Comparative evaluation of fiber-reinforced, bulk-fill and conventional dental composites: Physical characteristics and polymerization properties.

BACKGROUND: Resin composites have various applications. At the same time, they have some drawbacks, such as polymerization shrinkage. Conventional composites are polymerized in 2-mm thick layers. However, in posterior restoration, the 2-mm depth of cure is not satisfactory. To find a solution, resin composites have been vastly improved in terms of fillers, matrix and initiators. OBJECTIVES: To evaluate polymerization properties and physical characteristics of fiber-reinforced composites and compare them with bulk-fill composites that are designed for large posterior restorations. MATERIAL AND METHODS: Samples were prepared from each resin composite. The 3-point bending test was performed to evaluate the flexural strength of all composites. The depth of cure of the composite from 1 mm to 4 mm of depth was analyzed using Vickers hardness test (VHN). To analyze the degree of conversion, Fourier-transform infrared spectroscopy (FTIR) of the top and bottom surfaces of the samples with 4-mm thickness was calculated. The data were analyzed using one-way analysis of variance (ANOVA) test followed by post hoc test (95% confidence interval (95% CI)). RESULTS: The Filtek showed the highest flexural strength followed by everX and X-tra fil. At 1-mm depth, X-tra fil had the highest and Gradia had the lowest microhardness. At the 4-mm depth, the microhardness trend was as follows: everX > Filtek > X-tra fil > Gradia > Beautifil. The everX composite had the lowest reduction of the degree of conversion at 4-mm thickness, which showed a significant difference in comparison with Filtek, Gradia and X-tra fil composites. CONCLUSIONS: Based on the results of our study, it can be concluded that the fiber-reinforced composite everX showed more favorable results regarding polymerization properties, such as the degree of conversion and the depth of cure. However, the flexural strength results in Filtek were better than those in everX.

A modified TEGDMA-based resin infiltrant using polyurethane acrylate oligomer and remineralising nano-fillers with improved physical properties and remineralisation potential.

OBJECTIVES: This study aimed to modify an experimental triethylene glycol dimethacrylate (TEGDMA) based resin infiltrant using PUA oligomer and two remineralising fillers, including fluorohydroxyapatite (FHA) and fluoride-doped bioactive glass (FD-BG), to improve the mechanical and physical properties and induce remineralising potential. MATERIALS AND METHODS: The polyurethane acrylate oligomer (PUA) was synthesised and characterised. Experimental resin infiltrant was prepared by mixing 10% of synthesised PUA with 88% TEGDMA. Water contact angle, penetration coefficient, and penetration depth were then measured. The FHA and FD-BG fillers were synthesised and characterised. To prepare nano-filled resin infiltrant, 5% of each powder was mixed with the prepared resin infiltrant. The prepared resin infiltrants were characterised to evaluate their degree of conversion, mechanical properties, water sorption, and solubility. The ion release of filled resin was also assessed. The non-infiltrated and infiltrated enamel specimens underwent fourteen days of pH-cycling, and a surface microhardness was done to assess the resistance to demineralisation. RESULTS: The results showed that the addition of PUA to TEGDMA increased the mechanical properties and decreased water sorption and solubility. The addition of synthesised FD-BG fillers to resin infiltrant significantly improved the resistance to demineralisation of enamel samples compared with other groups (p ≤ 0.001). The FHA fillers also improved the resistance to demineralisation; however, the produced changes were not statistically meaningful (p > 0.05). CONCLUSIONS: Based on the results, the PUA+TEGDMA+ FD-BG/FHA composite can be used as an alternative material for pure TEGDMA in enamel infiltration approaches owing to its better mechanical properties, lower water sorption and solubility, and also remineralisation potential. CLINICAL SIGNIFICANCE: A resin infiltrant with remineralisation potential, lower water sorption and solubility and higher mechanical properties may enhance the management of early caries lesions.

Personality Characteristics and Oral Health-Related Quality of Life in an Iranian Adult Population.

Self-rated oral health and oral health-related quality of life is known to be influenced by various personality characteristics. The aim of this study was to understand how personality characteristics affect oral health-related quality of life ratings in an Iranian adult population. The study included 443 adult participants recruited from a public dental clinic in Kerman, southeast of Iran. The Oral Health Impact Profile-14 questionnaire was used to assess oral health-related quality of life. Personality traits were determined using the 20-item Positive Affectivity Negative Affectivity Scale. Locker's single-item global self-rating of oral health was used to obtain information on self-rated oral health. Pearson correlation and negative binomial regression were used for data analysis. A higher negative affectivity score was associated with worse oral heath related quality of life, and a higher positive affectivity score was associated with better rating of oral health-related quality of life. On average, individuals who described their oral health as worse scored higher on Oral Health Impact Profile-14. Negative affectivity and positive affectivity influence individuals' perceptions of their oral health and quality of life. If possible, investigations of oral health-related quality of life measures should also include a brief personality assessment.

Effect of Volume and Renewal of the Storage Media on the Release of Monomer from Dental Composites.

This study evaluated the effect of the volume and renewing of storage media on monomer leachability from dental composite. Samples of two dental composites (BEAUTIFIL II Gingiva (BG) and Filtek Bulk-Fill Flowable (FBF)) were stored after polymerization in 1 and 3 milt storage media (ethanol/water 75%) for seven days. Refreshing of storage media was done in half of the samples of each group. The amounts of releasing monomers (UDMA, BisGMA, TEGDMA) in storage media were measured by high-performance liquid chromatography (HPLC). Data was analyzed using two-way ANOVA and t-test (α = 0.05). Elution of TEGDMA and UDMA from both composites was significantly higher in 3 mL storage media. In groups with refreshing of storage media, BisGMA had higher amounts of release. Saturation makes the storage media volume important factor in monomer elution. Refreshing of storage media had significant effect on monomer release before the elution of 50% of total released monomer.

Comparative assessment of the crystalline structures of powder and bulk human dental enamel by X-ray diffraction analysis.

OBJECTIVES: The aim of this study was to assess and compare the crystalline structures of both powder and bulk human dental enamel by X-ray diffraction analysis (XRD). METHODS: The buccal surfaces of 60 selected noncarious third molars were divided into two groups of powdered and bulk enamel specimens. To prepare enamel powders, the enamel tissues were ground and powdered manually using a mortar and pestle. For bulk samples, the enamel slabs were sectioned using a low-speed diamond saw. The crystalline structures of samples were analyzed by XRD, and the obtained data were analyzed. The values of the lattice parameters were obtained using the equation of hexagonal crystalline structures. The crystal sizes and microstrains of crystallites were calculated using both the Scherrer and Williamson-Hall (W-H) methods. The total area under the peaks was considered as the criterion for assessing crystallinity. The data were analyzed by a parametric independent t-test and nonparametric Mann-Whitney test using SPSS for Windows at a significance level of 0.05. RESULTS: The results of the current study revealed significant differences between the crystallinity values and crystal sizes of the two study groups (p ≤ 0.001). The powdered samples showed higher crystallinity and smaller crystal sizes than those of the bulk samples. The obtained strain values of the powder samples were nearly twice those of the bulk samples. This difference was not statistically significant (p = 0.76). CONCLUSIONS: The results of this study revealed that the sample preparation method for human tooth enamel can affect the crystalline data obtained from XRD analysis.