Maxillary bone loss impairs essential functions (chewing, swallowing, speech) and gives patients a very unaesthetic appearance due to the removal of facial support tissues, leading to serious psychological consequence...Maxillary bone loss impairs essential functions (chewing, swallowing, speech) and gives patients a very unaesthetic appearance due to the removal of facial support tissues, leading to serious psychological consequences. Treatment is multidisciplinary and requires a resective surgery if the cause is tumor-related, or an additive surgery if the cause is traumatic. This article aims to show the role of making a prosthesis to restore function (chewing, swallowing, speech) and aesthetics following maxillary bone loss. We will eighter present a clinical case involving a right maxillary tumor that was surgically resected followed by radiotherapy, and subsequently rehabilitated with a maxillofacial prosthesis in the consultation and dental treatment center of the university hospital center of Casablanca.展开更多
We previously studied the mechanism underlying the adsorption of oral bacteria on the surfaces of dental prosthetic materials such as ceramics and resins in vitro. The aim of the present study was to examine bovine se...We previously studied the mechanism underlying the adsorption of oral bacteria on the surfaces of dental prosthetic materials such as ceramics and resins in vitro. The aim of the present study was to examine bovine serum albumin (BSA) adsorption on crown composite resin surfaces by means of zeta potential. We measured the zeta potentials of resins alone, BSA alone, and resins after BSA adsorption. Eight resins were pulverized into powders (300 - 1000 nm). All experiments were conducted in 10 mM sodium chloride solution (pH 6.5). BSA was dissolved in 10 mM NaCl with a concentration of 2.0 × 10-5 mol/l. An adsorption assay was performed for one hour at 37°C under continuous rotation (6 rpm). The zeta potentials of both resins and BSA were negative, with BSA itself less negative than the resins themselves as an absolute value (p < 0.0001). The zeta potentials of seven resin surfaces after BSA adsorption were significantly less negative than were those of the resins without BSA adsorption (p < 0.0001). Eight resins were divided into two classes based on the size of the surface potential difference between each resin and the BSA. The difference in surface potential between the resins and the BSA were small, leading to the theory that particles with identical charges repulse each other, and the amounts of adsorbed BSA on these resins might be less. On the other, when the differences between the other resins and BSA are large, so that the repulsive force between two nonidentical particles becomes zero and an attractive force might be generated, then more BSA might be adsorbed on those resins. Therefore, the zeta potentials were affected by BSA adsorption and became less negative. These results suggested that electrostatic interactions play an important role in the adsorption of BSA on resin surfaces.展开更多
Aim: Both conventional and flexible resins may show color alteration due to intrinsic and extrinsic factors. The aim of this study was to evaluate the color changes of the polyamid and heat polymerized acrylic denture...Aim: Both conventional and flexible resins may show color alteration due to intrinsic and extrinsic factors. The aim of this study was to evaluate the color changes of the polyamid and heat polymerized acrylic denture base materials in storage of different staining solutions. Methods: Two denture base materials were used in this study. The speciemens were stored in two staining solutions (tea, coffee), distilled water and denture cleaner. For each group, 14 speciemens (25 × 15 × 2.5 mm) were prepared. The color of speciemens was measured using a colorimeter according to the CIE L*a*b* color scale. The color changes of speciemens were evaluated before and after 7 and 30 days. All data recorded were taken by the same investigator to minimize inconstancy of technique. The data were analyzed statistically by repeated measures analysis of variance and Tukey honestly significant difference multiple comparison tests. It was found no statistically significant difference between solutions (P > 0.05). Results: Polyamid denture base resin displayed the greatest colour change when compared to polymetyhl methacrylate denture base resin (P < 0.001). Polyamid material indicated the highest value (ΔE: 7.28) in coffee solution for 7 days. Significance: The colour stability of polymetyhl methacrylate denture base resin is greater than polyamid denture base resin.展开更多
In this overview, we discuss the impact of antibiotic therapy on the COVID infection, the complications after vaccination, possible causes of adverse events, and ways to protect against pandemic infection, as well as ...In this overview, we discuss the impact of antibiotic therapy on the COVID infection, the complications after vaccination, possible causes of adverse events, and ways to protect against pandemic infection, as well as try to dispel myths about COVID. Antibiotics are necessary only in case of secondary infection, but overlapping with bacterial infection mainly occurs after hospitalization, and the vast majority of infections were caused by the Acinetobacter baumannii strain. Commonly used antimicrobial disinfectants are chlorhexidine derivatives;due to their frequent use, microorganisms have become resistant to them, and in addition, chloroquine has no clinical benefit in the treatment of COVID-19. Virus escapes from the immune response due to multiple mutations in the receptor-binding domain, or the N-terminal end, which are the sites responsible for antibody binding and virus neutralization. The COVID infection itself is characterized by a rather powerful suppression of immunity. For this reason, the use of antibiotics in the absence of a secondary infection layer leads to greater suppression of the immune system and an aggravation of the process, which often ends up fatally. Immune dysregulation predisposes to the development of severe COVID-19. A decrease in the number of leukocytes gives an unfavorable prognosis for the severity of the COVID infection course. The main reason for the death cases after vaccination seems to be an increase in blood clotting, which is observed not only among the population over 60 years old, but also amid young people.展开更多
Poly （methyl methacrylate） is widely used as denture base material. During fabrication of a denture, the physical and mechanical properties are influenced by cure condition. Each cure cycle or fabrication technique ...Poly （methyl methacrylate） is widely used as denture base material. During fabrication of a denture, the physical and mechanical properties are influenced by cure condition. Each cure cycle or fabrication technique is attempts to optimize the properties for a given application. The aim of this study was to compare two types of commercially available denture base materials （heat-cure and self-cure） in their mechanical properties. The samples were prepared according to the daily routine work for sample preparation in dental laboratories. After reaching dough stage the mix packed into dumbbell shaped of stainless steel mould and pressed in a hydraulic bench press for 25 mins at room temperature. For heat cure the polymerization cycle was carried out using water bath, while self cure was done at room temperature. The impact strength was evaluated using Charpy impact test. The hardness test was conducted using a calibrated Vickers hardness tester machine. The lowest impact strength was observed in self-cure denture base material （self cure material 6.2 kJ/m^2 while heat cure 12.69 kJ/m^2. It appears that the tendency of heat cure to fracture was lower than self-cure denture base materials. Heat cure denture base material has significantly higher hardness test values than self-cure denture base material. The observed VHN value of the heat-cure was 20.09 g/mm^2 while the self-cure value was 12.7 g/mm^2. This is may be due to the plasticizer effect of residual monomer which was higher in self curing material as reported in previous work. Generally, the heat cure material showed better properties compared to self cure material.展开更多
The oral rehabilitation of edentulous patients can be done in different ways depending on the alveolar ridge morphology and patient expectations. The objective of this clinical case was to report prosthetic and functi...The oral rehabilitation of edentulous patients can be done in different ways depending on the alveolar ridge morphology and patient expectations. The objective of this clinical case was to report prosthetic and functional adaptation difficulties when conventional complete denture was changed to a zygomatic implant-supported prosthesis. We report a 52-year-old male singer with an atrophic maxilla who was rehabilitated with zygomatic implant-supported prosthesis using 4 implants. However, the thickness of the prosthesis in the palatal region and the space between the prosthesis and soft tissue caused difficulty in speaking and singing. The palatal region of the prosthesis was trimmed and the anterior region of the prosthesis was relined. These procedures were performed to make room for the tongue and minimize the passage of air during speech. Adaptations in the shape of the prosthesis must be made to enable its use, without compromising its strength.展开更多
Based on the findings of epidemiological surveys in western countries, the number of person with suspected xerostomia in Japan is estimated to be 30,000,000. Xerostomia is caused by: 1) Systemic diseases;2) Medication...Based on the findings of epidemiological surveys in western countries, the number of person with suspected xerostomia in Japan is estimated to be 30,000,000. Xerostomia is caused by: 1) Systemic diseases;2) Medications;3) Tumors or trauma;4) Radiotherapy;and 5) Neurological factors. Its symptoms can be alleviated, and its progression can be stopped by close cooperation between the dental and medical departments. However, at present, symptomatic treatment methods such as water drinking, oral rinsing with water, and administration of Kampo medicines or parasymptomimetic drugs are mainly used, and a standard treatment has not been established. On the other hand, previous studies on xerostomia have reported improvement in dry mouth symptoms using dental approaches or a relationship between the development of candidiasis and the salivary flow rate. Therefore, in this study, to establish a dental method useful for improving xerostomia associated with systemic diseases and medications for them, we restored occlusal function, and as a result, increased the salivary flow rate, and evaluated changes in oral findings.展开更多
The aim of this study was to evaluate the effect of chewing simulation on wear of artificial enamel abraded against zirconia-based crowns. Fifteen crown preparations were scanned for the manufacturing of crowns using ...The aim of this study was to evaluate the effect of chewing simulation on wear of artificial enamel abraded against zirconia-based crowns. Fifteen crown preparations were scanned for the manufacturing of crowns using computer-aided-design/computer-aided-machining technique (CAD/CAM), according to the following (n = 5): Polished (PM) and glazed (GM) monolithic zirconia (1.5 mm uniform thickness), and Bilayer (BL - 0.8 mm zirconia coping, 0.7 mm porcelain veneer) crowns. The samples were cemented and chewing simulation (2.5 million cycles/0-80N/artificial saliva/37°C) was performed with steatite indenters (6 mm diameter) as antagonists. Assuming the uniformity of the unaged samples, antagonists were scanned using a surface profilometer and the material loss volume was calculated. Roughness of the crowns’ occlusal surface was also analyzed using the profilometer. Scanning electron microscopy was used to characterize the abraded surface. One-way ANOVA and Tukey test (p = 0.05) were employed for analysis of wear results. A significant difference was observed among the groups (p 3 ± 0.015) than those abraded against monolithic zirconia, polished (PM - 0.167 mm3 ± 0.02) and glazed (0.101 mm3 ± 0.03), which were similar to each other. Veneering porcelain results in more pronounced wear of the artificial enamel than monolithic zirconia. However, mastication against monolithic Y-TZP also imposes wear to the opposing teeth.展开更多
Aim: The aim of this study was to evaluate the effects of different solutions on the flexural strength of one methacrylate-based resin and three bis-acryl resin provisional materials using an in vitro model test syste...Aim: The aim of this study was to evaluate the effects of different solutions on the flexural strength of one methacrylate-based resin and three bis-acryl resin provisional materials using an in vitro model test system. Methods: The specimens (25 × 2 × 2 mm) were prepared from interim materials and stored for 14 days at 37°C in different solutions (coffee, burn, cola) and distilled water (control group). A standard three-point bending test was conducted on the specimens with an Instron universal testing machine at crosshead speed of 0.5 mm/min. Data were analyzed using the one-way analysis of variance and Tukey HSD multiple comprasion tests. Results: The methacry-late-based resin (Takilon) showed the least fracture strength (61.6 - 85.6 MPa). One of the bis-acryl resins (Protemp 4-3M ESPE) showed the highest fracture strength (112 - 128 MPa). Conclusions: All bis-acryl resin composite materials exhibited high fracture strength over the traditional methyl methacrylate resin throughout the 14 day time interval of investigation. The different solutions have not statistically significant effect on the flexure strength values on four temporary materials.展开更多
The aim of this study is to clarify the effect of different concentrations of titanium dioxide nanoparticles (Nps) on the properties of two types of heat polymerized acrylic resin. The tested parameters were flexural ...The aim of this study is to clarify the effect of different concentrations of titanium dioxide nanoparticles (Nps) on the properties of two types of heat polymerized acrylic resin. The tested parameters were flexural strength, impact strength, and microhardness. The two types of acrylic resin used in this study were conventional unmodified (Implacryl, Vertex) and high impact heat polymerized acrylic resin (Vertex-Dental, Netherlands). Both types of acrylic resin were modified by using 1% and 5% TiO<sub>2</sub> Nps powder. Specimen’s dimensions were prepared according to the American Dental Association Specification No. 12. Three types of specimens were prepared: 1) flexural strength specimens 50 mm × 10 (±0.2) mm × 3 (±0.2) mm, 2) impact strength test specimens 60 mm × 6.0 mm × 4.0 mm, 3) microhardnesss specimens 25 mm × 10 mm × 3 (±0.2) mm. For each test 6 groups were prepared (each group containing 5 samples). Thirty specimens were prepared in each of the three tests, amounting to a total number of 90 specimens. Mechanical properties such as flexural strength (FS), impact strength and microhardness of the above mentioned specimens were determined using universal testing machine, Izod pendulum impact testing machine and Vickers microhardness tester, respectively. ISO Specification No. 1567 was followed in microhardness test. The data was collected and statistically analyzed. Flexural strength considerably decreased by increasing TiO<sub>2</sub> concentration in both types of acrylic resin. Impact strength of the conventional acrylic resin modified by 1% of additives significantly increased. The microhardness is significantly increased by addition of 5% of TiO<sub>2</sub> Nps. The Incorporation of TiO<sub>2</sub> nanoparticles into acrylic resins can adversely affect its flexural strength. Meanwhile, the impact strength can be modified by small percentage of additives (abt. 1%). This effect is directly correlated with the concentration of nanoparticles. On the other hand, concentrations of TiO<sub>2</sub> Nps (abt. 5%) positively affect the microhardness of both types of acrylic resin used in the present study.</sub></sub></sub></sub></sub></sub></sub></sub></sub></sub>展开更多
The persistence of bacteria in the root canal system is the primary cause of recurrent apical periodontitis.The adaptability of residual bacteria to changing environmental conditions is a key survival strategy of biof...The persistence of bacteria in the root canal system is the primary cause of recurrent apical periodontitis.The adaptability of residual bacteria to changing environmental conditions is a key survival strategy of biofilms,often leading to endodontic treatment failure.DJK-5 is a protease-resistant,broad-spectrum D-enantiomeric peptide that degrades or prevents the accumulation of guanosine penta-and tetraphosphates,which are important for biofilm formation.We evaluated the effects of primary antimicrobial agents and nutrient conditions on the re-covery,metabolism,diversity,and composition of oral biofilms,and investigated how these factors affect the efficacy of DJK-5 and chlorhexidine(CHX)during re-exposure.Primary irrigants and nutrient conditions significantly influenced biofilm recovery,metabolic activity,diversity,and composition.Biofilm recovery was slower in nutrient-poor groups compared to nutrient-rich ones,and nutrient availability had the greatest effect on shaping both the diversity and composition of the biofilms.Water and DJK-5 groups showed similar biofilm diversity trends,while CHX generally led to lower diversity.Results indicate that primary irrigants and nutrient conditions significantly impact biofilm composition,diversity,and recovery.However,these changes did not compromise DJK-5’s effectiveness in killing of biofilm microbes during re-exposure of recovered biofilms.展开更多
文摘Maxillary bone loss impairs essential functions (chewing, swallowing, speech) and gives patients a very unaesthetic appearance due to the removal of facial support tissues, leading to serious psychological consequences. Treatment is multidisciplinary and requires a resective surgery if the cause is tumor-related, or an additive surgery if the cause is traumatic. This article aims to show the role of making a prosthesis to restore function (chewing, swallowing, speech) and aesthetics following maxillary bone loss. We will eighter present a clinical case involving a right maxillary tumor that was surgically resected followed by radiotherapy, and subsequently rehabilitated with a maxillofacial prosthesis in the consultation and dental treatment center of the university hospital center of Casablanca.
文摘We previously studied the mechanism underlying the adsorption of oral bacteria on the surfaces of dental prosthetic materials such as ceramics and resins in vitro. The aim of the present study was to examine bovine serum albumin (BSA) adsorption on crown composite resin surfaces by means of zeta potential. We measured the zeta potentials of resins alone, BSA alone, and resins after BSA adsorption. Eight resins were pulverized into powders (300 - 1000 nm). All experiments were conducted in 10 mM sodium chloride solution (pH 6.5). BSA was dissolved in 10 mM NaCl with a concentration of 2.0 × 10-5 mol/l. An adsorption assay was performed for one hour at 37°C under continuous rotation (6 rpm). The zeta potentials of both resins and BSA were negative, with BSA itself less negative than the resins themselves as an absolute value (p < 0.0001). The zeta potentials of seven resin surfaces after BSA adsorption were significantly less negative than were those of the resins without BSA adsorption (p < 0.0001). Eight resins were divided into two classes based on the size of the surface potential difference between each resin and the BSA. The difference in surface potential between the resins and the BSA were small, leading to the theory that particles with identical charges repulse each other, and the amounts of adsorbed BSA on these resins might be less. On the other, when the differences between the other resins and BSA are large, so that the repulsive force between two nonidentical particles becomes zero and an attractive force might be generated, then more BSA might be adsorbed on those resins. Therefore, the zeta potentials were affected by BSA adsorption and became less negative. These results suggested that electrostatic interactions play an important role in the adsorption of BSA on resin surfaces.
基金supported financially by the Department of Scientific Research Projects of Ataturk University(Project No.2003/158)and(Project no.2010/141).
文摘Aim: Both conventional and flexible resins may show color alteration due to intrinsic and extrinsic factors. The aim of this study was to evaluate the color changes of the polyamid and heat polymerized acrylic denture base materials in storage of different staining solutions. Methods: Two denture base materials were used in this study. The speciemens were stored in two staining solutions (tea, coffee), distilled water and denture cleaner. For each group, 14 speciemens (25 × 15 × 2.5 mm) were prepared. The color of speciemens was measured using a colorimeter according to the CIE L*a*b* color scale. The color changes of speciemens were evaluated before and after 7 and 30 days. All data recorded were taken by the same investigator to minimize inconstancy of technique. The data were analyzed statistically by repeated measures analysis of variance and Tukey honestly significant difference multiple comparison tests. It was found no statistically significant difference between solutions (P > 0.05). Results: Polyamid denture base resin displayed the greatest colour change when compared to polymetyhl methacrylate denture base resin (P < 0.001). Polyamid material indicated the highest value (ΔE: 7.28) in coffee solution for 7 days. Significance: The colour stability of polymetyhl methacrylate denture base resin is greater than polyamid denture base resin.
文摘In this overview, we discuss the impact of antibiotic therapy on the COVID infection, the complications after vaccination, possible causes of adverse events, and ways to protect against pandemic infection, as well as try to dispel myths about COVID. Antibiotics are necessary only in case of secondary infection, but overlapping with bacterial infection mainly occurs after hospitalization, and the vast majority of infections were caused by the Acinetobacter baumannii strain. Commonly used antimicrobial disinfectants are chlorhexidine derivatives;due to their frequent use, microorganisms have become resistant to them, and in addition, chloroquine has no clinical benefit in the treatment of COVID-19. Virus escapes from the immune response due to multiple mutations in the receptor-binding domain, or the N-terminal end, which are the sites responsible for antibody binding and virus neutralization. The COVID infection itself is characterized by a rather powerful suppression of immunity. For this reason, the use of antibiotics in the absence of a secondary infection layer leads to greater suppression of the immune system and an aggravation of the process, which often ends up fatally. Immune dysregulation predisposes to the development of severe COVID-19. A decrease in the number of leukocytes gives an unfavorable prognosis for the severity of the COVID infection course. The main reason for the death cases after vaccination seems to be an increase in blood clotting, which is observed not only among the population over 60 years old, but also amid young people.
文摘Poly （methyl methacrylate） is widely used as denture base material. During fabrication of a denture, the physical and mechanical properties are influenced by cure condition. Each cure cycle or fabrication technique is attempts to optimize the properties for a given application. The aim of this study was to compare two types of commercially available denture base materials （heat-cure and self-cure） in their mechanical properties. The samples were prepared according to the daily routine work for sample preparation in dental laboratories. After reaching dough stage the mix packed into dumbbell shaped of stainless steel mould and pressed in a hydraulic bench press for 25 mins at room temperature. For heat cure the polymerization cycle was carried out using water bath, while self cure was done at room temperature. The impact strength was evaluated using Charpy impact test. The hardness test was conducted using a calibrated Vickers hardness tester machine. The lowest impact strength was observed in self-cure denture base material （self cure material 6.2 kJ/m^2 while heat cure 12.69 kJ/m^2. It appears that the tendency of heat cure to fracture was lower than self-cure denture base materials. Heat cure denture base material has significantly higher hardness test values than self-cure denture base material. The observed VHN value of the heat-cure was 20.09 g/mm^2 while the self-cure value was 12.7 g/mm^2. This is may be due to the plasticizer effect of residual monomer which was higher in self curing material as reported in previous work. Generally, the heat cure material showed better properties compared to self cure material.
文摘The oral rehabilitation of edentulous patients can be done in different ways depending on the alveolar ridge morphology and patient expectations. The objective of this clinical case was to report prosthetic and functional adaptation difficulties when conventional complete denture was changed to a zygomatic implant-supported prosthesis. We report a 52-year-old male singer with an atrophic maxilla who was rehabilitated with zygomatic implant-supported prosthesis using 4 implants. However, the thickness of the prosthesis in the palatal region and the space between the prosthesis and soft tissue caused difficulty in speaking and singing. The palatal region of the prosthesis was trimmed and the anterior region of the prosthesis was relined. These procedures were performed to make room for the tongue and minimize the passage of air during speech. Adaptations in the shape of the prosthesis must be made to enable its use, without compromising its strength.
文摘Based on the findings of epidemiological surveys in western countries, the number of person with suspected xerostomia in Japan is estimated to be 30,000,000. Xerostomia is caused by: 1) Systemic diseases;2) Medications;3) Tumors or trauma;4) Radiotherapy;and 5) Neurological factors. Its symptoms can be alleviated, and its progression can be stopped by close cooperation between the dental and medical departments. However, at present, symptomatic treatment methods such as water drinking, oral rinsing with water, and administration of Kampo medicines or parasymptomimetic drugs are mainly used, and a standard treatment has not been established. On the other hand, previous studies on xerostomia have reported improvement in dry mouth symptoms using dental approaches or a relationship between the development of candidiasis and the salivary flow rate. Therefore, in this study, to establish a dental method useful for improving xerostomia associated with systemic diseases and medications for them, we restored occlusal function, and as a result, increased the salivary flow rate, and evaluated changes in oral findings.
文摘The aim of this study was to evaluate the effect of chewing simulation on wear of artificial enamel abraded against zirconia-based crowns. Fifteen crown preparations were scanned for the manufacturing of crowns using computer-aided-design/computer-aided-machining technique (CAD/CAM), according to the following (n = 5): Polished (PM) and glazed (GM) monolithic zirconia (1.5 mm uniform thickness), and Bilayer (BL - 0.8 mm zirconia coping, 0.7 mm porcelain veneer) crowns. The samples were cemented and chewing simulation (2.5 million cycles/0-80N/artificial saliva/37°C) was performed with steatite indenters (6 mm diameter) as antagonists. Assuming the uniformity of the unaged samples, antagonists were scanned using a surface profilometer and the material loss volume was calculated. Roughness of the crowns’ occlusal surface was also analyzed using the profilometer. Scanning electron microscopy was used to characterize the abraded surface. One-way ANOVA and Tukey test (p = 0.05) were employed for analysis of wear results. A significant difference was observed among the groups (p 3 ± 0.015) than those abraded against monolithic zirconia, polished (PM - 0.167 mm3 ± 0.02) and glazed (0.101 mm3 ± 0.03), which were similar to each other. Veneering porcelain results in more pronounced wear of the artificial enamel than monolithic zirconia. However, mastication against monolithic Y-TZP also imposes wear to the opposing teeth.
文摘Aim: The aim of this study was to evaluate the effects of different solutions on the flexural strength of one methacrylate-based resin and three bis-acryl resin provisional materials using an in vitro model test system. Methods: The specimens (25 × 2 × 2 mm) were prepared from interim materials and stored for 14 days at 37°C in different solutions (coffee, burn, cola) and distilled water (control group). A standard three-point bending test was conducted on the specimens with an Instron universal testing machine at crosshead speed of 0.5 mm/min. Data were analyzed using the one-way analysis of variance and Tukey HSD multiple comprasion tests. Results: The methacry-late-based resin (Takilon) showed the least fracture strength (61.6 - 85.6 MPa). One of the bis-acryl resins (Protemp 4-3M ESPE) showed the highest fracture strength (112 - 128 MPa). Conclusions: All bis-acryl resin composite materials exhibited high fracture strength over the traditional methyl methacrylate resin throughout the 14 day time interval of investigation. The different solutions have not statistically significant effect on the flexure strength values on four temporary materials.
文摘The aim of this study is to clarify the effect of different concentrations of titanium dioxide nanoparticles (Nps) on the properties of two types of heat polymerized acrylic resin. The tested parameters were flexural strength, impact strength, and microhardness. The two types of acrylic resin used in this study were conventional unmodified (Implacryl, Vertex) and high impact heat polymerized acrylic resin (Vertex-Dental, Netherlands). Both types of acrylic resin were modified by using 1% and 5% TiO<sub>2</sub> Nps powder. Specimen’s dimensions were prepared according to the American Dental Association Specification No. 12. Three types of specimens were prepared: 1) flexural strength specimens 50 mm × 10 (±0.2) mm × 3 (±0.2) mm, 2) impact strength test specimens 60 mm × 6.0 mm × 4.0 mm, 3) microhardnesss specimens 25 mm × 10 mm × 3 (±0.2) mm. For each test 6 groups were prepared (each group containing 5 samples). Thirty specimens were prepared in each of the three tests, amounting to a total number of 90 specimens. Mechanical properties such as flexural strength (FS), impact strength and microhardness of the above mentioned specimens were determined using universal testing machine, Izod pendulum impact testing machine and Vickers microhardness tester, respectively. ISO Specification No. 1567 was followed in microhardness test. The data was collected and statistically analyzed. Flexural strength considerably decreased by increasing TiO<sub>2</sub> concentration in both types of acrylic resin. Impact strength of the conventional acrylic resin modified by 1% of additives significantly increased. The microhardness is significantly increased by addition of 5% of TiO<sub>2</sub> Nps. The Incorporation of TiO<sub>2</sub> nanoparticles into acrylic resins can adversely affect its flexural strength. Meanwhile, the impact strength can be modified by small percentage of additives (abt. 1%). This effect is directly correlated with the concentration of nanoparticles. On the other hand, concentrations of TiO<sub>2</sub> Nps (abt. 5%) positively affect the microhardness of both types of acrylic resin used in the present study.</sub></sub></sub></sub></sub></sub></sub></sub></sub></sub>
文摘The persistence of bacteria in the root canal system is the primary cause of recurrent apical periodontitis.The adaptability of residual bacteria to changing environmental conditions is a key survival strategy of biofilms,often leading to endodontic treatment failure.DJK-5 is a protease-resistant,broad-spectrum D-enantiomeric peptide that degrades or prevents the accumulation of guanosine penta-and tetraphosphates,which are important for biofilm formation.We evaluated the effects of primary antimicrobial agents and nutrient conditions on the re-covery,metabolism,diversity,and composition of oral biofilms,and investigated how these factors affect the efficacy of DJK-5 and chlorhexidine(CHX)during re-exposure.Primary irrigants and nutrient conditions significantly influenced biofilm recovery,metabolic activity,diversity,and composition.Biofilm recovery was slower in nutrient-poor groups compared to nutrient-rich ones,and nutrient availability had the greatest effect on shaping both the diversity and composition of the biofilms.Water and DJK-5 groups showed similar biofilm diversity trends,while CHX generally led to lower diversity.Results indicate that primary irrigants and nutrient conditions significantly impact biofilm composition,diversity,and recovery.However,these changes did not compromise DJK-5’s effectiveness in killing of biofilm microbes during re-exposure of recovered biofilms.
