Effectiveness of plant-mediated synthesis of hydroxyapatite nano-particles impregnated in Pistachio oleogum resin on mineral contents of human teeth. An in-situ single-blind controlled study.

OBJECTIVES: This study aimed to synthesize and characterize an environmentally friendly nanohydroxyapatite (n-HA) and evaluate its impact on enamel mineral content when incorporated into a Pistachio oleo gum resin (Saqqez) bio-chewing gum for in-situ models. We compared the effects of this green nano-hydroxyapatite (G n-HA) with those of a commercially available synthetic nano-hydroxyapatite (S n-HA). METHODS: Various analytical techniques were employed including XRD, FESEM, FT-IR, EDX/SEM and TGA/DTA to characterize the crystallinity, size and composition of the G n-HA powder. Three chewing gum groups were formulated: (1) Saqqez gum containing 10% wt G n-HA, (2) Saqqez gum containing 10% wt S n-HA, and (3) pure Saqqez gum. In order to evaluate the impact of these chewing gums on enamel, intraoral appliances were fabricated, each containing six enamel specimens. Participants were instructed to chew the gums while wearing these appliances. The calcium (Ca+2) and phosphorus (P) levels in enamel specimens, both with and without exposure to an acid challenge, were quantified using EDX/SEM. FE-SEM was employed to capture the microstructure of the enamel surface. In terms of the statistical analysis, one-way ANOVA and Tukey's post hoc tests were utilized to compare the data, where the significance level (α) was set at 0.05. RESULTS: The characterization tests confirmed the successful synthesis of G n-HA. Furthermore, EDX/SEM analysis of the enamel specimens from the intraoral appliance revealed significant variations in calcium (Ca+2) content among the enamel specimens (P = 0.000). The S n-HA group, in particular, exhibited the highest Ca+2 content, while the pure Saqqez group displayed the lowest. Nonetheless, there was no statistically significant differences in phosphorus (P) content observed among the three groups (P = 0.27). CONCLUSIONS: Saqqez gum can be considered a wholesome natural chewing gum that serves, as a carrier for delivering remineralization agents to the tooth surfaces. This was evident in the groups containing n-HA, exhibiting elevated Ca+2 levels. It's noteworthy that G n-HA demonstrated less efficacy in enamel remineralization compared to S n-HA.

Evaluating the Effect of Sumac Extract on Dentine Micro-Hardness during pH Cycling.

Statement of the Problem: Although sumac extract (SE) is reported as a collagen cross linker, the available data regarding its effect on the dentine micro-hardness is quite sparse. Purpose: Therefore, the aim of this study includes evaluating the effect of different concentrations of SE on dentine micro-hardness comparing to grape seed extract (GSE). Materials and Method: In this experimental study, the GSE was purchased from available market and convert to 5% solution. Meanwhile the 5, 10, and 20% of SE solutions were prepared experimentally. The base line micro-hardness of 60 samples (30 premolars divided to buccal and lingual segments) was recorded triplicate for each specimen and they were randomly divided into 5 groups (four abovementioned experimental solutions and de-ionized water as negative control). For 35 consecutive days, each sample was twice pH cycled and treated by solutions. Ultimately, the final micro-hardness was recorded triplicate again for each sample and the numerical data was compared with each other using one-way ANOVA and Tukey HSD Post Hoc tests (α=0.05). Results: The meanSD values of micro-hardness for the groups was recorded as 54.45 13.4, 65.6518.5, 39.572.26, 41.131.66 and 43.794.96 at base line and 10.40.99, 11.85 0.75, 10.161.84, 8.481.16 and 6.311.01 at final stage for control, GSE 5%, SE 5%, SE 10% and SE 20% respectively. There was no significant difference among the micro-hardness of the groups before treatment (p= 0.369). However, after experimental treatment, there was significant difference between the groups (p= 0.024) while in pairwise comparison just two groups (GSE 5% and SE 20%) had significant difference with each other (p= 0.017). Conclusion: The efficacy of SE was reversely related to its concentration. Moreover, neither GSE nor SE had significant effect on dentine micro-hardness after 35 day pH cycling.

Evaluating the Effect of an Experimental Sesame Gel on Human Enamel: Atomic Force Microscopy Study.

Statement of the Problem: Every effort for increasing the calcium concentration in the saliva would be beneficial for prevention of dental caries. Regarding this issue, the natural products could be considered safer and more cost effective. Sesame is rich in calcium but the data about the effect of sesame on enamel roughness is inadequate. Purpose: This study aimed to assess the effect of an experimental sesame gel on the surface roughness of human enamel by using atomic force microscopy (AFM). Materials and Method: In the current experimental study, fifteen enamel slices with 1mm thickness were prepared. They were polished and acid etched to produce a substantial rough surface prior to the first AFM analysis. The enamel blocks were randomly divided into three groups treated with distilled water, fluoride gel, and an experimental prepared sesame gel correspondingly. The treating agent was applied for 3minutes at 0, 8, 24, and 48h intervals and washed by distilled water after each cycles. Ultimately, the final AFM micrographs were prepared. The statistical analysis was performed using paired t-test, one-way ANOVA, and Tukey Post Hoc tests (α=0.05). Results: Statistical analysis revealed that the surface roughness was significantly reduced in both sesame and fluoride groups (p= 0.017 and 0.018, respectively) while the control group (distilled water) were not noticeably changed (p= 0.12). The control group had statistically significant difference with both the sesame and the fluoride groups (p= 0.007 and 0.007, respectively) while the there was no significance difference between sesame and fluoride groups (p= 0.997). Conclusion: Following demineralization by acid etched process, the sesame gel significantly reduced surface roughness of enamel and its effect was similar to fluoride gel.

Evaluating the Effect of Oblique Ridge Conservation on Stress Distribution in an Endodontically Treated Maxillary First Molar: A Finite Element Study.

INTRODUCTION: Although the maxillary first molar (MFM) has been frequently subjected to stress analysis in endodontic investigations, the available data about the effect of its oblique ridge are quite sparse. The aim of this study includes evaluating the effect of the residual oblique ridge on the stress distribution after preparing conservative access cavities. METHODS: Based on the cone-beam computed tomographic data, the model of an intact MFM and 5 cavity designs were prepared for endodontic treatment, which were consequently filled with gutta-percha and dental resin composite (6 total models). All models were subjected to 4 types of occlusal loading; finite element analysis via ABAQUS CAE software (Dassault Systemes, Vélizy-Villacoublay, France) was accomplished, whereas other software programs such as (Mimics Research Materialise, Leuven, Belgium) and 3-Matic Research (Materialise) were also incorporated in different stages for detecting stress distribution. RESULTS: The stress distribution on the MFM is not only dependent on the remaining width of the oblique ridge but also on the type of loading. The most stress on the cervical region was concentrated on the palatal root in some type of loading, whereas the least stress on the occlusal surface was recorded when the whole oblique ridge was replaced by the composite resin. CONCLUSIONS: When the occlusal contacts are occurring only on the palatal cusp, the stress distribution on the oblique ridge is noticeably affected by the cavity design.

Antibacterial, physical and mechanical properties of bonding agent containing synthesized Zinc Dimethacrylate.

BACKGROUND: The aim of this study includes synthesis of zinc dimethacrylate ionomer (ZDMA) by a new method, incorporate it into resin bonding and evaluate its antibacterial, physical and mechanical properties. MATERIAL AND METHODS: Resin adhesives containing 0 to 5% wt of ZDMA was produced and the following tests were accomplished: A: Antibacterial test: 1.Direct contact test. 2.Material aging; in both of them the bacterial colony counting were performed. B: Physical test: 1.Degree of conversion (D.C). 2.Evaluating the amount of released Zinc ion release in aqueous medium. C: Mechanical test: 1.Compressive strength test. 2.Shear bond test (enamel and dentine separately). The obtained results were statistically analyzed using One Way ANOVA and LSD post hoc test (α=0.05). RESULTS: The anti-bacterial test revealed that all the ZDMA containing groups significantly reduced the amount of Streptococcus Mutans bacteria. Moreover, the D.C in all ZDMA groups was enhanced. Furthermore, ion release analysis revealed noticeable stability of Zn2+ in samples, as in the 5wt.% group it was even after nine cycle of 24h wash. On the other hand, the compressive strength was significantly reduced just in the 5% ZDMA group while the other groups were superior comparing to the control. In addition, there was no significant difference among the enamel shear bond strength of the groups. However, about the dentine shear bond strength, only the 5% ZDMA group was significantly higher than the control. CONCLUSIONS: Low percentages of ZDMA in adhesive could impart anti-bacterial efficacy without challenging its mechanical and physical properties. Key words:Dental Resin Bonding, Zinc, Streptococcus mutans, Degree of conversion, Compressive strength.

Thermal Scanning of Dental Pulp Chamber by Thermocouple System and Infrared Camera during Photo Curing of Resin Composites.

INTRODUCTION: Due to thermal hazard during composite restorations, this study was designed to scan the pulp temperature by thermocouple and infrared camera during photo polymerizing different composites. METHODS AND MATERIALS: A mesio-occlso-distal (MOD) cavity was prepared in an extracted tooth and the K-type thermocouple was fixed in its pulp chamber. Subsequently, 1 mm increment of each composites were inserted (four composite types were incorporated) and photo polymerized employing either LED or QTH systems for 60 sec while the temperature was recorded with 10 sec intervals. Ultimately, the same tooth was hemisected bucco-lingually and the amalgam was removed. The same composite curing procedure was repeated while the thermogram was recorded using an infrared camera. Thereafter, the data was analyzed by repeated measured ANOVA followed by Tukey's HSD Post Hoc test for multiple comparisons (α=0.05). RESULTS: The pulp temperature was significantly increased (repeated measures) during photo polymerization (P=0.000) while there was no significant difference among the results recorded by thermocouple comparing to infrared camera (P>0.05). Moreover, different composite materials and LCUs lead to similar outcomes (P>0.05). CONCLUSION: Although various composites have significant different chemical compositions, they lead to similar pulp thermal changes. Moreover, both the infrared camera and the thermocouple would record parallel results of dental pulp temperature.

The synergistic effect of honey and cinnamon against Streptococcus mutans bacteria

Objeetive:To investigate the effect of Iranian honey,cinnamon and their combination against Streptococcus mutans bacteria.Methods:Nine experimental solutions were examined in this study,including two types of honey (pasteurized and sterilized),two types of cinnamon extract (dissolved in distilled water or dimethyl sulfoxide) and five different mixtures of cinnamon in honey (prepared by admixing 1％-5％ w/w of cinnamon extract into 99％-95％ w/w of honey,respectively).Meanwhile,each of mentioned agent was considered as the first solution while it was diluted into seven serially two-fold dilutions (from 1∶2 to 1∶128 v/v).Therefore,eight diffcrent concentrations of each agent were tested.The antibacterial tests were performed through blood agar well diffusion method,and the minimum inhibitory concentration (MIC) was determined.Ultimately,the data were subjected to statistical analysis incorporating Two-way ANOVA and Bonferroni post hoc tests (α =0.01).Results:The highest zone of inhibition was recorded for the mixtures of honey and cinnamon while all the subgroups containing 95％-99％ v/v of honey were in the same range (P ＜ 0.01).The MIC for both honey solutions were obtained as 500 mg/mL whereas it was 50 mg/mL for both cinnamon solutions.Moreover,the MIC related to all honey/cinnamon mixtures were 200 mg/mL.Conclusions:A profound synergistic effect of honey and cinnamon was observed against Streptococcus mutans while there was no significant difference among extracts containing 99％-95％ v/v of honey admixing with 1％-5％ v/v of cinnamon,respectively.

Nano-hydroxyapatite could Compensate the Adverse Effect of soft carbonated Drinks on Enamel.

INTRODUCTION: Since one of the most important disadvantages of soft drinks includes their adverse effect on mineral content of enamel because of their low pH, this study examined the microhardness of enamel before and after exposure to a soft drink containing different concentrations of nano-hydroxyapatite (nano-HA) as an additive. MATERIALS AND METHODS: Sixty caries free human premolars were mounted in epoxy resin. After polishing, the baseline micro-hardness was recorded three times for each specimen using a Vickers indenter at 50 gm load. Subsequently, the samples were divided into six groups, which were treated for 5 minutes at 9°C by a cola-based drink contacting 0, 0.5, 1, 5, and 10 wt.% of nano-HA while the control group was immersed in artificial saliva. Ultimately, the final microhardness was assessed three times again for each specimen. RESULTS: Paired t-test showed that in groups containing 0 and 0.5 wt.% of nano-HA, the microhardness was significantly reduced after treatment protocol (p = 0.00 and 0.01 respectively). Whereas in the other groups the microhardness was not significantly changed after treatment (p > 0.05). CONCLUSION: Pure cola-based drink has a pronounced adverse effect on enamel microhardness, while admixing it with nano-HA could act as a protective factor. CLINICAL SIGNIFICANCE: Although soft beverages are hazardous to tooth structure, some additives could compensate their adverse effect.

The effect of silica nanoparticles on the mechanical properties of fiber-reinforced composite resins.

Background. Nanotechnology has introduced many nanoparticles in recent years, which can be incorporated for mechanical improvement of dental materials. However, the existing data are widely sparse. This study investigated the reinforcing effect of silica nanoparticles when incorporated into the matrix phase of an experimental dental fiber-reinforced compositeresin (FRC) through evaluation of its flexural properties. Methods. In this experimental study FRC samples were divided into two main groups (containing two or three bundles),either of whic consisted of five subgroups with 0, 0.2, 0.5, 2 and 5 wt% of silica nanoparticles in the matrix resin (n=10 in each subgroup); a commercial FRC (Angelus, Brazil) was used as the control group (n=10). Three-point bending test was performed to evaluate the flexural strength and modulus. Thereafter, the microstructure of the fractured samples was evalu-ated using scanning electron microscopy (SEM). The results were analyzed with one-way ANOVA and HSD Tukey tests (α = 0.05). Results. The results revealed that the silica nanoparticles had a significant and positive effect on the flexural strength and modulus of FRCs (P<0.05), with no significant differences from 0.2 to 5 wt% of nanoparticles (P > 0.05) in either group with two or three bundles of fibers. Conclusion. Incorporating silica nanoparticles into the FRC resin phase resulted in improved flexural strength and modulus of the final product.

Effect of Nano-Tricalcium Phosphate and Nanohydroxyapatite on the Staining Susceptibility of Bleached Enamel.

Objective. This study was designed to evaluate the effect of nano-tricalcium phosphate (n-TCP) and nanohydroxyapatite (n-HAP) on prevention of restaining of enamel after dental bleaching. Methods. Forty bovine incisors were bleached with 20% carbamide peroxide for two weeks. Afterward, they were divided into five groups based on remineralization solution: no treatment (control), 10% n-TCP, 5% n-TCP, 10% n-HAP, and 5% n-HAP. Each group was daily immersed for 10 minutes in the restaining solution (tea) and for 3 minutes in the remineralization agent, respectively. This protocol was repeated for five days. Subsequently, three digital photographs (baseline, after bleaching, and after restaining) were analyzed by Adobe Photoshop software. The obtained L (∗) , a (∗) , b (∗) , and ΔE parameters were compared using ANOVA and Wilcoxon and Bonferroni tests. Results. After bleaching, there were significant changes in tooth colors (P < 0.001) while, after restaining and immersion in remineralization solutions, there were no significant differences in L (∗) , a (∗) , and b (∗) values of different groups (P > 0.05). However, ΔE of 10% TCP was significantly lower than the control (P = 0.02) while there were no significant differences between the other groups (P > 0.05). Conclusion. 10% n-TCP could significantly maintain the resultant color and reconstruct the enamel structure after bleaching.

Effect of fiber diameter on flexural properties of fiber-reinforced composites.

BACKGROUND: Flexural strength (FS) is one of the most important properties of restorative dental materials which could be improved in fiber-reinforced composites (FRCs) by several methods including the incorporation of stronger reinforcing fibers. AIM: This study evaluates the influence of the glass fiber diameter on the FS and elastic modulus of FRCs at the same weight percentage. MATERIALS AND METHODS: A mixture of 2,2-bis-[4-(methacryloxypropoxy)-phenyl]-propaneand triethyleneglycol dimethacrylate (60/40 by weight) was prepared as the matrix phase in which 0.5 wt. % camphorquinone and 0.5 wt. % N-N'-dimethylaminoethyl methacrylate were dissolved as photoinitiator system. Glass fibers with three different diameters (14, 19, and 26 µm) were impregnated with the matrix resin using a soft brush. The FRCs were inserted into a 2 × 2 × 25 mm3 mold and cured using a light curing unit with an intensity of ca. 600 mW/cm2 . The FS of the FRCs was measured in a three-point bending method. The elastic modulus was determined from the slope of the initial linear part of stress-strain curve. The fracture surface of the composites was observed using scanning electron microscopy to study the fiber-matrix interface. STATISTICAL ANALYSIS: The results were analyzed and compared using one-way ANOVA and Tukey's post-hoc test. RESULTS: Although the FS increased as the diameter of fibers increased up to 19 µm (P < 0.05), no significant difference was observed between the composites containing fibers with diameters of 19 and 26 µm. CONCLUSION: The diameter of the fibers influences the mechanical properties of the FRCs.

Antibacterial, physical and mechanical properties of flowable resin composites containing zinc oxide nanoparticles.

OBJECTIVES: The aim of this study is evaluating the antibacterial activity of resin composites containing ZnO nanoparticles against Streptococcus mutans and examining their physical and mechanical properties. METHODS: The properties of flowable resin composites containing 0-5wt.% nano-ZnO are investigated using different tests: RESULTS: Although the agar diffusion test reveals no significant difference between the groups, the direct contact test demonstrates that by increasing the nanoparticle content, the bacterial growth is significantly diminished (p<0.05). In the aging test, however, the antibacterial properties reduce significantly (p<0.05). The flexural strength and compressive modulus remains unchanged by incorporation of nanoparticles (p>0.05) while the compressive strength and flexural modulus significantly increase (p<0.05). The ZnO containing resins show significantly lower depth of cure (p<0.05), and higher bond strength (p<0.05). There is no significant difference between the degrees of conversion, measured by FTIR technique, of the groups (p>0.05). SIGNIFICANCE: Production of a dental resin composite with antibacterial activity without significant sacrificing effect on the mechanical properties is desirable in dental material science.

Comparison of two canal preparation techniques using mtwo rotary instruments.

INTRODUCTION: Root canal preparation is an important process in endodontic therapy. Nickel-titanium (NiTi) rotary file system can be used in single length technique (simultaneous technique) without early coronal enlargement, as well as in crown-down method. The purpose of this in vitro study was to compare single length with crown-down methods' shaping ability using Mtwo NiTi files. MATERIALS AND METHODS: Fifteen acrylic-resin blocks containing simulated canals were divided into two experimental groups. In group A, single length technique was used and in group B root canals were prepared by crown-down technique. Pre- and post-preparation canals were photographed in a standardized manner and were superimposed. The inner and outer walls of canal curvature were evaluated at three points (apical, middle and coronal) to determine the greatest change. The data was statistically analyzed using the Student t-test by Statistical Analysis System (SAS) software. RESULTS: Statistical analysis revealed that in group B, dentine was equally removed within the canal coronal to the curvature, whereas in group A, the inner wall was predominantly removed (P<0.01). The two groups had no significant difference at the apical and middle points of the canal curvature. CONCLUSION: Our in vitro study revealed no significant difference between the single length method and crown-down technique using Mtwo for preparation of apical and middle portion of canal curvature.