Radiopacity evaluation of contemporary resin composites by digitization of images

The Impact of Simulated Bruxism Forces and Surface Aging Treatments on Two Dental Nano-Biocomposites-A Radiographic and Tomographic Analysis

Background and Objectives: Nowadays, indication of composite materials for various clinical situations has increased significantly. However, in the oral environment, these biomaterials are subjected (abnormal occlusal forces, external bleaching, consumption of carbonated beverages, etc.) to changes in their functional and mechanical behavior when indicated primarily for patients with masticatory habits. The study aimed to recreate in our lab one of the most common situations nowadays-in-office activity of a young patient suffering from specific parafunctional occlusal stress (bruxism) who consumes acidic beverages and is using at-home dental bleaching. Materials and Methods: Sixty standardized class II cavities were restored with two nanohybrid biocomposite materials (Filtek Z550, 3M ESPE, and Evetric, Ivoclar Vivadent); the restored teeth were immersed in sports drinks and carbonated beverages and exposed to an at-home teeth bleaching agent. The samples were subjected to parafunctional mechanical loads using a dual-axis chewing simulator. A grading evaluation system was conducted to assess the defects of the restorations using different examination devices: a CBCT, a high-resolution digital camera, and periapical X-rays. Results: Before mechanical loading, the CBCT analysis revealed substantially fewer interfacial defects between the two resin-based composites (p > 0.05), whereas, after bruxism forces simulation, significantly more defects were identified (p < 0.05). Qualitative examination of the restorations showed more occlusal defects for the Evetric than the other nanohybrid composite. Conclusions: There were different behaviors observed regarding the studied nanocomposites when simulation of parafunctional masticatory forces was associated with aging treatments.

Influence of Incorporating Zirconium- and Barium-based Radiopaque Filler Into Experimental and Commercial Infiltrants

OBJECTIVES

To evaluate how adding different concentrations of particles (barium or zirconium oxide 25%/45% by weight) to a commercial infiltrant (Icon) and an experimental infiltrant influences cohesive strength (CS), degree of conversion (DC), water sorption (WS), solubility (SL), radiopacity, and penetration depth.

METHODS AND MATERIALS

Microtensile CS (n=10) was evaluated using a universal testing machine. DC (n=5) was evaluated in a Fourier-transform infrared spectrometer. Polymerized samples were dissected, weighed, and stored to obtain the final mass for WS and SL tests (n=10). Radiopacity analysis (n=5) was performed using a digital radiography system. Penetration depth analysis (n=5) was performed by confocal laser scanning microscopy. Analyses were performed using the R program, with a significance level of 5%, except for the penetration depth analyses, which were evaluated only qualitatively.

RESULTS

The groups with 45% zirconium showed greater CS values, regardless of the infiltrant. Among the groups with no particle addition, those of the experimental infiltrant presented higher DC than those of Icon. The experimental infiltrant presented lower WS than Icon. All groups had SL below the ISO recommended levels. Radiopacity higher than 2.24 mmAl (enamel radiopacity) was observed only in the groups with 45% zirconium. All the groups achieved similar penetration depth, but the groups containing experimental infiltrant appear to have had longer tag extensions.

CONCLUSIONS

Addition of 45% of zirconium presented good results for CS and WS, as well as SL below the ISO recommended standard, adequate radiopacity, and penetration depth similar to the other groups.

Pediatric Dentists' Educational Experiences, Attitudes, and Professional Behavior Concerning Resin Infiltration: Implications for Dental Education

Minimally invasive dentistry (MID) is receiving increased attention. Resin infiltration (RI) is one micro-invasive technique for treating initial caries by sealing white spot lesions on tooth surfaces. The aims of this study were to assess pediatric dentists' RI-related educational experiences, attitudes, and professional behavior and to determine if their educational experiences were significantly related to their professional attitudes and behavior regarding RI. This cross-sectional study used an online survey to collect data from members of the American Academy of Pediatric Dentistry (AAPD) in March-April 2017. Of the 2,367 AAPD members invited to participate, 43 emails could not be delivered, and 273 surveys were completed, for a response rate of 11.8%. While only 9% of the 273 respondents reported that their classroom-based dental education had informed them about RI and only 1% that it had prepared them well to use RI with pediatric patients, higher percentages said they had been informed/prepared well by their classroom-based (24%) and clinical residency education (12%). The majority wanted to learn more about RI (71%) and would like to take a related CE course (59%). The respondents' average RI-related attitudes were positive (on five-point scale with 1=worst attitude: Mean=3.84). Regarding use of RI, 28% of respondents said they used RI sometimes and 4% often/very often, with 64% considering implementing RI in their clinics. Graduation year did not correlate with RI attitudes and use. However, the more education about RI the respondents had received during their residency (r=0.20; p<0.01) and in professional development after graduation (r=0.34; p<0.001), the more they used RI in their own work. This study found that the pediatric dentists' RI-related education was positively correlated with their professional behavior. Increasing predoctoral, resident, and continuing professional education about RI should therefore be considered.

Clinical relevance of antimicrobial testing results for dental restorative materials

BACKGROUND

The antimicrobial activity of restorative materials is clinically relevant because all dental materials are subject to an environment containing bacteria. This study aimed to investigate the use of 2 methodologies referred to in the literature to assess antimicrobial properties of restorative materials and investigate whether material properties alter results of these traditional methodologies.

METHODS

A number of dental restorative materials - namely, Chemfil Superior®, Spectrum®, Heliobond®, Ionoseal®, Dyract Extra®, Smart Dentin Replacement (SDR®) and Biodentine® - were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) analysis, Fourier transform infrared (FT-IR) spectroscopy and pH analysis. Antimicrobial activity was assessed using agar diffusion and biofilm accumulation tests. Key factors affecting results were assessed using analysis of covariance.

RESULTS

Biodentine after immediate mixing and Ionoseal aged for 6 weeks resulted in an inhibition zone, while significantly higher McFarland readings were observed in the presence of barium when using materials Ionoseal, Dyract and SDR at 24-hour aging. Through analysis of covariance it was shown that material properties affected methodology results.

CONCLUSIONS

Properties of materials affect results of antimicrobial testing, but this may not directly reflect the antimicrobial potential of the material in question. Careful choice of methodology and interpretation of results is important.

Biocompatibility and antibacterial activity of nitrogen-doped titanium dioxide nanoparticles for use in dental resin formulations

The addition of antibacterial functionality to dental resins presents an opportunity to extend their useful lifetime by reducing secondary caries caused by bacterial recolonization. In this study, the potential efficacy of nitrogen-doped titanium dioxide nanoparticles for this purpose was determined. Nitrogen doping was carried out to extend the ultraviolet absorbance into longer wavelength blue light for increased biocompatibility. Titanium dioxide nanoparticles (approximately 20-30 nm) were synthesized with and without nitrogen doping using a sol-gel method. Ultraviolet-Visible spectroscopy indicated a band of trap states, with increasing blue light absorbance as the concentration of the nitrogen dopant increased. Electron paramagnetic resonance measurements indicated the formation of superoxide and hydroxyl radicals upon particle exposure to visible light and oxygen. The particles were significantly toxic to Escherichia coli in a dose-dependent manner after a 1-hour exposure to a blue light source (480 nm). Intracellular reactive oxygen species assay demonstrated that the particles caused a stress response in human gingival epithelial cells when exposed to 1 hour of blue light, though this did not result in detectable release of cytokines. No decrease in cell viability was observed by water-soluble tetrazolium dye assay. The results show that nitrogen-doped titanium dioxide nanoparticles have antibacterial activity when exposed to blue light, and are biocompatible at these concentrations.