Changes In Surface Microhardness Research Articles

Effect of whitening dentifrices on dental enamel: an analysis of color, microhardness, and surface roughness in vitro.

This study aimed to evaluate the influence of different whitening toothpastes on color change and alteration in enamel surface roughness and microhardness compared to a conventional toothpaste. Fifty bovine incisors were selected, cleaned, and stored before being divided into five groups: a conventional toothpaste group and three whitening toothpaste groups containing different abrasive agents: silica, hydrogen peroxide, and activated charcoal. Specimens underwent simulated brushing, staining with black tea solution, and subsequent analyses of color, surface roughness, and microhardness. Statistical analysis was performed using three-way ANOVA and Tukey post-hoc tests (P .05). The results showed that the color analysis revealed similar whitening potential among all toothpastes. They showed significant differences in surface roughness (P .001) and microhardness (P .001) after simulated brushing. While all toothpastes caused a decrease in microhardness, the charcoal-based toothpaste showed a significant increase in surface roughness compared to the initial condition. All toothpastes demonstrated whitening capability. Surface roughness changed after brushing with activated charcoal-based whitening toothpaste, but final roughness was similar across all groups. Whitening toothpastes led to a decrease in enamel microhardness, with similar final performance across all toothpastes analyzed.

Effectiveness of New Isomalt-Containing Toothpaste Formulations in Preventing Dental Caries: A Microbial Study.

Human dental enamel slabs were allocated to six groups (30/group) at random: De-ionized distilled water (DDW), and toothpaste containing 10% Isomalt, 1100 ppm fluoride, 0.05% cetylpyridinium chloride [CPC] (ICT); 10% Isomalt, 1100 ppm fluoride (IT); 10% Isomalt, 1100 ppm fluoride, 1.5% Sodium lauryl sulfate [SLS] (IST); 1100 ppm fluoride only (FT); 1100 ppm fluoride with SLS (FST). The enamel slabs were exposed to caries development via plaque growth in a Microbial Caries Model for 7 days. Toothpastes were applied as slurries (one toothpaste-three DDW) for 2 min twice daily. Demineralization was measured as the change in surface microhardness (ΔSMH) and amount of mineral lost (∆Z), and these metrics were assessed using Transverse Microradiography. Intra-group (SMH) and intergroup (%∆SMH and ∆Z) comparisons were paired t-test and Tukey's test (α = 0.05), respectively. With SMH, demineralization was found to be significant (p < 0.001) in all groups compared to sound enamel baseline, except ICT group. With %ΔSMH, all other groups had significantly (p < 0.001) less demineralization compared to DDW. Significantly (p < 0.001) greater demineralization was observed in IT, FT and FST compared to ICT, and no significant difference was observed between IST and ICT or FT. With ∆Z, relative to the DDW group, the inhibition of demineralization was significant (p < 0.0001) in all groups at varying percentages. Toothpaste containing 10% Isomalt, 1100 ppm fluoride, and 0.05% CPC demonstrated greater efficacy in inhibiting caries development amid dental plaque compared to toothpaste containing only 1100 ppm fluoride.

Effect of Different Modification Techniques on Mechanical and Physical Properties of E-Max CAD Substrate

The world's best-selling glass-ceramic is IPS E.Max CAD. It is known for its versatile applications and is appropriate for the effective manufacturing of comprehensive dental restorations. This experimental study aimed to evaluate the morphological changes, surface roughness, and micro-hardness after modification techniques with KHF2 and NH4HF2 acid etching on e-max cad substrate. Materials and Methods: Forty disc shape of E.Max CAD specimens (thickness 3mm and diameter 10mm) were fabricated and divided into four groups according modification techniques (control group, sandblasting by 70µm of Al2O3, etching with 70 mg of KHF2 and etching with 70mg of NH4HF2),10 samples for each group. Surface roughness, micro-hardness, and microstructure changes of e-max CAD substrate have been measured. Results: The higher mean value for the surface roughness (Ra) was in the group (ECNH4HF2), followed by (ECKHF2) whereas the lowest mean value of surface roughness was in the group (ECC) followed by (ECSB). While for the micro-hardness test, the (ECKHF2) group demonstrated the highest mean value in comparison with other treated groups. Finally, SEM results for both untreated and sandblasted groups revealed there is a smooth and no deep morphological change for their surfaces. While the SEM analysis revealed that the e-max cad surfaces after KHF2 and NH4HF2 showed rough morphology with fine grains result and random porosities. Conclusions: Etching with KHF2 and NH4HF2 yielded higher microstructure changes and roughness than other techniques. While KHF2 etchant was more effective on E.Max CAD surface micro-hardness in comparison with other treated groups.

In Vitro Evaluation of Remineralization Potential of Five Toothpastes on Soft Drink-Eroded Human Enamel and Dentine.

The purpose of this in vitro study was to evaluate the potential remineralization of enamel and dentine erosion lesions after the application of five different toothpastes. A total of 104 enamel and dentine samples were prepared from maxillary third molars. Each group was divided according to the toothpaste application mode (topical = 56; brushing = 48) and the toothpaste used seven topical groups and six brushing groups (n = 8). The groups included negative control (NC), positive control (PC), Sensodyne Pronamel (SP), Regenerate (R), Regenerate with boosting serum (R+), Colgate Duraphat 5000 (CD), and tooth mousse (TM). The statistical analysis showed significant surface microhardness (SMH) change. All enamel groups showed a significant decrease in SMH compared to NCfor both application modes. However, no significance was recorded between test groups. Similar results were observed between dentine groups and their relevant controls for both application modes, except brushed Rand R+groups, which were insignificant to their NC. For topical groups, TMshowed a significant increase in SMH. While Rand R+showed lower loss than SPand CD. All tested agents offered a degree of remineralization in both enamel and dentine with no significant difference between agents in enamel groups while R, R+, and TMoffered better results in dentine groups. For dentine groups, similar findings were observed with superior tooth surface protection with the application of TM over other agents. Tooth surface remineralization was achieved when agents were either applied topically or brushed over the surface.

Changes in physical properties of universal composites and CAD/CAM materials after bleaching and antioxidant applications: Scanning electron microscope and atomic force microscope evaluation.

To evaluate the effects of vital bleaching agents and the subsequent application of ascorbic acid (AA) to universal composites and resin-based CAD/CAM blocks on the physical properties of materials. In the study; G-enial A'chord (GCA), Filtek Ultimate (FU), Clearfil Majesty (CM) composites, and LAVA Ultimate (LU), Cerasmart (GCC) CAD/CAM blocks were used. The materials were divided into two subgroups based on the applied bleaching type (n = 30/group): office bleaching (OB) and home bleaching (HB). After bleaching, AA was applied to the samples. Surface roughness, microhardness, and color change values of all samples were measured at three stages: initial (I), post-bleaching (B), and post-bleaching+AA application (BA). Statistical analysis was performed using 3-way Mixed ANOVA with Bonferroni correction (p < .05). The BA of the HB group of CM; the B of the HB group of LU; the B roughness values of both the OB and HB groups of GCC were significantly lower than I. The microhardness values of all the materials examined decreased significantly after both bleaching (p < .05). With regard to the AA application, it significantly decreased Ra values in the HB group of CM. In addition, it significantly increased the microhardness values in the HB groups of CM and GCC. Also, the ΔE001 and ΔE002 values for the FU and GCC HB groups were significantly higher than in the OB groups (p < .05). Bleaching and AA application affected the physical properties of the materials. The physical properties of the materials either remained unchanged or improved with the application of AA after bleaching. RESEARCH HIGHLIGHTS: This article presents in vitro results of a new approach that has not been studied before. Ascorbic acid, used to increase the bond strength between the material-tooth after bleaching, was used to eliminate the adverse effects of bleaching on the physical properties of aesthetic restorative materials. Additionally, the effects of all procedures on the materials were examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). As a result of the study, it was concluded that the application of ascorbic acid after bleaching improved the physical properties of some of the materials.

A new role for resveratrol: Protection of enamel against erosion

ObjectiveThe aim of this study was to determine the effect of different concentrations of resveratrol in protecting enamel against initial dental erosion in vitro. MethodsNinety bovine enamel samples (4 × 4 mm) were divided into six groups: Phosphate buffered saline (negative control; PBS), Commercial solution (Elmex Erosion Protection™; positive control) and resveratrol at 4 different concentrations (1, 10, 100 or 400 µg/mL). Initially, the samples were incubated in saliva for the formation of the acquired pellicle (250 µL, 1 h, 37 °C, 250 rpm). Afterward, the samples were incubated in the respective treatments (250 µL, 1 min, 37 °C, 250 rpm) and then reincubated in saliva (250 µL, 1 h, 37 °C, 250 rpm). Finally, the samples were subjected to an erosive challenge by incubating in 1 % citric acid (1 mL, pH 3.5, 1 min, 25 °C, 250 rpm). The percentage surface microhardness change (% SMC) was assessed using a microhardness tester. Data were analyzed by Kruskal-Wallis and Dunn's tests (p < 0.05). ResultsThe treatments with Elmex™ and resveratrol (1, 10 and 100 µg/mL) significantly protected enamel compared to the negative control, without significant differences among them. However, the group treated with the highest resveratrol concentration (400 µg/mL) did not show a significant difference from the negative control. ConclusionsResveratrol at concentrations ranging from 1 to 100 µg/ml was effective in preventing loss of enamel surface microhardness. Clinical significanceThis result suggests a potential new direction for the development of dental products based on resveratrol for the prevention of dental erosion.

Change in surface properties of two different dental resin composites after using various beverages and brushing

BackgroundThe study aimed to evaluate the influence of various beverages; with and without brushing; on the surface mechanical properties of two resin composites.MethodsA total of 160 disc-shaped specimens were prepared for each of the following dental composites; nanohybrid ormocer (Admira fusion, VOCO GmbH, Cuxhaven, Germany) and nanohybrid resin composite (Grandio, VOCO GmbH, Cuxhaven, Germany). The baseline surface hardness and roughness measurements were carried out after 24 h. The composite samples were randomly distributed into one of the two groups; brushing and non-brushing, which were further divided into one of the four subgroups (n = 10); artificial saliva as control, coffee, red wine, and soft drink. In the non-brushing group, the specimens were immersed in the different beverages for five minutes three times daily for 30 days. The same procedure was done for the brushing group, in addition to brushing the specimens for five seconds. The surface hardness and roughness measurements were repeated after 30 days. One-way ANOVA and independent t-tests were used for statistical analysis.ResultsThe soft drink had the most deteriorating effect and artificial saliva had the least. The change in surface properties was higher in the brushing subgroups. Grandio exhibited a higher change in surface microhardness while Admira fusion exhibited a higher change in surface roughness.ConclusionsThe surface properties of both dental resin composites were negatively affected by using beverages and brushing.

Surface morphological evolution and microhardness change of Cr12MoV steel by pulsed laser polishing

Laser polishing is gaining more and more attention because of its environmental friendliness and ability to process complex surfaces. It is considered as one of the technologies to replace traditional methods in the mold industry. In this work, the variation pattern of surface roughness with single pulse energy density and light-out overlap rate during nanosecond pulsed laser polishing of Cr12MoV steel was investigated. The surface roughness increased and then decreased with increasing single-pulse energy density and beam overlap rate, respectively. The lowest surface roughness was found to be 0.50 μm, which is a decrease of 79.34 % compared to the untreated sample. The effect of each parameter on the surface morphology during the laser polishing process is explained. There is minimal austenitization on the surface of the sample after laser polishing. The second phase of the remelting layer disappeared. The microhardness of the remelting layer increased by 36.17 % because the grain size was reduced by 30.65 %. This work further explains the mechanism transformation threshold for pulsed laser polishing of steel. With 95 % beam overlap, the melting and gasification energy density thresholds for Cr12MoV steel are respectively 1.269 J/cm2 and 2.937 J/cm2. The beam overlap rate of 95.5 % is the critical condition for continuous melt movement. It provides a new idea for the mechanism judgment of pulsed laser polishing.

Impact of different chemical denture cleansers on the properties of digitally fabricated denture base resin materials.

To compare the impact of three different chemical denture cleansers (CDCs) (Corega, chlorhexidine, and hydrogen peroxide) on the surface roughness, microhardness, and color stability of 3D-printed, computer-aided design and computer-aided manufacturing (CAD-CAM) milled, and heat-polymerized denture base material (DBM). A total of 420 disc-shaped specimens (10 ±0.1 × 2 ±0.1mm) were fabricated using three different construction techniques: three-dimensional (3D) printing (n = 140), CAD-CAM milling (n = 140), and heat-polymerization (n = 140). Sixty specimens (20 of each DBM) were used for baseline (pre-immersion) measurements (T1) for the tested surface properties (hardness [n = 10/material] and roughness [n = 10/material]). The remaining 360 specimens (n = 120/material) were investigated for surface roughness, microhardness, and color change after immersion for 1 year (T2) in distilled water or CDCs (n = 30/solution and n = 10/test). The data were analyzed using two-way ANOVA, one-way ANOVA followed by post-hoc Tukey's test at a significance level of less than 0.05. Significant differences were observed in the effects of the tested CDCs on the surface roughness, micro-hardness, and color stability of varying DBM specimens (p<0.05). Corega showed the highest surface roughness and color change in all DBMs while H2O2 resulted in the lowest microhardness for all DBMs. The lowest changes in all tested properties were seen with distilled water followed by chlorhexidine. A significant effect of type of cleanser, denture base material, and the interaction between the two was seen on all measured properties (p<0.05). The tested CDCs significantly affected the surface properties of all DBMs but at varying degrees. Corega produced the highest negative effect on roughness and color change while H2O2 dramatically affected the microhardness. Prolonged use of CDCs should be cautiously followed.

Impact of citric acid exposures on the erosion susceptibility and microhardness of anatomically different enamel surfaces

ObjectiveTo determine the indentation-load dependency of the observed changes in surface microhardness of occlusal and buccal enamel polished surfaces before and after a dietary acid exposure. MethodsEnamel specimens (n = 20) were obtained from previously extracted human molars. The samples were divided into two groups, buccal and occlusal (n = 10). Both groups were exposed to 0.3% citric acid at pH 2.7 over different time periods. The mean 3D step-heights defined by ISO 5436–1 standard of the erosion scar was calculated using a white light profilometer. Vickers microhardness testing was carried out to discriminate the surface mechanical changes and different loading regimens used to provide an estimate of depth related changes to the enamel sub-surface. Differences between groups were assessed using two-way ANOVA and post-hoc Sidak’s multiple comparisons tests at α = 0.05. ResultsA two-way ANOVA identified that erosion duration significantly influenced step-height (p < 0.01). The factorial analysis also identified a significant increase in step-height on occlusal surfaces compared to buccal surfaces (p < 0.01). At 5 min the mean 3D step-heights µm ± (SD) on the occlusal surface was 3.6 ± (0.65) and on the buccal surface was 3.1 ± (0.60) which increased after 60 mins to 32.9 ± (3.43) and 30.1 ± (3.34), respectively. In contrast to the non-eroded surface, increasing the indentation load on eroded enamel resulted in a significantly increased HV (p < 0.01) suggesting a significant modification to the enamel's response to an increasing indentation load. SignificanceOcclusal surfaces following acid exposure were more prone to erosion scar relative to buccal surfaces in vitro. Different loading regimens estimated the hardness of the erosive lesion from the outermost surface through the unaffected enamel.

Comparison of the Surface Properties of 3D-printed Permanent Restorative Resins and Resin-based CAD/CAM Blocks.

This study aimed to investigate the surface roughness, microhardness, and color changes of resin-based computer-aided design/computer-aided manufacturing (CAD/CAM) blocks and 3D-printed permanent resins in different beverages. Resin-based CAD/CAM blocks (Cerasmart 270 and Grandio Blocs) and 3D-printed permanent restorative resins (Crowntec and Permanent Crown) were used in this study. A total of 96 specimens were prepared from CAD/CAM blocks and 3D-printed permanent resins. The initial surface roughness, microhardness, and shade value of the specimens were measured. Then, the specimens prepared from each material were divided into three subgroups (n=8) and immersed in tea, coffee, and distilled water for 30 days. After the specimens were immersed in the beverages, the surface roughness, microhardness, and tone values were measured again. The data were statistically analyzed using a two-way analysis of variance test (p<0.05). No statistically significant difference was found in the surface roughness values of the resin-based CAD/CAM blocks and 3D-printed resins (p<0.05). Resin-based CAD/CAM blocks showed statistically significantly higher microhardness than 3D-printed permanent resins (p<0.05). Although the color changes in 3D-printed resins in tea and coffee were similar to those in resin-based CAD/CAM blocks on the first and seventh days, more color changes appeared in the 3D-printed resins after 30 days. The surface roughness and microhardness values of the specimens submerged in tea, coffee, and distilled water showed no statistically significant changes (p<0.05). Although the surface roughness of 3D-printed permanent resins was similar to that of resin-based CAD/CAM blocks, they had a lower microhardness value. Moreover, 3D-printed permanent resins showed more color changes in tea and coffee.

Comparative Evaluation of the Remineralizing Potential of Silver Diamine Fluoride, Casein Phosphopeptide-amorphous Calcium Phosphate, and Fluoride Varnish on the Enamel Surface of Primary and Permanent Teeth: An In Vitro Study.

With the paradigm shift in the management of dental caries, the focus is now laid on remineralization therapies that can arrest the progression of the disease and remineralize the subsurface lesions. The purpose of this study was to determine and compare the remineralizing potential of silver diamine fluoride (SDF), casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), and fluoride varnish (FV) on enamel surfaces in primary and permanent teeth. A total of 120 primary anterior teeth and 120 premolars were used to prepare enamel blocks in acrylic resin. The mean baseline surface microhardness (SMH) for each sample was determined using a microvickers hardness testing machine. Thereafter, the samples were randomly and equally distributed into groups and subgroups based on the materials used, that is, SDF, CPP-ACP, FV, and distilled water (control). After subjecting the samples to a pH cycling regime, SMH was determined again and the percentage change in SMH was calculated. The data were tabulated and subjected to statistical analysis using an independent t-test and one-way analysis of variance (ANOVA). In primary teeth, the least mean percentage reduction in SMH was observed after the application of FV followed by SDF, CPP-ACP, and control. In permanent teeth, both SDF and FV showed the least percentage reduction of enamel SMH followed by CPP-ACP and control. Silver diamine fluoride (SDF), FV, and CPP-ACP showed remineralizing potential in both primary and permanent teeth. Kaur S, Bhola M, Bajaj N, et al. Comparative Evaluation of the Remineralizing Potential of Silver Diamine Fluoride, Casein Phosphopeptide-amorphous Calcium Phosphate, and Fluoride Varnish on the Enamel Surface of Primary and Permanent Teeth: An In Vitro Study. Int J Clin Pediatr Dent 2023;16(S-1):S91-S96.

Changes in the properties of bulk-fill resins under conditions of gastroesophageal reflux and bulimia

Aim: Evaluate the roughness, microhardness and color change of different Bulk Fill resins when submitted to the condition of gastroesophageal reflux and bulimia. Methods: 60 specimens (n = 10) of Bulk-Fill composite resins were made: M1 – Filtek™; M2 – Tetric N-Ceram and M3 – OPUS, through a matrix 2x6 mm and light cured by the VALO light source. After polishing, initial analyzes (48 hours - T0) of surface roughness (Ra), microhardness (VHN) and color change (ΔE) were performed. To simulate the oral condition of severe gastroesophageal reflux and bulimia, the specimens were immersed in hydrochloric acid (S1) (pH 1.7) 4 minutes a day, for 7 days. Control group specimens were immersed in artificial saliva (S2). Subsequently to immersions, mechanical brushing was performed for 3 minutes, three times a day, simulating 7 days of brushing. And again, the analyzes of Ra, VHN and ΔE were performed (7 days - T1). Thus, hydrochloric acid immersion, mechanical brushing and Ra analysis were repeated at 14 days (T2) and 21 days (T3); and T2, T3 and T4 (3 years) for VHN and ΔE. Results: After Shapiro-Wilk statistical test, ANOVA and Tukey test with Bonferroni adjustment (p&gt;0.05), M3 showed the lowest Ra at all times compared to the other resins, while the highest Ra was at T0. M1 and T1 showed higher VHN. And M2 and T4 showed higher ΔE. Conclusion: Bulk Fill resins can be indicated for patients with Gastroesophageal Reflux and Bulimia, nonetheless, Tetric N-Ceram resin showed the worst results.

In Vitro Evaluation of the Effects of Different Beverages on the Surface Microhardness of a Single-Shade Universal Composite.

The aim of this in vitro study was to analyze the influence of various beverages on the surface microhardness of a single-shade composite resin. Seventy-five Omnichroma composite discs were fabricated and divided into five subgroups according to the beverages. The groups were Group A: tea; Group B: coffee; Group C: beer; Group D: whisky; and Group E: artificial saliva. The samples were immersed in their respective beverages for 15 minutes per day for 15 days. The Vickers microhardness values were taken before and after the immersion of the composite disc samples in their respective beverages. A one-way analysis of variance (ANOVA) test was conducted using IBM SPSS Statistics software version 23 (IBM Corp., Armonk, New York, USA), with a statistical significance level of 5%. It was observed that there was a reduction in the surface microhardness of the composite resin after immersion in most of the solutions. An increase in the mean percentage change of surface microhardness was observed in the beer group (29%; mean difference = 16.52±12.05), followed by the coffee group (27.2%; mean difference = 15.51±9.28). The least mean percentage change in microhardness was noted in group E, artificial saliva (8.5%; mean difference = 4.81±3.04). The surface microhardness of composite resin can be influenced by the type of beverages used for immersion and the duration of immersion.However, it is important to note that the interaction between composite resin and various beverages is influenced by a complex interplay of multiple variables.

Effect of silver diamine fluoride/potassium iodide treatment on the prevention of dental erosion in primary teeth: an in vitro study

IntroductionDental erosion has a great effect on oral health, when diagnosed it is irreversible, this sets the importance of different preventive measures being investigated against dental erosion.AimThis in vitro study aims to evaluate the effectiveness of silver diamine fluoride and Potassium iodide (SDF-KI) in comparison to casein phosphopeptide-amorphous calcium phosphate fluoride (CPP-ACPF) varnish, sodium fluoride (NaF) varnish, silver diamine fluoride (SDF) alone and deionized water as a control group in the prevention of dental erosion in primary teeth and assessing its staining effect.Materials and methodsForty deciduous teeth enamel specimens were randomly allocated into the five study groups. Tested materials were applied. An erosive challenge was done by immersing the specimens in a citric acid-containing soft drink with pH 2.85, for 5 min, 4 times/day, for 5 days. Changes in surface microhardness, mineral loss, and color change were evaluated besides recording of the surface topography and surface roughness for selected specimens.ResultsThe highest decrease in surface microhardness was recorded in the control group (−85.21 ± 10.60%), with a statistically significant difference (p = 0.002). SDF-KI group (−61.49 ± 21.08%) showed no statistically significant difference when compared to CPP-ACPF, NaF, and SDF groups. For calcium and phosphorous loss, control group was statistically significantly higher compared to the treatment groups (p = 0.003) and (p < 0.001) respectively, while there was no statistically significant difference between the tested treatment groups. The highest mean value for color change was recorded in SDF group (26.26 ± 10.31), followed by SDF-KI group (21.22 ± 12.87) with no statistically significant difference between groups.ConclusionsSDF-KI is as effective as CPP-ACPF, NaF varnishes and SDF in the prevention of dental erosion in primary teeth, there was no statistically significant difference regarding its staining potential.

Effects of silver diamine fluoride on demineralization protection after a secondary acid challenge.

This investigation describes the effects of 5% sodium fluoride varnish and 38% silver diamine fluoride on demineralization protection of human enamel lesions of three different severities after a secondary acid challenge. Specimens underwent color and enamel surface microhardness change measurements after demineralization and treatment events. Transverse microradiography was conducted following the secondary demineralization. After treatments, enamel surface microhardness change showed that 24-hour lesions treated with fluoride varnish had less rehardening than 24-hour lesions treated with silver diamine fluoride (p<0.05), whereas 144-hour lesions from both treatment groups showed a beneficial decrease in surface microhardness change that was markedly better in samples treated with silver diamine fluoride (p<0.05). After the secondary demineralization, 24- and 144-hour lesions treated with silver diamine fluoride showed a sustained beneficial decrease in enamel surface microhardness change when compared to fluoride varnish-treated samples of the corresponding lesion severity (p<0.05). Transverse microradiography showed no difference between fluoride varnish- and silver diamine fluoride-treated samples of any corresponding lesion severity, indicating that remineralization in both fluoride varnish- and silver diamine fluoride-treated samples was proportional to each other after a secondary acid challenge. Using silver diamine fluoride may have comparable benefits to fluoride varnish in mineral loss prevention.

In Vitro Evaluation of the Effect of Fluoride Varnish Application Frequency on Initial Enamel Lesions

Purpose: The aim of this study is the in vitro evaluation of the effect of fluoride varnish application at different frequencies on initial enamel lesions by surface microhardness (SMH) measurements. Material and Methods: This in vitro experimental study was performed on 80 extracted unerupted third molar teeth. The teeth were divided randomly into 4 groups: Group 1: Fluoride varnish application once a year, Group 2: Fluoride varnish application 4 times at 1 week intervals, Group 3: Fluoride varnish application 4 times a year with an interval of 3 months, Group 4: Application of fluoride varnish twice a year at 6-month intervals. Artificial enamel carious lesions were created by inserting the specimens in demineralization solution for 96 hours. The Vicker’s microhardness number (VHN) was measured at baseline, after demineralization and after fluor varnish application and 1 year after fluoride treatments of each group. The percent change in surface microhardness (% SMH change) was also calculated. Anova and Kruskall-Wallis H test, t-test and/or Wilcoxen sign test were used with 95% confidence levels to compare differences. Results: The surface microhardness values and recovery of surface hardness values of the groups were found as follows: Group 3&amp;gt; Group 2&amp;gt;Group 4&amp;gt; Group 1. VHN of Group 3 was statistically significantly higher than other groups (p&amp;lt;0.05). Conclusion: Fluoride varnish application 4 times a year with an interval of 3 months showed significantly higher enamel SMH than that of the other groups (p&amp;lt;0.05).

The Effect of Gastric Acid on the Surface Properties of Different Universal Composites: A SEM Study.

The aim of this study is to compare surface roughness and microhardness changes of three monochromatic (Omnichroma, Vittra Unique, and Charisma Diamond One) and three universal shade (Neo Spectra ST, G-ænial A'CHORD, and Nova Compo C) resin composites after exposure to simulated gastric acid. A total of 144 disc-shaped specimens (24 discs of each composite resin) were prepared using plexiglass molds (R = 5 mm × h = 2 mm) for evaluation from each material. Specimens of each material were divided into two main groups for the evaluation of the microhardness and surface roughness and also two subgroups for 7- and 14-day exposures to simulated gastric acid. Initial microhardness and surface roughness measurements of all samples were measured before immersion (T1) followed by exposing the samples to simulated gastric acid for 7 days (T2) and 14 days (T3), and then, the microhardness and roughness measurements were repeated. Randomly selected specimens of each material for each of the time intervals (T1, T2, and T3) were evaluated with scanning electron microscopy (SEM). One-way ANOVA revealed that the surface roughness and hardness values of all tested composite resin restorative materials show no statistically significant difference for the initial (T1) value (p > 0.05). Regarding the 7th day (T2) and 14th day (T3) surface roughness and microhardness value of all composites, there are statistically significant differences between the groups (p < 0.05), while there was no statistically significant difference between the surface hardness reduction percentage between the time intervals (p > 0.05). As a result of this in vitro study, increase in surface roughness and decrease in microhardness of the tested universal composite materials when exposed to simulated gastric acid were statistically significant.

Acid resistance of self-adhesive resin luting cements – changes in surface texture parameters and microhardness

ObjectivesWhen consumed in excess, acidic foods and beverages can cause dental erosions leading to irreversible loss of tooth substance. In many cases, prosthetic rehabilitation of the damaged teeth is mandatory. The aim of this in vitro study was to investigate, for the first time on this scale, the resistance of various commonly used self-adhesive resin luting cements (Bifix SE, VOCO; G-Cem LinkAce, GC; RelyX Unicem, 3 M Oral Care; SpeedCEM Plus, Ivoclar ) against acidic media, and to find out whether they can withstand long-term exposure. These results were compared with an adhesive resin luting cement (Panavia V5, Kuraray) that functioned as reference gold standard. Furthermore we applied area roughness parameters for surface texture analysis in the present investigation, to highlight their advantages for investigations on the surface quality of resin luting cements. MethodsSix specimens with identical diameter (10 mm) and thickness (3 mm) were prepared from each self-adhesive and adhesive resin luting cement and forwarded to an incubation in various acidic media for a period of 232 h. Conductivity and pH-values of each acidic medium was analyzed for each material group prior (t 0) and after exposure (t 1). The specimens were examined for Vickers microhardness and surface quality. For the evaluation of surface roughness, the parameters Sa, Sdr, Spc Spk, Sk, and Svk were investigated by using different filtered surfaces (S-L; S-F) according to ISO 25 178. Statistical analysis was conducted at a significance level of α = 0.050. ResultsFor the evaluation of the acid resistance of self-adhesive resin luting cements investigations on conductivity and pH-value assessment of storage solution appear unsuitable, while the assessment of microhardness and surface analysis revealed valid data. It could be shown that changes in surface texture of the resin luting cements can be determinend in qualitative and quantitative manner. While the microhardness and surface quality of some resin luting cements hardly changed, others showed significantly reduced values in microhardness and changes in their surface quality (p < 0.001). SignificanceThe data of the current study emphasize the relevance of interactions between resin luting cements and acids and suggest further laboratory and clinical studies to elucidate its impact on the clinical performance of the materials investigated

Longitudinal In Vitro Effects of Silver Diamine Fluoride on Early Enamel Caries Lesions.

This laboratory study evaluated the longitudinal surface microhardness changes in early, incipient, noncavitated, white-spot, enamel caries lesions treated with silver diamine fluoride (SDF). Five intervention groups (SDF, AgNO3, KF, 5% sodium fluoride varnish (FV), deionized water (DI)) × two-time intervals after intervention (immediate & delayed pH-cycling) resulted in 10 groups (n=18). Silver nitrate (AgNO3) and potassium fluoride (KF) groups served as controls to assist in evaluating if remineralization effects were due to the silver or fluoride component in SDF. Early, incipient, noncavitated, white-spot, enamel caries lesions were created in bovine enamel, the extent of demineralization was determined using Vickers surface microhardness (VHNlesion). Intervention treatments were applied. Half the specimens from each group underwent immediate 5-day pH-cycling, and half were stored in an incubator with artificial saliva for 2 weeks before undergoing 5-day pH-cycling. After pH-cycling, lesion hardness was evaluated using VHNpost. Specimens were then exposed to a second demineralization challenge, and lesion softening was evaluated (VHNsecdem). Hardness variables were calculated: ΔVHN = VHNpost - VHNlesion; ΔVHNsecdem = VHNsecdem - VHNpost. Data were analyzed using two-way ANOVA (α=0.05). Immediately cycled, SDF had significantly (p<0.0001) greater remineralization than DI, AgNO3, and FV. All delayed cycling groups had significantly greater remineralization than FV (p<0.0001). Significantly greater remineralization was noted in delayed AgNO3 (p≤0.0001), DI (p=0.0003), and FV (p=0.0006) compared to immediately cycled. After the second demineralization challenge, FV had significantly less surface softening than AgNO3 (p=0.0002), DI (p=0.0003), KF (p=0.0225), and SDF (p=0.0388) intervention groups. No significant difference was found between the pH-cycle timings (p=0.2710). Based the present findings, FV may be better suited than SDF to treat early, incipient, noncavitated, white-spot, enamel caries lesions.