smear layer and to cause dentin erosion as EDTA. EDS results showed that the GA and EDTA solutions did not alter the dentin mineral content distribution. The apatite/collagen ratio reduced with all irrigant solution and was the lowest with GA pH 5 (p<0.001), while σ was not significantly affected by the experimental solutions (p = 0.559). It can be concluded that GA has similar ability to remove the smear layer than EDTA. GA does not affect negatively the chemical/mechanical properties and it does not increase dentin erosion. The use of GA with low pH seems to promote less change in collagen/apatite ratio, but further studies are needed to establish an ideal clinical protocol. Therefore, this study supports the potential use of GA as an alternative final irrigation solution for root canal preparation.

Association of calcium hypochlorite, reciprocating instrumentation and photodynamic therapy: Antimicrobial analysis and effects on root dentin structure.

INTRODUCTION: This study aimed to evaluate the antimicrobial action of calcium hypochlorite(Ca[OCl]2) and sodium hypochlorite (NaOCl) with reciprocating instrumentation and photodynamic therapy(PDT), and its influence on root dentin structure. METHODS: One hundred and ten human teeth were used to antimicrobial evaluation, inoculated with Enterococcus faecalis and divided into 11 groups (n = 10): G1 - distilled water(control); G2-1 % NaOCl; G3-5.25 % NaOCl; G4-1 % Ca(OCl)2; G5-5.25 % Ca(OCl)2; G6-PDT; G7-distilled water + PDT; G8-1 % NaOCl + PDT; G9-5.25 % NaOCl + PDT; G10-1 % Ca(OCl)2+PDT; G11-5.25 % Ca(OCl)2+PDT. In all groups, except G6, the root canals were instrumented with #R50 Reciproc file in the working length in association with tested chemical auxiliary substance. The counting of colony forming units (CFUs) was performed to calculate the bacterial percentage reduction of each group. Following, 55 bovine teeth were used to microhardness evaluation and divided into the same 11 groups (n = 5), with no instrumentation and immersion in the tested protocols. The modification of root dentin microhardness was evaluated by using the Vicker tester. Finally, 33 bovine teeth were used to organic components evaluation and divided into the same 11 groups (n = 3), with no instrumentation and immersion in the tested protocols. The modification of organic components of root dentin was evaluated by light microscopy. Specific statistical analysis was performed for each evaluation. RESULTS: The higher bacterial reduction was observed in groups 3,4,5,8,9,10 and 11, with no statistical difference between them (p > 0.05). The higher microhardness reduction was observed in groups 8,9,10 e 11, with no statistical difference between them (p > 0.05). The highest modification on organic components was observed in groups 3,5,9 and 11, with no statistical difference between them (p > 0.05). CONCLUSIONS: The association of Ca(OCl)2, reciprocating instrumentation and PDT promotes effective antimicrobial action. Moreover, lower modification was induced in microhardness and organic components of root dentin, by using Ca(OCl)2 in low concentration associated to PDT.