جستجوی مقالات مرتبط با کلیدواژه "microhardness" در نشریات گروه "پزشکی"

 This in vitro study compared the remineralization potential of Dabur red (DR), a non-fluoridated herbal toothpaste, with Colgate Strong Teeth (CST), a fluoride-based toothpaste, on permanent teeth with artificially created white spot lesions. Vickers microhardness (VMH), quantitative light-induced fluorescence system (QLF), and scanning electron microscopy (SEM) were used for data analysis.

 Enamel samples were prepared from the buccal surface of forty-five extracted maxillary premolars and subjected to demineralization to achieve adequate fluorescence loss (ΔF). The samples were divided into DR, CST, and control groups (n=15) and underwent 21 days of pH cycling. VMH was measured at baseline and after 21 days. QLF imaging was performed on days 7, 14, and 21. One randomly selected sample from each group underwent SEM examination to compare morphological variations. The statistical analysis was conducted using SPSS 22.0. Intra-group comparisons were made with repeated measures of analysis of variance (ANOVA), and one-way ANOVA with Tukey’s post-hoc test was utilized for inter-group comparisons (P<0.05).

 Mean VHN increased significantly in all three groups from baseline (DR=40.47, CST=41.91, control=36.42) to the 21st day (DR=119.47, CST=120.36, control=74.36) (P=0.00). Significant differences were found between the control and test groups, but not between DR and CST. No statistically significant difference was observed in ΔF at baseline and 7 days, but there were significant differences among the groups at 14 and 21 days. SEM images revealed dense mineralization for both DR and CST.

 After 21 days of in vitro remineralization, both DR and Colgate toothpaste demonstrated similar remineralizing potential as evaluated by surface MH and QLF.

 This study evaluated the efficacy of grape seed extract (GSE) on the remineralization of primary tooth enamel alone or in combination with remineralizing agents.

 The initial microhardness value of 90 primary tooth enamel samples was calculated; then, the samples were demineralized. The post-demineralization hardness of the samples was measured and the samples were randomly divided into 6 groups as follows: G1: negative control, G2: GSE, G3: NaF, G4:Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), G5: GSE+NaF, and G6: GSE+CPP-ACP (n=15). Oral environment pH cycle was applied and hardness measurements were repeated after treatments. The samples were stained with 1% rhodamine B dye and sectioned, and the lesion depth was measured. Statistical significance was set at P<0.05.

 The hardness decrease of the GSE and GSE+NaF groups was less than the other groups (P<0.05). The decrease was also less in the other groups than in the control group (P>0.05). GSE showed a positive effect when combined with NaF in maintaining microhardness but did not show the same effect when combined with CPP-ACP (P<0.05). Concerning penetration depth, all the groups had statistically lower values than the control group (P<0.05). The lowest penetration rates were observed in the GSE+NaF and GSE+CPP-ACP groups (P<0.05).

 The lowest hardness decrease was observed in the GSE and GSE+NaF groups, and the lowest penetration rates were observed in the GSE+NaF and GSE+CPP-ACP groups. It has been determined that a 15% GSE solution might be used as an alternative to fluoride in primary tooth remineralization and can increase the effectiveness of fluoride when used together.

This study aimed to synthesize an herbal remineralizing paste containing the extracts of Miswak, licorice, aloe vera, propolis, and honey and compare its effect with 5% sodium fluoride (NaF) and 1.23% acidulated phosphate fluoride (APF) on demineralized enamel microhardness.

 This experimental study was conducted on 72 extracted sound premolars. After obtaining the extracts and synthesis of the herbal paste, the baseline microhardness was measured, and the samples underwent a 14-day pH cycling. Next, the teeth were randomly assigned to six groups (N=12) for application of (I) 5% NaF for one minute, (II) 1.23% APF for one minute, (III) herbal paste for one minute, (IV) herbal paste for five minutes, (V) herbal paste for 15 minutes, and (VI) herbal paste for six hours. The microhardness was measured again. Data were analyzed by one-way analysis of variance (ANOVA) (alpha=0.05).

The mean final microhardness was significantly higher than the primary microhardness in all groups (P<0.05). The highest microhardness was noted in group IV, followed by II, VI, I, V and III. One-way ANOVA revealed no significant difference between the final microhardness of study groups (P=0.97).

 The effect of synthesized herbal paste on demineralized enamel microhardness was comparable to that of 5% NaF and 1.23% APF. Due to the lack of a significant difference in duration of application, this paste may be applied for one minute to benefit from its remineralizing effects.

 The preventive treatments of primary caries lesions are essential for preventing destructive damage to the tooth structure. One of the common treatments is the application of casein phosphopeptide-amorphous calcium phosphate (CCP/ACP) paste on the enamel surface. The aim of this study was to investigate the effect of different percentages of nano-bioactive glass (nBG) incorporation into synthesized CPP/ACP paste on the remineralization of demineralized enamel.

 In general, 24 extracted human intact premolar teeth were selected, and their crowns were removed for this purpose. Each crown was cut into two halves, and each half was considered as a sample. The samples were placed in a demineralizing solution at a pH rate of 4.6 for 8 hours, in artificial saliva for 1 hour, and again in a remineralizing solution at a pH rate of 7 for 15 hours. The pH cycling was performed for 14 days to demineralize the enamel surface. The samples were randomly divided into 3 groups (n=16), including G1 (without treatment), G2 (treated with synthesized CPP/ ACP paste containing 5% nanobioglass), and G3 (treated with synthesized CPP/ACP paste containing 10% nanobioglass). The paste was then placed directly on the surface of the demineralized enamel for 4 minutes (twice a day for 28 days). The samples were subjected to the Vickers microhardness test. Finally, data were analyzed using SPSS (version 19) and the analysis of variance and Tukey’s tests (α = 0.05).

 There was a significant difference between microhardness values in G1 and G2, as well as G1 and G3 (P<0.05). However, no statistically significant difference was observed between G2 and G3 (P>0.05).

 The results showed adding bioactive glass into synthetic CPP/ACP paste increases enamel remineralization in spite of the percentage of bioactive glass incorporation.

Chemical agents, in combination with mechanical methods, play an important role in reducing microbial plaque on denture surfaces. However, these methods might change the mechanical behavior of acrylic resins, including microhardness and surface roughness. This in vitro study investigated the effect of two disinfectants, i.e., water and sodium hypochlorite, on the microhardness of conventional heat-cured and TiO2 nanoparticle-reinforced acrylic resins.

Sixty acrylic resin specimens were divided into two groups, and the samples in each group were randomly assigned to three subgroups (n=10). Heat-cured specimens and 1 wt% TiO2 acrylic resin were prepared and immersed in three solutions: water, a solution prepared with NatureDent pills, and 1% sodium hypochlorite for 30, 60, and 90 days. Microhardness tests were performed on each sample at each immersion stage. The data were analyzed using descriptive statistical methods, three-way and one-way ANOVA, repeated-measures t test, and Tukey HSD tests using SPSS 17. P values<0.05 were considered significant.

All three independent parameters, including resin, solution, and time, significantly affected microhardness (P<0.05). The microhardness of both specimen types, i.e., conventional heat-cured and TiO2 nanoparticle-reinforced acrylic resins, immersed for 30, 60, and 90 days, was the highest and lowest in water and hypochlorite solutions, respectively. Regarding 90 days, the microhardness values of conventional heat-cured and TiO2 nanoparticle-reinforced acrylic resins were 17.050±0.094 and 19.953±0.053 in water, 15.675±0.069 and 18.965±0.037 in hypochlorite, and 16.713±0.122 and 19.39±20.113 in NatureDent solutions, respectively.

Disinfecting two types of acrylic resin specimens decreased their microhardness as a function of immersion time for up to 90 days in the three solutions. However, the magnitude of hardness lost was less for TiO2 nanoparticles-reinforced acrylic resin.

The prevalence of using different esthetic methods increases the possibility of close contact between them with potential adverse interactions. This study aimed to compare the surface changes (microhardness and roughness) in two types of feldspathic porcelain after laser bleaching and post-bleach polishing.

12 standardized rectangular specimens were prepared for each porcelain group (conventionally layered and CAD-CAM milled). Vickers microhardness and roughness were evaluated before and after the bleaching procedure and after polishing. Data were statistically analyzed using repeated measures ANOVA and t test (P<0.05).

The surface roughness of both groups increased significantly after laser bleaching (P<0.001 for conventional and P=0.004 for CAD-CAM porcelains). The polishing process reduced the roughness of both groups; the reduction was significant in conventional specimens (P=0.020). The surface hardness values did not change significantly in the groups after the bleaching and post-bleach polishing stages (P=0.142). Generally, the average surface roughness of CAD-CAM specimens was significantly lower (P<0.001), and the surface microhardness of the CAD-CAM group was significantly higher than conventional porcelains (P=0.011).

Laser bleaching significantly increased the surface roughness of feldspathic porcelains; however, it did not affect the surface microhardness significantly. Unlike CAD-CAM specimens, polishing significantly improved the surface smoothness of conventional porcelains.

Different factors play a role in causing tooth decay. Modern dentistry is looking for a way to prevent tooth decay and suggests different ways to increase remineralization. The aim of this study was to evaluate the effect of nanohydroxyapatite toothpaste and mouthwash on remineralization of primary enamel lesions and obstruction of tubules.

In this study, 90 human extracted central teeth were used. Artificial decay was induced by placing the specimens for 72 hrs in a demineralization solution in an incubator at 37 °C. Hardness of the specimens was determined by a microhardness test before any surface treatment. The specimens were then divided randomly into 6 groups of 15. For 1-6 groups, the specimens were subjected to a pH cycling for 14 days, which included 3 hrs of demineralization and 21 hrs of remineralization. At the same time, 1-3 groups were in contact with diluted toothpaste in a ratio of 1:3 with deionized water at a rate of 5 ml twice a day for two min. Eac specimen of 4-6 groups was exposed to 5 ml of three types of mouthwashes for one min. Then, the specimens were cut in the buccolingual direction in order to simultaneously evaluate the dentinal tubules and Vickers microhardness test was performed again and the before and after microhardness values were compared. Then, the percentage of deposition on the surface and tubule obstruction were analyzed using SEM (Scanning electron microscope) (P=0.006). Data were analyzed using SPSS24 software bu the descriptive statistics, ANOVA analysis of variance, and multiple Tukey comparisons.

The results of analysis of variance test showed that there was a statistically significant difference in the microhardness changes between study groups (P=0.006). Also, in-group analysis of microhardness changes, there was a significant difference (P<0.0001). Besides, only in the group containing 0.5% nanohydroxyapatite toothpaste, more than 50% tubule deposition and obstraction was observed (P<0.05).

According to the present study, nanohydroxyapatite can be one of the treatment strategies to repair incipient lesions of teeth and the addition of nanohydroxyapatite, preferably to toothpaste, increases the dental microhardness.

This study aimed to assess the effect of strontium-doped 45S5 bioglass (BG) and Nd:YAG laser on the microhardness of demineralized enamel.

In this in vitro, experimental study, 65 sound enamel samples were prepared of human premolars and polished, and then immersed in a demineralizing solution for 10 weeks. The samples were randomly divided into 5 groups of control, BG, laser, laser plus BG, and BG plus laser. Two samples of each group underwent assessment of surface morphology under a scanning electron microscope. Finally, the microhardness of samples was measured using a Vickers hardness tester, and data were analyzed by ANOVA.

The mean microhardness of the BG group was significantly higher than that of other groups (P<0.05). The lowest microhardness was noted in the control group. The difference in microhardness was significant between laser and laser plus BG groups (P<0.05). Further, the BG plus laser group had a significant difference in microhardness with BG and control groups (P<0.05). The difference between laser plus BG and control groups was also significant in this respect (P<0.05). Eventually, maximum morphological changes were observed in the BG group.

Overall, BG seems to be effective for the treatment of incipient enamel caries. It effectively increases enamel microhardness and decreases mineral loss while preserving the integrity of the enamel surface.

Statement of the Problem: One of the problems with light-cured composite resins is the limitation and inadequate depth of curing and polymerization, resulting in low surface microhardness and restoration failure.
The present study aimed to compare the surface microhardness of two different bulk-fill composite resins and one conventional composite resin using the Vickers microhardness test.
In the present in vitro study, 108 samples from two different bulk-fill composite resins (Tetric N Ceram and Xtrafil) and one conventional composite resin (Filtek Z250) were prepared in metallic molds (2×4×10 mm) (n=36 for each composite resin). Six samples from each composite resin (n=6) underwent a hardness measurement test at specific depths (0.1, 1, 2, 3, 4 and 5mm). The samples were then stored at 37ºC for 24 hours, followed by a microhardness test at the depths mentioned above.
In all the composite resin samples, microhardness decreased with an increase in depth. The highest microhardness was recorded in Filtek Z250, followed by Xtrafil, with no significant difference. The lowest microhardness was recorded in Tetric N Ceram bulk-fill. Both bulk-fill composite resins at all the depths exhibited depth-to-surface standard microhardness (>80%).
According to the results, both evaluated bulk-fill composite resins exhibited favorable surface microhardness up to a depth of 5 mm.

Tooth bleaching changes the microhardness and mineral content and color of the tooth. The present study aimed to evaluate the effect of carbamide peroxide on microhardness, mineral content and color change in white spot lesions.

Thirty-two samples were selected without caries, cracks and stains, and immersed in 0.5% chloramine-T for one week. Then the tooth crowns were separated. The teeth were artificially decayed by pH cycling. For bleaching on the enamel, a coating of 10% carbamide peroxide gel with a thickness of 1 mm was used for 8 hours. Samples were stored in artificial saliva for 16 hours. Bleaching process lasted for 14 days. Microhardness, color changes, calcium and phosphorus levels were measured before and after bleaching. Paired t-test and one-sample test were used to analyze the data.

The microhardness test results were 338.02± 90.15 and 320.94±87.41 before and after bleaching, respectively. microhardness of the samples significantly decreased after bleaching compared to before bleaching (P<0.001). Calcium and phosphorus content in samples after bleaching was not significantly different from before bleaching (P>0.05). The mean color change coefficient (∆E) after bleaching was 6.82±3.96. ∆E in the studied samples was significantly higher than the standard (∆E =3.3).

Bleaching with 10% carbamide peroxide significantly reduced microhardness. There was no change in the mineral content of the enamel and color change was proper. It can be concluded from this study that bleaching with carbamide peroxide can be successful.

Background:

 Dental caries occurs due to the imbalance in the course of demineralization-remineralization in favor of demineralization. With remineralization, some signs of halted progression could be observed in the primary stages. The aim of this study is to in-vitro investigation of the effect of Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP), fluoride varnish, and fluoride gel on the microhardness of the enamel of permanent teeth.

In this in vitro study, 344 specimens prepared from human premolars were randomly divided into four groups (n=86 specimens in each group). After preparing the specimens, the initial enamel value was first evaluated by Vickers microhardness technique. The specimens were immersed in a demineralizing solution and then treated with remineralizing compounds (I. Control, II. Fluoride varnish, III. Fluoride gel and IV. CPP-ACP). Microhardness values were re-measured at the end of demineralization and remineralization stages. The data were analyzed using SPSS software (version 16.0).

The results of the present study indicated a statistically significant difference in all groups in terms of initial enamel microhardness (0.288 ± 42.77), remineralization (0.213 ± 26.89), and demineralization values (0.167 ± 63.87) (p <0.001). Besides, there was a statistically significant difference in different groups in terms of remineralization values (p <0.001). In other words, the mean microhardness was 241.21 ±15.60 in Group III, 221.12 ± 75.69 in Group II, 211.16 ± 43.04 in Group IV, and 178.21 ± 63.9 in group- I.

Conclusion :

All remineralizing compounds resulted in enhanced microhardness of the enamel. Nevertheless, the fluoride-containing products showed greater potential in improving the level of microhardness and strength of the teeth compared to the compounds containing CPP-ACP.

Preventing caries or stopping primary caries lesions is one of the most important goals of oral health care. The aim of this study was to compare the effect of flavonoids and the whey extract on tooth enamel by measuring the microhardness of enamel following its demineralization.

In general, 42 samples of healthy enamel were prepared in this experimental-laboratory study. After measuring the initial microhardness using Vickers hardness tester )Buehler, Lake Bluff, IL, USA(, the samples were immersed in the demineralization solution for 4 days and re-tested for microhardness. Then, the samples were randomly divided into three groups of 14 and treated, including the grape seed extract w/v8%, the whey extract, and the artificial saliva. The samples were in contact with the treatment material for 8 days in an incubator at 37° C and then their microhardness was evaluated again.

The analysis of covariance showed that there was a significant difference in the amount of microhardness changes between the study groups (P<0.001) so that microhardness changes were the highest in the grape seed extract group while they decreased in the control group. However, the post hoc test showed no statistically significant difference between the whey extract and grape seed extract groups (P=1.000). Finally, the control group had a statistically significant difference from the whey extract and grape seed extract groups.

Both grape seed extract and whey extract increased remineralization and the microhardness of tooth enamel compared to the control group. Thus, these two substances can be considered as natural and effective substances in the non-invasive treatment of carious lesions.

Preventing caries or stopping primary caries lesions is one of the most important goals of oral health care. The aim of this study was to compare the effect of flavonoids and the whey extract on tooth enamel by measuring the microhardness of enamel following its demineralization.

In general, 42 samples of healthy enamel were prepared in this experimental-laboratory study. After measuring the initial microhardness using Vickers hardness tester )Buehler, Lake Bluff, IL, USA(, the samples were immersed in the demineralization solution for 4 days and re-tested for microhardness. Then, the samples were randomly divided into three groups of 14 and treated, including the grape seed extract w/v8%, the whey extract, and the artificial saliva. The samples were in contact with the treatment material for 8 days in an incubator at 37° C and then their microhardness was evaluated again.

The analysis of covariance showed that there was a significant difference in the amount of microhardness changes between the study groups (P<0.001) so that microhardness changes were the highest in the grape seed extract group while they decreased in the control group. However, the post hoc test showed no statistically significant difference between the whey extract and grape seed extract groups (P=1.000). Finally, the control group had a statistically significant difference from the whey extract and grape seed extract groups.

Both grape seed extract and whey extract increased remineralization and the microhardness of tooth enamel compared to the control group. Thus, these two substances can be considered as natural and effective substances in the non-invasive treatment of carious lesions.

Statement of the Problem: 

In an attempt to fasten and simplify the restoration process, a new class of composite resins, called the bulk fill composite resins have been introduced, which has been claimed to achieve a depth of cure (DOC) of 4 mm without affecting the properties of the material.

The Purpose of this study was to investigate the effect of different shades, thicknesses and viscosities on the DOC of bulk-fill composites.

Four bulk-fill composites [FiltekTMBulkfill Flowable (FBF), FiltekTM Bulkfill posterior (FBP), Tetric N-Flow bulkfill(TNF), Tetric N-Ceram bulkfill(TNC)] and a conventional composite, FiltekTM Z250XT Universal (FZ) were evaluated. samples (n=5) were made using two different shades( light and dark), thicknesses (2 and 4mm) and viscosities (flowable and sculptable). Microhardness was conducted on top and bottom surface using Vickers microhardness tester and DOC calculated as the bottom/top ratio. Statistical analysis was done using a mannwhitney test at p < 0.05.

DOC ranged between 52-95%. FBF composite exhibited the lowest overall hardness numbers. At 2-mm thickness, all the samples achieved an appropriate DOC. However, at 4-mm thickness, only the light shades for FBF and TNF samples achieved a DOC very close to 0.8. At 4-mm thickness, the light shades for FBF, TNF and FZ samples exhibited significantly higher DOC compared to dark shades. For 4-mm-thick samples, DOC of FB )dark and light shades (and DOC of TN (light shade( were different in the flowable type from the sculptable type.

Shade and viscosity influence DOC of bulk-fill composites at 4-mm depths. For bulk-fill composites, 20s light curing appears insufficient for 4mm bulk-fill placement.