Novel antimicrobial applications of copper oxide nanoparticles after combination with tissue conditioner used in complete prostheses.

BACKGROUND: Tissue conditioners are used for treating and improving the tissues supporting complete dentures. On the other hand, recent advances in nanotechnology have revolutionized various fields of science, including dentistry. The present study aimed to investigate novel antimicrobial applications of copper oxide nanoparticle-based tissue conditioner used in complete prostheses. METHODS: The present experimental study included 126 tissue conditioner samples with different concentrations of copper oxide nanoparticles (20%, 10%, 5%, 2.5%, 1.25%, 0.625%, and 0% w/w). The samples were incubated with Enterococcus faecalis, Pseudomonas aeruginosa, and Candida albicans in 24-well plates for 24 h. Then, samples from the wells were re-incubated for 24 h, and the microorganisms were counted. RESULTS: The culture media containing E. faecalis and P. aeruginosa showed significantly different growth between different nanoparticle concentrations following 24 h (P < 0.001), showing a reduction in bacterial growth with increased nanoparticle concentration. Both bacteria did not show any growth at the 20% concentration. However, C. albicans showed significant differences in growth between different nanoparticle concentrations following 48 h (P < 0.001), showing a reduction in growth with increased nanoparticle concentration. Also, the least growth was observed at the 20% concentration. CONCLUSIONS: In conclusion, the CuO nanoparticles were prepared using a green synthesis methon in the suitable sizes. Moreover, the tissue conditioners containing CuO nanoparticles showed acceptable antimicrobial properties against E. faecalis, P. aeruginosa, and C. albicans.

Effects of various disinfectants on surface roughness and color stability of thermoset and 3D-printed acrylic resin.

Denture cleansers are extensively utilized to inhibit the colonization of various Candida species. Currently, additive technology in denture fabrication has become more prevalent. This study aims to assess the impact of disinfectants on the surface roughness and color stability of distinct denture bases. Disc-shaped samples (N=66) were exposed to three different disinfectants: 0.5% sodium hypochlorite, 1% hydrogen peroxide, and 2% chlorhexidine. The samples underwent evaluation via spectrophotometry and profilometry, respectively. Data analysis was conducted utilizing analysis of variance (ANOVA) (p < 0.05). Within the heat-cured group, sodium hypochlorite resulted in the most notable change in surface roughness (0.2 µm), while chlorhexidine exhibited the least impact (0.001 µm), showing a significant difference (p <0.008). The color change (ΔE) for 3D-printed samples immersed in all disinfectants was higher compared to heat-cured samples. Among the heat-cured samples, chlorhexidine induced the highest ΔE (2.76), while sodium hypochlorite resulted in the lowest (ΔE = 1.44), and this difference was statistically significant (p <0.008). Chlorhexidine caused the most significant color alteration among the solutions, while sodium hypochlorite induced the most considerable changes in surface roughness.

The influence of foundation restoration type and ceramic thickness on the final color of zirconia-reinforced lithium silicate ceramic.

Background: Similarity in the appearance of a monolithic restoration with the adjacent teeth is necessary. This study aims to influence the foundation material type and ceramic thickness on the final color of zirconia-reinforced lithium silicate (ZLS) ceramic. Materials and Methods: In this experimental study, the A2 translucent blocks of ZLS were sectioned into rectangular specimens with thicknesses 1, 1.5, and 2 mm (n = 15). Substructure materials include resin composite (B1, D2, A2, A3, and C3), nickel chrome alloy, amalgam, and white and black substrate. Substructure material of resin composite with A2 color was proposed as the control group. The value of the color difference (ΔE00) is calculated by the CIEDE2000 formula. Data analysis was accomplished by two-factor repeated measures ANOVA and one-sample t-test (α =0.05). Results: The mean value of maximum ΔE00 with a black substrate (12.13 ± 0.17) at 1 mm ceramic thickness and the mean value of minimum ΔE00 with B1 resin composite foundation material (0.02 ± 0.17) at 2 mm ceramic thickness are visible. The significant effect of the foundation restoration type, thickness, and interaction between them is visible on ΔE00 (P < 0.001). Conclusion: Different thickness is required to meet ideal esthetic outcomes with different substrates. Under the conditions of this investigation, zirconia-reinforced lithium silicate over black, white, nickel-chromium, and amalgam did not meet acceptable outcomes.

The effect of adding silver nanoparticles on the color stability of feldspathic porcelains.

Background: This study aims to investigate the color stability of feldspathic porcelains with different concentrations of silver nanoparticles (AgNPs). Materials and Methods: In this experimental study, feldspathic porcelain disks with AgNPs of 0 parts per million (ppm), 250 ppm, and 500 ppm were used (sample size = 180). These ceramic discs were subjected to thermocycling in tea, orange juice, and artificial saliva. The optical parameters of disks were measured before and after being immersed in the solutions. Then, the color change (ΔE 00) of the samples was measured by using the CIEDE 2000 formula. The data were analyzed by one-way analysis of variance (ANOVA) and Tukey's post hoc test. The level of significance was determined to be 0.05. Results: The results of the ANOVA test show that there was a significant difference in ΔE 00 (P ≤ 0.05). The maximum ΔE 00 was visible in the samples with AgNPs 0 ppm that were exposed to orange juice, and the minimum ΔE 00 was related to the disks with AgNPs 500 ppm in artificial saliva. Conclusion: Based on the results of this study, adding AgNPs to feldspathic porcelain increases the color stability of the ceramic discs.

A comparative evaluation of wear resistance of three types of artificial acrylic teeth after removing the glaze layer.

Background: The posterior denture teeth wear faster than the anterior teeth, which can result in occlusal interferences, loss of vertical dimension of occlusion, greater stress accumulation in the anterior region, and higher ridge resorption. This study aimed to compare the wear resistance of three types of artificial acrylic teeth before and after removing the glaze layer. Materials and Methods: This in vitro study compared three types of artificial acrylic teeth, namely, Finex (F), SR Orthotyp DCL (S), and Vita Physiodents (V) in six groups (n = 10). Half of the artificial teeth of each brand underwent 0.5-mm buccal reduction to remove the glaze layer (groups FC, SC, and VC). The teeth were thermocycled and placed in a chewing simulator. The teeth with and without the glaze layer were weighed before and after the wear test. The data were analyzed using ANCOVA (the level of significance was 0.05). Results: The weight reduction (indicative of wear) was 0.03 ± 0.02 and 0.12 ± 0.03 mg in Groups S and SC, 0.03 ± 0.02 and 0.25 ± 0.04 mg in Groups V and VC, and 0.11 ± 0.15 and 0.28 ± 0.1 mg in groups F and FC, respectively. Removing the glaze layer (P < 0.01), type and brand of acrylic tooth (P < 0.01), and the baseline weight of artificial teeth (P < 0.01) had significant effects on wear resistance of artificial teeth. Conclusion: The wear of artificial teeth was greater after removing the glaze layer, and the magnitude of wear was also significantly different among the three brands. The group FC showed maximum wear while the groups S and V showed minimum wear.

Influence of Head Position on the CBCT Accuracy in Assessment of the Proximity of the Root Apices to the Inferior Alveolar Canal.

STATEMENT OF THE PROBLEM: The most important risk factor for inferior alveolar nerve (IAN) damage is the proximity of the mandibular root apices to the alveolar canal. Failure to position the patient's head at standardized orientation during cone beam computed tomography (CBCT) scans might adversely affect the relative position of the alveolar canal and mandibular root apices with subsequent treatment failure. PURPOSE: The purpose of the present study was to investigate the influence of the orientations of the skull during the scanning procedure on the accuracy of CBCT images in determining the positional relationship of the mandibular tooth apices to the alveolar canal. MATERIALS AND METHOD: CBCT scans of 7 human dry skulls were obtained by using NewTom VGi CBCT in standard, tilt, flexion, extension and rotation positions of the head. The shortest radiographic distance between the mandibular tooth apices and the IAN canal of 20 points were measured on cross sectional images of CBCT in all position scans. A sample t-test was used to compare the measurements at different head position with the standard position values. RESULTS: Significant differences were found in the measurements of normal and tilt orientations. However, there was no statistically significant difference between the measurements in standard position and other deviated positions. The mean errors in all head positions were less than 0.5mm. CONCLUSION: Alteration of patient head positioning during CBCT scanning does not affect the relative position of the IAN and the apices of posterior teeth.