Effect of curcumin-containing nanofibrous gelatin-hydroxyapatite scaffold on proliferation and early osteogenic differentiation of dental pulp stem cells.

BACKGROUND: In recent years, the electrospinning method has received attention because of its usage in producing a mimetic nanocomposite scaffold for tissue regeneration. Hydroxyapatite and gelatin are suitable materials for producing scaffolds, and curcumin has the osteogenesis induction effect. AIMS: This study aimed to evaluate the toxicity and early osteogenic differentiation stimulation of nanofibrous gelatin-hydroxyapatite scaffold containing curcumin on dental pulp stem cells (DPSCs). OBJECTIVE: The objective of the present investigation was the evaluation of the proliferative effect and primary osteogenic stimulation of DPSCs with a nanofibrous gelatin-hydroxyapatite scaffold containing curcumin. Hydroxyapatite and gelatin were used as suitable and biocompatible materials to make a scaffold suitable for stimulating osteogenesis. Curcumin was added to the scaffold as an osteogenic differentiation-enhancing agent. METHODS: The effect of nano-scaffold on the proliferation of DPSCs was evaluated. The activity of alkaline phosphatase (ALP) as the early osteogenic marker was considered to assess primary osteogenesis stimulation in DPSCs. RESULTS: The nanofibrous gelatin-hydroxyapatite scaffold containing curcumin significantly increased the proliferation and the ALP activity of DPSCs (P<0.05). The proliferative effect was insignificant in the first 2 days, but the scaffold increased cell proliferation by more than 40% in the fourth and sixth days. The prepared scaffold increased the activity of the ALP of DPSCs by 60% compared with the control after 14 days (P<0.05). CONCLUSION: The produced nanofibrous gelatin-hydroxyapatite scaffold containing curcumin can be utilized as a potential candidate in tissue engineering and regeneration of bone and tooth. FUTURE PROSPECTS: The prepared scaffold in the present study could be a beneficial biomaterial for tissue engineering and the regeneration of bone and tooth soon.

Extracorporeal Shock Wave Therapy as a Helpful Method for Rapid Osseointegration of Dental Implants: Animal Study.

The aim of this study was to assess the multi-phasic use of extracorporeal shock wave therapy (ESWT) as an adjuvant treatment to accelerate the osseointegration of titanium dental implants. Initially, twelve titanium mini-screws were inserted in femur bones of six New Zealand rabbits in three groups; the one-time treated group, the three-time treated group, and the control group (without ESWT). Then, 1800 focused shockwaves with an energy flux density of 0.3 mJ/mm2 in every phase were used. Fourteen days after the last phase of ESWT, the animals were sacrificed to assess the osseointegration of screws via micro-computed tomography scan (micro-CT scan), biomechanical pull-out test, and histopathological analysis. Pull-out and histopathology analysis showed that the ESWT significantly increased bone regeneration and osseointegration around the implants compared to the control group (p < 0.05). Moreover, the pull-out test confirmed that the three-time treated screws needed more force to pull the bone out compared to the other two groups (p < 0.05). The mean bone volume fraction between the control group, the one-time treated group, and the three-time treatment group were not statistically significant (p > 0.05) according to the micro-CT scan results. Based on our results, ESWT can be suggested as a non-invasive and cost-effective adjuvant for osseointegration of dental implants. However, more in vivo studies and clinical trials are needed for validation of this finding.

Effect of Adding Silica Nanoparticles on the Physicochemical Properties, Antimicrobial Action, and the Hardness of Dental Stone Type 4.

This study was conducted to investigate the effect of adding silica nanoparticles on the physicochemical properties, antimicrobial action, and the hardness of dental stone type 4. Dental stone type 4 powder was physically mixed with nanoparticle powder at weight percentages (0, 0.5, 1, and 2 percent). The required amount of powder was added to water according to the manufacturer's instructions. The prepared set materials were subjected to the physicochemical studies; Fourier transmission infrared spectroscopy (FTIR) was taken up to investigate the functional groups and X-ray diffraction (XRD) was used to evaluate the crystallinity. Also, scanning electron microscopy (SEM) was used to examine the morphology of the prepared samples. Agar diffusion test was carried out for the prepared samples against the Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) to test the average growth inhibition zones. Finally, the Vickers surface hardness test was performed for each group using a hardness tester. The adding silica nanoparticles to dental stone type 4 increased the diameter of inhibition zones for the groups in both bacteria significantly (p < 0.05). The results showed that adding silica nanoparticles to dental stone type 4 increased the diameter of inhibition zones for the groups in both bacteria significantly (p < 0.0001). There was a significant difference between all groups and the 0% group in both bacteria (p < 0.0001). Besides, the adding of silica nanoparticles to dental stone type 4 increased the surface hardness significantly (p = 0.0057) without any effect on physicochemical properties. The 0% and the 0.5% groups had significant differences with the 2% group (p = 0.0046 and p = 0.0205 respectively). Then, at least 2% silica nanoparticles are needed for a significant increase. Clinical trials are needed to enlarge for dental stone type 4 containing silica nanoparticles in the future.

Antibacterial agent-releasing scaffolds in dental tissue engineering.

It seems quite challenging in tissue engineering to synthesize a base material with a range of essential activities, including biocompatibility, nontoxicity, and antimicrobial activities. Various types of materials are synthesized to solve the problem. This study aimed to provide the latest relevant information for practitioners about antibacterial scaffolds in dental tissue engineering. The PubMed search engine was used to review the relevant studies with a combination of the following terms as search queries: tissue engineering, scaffolds, antimicrobial, dentistry, dental stem cells, and oral diseases. It is noteworthy to state that only the terms related to tissue engineering in dentistry were considered. The antimicrobial scaffolds support the local tissue regeneration and prevent adverse inflammatory reactions; however, not all scaffolds have such positive characteristics. To resolve this potential defect, different antimicrobial agents are used during the synthesis process. Innovative methods in guided tissue engineering are actively working towards new ways to control oral and periodontal diseases.

Preparation, Physicochemical Assessment and the Antimicrobial Action of Hydroxyapatite-Gelatin/Curcumin Nanofibrous Composites as a Dental Biomaterial.

In this study, we prepared and evaluated hydroxyapatite-gelatin/curcumin nanofibrous composites and determined their antimicrobial effects against Escherichia coli, Staphylococcus aureus, and Streptococcus mutans. Hydroxyapatite-gelatin/curcumin nanofibrous composites were prepared by the electrospinning method. The prepared nanocomposites were then subjected to physicochemical studies by the light scattering method for their particle size, Fourier transmission infrared spectroscopy (FTIR) to identify their functional groups, X-ray diffraction (XRD) to study their crystallinity, and scanning electron microscopy (SEM) to study their morphology. For the microbial evaluation of nanocomposites, the disk diffusion method was used against Streptococcus mutans, Staphylococcus aureus, and Escherichia coli. The results showed that the nanofibers were uniform in shape without any bead (structural defects). The release pattern of curcumin from the nanocomposite was a two-stage release, 60% of which was released in the first two days and the rest being slowly released until the 14th day. The results of the microbial evaluations showed that the nanocomposites had significant antimicrobial effects against all bacteria (p = 0.0086). It seems that these nanocomposites can be used in dental tissue engineering or as other dental materials. Also, according to the appropriate microbial results, these plant antimicrobials can be used instead of chemical antimicrobials, or along with them, to reduce bacterial resistance.

Effects of Orthodontic Adhesives on Dental Enamel Color Alteration Using Chemically Cured and Light-Cured Composites.

OBJECTIVES: The purpose of this investigation was to evaluate the color alteration of dental enamel following the use of light-cured and chemically cured composites for bonding of metal brackets. MATERIALS AND METHODS: Sixty extracted human premolars divided into five groups (n=12) were included in this study. Metal brackets were bonded using chemically cured (System 1+ and Unite) and light-cured (Transbond XT and Grengloo) composites. The control group remained untreated. After 72 hours of immersion in a staining solution and 24 hours of photoaging, the brackets were debonded, and adhesive remnants were cleaned using a 12-blade tungsten carbide bur and polished with Sof-Lex discs. The color was assessed at the baseline and after cleaning procedures in accordance with the CIE L*a*b (lightness, red/green, blue/yellow) color system. Statistical analyses were performed using paired sample t-test and one-way analysis of variance (ANOVA). RESULTS: The L*, a*, and b* parameters showed a significant increase in all adhesive groups (P<0.001). The experimental groups showed significant color changes (P<0.05), and the mean ΔE ranged from 2.46 to 3.15 units. No significant difference was found between the ΔE of the adhesive groups (P>0.05). CONCLUSION: The enamel color change is influenced by bonding and debonding procedures. Chemically cured and light-cured composites have similar effects on dental enamel color alterations.

Effect of the of Zeolite Containing Silver-Zinc Nanoparticles on the Push out Bond Strength of Mineral Trioxide Aggregate in Simulated Furcation Perforation.

STATEMENT OF THE PROBLEM: Recently, zeolite has been regarded to improve the properties of dental materials such as mineral trioxide aggregate (MTA). PURPOSE: The aim of the present study was to evaluate the effect of incorporating zeolite/silver/zinc (Ze/Ag/Zn) composite at 2 wt% to MTA powder on the push-out bond strength in simulated furcation perforations. MATERIALS AND METHOD: Furcal perforations, measuring 1.3 mm in diameter and 2 mm in height, were simulated in 40 human mandibular first molars. The samples were allocated to two groups (n=20) based on the material used for the repair of perforations. In the group 1, MTA and in the group 2, MTA plus Ze/Ag/Zn (2%) was used. The samples were incubated at 37°C for 1 week. Then the universal testing machine was employed to measure bond strength. The resistance of materials to dislodgment was recorded in MPa. Data were analyzed using t-test. Statistical significance was set at p< 0.05. RESULTS: The push-out bond strength in the group 1 (6.40±1.98 MPa) was significantly higher than that in the group 2 (2.1±0.6 MPa) with p= 0.001. CONCLUSION: Under the limitations of the present study, it can be concluded that incorporation of Ze/Ag/Zn at 2 wt% to MTA powder had a negative effect on the push-out bond strength.

The effect of photodynamic therapy and polymer solution containing nano-particles of Ag /ZnO on push-out bond strength of the sealers AH-Plus and MTA Fillapex.

BACKGROUND: The aim of this in vitrostudy was to examine and compare the effect of photodynamic therapy and solution containing nano particles Ag/ZnO on adhesion of endodontic sealers to dentinal walls of human root canal. MATERIAL AND METHODS: Ninty single-rooted human teeth were selected and their clinical crown was cut from the cemento-enamel junction zone. Canals were prepared by RaCe rotary system and the smear layer was removed using 17% EDTA and 5.25% NaOCl. Samples were randomly divided into two groups of AH Plus and MTA Fillapex based on the sealer type and each group based on antimicrobial method was divided into two sub-groups of photodynamic therapy and polymer containing nano particles of Ag / ZnO and a control sub-group (N = 15). After obturation of canals with gutta-percha and sealers mentioned, the samples were incubated for a week at a humidity of 95% and 37°C and then 2mm thick discs were prepared from the middle region of roots for Push-out test. The maximum failure force was recorded in newton and converted to MPa. Then, 3 random specimens of each subgroup were evaluated by scanning electron microscopy. Statistical analysis was performed by Two way ANOVA and (P<0.05) was considered significant. RESULTS: The highest (4.84 ± 1.63) and lowest (0.16 ± 0.075) push-out bond strength values were obtained in (AH Plus-PDT) and (MTA Fillapex-Ag/ZnO) respectively. Independent of antimicrobial method, AH Plus bond strength was significantly higher than the MTA Fillapex (p<0.001). For both sealers, PDT increased the bond strength significantly (p<0.001). CONCLUSIONS: Photodynamic therapy has a positive effect on the bond strength of AH Plus and MTA Fillapex sealers. Key words:AH Plus, MTA Fillapex, Nano particles, Photodynamic therapy, Push-out.

Effect of preheat repetition on color stability of methacrylate- and silorane-based composite resins.

Background. The aim of this study was to investigate the effect of preheating methacrylate- and silorane-based composite resins on their color stability up to 40 times at 55‒60°C. Methods. Seventy-six methacrylate and silorane-based composite resin samples, with a diameter of 10 mm and a height of 2 mm, were divided into 4 groups (n=19). After the samples were prepared, their color parameters were determined using a reflective spectrophotometer. The composite resin samples were separately stored in a solution of tea for 40 consecutive days. Then the samples underwent a color determination procedure again using a spectrophotometer and color changes were recorded. Finally two-way ANOVA was used to study the effect of composite temperature on its staining (P<0.05). Independent-samples t-test was used to evaluate changes in conversion rates of preheated composite resin samples compared to non-heated samples at P=0.005 and P=0.029 for silorane-based and Z250 composite resin samples, respectively. Results. Both composite resin type (P=0.014) and preheating (P<0.001) had significant effects on ΔE. Conclusion. Repeated preheating of methacrylate- and silorane-based composite resin samples, up to 55‒60°C for 40 rounds, resulted in more color changes compared with unheated composite resin samples. After storage in a solution of tea the color change rate in the composite resin samples of silorane-based was higher than the Z250 composite resin samples.

Compressive Strength of Mineral Trioxide Aggregate with Propylene Glycol.

INTRODUCTION: The aim of this study was to evaluate the effect of adding propylene glycol (PG) to mineral trioxide aggregate (MTA) liquid with volume ratio of 20% on the compressive strength (CS) of MTA in two time periods (4 and 21 days) after mixing. METHODS AND MATERIALS: Four groups of steel cylinders (n=15) with an internal diameter of 3 and a height of 6 mm were prepared and MTA (groups 1 and 2) and MTA+PG (80% MTA liquid+20% PG) (groups 3 and 4) were placed in to the cylinders. In groups 1 and 3 the CS was evaluated after 4 days and in groups 2 and 4 after 21 days. Data were calculated using the two-ways ANOVA. The level of significance was set at 0.05. RESULTS: The highest (52.22±18.92 MPa) and lowest (4.5±0.67 MPa) of CS was obtained in 21-day MTA samples and 4-day MTA+PG specimen, respectively. The effect of time and PG were significant on the CS (P<0.05). Mixing MTA with PG significantly reduced the CS; but passing the time from 4 to 21 days significantly increased the CS. CONCLUSION: Considering the limitations of this study, PG had a negative effect on CS of MTA.

FT-Raman spectroscopic characterization of enamel surfaces irradiated with Nd:YAG and Er:YAG lasers.

Background. Despite recent advances in dental caries prevention, caries is common and remains a serious health problem. Laser irradiation is one of the most common methods in preventive measures in recent years. Raman spectroscopy technique is utilized to study the microcrystalline structure of dental enamel. In this study, FT-Raman spectroscopy was used to evaluate chemical changes in enamel structure irradiated with Nd:YAG and Er:YAG lasers. Methods. We used 15 freshly-extracted, non-carious, human molars that were treated as follows: No treatment was carried out in group A (control group); Group B was irradiated with Er:YAG laser for 10 seconds under air and water spray; and Group C was irradiated with Nd:YAG laser for 10 seconds under air and water spray. After treatment, the samples were analyzed by FT-Raman spectroscopy. Results. The carbonate content evaluation with regard to the integrated area under the curve (1065/960 cm-1) exhibited a significant reduction in its ratio in groups B and C. The organic content (2935/960 cm-1) area exhibited a significant decrease after laser irradiation in group B and C. Conclusion. The results showed that the mineral and organic matrices of enamel structure were affected by laser irradiation; therefore, it might be a suitable method for caries prevention.

Evaluation of Polymerization Efficacy in Composite Resins via FT-IR Spectroscopy and Vickers Microhardness Test.

Background and aims. Polymerization efficacy affects the properties and performance of composite resin restorations.The purpose of this study was to evaluate the effectiveness of polymerization of two micro-hybrid, two nano-hybrid and one nano-filled ormocer-based composite resins, cured by two different light-curing systems, using Fourier transformation infrared (FT-IR) spectroscopy and Vickers microhardness testing at two different depths (top surface, 2 mm). Materials and methods. For FT-IR spectrometry, five cylindrical specimens (5mm in diameter × 2 mm in length) were prepared from each composite resin using Teflon molds and polymerized for 20 seconds. Then, 70-µm wafers were sectioned at the top surface and at2mm from the top surface. The degree of conversion for each sample was calculated using FT-IR spectroscopy. For Vickers micro-hardness testing, three cylindrical specimens were prepared from each composite resin and polymerized for 20 seconds. The Vickers microhardness test (Shimadzu, Type M, Japan) was performed at the top and bottom (depth=2 mm) surfaces of each specimen. Three-way ANOVA with independent variables and Tukey tests were performed at 95% significance level. Results. No significant differences were detected in degree of conversion and microhardness between LED and QTH light-curing units except for the ormocer-based specimen, CeramX, which exhibited significantly higher DC by LED. All the composite resins showed a significantly higher degree of conversion at the surface. Microhardness was not significantly affected by depth, except for Herculite XRV Ultra and CeramX, which showed higher values at the surface. Conclusion. Composite resins containing nano-particles generally exhibited more variations in degree of conversion and microhardness.

Evaluating the In-vitro Antibacterial Effect of Iranian Propolis on Oral Microorganisms.

Propolis has traditionally been used in curing infections and healing wounds and burns. Current researches have shown that propolis has antibacterial, antifungal and antiviral actions however, the pharmacological activity of propolis is highly variable depending on its geographic origin. There have been few studies on the effects of Iranian propolis on the oral microorganisms. In this in-vitro study, the antimicrobial activity of the ethanolic and water extracts of the Iranian propolis (10%, w/v) from north-east area of Tehran was evaluated. Susceptibility of the oral strains tested (Streptococcus mutans ATCC 35668; Streptococcus salivarius ATCC 9222; Staphylococcus aureus ATCC 25923; Enterococcus faecalis ATCC 9854 and Lactobacillus casei ATCC 39392) was evaluated using the agar diffusion method at a concentration of 20 mg/mL of propolis and the zones of growth inhibition were measured. Antibacterial activity was determined by using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) at different concentrations of propolis. The ethanolic extract showed bacteriostatic and bactericidal activity against all the strains, with MIC and MBC ranges of 250-500 µg/mL. The MIC concentration of the water extract was 500 µg/mL against S. mutans and E. faecalis. The water extract showed bactericidal activity only against S. mutans (20 mg/mL). These results indicate that the ethanolic extract is probably more useful in the control of oral biofilms and subsequent dental caries development. However, to determine the consequence of the ethanolic extract of Iranian propolis on the oral mucosa, in-vivo studies of its possible effects are needed.