Zahra Khamverdi

Background: The preventive treatments of primary caries lesions are essential for preventing destructive damage to the tooth structure. One of the common treatments is the application of casein phosphopeptide-amorphous calcium phosphate (CCP/ACP) paste on the enamel surface. The aim of this study was to investigate the effect of different percentages of nano-bioactive glass (nBG) incorporation into synthesized CPP/ACP paste on the remineralization of demineralized enamel. Methods: In general, 24 extracted human intact premolar teeth were selected, and their crowns were removed for this purpose. Each crown was cut into two halves, and each half was considered as a sample. The samples were placed in a demineralizing solution at a pH rate of 4.6 for 8 hours, in artificial saliva for 1 hour, and again in a remineralizing solution at a pH rate of 7 for 15 hours. The pH cycling was performed for 14 days to demineralize the enamel surface. The samples were randomly divided into 3 groups (n=16), including G1 (without treatment), G2 (treated with synthesized CPP/ ACP paste containing 5% nanobioglass), and G3 (treated with synthesized CPP/ACP paste containing 10% nanobioglass). The paste was then placed directly on the surface of the demineralized enamel for 4 minutes (twice a day for 28 days). The samples were subjected to the Vickers microhardness test. Finally, data were analyzed using SPSS (version 19) and the analysis of variance and Tukey’s tests (α = 0.05). Results: There was a significant difference between microhardness values in G1 and G2, as well as G1 and G3 (P0.05). Conclusions: The results showed adding bioactive glass into synthetic CPP/ACP paste increases enamel remineralization in spite of the percentage of bioactive glass incorporation.

Background: Clinical long-term success of bonded restorations is depended to reduce marginal microleakage and the laser application with combination of new bonding systems may play positive role. The aim of this study was comparative evaluation of Er,Cr:YSGG and Nd:YAG lasers effect on microleakage of class V composite resin restorations using several universal adhesives. Methods: In this in vitro study, standard class V cavities were prepared on both lingual and buccal surfaces of 72 intact premolar teeth. For evaluation of microleakage, the cavities were divided into 9 groups according to conditioning method (n=15): G1: G-Premio Bond [GP]; G2: Scotchbond Universal Adhesive [SU]; G3: All-Bond Universal [AB]; G4: GP+Nd:YAG Laser; G5: SU+Nd:YAG Laser; G6: AB+Nd:YAG Laser; G7: GP+Er,Cr:YSGG Laser; G8: SU+Er,Cr:YSGG Laser; and G9: AB+Er,Cr:YSGG Laser. The cavities were filled with composite resin and then subjected to thermocycling, placed in methylene blue solutions, embedded in resin blocks and vertically cut in the bucco­lingual direction. The microleakage in occlusal and gingival margins was defined as linear penetration of methylene blue and determined with a stereomicroscope to assign microleakage scores using a four­point scale. Data were analyzed by using SPSS software and Kruskal-wallis and Mann-Whitney U tests. Results: Microleakage scores had statistically significant different before and after laser irradiation in dependent to the adhesive used (P<0.05) but there were no significant different between Nd:YAG and ER,Cr:YSGG laser, also between different universal adhesives (GP, SU, AB). The results showed that total microleakage scores of occlusal margins had significant statistical different in comparison with gingival margins (P<0.001). Conclusion: The results indicate that Nd:YAG and Er,Cr:YSGG lasers irradiation, after using the investigated universal adhesives, had a positive effect on reducing the microleakage of composite Class V restorations. The microleakage rate was shown to be independent of adhesives and lasers type used in this study.

Background: Academic dishonesty is the most important educational concern. According to previous studies, it is more common in several groups of students. To prevent academic dishonesty, it is important to know the extent of the problem. Accordingly, this study was designed to investigate the behaviors, attitudes, and interpretations of dental students regarding exam fraud in the 2015-2016 academic years. Methods: For this purpose, a three-part questionnaire was prepared, including demographic characteristics and specific questions. The specific questions included students’ behavior, attitudes, and interpretation in the form of three scenarios. A total of 163 questionnaires were collected, and the statistical analysis was performed using SPSS, version 20. The Mann-Whitney U test and the Kruskal-Wallis test were used to analyze the data. Results: The students consisted of 90 males (55.2%) and 73 females (44.8%), and their average age was 22.72±2 years (22.3±2.87 and 23.23±2.37 years for boys and girls, respectively). The results revealed that around 65.6% of students were generally aware of the fraud problem in the faculty and knew the cheaters (63.1%). Further, 55.2% of students believed that instructors should prevent cheating during the exam. Data analyses demonstrated that there were no significant differences between boys and girls in all research variables. Finally, the average behavior proportion and attitude of the first-year students were higher than those of other students. Conclusion: Based on the findings, the rate of fraud was high in dentistry schools and possibly in other medical schools, highlighting the importance of the creating culture in changing students’ attitudes.

Background: The methods of increasing the longevity of dental burs by improving the mechanical properties of these surfaces, can increase their longevity. This study assessed the effect of diamond-like carbon (DLC) coating applied by the physical vapor deposition (PVD) technique on wear of diamond and tungsten carbide (TC) burs. Methods: In this in vitro study, 30 diamond and 30 TC burs were evaluated in four groups, including TC burs without coating (control), TC burs with a 3.5-µm DLC coating applied by the PVD technique, diamond burs without coating (control), and diamond burs with a 3.5-µm DLC coating applied by the PVD technique. The burs were weighed by a digital scale, underwent the pin-on-disc wear test, and were weighed again. The weight loss indicated the degree of wear in each group. For qualitative assessments, the surface of the burs was inspected under a stereomicroscope at×4 and×10 magnifications before wear, halfway through the test, and after the test. Finally, the data were analyzed by two-way ANOVA (α=0.05). Results: The effect of DLC coating was significant on the wear of burs (P=0.032), but the effect of the type of bur and their interaction effect on wear were not significant (P=0.151). A significant difference existed in wear among the four groups (P < 0.001), and the wear of coated burs was significantly lower than that of non-coated burs (P=0.012). Stereomicroscopic assessments revealed some residual diamond particles, the impression of dislodged particles and the path of wear on the surface of diamond burs, and the path of wear on the surface of TC burs. Conclusions: Overall, the DLC coating of diamond and TC dental burs by the PVD technique could increase their wear resistance irrespective of the bur type.

Background: To establish a good and effective relationship between a doctor and his/her patient, certain non-verbal standards are as necessary as knowledge and skills. According to evidence, one of these standards may be the dentist’s attire. Therefore, this study aimed to determine the effect of dental students’ dressing on patients’ trust and confidence. Methods: This cross-sectional descriptive study was performed to evaluate the perception of dental school patients. After reviewing pictures of dental students in six different dress styles, the respondents were asked some questions on their preference for dental students’ attire, as well as several questions targeting patients’ trust and confidence. The collected data were analyzed using SPSS 16. Results: In the present study, 169 respondents with a mean age of 27.5 years old were enrolled, including 47% men and 53% women. The included respondents significantly favored male dentists with a long white coat and surgical scrubs and preferred a long white coat with a white scarf for women (P<0.001). They believed that dentists with this attire are more knowledgeable, skilled, and professionally competent, and they were more appealing to share their personal issues with this kind of dentist. Conclusions: The respondents preferred dental students in professional attire. Wearing professional dress (a white coat) could have a favorable effect on patients’ trust and confidence.

Objective: Nanomaterials with superior properties such as high surface area over volume ratio are widely used in dentistry and medicine. This in vitro study was performed to synthesize and characterize nano bioactive glass (nBG) and to evaluate the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) containing nBG (CPP-ACP@nBG) on enamel remineralization by its application to pH-cycled, synthetically demineralized enamel surfaces. Materials and methods: nBG particles were prepared by sol-gel method. X-ray diffraction pattern (XRD), Fourier-transform infrared spectroscopy (FTIR) and transmittance electron microscopy (TEM) were used for nBG characterization. Synthetic CPP-ACP paste was prepared and nBG particles were added to it. To evaluate the degree of remineralization, 32 healthy human premolars were selected. The samples were randomly divided into 4 groups as: Group 1: Commercial CPP-ACFP (MI paste plus), Group 2: Synthetic casein phosphopeptide-amorphous calcium phosphate containing fluoride (CPP-ACP@F), Group 3: Synthetic CPP/ACP containing nBG (CPP-ACP@nBG), and Group 4: Control (received no treatment). The pastes were then applied on the tooth surfaces for 28 days. The Vickers microhardness of enamel surfaces was evaluated, and enamel surface morphology was assessed using scanning electron microscopy (SEM). Results: X-Ray diffraction pattern (XRD) of the synthesized nBG show its crystalline nature with the Larnite crystalline mode. Transmittance electron microscope (TEM) microimage of the synthesized nBG shows its formation as less that 100 nm spherical nanoparticle with partial agglomeration. Fourier transform infrared spectroscopy (FTIR) confirm the success formation of nBG with high purity. The results of this study showed that microhardness of the experimental groups was significantly higher than the control group (p ≥ 0.05). SEM images showed a layer of hydroxyapatite in the CPP-ACP@nBG, synthetic and commercial CPP-ACP@F remineralized groups. Conclusion: The results of this study demonstrated that CPP-ACP@F and CPP-ACP@nBG remineralize the surface of the demineralized enamel. Microhardness of the remineralized enamel in the CPP-ACP@nBG group was higher than synthetic and commercial CPP-ACP@F groups.

Background: Reports indicate that lasers accelerate tooth bleaching by activating bleaching agents. Due to the lack of sufficient information about the application of the Er, Cr:YSGG laser, the present study was conducted to compare the degree of enamel color changes after teeth bleaching treatment using chemical whitening agents alone and with Er, Cr:YSGG laser. Methods: In this laboratory study, several human molars were cut into 4 parts after cutting and removing the pulp. Based on laser application, the samples were randomly divided into two groups (N=20), including the chemical bleaching group (G1) and the chemical bleaching group with activated laser (G2). In G1, the bleaching process was performed only with 35% hydrogen peroxide for two weeks (3 times, 15 minutes each week). In G2, the gel bleaching was activated by the Er, Cr:YSGG laser with a wavelength of 2780 nm. It was placed 2.5 cm from the sample surface with bleaching agents and applied twice for 15 seconds. Color changes were recorded using a spectrophotometer before bleaching, immediately after, 1 month, and 3 months after bleaching. Data were analyzed by SPSS software (version 18), Repeated measures ANOVA, and Tukey’s tests (α=0.05). Results: Mean and standard deviation of changes in Δa showed a significant difference between the gel group and the gel group with laser over time (P0.05). However, the intragroup comparison demonstrated significant changes in Δa and Δb in both groups over time, but not in ΔL (P>0.05). The ΔE changes in both the laser and bleaching gel groups were above the threshold of 3.3. The results indicated no significant difference between G1 and G2 in terms of the ΔE (P>0.05). Finally, the results revealed that 1 and 3 months after teeth whitening, ΔE changes in both groups were greater than 3.3. Conclusions: Overall, the application of the Er, Cr:YSGG laser had no positive effect on bleaching efficacy when using a 35% hydrogen peroxide gel. Based on the findings, color changes were stable in the studied groups for up to 3 months after teeth bleaching.

Background: Matrix metalloproteinase-8 (MMP-8) is the most abundant member of the MMP family in human dentin. It takes a part in the normal physiology of tissue remodeling and wound healing, while the overexpression/hyperactivity of this protein leads to several oral disorders, including dental caries and peri-implant inflammation/diseases, and therefore, MMP-8 inhibition may have therapeutic effects. Accordingly, the current study aimed to identify potential MMP-8 inhibitors from cinnamic acid derivatives. Methods: The binding affinity of cinnamic acid and its several derivatives to the MMP-8 active site were estimated using the AutoDock 4.0 software. The pharmacokinetics, toxicity, and bioavailability of top-ranked MMP-8 inhibitors were also predicted by utilizing bioinformatics web tools. Results: Five of the studied components, including chlorogenic acid (CGA), caffeic acid 3-glucoside, rosmarinic acid, N-p-Coumaroyltyramine, and caffeic acid phenethyl ester (CAPE) demonstrated a salient affinity of binding to the MMP-8 catalytic site (∆Gbinding<-10 kcal/mol). It was estimated that these compounds can inhibit the MMP-8 at the nanomolar concentration, and therefore, were considered as top-ranked MMP-8 inhibitors. Finally, none of the top-ranked components revealed a considerable side effect and thus were found to be suitable for oral use. Conclusions: The results of the present study suggested that CGA, caffeic acid 3-glucoside, rosmarinic acid, N-p-coumaroyltyramine, and CAPE might have protective effects on tooth decay and peri-implant inflammation/diseases.

Background: Dental caries is one of the most common oral chronic diseases. Streptococcus mutans is the main pathogenic bacteria playing a role in degrading the mineral texture of the teeth. Glucosyltransferase (GTFase) of S. mutans is responsible for producing glucan, which is the main exopolysaccharide found in the cariogenic biofilms. Further, previous studies have reported that cinnamic acid diminished biofilm formation of S. mutans. Therefore, we hypothesized that cinnamic acid and its derivatives might act as GTFase inhibitors. Methods: The binding affinity of a total of 12 plant-based compounds including cinnamic acid and its 11 derivatives to the GTFase active site were examined by utilizing the AutoDock tool. The possible interactions between top-ranked cinnamic acid derivatives and the residues within the GTFase catalytic site were also taken into consideration. Results: Five of the cinnamic acid derivatives including rosmarinic acid (RA), cynarine, chlorogenic acid (CGA), caffeic acid 3-glucoside, and N-p-coumaroyltyramine demonstrated inhibitory effects on GTFase at nanomolar concentration. Stabilizing interactions such as π–π stack pairing and pi-charge interactions were detected between top-ranked GTFase inhibitors and residues within the enzyme active site. Conclusions: The present study suggests that RA, cynarine, CGA, caffeic acid 3-glucoside, and N-p-coumaroyltyramine might have protective effects on dental caries, and therefore, may be considered as anti-tooth caries compounds.

Background: Extending the lifespan and improving the physical properties of dental burs as the most extensivly used instruments have been the subject of several studies. One of the proposed methods is using surface coatings for the burs. Since the dental instruments are reused, they require sterilization. One of the possible causes of the damage to dental burs is autoclaving process. This study aimed to investigate sterilization (autoclave) effect on wear of diamond coated tungsten-carbide burs with different thicknesses. Methods: In this in vitro study, 40 tungsten-carbide dental burs (IQ DENT, Poznan, Poland) were selected, out of which 20 burs were coated with 1.5-μm-like diamond particles, and 20 burs were coated with 3.5-μm by PVD method using Swin Plasma Coating Machine. Then, the burs were randomly divided into four groups (n=10) as follow: G1: 1.5 μm thickness coated burs without sterilization; G2: 3.5 μm thickness coated burs without sterilization; G3: 1.5 μm coated with sterilization; and G4: 3.5μm thickness coated burs with sterilization. Their weights were measured before wear test.Wear test was performed and then they were re-weighted. Data were analyzed using SPSS software (version 21) as well as Two-way ANOVA and Tukey HSD supplementary tests (α=0.05). Results: Mean and standard deviation of the burs weights without sterilization in the control groups were 7.31±2.63 and 7.96±1.61 mg, respectively; and mean and standard deviation of the burs weights in the sterilization groups were 7.06±0.98 and 7.12±1.11 mg, respectively. The study results showed that "sterilization application" and "thickness of coated layer" were the main factors and their intraction had no statistically significant difference (P=0.589). Conclusions: The sterilization process had no effect on wear of diamond coated tungsten-carbide burs with different thicknesses.