Effect of simulated gastric acid on aesthetical restorative CAD-CAM materials' microhardness and flexural strength

Background

Gastric acid, which is among erosive substances, gradually rises to the mouth in individuals with reflux and bulimia nervosa disorders, and this causes various effects on dental restorations.

Aim

The objective of this study is in vitro investigation of gastric acid's effect on flexural strength and hardness on aesthetic restorative computer-aided design and computer-aided manufacturing (CAD-CAM) materials.

Materials and Methods

For this study, four materials have been used, namely Enamic (Vita), Superfect Zir (Aidite) Zirconia, IPS e.max CAD (Ivoclar Vivadent), and Mark II (Vita). From these four different materials, 24 samples with 14 × 4 × 1 dimensions in rectangular prism form are used, which makes a total of 96 samples. One group was separated as the control group, while the rest was allowed to wait at 37°C, 5 ml gastric acid for 96 hours. Hardness value and flexural strengths were measured as pre-exposure and post-exposure to gastric acid.

Results

There is a statistically significant difference between the groups in terms of the amount of decrease in the mean hardness after exposure to gastric acid compared to pre-exposure values (p: 0,000; P < 0,05). There was no statistically significant difference between the groups in terms of the amount of decrease in the post-exposure average flexural strength compared to the pre-exposure value (p: 0.063; P > 0.05). There is a statistically significant difference between the groups in terms of the average flexural strength after exposure to the acid.

Conclusions

According to the data obtained, it was concluded that exposure to gastric acid affects the hardness and flexural strength properties of dental restorative ceramic materials.

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

AIM

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.

MATERIALS AND METHODS

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%.

RESULTS

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).

CONCLUSION

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 Adding Silver-Doped Carbon Nanotube Fillers to Heat-Cured Acrylic Denture Base on Impact Strength, Microhardness, and Antimicrobial Activity: A Preliminary Study

Poly (methyl methacrylate) (PMMA), is an acrylic polymer substance that is mostly used for denture base applications. The purpose of this laboratory study was to investigate the effect of adding 0.05 wt.% Ag-doped carbon nanotubes (CNT) to PMMA-based (PMMA and MMA) denture base material on the impact strength, microhardness, and antimicrobial activity. A total of 60 heat-cured acrylic resin specimens were prepared. The specimens were randomly divided into two main groups (n = 30/group), according to the powder used: (a) control group, using heat-cured PMMA; (b) treatment group, using a powder prepared by blending 0.05 wt.% silver-doped CNT nanoparticles with heat-cured PMMA. The impact strength, microhardness and anticandidal activity for each group were assessed via the Charpy, Vickers and agar diffusion tests, respectively (n = 10/test for each subgroup). Data were analyzed using independent-sample t-tests (p ≤ 0.05). The results of the impact strength test revealed that the treated heat-cured PMMA-MMA with Ag-doped CNT (2.2 kJ/mm²) was significantly higher than that of the control heat-cured PMMA (1.6 kJ/mm²). Similarly, the Vickers microhardness of the treatment group (52.7 VHN) was significantly higher than that of the control group (19.4 VHN). Regarding the agar diffusion test, after 24 h of incubation, the treated heat-cured PMMA with the Ag-doped CNT exhibited significantly higher anticandidal activity than that of the control group. Therefore, Ag-doped carbon nanotubes could be considered as promising fillers for the dental heat-cured acrylic resin to improve the resistance of the resultant denture against sudden fractures, scratching, and candida invasion.

Effect of Dental Varnishes in Prevention of Enamel Demineralization Adjacent to Orthodontic Brackets

Aim

The aim of the current research was to assess the ability of different dental varnishes in averting enamel demineralization adjoining the orthodontic brackets.

Materials and Methods

Seventy-five premolars devoid of dental caries that were subjected to extraction for orthodontic purposes were employed in this research. The surface of enamel was etched with 37% phosphoric acid and subjected to primer application. Individual brackets were placed on the midregion of the buccal surfaces of the premolars with Transbond™ XT adhesive. Postbracket bonding, the dry premolar tooth samples were set aside cautiously. The samples were then allocated to three groups: Group I: Duraphat Varnish, Group II: Clinpro XT Varnish, and Group III: Profluorid Varnish. Every sample was independently subjected to immersion in demineralizing solution for a period of 96 h at 37°C in an incubator. Areas of demineralization were evaluated by documenting the microhardness along the severed surface using a microhardness tester equipped with a Vickers diamond.

Results

The highest surface microhardness was noted with Profluorid Varnish group at 328.48 ± 1.12 in pursuit by Clinpro XT Varnish group at 322.08 ± 0.04 as well as Duraphat Varnish group at 307.42 ± 0.28 with a statistically noteworthy dissimilarity amid the groups.

Conclusion

In conclusion, the three varnishes employed had an influence on the prevention of enamel demineralization surrounding the orthodontic brackets. Profluorid varnish however exhibited maximum efficiency in avoiding enamel demineralization versus Clinpro XT varnish as well as Duraphat varnish group.

Impact of Various Remineralizing Agents on Artificial White Spot Lesion on Primary Teeth-A Comparative Study

Aim

The aim of the current research was to assess the effectiveness of different remineralizing substances on artificial white spot lesions on deciduous teeth.

Materials and Methods

45 deciduous teeth without dental caries constituted the study group for this in vitro research. A 3 mm by 3 mm window of enamel was uncovered at the occluso-gingival midpoint of the coronal labial surface; an acid-resistant nail varnish was coated alongside the uncovered enamel surface of all specimens, employing vertical strokes. Demineralization was executed for the tenure of 72 hours at 37°C temperature in an incubator. The forty-five specimens, fifteen in each group, were assigned to the investigational groups plus a control group as: Group A: Control, Group B: Calcium sucrose phosphate (CaSP), Group C: Casein phosphopeptide-amorphous calcium phosphate-fluoride (CPP-ACPF). Microhardness tester was employed for testing the microhardness of the enamel surface using a Vickers diamond indenter laden with twenty-five milligrams for approximately ten seconds. Vickers hardness number (VHN) calculations for the microhardness were performed at baseline and on the fourteenth day.

Results

The CPP-ACPF group exhibited greater mean microhardness value at 236.14 ± 2.12, in pursuit by CaSP group with a score of 231.98 ± 3.16 and then the control group at 220.22 ± 5.08. An extremely statistically significant difference was seen amid the groups.

Conclusion

The current research arrived at a conclusion that both the remineralizing substances were certainly efficient in handling early dental caries, and additionally, casein phosphopeptide-amorphous calcium phosphate-fluoride (CPP-ACPF) was found highly efficient as a remineralizing substance, in pursuit by calcium sucrose phosphate (CaSP).

Evaluation of different remineralization agents in the treatment of natural caries-affected dentin in permanent teeth

BACKGROUND

In the preventive treatment protocol, providing remineralization of the tissue in demineralized dentin caries is an important step.

OBJECTIVE

In this in vitro study, the effectiveness of remineralization agents in natural caries-affected dentin (NCAD) were investigated.

METHODS

Forty caries slices were prepared from permanent molar dentin with International Caries Detection and Assessment System (ICDAS 2) (Code 3). The interventions with 8 days pH cycling were as follows: Deionized water (DW); 5% Sodium Fluoride (5% NaF) Varnish; Casein Phosphopeptide-Amorphous Calcium Fluoride Phosphate (CPP-ACFP); Calcium Glyserophosphate (CaGP) + Magnesium (Mg) + Xylitol. DIAGNOdent (Laser Fluorescence, LF), Surface Microhardness (SMH), and X-ray Fluorescence (XRF) Spectroscopy measurements were calculated before and after pH cycling.

RESULTS

LF values decreased between 5% NaF, CCP-ACFP and CaGP. NCAD treated with 5% NaF, CaGP and CCP-ACFP exhibited statistically higher hardness compared to the control group. After 5% NaF application, SMH values were significantly higher than the others. There was no statistically significant difference between baseline and after pH cycling hardness of the control group. After cycling, XRF showed that Ca and P concentrations were increased in all groups.

CONCLUSION

The application of agents used in the study could be recommended and promoted as a treatment option of caries dentin for conventional management of caries.

The Microhardness and Surface Roughness Assessment of Bulk-Fill Resin Composites Treated with and without the Application of an Oxygen-Inhibited Layer and a Polishing System: An In Vitro Study

The aim of this study was to assess the microhardness and surface roughness of bulk-fill resin composites treated with and without the application of an oxygen-inhibited layer (OIL) and a polishing system. This in vitro experimental study consisted of 72 resin composite blocks divided into three groups: Tetric N-Ceram Bulk Fill, Opus Bulk Fill APS, and Filtek Bulk Fill. Each resin composite group was further divided into two subgroups: with and without OIL control. Subsequently, surface roughness and microhardness were measured before and after polishing. A t-test was used to compare independent and related measures. For the intergroup comparison of variation before and after polishing, the Kruskal−Wallis test with Bonferroni post hoc was used considering a significance level of p < 0.05. When comparing surface roughness, significant differences were observed between Opus Bulk Fill resin composite with and without OIL control (p = 0.003) before polishing. The same occurred when comparing Tetric N-Ceram resin composite with and without OIL control (p = 0.039) after polishing. In addition, the surface roughness of Filtek Bulk Fill, Opus Bulk Fill, and Tetric N-Ceram Bulk Fill resin composites, with and without OIL control, decreased significantly after polishing (p < 0.001), while surface microhardness significantly increased (p < 0.05), with the exception of Opus Bulk Fill resin with OIL control (p = 0.413). In conclusion, OIL control and polishing significantly improved the surface roughness and surface microhardness of Filtek Bulk Fill and Tetric N-Ceram Bulk Fill resin composites. However, in the case of Opus Bulk Fill resin composite, only its surface roughness was significantly improved.

Effects of Sr/F-Bioactive Glass Nanoparticles and Calcium Phosphate on Monomer Conversion, Biaxial Flexural Strength, Surface Microhardness, Mass/Volume Changes, and Color Stability of Dual-Cured Dental Composites for Core Build-Up Materials

This study prepared composites for core build-up containing Sr/F bioactive glass nanoparticles (Sr/F-BGNPs) and monocalcium phosphate monohydrate (MCPM) to prevent dental caries. The effect of the additives on the physical/mechanical properties of the materials was examined. Dual-cured resin composites were prepared using dimethacrylate monomers with added Sr/F-BGNPs (5 or 10 wt%) and MCPM (3 or 6 wt%). The additives reduced the light-activated monomer conversion by ~10%, but their effect on the conversion upon self-curing was negligible. The conversions of light-curing or self-curing polymerization of the experimental materials were greater than that of the commercial material. The additives reduced biaxial flexural strength (191 to 155 MPa), modulus (4.4 to 3.3), and surface microhardness (53 to 45 VHN). These values were comparable to that of the commercial material or within the acceptable range of the standard. The changes in the experimental composites’ mass and volume (~1%) were similar to that of the commercial comparison. The color change of the commercial material (1.0) was lower than that of the experimental composites (1.5–5.8). The addition of Sr/F-BGNPs and MCPM negatively affected the physical/mechanical properties of the composites, but the results were satisfactory except for color stability.

Compressive strength, surface roughness, and surface microhardness of principle tricalcium silicate-based endodontic cements after universal adhesive application

Aims and Background

It was aimed to evaluate compressive strength (CS), surface roughness, and microhardness of mineral trioxide aggregate (ProRoot MTA) and Biodentine (BD) after adhesive application.

Materials and Methods

Tests was carried out according to international ISO standard. ProRoot MTA and BD were prepared in Teflon molds according to manufacturer's instructions: n = 210 for CS; n = 210 for microhardness. Samples were incubated for 7 days at 37°C in 100% humidity. Surfaces were smoothed with up to 2000 grits of silicon-carbide sandpaper on abrasive device at 150 rpm, randomly divided into seven groups (n = 15). Clearfil Universal Bond, All Bond Universal, and Single Bond Universal (SBU) were applied in both total-etch and self-etch (SE) modes. Adhesives were applied according to manufacturers' recommendations (no adhesive used in control). CS was performed at speed of 1 mm/min, microhardness at 100 gr for 15 s. The surface roughness of the samples was analyzed with atomic force microscopy. Two-way analysis of variance and post hoc Tukey tests were used for the evaluation of the data.

Results

Man CS and microhardness values between ProRoot MTA and BD were as follows: 24.9 N, 72.6 HV; 59.8 N, 59.0 HV, respectively. In CS, BD was higher than ProRoot MTA (P < 0.05). In other comparisons except for SBU SE group (P < 0.05), BD and ProRoot MTA showed similar results (P > 0.05). However, ProRoot MTA was found higher than BD regarding microhardness (P < 0.05). As a result of the adhesive application in both BD and ProRoot MTA groups, a decrease in surface roughness was observed compared to the control group.

Conclusion

BD exhibited better results than ProRoot MTA regarding CS. However, ProRoot MTA was found to be more successful than BD in terms of microhardness. BD and ProRoot MTA showed similar physical properties in terms of surface roughness. To improve regenerative procedures, besides the selection of bioceramic cements, the interaction between cements and materials applied during coronal restoration should be considered.

Effects of Color Modifier on Degree of Monomer Conversion, Biaxial Flexural Strength, Surface Microhardness, and Water Sorption/Solubility of Resin Composites

Color modifiers can be mixed with resin composites to mimic the shade of severely discolored tooth. The aim of this study was to assess the effects of a color modifier on the physical and mechanical properties of a resin composite. The composite was mixed with a color modifier at 0 wt% (group 1), 1 wt% (group 2), 2.5 wt% (group 3), or 5 wt% (group 4). The degree of monomer conversion (DC) was examined after light curing for 20 or 40 s. Biaxial flexural strength (BFS)/modulus (BFM), surface microhardness (SH), and water sorption (W_sp)/solubility (W_sl) were also tested. The DC of group 1 was significantly higher than that of groups 3 and 4. The increase in curing time from 20 to 40 s increased the DC by ~10%. The BFS, BFM, W_sp, and W_sl of all the groups were comparable. A negative correlation was detected between the concentration of color modifier and the BFS and DC, while a positive correlation was observed with W_sp. In conclusion, the color modifier reduced the DC of composites, but the conversion was improved by extending the curing time. The increase in color modifier concentration also correlated with a reduction in strength and the increase in the water sorption of the composites.

Effect of Acidic Beverages on Color Stability and Microhardness of Various Esthetic Restorative Materials: A Comparative Study

Aim:

The aim of this study was to assess the effect of acidic beverages on color stability and microhardness of various esthetic restorative materials.

Materials and Methods:

A total of 60 samples were included in the present study. Group I: Microhybrid composite resin, Group II: Nanoceramic, Group III: ORMOCER (Organically Modified Ceramics). 10 mm internal diameter and 5 mm depth of cylindrical aluminum mold of were utilized to prepare the samples. All the esthetic restorative samples were submerged for 10 min in 25 ml of acidic drink (Coca-Cola) each day up to 15 days. Vickers diamond intender was used to measure the microhardness of each sample. These values were calculated with baseline, 7^th, and 15^th days for final microhardness values.

Results:

The mean surface microhardness of 63.20 ± 0.46 was shown by Group III which was slightly more than that in Group II (60.08 ± 0.34) and Group I (58.10 ± 1.76). Analysis of covariance did not show any statistically significant difference between the groups. The samples in Group I showed the highest reduction in surface microhardness value after immersion into acidic drink, followed by Group II and Group III on 7^th day and 15^th day. A statistically significant difference (P < 0.001) was found on the 7^th day.

Conclusion:

The present study concludes that the Organically Modified Ceramics esthetic restorative material showed the finest behavior after being dipped in the acidic drink followed next by Nanoceramic and Microhybrid composite resin.

Rheological Properties, Surface Microhardness, and Dentin Shear Bond Strength of Resin-Modified Glass Ionomer Cements Containing Methacrylate-Functionalized Polyacids and Spherical Pre-Reacted Glass Fillers

The aim of this study was to prepare experimental resin-modified glass ionomer cements (RMGICs) containing low levels of hydroxyethyl methacrylate (HEMA) for pulp protection. Liquid and powder phases of the experimental RMGICs were polyacid functionalized with methacrylate groups and spherical pre-reacted glass fillers (SPG). Two types of liquid phase containing 0 wt. % HEMA (CM liquid) or 5 wt. % HEMA (CMH liquid) were formulated. The experimental RMGICs were prepared by mixing SPG fillers with CM liquid (F1) or CMH liquid (F2). Rheological properties were examined using a strain-controlled rheometer (n = 5). The Vickers microhardness (n = 5) and dentin shear bond strength (SBS) (n = 10) of the materials were tested. Commercial pulp protection materials (Vitrebond and TheraCal LC) were used as comparisons. The viscosity and surface microhardness of F1 (22 m Pa·s, 18 VHN) and F2 (18 m Pa·s, 16 VHN) were significantly higher than those of Vitrebond (6 mPa·s, 6 VHN) and TheraCal (0.1 mPa·s, 7 VHN). The SBS of F1 (10.7 MPa) and F2 (11.9 MPa) was comparable to that of Vitrebond (15.4 MPa) but higher than that of TheraCal LC (5.6 MPa). The addition of 5 wt. % HEMA showed no significant effect on viscosity, surface microhardness, or SBS of the experimental RMGICs. The experimental materials showed higher viscosity and microhardness but similar SBS when compared with the commercial RMGIC.

Effect of Polishing on the Surface Microhardness of Nanohybrid Composite Resins Subjected to 35% Hydrogen Peroxide: An In vitro Study

Aim:

The use of bleaching agents, despite being a conservative treatment, can cause a decrease in the surface microhardness of dental resins, affecting their aesthetics and performance. The aim of this study was to evaluate the in vitro effect of polishing on the surface microhardness of nanohybrid composite resins that were subjected to bleaching with 35% hydrogen peroxide.

Materials and Methods:

This cross-sectional, in vitro experimental study consisted of 30 composite resin samples made according to ISO 4049-2019 and divided equally into two groups (A and B) which were subjected to 35% hydrogen peroxide bleaching. Group A was subjected to polishing procedure, whereas group B was the control group. The samples were stored in distilled water at 37°C for 24 h. The Vickers microhardness was determined with a load of 100 g-f for 10 s. The data were analyzed with Student’s t-test for independent samples at a confidence level of 95%.

Results:

The surface microhardness of the group that was subjected to polishing (A) obtained a mean of 78.07 ± 7.96 HV, whereas for the group that was not subjected to polishing (B) the mean was 65.67 ± 5.22 HV. The difference between groups (A and B) was statistically significant (P < 0.001).

Conclusion:

Nanohybrid composite resins previously subjected to 35% hydrogen peroxide gel significantly increased their surface microhardness when subjected to polishing when compared with unpolished nanohybrid composite resins.

Evaluation of photopolymerization efficacy and temperature rise of a composite resin using a blue diode laser (445 nm)

The purpose of this study was to evaluate the photopolymerization efficacy of a diode laser (445 nm) for use with a composite containing camphorquinone and to estimate the safety of the method related to the temperature rise. Five cylindrical composite specimens were prepared for each thickness: 1, 2, and 3 mm. Three light-curing modes were investigated: a light emitting diode (LED) unit and a diode laser (445 nm) with output powers at 0.7 W or 3 W. Evaluation of the polymerization efficacy was based on Vickers hardness measurements, and the highest temperatures at the bottom of the specimens were recorded using a K-type thermocouple. The highest microhardness was observed after the diode laser curing operating at 3 W. A comparison of the microhardness of the 0.7 W laser cured specimens with the LED cured specimens showed a statistically significant difference in favor of the laser curing. Laser curing operating at 3 W resulted in extremely high temperatures. Laser curing at 0.7 W resulted in statistically significantly higher maximum temperatures than did LED curing for both 1 mm thick (52.9°C against 45.4°C) and 3 mm thick (43.6°C against 40.9°C) specimens. Diode laser (445 nm) may be an alternative for photopolymerization of composite materials and may result in a higher degree of conversion and depth of cure of composites than what has been seen with LED curing units when they emit at the same energy density.

Surface microhardness of a self-adhesive composite in comparison with conventional composite resins

BACKGROUND

The surface microhardness of dental composites greatly affects the durability of restorations.

OBJECTIVES

The aim of this study was to compare the surface microhardness of a self-adhesive composite with that of other conventional composites. The effect aging has on surface microhardness was also evaluated.

MATERIAL AND METHODS

In this in vitro experimental study, the composite resins were poured into molds measuring 3 mm × 3 mm × 6 mm and cured for 40 s. The samples were then immersed in distilled water at 37°C for 24 h. After polishing, the surface microhardness of the samples was measured using the Vickers hardness tester. For this purpose, a 100-gram load was applied to 3 points on the surface of each composite sample for 20 s, and the mean value of surface microhardness was used as the Vickers hardness number. The samples were then subjected to 30,000 thermal cycles at 5-55°C in order to age them; after that, their surface microhardness was measured again. The one-way analysis of variance (ANOVA) was used for the statistical analysis.

RESULTS

The maximum hardness value before and after aging belonged to Filtek® Z250, followed by Premise™ Flow and Vertise™ Flow, with significant differences between them (p < 0.001). After aging, the surface microhardness of all composites decreased significantly (p < 0.001). The effect of aging on surface microhardness was the same in all groups (p > 0.05).

CONCLUSIONS

The surface microhardness of composites was significantly different before and after aging. All composites experienced a reduction in their surface microhardness after aging.

The effect of operator-induced variability on the physical properties of ProRoot MTA

Aims

The aim of this study was to compare the influence of operators on the microhardness and compressive strength of mineral trioxide aggregate (MTA).

Materials and Methods

Forty dental specialists were asked to prepare a series of MTA samples. The tested material was ProRoot MTA (DentsplyMaillefer, Switzerland). Each participant prepared one sample to a consistency they considered acceptable for use in practice (improvised group) and another one according to the manufacturer's recommended water-to-powder (WP) ratio (pre-weighed group). The samples were incubated at 37°C and 95% humidity for 4 days. Parameters evaluated in this study were microhardness and compressive strength.

Results

Operators mixed MTA samples with varying WP ratios. However, there was no significant difference between the microhardness and compressive strength values of MTA samples between the improvised, the pre-weighed and the control groups. MTA was mixed in a thicker consistency than the manufacturers recommended ratio (0.33) by 62.5% of the operators.

Conclusion

According to the results of this study, even though the WP ratios that were utilized in the clinical setting vary, microhardness and compressive strength values of MTA was not significantly affected.

Comparative evaluation of three different toothpastes on remineralization potential of initial enamel lesions: A scanning electron microscopic study

Background

The early enamel lesions are reversible as it is a process involving mineral transactions between the teeth and saliva.

Aim

To evaluate the efficiency of three different tooth pastes on remineralization potential of initial enamel lesions using Vickers Micro hardness Test and Scanning electron microscopy.

Materials and Methods

Artificial carious lesions were prepared in human enamel with demineralizing solution. The treatment agents included were Colgate sensitive plus^® toothpaste, Regenerate enamel science™ toothpaste, BioRepair^® toothpaste and control as Deionized water. All the samples were subjected to treatment solutions as per the pH cycling model for 12 days to simulate the daily oral environment's acid challenge. The remineralization parameters-surface hardness and surface roughness of enamel blocks were evaluated with Vickers indenter and Scanning electron microscope respectively. Statistical Analysis: ANOVA test was used to check mean differences between the groups. Post hoc analysis was done using Tukey's post hoc test. SEM images were graded according to Bonetti et al grading criteria.

Results

As per statistical analysis, maximum remineralization of enamel blocks occurred after applying Colgate Sensitive Plus^® tooth paste followed by BioRepair^® tooth paste and Regenerate enamel Science™ toothpaste. Least remineralization potential was shown by control group.

Conclusion

Colgate sensitive plus tooth paste with Pro Argin™ formula can be regarded as a potential remineralising agent. It can be concluded as a noninvasive means of managing early enamel carious lesions.

Comparative evaluation of compressive strength and surface microhardness of EQUIA Forte, resin-modified glass-ionomer cement with conventional glass-ionomer cement

PURPOSE

The study aimed to evaluate and compare the compressive strength and surface microhardness of EQUIA Forte, light cure, and conventional glass-ionomer cement (GIC).

METHODOLOGY

Fifty-four pellets of G-Coat (GC) Gold Label 2, GC Gold Label light-cured universal restorative material, and EQUIA Forte GIC were prepared of dimensions (6 × 4) mm and were divided into three groups (18) each and were stored at 37°C for 1 h and then immersed in 20 ml of deionized water, artificial saliva, and lactic acid six each, respectively, over 30 days. Samples were subjected to surface microhardness and compressive strength test on the 1^st day, 7^th day, and 30^th day. Results were subjected to ANOVA and Bonferroni post hoc test.

RESULTS

Comparing the compressive strength of EQUIA Forte from day 1 to 30 when placed in artificial saliva, there was a significant increase on day 30 (P = 0.007); compared to other groups. The surface microhardness of EQUIA Forte from day 1 to 30 when placed in artificial saliva nonsignificantly decreased comparing to other groups.

CONCLUSION

Surface microhardness and compressive strength of EQUIA Forte were significantly high in comparison to the other groups.

Comparative evaluation of remineralizing efficacy of biomimetic self-assembling peptide on artificially induced enamel lesions: An in vitro study

Background

The biomimetic self-assembling peptide technology is a paradigm for dental hard tissue regeneration.

Aim

To investigate the efficacy of biomimetic self-assembling peptide (P₁₁-4) on enamel remineralization compared to casein phosphopeptide-amorphous calcium phosphate fluoride (CPP-ACPF) and fluoride-based delivery systems.

Materials and Methods

Artificial enamel lesions were created on buccal surfaces of 40 extracted human molars. Specimens were randomly assigned to four groups (n = 10) according to the remineralizing agent used: G1 - control: artificial saliva, G2 - fluoride varnish, G3 - CPP-ACPF varnish, G4 - self-assembling peptide agent. All products were applied according to the manufacturer's instructions and the specimens were stored in daily renewed artificial saliva. Surface microhardness (SMH) was assessed at baseline, after demineralization, after 1 week and after 4 weeks storage. SMH values were analyzed using ANOVA and Tukey's post hoc test.

Results

Self-assembling peptide showed the highest statistically significant mean SMH followed by fluoride and CPP-ACPF while the lowest mean SMH was found in artificial saliva. However, no statistically significant difference was found between fluoride and CPP-ACPF. Higher statistically significant mean SMH was found after 4 weeks compared to 1 week remineralization in all groups.

Conclusions

Self-assembling peptide confers the highest remineralizing efficacy compared to fluoride and CPP-ACPF, showing a promising, noninvasive regeneration potential. Furthermore, extended period of time helped attain more benefits from the remineralizing regimens applied.

Push-Out Bond Strength and Surface Microhardness of Calcium Silicate-Based Biomaterials: An in vitro Study

OBJECTIVE

This was an in vitro evaluation of push-out bond strength and surface microhardness of calcium silicate-based biomaterials in coronal and apical root dentin.

MATERIALS AND METHODS

Ninety sections (2 mm thick) of coronal and apical root dentin were obtained from roots of 60 extracted teeth; the canals were enlarged to a standardized cavity diameter of 1.3 mm. Sections were randomly divided into 6 groups (n = 15 per group), and cavities were filled with Biodentine™, BioAggregate, or ProRoot mineral trioxide aggregate (MTA), according to the manufacturers' instructions. Push-out bond strength values were measured using a universal testing machine under a compressive load at a speed of 1 mm/min. Samples were analyzed under a light microscope to determine the nature of bond failure. Ten samples (2 mm thick) were prepared for all the materials, and Vickers microhardness was determined using a digital hardness tester. Data were analyzed using one-way analysis of variance and Tukey-Kramer multiple comparison tests at a significance level of p < 0.05.

RESULTS

Biodentine (42.02; 39.35 MPa) and ProRoot MTA (21.86; 34.13 MPa) showed significantly higher bond strengths than BioAggregate (6.63; 10.09 MPa) in coronal and apical root dentin, respectively (p < 0.05). Biodentine also differed significantly from ProRoot MTA in coronal dentin. Bond failure was predominantly adhesive in Biodentine and ProRoot MTA, while BioAggregate showed predominantly mixed failure. ProRoot MTA (158.52 HV) showed significantly higher microhardness and BioAggregate (68.79 HV) showed the lowest hardness.

CONCLUSION

Biodentine and ProRoot MTA showed higher bond strength and microhardness compared to BioAggregate.

Spectroscopic and Mechanical Properties of a New Generation of Bulk Fill Composites

Objectives: The aims of this study were to in vitro evaluate the degree of conversion and the microhardness properties of five bulk fill resin composites; in addition, the performance of two curing lamps, used for composites polymerization, was also analyzed.

Materials and Methods: The following five resin-based bulk fill composites were tested: SureFil SDR®, Fill Up!™, Filtek™, SonicFill™, and SonicFill2™. Samples of 4 mm in thickness were prepared using Teflon molds filled in one increment and light-polymerized using two LED power units. Ten samples for each composite were cured using Elipar S10 and 10 using Demi Ultra. Additional samples of SonicFill2, (3 and 5 mm-thick) were also tested. The degree of conversion (DC) was determined by Raman spectroscopy, while the Vickers microhardness (VMH) was evaluated using a microhardness tester. The experimental evaluation was carried out on top and bottom sides, immediately after curing (t0), and, on bottom, after 24 h (t24). Two-ways analysis of variance was applied to evaluate DC and VMH-values. In all analyses, the level of significance was set at p < 0.05.

Results: All bulk fill resin composites recorded satisfactory DCs on top and bottom sides. At t0, the top of SDR and SonicFill2 showed the highest DCs-values (85.56 ± 9.52 and 85.47 ± 1.90, respectively), when cured using Elipar S10; using Demi Ultra, SonicFill2 showed the highest DCs-values (90.53 ± 2.18). At t0, the highest DCs-values of bottom sides were recorded by SDR (84.64 ± 11.68), when cured using Elipar S10, and Filtek (81.52 ± 4.14), using Demi Ultra. On top sides, Demi Ultra lamp showed significant higher DCs compared to the Elipar S10 (p < 0.05). SonicFill2 reached suitable DCs also on bottom of 5 mm-thick samples. At t0, VMH-values ranged between 24.4 and 69.18 for Elipar S10, and between 26.5 and 67.3 for Demi Ultra. Using both lamps, the lowest VMH-values were shown by SDR, while the highest values by SonicFill2. At t24, all DC and VMH values significantly increased.

Conclusions: Differences in DC and VMH among materials are suggested to be material and curing lamp dependent. Even at t0, the three high viscosity bulk composites showed higher VMH than the flowable or dual curing composites.

Effect of three different pastes on remineralization of initial enamel lesion: an in vitro study

OBJECTIVE

Dental caries in enamel is unique as enamel is both acellular and avascular. Fluoride is one of the most effective remineralizing agents in caries prevention. The purpose of the study was to assess whether nano-hydroxyapatite and CPP-ACP can be used as an alternative to fluoride for remineralization of early carious lesions.

STUDY DESIGN

Initial artificial carious lesions were prepared in enamel with demineralization solution. The treatment materials used as remineralizing agents were Nano-hydroxyapatite (10%), CPP - ACP (10%), NaF (1000 ppm) and Deionized water (negative control). Surface microhardness (SMH) measurements were performed before/after demineralization and after 3, 6, 9 and 12 days of pH cycling and the percentage surface microhardness recovery (%SMHR) was calculated. The specimens were then examined by scanning electron microscope.

RESULTS

Percentage surface microhardness recovery of nano-hydroxyapatite and fluoride was significantly greater than CPP - ACP and negative control. There was no significant difference of %SMHR between n-HA and fluoride at different time periods in the pH cycling. SEM analysis revealed n-HA particles were deposited on the demineralized enamel surface which formed a new surface layer. When observed under SEM CPP - ACP failed to show any significant surface remineralization while surface globular crystal depositions with multiple discrete porosities were evident with fluoride.

CONCLUSION

It was concluded that nano-hydroxyapatite and fluoride had the potential to remineralize initial enamel lesions. CPP - ACP can be used as an effective adjunct to fluoride therapy but cannot be used as an alternative to fluoride.

Enamel remineralization assessment after treatment with three different remineralizing agents using surface microhardness: An in vitro study

AIM

The aim of this study is to evaluate the enamel remineralization after treatment with three different remineralizing agents using surface microhardness assessment.

MATERIALS AND METHODS

This in vitro study involves 50 enamel samples divided into five groups of 10 samples each. The positive control group consisted of intact enamel and a negative control group consisted of demineralized enamel samples. All groups excluding the positive control group were subjected to demineralization following which three of these groups were remineralized using remineralizing agents (casein phosphopeptide amorphous calcium phosphate [CPP-ACP] [GC tooth mousse], casein phosphopeptide amorphous calcium phosphate with fluoride [CPP-ACPF] [GC tooth mousse plus], sodium fluoride [phos-flur]). The groups treated with remineralizing agents were subjected to pH cycling over a period of 28 days. This was followed with assessment of surface microhardness (Micro Vickers Hardness tester, Matsuzawa Co., Ltd, Toshima, Japan).

STATISTICAL ANALYSIS

One-way analysis of variance test and posthoc Tukey test were conducted for multiple group comparison.

RESULTS

There was an improved enamel remineralization in the group, remineralized using CPP-ACPF in comparison with the other groups.

CONCLUSION

Casein phosphopeptide with fluoride is a promising material for remineralization of enamel subsurface lesions.