Dasmawati Mohamad - Academia.edu (original) (raw)

Papers by Dasmawati Mohamad

Light intensity output is one of the determinants for adequate curing of visible light-cured mate... more Light intensity output is one of the determinants for adequate curing of visible light-cured materials. The aim of this survey was to evaluate the performance of light curing units (LCUs) in PPSG and KPHUSM. All functioning light curing units were numbered and tested by using light radiocurimeter to determine the respective light intensity output. For cordless light-emitting-diode (LED) LCUs, testing procedure was done in two stages; in situ and after the units were fully charged. Other units were tested once only. The intensity value for each unit was read 5 times and averaged. Data for statistical analysis was assessed by using SPSS version 12.0. Out of all the units tested, 42% (31/73), 92% (23/25) and 73% (8/11) of cable LED, cordless LED and quartz-tungsten-halogen (QTH) LCUs respectively recorded acceptable light intensity output as measured by radiocurimeter. Independent t-test showed that there was statistically significant different of mean intensity output of cordless LED ...

Malaysian Journal of Social Sciences and Humanities (MJSSH)

The objectives of ATAP-NEPAH are to enhance and nurture healthy habits among adolescents as well ... more The objectives of ATAP-NEPAH are to enhance and nurture healthy habits among adolescents as well as to empower adolescents in inculcating these healthy habits among them. Health education through peer-to-peer approach is used to instill the knowledge on important areas such as sexual and reproductive health, smoking, substance abuse, illegal street racing (rempit) and mental health. Specific modules were developed by experts (lecturers) in multidisciplinary fields in collaboration with Malaysian Association for Adolescent Health (MAAH), National Population and Family Development Board (NPFDB), Reproductive Health Association of Kelantan (REHAK) and Rhaudatus Sakinah Kelantan. The trained Medical Students Facilitator Team (MSFT) of USM became trainers to secondary one school students. The selected school students were trained by the medical students to become peer educators to their juniors and peers. There was improvement in the readiness level of peer educators, knowledge and attit...

Proceedings of the 7th International Conference on Multidisciplinary Research

β-Tricalcium Phosphate (β–TCP) have been widely used as an implant materials. It has been success... more β-Tricalcium Phosphate (β–TCP) have been widely used as an implant materials. It has been successfully produced locally using two different method which is hydrothermal and precipitation. The aim of the study was to determine the biocompatibility of β-TCP prepared by hydrothermal and precipitation method with normal human osteoblast (NHOst) cells. For this purpose cytotoxicity of the material was assessed using an Alamar Blue method to determine the viability of NHOst cells grown with extracts of β-TCP in various concentrations. In addition NHOst grown on β-TCP ceramics were examined under an inverted microscope after 4, 24, 48 and 72 hours to verify cell attachment. Staining was done using Calcein AM and Ethidium homodimers to assess viability using a Confocal Laser Scanning Microscope (CLSM). The results showed that neither hydrothermal β-TCP nor precipitation β-TCP were cytotoxic with either of the method applied.

The aim of this study was to determine the effects of two types of coumarin derivatives, namely, ... more The aim of this study was to determine the effects of two types of coumarin derivatives, namely, 3-acetylcoumarin (AC) and coumarin thiosemicarbazone (CT) on surface characteristics such as the roughness, hardness, and morphology of resin-modified glass-ionomer cement (RMGIC). The release of coumarin from the fabricated RMGIC was also investigated. AC and CT at 1.0% (w/w) concentration were added into 0.3 g of RMGIC powder and mixed with 0.1 g of polyacrylic acid. The fabricated RMGIC-AC and RMGIC-CT were evaluated for surface characteristics such as roughness, hardness and topography. The coumarin release of AC and CT from RMGIC was also determined. The RMGIC-CT demonstrated a decreased roughness value among the materials. The surface roughness exhibited by the RMGIC was statistically higher (p < 0.05) than that of fabricated materials. The RMGIC-AC was observed to have the highest hardness value compared to the RMGIC-CT and RMGIC, and this value was significantly higher (p <...

Existence of stress distribution impact on the remodelling/osseointegration process, however, the... more Existence of stress distribution impact on the remodelling/osseointegration process, however, the distribution of stress in implant system is difficult to be measured. The purpose of this study was to perform the three-dimensional finite element analysis (FEA) for stress distribution analysis on implant system during post loading. Materials and Methods: A three-dimensional model of mandible which is consisting of bone, implant and tooth surrounding implant are constructed from CBCT data. The processing data including segmentation and meshing were processed using MIMICS Software. FEA was performed in ANSYS to investigate the distribution of stress due to three different simulations of loading; pull-in, push-out and removal torque. Results: The simulation showed that during the pull in and push out simulation, higher stresses were observed at the area around implant-bone conjunction. Stress also propagated into surrounding area around the nearest tooth. Propagation of the stress wa...

Article history: Received 15 September 2014 Accepted 5 October 2014 Available online 25 October 2014

International Journal of Technology, 2020

Dental implants commonly practiced replacing edentulous teeth. However, it is still challenging t... more Dental implants commonly practiced replacing edentulous teeth. However, it is still challenging to evaluate the progress of osseointegration during the healing process after implant placement. This study aims to measure the implant stability of pre-and post-crown placement to monitor osseointegration during the healing process and correlate it with the bone quality and quantity and other parameters. Resonance Frequency Analysis (RFA) method as a standard method has been used to monitor implant stability. Ten patients from Hospital Universiti Sains Malaysia have been involved with and treated by immediate implant placement procedures on their mandibular jaw system. Monitoring was also conducted by measuring the density of bone estimated based on Cone Beam Computed Tomography data. On the basis of the study, RFA and density monitoring show that there are at least three classes of patients: Class 1 are the patients who have a significant increment of implant stability; Class 2 are the patients with constant implant stability; and Class 3 are the patients who have negative implant stability progress, or their implant stability was decreasing. On the basis of the result, monitoring of implant stability by measuring the density is still challenging, the correlation between secondary implant stability and density is not significant statistically. It is recommended in future research to evaluate the implant stability by involving more patients from different races and also correlating the implant stability with the dynamic properties such as stress distribution.

Unfilled PMMA suffers from its moderate mechanical properties and high shrinkage. This study aime... more Unfilled PMMA suffers from its moderate mechanical properties and high shrinkage. This study aimed to evaluate tensile and shrinkage of newly developed β-TCP/ZnO filled PMMA for craniofacial reconstruction. β-TCP was fixed at 15 wt%, whereas ZnO was varied between 0, 2.5 and 5 wt%. Unfilled PMMA was also prepared as control (n=7/composition). β-TCP particles were in 1-5 µm sizes whereas ZnO particles were in nanosize of less than 260nm.The effect of filler incorporation on the tensile and morphological were determined using Universal Testing Machine (AGX 2 plus, Shimadzu, Japan), field emission scanning electron microscope (FESEM) and scanning electron microscope (SEM). Shrinkage was calculated using volumetric shrinkage formula. Statistical analysis of One-Way ANOVA (p<0.05) was employed to assess the differences in the mean of tensile and shrinkage properties between the developed composites and unfilled PMMA. Shrinkage percentages reduced from 8.29 % (unfilled PMMA) to 4.8% ...

Materials Chemistry and Physics

Abstract Zinc oxide eugenol (ZOE) is composed of approximately 70% ZnO and approximately 30% euge... more Abstract Zinc oxide eugenol (ZOE) is composed of approximately 70% ZnO and approximately 30% eugenol. ZOE has been used in dentistry as a temporary filler, cavity liner, and base for tooth cavities. It is used to form a thin layer of cement to protect the pulp from any influx of bacteria or irritants present in the tooth cavity. Such bacteria and irritants can lead to the formation of an abscess or pus in the gums or periapical tissues. As ZnO has antibacterial effects, it is appropriate to use ZOE as a temporary filler, liner, or base. On the other hand, eugenol alone is acidic and may leach out to have adverse effects on the periapical tissue. Therefore, the toxicity level of ZOE is important to avoid adverse effects or unnecessary dosing. Thus, in the present study, we investigated the potential toxicity of ZOE leaching toward human gingival fibroblast tissue to verify its safety and efficacy by using ZnO particles with different morphologies and sizes. Three types of ZnO powder were used in this study: ZnO-A and ZnO–B (which were produced using the French process) and ZnO–K, which are commercial particles used for ZOE temporary fillers. All three types of ZnO were mixed with eugenol to form ZOE. Then, all three types were characterised to determine their morphology, particle size, and specific surface area. Each type of ZnO was then mixed with resin-bonded eugenol to obtain ZOE pellets. Subsequently, the toxicology of the ZOE leachings was tested on human gingival fibroblast cells using a calorimetric assay for 24 and 48 h. The results show that ZnO-A, ZnO–B, and ZnO–K have particle sizes of 22.3, 48.33, and 1196 nm, respectively. The specific surface areas were 4.44, 3.89, and 0.74 m2/g, respectively. Moreover, the toxicology of the ZOE leachings revealed a lower percentage of viable cells with an increase in the leaching concentration. After 24 and 48 h of cytotoxicity tests, the percentage of viable cells decreased slightly with leaching concentrations of 10%–40% and decreased considerably with leaching concentrations of 50%–100%. This shows that the viable cell percentage depends on the leaching concentration and duration of the exposure. Moreover, the results show that smaller particles have larger specific surface areas and higher percentages of viable cells. This means that the smaller particles released smaller amounts of eugenol and Zn2+ during the toxicity evaluation, which led to less reactive oxygen species (ROS) production and influenced the number of cells that survived after 24 and 48 h.

Journal of Materials Research and Technology

Polymers

Calcium silicate-based cements (CSCs) are widely used in various endodontic treatments to promote... more Calcium silicate-based cements (CSCs) are widely used in various endodontic treatments to promote wound healing and hard tissue formation. Chitosan-based accelerated Portland cement (APC-CT) is a promising and affordable material for endodontic use. This study investigated the effect of APC-CT on apoptosis, cell attachment, dentinogenic/osteogenic differentiation and mineralization activity of stem cells from human exfoliated deciduous teeth (SHED). APC-CT was prepared with various concentrations of chitosan (CT) solution (0%, 0.625%, 1.25% and 2.5% (w/v)). Cell attachment was determined by direct contact analysis using field emission scanning electron microscopy (FESEM); while the material extracts were used for the analyses of apoptosis by flow cytometry, dentinogenic/osteogenic marker expression by real-time PCR and mineralization activity by Alizarin Red and Von Kossa staining. The cells effectively attached to the surfaces of APC and APC-CT, acquiring flattened elongated and ro...

AIP Conference Proceedings

Journal of International Oral Health

Glass ionomer cements (GIC) were first introduced to dentistry in the late 1960s and since have p... more Glass ionomer cements (GIC) were first introduced to dentistry in the late 1960s and since have proven to be useful in various areas of dental science, particularly restorative dentistry. As an aqueous polyelectrolyte system, GICs are known for their relative ease of use, chemical bond to the tooth, fluoride release and recharge, low coefficient of thermal expansion, and acceptable esthetic quality. However, clinical usage of GICs is still limited due to their relatively inferior mechanical properties and sensitivity to initial desiccation and moisture. Years of extensive research on enhancing the chemistry of the basic glasses have yielded improved formulations with enhanced mechanical properties and reduced moisture sensitivity. A comprehensive review of the available literature has revealed that not all modifications in glass powder have resulted in the desirable strengthening of GICs. There is a shift of focus toward studies on nanoscale particles and bioactive glass. Recent research has proven that incorporation of nanoceramics such as hydroxyapatite (HA), fluorapatite, silica, and zirconia (ZrO2) have resulted in improved mechanical properties of GICs due to their ability to release fluoride, high surface area, and better particle size distribution. More work should thus, be undertaken to optimize techniques for enhancing the physicomechanical properties of GICs by incorporation of nanophases of ZrO2, HA, and metallic nanofillers.

Bangladesh Journal of Medical Science

Background: Studies on microleakage of Computer-Aided Design/Computer-Aided Manufacturing (CAD/CA... more Background: Studies on microleakage of Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) crowns are abundant. However many of them are inconclusive, especially those using self adhesive cements. Aims: To compare the microleakage between CAD/CAM crowns milled out of feldspathic ceramic and resin nano ceramics, cemented with three resin cements. Materials and Methods: Crown preparation was made on 54 extracted human premolars. Impressions were captured optically using CEREC 3D machine intraoral camera, and crowns were milled from feldspathic ceramic (CEREC® Blocs PC, VITA) and resin nano ceramic (Lava™ Ultimate CAD/CAM Restorative, 3M ESPE) blocks. The crowns were then cemented with three cements (n = 9); RelyX™ U200 Self-Adhesive Resin Cement (3M ESPE); NX3 Nexus ® cement with two-step etch-and-rinse adhesive (Kerr Corporation) or three/multistep etch-and-rinse resin cement, Variolink® II/Syntac Classic (Ivoclar Vivadent). The specimens were kept in water for 24 hours, the...

Dental Materials

OBJECTIVE To compare the mechanical and biological properties of newly developed hybrid ceramics ... more OBJECTIVE To compare the mechanical and biological properties of newly developed hybrid ceramics filled and unfilled polyamide 12 (PA 12) for craniofacial reconstruction via a fused deposition modelling (FDM) framework. METHODS 15wt% of zirconia (ZrO2) as well as 30, 35, and 40wt% of beta-tricalcium phosphate (β-TCP) were compounded with PA 12, followed by the fabrication of filament feedstocks using a single screw extruder. The fabricated filament feedstocks were used to print the impact specimens. The melt flow rate, tensile properties of fabricated filament feedstocks, and 3D printed impact properties of the specimens were assessed using melt flow indexer, universal testing machine, and Izod pendulum tester, respectively. The microstructure of selected filament feedstocks and broken impact specimens were analysed using a field emission scanning electron microscope and universal testing machine. Human periodontal ligament fibroblast cells (HPdLF) were used to evaluate the cytotoxicity of the materials by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromid) (MTT) assay. RESULTS Hybrid ceramics filled PA 12 indicated sufficient flowability for FDM 3D printing. The tensile strength of hybrid ceramics filled PA 12 filament feedstocks slightly reduced as compared to unfilled PA 12. However, the tensile modulus and impact strength of hybrid ceramics filled PA 12 increased by 8%-31% and 98%-181%, respectively. A significant increase was also detected in the cell viability of the developed composites at concentrations of 12.5, 25, 50 and 100mg/ml. SIGNIFICANCE The newly developed hybrid ceramics filled PA 12 filament feedstock with improved properties is suitable for an FDM-based 3D printer, which enables the creation of patient-specific craniofacial implant at a lower cost to serve low-income patients.

Journal of Materials Research and Technology

Abstract This study aims to fabricate experimental flowable composites (FCs), by incorporating sp... more Abstract This study aims to fabricate experimental flowable composites (FCs), by incorporating spherical nanohybrid silica as the filler and subsequently to evaluate their physical and mechanical properties in comparison to a commercial counterpart (Revolution Formula 2). The nanohybrid silica used in this study was synthesised from rice husk using sol–gel method and the dilution effect of Bis-GMA on the physical and mechanical properties of the experimental FCs was also investigated. Three experimental FCs (EF50B, EF45B and EF40B) were prepared by diluting the base monomer namely Bis-GMA to obtain the desired flowability. Surface roughness, surface morphology, Vickers hardness, compressive strength and compressive modulus of each group were determined. The data were statistically analysed using one-way ANOVA followed by Scheffe post hoc test. The surface roughness and Vickers hardness of the experimental FCs were comparable to Revolution Formula 2. Even though experimental FCs were inferior in compressive strength compared to Revolution Formula 2, they had passed the minimum requirement for compressive strength. The compressive modulus of experimental FCs was higher than Revolution Formula 2, but no statistically significant difference was detected except for EF50B. The dilution of the base monomer among the experimental FCs had no significant effect on their physical and mechanical strength. In conclusion, experimental FCs from rice husk had adequate physical and mechanical strength in comparison to the commercial counterpart rendering them a potential sustainable green-based product in dentistry.

Materials science & engineering. C, Materials for biological applications, 2017

ZnO with two different morphologies were used to study the inhibition of Streptococcus sobrinus a... more ZnO with two different morphologies were used to study the inhibition of Streptococcus sobrinus and Streptococcus mutans which are closely associated with tooth cavity. Rod-like shaped ZnO-A and plate-like shaped ZnO-B were produced using a zinc boiling furnace. The nanopowders were characterized using energy filtered transmission electron microscopy (EFTEM), X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, Raman spectroscopy and dynamic light scattering (DLS) to confirm the properties of the ZnO polycrystalline wurtzite structures. XRD results show that the calculated crystallite sizes of ZnO-A and ZnO-B were 36.6 and 39.4nm, respectively, whereas DLS revealed particle size distributions of 21.82nm (ZnO-A) and 52.21nm (ZnO-B). PL spectra showed ion vacancy defects related to green and red luminescence for both ZnO particles. These defects evolved during the generation of reactive oxygen species which contributed to the antibacterial activity. Antibacterial activity was...

Malaysian Journal of Medical Sciences, 2017

Background: This study investigated the association of emotional intelligence (EI) and other fact... more Background: This study investigated the association of emotional intelligence (EI) and other factors with perceived stress (PS) in undergraduate dental students. Methods: A total of 234 undergraduate dental students at the School of Dental Sciences, Universiti Sains Malaysia (USM), in the academic year of 2009/2010, participated in this crosssectional study. Self-administered questionnaires, the Assessing Emotions Scale and the Perceived Stress Scale (PSS-10), were used to evaluate EI and PS, respectively. Results: The mean EI score was 121.2 (SD 11.85). The scores were significantly higher in females than males, and in students who chose dentistry based on their own interest rather than in those who were motivated by others to study dentistry. The mean PSS-10 score was 21.2 (SD 5.08). Pearson correlation analysis indicated a significant inverse relationship between EI and PSS-10 scores (r =-0.337). Multi-variable regression analysis also indicated a significant negative linear association between EI and PSS-10 scores (b =-0.156, 95% CI:-0.207,-0.104). PSS-10 scores were significantly higher for students who were in the clinical years rather than the preclinical years. Conclusions: This study of USM undergraduate dental students shows that a low EI, female sex, and being in the clinical years were significant predictors of PS.

Light intensity output is one of the determinants for adequate curing of visible light-cured mate... more Light intensity output is one of the determinants for adequate curing of visible light-cured materials. The aim of this survey was to evaluate the performance of light curing units (LCUs) in PPSG and KPHUSM. All functioning light curing units were numbered and tested by using light radiocurimeter to determine the respective light intensity output. For cordless light-emitting-diode (LED) LCUs, testing procedure was done in two stages; in situ and after the units were fully charged. Other units were tested once only. The intensity value for each unit was read 5 times and averaged. Data for statistical analysis was assessed by using SPSS version 12.0. Out of all the units tested, 42% (31/73), 92% (23/25) and 73% (8/11) of cable LED, cordless LED and quartz-tungsten-halogen (QTH) LCUs respectively recorded acceptable light intensity output as measured by radiocurimeter. Independent t-test showed that there was statistically significant different of mean intensity output of cordless LED ...

Malaysian Journal of Social Sciences and Humanities (MJSSH)

The objectives of ATAP-NEPAH are to enhance and nurture healthy habits among adolescents as well ... more The objectives of ATAP-NEPAH are to enhance and nurture healthy habits among adolescents as well as to empower adolescents in inculcating these healthy habits among them. Health education through peer-to-peer approach is used to instill the knowledge on important areas such as sexual and reproductive health, smoking, substance abuse, illegal street racing (rempit) and mental health. Specific modules were developed by experts (lecturers) in multidisciplinary fields in collaboration with Malaysian Association for Adolescent Health (MAAH), National Population and Family Development Board (NPFDB), Reproductive Health Association of Kelantan (REHAK) and Rhaudatus Sakinah Kelantan. The trained Medical Students Facilitator Team (MSFT) of USM became trainers to secondary one school students. The selected school students were trained by the medical students to become peer educators to their juniors and peers. There was improvement in the readiness level of peer educators, knowledge and attit...

Proceedings of the 7th International Conference on Multidisciplinary Research

β-Tricalcium Phosphate (β–TCP) have been widely used as an implant materials. It has been success... more β-Tricalcium Phosphate (β–TCP) have been widely used as an implant materials. It has been successfully produced locally using two different method which is hydrothermal and precipitation. The aim of the study was to determine the biocompatibility of β-TCP prepared by hydrothermal and precipitation method with normal human osteoblast (NHOst) cells. For this purpose cytotoxicity of the material was assessed using an Alamar Blue method to determine the viability of NHOst cells grown with extracts of β-TCP in various concentrations. In addition NHOst grown on β-TCP ceramics were examined under an inverted microscope after 4, 24, 48 and 72 hours to verify cell attachment. Staining was done using Calcein AM and Ethidium homodimers to assess viability using a Confocal Laser Scanning Microscope (CLSM). The results showed that neither hydrothermal β-TCP nor precipitation β-TCP were cytotoxic with either of the method applied.

The aim of this study was to determine the effects of two types of coumarin derivatives, namely, ... more The aim of this study was to determine the effects of two types of coumarin derivatives, namely, 3-acetylcoumarin (AC) and coumarin thiosemicarbazone (CT) on surface characteristics such as the roughness, hardness, and morphology of resin-modified glass-ionomer cement (RMGIC). The release of coumarin from the fabricated RMGIC was also investigated. AC and CT at 1.0% (w/w) concentration were added into 0.3 g of RMGIC powder and mixed with 0.1 g of polyacrylic acid. The fabricated RMGIC-AC and RMGIC-CT were evaluated for surface characteristics such as roughness, hardness and topography. The coumarin release of AC and CT from RMGIC was also determined. The RMGIC-CT demonstrated a decreased roughness value among the materials. The surface roughness exhibited by the RMGIC was statistically higher (p < 0.05) than that of fabricated materials. The RMGIC-AC was observed to have the highest hardness value compared to the RMGIC-CT and RMGIC, and this value was significantly higher (p <...

Existence of stress distribution impact on the remodelling/osseointegration process, however, the... more Existence of stress distribution impact on the remodelling/osseointegration process, however, the distribution of stress in implant system is difficult to be measured. The purpose of this study was to perform the three-dimensional finite element analysis (FEA) for stress distribution analysis on implant system during post loading. Materials and Methods: A three-dimensional model of mandible which is consisting of bone, implant and tooth surrounding implant are constructed from CBCT data. The processing data including segmentation and meshing were processed using MIMICS Software. FEA was performed in ANSYS to investigate the distribution of stress due to three different simulations of loading; pull-in, push-out and removal torque. Results: The simulation showed that during the pull in and push out simulation, higher stresses were observed at the area around implant-bone conjunction. Stress also propagated into surrounding area around the nearest tooth. Propagation of the stress wa...

Article history: Received 15 September 2014 Accepted 5 October 2014 Available online 25 October 2014

International Journal of Technology, 2020

Dental implants commonly practiced replacing edentulous teeth. However, it is still challenging t... more Dental implants commonly practiced replacing edentulous teeth. However, it is still challenging to evaluate the progress of osseointegration during the healing process after implant placement. This study aims to measure the implant stability of pre-and post-crown placement to monitor osseointegration during the healing process and correlate it with the bone quality and quantity and other parameters. Resonance Frequency Analysis (RFA) method as a standard method has been used to monitor implant stability. Ten patients from Hospital Universiti Sains Malaysia have been involved with and treated by immediate implant placement procedures on their mandibular jaw system. Monitoring was also conducted by measuring the density of bone estimated based on Cone Beam Computed Tomography data. On the basis of the study, RFA and density monitoring show that there are at least three classes of patients: Class 1 are the patients who have a significant increment of implant stability; Class 2 are the patients with constant implant stability; and Class 3 are the patients who have negative implant stability progress, or their implant stability was decreasing. On the basis of the result, monitoring of implant stability by measuring the density is still challenging, the correlation between secondary implant stability and density is not significant statistically. It is recommended in future research to evaluate the implant stability by involving more patients from different races and also correlating the implant stability with the dynamic properties such as stress distribution.

Unfilled PMMA suffers from its moderate mechanical properties and high shrinkage. This study aime... more Unfilled PMMA suffers from its moderate mechanical properties and high shrinkage. This study aimed to evaluate tensile and shrinkage of newly developed β-TCP/ZnO filled PMMA for craniofacial reconstruction. β-TCP was fixed at 15 wt%, whereas ZnO was varied between 0, 2.5 and 5 wt%. Unfilled PMMA was also prepared as control (n=7/composition). β-TCP particles were in 1-5 µm sizes whereas ZnO particles were in nanosize of less than 260nm.The effect of filler incorporation on the tensile and morphological were determined using Universal Testing Machine (AGX 2 plus, Shimadzu, Japan), field emission scanning electron microscope (FESEM) and scanning electron microscope (SEM). Shrinkage was calculated using volumetric shrinkage formula. Statistical analysis of One-Way ANOVA (p<0.05) was employed to assess the differences in the mean of tensile and shrinkage properties between the developed composites and unfilled PMMA. Shrinkage percentages reduced from 8.29 % (unfilled PMMA) to 4.8% ...

Materials Chemistry and Physics

Abstract Zinc oxide eugenol (ZOE) is composed of approximately 70% ZnO and approximately 30% euge... more Abstract Zinc oxide eugenol (ZOE) is composed of approximately 70% ZnO and approximately 30% eugenol. ZOE has been used in dentistry as a temporary filler, cavity liner, and base for tooth cavities. It is used to form a thin layer of cement to protect the pulp from any influx of bacteria or irritants present in the tooth cavity. Such bacteria and irritants can lead to the formation of an abscess or pus in the gums or periapical tissues. As ZnO has antibacterial effects, it is appropriate to use ZOE as a temporary filler, liner, or base. On the other hand, eugenol alone is acidic and may leach out to have adverse effects on the periapical tissue. Therefore, the toxicity level of ZOE is important to avoid adverse effects or unnecessary dosing. Thus, in the present study, we investigated the potential toxicity of ZOE leaching toward human gingival fibroblast tissue to verify its safety and efficacy by using ZnO particles with different morphologies and sizes. Three types of ZnO powder were used in this study: ZnO-A and ZnO–B (which were produced using the French process) and ZnO–K, which are commercial particles used for ZOE temporary fillers. All three types of ZnO were mixed with eugenol to form ZOE. Then, all three types were characterised to determine their morphology, particle size, and specific surface area. Each type of ZnO was then mixed with resin-bonded eugenol to obtain ZOE pellets. Subsequently, the toxicology of the ZOE leachings was tested on human gingival fibroblast cells using a calorimetric assay for 24 and 48 h. The results show that ZnO-A, ZnO–B, and ZnO–K have particle sizes of 22.3, 48.33, and 1196 nm, respectively. The specific surface areas were 4.44, 3.89, and 0.74 m2/g, respectively. Moreover, the toxicology of the ZOE leachings revealed a lower percentage of viable cells with an increase in the leaching concentration. After 24 and 48 h of cytotoxicity tests, the percentage of viable cells decreased slightly with leaching concentrations of 10%–40% and decreased considerably with leaching concentrations of 50%–100%. This shows that the viable cell percentage depends on the leaching concentration and duration of the exposure. Moreover, the results show that smaller particles have larger specific surface areas and higher percentages of viable cells. This means that the smaller particles released smaller amounts of eugenol and Zn2+ during the toxicity evaluation, which led to less reactive oxygen species (ROS) production and influenced the number of cells that survived after 24 and 48 h.

Journal of Materials Research and Technology

Polymers

Calcium silicate-based cements (CSCs) are widely used in various endodontic treatments to promote... more Calcium silicate-based cements (CSCs) are widely used in various endodontic treatments to promote wound healing and hard tissue formation. Chitosan-based accelerated Portland cement (APC-CT) is a promising and affordable material for endodontic use. This study investigated the effect of APC-CT on apoptosis, cell attachment, dentinogenic/osteogenic differentiation and mineralization activity of stem cells from human exfoliated deciduous teeth (SHED). APC-CT was prepared with various concentrations of chitosan (CT) solution (0%, 0.625%, 1.25% and 2.5% (w/v)). Cell attachment was determined by direct contact analysis using field emission scanning electron microscopy (FESEM); while the material extracts were used for the analyses of apoptosis by flow cytometry, dentinogenic/osteogenic marker expression by real-time PCR and mineralization activity by Alizarin Red and Von Kossa staining. The cells effectively attached to the surfaces of APC and APC-CT, acquiring flattened elongated and ro...

AIP Conference Proceedings

Journal of International Oral Health

Glass ionomer cements (GIC) were first introduced to dentistry in the late 1960s and since have p... more Glass ionomer cements (GIC) were first introduced to dentistry in the late 1960s and since have proven to be useful in various areas of dental science, particularly restorative dentistry. As an aqueous polyelectrolyte system, GICs are known for their relative ease of use, chemical bond to the tooth, fluoride release and recharge, low coefficient of thermal expansion, and acceptable esthetic quality. However, clinical usage of GICs is still limited due to their relatively inferior mechanical properties and sensitivity to initial desiccation and moisture. Years of extensive research on enhancing the chemistry of the basic glasses have yielded improved formulations with enhanced mechanical properties and reduced moisture sensitivity. A comprehensive review of the available literature has revealed that not all modifications in glass powder have resulted in the desirable strengthening of GICs. There is a shift of focus toward studies on nanoscale particles and bioactive glass. Recent research has proven that incorporation of nanoceramics such as hydroxyapatite (HA), fluorapatite, silica, and zirconia (ZrO2) have resulted in improved mechanical properties of GICs due to their ability to release fluoride, high surface area, and better particle size distribution. More work should thus, be undertaken to optimize techniques for enhancing the physicomechanical properties of GICs by incorporation of nanophases of ZrO2, HA, and metallic nanofillers.

Bangladesh Journal of Medical Science

Background: Studies on microleakage of Computer-Aided Design/Computer-Aided Manufacturing (CAD/CA... more Background: Studies on microleakage of Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) crowns are abundant. However many of them are inconclusive, especially those using self adhesive cements. Aims: To compare the microleakage between CAD/CAM crowns milled out of feldspathic ceramic and resin nano ceramics, cemented with three resin cements. Materials and Methods: Crown preparation was made on 54 extracted human premolars. Impressions were captured optically using CEREC 3D machine intraoral camera, and crowns were milled from feldspathic ceramic (CEREC® Blocs PC, VITA) and resin nano ceramic (Lava™ Ultimate CAD/CAM Restorative, 3M ESPE) blocks. The crowns were then cemented with three cements (n = 9); RelyX™ U200 Self-Adhesive Resin Cement (3M ESPE); NX3 Nexus ® cement with two-step etch-and-rinse adhesive (Kerr Corporation) or three/multistep etch-and-rinse resin cement, Variolink® II/Syntac Classic (Ivoclar Vivadent). The specimens were kept in water for 24 hours, the...

Dental Materials

OBJECTIVE To compare the mechanical and biological properties of newly developed hybrid ceramics ... more OBJECTIVE To compare the mechanical and biological properties of newly developed hybrid ceramics filled and unfilled polyamide 12 (PA 12) for craniofacial reconstruction via a fused deposition modelling (FDM) framework. METHODS 15wt% of zirconia (ZrO2) as well as 30, 35, and 40wt% of beta-tricalcium phosphate (β-TCP) were compounded with PA 12, followed by the fabrication of filament feedstocks using a single screw extruder. The fabricated filament feedstocks were used to print the impact specimens. The melt flow rate, tensile properties of fabricated filament feedstocks, and 3D printed impact properties of the specimens were assessed using melt flow indexer, universal testing machine, and Izod pendulum tester, respectively. The microstructure of selected filament feedstocks and broken impact specimens were analysed using a field emission scanning electron microscope and universal testing machine. Human periodontal ligament fibroblast cells (HPdLF) were used to evaluate the cytotoxicity of the materials by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromid) (MTT) assay. RESULTS Hybrid ceramics filled PA 12 indicated sufficient flowability for FDM 3D printing. The tensile strength of hybrid ceramics filled PA 12 filament feedstocks slightly reduced as compared to unfilled PA 12. However, the tensile modulus and impact strength of hybrid ceramics filled PA 12 increased by 8%-31% and 98%-181%, respectively. A significant increase was also detected in the cell viability of the developed composites at concentrations of 12.5, 25, 50 and 100mg/ml. SIGNIFICANCE The newly developed hybrid ceramics filled PA 12 filament feedstock with improved properties is suitable for an FDM-based 3D printer, which enables the creation of patient-specific craniofacial implant at a lower cost to serve low-income patients.

Journal of Materials Research and Technology

Abstract This study aims to fabricate experimental flowable composites (FCs), by incorporating sp... more Abstract This study aims to fabricate experimental flowable composites (FCs), by incorporating spherical nanohybrid silica as the filler and subsequently to evaluate their physical and mechanical properties in comparison to a commercial counterpart (Revolution Formula 2). The nanohybrid silica used in this study was synthesised from rice husk using sol–gel method and the dilution effect of Bis-GMA on the physical and mechanical properties of the experimental FCs was also investigated. Three experimental FCs (EF50B, EF45B and EF40B) were prepared by diluting the base monomer namely Bis-GMA to obtain the desired flowability. Surface roughness, surface morphology, Vickers hardness, compressive strength and compressive modulus of each group were determined. The data were statistically analysed using one-way ANOVA followed by Scheffe post hoc test. The surface roughness and Vickers hardness of the experimental FCs were comparable to Revolution Formula 2. Even though experimental FCs were inferior in compressive strength compared to Revolution Formula 2, they had passed the minimum requirement for compressive strength. The compressive modulus of experimental FCs was higher than Revolution Formula 2, but no statistically significant difference was detected except for EF50B. The dilution of the base monomer among the experimental FCs had no significant effect on their physical and mechanical strength. In conclusion, experimental FCs from rice husk had adequate physical and mechanical strength in comparison to the commercial counterpart rendering them a potential sustainable green-based product in dentistry.

Materials science & engineering. C, Materials for biological applications, 2017

ZnO with two different morphologies were used to study the inhibition of Streptococcus sobrinus a... more ZnO with two different morphologies were used to study the inhibition of Streptococcus sobrinus and Streptococcus mutans which are closely associated with tooth cavity. Rod-like shaped ZnO-A and plate-like shaped ZnO-B were produced using a zinc boiling furnace. The nanopowders were characterized using energy filtered transmission electron microscopy (EFTEM), X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, Raman spectroscopy and dynamic light scattering (DLS) to confirm the properties of the ZnO polycrystalline wurtzite structures. XRD results show that the calculated crystallite sizes of ZnO-A and ZnO-B were 36.6 and 39.4nm, respectively, whereas DLS revealed particle size distributions of 21.82nm (ZnO-A) and 52.21nm (ZnO-B). PL spectra showed ion vacancy defects related to green and red luminescence for both ZnO particles. These defects evolved during the generation of reactive oxygen species which contributed to the antibacterial activity. Antibacterial activity was...

Malaysian Journal of Medical Sciences, 2017

Background: This study investigated the association of emotional intelligence (EI) and other fact... more Background: This study investigated the association of emotional intelligence (EI) and other factors with perceived stress (PS) in undergraduate dental students. Methods: A total of 234 undergraduate dental students at the School of Dental Sciences, Universiti Sains Malaysia (USM), in the academic year of 2009/2010, participated in this crosssectional study. Self-administered questionnaires, the Assessing Emotions Scale and the Perceived Stress Scale (PSS-10), were used to evaluate EI and PS, respectively. Results: The mean EI score was 121.2 (SD 11.85). The scores were significantly higher in females than males, and in students who chose dentistry based on their own interest rather than in those who were motivated by others to study dentistry. The mean PSS-10 score was 21.2 (SD 5.08). Pearson correlation analysis indicated a significant inverse relationship between EI and PSS-10 scores (r =-0.337). Multi-variable regression analysis also indicated a significant negative linear association between EI and PSS-10 scores (b =-0.156, 95% CI:-0.207,-0.104). PSS-10 scores were significantly higher for students who were in the clinical years rather than the preclinical years. Conclusions: This study of USM undergraduate dental students shows that a low EI, female sex, and being in the clinical years were significant predictors of PS.