Kamran Safavi - Academia.edu (original) (raw)

Papers by Kamran Safavi

Research paper thumbnail of A Rapid Non-destructive Method for Root Dentin Moisture Measurements

Dentin moisture content is important in adhesive bonding and structural strength research. Howeve... more Dentin moisture content is important in adhesive bonding and structural strength research. However, there is no rapid method available to assess dentin moisture without sample destruction. This study examined the use of a digital grain moisture meter to measure root dentin moisture in vitro. Extracted mandibular single rooted teeth were sectioned at the CEJ. The moisture of the root dentin was measured at six measuring modes for different grains and repeated five times. Dentin weight changes before and after drying were measured to obtain control values. The control values were compared with machine readings. In conclusion, (1) Each non-destructive measurement took less than 30 seconds. (2) 24 hours storage at 37°C and 100 % humidity did not restore dentin moisture. (3) Five grain modes had a high validity, and could be used for dentin moisture measurements.

Research paper thumbnail of Comparison of the effect of two endodontic irrigation protocols on the elimination of bacteria from root canal system: a prospective, randomized clinical trial

Journal of endodontics, 2012

The purpose of this prospective, randomized clinical study was to compare the results of a nonact... more The purpose of this prospective, randomized clinical study was to compare the results of a nonactivated single-irrigation protocol (NAI) that used only 1% NaOCl with a passive ultrasonic multi-irrigation protocol (PUI) that used 1% NaOCl, 17% ethylenediaminetetraacetic acid, and 2% chlorhexidine in rendering canals bacteria free. In addition, the effect of a second-visit instrumentation after intra-appointment calcium hydroxide (CaOH(2)) was also evaluated in bacterial elimination. Fifty patients were recruited with a posterior tooth requiring primary endodontic treatment of apical periodontitis. Standard nonsurgical endodontic therapy was performed on both groups in a 2-visit approach by using calcium hydroxide intracanal medicament. Teeth were randomly treated with the NAI or PUI protocols in the first visit after complete instrumentation. Bacterial cultures were obtained at 4 periods during treatment from the canals: (1) before instrumentation, (2) after irrigation protocol, (3) ...

Research paper thumbnail of Influence of an apical negative pressure irrigation system on bacterial elimination during endodontic therapy: a prospective randomized clinical study

Journal of endodontics, 2012

Recent in vitro studies that use an apical negative pressure irrigation system, EndoVac, have dem... more Recent in vitro studies that use an apical negative pressure irrigation system, EndoVac, have demonstrated promising results in the production of debris-free root canals, while also preventing potential extrusion of irrigants into the periapical region. We conducted a randomized, controlled, prospective clinical study to determine whether the use of EndoVac irrigation (EndoVac group) was more efficient compared with standard needle irrigation (control group) in obtaining canals from which microbes could not be cultivated. Routine endodontic therapy was performed in 48 patients with necrotic, single-rooted, single-canal teeth. The patients were randomly assigned to either the EndoVac group (n = 25) or control group (n = 23). Irrigation with either method was carried out with 0.5% sodium hypochlorite. After surface disinfection, before instrumentation and on completion of chemomechanical preparation, intracanal microbial samples were obtained and cultured under anaerobic conditions. T...

Research paper thumbnail of Influence of a passive sonic irrigation system on the elimination of bacteria from root canal systems: a clinical study

Journal of endodontics, 2010

The present investigation evaluated the ability of a new passive sonic irrigation (sonic group) s... more The present investigation evaluated the ability of a new passive sonic irrigation (sonic group) system (EndoActivator) to eliminate cultivable bacteria from root canals in vivo and compared it with that of standard syringe irrigation (control group). Data were obtained by using bacteriologic sampling of root canals treated by endodontic residents. Sampling results from 1 session of treatment were then compared with results obtained after intervisit calcium hydroxide disinfection and a second session of treatment. There was no significant difference in the ability of sonic group and control group to eliminate cultivable bacteria from root canals (P > .05). A second session and intervisit calcium hydroxide disinfection were able to eliminate cultivable bacteria from significantly more teeth than a single session of treatment (P < .05). These in vivo results strengthen the case for a multi-visit approach to the treatment of apical periodontitis.

Research paper thumbnail of Cell and tissue reactions to mineral trioxide aggregate and Portland cement

Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics, 2003

Mineral trioxide aggregate (MTA) is being widely used for root-end fillings, pulp capping, perfor... more Mineral trioxide aggregate (MTA) is being widely used for root-end fillings, pulp capping, perforation repairs, and other endodontic procedures. MTA and Portland cement (PC) have many similar physical, chemical, and biologic properties. PC cement has shown promising potential as an endodontic material in several studies in vitro and in vivo. The purpose of this study was to compare the cytotoxic effect in vitro and the tissue reaction of MTA and Portland cement in bone implantation in the mandibles of guinea pigs. Millipore culture plate inserts with freshly mixed or set material were placed into the culture plates with already attached L929 cells. After an incubation period of 3 days, the cell morphology and cell counts were studied. Adult male guinea pigs under strict asepsis were anesthetized, during which a submandibular incision was made to expose the symphysis of the mandible. Bilateral bone cavities were prepared and Teflon applicators with freshly mixed materials were insert...

Research paper thumbnail of Influence of mixing vehicle on dissociation of calcium hydroxide in solution

Journal of endodontics, 2000

The antimicrobial effects of aqueous preparations of calcium hydroxide have been demonstrated in ... more The antimicrobial effects of aqueous preparations of calcium hydroxide have been demonstrated in the past. Calcium hydroxide, when dissolved in water, dissociates into hydroxide and calcium ions. The presence of hydroxide ions in a solution makes it antimicrobial. Recently it was shown that the use of glycerin as a mixing vehicle facilitates placement of calcium hydroxide in the root canals. The influence of nonaqueous mixing vehicles on the dissociation of calcium hydroxide is not clearly understood. In this study the conductivity of aqueous and nonaqueous solutions of calcium hydroxide was measured. The conductivity values for saturated solutions of calcium hydroxide in water was 7.3+/-3 mS/cm. The conductivity of calcium hydroxide in pure glycerin or propylene glycol was essentially zero. It was concluded that use of nonaqueous mixing vehicles may impede the effectiveness of calcium hydroxide as a root canal dressing.

Research paper thumbnail of Adherence of enamel matrix derivatives on root-end filling materials

Journal of endodontics, 1999

It was recently shown that application of enamel matrix derivatives (EMDs) on denuded root dentin... more It was recently shown that application of enamel matrix derivatives (EMDs) on denuded root dentin promotes periodontal regeneration. EMD is shown to adhere to the etched dentin, but its adherence to root-end filling materials is not known. The purpose of this study was to evaluate the adherence of a commercially available EMD product to root-end filling materials. Dentin sections were embedded in blocks made of acrylic resin. Cavities were prepared in similar acrylic resin blocks and were filled with amalgam, IRM, or composite resin. EMD was labeled with radioactive iodine and applied to the surfaces of the dentin sections, freshly made fillings, or acrylic resin controls. The specimens were rinsed, and the amount of radioactive iodine was determined in a gamma counter. Substantial amounts of EMD adhered to dentin sections. EMD adherence to amalgam and IRM was significantly less than to dentin or composite resin.

Research paper thumbnail of Tumor necrosis factor identified in periapical tissue exudates of teeth with apical periodontitis

Journal of endodontics, 1991

Root canal samples, taken from periapical tissue exudates during routine root canal treatment pro... more Root canal samples, taken from periapical tissue exudates during routine root canal treatment procedures, were processed for identification of tumor necrosis factor using a mouse anti-human monoclonal antibody and enzyme-linked immunosorbent assay. Detectable levels of tumor necrosis factor were identified in periapical tissue exudates in chronic apical periodontitis.

Research paper thumbnail of Decreased Bacterial Adherence and Biofilm Growth on Surfaces Coated with a Solution of Benzalkonium Chloride

Introduction: Secondary biofilm formation by oral bacteria after breakdown/fracture of temporary ... more Introduction: Secondary biofilm formation by oral bacteria after breakdown/fracture of temporary or permanent restorations imposes a challenge to the outcome of root canal treatment. This study focuses on benzalkonium chloride (BAK) coating on dentin or polystyrene surfaces and its influence on the early adhesion and biofilm formation by oral and root canal bacteria. Methods: Microbial adhesion and biofilm growth on surfaces coated with BAK were analyzed qualitatively with a dentin disk model and quantitatively with a mini-flow cell biofilm model. Cell viability and total biovolume were analyzed by the LIVE/DEAD technique. The repelling effect of surfaces coated with BAK was compared with NaOCl. Uncoated surfaces were used as controls. Results: Scanning electron microscope images in the dentin disk model revealed that very sparse biofilms were formed on NaOCl-and BAK-coated dentin surfaces. In contrast, biofilms formed on uncoated dentin were clearly visible as numerous irregularly distributed aggregates of rods and cocci. In the mini-flow cell system, confocal laser scanning microscope analysis confirmed that biofilms formed on NaOCl-and BAK-coated surfaces showed significantly less adhesion (2 hours) and biovolume accumulation (24 and 96 hours) compared with the uncoated controls (P < .01). Furthermore, cell viability assessments showed that on uncoated controls the viability measurements were high (>89%) as well as on BAK-coated surfaces (88% viable cells). However, cell viability was significantly reduced on NaOCl-coated surfaces (59% viable cells). Conclusions: This study illustrates that surface modification with a surfactant solution containing BAK does not cause cell membrane damage but might interfere with cell mechanisms of adhesion. Investigations into the clinical utility of BAK as an antibiofilm medication are warranted. (J Endod 2012;-:1-5)

Research paper thumbnail of Tissue lead levels in dogs with RC-2B root canal fillings

Journal of Endodontics, 1980

Research paper thumbnail of Levels of lead in blood of dogs with RC-2B root canal fillings

Journal of Endodontics, 1980

Research paper thumbnail of Application of Small Interfering RNA for Inhibition of Lipopolysaccharide-induced Osteoclast Formation and Cytokine Stimulation

Journal of Endodontics, 2008

RNA interference (RNAi) is a unique and powerful tool used for the study of gene function by supp... more RNA interference (RNAi) is a unique and powerful tool used for the study of gene function by suppressing its expression. Nuclear factor of activated T cells (NFATc1) is the most strongly induced transcription factor mediated by receptor activator for nuclear factor kappa B ligand stimulation and has shown to be a key regulator of osteoclastogenesis. To determine the application of small interfering RNA (siRNA) for inhibition of lipopolysaccharide (LPS)-induced cytokine stimulation and osteoclast formation, murine monocyte, RAW 264.7 cells as well as differentiated osteoclasts were transfected with NFATc1-specific siRNA and then stimulated with 100 ng/mL LPS. By using real-time polymerase chain reaction analysis and enzyme-linked immunosorbent assay, we confirmed that monocytes whose NFATc1 protein expression was silenced by using RNAi produced lower levels of inflammatory cytokines, fewer numbers evolved into mature osteoclasts, and osteoclasts expressed lower levels of osteoclast-specific gene markers such as tartrate-resistant acid phosphatase and cathepsin K. These results suggested that RNAi could be used to modulate the effects of LPS stimulation. (J Endod 2008;34:563-569)

Research paper thumbnail of Cytotoxic evaluation of root-end filling materials in cultures of human osteoblast-like cells and periodontal ligament cells

Journal of Endodontics, 1999

The cytotoxicity of three root-end filling materials (amalgam, IRM, and Super-EBA) was evaluated ... more The cytotoxicity of three root-end filling materials (amalgam, IRM, and Super-EBA) was evaluated in cultures of human periodontal ligament cells and human osteoblast-like cells. Ten-millimeter-long plastic test tubes were filled with 3 mm of freshly mixed root-end filling materials at one end (1.5 mm diameter). The opposite end was sealed and attached by heat to a 35-mm cell culture dish. Human periodontal ligament cells and human osteoblast-like cells were seeded in the dishes. The size of cell-free zones around the root-end filling materials and the total cell number per dish were calculated after 3 and 7 days. Empty test tubes used as controls did not influence the growth and distribution of the cultured cells. Cell density increased in all groups in the test period. Amalgam had a larger cell-free zone, compared with IRM and Super-EBA and showed a reduction in total cell number per dish for both tested cell types. IRM and Super-EBA also had a cell-free inhibition zone for both cell types, but no significant reduction in total cell number per dish. This study showed that amalgam had a higher cell toxicity to human periodontal ligament cells and human osteoblast-like cells than IRM and Super-EBA.

Research paper thumbnail of In vitro evaluation of biocompatibility and marginal adaptation of root retrofilling materials

Journal of Endodontics, 1988

Research paper thumbnail of Quantitative Analysis of Osteoclast-Specific Gene Markers Stimulated by Lipopolysaccharide

Journal of Endodontics, 2006

Lipopolysaccharide (LPS) in the outer layers of Gramnegative bacteria plays an important role in ... more Lipopolysaccharide (LPS) in the outer layers of Gramnegative bacteria plays an important role in initiating and sustaining periapical lesions. To understand the mechanisms of osteoclastic bone resorption in periapical lesions induced by LPS, we stimulated osteoclast precursors, RAW 264.7 cells with LPS. LPS stimulated osteoclastogenesis when osteoclast precursors were primed with activator for NF-B ligand (RANKL) as little as 24 h. By employing real-time PCR analysis, we have confirmed that osteoclast-like cells stimulated by LPS express high level of osteoclast-specific gene markers such as TRAP, cathepsin K, and calcitonin receptor. These results suggest that bone-resportive action by LPS is partially independent of RANKL. (J Endod 2006; 32:742-746)

Research paper thumbnail of Antifungal effects of sodium hypochlorite and chlorhexidine in root canals

Journal of Endodontics, 1999

The purpose of this study was to evaluate the antifungal properties of 0.12% chlorhexidine, 1% Na... more The purpose of this study was to evaluate the antifungal properties of 0.12% chlorhexidine, 1% NaOCI, and 5% NaOCI. Root sections were enlarged and the smear layer was removed in half of the specimens. The specimens were fixed in the wells of tissue culture plates. Each root canal was dispensed with an inoculum of Candida albicans. After 10 days, the root sections were treated with 3 ml of either disinfectant solution for I rain, 5 min, 30 min, and 1 h. Then, root sections were incubated in test tubes having Sabouraud's Dextrose Broth at 37°C for 24 h. In the presence of the smear layer, antifungal activity was observed only in 1-h treatment groups for all solutions. However, in the absence of the smear layer, 5% NaOCI alone started to show antifungal activity after 30 min. The antimicrobial effectiveness of irrigating solutions should be re-evaluated, particularly in patients predisposed to oral candidiasis.

Research paper thumbnail of Assessment of marginal stability and permeability of an interim restorative endodontic material

Oral Surgery, Oral Medicine, Oral Pathology, 1994

Research paper thumbnail of Dimensional changes of endodontic sealers

Oral Surgery, Oral Medicine, Oral Pathology, 1993

The purpose of this study was a long-term comparison of the dimensional changes of endodontic sea... more The purpose of this study was a long-term comparison of the dimensional changes of endodontic sealers of diverse properties. The sealers were injected as thin layers on the internal wails of glass pipettes 1 mm in diameter. The pipettes were filled with deionized water, and the water meniscus levels were recorded periodically up to 180 days. The water was removed from the pipettes, samples were allowed to dry, and the mass and the volume of the sealers were measured. AH26 and Endo-Fill had an initial expansion followed by a volumetric loss. The two zinc oxide eugenol-based sealers studied started to shrink within hours after mixing; the first volumetric loss for AH26 was recorded during the first 30 days and for Endo-Fill after 30 days, The least dimensional change at any time was observed for Endo-Fill. It was concluded that a significant dimensional change and continued volume loss can occur in some endodontic sealers

Research paper thumbnail of Root canal dentinal tubule disinfection

Journal of Endodontics, 1990

Dentinal tubules of the root canal walls of human teeth were infected in vitro with a known bacte... more Dentinal tubules of the root canal walls of human teeth were infected in vitro with a known bacterial isolate. The roots were exposed to either calcium hydroxide or iodine potassium-iodide for various periods of time and the viability of microorganisms was determined by incubation of entire root samples in a culture medium. The effects of the two agents on microbial viability were evaluated and compared. Iodine potassium-iodide disinfected dentin effectively. In contrast, bacteria remained viable in the dentin after relatively extended periods of calcium hydroxide treatment.

Research paper thumbnail of Particle size and shape of calcium hydroxide

The aim of this study was to examine the particle length, width, perimeter, and aspect ratio of c... more The aim of this study was to examine the particle length, width, perimeter, and aspect ratio of calcium hydroxide powder using a flow particle image analyzer (FPIA). Five sample groups each with 10mg calcium hydroxide were mixed with 15mL of alcohol and sonicated. Digital images of the particle samples were taken using the FPIA and analyzed with a one-way ANOVA. The overall averages ±S.D. among the five groups for particle length (μm), width (μm), perimeter (μm), and aspect ratio were 2.255±1.994, 1.620±1.464, 6.699±5.598, and 0.737±0.149, respectively. No statistical significance was observed among the groups for all parameters. When the total of 46,818 particles from all five groups were classified into the five length categories of 0.5μm increments, there were significant differences in width, perimeter, and aspect ratio (all p-values<0.0001). In conclusion, calcium hydroxide particles have a size and shape that may allow direct penetration into open dentin tubules.

Research paper thumbnail of A Rapid Non-destructive Method for Root Dentin Moisture Measurements

Dentin moisture content is important in adhesive bonding and structural strength research. Howeve... more Dentin moisture content is important in adhesive bonding and structural strength research. However, there is no rapid method available to assess dentin moisture without sample destruction. This study examined the use of a digital grain moisture meter to measure root dentin moisture in vitro. Extracted mandibular single rooted teeth were sectioned at the CEJ. The moisture of the root dentin was measured at six measuring modes for different grains and repeated five times. Dentin weight changes before and after drying were measured to obtain control values. The control values were compared with machine readings. In conclusion, (1) Each non-destructive measurement took less than 30 seconds. (2) 24 hours storage at 37°C and 100 % humidity did not restore dentin moisture. (3) Five grain modes had a high validity, and could be used for dentin moisture measurements.

Research paper thumbnail of Comparison of the effect of two endodontic irrigation protocols on the elimination of bacteria from root canal system: a prospective, randomized clinical trial

Journal of endodontics, 2012

The purpose of this prospective, randomized clinical study was to compare the results of a nonact... more The purpose of this prospective, randomized clinical study was to compare the results of a nonactivated single-irrigation protocol (NAI) that used only 1% NaOCl with a passive ultrasonic multi-irrigation protocol (PUI) that used 1% NaOCl, 17% ethylenediaminetetraacetic acid, and 2% chlorhexidine in rendering canals bacteria free. In addition, the effect of a second-visit instrumentation after intra-appointment calcium hydroxide (CaOH(2)) was also evaluated in bacterial elimination. Fifty patients were recruited with a posterior tooth requiring primary endodontic treatment of apical periodontitis. Standard nonsurgical endodontic therapy was performed on both groups in a 2-visit approach by using calcium hydroxide intracanal medicament. Teeth were randomly treated with the NAI or PUI protocols in the first visit after complete instrumentation. Bacterial cultures were obtained at 4 periods during treatment from the canals: (1) before instrumentation, (2) after irrigation protocol, (3) ...

Research paper thumbnail of Influence of an apical negative pressure irrigation system on bacterial elimination during endodontic therapy: a prospective randomized clinical study

Journal of endodontics, 2012

Recent in vitro studies that use an apical negative pressure irrigation system, EndoVac, have dem... more Recent in vitro studies that use an apical negative pressure irrigation system, EndoVac, have demonstrated promising results in the production of debris-free root canals, while also preventing potential extrusion of irrigants into the periapical region. We conducted a randomized, controlled, prospective clinical study to determine whether the use of EndoVac irrigation (EndoVac group) was more efficient compared with standard needle irrigation (control group) in obtaining canals from which microbes could not be cultivated. Routine endodontic therapy was performed in 48 patients with necrotic, single-rooted, single-canal teeth. The patients were randomly assigned to either the EndoVac group (n = 25) or control group (n = 23). Irrigation with either method was carried out with 0.5% sodium hypochlorite. After surface disinfection, before instrumentation and on completion of chemomechanical preparation, intracanal microbial samples were obtained and cultured under anaerobic conditions. T...

Research paper thumbnail of Influence of a passive sonic irrigation system on the elimination of bacteria from root canal systems: a clinical study

Journal of endodontics, 2010

The present investigation evaluated the ability of a new passive sonic irrigation (sonic group) s... more The present investigation evaluated the ability of a new passive sonic irrigation (sonic group) system (EndoActivator) to eliminate cultivable bacteria from root canals in vivo and compared it with that of standard syringe irrigation (control group). Data were obtained by using bacteriologic sampling of root canals treated by endodontic residents. Sampling results from 1 session of treatment were then compared with results obtained after intervisit calcium hydroxide disinfection and a second session of treatment. There was no significant difference in the ability of sonic group and control group to eliminate cultivable bacteria from root canals (P > .05). A second session and intervisit calcium hydroxide disinfection were able to eliminate cultivable bacteria from significantly more teeth than a single session of treatment (P < .05). These in vivo results strengthen the case for a multi-visit approach to the treatment of apical periodontitis.

Research paper thumbnail of Cell and tissue reactions to mineral trioxide aggregate and Portland cement

Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics, 2003

Mineral trioxide aggregate (MTA) is being widely used for root-end fillings, pulp capping, perfor... more Mineral trioxide aggregate (MTA) is being widely used for root-end fillings, pulp capping, perforation repairs, and other endodontic procedures. MTA and Portland cement (PC) have many similar physical, chemical, and biologic properties. PC cement has shown promising potential as an endodontic material in several studies in vitro and in vivo. The purpose of this study was to compare the cytotoxic effect in vitro and the tissue reaction of MTA and Portland cement in bone implantation in the mandibles of guinea pigs. Millipore culture plate inserts with freshly mixed or set material were placed into the culture plates with already attached L929 cells. After an incubation period of 3 days, the cell morphology and cell counts were studied. Adult male guinea pigs under strict asepsis were anesthetized, during which a submandibular incision was made to expose the symphysis of the mandible. Bilateral bone cavities were prepared and Teflon applicators with freshly mixed materials were insert...

Research paper thumbnail of Influence of mixing vehicle on dissociation of calcium hydroxide in solution

Journal of endodontics, 2000

The antimicrobial effects of aqueous preparations of calcium hydroxide have been demonstrated in ... more The antimicrobial effects of aqueous preparations of calcium hydroxide have been demonstrated in the past. Calcium hydroxide, when dissolved in water, dissociates into hydroxide and calcium ions. The presence of hydroxide ions in a solution makes it antimicrobial. Recently it was shown that the use of glycerin as a mixing vehicle facilitates placement of calcium hydroxide in the root canals. The influence of nonaqueous mixing vehicles on the dissociation of calcium hydroxide is not clearly understood. In this study the conductivity of aqueous and nonaqueous solutions of calcium hydroxide was measured. The conductivity values for saturated solutions of calcium hydroxide in water was 7.3+/-3 mS/cm. The conductivity of calcium hydroxide in pure glycerin or propylene glycol was essentially zero. It was concluded that use of nonaqueous mixing vehicles may impede the effectiveness of calcium hydroxide as a root canal dressing.

Research paper thumbnail of Adherence of enamel matrix derivatives on root-end filling materials

Journal of endodontics, 1999

It was recently shown that application of enamel matrix derivatives (EMDs) on denuded root dentin... more It was recently shown that application of enamel matrix derivatives (EMDs) on denuded root dentin promotes periodontal regeneration. EMD is shown to adhere to the etched dentin, but its adherence to root-end filling materials is not known. The purpose of this study was to evaluate the adherence of a commercially available EMD product to root-end filling materials. Dentin sections were embedded in blocks made of acrylic resin. Cavities were prepared in similar acrylic resin blocks and were filled with amalgam, IRM, or composite resin. EMD was labeled with radioactive iodine and applied to the surfaces of the dentin sections, freshly made fillings, or acrylic resin controls. The specimens were rinsed, and the amount of radioactive iodine was determined in a gamma counter. Substantial amounts of EMD adhered to dentin sections. EMD adherence to amalgam and IRM was significantly less than to dentin or composite resin.

Research paper thumbnail of Tumor necrosis factor identified in periapical tissue exudates of teeth with apical periodontitis

Journal of endodontics, 1991

Root canal samples, taken from periapical tissue exudates during routine root canal treatment pro... more Root canal samples, taken from periapical tissue exudates during routine root canal treatment procedures, were processed for identification of tumor necrosis factor using a mouse anti-human monoclonal antibody and enzyme-linked immunosorbent assay. Detectable levels of tumor necrosis factor were identified in periapical tissue exudates in chronic apical periodontitis.

Research paper thumbnail of Decreased Bacterial Adherence and Biofilm Growth on Surfaces Coated with a Solution of Benzalkonium Chloride

Introduction: Secondary biofilm formation by oral bacteria after breakdown/fracture of temporary ... more Introduction: Secondary biofilm formation by oral bacteria after breakdown/fracture of temporary or permanent restorations imposes a challenge to the outcome of root canal treatment. This study focuses on benzalkonium chloride (BAK) coating on dentin or polystyrene surfaces and its influence on the early adhesion and biofilm formation by oral and root canal bacteria. Methods: Microbial adhesion and biofilm growth on surfaces coated with BAK were analyzed qualitatively with a dentin disk model and quantitatively with a mini-flow cell biofilm model. Cell viability and total biovolume were analyzed by the LIVE/DEAD technique. The repelling effect of surfaces coated with BAK was compared with NaOCl. Uncoated surfaces were used as controls. Results: Scanning electron microscope images in the dentin disk model revealed that very sparse biofilms were formed on NaOCl-and BAK-coated dentin surfaces. In contrast, biofilms formed on uncoated dentin were clearly visible as numerous irregularly distributed aggregates of rods and cocci. In the mini-flow cell system, confocal laser scanning microscope analysis confirmed that biofilms formed on NaOCl-and BAK-coated surfaces showed significantly less adhesion (2 hours) and biovolume accumulation (24 and 96 hours) compared with the uncoated controls (P < .01). Furthermore, cell viability assessments showed that on uncoated controls the viability measurements were high (>89%) as well as on BAK-coated surfaces (88% viable cells). However, cell viability was significantly reduced on NaOCl-coated surfaces (59% viable cells). Conclusions: This study illustrates that surface modification with a surfactant solution containing BAK does not cause cell membrane damage but might interfere with cell mechanisms of adhesion. Investigations into the clinical utility of BAK as an antibiofilm medication are warranted. (J Endod 2012;-:1-5)

Research paper thumbnail of Tissue lead levels in dogs with RC-2B root canal fillings

Journal of Endodontics, 1980

Research paper thumbnail of Levels of lead in blood of dogs with RC-2B root canal fillings

Journal of Endodontics, 1980

Research paper thumbnail of Application of Small Interfering RNA for Inhibition of Lipopolysaccharide-induced Osteoclast Formation and Cytokine Stimulation

Journal of Endodontics, 2008

RNA interference (RNAi) is a unique and powerful tool used for the study of gene function by supp... more RNA interference (RNAi) is a unique and powerful tool used for the study of gene function by suppressing its expression. Nuclear factor of activated T cells (NFATc1) is the most strongly induced transcription factor mediated by receptor activator for nuclear factor kappa B ligand stimulation and has shown to be a key regulator of osteoclastogenesis. To determine the application of small interfering RNA (siRNA) for inhibition of lipopolysaccharide (LPS)-induced cytokine stimulation and osteoclast formation, murine monocyte, RAW 264.7 cells as well as differentiated osteoclasts were transfected with NFATc1-specific siRNA and then stimulated with 100 ng/mL LPS. By using real-time polymerase chain reaction analysis and enzyme-linked immunosorbent assay, we confirmed that monocytes whose NFATc1 protein expression was silenced by using RNAi produced lower levels of inflammatory cytokines, fewer numbers evolved into mature osteoclasts, and osteoclasts expressed lower levels of osteoclast-specific gene markers such as tartrate-resistant acid phosphatase and cathepsin K. These results suggested that RNAi could be used to modulate the effects of LPS stimulation. (J Endod 2008;34:563-569)

Research paper thumbnail of Cytotoxic evaluation of root-end filling materials in cultures of human osteoblast-like cells and periodontal ligament cells

Journal of Endodontics, 1999

The cytotoxicity of three root-end filling materials (amalgam, IRM, and Super-EBA) was evaluated ... more The cytotoxicity of three root-end filling materials (amalgam, IRM, and Super-EBA) was evaluated in cultures of human periodontal ligament cells and human osteoblast-like cells. Ten-millimeter-long plastic test tubes were filled with 3 mm of freshly mixed root-end filling materials at one end (1.5 mm diameter). The opposite end was sealed and attached by heat to a 35-mm cell culture dish. Human periodontal ligament cells and human osteoblast-like cells were seeded in the dishes. The size of cell-free zones around the root-end filling materials and the total cell number per dish were calculated after 3 and 7 days. Empty test tubes used as controls did not influence the growth and distribution of the cultured cells. Cell density increased in all groups in the test period. Amalgam had a larger cell-free zone, compared with IRM and Super-EBA and showed a reduction in total cell number per dish for both tested cell types. IRM and Super-EBA also had a cell-free inhibition zone for both cell types, but no significant reduction in total cell number per dish. This study showed that amalgam had a higher cell toxicity to human periodontal ligament cells and human osteoblast-like cells than IRM and Super-EBA.

Research paper thumbnail of In vitro evaluation of biocompatibility and marginal adaptation of root retrofilling materials

Journal of Endodontics, 1988

Research paper thumbnail of Quantitative Analysis of Osteoclast-Specific Gene Markers Stimulated by Lipopolysaccharide

Journal of Endodontics, 2006

Lipopolysaccharide (LPS) in the outer layers of Gramnegative bacteria plays an important role in ... more Lipopolysaccharide (LPS) in the outer layers of Gramnegative bacteria plays an important role in initiating and sustaining periapical lesions. To understand the mechanisms of osteoclastic bone resorption in periapical lesions induced by LPS, we stimulated osteoclast precursors, RAW 264.7 cells with LPS. LPS stimulated osteoclastogenesis when osteoclast precursors were primed with activator for NF-B ligand (RANKL) as little as 24 h. By employing real-time PCR analysis, we have confirmed that osteoclast-like cells stimulated by LPS express high level of osteoclast-specific gene markers such as TRAP, cathepsin K, and calcitonin receptor. These results suggest that bone-resportive action by LPS is partially independent of RANKL. (J Endod 2006; 32:742-746)

Research paper thumbnail of Antifungal effects of sodium hypochlorite and chlorhexidine in root canals

Journal of Endodontics, 1999

The purpose of this study was to evaluate the antifungal properties of 0.12% chlorhexidine, 1% Na... more The purpose of this study was to evaluate the antifungal properties of 0.12% chlorhexidine, 1% NaOCI, and 5% NaOCI. Root sections were enlarged and the smear layer was removed in half of the specimens. The specimens were fixed in the wells of tissue culture plates. Each root canal was dispensed with an inoculum of Candida albicans. After 10 days, the root sections were treated with 3 ml of either disinfectant solution for I rain, 5 min, 30 min, and 1 h. Then, root sections were incubated in test tubes having Sabouraud's Dextrose Broth at 37°C for 24 h. In the presence of the smear layer, antifungal activity was observed only in 1-h treatment groups for all solutions. However, in the absence of the smear layer, 5% NaOCI alone started to show antifungal activity after 30 min. The antimicrobial effectiveness of irrigating solutions should be re-evaluated, particularly in patients predisposed to oral candidiasis.

Research paper thumbnail of Assessment of marginal stability and permeability of an interim restorative endodontic material

Oral Surgery, Oral Medicine, Oral Pathology, 1994

Research paper thumbnail of Dimensional changes of endodontic sealers

Oral Surgery, Oral Medicine, Oral Pathology, 1993

The purpose of this study was a long-term comparison of the dimensional changes of endodontic sea... more The purpose of this study was a long-term comparison of the dimensional changes of endodontic sealers of diverse properties. The sealers were injected as thin layers on the internal wails of glass pipettes 1 mm in diameter. The pipettes were filled with deionized water, and the water meniscus levels were recorded periodically up to 180 days. The water was removed from the pipettes, samples were allowed to dry, and the mass and the volume of the sealers were measured. AH26 and Endo-Fill had an initial expansion followed by a volumetric loss. The two zinc oxide eugenol-based sealers studied started to shrink within hours after mixing; the first volumetric loss for AH26 was recorded during the first 30 days and for Endo-Fill after 30 days, The least dimensional change at any time was observed for Endo-Fill. It was concluded that a significant dimensional change and continued volume loss can occur in some endodontic sealers

Research paper thumbnail of Root canal dentinal tubule disinfection

Journal of Endodontics, 1990

Dentinal tubules of the root canal walls of human teeth were infected in vitro with a known bacte... more Dentinal tubules of the root canal walls of human teeth were infected in vitro with a known bacterial isolate. The roots were exposed to either calcium hydroxide or iodine potassium-iodide for various periods of time and the viability of microorganisms was determined by incubation of entire root samples in a culture medium. The effects of the two agents on microbial viability were evaluated and compared. Iodine potassium-iodide disinfected dentin effectively. In contrast, bacteria remained viable in the dentin after relatively extended periods of calcium hydroxide treatment.

Research paper thumbnail of Particle size and shape of calcium hydroxide

The aim of this study was to examine the particle length, width, perimeter, and aspect ratio of c... more The aim of this study was to examine the particle length, width, perimeter, and aspect ratio of calcium hydroxide powder using a flow particle image analyzer (FPIA). Five sample groups each with 10mg calcium hydroxide were mixed with 15mL of alcohol and sonicated. Digital images of the particle samples were taken using the FPIA and analyzed with a one-way ANOVA. The overall averages ±S.D. among the five groups for particle length (μm), width (μm), perimeter (μm), and aspect ratio were 2.255±1.994, 1.620±1.464, 6.699±5.598, and 0.737±0.149, respectively. No statistical significance was observed among the groups for all parameters. When the total of 46,818 particles from all five groups were classified into the five length categories of 0.5μm increments, there were significant differences in width, perimeter, and aspect ratio (all p-values<0.0001). In conclusion, calcium hydroxide particles have a size and shape that may allow direct penetration into open dentin tubules.