- Email: [email protected]
The impact of irrigant solutions on root canal filling materials
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assay and employing osteoblast and fibroblast cell lineages. Materials and methods: Extracts of each sealer were prepared following a 24-h exposure to culture media (extract media). Mouth fibroblasts and Saos2 (osteoblast-like cells) were cultured in DMEM containing 10% FBS. Cells were seeded into 96-well plates (Corning, Elmira, NY, USA) at a concentration of 2 × 104 cells/well and incubated for 48 h. For both cell lineages, the same experiment steps were carried out. Elution experiments: The cells were exposed to “extract media” in the following way: undiluted—culture medium was replaced by extract media; extract media—medium containing extracts from the respective sealer was diluted with fresh sterile DMEM in ratios of 1:1, 1:2, and 1:5. Each blended medium with a different extract concentration was used as the new culture medium for plated cells. Control was exposed only to DMEM 10%. Cells were exposed for 24 h to test samples, and at the end of treatment, cytotoxicity was evaluated by two independent endpoints: MTT assay and Neutral Red (NR). Each condition was tested on 6 replicates to ensure reproducibility. Results from each test and experimental time were compared using a one-way analysis of variance (ANOVA). Results: No tests at high concentration (1; 1:1 extract) detected differences in cell viability in either of the two sealers using the MTT or NR assay (p > .05) in a fibroblast culture. At dilutions of 1:2 and 1:5, the BC sealer presented results superior to the MTA group, and NC showed high levels of absorbance (p < .001). In the osteoblast culture, both sealers showed lower absorbance than the NC, as demonstrated by MMT and NR assays (p < .005). Using the NR assay, the BC group with a dilution of 1:5 was statistically superior to MTA (p < .05), with absorbance levels equivalent to the control (p > .005). In both cell culture models, MTA was as cytotoxic as the PC in dilutions of 1 to 1:2 (p > .05). Conclusions: The BC sealer was less cytotoxic than MTA, stimulating fibroblast proliferation. However, the cytotoxicity of sealers varies depending on the cell type examined, as the osteoblast results showed.
taken like the first ones. After gutta-percha insertion, the specimen’s apexes were ground allowing gutta-percha visualization and a picture was taken from the apex to identify root canal deformation with computer software. The flexion of files were evaluated from both initial and final radiographs as the angle formed between the divergence of the file path and its virtual image representing its trail in no presence of curvature. Results: Wilcoxon and Mann–Whitney U-tests were used for data analyses and level of significance was set at 0.05. All files flexion angles decreased after instrumentation (0.002 and 0.001) mesio-distal and buccal-lingual respectively. Group 1 presented the highest variation in flexion angles compared to group 2 (0.112) and group 3 (0.024). NiTi rotary system promoted lower apical stop deformation than the both manual techniques using NiTi (0.011) and stainless steel (0.025). Conclusions: Force vectors caused by the flexion angles of files during the instrumentation of curved canals promoted apical stop deformation. ProTaper Universal rotary files showed less apical deformation than hand ProTaper Universal and stainless steel files (Table 1).
Table 1 – Mann–Whitney test probabilities according to the instrumentation techniques used for each group. Variables
Frontal angle variation Lateral angle variation Deformation (%) ∗
Probability Group 1
Group 2
Group 3
0.303 0.048* 0.672
0.092 0.860 0.025*
0.978 0.000* 0.011*
Indicates significant difference between initial and final variation of the angles and deformation (p < .05).
http://dx.doi.org/10.1016/j.dental.2012.07.140 134 The impact of irrigant solutions on root canal filling materials
http://dx.doi.org/10.1016/j.dental.2012.07.139
M. Prado 1,2,∗ , D.F. Assis 1 , R.A. Simão 1 , B.P.F.A. Gomes 2
133 Files flexion angles influence in the apical third instrumentation
1
A.G. Pereira ∗ , R.M.F. Santos, K.C.M. Azevedo, L.C.M. Dantas, L.H.A. Raposo, J.C.G. Biffi Federal University of Uberlândia, Brazil Objectives: The aim of this study was to evaluate the influence of flexion angles produced by files during root canal instrumentation on the final form of apical stop. Materials and methods: Sixty human lower incisors were divided into three groups (n = 20). After coronal opening and tooth length measuring, radiographs were taken in two aspects (mesio-distal and buccal-lingual) with a #15 K-file at working length. Teeth from group 1 were instrumented with stainless steel Flexofiles up to #40 file. For groups 2 and 3, hand ProTaper Universal and ProTaper Universal rotary files were used respectively, up to file F4. New radiographs were
2
Federal University of Rio de Janeiro, Brazil State University of Campinas, Brazil
Objectives: Gutta-percha (GP) and Resilon (Res) cones are manufactured under aseptic conditions, but they can be contaminated during the storage process. Because of their thermoplastic characteristics, the conventional heating processes cannot be used for sterilization. Irrigant solutions such as sodium hypochlorite (NaOCl) and chlorhexidine (CHX) are, therefore, used for cones disinfection. The objective of this study was to evaluate the effect of 5.25% sodium hypochlorite and 2% chlorhexidine, on the surface of gutta-percha and Resilon cones by means of scanning electron microscopy (SEM) and the contact angle analyses. Moreover, the influence of these solutions in the interaction between GP and Res with the root canal sealers AH Plus and Real Seal was investigated by means of the contact angle and the Atomic Force Microscopy (AFM) analyses. Materials and methods: A total of 9 GP and Res cones and forty-five flat smooth surfaces of each material were
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used. The samples were divided into 6 groups as follows: G1: GP immersed in ultrapure water (UPW); G2: GP immersed in CHX, then washed with UPW; G3: GP immersed in NaOCl, then washed with UPW; G4: Res immersed in UPW; G5: Res immersed in CHX, then washed with UPW; and G6: Res immersed in NaOCl, then washed with UPW. The cones were analyzed by SEM to evaluate changes on the surface of these materials. The flat smooth surfaces were analyzed with a goniometer to measure the contact angle between the test surfaces and 3 solutions (water, ethylene glycol, and diiodomethane) to determine the surface free energy. Moreover, the contact angle between the flat surfaces and each one of the tested sealers was also measured. Finally, AFM was used to investigate the adhesion force (Fad) between root canal sealers and GP and Res surfaces. Data were statistically analyzed using Kruskal–Wallis and Mann–Whitney tests (p < 0.05). Results: The use of NaOCl and CHX solutions did not morphologically alter the cone surfaces, but they increased the surface free energy. Evaluating the interaction between solid filling materials (GP and Res) and root canal sealers, the use of chlorhexidine showed the lowest values of contact angle and the highest Fad values. Conclusions: The irrigant solutions employed in cones decontamination, 5.25% sodium hypochlorite and 2% chlorhexidine, increased the surface free energy, promoting a high interaction between GP/Res and sealers. 2% CHX resulted in lower values of contact angle and higher Fad values when compared with 5.25% NaOCl. http://dx.doi.org/10.1016/j.dental.2012.07.141 135 Pulp regeneration medicaments effect on microindentation of root canal dentin G.H. Yassen 1,∗ , G.J. Eckert 2 , J.A. Platt 1 1
Indiana University School of Dentistry, USA 2 Indiana University School of Medicine, USA
Objectives: To investigate the effect of three suggested pulp regeneration medicaments on the microindentation of the superficial root canal dentin of immature human teeth. Materials and methods: Extracted intact immature human premolars were selected (n = 22). The root from each tooth was sectioned horizontally into two 4 mm dentin cylinders. The pulp tissues were removed with a barbed broach. Then, each cylinder was carefully sectioned longitudinally across the maximum diameter of the root canal into two dentin specimens without touching the root canal dentin surface. The four specimens obtained from each root were randomly assigned into three experimental groups and one control group. Each specimen was placed in a 2 mL sample cup containing 0.15 mL of the treatment pastes (tri-antibiotic pastes, bi-antibiotic paste, or calcium hydroxide) or de-ionized water (control). The containers were stored under 37 ◦ C for either one week or one month. After each time interval, 44 specimens from 11 teeth were removed and washed with de-ionized water. Microindentations on the superficial root canal dentin were performed using a BioDent reference point indenter (RPI) according to the following protocol: indentation force = 5 N; indentations
per second = 2 Hz; indentations per measurement = 10 cycles. The following variables were measured: indentation distance increase (IDI), first cycle indentation distance (ID), total indentation distance (TID), and creep indentation distance (CID). One randomly selected specimen from each group was examined under SEM. Two-way ANOVA was used for statistical analysis (˛ = 0.05). Results: The IDI, ID, CID and TID variables were significantly higher among triple paste and bi-paste treated groups compared to control and calcium hydroxide treated groups at both time intervals. Furthermore, IDI, ID, and TID variables were significantly lower among calcium hydroxide treated group compared to the control group at both time intervals. The SEM showed clear micro-fractures created by BioDent RPI. Additionally, exposed collagen fibers were noticed in the triantibiotic paste treated dentin specimen. Conclusions: The three suggested pulp regeneration medicaments significantly affect the microindentation of root canal dentin surface. BioDent RPI may offer an advantage of measuring the microindentation of root canal dentin surface in immature teeth without the need of any canal surface preparation. http://dx.doi.org/10.1016/j.dental.2012.07.142 Paffenbarger Award finalists P1 Effect of acrolein-based primer as collagen cross-linker on adhesion V. Angeloni 1,∗ , A. Mazzoni 1 , M. Cadenaro 1 , G. Marchesi 1 , L. Manzoli 2 , L. Breschi 1 1 2
University of Trieste, Italy University of Bologna, Italy
Objectives: To investigate the potential effect of a collagen cross-linker on bonding effectiveness and stability over time, the hypothesis tested in this study was that pretreatment with acrolein-based primer before bonding application can improve the mechanical properties and stability over time of the hybrid layer created by a two step etch-and-rinse adhesive system. Materials and methods: Sixteen middle/deep dentin surfaces were etched with 37% phosphoric acid for 15 s, rinsed and blot dried. Specimens were then assigned to: Group 1: dentin was pretreated with 0.01% acrolein water solution, for 1 min, then bonded with Adper Scotchbond 1 XT (3M ESPE), a 2-step etch-and-rinse adhesive system; Group 2: Adper Scotchbond 1 XT was applied on untreated etched dentin (control group). The adhesives were generously applied to dentin with a microbrush for 15 s and light cured for 20 s after solvent evaporation. Composite buildups were made using Filtek Z250 (3M ESPE). The bonded teeth were sectioned into 1 mm x 1 mm beams for microtensile bond strength test (TBS) in accordance with the non trimming technique and stressed to failure at a crosshead speed of 1 mm/min. TBS was performed 24 h after specimen preparation and 6 months after storage in artificial saliva at 37 ◦ C. The TBS data were analyzed using two-way ANOVA and Tukey’s multiple comparison tests.
d e n t a l m a t e r i a l s 2 8 S ( 2 0 1 2 ) e1–e70
assay and employing osteoblast and fibroblast cell lineages. Materials and methods: Extracts of each sealer were prepared following a 24-h exposure to culture media (extract media). Mouth fibroblasts and Saos2 (osteoblast-like cells) were cultured in DMEM containing 10% FBS. Cells were seeded into 96-well plates (Corning, Elmira, NY, USA) at a concentration of 2 × 104 cells/well and incubated for 48 h. For both cell lineages, the same experiment steps were carried out. Elution experiments: The cells were exposed to “extract media” in the following way: undiluted—culture medium was replaced by extract media; extract media—medium containing extracts from the respective sealer was diluted with fresh sterile DMEM in ratios of 1:1, 1:2, and 1:5. Each blended medium with a different extract concentration was used as the new culture medium for plated cells. Control was exposed only to DMEM 10%. Cells were exposed for 24 h to test samples, and at the end of treatment, cytotoxicity was evaluated by two independent endpoints: MTT assay and Neutral Red (NR). Each condition was tested on 6 replicates to ensure reproducibility. Results from each test and experimental time were compared using a one-way analysis of variance (ANOVA). Results: No tests at high concentration (1; 1:1 extract) detected differences in cell viability in either of the two sealers using the MTT or NR assay (p > .05) in a fibroblast culture. At dilutions of 1:2 and 1:5, the BC sealer presented results superior to the MTA group, and NC showed high levels of absorbance (p < .001). In the osteoblast culture, both sealers showed lower absorbance than the NC, as demonstrated by MMT and NR assays (p < .005). Using the NR assay, the BC group with a dilution of 1:5 was statistically superior to MTA (p < .05), with absorbance levels equivalent to the control (p > .005). In both cell culture models, MTA was as cytotoxic as the PC in dilutions of 1 to 1:2 (p > .05). Conclusions: The BC sealer was less cytotoxic than MTA, stimulating fibroblast proliferation. However, the cytotoxicity of sealers varies depending on the cell type examined, as the osteoblast results showed.
taken like the first ones. After gutta-percha insertion, the specimen’s apexes were ground allowing gutta-percha visualization and a picture was taken from the apex to identify root canal deformation with computer software. The flexion of files were evaluated from both initial and final radiographs as the angle formed between the divergence of the file path and its virtual image representing its trail in no presence of curvature. Results: Wilcoxon and Mann–Whitney U-tests were used for data analyses and level of significance was set at 0.05. All files flexion angles decreased after instrumentation (0.002 and 0.001) mesio-distal and buccal-lingual respectively. Group 1 presented the highest variation in flexion angles compared to group 2 (0.112) and group 3 (0.024). NiTi rotary system promoted lower apical stop deformation than the both manual techniques using NiTi (0.011) and stainless steel (0.025). Conclusions: Force vectors caused by the flexion angles of files during the instrumentation of curved canals promoted apical stop deformation. ProTaper Universal rotary files showed less apical deformation than hand ProTaper Universal and stainless steel files (Table 1).
Table 1 – Mann–Whitney test probabilities according to the instrumentation techniques used for each group. Variables
Frontal angle variation Lateral angle variation Deformation (%) ∗
Probability Group 1
Group 2
Group 3
0.303 0.048* 0.672
0.092 0.860 0.025*
0.978 0.000* 0.011*
Indicates significant difference between initial and final variation of the angles and deformation (p < .05).
http://dx.doi.org/10.1016/j.dental.2012.07.140 134 The impact of irrigant solutions on root canal filling materials
http://dx.doi.org/10.1016/j.dental.2012.07.139
M. Prado 1,2,∗ , D.F. Assis 1 , R.A. Simão 1 , B.P.F.A. Gomes 2
133 Files flexion angles influence in the apical third instrumentation
1
A.G. Pereira ∗ , R.M.F. Santos, K.C.M. Azevedo, L.C.M. Dantas, L.H.A. Raposo, J.C.G. Biffi Federal University of Uberlândia, Brazil Objectives: The aim of this study was to evaluate the influence of flexion angles produced by files during root canal instrumentation on the final form of apical stop. Materials and methods: Sixty human lower incisors were divided into three groups (n = 20). After coronal opening and tooth length measuring, radiographs were taken in two aspects (mesio-distal and buccal-lingual) with a #15 K-file at working length. Teeth from group 1 were instrumented with stainless steel Flexofiles up to #40 file. For groups 2 and 3, hand ProTaper Universal and ProTaper Universal rotary files were used respectively, up to file F4. New radiographs were
2
Federal University of Rio de Janeiro, Brazil State University of Campinas, Brazil
Objectives: Gutta-percha (GP) and Resilon (Res) cones are manufactured under aseptic conditions, but they can be contaminated during the storage process. Because of their thermoplastic characteristics, the conventional heating processes cannot be used for sterilization. Irrigant solutions such as sodium hypochlorite (NaOCl) and chlorhexidine (CHX) are, therefore, used for cones disinfection. The objective of this study was to evaluate the effect of 5.25% sodium hypochlorite and 2% chlorhexidine, on the surface of gutta-percha and Resilon cones by means of scanning electron microscopy (SEM) and the contact angle analyses. Moreover, the influence of these solutions in the interaction between GP and Res with the root canal sealers AH Plus and Real Seal was investigated by means of the contact angle and the Atomic Force Microscopy (AFM) analyses. Materials and methods: A total of 9 GP and Res cones and forty-five flat smooth surfaces of each material were
e62
d e n t a l m a t e r i a l s 2 8 S ( 2 0 1 2 ) e1–e70
used. The samples were divided into 6 groups as follows: G1: GP immersed in ultrapure water (UPW); G2: GP immersed in CHX, then washed with UPW; G3: GP immersed in NaOCl, then washed with UPW; G4: Res immersed in UPW; G5: Res immersed in CHX, then washed with UPW; and G6: Res immersed in NaOCl, then washed with UPW. The cones were analyzed by SEM to evaluate changes on the surface of these materials. The flat smooth surfaces were analyzed with a goniometer to measure the contact angle between the test surfaces and 3 solutions (water, ethylene glycol, and diiodomethane) to determine the surface free energy. Moreover, the contact angle between the flat surfaces and each one of the tested sealers was also measured. Finally, AFM was used to investigate the adhesion force (Fad) between root canal sealers and GP and Res surfaces. Data were statistically analyzed using Kruskal–Wallis and Mann–Whitney tests (p < 0.05). Results: The use of NaOCl and CHX solutions did not morphologically alter the cone surfaces, but they increased the surface free energy. Evaluating the interaction between solid filling materials (GP and Res) and root canal sealers, the use of chlorhexidine showed the lowest values of contact angle and the highest Fad values. Conclusions: The irrigant solutions employed in cones decontamination, 5.25% sodium hypochlorite and 2% chlorhexidine, increased the surface free energy, promoting a high interaction between GP/Res and sealers. 2% CHX resulted in lower values of contact angle and higher Fad values when compared with 5.25% NaOCl. http://dx.doi.org/10.1016/j.dental.2012.07.141 135 Pulp regeneration medicaments effect on microindentation of root canal dentin G.H. Yassen 1,∗ , G.J. Eckert 2 , J.A. Platt 1 1
Indiana University School of Dentistry, USA 2 Indiana University School of Medicine, USA
Objectives: To investigate the effect of three suggested pulp regeneration medicaments on the microindentation of the superficial root canal dentin of immature human teeth. Materials and methods: Extracted intact immature human premolars were selected (n = 22). The root from each tooth was sectioned horizontally into two 4 mm dentin cylinders. The pulp tissues were removed with a barbed broach. Then, each cylinder was carefully sectioned longitudinally across the maximum diameter of the root canal into two dentin specimens without touching the root canal dentin surface. The four specimens obtained from each root were randomly assigned into three experimental groups and one control group. Each specimen was placed in a 2 mL sample cup containing 0.15 mL of the treatment pastes (tri-antibiotic pastes, bi-antibiotic paste, or calcium hydroxide) or de-ionized water (control). The containers were stored under 37 ◦ C for either one week or one month. After each time interval, 44 specimens from 11 teeth were removed and washed with de-ionized water. Microindentations on the superficial root canal dentin were performed using a BioDent reference point indenter (RPI) according to the following protocol: indentation force = 5 N; indentations
per second = 2 Hz; indentations per measurement = 10 cycles. The following variables were measured: indentation distance increase (IDI), first cycle indentation distance (ID), total indentation distance (TID), and creep indentation distance (CID). One randomly selected specimen from each group was examined under SEM. Two-way ANOVA was used for statistical analysis (˛ = 0.05). Results: The IDI, ID, CID and TID variables were significantly higher among triple paste and bi-paste treated groups compared to control and calcium hydroxide treated groups at both time intervals. Furthermore, IDI, ID, and TID variables were significantly lower among calcium hydroxide treated group compared to the control group at both time intervals. The SEM showed clear micro-fractures created by BioDent RPI. Additionally, exposed collagen fibers were noticed in the triantibiotic paste treated dentin specimen. Conclusions: The three suggested pulp regeneration medicaments significantly affect the microindentation of root canal dentin surface. BioDent RPI may offer an advantage of measuring the microindentation of root canal dentin surface in immature teeth without the need of any canal surface preparation. http://dx.doi.org/10.1016/j.dental.2012.07.142 Paffenbarger Award finalists P1 Effect of acrolein-based primer as collagen cross-linker on adhesion V. Angeloni 1,∗ , A. Mazzoni 1 , M. Cadenaro 1 , G. Marchesi 1 , L. Manzoli 2 , L. Breschi 1 1 2
University of Trieste, Italy University of Bologna, Italy
Objectives: To investigate the potential effect of a collagen cross-linker on bonding effectiveness and stability over time, the hypothesis tested in this study was that pretreatment with acrolein-based primer before bonding application can improve the mechanical properties and stability over time of the hybrid layer created by a two step etch-and-rinse adhesive system. Materials and methods: Sixteen middle/deep dentin surfaces were etched with 37% phosphoric acid for 15 s, rinsed and blot dried. Specimens were then assigned to: Group 1: dentin was pretreated with 0.01% acrolein water solution, for 1 min, then bonded with Adper Scotchbond 1 XT (3M ESPE), a 2-step etch-and-rinse adhesive system; Group 2: Adper Scotchbond 1 XT was applied on untreated etched dentin (control group). The adhesives were generously applied to dentin with a microbrush for 15 s and light cured for 20 s after solvent evaporation. Composite buildups were made using Filtek Z250 (3M ESPE). The bonded teeth were sectioned into 1 mm x 1 mm beams for microtensile bond strength test (TBS) in accordance with the non trimming technique and stressed to failure at a crosshead speed of 1 mm/min. TBS was performed 24 h after specimen preparation and 6 months after storage in artificial saliva at 37 ◦ C. The TBS data were analyzed using two-way ANOVA and Tukey’s multiple comparison tests.