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Objectives: This study aimed to evaluate the color stability and translucency of various types of monolithic zirconia after immersion in chlorhexidine and Listerine mouthwashes. Materials and methods: This experimental study was performed on 36 disk-shaped specimens fabricated from low-translucent, high-translucent, and multilayered monolithic zirconia (n = 12 per group). Each group was equally divided and immersed in either 2% chlorhexidine (CHX) or Listerine mouthwash for 2 min daily over 7 days. Changes in color (ΔE) and the translucency parameter (ΔTP) were evaluated and compared. The data were analyzed with one-way ANOVA followed by Tukey's post-hoc tests (α = 0.05). Results: Chlorhexidine caused a significantly lower ΔE and a significantly higher ΔTP in multilayered zirconia compared to the low-translucency (ΔE: P = 0.0027, ΔTP: P<0.001) and the high-translucency zirconia group (ΔE: P<0.001, ΔTP: P = 0.022). Listerine caused a significantly higher ΔE in the high-translucency zirconia group compared to the multilayered zirconia group (P = 0.0165). It also resulted in a significantly higher mean ΔTP in the multilayered zirconia group compared to the low-translucency (P = 0.0003) and high-translucency zirconia groups (P = 0.019). Conclusions: In both mouthwashes, multilayered monolithic zirconia exhibited the highest color stability among the tested materials; albeit with the most pronounced changes in translucency. Meanwhile, high-translucency monolithic zirconia was more prone to discoloration when exposed to both mouthwashes. [ABSTRACT FROM AUTHOR]

The incidence rate of melanoma is dramatically increasing worldwide, raising it to the fifth most common cancer in men and the sixth in women currently. Resistance generally occurs to the agents used in chemotherapy; besides their high toxicity destroys the normal cells. This study reviewed a detailed summary of the structure, advantages, and disadvantages of nanotechnologybased drug delivery systems in the treatment of melanoma, as well as some nanocarrier applications in animal models or clinical studies. Respective databases were searched for the target keywords and 93 articles were reviewed and discussed. A close study of the liposomes, niosomes, transferosomes, ethosomes, transethosomes, cubosomes, dendrimers, cyclodextrins, solid lipid nanoparticles, and carbon nanotubes (CNTs) was conducted. It was found that these nanocarriers could inhibit metastasis and migration of melanoma cells and decrease cell viability. Conclusively, some nanocarriers like liposomes, niosomes, and transferosomes have been discussed as superior to conventional therapies for melanoma treatment. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effect of a surface sealant agent on the color stability and surface roughness (Ra) of two denture base materials: polymethyl methacrylate (PMMA) and nylon. Materials and Methods: A total of 96 disk-shaped specimens (10 x 2 mm) were fabricated from heat-cured PMMA and nylon denture base materials (n = 48/material). Each of the color stability and Ra tests were performed on half of the samples in each material group (n = 24), and these subgroups were then subdivided according to the surface treatment applied: 12 specimens were conventionally polished, serving as the control group, and 12 specimens received a sealant on the surface in addition to the surface polishing. Color stability was assessed through measuring the CIEL*a*b* color parameters before and after immersion in coffee solution. Ra was measured and scanning electron microscopy (SEM) photomicrographs were taken before and after thermocycling. Statistical analysis was done using 2-way analysis of variance (α = .05). Results: The surface sealant agent significantly increased the color stability of both materials (P = .047). However, it had no significant effect on the Ra of materials before (P = .600) or after (P = .583) thermocycling. Nylon had a significantly rougher surface than PMMA both before and after thermocycling (P < .001). Similarly, SEM observations show a more irregular texture for nylon than for PMMA. Conclusion: Although the sealant agent had no significant effect on the Ra before or after thermocycling, it significantly decreased the color change of nylon and PMMA disks. Based on both statistical analyses and SEM observations, the Ra of PMMA was lower than nylon denture base material. [ABSTRACT FROM AUTHOR]

Statement of the Problem: Increasing the sintering temperature is suggested by some manufacturers as a way to enhance the translucency of monolithic zirconia crowns. Meanwhile, its effect on the marginal fit and compressive strength of the restoration is not fully understood. Purpose: This study aimed to evaluate the effect of sintering temperature on the marginal fit and compressive strength of monolithic zirconia crowns. Materials and Method: In this in vitro study, thirty crowns of pre-sintered monolithic zirconia were milled and sintered in a special furnace at either 1450°C or 1550°C (n=15 per group). The marginal gaps were measured at 18 spots on the dies with a digital microscope. To evaluate the compressive strength, the specimens were cemented on brass dies by using conventional glass ionomer cement. Vertical load was applied by a universal testing machine until fracture. One-way ANOVA test was used to analyze the results (α=0.05). Results: The marginal gap was not significantly different between the two groups (p= 0.062). A significantly higher mean value of compressive strength was observed in crowns sintered at 1550°c (1988.27±635.09 N) than those sintered at 1450 °c (1514.27±455.11 N) (p= 0.026). Conclusion: Although increasing the sintering temperature would not affect the marginal gap of monolithic zirconia crowns, it could significantly improve the compressive strength of zirconia restorations. [ABSTRACT FROM AUTHOR]

Statement of the Problem: Monolithic zirconia restoration has been introduced to overcome the porcelain chipping. Different factors can affect the color of monolithic zirconia, so achieving the desired color in the restorations is considered as a challenge. Purpose: The purpose of this in vitro study was to determine the effect of different foundation materials on the color of monolithic zirconia at different thicknesses. Materials and Method: In this experimental study, thirty ceramic disks in three thicknesses (i.e. 0.6mm, 1.1mm and 1.5mm) were fabricated from high translucency shade A2 monolithic zirconia block. Disk shaped foundation materials were fabricated from nickel chromium alloy (Ni-Cr), non-precious gold alloy (NPG), zirconia, and shade A2 composite resin. The color was measured by a spectrophotometer. The color differences (ΔE) in the control and the test groups were calculated. The data were analyzed using two way ANOVA and compared with the post-hoc Tukey test (a=0.05). Results: ceramic thickness and foundation materials had a significant effect on the mean values of ΔE of monolithic zirconia ceramics (p= 0.001). The highest amount of ΔE value was observed in NPG, while Ni-Cr resulted in the lowest ΔE. Unacceptable results (ΔE>2.25) were observed for monolithic zirconia ceramics on NPG foundation material with a thicknesses of 0.6 and 1.1mm. The mean L* values of all foundation materials were higher than those of the control group except for Ni-Cr. The highest a* was seen in NPG and the mean b* values of all tested foundation materials were higher than those of the control group except for Ni-Cr. Conclusion: Increasing the thickness of monolithic zirconia decreased the color mismatch. High translucent monolithic zirconia could mask the color of Ni-Cr and zirconia in all three thicknesses (ΔE˂2.25), while it could not mask the color of NPG under thickness of 1.5mm. [ABSTRACT FROM AUTHOR]

Background: The flexural strength (FS) of a denture base material is of great concern, and many approaches have been used to strengthen the denture acrylic resins. The present study aimed to evaluate the effect of high-performance polymer (BioHPP) and metal mesh reinforcement on the FS of a heat-cured poly methyl methacrylate (PMMA) acrylic resin. Materials and Methods: This experimental study was done on 30 rectangular specimens (64 mm x 13 mm x 3 mm) of a heat-cured PMMA resin. The specimens were divided into three groups (n = 10) to be reinforced with either metal mesh or BioHPP mesh; one group was left nonreinforced, serving as the control group. The FS of specimens was assessed through a 3-point bending test by using a universal testing machine at a crosshead speed of 2 mm/min. Kruskal--Wallis H and Dunn's post hoc tests were used to compare the FS among the groups (alpha = 0.05). Results: The FS in the metal-reinforced group was statistically significantly higher than the two other groups (P < 0.001). However, the FS of the BioHPP-reinforced samples was not statistically significantly higher than the nonreinforced ones (P = 0.614). Conclusion: Reinforcing the PMMA with metal mesh significantly enhances its FS while BioHPP has no significant effect on the PMMA FS. [ABSTRACT FROM AUTHOR]

Statement of the Problem: Retrieval of cement-retained implant-supported restorations is challenging in cases of screw loosening or periodontal problems. Purpose: The purpose of this study was to evaluate the effect of the screw access hole on the fracture resistance of zirconia-based cement-retained restorations with and without an access opening. Materials and Method: In this in vitro study thirty-three cement-retained implantsupported zirconia-based molar crowns were fabricated and divided into 3 groups (n=11). As the control group, group 1 consisted of conventional cement-retained crowns. Group 2 comprised conventional cement-retained crowns in which a hole was created in the location of the screw. Group 3 consisted of cement-retained crowns in which a ledge was created in the location of the screw access channel. The specimens were cemented to their abutments and their access openings were filled with composite resin. A compressive load was applied to the specimens using a universal testing machine until they fractured. The mean fracture resistance values of the samples were compared by using the one-way ANOVA and Tamhane post-hoc test (a=0.05). Results: The mean fracture resistance values were 1270.18± 12.67 N in group 1 (the control group), 960.09±210.67 N in group 2 (conventional), and 1357.81±361.68 N in group 3 (the special design). The fracture resistance value was higher in the special design group than that of the conventional design (p= 0.018) and the fracture resistance value of the conventional design group was less than that of the control group (p= 0.042). No statistically significant difference was detected between the control group and the special design group in fracture resistance values. Conclusion: Preparing a screw access hole in cement-retained implant-supported zirconiabased crowns decreased the fracture resistance of the restoration. Designing a ledge in the zirconia framework around the access hole may increase the fracture resistance of the restoration. [ABSTRACT FROM AUTHOR]

Aim: The objective is to evaluate the effect of shades of monolithic zirconia on the microhardness and sorption/solubility of the underlying two dual-cured resin types of cement. Materials and Methods: Eighty samples of two dual-cured resin cement discs were polymerized under 60 monolithic zirconia discs in three shades and directly activated resin discs of cement were used as the control group (n = 10). After 24 h storage at 37°C in an incubator, Vickers microhardness and the sorption and solubility were measured. Statistical Analysis Used: Two-way ANOVA , one-way ANOVA, Independent t-test, Tukey's honestly significant difference, and Tamhane's T2 tests. Results: The mean microhardness of the Variolink N resin cements were significantly higher than Panavia SA ones (P < 0.001). Furthermore, Variolink N cements exhibited lower sorption/solubility than Panavia SA resin cements (both P < 0.05). The ceramic shade had a significant influence on the microhardness of both cements (P < 0.001) but had no significant effect on the sorption/solubility of resin cements (P > 0.05). Conclusion: Interposition of monolithic zirconia decreases the microhardness of resin cement especially Panavia SA. In Variolink N, by increasing the chroma saturation of ceramics, the microhardness decreased, however in Panavia SA, it was altered by the shades, but not in a specific pattern. For both cements, there were no statistical differences between the sorption/solubility of samples photo-cured under different shades. There was a reverse correlation between microhardness and water sorption/solubility of both cements. [ABSTRACT FROM AUTHOR]

Background and Aim: Dimensional accuracy of impressions is crucial to the quality of fixed restorations. This accuracy can be highly affected by the type of core and impression materials. This study aimed to assess the effect of different core materials on dimensional accuracy of two silicone impression materials. Materials and Methods: In this in vitro study, three master core models were fabricated of amalgam, composite resin, and nickel--chromium. Of each model, 30 impressions were taken; 15 with additional and 15 with condensational silicone impression material. The accuracy of impressions of the three core materials was assessed by measuring two linear dimensions and one vertical dimension on the stone casts. Statistical Analysis: Data were analyzed with two-way analysis of variance and Scheffe post hoc test (α = 0.05). Results: Accuracy of the three measured dimensions was significantly affected by both the impression and core materials (P < 0.05). Additional silicone was significantly more accurate in linear dimensions, and impressions of the amalgam core were significantly more accurate than other cores in linear dimensions. Conclusion: Additional silicone impression material had more detail reproduction, and the impressions of amalgam core were more accurate than the composite and nickel--chromium core materials. [ABSTRACT FROM AUTHOR]

Aims and Objectives: This study aimed to determine the biometric dimensions of three human permanent teeth in the occlusal/incisal-cervical and apical, buccolingual, and mesiodistal directions, and its relationship with age in adults in Shiraz, Iran. Materials and Methods: The samples included 50 upper canines, 50 maxillary first premolars, and 50 maxillary second molars, extracted from patients aged 25-55 years. Total length, crown labial surface length, crown palatal surface length, crown mesiodistal width, root length, and some other biometrical characteristics of the teeth were measured by using a Vernier caliper with 0.05-mm accuracy. The samples were divided into two age groups: patients aged below 45 years (younger adults group), and those aged over 45 years (older adults group). The data were analyzed by using independent t-test. P < 0.05 was considered as the significance level. Results: Most parameters such as the total length, crown mesiodistal and labiopalatal width, as well as the root length decreased in older adults group in all the three tested permanent teeth. Conclusion: During a lifetime, the crown length, mesiodistal, and buccolingual dimensions seem to decrease because of the physiological and pathological tooth wear. The tooth wear in a mesiodistal dimension is more frequent in posterior teeth than in the anterior ones. [ABSTRACT FROM AUTHOR]

Introduction: Marginal adaptation is the most critical item in long-term prognosis of single crowns. This study aimed to assess the marginal quality as well asthe discrepancies in marginal integrity of some PFM single crowns of posterior teeth by employing parallel radiography in Shiraz Dental School, Shiraz, Iran. Methods: In this descriptive study, parallel radiographies were taken from 200 fabricated PFM single crowns of posterior teeth after cementation and before discharging the patient. To calculate the magnification of the images, a metallic sphere with the thickness of 4 mm was placed in the direction of the crown margin on the occlusal surface. Thereafter, the horizontal and vertical space between the crown margins, the margin of preparations and also the vertical space between the crown margin and the bone crest were measured by using digital radiological software. Results: Analysis of data by descriptive statistics revealed that 75.5% and 60% of the cases had more than the acceptable space (50μm) in the vertical (130±20μm) and horizontal (90±15μm) dimensions, respectively. Moreover, 85% of patients were found to have either horizontal or vertical gap. In 77% of cases, the margins of crowns invaded the biologic width in the mesial and 70% in distal surfaces. Conclusion: Parallel radiography can be expedient in the stage of framework try-in to yield some important information that cannot be obtained by routine clinical evaluations and may improve the treatment prognosis. [ABSTRACT FROM AUTHOR]

Statement of the Problem: Increasing the sintering temperature is suggested by some manufacturers as a way to enhance the translucency of monolithic zirconia crowns. Meanwhile, its effect on the marginal fit and compressive strength of the restoration is not fully understood., Purpose: This study aimed to evaluate the effect of sintering temperature on the marginal fit and compressive strength of monolithic zirconia crowns., Materials and Method: In this in vitro study, thirty crowns of pre-sintered monolithic zirconia were milled and sintered in a special furnace at either 1450°C or 1550°C (n=15 per group). The marginal gaps were measured at 18 spots on the dies with a digital microscope. To evaluate the compressive strength, the specimens were cemented on brass dies by using conventional glass ionomer cement. Vertical load was applied by a universal testing machine until fracture. One-way ANOVA test was used to analyze the results (α=0.05)., Results: The marginal gap was not significantly different between the two groups ( p = 0.062). A significantly higher mean value of compressive strength was observed in crowns sintered at 1550°c (1988.27±635.09 N) than those sintered at 1450 °c (1514.27±455.11 N) ( p = 0.026)., Conclusion: Although increasing the sintering temperature would not affect the marginal gap of monolithic zirconia crowns, it could significantly improve the compressive strength of zirconia restorations., Competing Interests: The authors declare no conflicting interest., (Copyright: © Journal of Dentistry.)

Statement of the Problem: Structural integrity and dimensional stability are the key factors that determine the clinical success and durability of luting cements in the oral cavity. Sorption and solubility of self-adhesive resin luting cements in food-simulating solutions has not been studied sufficiently., Purpose: This study aimed to compare the sorption and solubility of 2 conventional and 2 self-adhesive resin-based luting cements immersed in four different storage media., Materials and Method: A total of 32 disc-shaped specimens were prepared from each of four resin luting cements; seT (SDI), Panavia F (Kuraray), Clearfil SA Cement (Kuraray), and Choice 2 (Bisco). Eight specimens of each material were immersed in all tested solutions including n-heptane 97%, distilled water, apple juice, or Listerine mouth wash. Sorption and solubility were measured by weighing the specimens before and after immersion and desiccation. Data were analyzed by SPSS version 18, using two-way ANOVA and Tukey's HSD test with p≤ 0.05 set as the level of significance., Results: There was a statistically significant interaction between the materials and solutions. The effect of media on the sorption and solubility was material-dependent. While seT showed the highest values of the sorption in almost all solutions, Choice 2 showed the least values of sorption and solubility. Immersion in apple juice caused more sorption than other solutions (p≤ 0.05)., Conclusion: The sorption and solubility behavior of the studied cements were significantly affected by their composition and the storage media. The more hydrophobic materials with higher filler content like Choice 2 resin cement showed the least sorption and solubility. Due to their lower sorption and solubility, these types of resin-based luting cements are recommended to be used clinically.