Self-curing Acrylic Resin Research Articles

Comparison of Friction Resistance Between Different Bracket Systems: An In Vitro Study

Introduction The efficiency of tooth movement associated with orthodontic sliding mechanics can be compromised by friction between archwire and tube or bracket slot. Orthodontic brackets and archwires are important constituents of an orthodontic appliance system. Friction is an uncontrolled variable of particular interest when continuous arch techniques are used to align and move teeth by way of sliding a tube or bracket along an arch. Aim and Objectives Comparison of frictional resistance between different bracket systems of 3M and MO brands in combination with different wires of 3M, MO, and G&H brands. Evaluation of frictional resistance between two different types of bracket systems and different types of wire combinations. Materials and Methods Two types of bracket systems were used: metal bracket system and ceramic bracket system (3M and MO brands). Four different orthodontic wire alloys were used: stainless steel (SS), TMA, NiTi, and CuNiTi (3M, MO, and G&H brands). A rectangular block made up of self-cure acrylic resin was designed to hold the bracket during the mechanical test. Each bracket base was glued to an acrylic block with cyanoacrylate glue. The wire segment was inserted into the bracket and was ligated passively with SS ligature wire. The bracket–wire combination was submitted to mechanical tests with a universal testing machine. One end of the acrylic block was mounted to the lower grip of the universal testing machine. The free end of the archwire was fixed to the upper grip of the universal testing machine. The friction which was generated between the wire and bracket was measured under dry conditions and at room temperature. The test wire was pulled through the bracket at a speed of 0.5 cm/min. The load cell registered a maximum force level. This data was stored in the computer and was submitted to statistical analysis, and parameter tests were applied. Results The highest mean friction resistance of 5.998 N was generated by group B2-E2 (ceramic bracket – MO + TMA archwire – MO). The lowest mean friction resistance of 2.552 N was generated by group A1-C1 (metal bracket – 3M + SS wire – 3M). There was a statistically significant difference between the friction generated by the metal bracket on SS archwire and the ceramic bracket on TMA archwire regardless of 3M or MO brand material ( p value < .0001) and metal bracket ( p = .0004).

A comparative evaluation of human enamel remineralization ability of biomimetic nacre against casein phosphopeptide-amorphous calcium phosphate: An in vitro study.

This study aimed to assess and compare the efficacy of Nacre and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on the remineralization of enamel using surface microhardness analysis, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy. Twenty human maxillary premolars extracted for orthodontic reasons were collected. Under cool water spray, the crowns were sectioned mesiodistally into buccal and palatal halves using a diamond disc. The samples were subsequently mounted in self-cure acrylic resin. The samples were then subjected to Vickers hardness testing and SEM-EDX for baseline. To simulate carious lesions, all of the samples were acid-etched with 37% phosphoric acid for 30 s in a specific area on the enamel samples and subjected to surface microhardness testing and SEM-EDX. The enamel samples were randomly assigned to Group 1: Nacre water-soluble matrix (WSM), Group 2: Nacre varnish, and Group 3: CPP-ACP for remineralization. After 21 days, remineralization assessment of the test samples was done using SMH analysis and SEM-EDX analysis. Data obtained were statistically analyzed using the one-way analysis of variance to reveal the significant differences between the groups. Tukey's test was used for post hoc comparisons. All three groups showed a significant increase in surface microhardness. All three groups showed a significant calcium and phosphorous ratio increase after remineralization. Among the three groups, the highest Ca:P ratio was seen in the Nacre WSM group (0.58) followed by the Nacre Varnish (0.57) and CPP-ACP group (0.57). SEM images of the Nacre surface revealed the presence of extensive interlocking. A layer of packed hydroxyapatite particles was formed on the surface of the nacre through surface reactions. All the groups in the present study showed some extent of remineralizing ability irrespective of the different materials and mechanisms of action. Nacre WSM showed a remarkable hardness spike close to natural enamel after demineralization.

Effect of hydrogen peroxide versus charcoal-based whitening mouthwashes on color, surface roughness, and color stability of enamel

BackgroundPatients tend to favor the whitening mouthwashes as they are easily applied and affordable. This study aimed to evaluate the effect of hydrogen peroxide versus charcoal-based whitening mouthwashes on color, surface roughness, and color stability of enamel. In the current study, the whitening mouthwashes used have the ability to stop future stains due to their white seal technology.MethodsA total of 21 permanent central incisor teeth extracted for periodontal reasons were used in the present study. Teeth roots were sectioned and crowns were mounted in self-cured acrylic resin blocks. The specimens were randomly divided into three groups (n = 7) according to the tested whitening mouthwash: Control group ‟ DW” (Distilled water), ‟OW” group: Peroxide-based mouthwash (Colgate Optic White) and ‟CP” group: Charcoal-based mouthwash (Colgate® Plax Charcoal). Regarding ‟OW” and ‟CP” groups, the specimens were immersed in 20 ml of the tested mouthwash in each corresponding group for 1 min twice daily (morning and evening) for a total of 12 uninterrupted weeks. Color change was assessed using VITA Easyshade spectrophotometer and surface roughness (Ra) was measured using a white light interferometer. The specimens were stained using black tea solution and color was measured after 24 h of immersion for assessment of color stability.ResultsColor change results revealed that both whitening mouthwashes were able to restore color comparable to the control group with no significant difference between them. Regarding surface roughness, the control group showed the highest mean Ra value, followed by ‟OW” group while ‟CP” group showed the lowest mean Ra value. While color stability after staining, the control group showed a significantly higher value than the ‟CP” and ‟OW” groups.ConclusionHydrogen peroxide and charcoal-based whitening mouthwashes improve the color of enamel with no adverse effect on the surface roughness. Both whitening mouthwashes were beneficial to maintain the color after staining and prevent future enamel stains.

Comparative Evaluation of Microbial Adhesion on Provisional Crowns Fabricated With Milled Polymethyl Methacrylate (PMMA) and Conventional Acrylic Resin: A Prospective Clinical Trial.

Introduction Provisional prosthetic restorations play a crucial role in dentistry by protecting dentinal tubules, offering thermal insulation, and ensuring a precise fit during dental treatments. Computer-aided design and computer-aided manufacturing (CAD/CAM) have improved polymethyl methacrylate (PMMA), enhancing its mechanical properties such as hardness and resistance compared to traditional methods. However, bacterial accumulation remains a challenge due to inherent surface roughness. This study aims to assess and compare Streptococcus mutans adhesion on milled PMMA and conventional self-cure acrylic resin, providing insights into their microbial interaction dynamics. Materials and methods This study was a prospective trial approved by the Institutional Human Ethical Committee (SRB-IHEC) (registration number: IHEC/SDC/PROSTHO-2104/24/045) and registered in the Clinical Trial Registry, India (registration number: CTRI/2024/05/068196). The study involved 20 patients requiring single crowns in the right and left molar regions. Two groups were established: Group I (the milled PMMA group) and Group II (the conventional PMMA group). Criteria for participant selection and exclusion were set. A total of 120 swab samples from the buccal mucosa and tooth surfaces were collected before tooth preparation (the baseline) at one week and three weeks. Culture for S. mutans was done, and colony-forming units were counted. Data analysis was carried out using IBM SPSS Statistics for Windows, Version 26 (Released 2019; IBM Corp., Armonk, New York, United States). An independent sample t-test was employed to compare the two materials for crowns. To analyze changes over time within each group, a repeated-measures analysis of variance (ANOVA) was conducted. When the ANOVA test indicated significance, Tukey's post-hoc test was utilized for pairwise mean comparison. The level of significance was set at P < 0.05. Results The mean colony-forming units (CFU) counts for the milled PMMA group were 4.46 ± 0.167 CFU at baseline, 4.163 ± 0.058 CFU at one week, and 3.87 ± 0.19 CFU at three weeks. The mean CFU counts for the conventional PMMA group were 4.41 ± 0.13 CFU at baseline, 4.29 ± 0.114 CFU at one week, and 4.16 ± 0.108 CFU at three weeks. At baseline (before cementation), there was no difference between milled PMMA and conventional PMMA (P = 0.578). After one week, a significant difference between milled PMMA and conventional PMMA was observed (P < 0.005). After three weeks, a significant difference between milled PMMA and conventional PMMA persisted (P < 0.005). Conclusion There was a significant reduction in microbial adhesion in both the milled and conventional PMMA groups. However, milled PMMA demonstrated a greater decrease in microbial adhesion as compared to conventional PMMA.

Effect of polymerization methods on surface roughness and hardness of commercially available self-curing acrylic resins: a comparative study

Purpose This paper aims to compare the surface roughness and hardness of three commercially available self-curing acrylic resins for dental use, under different polymerization conditions. Design/methodology/approach A comparative in vitro study was conducted using a convenience sample of 12 × 5 × 2 mm blocks with n = 40 for each material (Nic Tone, Arias Plus and Orthocryl®), with subgroups according to the polymerization method: conventional (C) and polymerization under ambient conditions (A). The surface roughness of the materials was measured using a profilometer; hardness was measured with a portable hardness tester. Additionally, surface morphology as well as particles size and morphology were evaluated with scanning electron microscopy. Findings There were significant differences in roughness and hardness values between the three self-curing acrylic resins (p &lt; 0.05), as well as within each self-curing acrylic resin according to the polymerization method used (p &lt; 0.05). The samples polymerized with the conventional method presented lower surface roughness and hardness values. Originality/value This study provides scientific evidence of values not provided by manufacturers in relation to the surface roughness and hardness of these materials, and all of them met the ideal minimum values of surface roughness, regardless of the polymerization technique used.

Effect of Dietary Simulating Solvents on the CAD-CAM Provisional Restorative Materials' Microhardness and Color Stability Properties: An in vitro Study.

This in vitro study investigated the effects of dietary solvents on the microhardness and color stability of CAD/CAM provisional restorations compared to conventional materials. Disc-shaped specimens (n=200) were fabricated from self-cured acrylic resin, two 3D-printing resins (FormLabs, NextDent), and a milled material (TelioCAD). Randomization assigned specimens (n=10/group) to immersion solutions: artificial saliva, citric acid, heptane, coffee, and tea. Microhardness and color stability were evaluated. One-way and three-way ANOVA with Tukey's post hoc test analyzed the data. Dietary solvents significantly reduced the surface microhardness of all tested materials (p<0.05). Unpolished surfaces exhibited greater color changes compared to polished ones (p<0.05) across all materials. Coffee and tea induced the most substantial reductions in hardness and the most significant color alterations (p<0.05), whereas saliva and citric acid had minimal effects. Milled provisional restorations exhibited superior hardness and color stability. Dietary solvents significantly affected material properties over time, highlighting the importance of material selection for clinical applications.

In Vitro Evaluation Of The Effect Of Different Cleansing Agents On The Shear Bond Of Contaminated Zirconia Ceramics To Resin Cement

Aim: The aim of this in-vitro study was to evaluate the effect of different cleansing solutions on the shear bond strength of contaminated zirconia ceramic to resin cement. Materials and Methods: Fifty zirconia disc (Dental Direkt,YES Germany) of size 10mm x 3mm were fabricated and mounted in self-cure acrylic resin block using a customized jig. The samples (n=10) were grouped based on two cleansing solutions and sub grouped based on two contaminants. Group I (control), neither contaminated nor any cleansing solution used. Group IIA, contaminating with saliva, cleansed with water and Group IIB, contaminating with GC Fitchecker II, cleansed with water. Group IIIA, contaminating with saliva, cleansed with Zirclean and Group IIIB, contaminating with GC Fitchecker II, cleansed with Zirclean. Subsequently fifty composite buttons (5.5mm x 3mm) were fabricated and bonded to the test samples using resin modified glass ionomer cement (Riva Cem,SDI). Thermocycling, shear bond strength, scanning electron microscopy were carried out for all the groups. Statistical analysis was done using independent t test with SPSS software Results: On comparison it was found that samples contaminated with saliva, cleansed with Zirclean showed a higher mean shear bond strength and the result was statistically significant (P&lt;0.001). Samples contaminated with GC Fitchecker, cleansed with Zirclean showed a higher mean shear bond strength and the result was statistically significant (P&lt;0.001). The result collaborated with SEM analysis of the debonded samples. Conclusion: Zirclean can be used as an effective surface cleansing solution for zirconia restorations.

Adaptability of VisCalor versus bulk-fill composites using scanning electron microscope: an in-vitro study

Purpose To evaluate the marginal integrity of two types of bulk-fill composite resins in Class I box-shaped cavities. Materials and methods Forty extracted human sound molars were selected. The teeth were fixed with sticky wax to the base of plastic cylinder and the cylinder was filled with self-curing acrylic resin so that only root was embedded. Simple Class I box-shaped cavities were prepared using a fissure carbide bur with water spray and finished with fine-grained flame burs. The overall dimensions and depth of the cavities were standardized as follows: 4 mm length mesiodistally and 3 mm width buccolingually and up to 4 mm depth. All prepared cavities were bonded using Futurabond M+ one-step self-etch adhesive system. The teeth were randomly divided into two groups (n = 20 teeth each): group I: specimens were restored with VisCalor composite bulk-fill composite resin, which is heated before insertion using a VisCalor dispenser dental device. Group II: specimens were directly restored with X-tra fill bulk-fill composite resin without preheating. After curing, finishing and polishing were performed. Each group was subdivided into two subgroups a and b (n = 10) according to whether subjecting 500 thermocycling fluctuations or not. Each specimen was sectioned buccolingually through the center of the composite resin restoration in two halves, and then cleaned under running tap water and subjected to thorough ultrasonic cleaning to get rid of both soft and hard surface deposits. All sectional samples were fixated in cylindrical carriers, and a thin layer of gold was applied to the surfaces. The marginal adaptation of composite restorations and ultramorphology of adhesive bonds were analyzed at ×50, ×1000 magnification, with a scanning electron microscope. ×50 magnification was utilized to measure the length of margins free gap in enamel and dentin by Autodesk Auto CAD program and expressed in mm/percent. All data of measurements of the length of nongaped margins in enamel and dentin are collected, tabulated, and statistically analyzed. Results Group Ia (VisCalor bulk-fill not thermocycled), recorded the highest mean value of marginal free-gap with 10.26 ± 0.27 mm (93.31%), while group IIb (X-tra-fill bulk-fill thermocycled) recorded the lowest mean value in 7.90 ± 0.26 mm (73.04%) and the difference was statistically highly significant (P = 0.000). In general, group I recorded higher mean values of marginal free gap and adaptation in mm/percent than group II, and the difference was statistically highly significant at P value of 0.000 (9.86 ± 0.55 and 8.23 ± 0.39 mm and 89.15 ± 5.38 and 74.89 ± 3.69%, respectively). Bulk-fill restorations without thermocycling exhibited a higher mean value of marginal free gap and adaptation in mm/percent than the thermocycled one with a significant difference recorded at P value of 0.005. Conclusion Using preheated VisCalor bulk-fill composites could decrease the marginal gap formation improving the continuity at the tooth–restorative material interface than conventional bulk-fill restorations. On the other hand, thermocycling.

Comparative Evaluation of Candida Albicans Adherence, Flexural strength and Water Sorption of Orthodontic Self-Cure Acrylic Resin Modified with 2-Methacryloyloxyethyl Phosphorylcholine by Two Different Techniques: in-vitro Study

Comparative Evaluation of Candida Albicans Adherence, Flexural strength and Water Sorption of Orthodontic Self-Cure Acrylic Resin Modified with 2-Methacryloyloxyethyl Phosphorylcholine by Two Different Techniques: in-vitro Study

Comparative evaluation of the dimensional accuracy of two commercially available extended pour alginates and a conventional alginate impression material at various time intervals – An in vitro study

Because of its acceptable accuracy, affordable price, accessible availability, and simplicity of handling, alginate impression materials continue to be a crucial component of dental practice despite many developments.The purpose of this study was to evaluate and compare the dimensional accuracy of two commercially available extended pour alginates (Cavex ColorChange and Algeniux) and a conventional alginate impression material (Zelgan) at different time intervals. On a maxillary model (Columbia Dentoform, Long Island City, N.Y.) the canines and the first molars were replaced with metal dies. This was selected as the master model. A ‘+’ mark was inscribed on these metal dies to serve as a reference for measurements. A self-cure acrylic resin custom tray was fabricated such that it was positioned over the model in the same spatial relationship with equal amount of space between the tray and model every time an impression was made. A total of 180 impressions were made of the master model, 15 impressions with each material at four different time intervals; immediate, 30 minutes, 48 hours (2 days) and 120 hours (5 days) to obtain gypsum cast. Manufacturer recommended water/powder ratios and storage conditions were followed in the process. Following the designated storage time interval, the casts were poured in minimum expansion Type IV dental stone. Measurements were done with a coordinate measuring machine after 7 days when the casts were completely dry. To evaluate and compare the dimensional accuracy of materials across various time points, for each group, the mean and standard deviation were estimated and subjected to statistical analysis. Two Way Repeated Measure Analysis of Variance (ANOVA) was performed to determine if the dimensions differed significantly across groups with time. The pair wise analysis for materials and time points was performed using Tukey’s post-hoc test. The p value was taken as significant when less than 0.05.Across different time points, a minimum % change was observed at immediate time point, which gradually increased at 30 minutes and at 48 hour, but at 120 hour the % change was maximum for all dimensions. Among three groups, Cavex ColorChange material showed minimum % change across time points, whereas Zelgan group showed maximum % change across all dimensions. All the paired differences were statistically insignificant (p &amp;#62; 0.05) for Algeniux and Cavex ColorChange group. But for Zelgan group, the difference between all the pairs of time points were statistically significant (p &amp;#60; 0.05), except for the pair immediate vs. 30 minutes. These results suggest that Zelgan material showed significant changes after 30 min for all the dimensions.: The results revealed that both the extended pour alginates Cavex ColorChange and Algeniux produced dimensionally accurate casts at all time intervals while the conventional alginate, Zelgan was accurate only at immediate and 30-minute time interval. It was also observed that, among the 4-time intervals investigated, most accurate casts were obtained when the impressions were poured immediately.

Cytotoxicity Evaluation of Various Composite Resin Materials: An In Vitro Study.

Aim This study aimed to determine and comparethe cytotoxicity of light-cured composite resin (Enlight light cure composite (Ormco, Glendora, California, USA)), light-cured acrylic resin (Orthocryl LC (Dentaurum, Ispringen, Germany)), and the self-cure acrylic (DPI RR cold cure acrylic (Dental Products of India, Bombay Burmah Trading Corporation Ltd., Mumbai, India)) material and to determine which component is best to be used for the purpose of nasal stent fabrication in the nasoalveolar molding (NAM) technique for cleft therapy. Methods Circular discs made from Enlight light cure composite, Orthocryl LC, and self-cure acrylic were submerged for 24 hours in gingival fibroblast media (three discs of each material) and control medium (three discs of each material) that were both contained in plates. After analyzing the optical densities of the plates, the cytotoxicity of the products was assessed by measuring cell viability using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The compiled data was analyzed using IBM SPSS Statistics for Windows, V. 23.0 (IBM Corp., Armonk, NY). The normality of the data was evaluated using the Shapiro-Wilk test.One-way analysis of variance (ANOVA) and pairwise comparison made with Tukey's honestly significant difference (HSD) post hoc test with a significance level (p) of 0.05 were considered. Results The percentage of cell viability was between 80% and 150%. A significantmean difference was noted in the cell viability between the three groups (p=0.009). High mean cell viability was seen in Orthocryl LC. However, there was no significant mean difference between Orthocryl LC and Enlight light cure composite material (p=0.854). Conclusion Both Orthocryl LC and Enlight light cure composite materials are less cytotoxic when compared to the self-cure acrylic resin material and can be used to fabricate the nasal stent component for infants with cleft defects, undergoing NAM procedure.

Comparative Evaluation of Shear Bond Strength of Resin-modified Glass Ionomer Cement with ProRoot MTA and MTA Angelus.

The aim of the present study was to evaluate the shear bond strength of resin-modified glass ionomer cement with two different types of mineral trioxide aggregate at different time intervals. A total of 80 cylindrical blocks were prepared using a self-cure acrylic resin with a central cavity of 4 mm internal diameter and 2 mm height. The prepared samples were randomly divided into two groups (n = 40 each) according to the type of MTA cements used (ProRoot MTA and MTA Angelus). Two groups were further sub-divided into four sub-groups of 10 samples each according to the different time intervals. ProRoot MTA and MTA Angelus were placed in the prepared cavity and a wet cotton pellet was placed over the filled cavity. A hollow plastic tube was placed over the MTA surface and resin-modified glass ionomer cement (RMGIC) was placed into the hollow plastic tube and light-cured (Spectrum 800, Dentsply Caulk Milford, DE, USA) according to the time intervals decided. After light curing the plastic tubes were removed carefully and the specimens were stored at 37°C and 100% humidity for 24 hours to encourage setting of MTA. The specimens were mounted in a universal testing machine (ADMET) and a crosshead speed of 0.5 mm/min was applied to each specimen by using a knife-edge blade until the bond between the MTA and RMGIC failed. The data were statistically analyzed using ANOVA, post hoc Tukey's t-test and Fisher's t-test and p-value ≤ 0.5 was considered significant. For both ProRoot MTA and MTA Angelus there was no statistically significant difference between 45 minutes and 24 hours (p-value ≥ 0.8). For ProRoot MTA, shear bond strength value at 10 minutes were significantly lower than 45 minutes and 24 hours group. However, for MTA Angelus, shear bond strength value at 10 minute was not significantly different from 45 minutes group (p-value ≥ 0.3). For both ProRoot MTA and MTA Angelus shear bond strength value at 0 minute were the least and were significantly lower than 10 minutes, 45 minutes, and 24 hours, respectively (p-value ≥ 0.000). Resin-modified glass ionomer cement can be layered over MTA Angelus after it is allowed to set for 10 minutes. However, ProRoot MTA should be allowed to set for at least 45 minutes before the placement of RMGIC to achieve better shear bond strength. Due to the variety of types of mineral trioxide aggregate cements available in dentistry, it is justifiable to emphasize on different time intervals as it may affect the shear bond strength of restorative cements. Such information is pivotal for the clinicians while using mineral aggregate-based cements that receive forces from the condensation of restorative materials or occlusion, as the compressive strength may be affected due to different time intervals. How to cite this article: Tyagi N, Chaman C, Anand S, et al. Comparative Evaluation of Shear Bond Strength of Resin-modified Glass Ionomer Cement with ProRoot MTA and MTA Angelus. J Contemp Dent Pract 2024;25(1):35-40.

Tea and Coffee Discoloration in the Simulated Remineralization Process of Tooth Structure: Investigating the Influence of In-Office Bleaching Material on Arrested Stains

This study aimed to investigate the efficacy of an in-office dental bleaching agent (with 40% H2O2) on the simulated stained remineralized lesions of teeth using tea and coffee as staining solutions. Forty-eight sound premolar teeth were selected, root amputated, and embedded in a self-curing acrylic resin. Half of the samples were immersed in a tea solution and the remaining half were immersed in a coffee solution for 4 days (n = 24). From each study group, half of the samples went through the bleaching process, and the remaining half served as a control. The color change was observed with a paired t-test and two-way ANOVA (α = 0.05). The ANOVA findings observed a significant effect on the ΔΕ value (p =&lt; .001) due to independent factors. Additionally, individual stages, i.e., time points such as baseline, demineralization, staining, re-mineralization, and bleaching had a significant effect on ΔΕ value (p =&lt;.001). The t-test results observed significant variations between ΔΕ values of bleached and not bleached groups after the staining and remineralization process, irrespective of the staining solution used. It’s crucial to abstain from coffee and tea during and shortly after bleaching until thorough remineralization therapy is completed.

Comparative evaluation of shear bond strength and modes of failure of five different reinforced glass ionomer restorative cements to TheraCal LC: An in vitro study.

The aim of the study is to evaluate and compare the shear bond strength (SBS) and modes of failure of different reinforced glass ionomer cement restorative materials such as GC IX, GC Gold Label 2 LC, Amalgomer CR, Equia Forte, and Secure Core Z to TheraCal LC. A total of 50 acrylic blocks, each containing a cylindrical hole in the center were prepared from self-cure acrylic resin and randomly divided into five groups and restored, namely Group A - TheraCal LC + GC Fuji IX, Group B - TheraCal LC + GC Gold Label 2 LC, Group C - TheraCal LC + Amalgomer CR, Group D - TheraCal LC + Equia Forte, and Group E - TheraCal LC + Secure Core Z. All the specimens were stored in artificial saliva at 37°C for 24 h before testing. The statistical tests used for the analysis of the result were: one-way ANOVA, Tukey multiple comparison test, and the Chi-squared test, and P < 0.05 is considered as the level of significance. Equia Forte showed the highest SBS, while GC type IX showed the lowest SBS with TheraCal LC. Equia Forte can be the restorative material of choice when TheraCal LC is used as a base materials for better clinical efficacy.

Evaluation of flexural strength, impact strength, and surface microhardness of self-cured acrylic resin reinforced with silver-doped carbon nanotubes

BackgroundPoly-methyl methacrylate (PMMA) is a type of polymer mostly used to make denture bases. Self-cured acrylic resin (PMMA) can be used to repair a fractured acrylic denture base; however, even after repair, this area remains vulnerable. Carbon nanotubes (CNTs) could be used as a filler for polymer reinforcement. Furthermore, silver nanoparticles are efficient agents for the prevention of dental biofilm and improving their mechanical properties. The doping of CNTs with silver nanoparticles may lead to a synergistic interaction that is predicted to enhance the mechanical characteristics of the fillers.ObjectivesThe aim of the study was to assess the influnce of manual incorporation of 0.5% weight percent (%wt.) of silver doped carbon nanotubes (Ag-doped CNTs) into commercial self-cured PMMA on its flexural strength, impact strength, and surface microhardness.MethodsIn this investigation, a total of 60 specimens comprised of acrylic resin were employed. They are divided into two main groups: (a) the control group, which was made by using liquid monomer and commercial self-cured PMMA powder; and (b) the modified group, prepared by hand mixing the purchased silver-doped CNTs powder (0.5% wt.) to self-cured PMMA powder (99.5%wt.), and then the blended powder was incorporated into the liquid monomer. Flexural strength, flexural modulus, impact strength, and surface microhardness were evaluated. Independent sample t-tests were used to statistically analyze the data and compare the mean values of flexural strength, flexural modulus, impact strength, and surface microhardness (p-value ≤ 0.05).ResultsThe flexural strength of the modified groups with Ag-doped CNTs (132.4 MPa) was significantly greater than that of the unmodified (control) groups (63.2 MPa). Moreover, the flexural modulus of the modified groups with Ag-doped CNTs (3.067 GPa) was significantly greater than that of the control groups (1.47 GPa). Furthermore, the impact strength of the modified groups with Ag-doped CNTs (11.2 kJ/mm2) was significantly greater than that of the control groups (2.3 kJ/mm2). Furthermore, the microhardness of the modified groups with Ag-doped CNTs (29.7 VHN) was significantly greater than that of the control groups (16.4 VHN), (p-value = 0.0001).ConclusionThe incorporation of 0.5% wt. silver doped CNTs fillers to the self-cured acrylic resin enhanced its flexural strength, flexural modulus, impact strength, and surface microhardness.

In vitro remineralization by various ion-releasing materials of artificially demineralized dentin: A micro-CT study

ObjectiveThe aim of this study was to evaluate the remineralizing properties of ion-releasing restorative materials on pH cycling-induced carious dentin. MethodsFifty sound molars were freshly extracted. The occlusal surfaces were abraded using water-cooled sandpaper (800 grit). The residual crowns were embedded in self-cured acrylic resin with the flat dentin surface exposed. A mesio-distal trench was created using a calibrated 0.5 mm deep occlusal reduction burr, and artificial dentin caries were generated by pH cycling. Then, teeth were randomly assigned to five groups according to the ion-releasing material used. For each sample, micro-CT acquisitions were performed at various intervals. Remineralization was assessed by mean gray value (MGV) measurements after registration and segmentation of the region of interest with 3D Slicer software. One-way repeated-measures ANOVA followed by Tukey’s post hoc test was used to investigate the difference in MGVs among the various groups. ResultsOnly Cention Forte showed significantly increased MGVs after 4 weeks compared to demineralized dentin. MGVs were higher, but not significantly, after placement of the restorative materials, including in the resin composite control group. These results can be explained by the radiopacity of the materials. SignificanceCention Forte, the material with the highest radiopacity, showed a significant increase in the MGVs of artificially carious dentin after 4 weeks. However, the study of dentin remineralization by micro-CT could be impacted by the radiopacity of the restorative materials used. The relevance of this examination for the study of dentinal remineralization should be investigated.

EVALUATION OF BOND STRENGTH BETWEEN DIFFERENT SYSTEMS FOR ADHESIVE CEMENTATION TO FELDSPATHIC PORCELAIN AND ZIRCONIUM OXIDE

Introduction: New systems for adhesive cementation have been increasingly developed and used in daily clinical practice for the cementation of ceramic prostheses. Differences in the chemical composition of various system components can influence the bond strength between the resin cement and the ceramic. Objective: This study aims to evaluate the bond strength between two ceramic systems—feldspathic porcelain and yttria-stabilized zirconium oxide—and three different systems for adhesive cementation: Rely X ARC, Multilink System, and Rely X UCem. Methodology: Thirty discs of Noritake feldspathic porcelain and thirty discs of zirconium oxide ceramic were fabricated, each measuring 7.5 mm in diameter by 3.0 mm in thickness, according to the manufacturers’ instructions. The discs were polished on a mechanical polisher with water sandpaper ranging from 320 to 1500 grit and embedded in ½ inch PVC tubes with self-curing acrylic resin. The feldspathic porcelain discs were conditioned with 10% hydrofluoric acid for 120 seconds, and the zirconium oxide discs were sandblasted with 40 psi alumina for 10 seconds at 10 mm. All discs were then washed and placed in an ultrasonic bath with distilled water for 10 minutes. The cementation systems were applied according to the manufacturers’ instructions (n=10) on an adhesion area of 5.0 mm in diameter, delimited by a tripartite metal matrix. The samples underwent 1,000 thermal cycles ranging from 5°C to 55°C. Shear bond strength tests were performed on an EMIC DL2000 testing machine with a 20 kN load cell and a speed of 0.5 mm/min. The mean values of the groups were as follows (in MPa): Feldspathic with Rely X ARC (G1) 6.21; Feldspathic with Multilink (G2) 8.98; Feldspathic with Rely X UCem (G3) 8.15; Zirconium Oxide with Rely X ARC (G4) 0.53; Zirconium Oxide with Multilink (G5) 9.25; Zirconium Oxide with Rely X UCem (G6) 4.37. Data were subjected to one-way ANOVA and Tukey tests. Results: There was no significant difference among the feldspathic porcelain groups. For zirconium oxide, Multilink showed higher bond strength values. Conclusion: The bond strength between the cements and feldspathic porcelain exceeded the intrinsic strength of this material, and Multilink showed the highest bond strength values regardless of the ceramic material.

Microbiological, physicomechanical, and surface evaluation of an experimental self-curing acrylic resin containing halloysite nanotubes doped with chlorhexidine

ObjectiveThe objective was to synthesize halloysite nanotubes loaded with chlorhexidine (HNT/CHX) and evaluate the antimicrobial activity, microhardness, color change, and surface characteristics of an experimental self-curing acrylic resin containing varying concentrations of the synthesized nanomaterial. MethodsThe characterization of HNT/CHX was carried out by calculating incorporation efficiency, morphological and compositional, chemical and thermal evaluations. SAR disks were made containing 0 %, 3 %, 5 %, and 10 % of HNT/CHX. Specimens (n = 3) were immersed in distilled water and spectral measurements were carried out using UV/Vis spectroscopy to evaluate the release of CHX for up to 50 days. The antimicrobial activity of the composite against Candida albicans and Streptococcus mutans was evaluated by disk-diffusion test. Microhardness, color analyses (ΔE), and surface roughness (Ra) (n = 9) were performed before and after 30 days of immersion. Data were analyzed using ANOVA/Bonferroni. {Results.} The incorporation efficiency of CHX into HNT was of 8.15 %. All test groups showed controlled and cumulative CHX release up to 30 or 50 days. Significant antimicrobial activity was verified against both microorganisms (p < 0.001). After the 30-day immersion period, the 10 % HNT/CHX group showed a significant increase in hardness (p < 0.05) and a progressive color change (p < 0.001). At T0, the 5 % and 10 % groups exhibited Ra values similar to the control group (p > 0.05), while at T30, all groups showed similar roughness values (p > 0.05). {Significance.}The modification of a SAR with HNT/CHX provides antimicrobial effect and controlled release of CHX, however, the immediate surface roughness in the 3 % group was compromised when compared to the control group.

Surface treatments for polyetheretherketone (Peek): Effects on the bond strength to a resin cement and on the fatigue performance of a bonded glass-ceramic

ObjectiveTo evaluate the effect of distinct surface treatments on Peek (polyetheretherketone) adhesion to the resin cement and the mechanical fatigue behavior of lithium disilicate adhesively bonded to it. Materials and methodsPeek slices embedded in plastic rings with self-curing acrylic resin were randomized into 4 groups for adhesion testing, considering the following surface treatment factors: Ctrl (just cleaned with 78 % isopropyl alcohol); Grinding (4219F diamond bur - 46 μm grain size); Air abrasion (45 μm aluminum oxide for 10 s); Sulfuric acid (acid etching for 30 s). All slices received a layer of adhesive agent; resin composite cylinder specimens (Ø = 3 mm; h = 3 mm) were produced and bonded onto the Peek slices using a dual resin cement for the shear bond strength tests (n = 20) through the wire-loop technique. Next, disc-shaped specimens of Peek (Ø = 10 mm; thickness: 2 mm) and lithium disilicate (LD) (Ø = 10 mm; thickness: 1 mm) were produced for the fatigue tests (n = 20) and paired. The LD was treated (5 % hydrofluoric acid for 20 s + silane agent) and adhesively bonded (with dual resin cement) onto Peek (treated with the previously mentioned surface treatments). The fatigue tests were performed with a step-stress approach (20 Hz; 10,000 cycles/step; initial load: 100 N; step-size: 50 N). Roughness, contact angle, topography and fractographic analysis were performed. The adhesive data was analyzed by one-way ANOVA and Tukey post-hoc tests, while the fatigue data were subjected to survival analysis (Kaplan Meier and Mantel-cox post hoc tests). ResultsOnly the air abrasion surface treatment was able to improve the bond strength between Peek and resin cement (p < 0.05); the Grinding and Sulfuric acid groups were similar to the Ctrl. All surface treatments promoted similar fatigue performance. ConclusionAir abrasion promoted increased bond strength between Peek and resin cement, having no detrimental effect on fatigue behavior. Overall, the mechanical behavior under fatigue of a lithium disilicate glass-ceramic was not influenced by the Peek substrate surface treatments.

Effect of khat extract on color stability of digitally and manually fabricated provisional restorations: an in vitro comparative study

BackgroundThe aim of this in vitro study was to evaluate the effect of khat extract on the color stability of five different provisional restorative materials (PRMs).MethodsIn this study, 50 specimens were fabricated from five different PRMs with different techniques. Twenty specimens were digitally fabricated of poly-methyl methacrylate (PMMA) CAD/CAM milling and 3D printing PRMs, while the other thirty specimens were manually fabricated of three different PRMs: PMMA self-cured (SC) acrylic resin, light-cured (LC) composite, and Bis-acrylic SC composite. Milling and 3D printing machines were used to fabricate the digital specimens, while the manual specimens were fabricated using a metallic mold. The material was placed in the mold, covered by a polyester stripe, and held between two glass slabs with a constant load for 30 s. After setting, the specimens were removed and checked. Ten disc-shaped specimens with 2 ± 0.3 mm thickness and 10 ± 0.3 mm diameter were prepared from each of the tested PRM. Then all the specimens were polished. Five specimens of each PRM were immersed in khat extract, while the other five were immersed in distilled water medium as a control group. The color measurements were recorded before and after 1 and 7 days of immersion using a spectrophotometer. The immersion media were renewed every 24 h and kept along with the specimens at 37 °C. The T test, paired T test, and ANOVA analysis of variance were used to analyze the results. The Bonferroni test was used for post-hoc multiple comparisons.ResultsThe interaction between the tested PRMs, the media, and the duration of immersion time was statistically significant (p < 0.05). PMMA CAD/CAM milling PRM was the most stable in color, and this was statistically significant (p < 0.05). The LC composite PRM composite was the least stable in color and was statistically insignificant (p > 0.05) when compared to the 3D printing and Bis-acrylic SC composite PRMs, respectively.ConclusionsThis study demonstrated that khat extract medium has a high staining ability on the tested PRMs. CAD/CAM milling PRM was the most stable in color and could therefore be used as a long-term provisional. The increase in immersion time was a significant factor in the color change of the tested PRMs. The color of the 3D-printed PRM was the most affected over time.