وجیه سادات مرتضوی

The objective of this study was to synthesize glass ionomer–forsterite nanocomposite and study the effect of incorporating forsterite nanoparticles to the ceramic part of glass ionomer cement in order to improve mechanical properties and bioactivity. So، Forsterite nanoparticles were made by the sol-gel process using different weight percentages added to the ceramic part of commercial GIC (Fuji II GC). X-ray diffraction (XRD) was used in order to characterize and determine grain size of the produced forsterite nanopowder. In order to study the mechanical properties of the produced glass ionomer cement-forsterite nanocomposite، the compressive strength (CS)، three-point flexural strength (FS) and diametral tensile strength (DTS) of specimens were measured. Statistical analysis was done by one Way ANOVA and differences were considered significant if P‹0. 05. The morphology of fracture surface of specimens was studied using scanning electron microscopy (SEM) technique. Bioactivity of specimens was investigated by Fourier transitioned-infrared spectroscopy (FTIR)، scanning electron microscopy (SEM)، and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The results of XRD analysis confirmed the nanocrystalline and pure forsterite synthesis. According to the mechanical properties measurements، the optimum weight percentages of forsterite nanoparticles for enhancement of CS، FS، and DTS were obtained equal to 3، 1 and 1 wt. %، respectively. Statistical analysis showed that the differences between all the groups were significant (P<0. 05). SEM images and results of the ICP-OES and FTIR tests confirmed the bioactivity of the nanocomposite. Glass ionomer-forsterite nanocomposite containing 1 to 3 wt. %-forsterite nanoparticles can be a suitable candidate for dentistry and orthopedic applications due to the improvement of mechanical properties and bioactivity.

In this study، antibacterial behavior of nanoparticles of titania and nanoparticles of silver-doped titania were evaluated against Streptococcus mutans and were compared with three pathogen bacteria. Initially، the nanoparticles of titania and nanoparticles of silver-doped titania were synthesized by sol-gel method. The powders were characterized by X-ray diffraction (XRD)، Transmission Electron Microscopy (TEM) and Energy-Dispersive Spectroscopy (EDS) techniques. Then، Agar dilution was used to evaluate antibacterial properties of silver- doped titania nanoparticles against Streptococcus mutans and three types of pathogen bacteria. Phase structure evaluation showed anatase phase of titania in all silver-dopped titania nanoparticles. The particle size of titania and silver particles were determined 30 and 15 nanometers، respectively. The antibacterial results showed that Minimum Inhibition Concentration (MIC) of 3 mg/ml for silver-doped titania nanoparticles with different percentages of silver could inhibit bacteria growth، while nanoparticles of titania in fluorescent light indicated reducing growth of bacteria. Furthermore، MIC of 4 mg/ml was achieved for silver-doped titania nanoparticles with 5 mole percent sliver against the other pathogen bacteria and for other specimens observed growth of bacteria. These results showed that silver could increase antibacterial properties of titania. This is due to presence of silver nanoparticles and also the effect of silver on the photocatalyst properties increased antibacterial properties.

Yttria stabilized zirconia (YSZ) has been under consideration due to its desiredproperties for preparing dental restorations. The aim of this research was to produce the YSZnanopowder via sol-gel rout. The present research was an experimental study and in vitro evaluation.Appropriate amount of zirconium oxide chloride, ZrOC12.8H2O, and yttrium nitrate,Y(NO3)3.6H2O, to reach 3mol% yttrium oxide in final product, were mixed in anhydrous ethanol ona magnetic stirrer. After drying the obtained gel at 50ºC, it was calcined at 600ºC for 1, 2 and 3hours. Phase identification, particle size and distribution determination, functional groupidentification and microstructural investigation were performed using XRD, SEM, TEM and FTIRtechniques. Results revealed that the tetragonal zirconia phase nanopowder has been obtained.Crystallite size of the powder was about 20 nm and the size of particles was about 80 nm. Theoptimum temperature and time for calcimine process was 600ºC and 3 hours, respectively. The obtained Yttria stabilized zirconia with special characteristics duo to nano scalestructure, could be a desired biomaterials for preparing dental restorations such as inlay, on lay, postand core, crown, and bridges in dentistry

Regarding the importance of surface roughness of tooth structure and restorative materials on plaque retention, this study was done to evaluate the effect of home and office bleaching agents on surface roughness of microhybrid and nanofilled composite resins. Point 4 (kerr, USA) microhybride composite, Premise (Kerr, USA) and Filtek supreme (3M ESPE, USA) nanofilled composites, Opalescence PF (Ultradent, USA) as the home bleaching agent and Opalescence Quisk (Ultradent, USA) as the office bleaching agent were selected. One hundred and fifty samples were divided into 15 groups (n = 10). For each composite, five groups were defined as: control, two weeks home bleaching, 4 weeks home bleaching, one time office bleaching and two times office bleaching with 2 weeks interval. The composites light cured under clear matrix strip and polished with soflex TM (3M ESPE, USA) polishing disks systems.After bleaching with specific protocol, surface roughness of samples was measured withprofilometer (SM7 Profile Test, Italy). The data were analyzed with two-way ANOVA statistical test. Surface morphology of samples were analyzed with scanning electron microscopy; SEM (XL30, Philips, Netherlands). There was no significant difference in surface roughness among all groups (p value > 0.05). There were no difference between the surface morphology of control and experimental groups of each composite. The bleaching agents used in this study had no effects on surface roughness of two types of nanofilled composites and one type of microhybrid composite.

Introduction of a material, that in blood contamination, can maintain marginal seal plays an important role in clinical success of a restoration. The aim of this study was to determine and compare microleakage rates of composite and compomer restorative materials, in blood contamination, with the application of Prompt L-Pop as an adhesive system. In this experimental study, One hundred and twenty ClV cavities, in dentino - enamal junction of buccal and lingual surfaces of extracted human sound molars, were prepared. After Prompt L-Pop application, the samples were divided in to 10 groups of 12 cavities Group Z1 was control Group Z2 was contaminated. Group Z3 was rinsed with water after contamination. Group Z4 was rinsed with water after contamination and Pronpt L-Pop was reused. GroupZ5. was similar to Z4 but it was rinsed with Naocl after contamination. The cavities were filled with composite (Z 520). The remaining five groups (F1 to F5), were just the same but filled with compomer (F 2000). After polishing and thremocycling (X 500) the microleakage rates of specimens were evaluated with dye penetration method. The data were statistically analyzed using Kruskal - Wallis and Mann - Whitney tests. Kruskal - Wallis test revealed significant differences among composite groups in gingival margins (p= 0.017). Mann - Whitney test showed more microleakage in group Z2 as compared with groups, Z1 Z4 and Z5 (P=0.005, P=0.015 and P=0.015, respectively) which was statistically significant. No significant differences were found, in microleakage rate, between composite andcompomer groups in occlusal and gingival margins (P= 0.348 and P=0.213,respectively). According to the results of this study, blood contamination could increase the microleakage of composite and Prompt L-Pop in gingival margins. In this condition rinsing with water and Naocl and Prompt L-Pop reapplication can decrease microleakage effectively.

When an amalgam restoration fails, the repair of existing amalgam restoration with fresh amalgam can be a practical alternative to the replacement of entire restoration. In most studies the bond strength of fresh amalgam to old amalgam is reported lower than the old amalgam itself. Therefore, the purpose of this study was to compare the effect of using adhesive system with surface irregularities and roughness on shear bond strength between fresh and set (old) amalgam. Methods and Materials: Fifty acrylic cylinders were made and a cavity preparation (6mm diameter by 2 mm high) was made in each cylinder. Forty cavities were filled with amalgam, level with cylinders surface and ten cylinders (control group=Groupl) were filled 5mm higher than the surface of cylinder using split die. After aging of all samples in water at 37º c for 14 days, the first 40 samples were divided into 4 groups and were repaired with fresh amalgam in the following manner. Group 2: with surface irregularities and roughness, group 3: using Panavia F, without surface irregularities and roughness, Group4: using cement and surface irregularities and roughness, group 5: without cement and without surface irregularities and roughness. After storage in water at 37ºc for 7 days, the shear bond strengths of groups were tested. Mean shear bond strengths and standard deviations (MPa) for groups were: in Group 1 (control): 36±4.8, Group 2: 31.26±2.70, Group 3: 8.07±1.34, Group 4: 13.05±183 and in Group 5 no bond was seen. ANOVA revealed statistically significant difference among groups Duncan test indicated that there was a significant difference between each group with the other one. Results of this study didnt reveal any advantages for using Panavia F to increase the bond strength. According to the results obtained from making surface roughness and irregularities compared to the control group, this procedure can be suggested for repairing broken amalgam as an acceptable procedure.

Since hygiene instructors can play important role in promoting and following oral hygiene instructions in schools, it was decided to investigate hygiene instructors’ knowledge and their attitudes about oral hygiene. This was qualitative-descriptive cross sectional study. Information was gathered by questionnaire containing 25 questions about knowledge and 8 questions about attitudes. 188 hygiene instructors were selected randomly among 278 hygiene instructors present in primary schools in Isfahan. After questionnaires were approved by specialists, they were completed by hygiene instructors. The data were analyzed by SPSS software program and statistical analysis was carried out with analysis of Variance, T-test, ANOVA and Spearman correlation. The average of personals’' knowledge was 18.53± 2. 78 and domain was 11 to 24 (Total mark: 25). The average of their attitude was 25. 7± 2. 7 (Total mark: 32). The T-test didnt show any relationship between altitude, knowledge and educational degree (i. c. Diploma VS bachelor degree). There was no relationship between work experience and educational degree work experience and attitude, knowledge and attitudes. The average of personals’' knowledge showed satisfactory results and positive attitude. Periodic instructions and supervising hygiene instructions in school can improve student's oral hygiene in school and this in turn can create healthier students overall.

The aim of this research was to evaluate the effect of surface treatment, clinical performance and the condition and position of the dental restoration on the corrosion behavior of dental amalgam. Commercial amalgam namely Oralloy was selected to prepare 21 flat amalgam samples. After triturating and condensation, the samples were divided into three groups and each group was finished by using one of the three clinical procedures carving, carving-burnishing, carving-burnishing-polishing. A special cylindrical mold was used in order to simulation of the inter-proximal areas and proximal surfaces of the dental restorations. Stainless steel matrix band was placed on the internal mold surfaces and amalgam paste was compacted in the mold and 14 cylindrical samples were prepared. Electrochemical tests were performed at a temperature of 37±1oC in normal saline in order to determine the corrosion behavior of dental amalgam samples. Tafel extrapolation and linear polarization methods determined corrosion potential and corrosion current densities. The mean value and standard deviations of the results were calculated. The mean values were statistically compared by ANOVA and Duncan methods at 95% level of confidence. The results showed statistically significant differences between the mean corrosion current density values of three different groups of dental amalgam(P<0.05). The carved group showed more corrosion resistance in comparison with the sample near the matrix band (P<0.05) as an index of the proximal surfaces of the dental restorations. Even a simple clinical performance could effect on the corrosion resistance of dental amalgam. The proximal surfaces of the class II restorations are not only susceptible to concentration cell corrosion but also possess less corrosion resistance.

Amalgam restorations often tarnish and corrode in the oral environment. The degree of tarnish and the resulting discoloration appear to be dependent on the parameters such as oral environment, oral hygiene, and the particular alloy employed and clinical procedures. The aim of this research was to evaluate and compare the effect of clinical procedures such as carving, carving-burnishing and carving-burnishing-polishing on the tarnish and corrosion behavior of four brand dental amalgams. Method & Materials: Four different type of commercial amalgam alloy powders with different powders with various particles shape (lathe cut, spherical, spheroids) namely Sybraloy (Sy), Cinalux (CL), Oralloy (Or) and cinaalloy (Ca) were studied. A special mold was used to prepare the samples of each type of commercial amalgams. Twenty-one samples of each type of amalgams were prepared. After trituration and condensation, the samples of each type of amalgams were divided into three groups and each group was finished by using one of three procedures carving, carving-burnishing, carving-burnishing-polishing. Electrochemical potentiodynamic tests were performed at a temperature of 37±1 °C in order to determine and compare the corrosion behavior of dental amalgams, as an indication of biocompatibility. The results showed statistically significant differences between the mean corrosion current densities values of three different groups of each type of commercial amalgam (P<0.05). The polished group of each type of commercial amalgams possesses the lowest corrosion current density and the carved group shows the highest corrosion current density (the lowest corrosion resistance). This trend was not affected by the brand and chemical composition of commercial amalgams. The polished Sybraloy amalgam possesses the highest corrosion resistance between four types of polished amalgams and the polished Cinaaloy amalgam showed the lowest corrosion resistance. The similar trend was observed in carved group and carved-burnished group of four types of amalgams. It was concluded that the clinical operations and procedures could influence the tarnish and corrosion behavior of high copper dental amalgams. Polishing procedure increases the corrosion resistance of high copper dental amalgams and is more effective on the corrosion behavior of dental amalgams, which are less corrosion resistant in compare with the dental amalgams that are more corrosion resistant.

Casting is one of the most popular processes for preparation of dental appliances and structures. The effect of melting and casting process on the corrosion behavior of dental appliances and prosthetics is important since the corrosion behavior of the dental metallic alloy is an indication of their biocompatibility in the mouth. The aim of this investigation was to evaluate the effect of laboratory casting and the recasting and use of return materials on the corrosion resistance of dental casting alloys. The ingot of two types of dental alloys (Co-Cr-Mo and Ni-Cr- Mo alloys) were used and enough coupons were prepared using the lost wax moldingtechnique and centrifugal casting process. The same process, using remelting andrecasting of the alloys, was performed to prepare the other samples for evaluating theeffect of the recasting and use of casting returns and scrape materials on the corrosionresistance of the casting alloys. Electrochemical potentiodynamic tests were performed inphysiological solution in order to determine and compare the corrosion behavior of dentalcasting alloy samples as an indication of biocompatibility. The results showed no statistically significant difference between the mean corrosion current density values of two groups of the Cr-Co-Mo alloy (melted once and melted four times). There were statistically significant differences between the meancorrosion current density values of three groups (melted once, melted four times, andmelted five times) of the Ni-Cr-Mo alloy (p<0.05). The five times melted dental castingalloy possessed the lowest corrosion resistance. This was due to the undesired effect ofrecasting process on the corrosion characteristics of dental casting alloys and it seems thatthe condition and parameters of the casting process is not stable every time.

In this study, the relative frequency of factors, that cause the necessity for replacement of dental amalgam restorations in patients referred to Operative Department of Isfahan Dental School was clinically and radiographic evaluated (year: 2000 2001). In addition, the prevalence of diagnostic instances through clinical examination and radiographic inspection was compared. Four hundred cases were included in this study. The type of research was descriptive. Regular explorer, plain mouth mirror, dental floss and light of dental unit were utilized for clinical registration. Isolation was performed by saliva ejector and cotton roles. Bitewing radiography technique was used for radiographic inspection. Relative frequency of secondary caries, overhang, tooth fracture, amalgam bulk fracture and marginal fracture were 66.25 %, 23.5 %, 19.5 %, 15.25 %, 23.5 %, and 4.5 %, respectively. There was no significant difference in diagnosis overhang between the results of the clinical examination and the radiographic inspection. In other instances, clinical examination
had a significant more diagnostic value. The high relative frequency of recurrent caries factor indicates the importance of proper cavity preparation, optimal material selection and accurate material manipulation, and also oral hygiene education to the patients.

Nowadays, application of implants as a new method for replacing extracted teeth have been improved. So, many researches have been performed for improving the characteristics of implants. The aim of this study was to design and produce a desired coating in order to obtaining two goals including improvement of the corrosion behavior of metallic endodontic implant and the bone osseointegration simultaneously. Stainless steel 316L (SS), cobalt-chromium alloy (Vit) and commercial pure titanium (cpTi) were chosen as metallic substrates and hydroxyapatite coating (HAC) were performed by plasma-spraying (PS) process on three different substrates. A novel double layer Hydroxyapatite/Titanium (HA/Ti) composite coating composed of a HA top layer and a Ti under layer was prepared using PS and physical vapor deposition (PVD) process respectively on SS. Structural characterization techniques including XRD, SEM and EDX were utilized to investigate the microstructure, morpholgy and crystallinity of the coatings. Electrochemical potentiodynamic tests were performed in physiological solutions in order to determine and compare the corrosion behavior of the coated and uncoated specimens behavior as an indication of biocmpatibility. Results indicated that the cpTi possesses the highest and SS the lowest corrosion resistance (highest corrosion current density) between uncoated substrates. This trend was independent to the type of physiological environment. The HA coating decreased the corrosion current density of HA coated metallic implants but did not change that trend. HAC acted as a mechanical barrier on the metallic substrate but could not prevent the interaction between metallic substrate and environment completely. The HA/Ti composite coating improved the corrosion behavior of SS. The corrosion current density of HA/Ti coated SS decreased and was exactly similar to single HA coated cpTi in physiological solutions. The results indicated that HA/Ti composite coated SS could be used as an endodontic implant and two goals including improvement of corrosion resistance (biocompatibiiity) and bone osseointegration could be obtained simultaneously.

Bone osseointegration around dental implant can cause earlier stabilization and fixation of implant and reduce healing time. Hydroxyapatite coating can affect bone osseointegration and enhance its rates. The aim of this study was comparison of osseointegration between plasma sprayed hydroxyapatite coated and uncoated dental implants in cats. Four endodontic implants including, vitallium and two stainless steel with and without hydroxyapatite coating were prepared and placed in mandibular canines of 20 cats after completion of root canal treatment and osseous preparation. After a healing period of 4 months, investigation by scanning electron microscopy showed significant difference in ossointegration between coated and uncoated dental implants and average bone osseointegration of coated implants was more than uncoated implants.