Resin-based Dental Materials Research Articles

Development of Light-Polymerized Dental Composite Resin Reinforced with Electrospun Polyamide Layers.

As the mechanical properties of resin-based dental composite materials are highly relevant in clinical practice, diverse strategies for their potential enhancement have been proposed in the extant literature, aiming to facilitate their reliable use in dental medicine. In this context, the focus is primarily given to the mechanical properties with the greatest influence on clinical success, i.e., the longevity of the filling in the patient's mouth and its ability to withstand very strong masticatory forces. Guided by these objectives, the goal of the present study was to ascertain whether the reinforcement of dental composite resins with electrospun polyamide (PA) nanofibers would improve the mechanical strength of dental restoration materials. For this purpose, light-cure dental composite resins were interspersed with one and two layers comprising PA nanofibers in order to investigate the influence of such reinforcement on the mechanical properties of the resulting hybrid resins. One set of the obtained samples was investigated as prepared, while another set was immersed in artificial saliva for 14 days and was subsequently subjected to the same set of analyses, namely Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Findings yielded by the FTIR analysis confirmed the structure of the produced dental composite resin material. They also provided evidence that, while the presence of PA nanofibers did not influence the curing process, it strengthened the dental composite resin. Moreover, flexural strength measurements revealed that the inclusion of a 16 μm-thick PA nanolayer enabled the dental composite resin to withstand a load of 3.2 MPa. These findings were supported by the SEM results, which further indicated that immersing the resin in saline solution resulted in a more compact composite material structure. Finally, DSC results indicated that as-prepared as well as saline-treated reinforced samples had a lower glass transition temperature (Tg) compared to pure resin. Specifically, while pure resin had a Tg of 61.6 °C, each additional PA nanolayer decreased the Tg by about 2 °C, while the further reduction was obtained when samples were immersed in saline for 14 days. These results show that electrospinning is a facile method for producing different nanofibers that can be incorporated into resin-based dental composite materials to modify their mechanical properties. Moreover, while their inclusion strengthens the resin-based dental composite materials, it does not affect the course and outcome of the polymerization reaction, which is an important factor for their use in clinical practice.

Adhesion of Conventional, 3D-Printed and Milled Artificial Teeth to Resin Substrates for Complete Dentures: A Narrative Review.

One type of failure in complete or partial dentures is the detachment of resin teeth from denture base resin (DBR). This common complication is also observed in the new generation of digitally fabricated dentures. The purpose of this review was to provide an update on the adhesion of artificial teeth to denture resin substrates fabricated by conventional and digital methods. A search strategy was applied to retrieve relevant studies in PubMed and Scopus. Chemical (monomers, ethyl acetone, conditioning liquids, adhesive agents, etc.) and mechanical (grinding, laser, sandblasting, etc.) treatments are commonly used by technicians to improve denture teeth retention with controversial benefits. Better performance in conventional dentures is realized for certain combinations of DBR materials and denture teeth after mechanical or chemical treatment. The incompatibility of certain materials and lack of copolymerization are the main reasons for failure. Due to the emerging field of new techniques for denture fabrication, different materials have been developed, and further research is needed to elaborate the best combination of teeth and DBRs. Lower bond strength and suboptimal failure modes have been related to 3D-printed combinations of teeth and DBRs, while milled and conventional combinations seem to be a safer choice until further improvements in printing technologies are developed.

Influence of Fabrication Technique on Adhesion and Biofilm Formation of Candida albicans to Conventional, Milled, and 3D-Printed Denture Base Resin Materials: A Comparative In Vitro Study.

The aim of this study was to evaluate the adhesion and biofilm formation of Candida albicans (C. albicans) on conventionally fabricated, milled, and 3D-printed denture base resin materials in order to determine the susceptibility of denture contamination during clinical use. Specimens were incubated with C. albicans (ATCC 10231) for 1 and 24 h. Adhesion and biofilm formation of C. albicans were assessed using the field emission scanning electron microscopy (FESEM). The XTT (2,3-(2-methoxy-4-nitro-5-sulphophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide) assay was used for the quantification of fungal adhesion and biofilm formation. The data were analyzed using GraphPad Prism 8.02 for windows. One-way ANOVA with Tukey's post hoc testing were performed with a statistical significance level set at α = 0.05. The quantitative XTT biofilm assay revealed significant differences in the biofilm formation of C. albicans between the three groups in the 24 h incubation period. The highest proportion of biofilm formation was observed in the 3D-printed group, followed by the conventional group, while the lowest candida biofilm formation was observed in the milled group. The difference in biofilm formation among the three tested dentures was statistically significant (p < 0.001). The manufacturing technique has an influence on the surface topography and microbiological properties of the fabricated denture base resin material. Additive 3D-printing technology results in increased candida adhesion and the roughest surface topography of maxillary resin denture base as compared to conventional flask compression and CAD/CAM milling techniques. In a clinical setting, patients wearing additively manufactured maxillary complete dentures are thus more susceptible to the development of candida-associated denture stomatitis and accordingly, strict oral hygiene measures and maintenance programs should be emphasized to patients.

In Vitro Mechanical Properties of a Novel Graphene-Reinforced PMMA-Based Dental Restorative Material.

Recent studies suggest that the incorporation of graphene in resin-based dental materials might enhance their mechanical properties and even decrease their degree of contraction during polymerization. The present study aimed at comparing the three-point flexural strength (FS), the compressive strength (CS), and the Vickers hardness (VH) of a CAD/CAM poly-methylmethacrylate (PMMA)-based resin, a recently introduced graphene-reinforced CAD/CAM PMMA-based resin (G-PMMA), and a conventional dental bis-acryl composite resin (BACR). No significant differences (p > 0.05) were detected among the materials in terms of flexural strength. On the other hand, a mean flexural modulus value of 9920.1 MPa was recorded in BACR group, significantly higher compared to the flexural modulus detected for G-PMMA (2670.2 MPa) and for conventional PMMA (2505.3) (p < 0.05). In terms of compressive modulus (MPa) and compressive strength (MPa), BACR was significantly stiffer than PMMA and G-PMMA. Concerning VH measurements, a significantly increased hardness emerged comparing the BACR group (VH 98.19) to both PMMA and G-PMMA groups (VH 34.16 and 34.26, respectively). Based on the finding of the present study, the graphene-reinforced (PMMA)-based polymer herein tested was not superior to the conventional PMMA and seemed not able to be considered as an alternative material for permanent restorations, at least in terms of hardness and mechanical response to compressive stress. More research on the mechanical/biological properties of G-PMMAs (and on graphene as a filler) seems still necessary to better clarify their potential as dental restorative materials.

Effect of topical fluoride applications on residual monomer release from resin-based restorative materials

BackgroundThe effects of topical fluoride applications on the release of monomer ingredients from resin-based dental materials by immersion in various extraction solutions are unclear. The aim of this study was to determine the effect of topical fluorides (APF and NaF) on the elution of residual monomers (Bis-GMA, TEGDMA, UDMA, and HEMA) from resin-based materials.MethodsNinety specimens were prepared, 30 bulk-fill composite resin, 30 nanohybrid universal composite resin, and 30 polyacid-modified composite resin (compomer). These were randomly divided into three groups based on fluoride application procedures. Each specimen was kept in 75% ethanol solution, and residual monomers released from materials were analyzed using high-performance liquid chromatography (HPLC) after 10 min, 1 h, 24 h, and 30 days. The groups were compared using the Mann Whitney U and Kruskal Wallis tests. Measurements were analyzed using the Friedman and Wilcoxon signed-rank tests.ResultsFluoride applications generally had no considerable effect on the amount of residual monomer released from resin-based restorative materials. The amount of monomer release after topical APF application was similar to the release in the control group and was lower than the release in the NaF group. The release of monomers from the resin-based material used in the study did not approach toxic levels at the applied time intervals. The compomer released lower amounts of monomer than other resin-based materials.ConclusionsFluoride applications do not increase monomer release from resin-based restorative materials. However, compomers should be employed by clinicians due to their lower monomer release compared to other resin restorative materials. The release of monomers from all the resin-based materials did not approach toxic levels at the applied time intervals.

Prospects on Tuning Bioactive and Antimicrobial Denture Base Resin Materials: A Narrative Review.

Denture base resin (DBR) materials are used in dentistry in constructing removable dentures and implant-supported prostheses. A plethora of evidence has demonstrated that DBR materials are associated with a high risk of denture stomatitis, a clinical complication where the soft oral tissues underneath the resin-based material are inflamed. The prevalence of denture stomatitis among denture wearers is high worldwide. Plaque accumulation and the infiltration of oral microbes into DBRs are among the main risk factors for denture stomatitis. The attachment of fungal species, mainly Candida albicans, to DBRs can irritate the underneath soft tissues, leading to the onset of the disease. As a result, several attempts were achieved to functionalize antimicrobial compounds and particles into DBRs to prevent microbial attachment. This review article explored the advanced approaches in designing bioactive and antimicrobial DBR materials. It was reported that using monomer mixtures, quaternary ammonium compounds (QACs), and organic and inorganic particles can suppress the growth of denture stomatitis-related pathogens. This paper also highlighted the importance of characterizing bioactive DBRs to be mechanically and physically sustainable. Future directions may implement a clinical translational model to attempt these materials inside the oral cavity.

Water sorption, water solubility, degree of conversion, elastic indentation modulus, edge chipping resistance and flexural strength of 3D-printed denture base resins

ObjectivesTo investigate the water sorption (wsp), water solubility (wsl), degree of conversion (DC), elastic indentation modulus (EIT), edge chipping resistance (ECR) and flexural strength (FS) of 3D-printed, milled and conventionally polymerized denture base resin materials. MethodsSpecimens (N = 540) were 3D-printed (NextDent Denture 3D+ (DEN), Fotodent Denture (FOT), Freeprint Denture (FRE), V-Print dentbase (VPR)), cut (Ivotion Base (IVO)) and molded (PalaXpress (PAL)) in three geometries. Wsp,wsl,DC, EIT, ECR and FS were tested initially (24 h, 37 °C, H20) and after additional aging (5000 thermal cycles, 5/55 °C). Data were analyzed with Kolmogorov-Smirnov, univariate ANOVA, Kruskal-Wallis, Mann-Whitney U test and Spearman's correlation (p < 0.05) ResultsMost 3D-printed denture base resins showed higher wsp (25.31–37.94 μg/mm3) and wsl (0.08–8.27 μg/mm3), but also higher EIT (3.11–4.09 GPa) and FS (60.81–99.57N/mm2) values than the control groups. DEN and VPR showed high DC (89.36–93.53%), EIT (3.77–4.09 GPa) and FS (79.65–99.57N/mm2), while FOT showed low wsp (25.31–27.35 μg/mm3) and wsl (1.01–3.87 μg/mm3) values. In all materials, the examined parameters were affected by aging. SignificanceAlthough 3D-printed denture base resins showed promising results with regard to the observed DC and FS, only FOT and FRE surpassed the threshold values defined by the ISO norms.

Impact of curcumin loading on the physicochemical, mechanical and antimicrobial properties of a methacrylate-based experimental dental resin

Oral biofilms are directly linked to one of the most common chronic human diseases, dental caries. Resin-based dental materials have significant potential to replace amalgam, however they lack sufficient antimicrobial power. This innovative study investigates a curcumin-loaded dental resin which can be utilized in an antimicrobial photodynamic therapy (aPDT) approach. The study evaluated the effects of curcumin loading on resin physicochemical, mechanical, and adhesive properties, as well as the antimicrobial response associated with blue light activation. Preliminary tests involving degree of conversion (DC) and sample integrity determined the optimal loading of curcumin to be restricted to 0.05 and 0.10 wt%. These optimal loadings were tested for flexural strength (FS), water sorption (WS) and solubility (SL), shear bond strength to dentin (SBS), and viability of Streptococcus mutans under 14.6 J/cm2 blue light or dark conditions, in 6 h and 24 h biofilms. The results demonstrated that 0.10 wt% curcumin had minimal impact on either FS or SBS, but detectably increased WS and SL. A 2 log10 (CFU/mL) reduction in S. mutans after light application in both 6 h and 24 h biofilms were corroborated by CLSM imaging and highlighted the significant potential of this novel aPDT approach with resin-based dental materials.

Silver-loaded mesoporous silica nanoparticles enhanced the mechanical and antimicrobial properties of 3D printed denture base resin

The aim of this study is to develop a novel 3D printed denture base resin material modified with mesoporous silica nanocarrier loaded with silver (Ag/MSN) to enhance mechanical and antimicrobial properties. Acrylate resin-based was incorporated with various proportion of Ag/MSN (0.0–2.0 wt%). Specimens with different geometry were printed and characterized accordingly for the effect of modification on properties such as: mechanical and physical properties, chemical composition and degree of conversion, as well as biological response in term of biocompatibility and antimicrobial against oral fibroblast and candida biofilm (C. albicans), respectively. The consecutive addition of Ag/MSN improved significantly surface hardness and crack propagation resistance, while flexural strength remained similar to control; however, a negligible decrease was observed with higher concentrations ≥1 wt%. No significant difference was noticed with water sorption, while water solubility had a remarkable trend of reduction associated with filler content. The surface roughness significantly increased when concentration of Ag/MSN was ≥1.0 wt%. A significant reduction in C. albicans biofilm mass, as the inhibition proficiency was correlated with the proportion of the filler. With respect to the amount of Ag/MSN, the modification was compatible toward fibroblast cells. The sequential addition of Ag/MSN enhanced significantly the mechanical and antimicrobial properties of the 3D printed resin-based material without affecting adversely compatibility. The acrylic resin denture base material has susceptibility of microbial adhesion which limits its application. Silver loaded MSN showed a significant performance to enhance antimicrobial activity against C. albicans which is the main cause of denture stomatitis. The proposed invention is a promise technique for clinical application to provide an advanced prosthesis fabrication and serve as long-term drug delivery.

Evaluation of the Impact of Different Disinfectants on Color Stability of Denture Base Materials: A Comparative Study

Aim of the current research was to assess the effect of different disinfectant solutions on the color steadiness of denture base materials. Ninety samples were made employing the Meliodent and ProBase Hot heat cure denture base resin materials. Metallic disks measuring 3 mm thick as well as 20 mm in diameter were utilized to make the samples. Forty-five samples of every denture base material were immersed in three chemical disinfectants: 2% alkaline glutaraldehyde, 0.5% chlorhexidine gluconate, 0.5% sodium hypochlorite solution as well as distilled water that served as a control. Color scoring was performed at baseline and following first, 14th as well as 21 days. Color was calculated as per CIE L*a*b* color scale as related to standard source C alongside a white background on a reflection spectrophotometer. Subsequent to the immersion of Meliodent heat-cured denture base resin materials within distilled water, the baseline color steadiness score was 6.16 ± 0.12, 6.12 ± 0.08 on the first day, 5.98 ± 0.06 on day 14 and 5.74 ± 0.14 on day 21. Within 2% alkaline glutaraldehyde the baseline color constancy mean value was 6.12 ± 0.28, 6.08 ± 0.04 on the first day, 5.04 ± 0.11 on day 14 and 4.22 ± 0.14 on day 21. Within 0.5% chlorhexidine gluconate the baseline color constancy mean value was 6.14 ± 0.09, 6.02 ± 0.12 on the first day, 5.38 ± 0.19 at 14th day and 4.84 ± 0.10 on day 21. In 0.5% sodium hypochlorite solution the baseline color steadiness mean value was 6.16 ± 0.18, 6.10 ± 0.06 on the first day, 4.98 ± 0.26 on 14th day and 3.14 ± 0.14 on day 21. ProBase Hot heat cure denture base resin materials after immersion in Distilled water delineated the baseline color constancy mean value was 6.48 ± 0.02, 6.34 ± 0.09 on the first day, 6.08 ± 0.14 on 14th day and 5.88 ± 0.07 on day 21. Within 2% alkaline glutaraldehyde the baseline color constancy mean value was 6.42 ± 0.16, 6.18 ± 0.11 on the first day, 5.12 ± 0.18 at 14th day and 4.24 ± 0.24 on day 21. Within 0.5% Chlorhexidine gluconate the baseline color steadiness mean value was 6.48 ± 0.10, 6.26 ± 0.08 on the first day, 5.48 ± 0.11 on 14th day and 4.88 ± 0.06 on day 21. In 0.5% sodium hypochlorite solution the baseline color steadiness mean value was 6.44 ± 0.12, 6.14 ± 0.08 on the first day, 4.98 ± 0.16 on 14th day, and 3.34 ± 0.06 on day 21. There was a statistically noteworthy difference amid the dissimilar time points in each of the three disinfectants. In the confines of the inherent limitations of this research, it can be inferred that the color steadiness of either denture base resins was enhanced following immersion in 0.5% chlorhexidine gluconate in pursuit by 2% alkaline glutaraldehyde as well as 0.5% sodium hypochlorite solution. Distilled water exerted the smallest amount of influence on the color change of the samples of denture base resins. Techniques that help infection prevention influence denture disinfection. Currently, there is a dearth of commercially marketed agents that are specifically intended to disinfect dentures. Color constancy of the denture materials is an important parameter to be given due consideration while selecting a disinfectant. This would be a pivotal characteristic for practitioners to consider as they choose disinfectant solutions to disinfect dentures.

Surface Treatments and Adhesives Used to Increase the Bond Strength Between Polyetheretherketone and Resin-based Dental Materials: A Scoping Review.

To identify and discuss the available surface treatments and adhesives for polyetheretherketone (PEEK) to increase its bond strength to resin-based materials used in dentistry. The reporting of this scoping review was based on PRISMA. The study protocol was made available at: https://osf.io/4nur9/. Studies which evaluated PEEK surface treatments and its bond strength to resin-based materials were selected. The search was performed in PubMed, Scopus, Web of Sciences and Cochrane databases. The screening was undertaken by 3 independent researchers using the Rayyan program. A descriptive analysis was performed considering study characteristics and main findings (title, data of publication, authors, PEEK characteristics, surface treatments, control group, bonded set, luting agent, specimen geometry, storage, thermocycling, pre-test failures, test geometry, failure analysis, main findings, and compliance with normative guidelines). The initial search yielded 1965 articles, of which 32 were included for descriptive analysis. The review showed that the use of surface treatments and adhesives are important to promote bond strength to PEEK. Up until now, various surface treatments have been explored for bond improvement to PEEK. Sulfuric acid etching is commonly reported as promoting the highest bond strength, followed by alumina-particle air abrasion. Regarding adhesives, the use of a specific adhesive containing MMA, PETIA (pentaerythritol triacrylate), and dimethacrylates yields the best adhesive performance. Sulfuric acid etching and alumina particle air abrasion followed by application of bonding agents containing MMA, PETIA and dimethacrylates are the most effective choices to increase resin-based materials' adhesion to PEEK.

Recent Advances in Direct Adhesive Restoration Resin-Based Dental Materials With Remineralizing Agents

Resin-based dental materials are popular restorative materials especially in direct adhesive restoration because of the excellent mechanical and esthetic properties. Toward the realization of minimally invasive dental procedures, direct composite resin adhesive restoration has become the main treatment for dental defects. In addition, for caries-affected dentin close to the pulp, conservation remineralization has been advocated to save the living pulp. However, the resin–dentin interface can be destabilized by various factors, especially the enzymatic degradation of collagen fibrils within the hybrid layer and polymer hydrolysis. Furthermore, for resin-based restorative materials, the marginal gap remains a major problem that can lead to the occurrence of secondary caries. To address these issues, research efforts have focused on the remineralization of mineral-depleted dental hard tissues using remineralizing bioactive substances. In this review, we first described various bioactive agents with remineralizing properties. Furthermore, we discussed recent advances in resin-based dental materials for enamel or dentin remineralization. Finally, we examined the current challenges and prospects of these emerging materials. This work aims to provide a theoretical foundation for the future development of resin-based dental materials in direct adhesive restoration with remineralizing agents.

Antifungal effect, surface roughness, and cytotoxicity of three-dimensionally printed denture base with phytoncide-filled microcapsules: An in-vitro study

To produce three-dimensionally (3D) printed removable denture bases with antifungal activity using microencapsulation of phytochemicals that inhibit Candida albicans growth. Two types of phytoncide oil extract A and B were micro-encapsulated. The phytoncide-filled microcapsules were mixed with denture base resin for 3D printing with various concentration conditions, and manufactured into the discs by digital light processing. The microcapsule concentrations in 3D-printed discs were 2, 4, 6 and 8wt% for the phytoncide oil A, and 5, 10, 15, 20, and 25wt% for the phytoncide oil B. Nine groups with different microcapsule concentrations and a control group were prepared (n=5). Microcapsule-containing 3D-printed denture base resin discs were evaluated in terms of surface roughness, polymerization, antifungal activity, and its persistence against C. albicans, and cytotoxicity. There was no significant difference amongst the surface roughness values of all discs. The polymerization of 3D-printed resin disc with microcapsule was different between phytoncide type A and B. The discs with phytoncide-filled microcapsules at 6wt% for type A and 15wt% for type B showed significant antifungal activities against C. albicans at 4 weeks. All discs were reported to be non-cytotoxic to human gingival fibroblasts. Denture base resin discs with antifungal activities were successfully manufactured using phytoncide micro-encapsulation and digital light processing. Considering the antifungal effect and its persistence, surface roughness, polymerization, and cytotoxicity, the optimal microcapsule concentrations for 3D-printed denture bases were 6wt% and 15wt% for phytoncide A and B, respectively. Using micro-encapsulation of phytochemicals such as phytoncide oil, denture base resin materials with antifungal activities can be successfully fabricated by digital light processing.

Influence of different concentrations of titanium dioxide and copper oxide nanoparticles on water sorption and solubility of heat-cured PMMA denture base resin.

ObjectivesThis study aimed to evaluate the effect of different concentrations of titanium dioxide (TiO2) and copper oxide (CuO) nanoparticles on the water sorption and solubility of heat‐cured polymethyl methacrylate (PMMA).Materials and MethodsFifty disc‐shaped specimens (10 × 2 mm) of heat‐cured PMMA were prepared and divided into five groups (n = 10) to be modified with 2.5 wt.% or 7.5 wt.% of either TiO2 or CuO nanoparticles. One group was left unmodified, serving as the control group. Water sorption and solubility were measured by weighing the specimens before and after immersion in distilled water and desiccation. The data were analyzed by using one‐way ANOVA and Tukey's post hoc test (α = .05).ResultsThe 2.5 wt.% CuO nanoparticles significantly decreased the water sorption (p = .016), but did not change the water solubility (p = .222) compared with the control group. The 7.5 wt.% CuO and both concentration of TiO2 nanoparticles did not change the water sorption, but significantly increased the solubility of heat‐cured PMMA (p ≤ .05).ConclusionAdding 2.5 wt.% CuO nanoparticles to heat‐cured PMMA decreases the water sorption; although, it has no significant effect on the solubility. Likewise, 2.5 and 7.5 wt.% TiO2 and 7.5 wt.% CuO do not affect the water sorption, but increase the water solubility of heat‐cured PMMA.Clinical SignificanceReinforcing the heat‐cured PMMA denture base resin materials with the right concentration and type of nanoparticles can decrease the water sorption of resin base materials, and consequently can influence the durability of dentures.

Influence of Dimethacrylate Monomer on the Polymerization Efficacy of Resin-Based Dental Cements—FTIR Analysis

The degree of polymerization for dimethacrylate resin-based materials (BisGMA, TEGDMA, UDMA, HEMA) ranges from 55 to 75%. Literature data indicate that polymerization efficacy depends, among other factors, on the type of methacrylate resin comprising the material. The aim of this study was to evaluate the polymerization efficacy of four dental cement materials characterized by different polymerization mechanisms using FTIR analysis. In the present study, the FTIR method was adopted to analyze the degree of polymerization efficacy of four resin-based dental cement materials, two of which were self-cured and two were dual-cured cements. The IR spectral analysis was performed 24 h after the polymerization of the cementitious material. RelyX ARC cement exhibits the lowest polymerization efficacy (61.3%), while that of Variolink II (85.8%) and Maxcem Elite is the highest (90.1%). Although the efficacy of self-cured cements appears to be superior, the difference is not statistically significant (p = 0.280). Polymerization efficacy largely depends on the chemical structure of the material in terms of the presence of a particular methacrylate resin and less on the polymerization mechanism itself, i.e., whether it is a self-cured or dually cured dental cement. Thus, in clinical practice, cementitious materials with a higher proportion of TEGDMA compared with BisGMA are recommended.

In-vitro Comparative Evaluation for the Surface Properties and Impact Strength of CAD/CAM Milled, 3D Printed, and Polyamide Denture Base Resins.

ABSTRACTObjective:There is a paucity of data regarding the effect of fabrication techniques and compositions of CAD/CAM milled, 3D-printed, and polyamide flexible denture base resin materials (DBRMs) on the surface roughness (SR), surface hardness (SH), and impact strength (IS). Therefore, this study aimed to evaluate the SR, SH, and IS of CAD/CAM milled, 3D-printed, and polyamide flexible DBRMs.Materials and Methods:Ninety specimens were constructed from different DBRMs and divided into three groups (CAD/CAM, 3D-printed, and polyamide DBRMs; n = 30) with specific measurements: 15 × 10 × 2.5 mm for SR and H tests and 80 × 10 × 4 mm notched specimen for IS test. SR meter and Vickers micro SH tester were used to measure SR and SH, respectively, whereas the IS was evaluated using Charpy’s impact testing machine. Data were collected and statistically analyzed using one-way analysis of variance and post hoc Tukey’s tests (α=0.05).Results:There were significant differences between the tested materials (P< 0.05). The CAD/CAM milled showed lowest SR when compared with 3D-printed resin and polyamide flexible resin (P< 0.05); however, there was a significant increase in SH of CAD/CAM milled and 3D-printed DBRMs when compared with polyamide materials (P< 0.05). There was a significant increase in IS of polyamide and CAD/CAM milled resins when compared with 3D-printed DBRMs (P < 0.05).Conclusion:CAD/CAM milled resins showed high IS and SH with lower SR.

The cuspal deflection caused by dental composite polymerization shrinkage analyzed by digital holography

Background/Aim. Polymerization shrinkage of filling materials is one of the main disadvantages of adhesive restorative dentistry. The objective of the study was to measure tooth cusps deflection caused by polymerization shrinkage of a resin-based dental material (RDM) in real-time using digital holographic interferometry (DHI) in two groups of cavities restored with and without an additional wall. Simultaneously, internal tooth mechanical behavior was monitored. Methods. Standardized three class I cavities were prepared on third molar teeth. The teeth were cut in two halves in the longitudinal plane, obtaining six samples for the study (now with class II cavities), divided into two groups (group G1 ? with the additional wall, group G2 ? without it), and mounted in aluminum blocks. The cavities were filled with the RDM, cured with a light emitting diode (LED) for 40 sec from the occlusal direction, and monitored during the curing and post-curing period using DHI. Data were analyzed using the Student's t-test for independent samples and the Anderson-Darling test, with an alpha level of 0.05. Results. At the end of the examined period, the samples from the group G1 showed significantly in-creased tooth cusps deflection [t (10) = 4.7; p = 0.001] compared to samples from the group G2. Conclusion. Within the limitations of this study, it was concluded that the presence of the additional wall simulating a dental matrix band had a significant influence on the increase and prolonged deflection of tooth cusps during the examined RDM polymerization shrinkage.

Improvement of Quality of Life through Nanoparticles in Restorative Dentistry

Dental methods aimed at dental rehabilitation, regional anesthesia, orthodontic realigning, permanent hypersensitivity treatment, covalent bonding diamondized enamel, dental health preservation using mechanical dentifrobots, and the formation of artificial bone and teeth are among the possible uses of nanotools in dentistry. The evaluation and treatment of problems affecting the teeth and their surrounding tissues are the focus of restorative dentistry. For the restoration of tooth function and the repair and replacement of damaged tooth structures as well as better aesthetics, advanced procedures are required. In the past few years, resin-based dental restorative materials have made significant progress. Dental composite resin's mechanical performance, minimal polymerization contraction, strong wear resistance, and surface hardness can all be considerably improved by adding nanoparticles to the matrix. To date, nanocomposites for the repair of tooth structure have made one of the most significant contributions to restorative and cosmetic dentistry. Nanocomposites' characteristics aid in minimizing polymerization loss. Their microhardness is higher than that of already employed posterior resin-based composites, and the improved polishability properties in turn result in a smoother surface with better shade qualities. Nanocomposites have a number of benefits, including reduced weight, excellent thermal and electrical properties, antimicrobial activity, and the ability to remineralize dental defects. The other nanotools used in restorative dentistry are nanoadhesives, nanoionomers and nanoendodontic sealants. Nanoadhesives protect against failure of a restoration from bacterial invasion occurs due to spaces between restorative material and preparation margins. Nanoionomers chemically adhere to the surface of the tooth and offer advantages of enhanced bond strength, chemical stability, and insoluble nature. Nano endodontic sealers have the advantage of sealing better than conventional sealers and employing nanoparticles effectively acts as an antibacterial agent. Due to its potential uses and advantages, there is a growing demand for and interest in nano-based dental materials.

Comparative evaluation of flexural strength of denture base resin materials processed using compression molding technique, injection molding technique, and computer-aided design CAM technique: An in vitro study

Comparative evaluation of flexural strength of denture base resin materials processed using compression molding technique, injection molding technique, and computer-aided design CAM technique: An in vitro study

Bisphenol A Release from Dental Composites and Resin-Modified Glass Ionomers under Two Polymerization Conditions.

Bisphenol A (BPA)-based monomers are commonly contained in dental resin-based materials. As BPA is an endocrine disruptor, its long-term release from restorative composites and resin-modified glass ionomers (RM-GICs) under two polymerization conditions was measured in this study. Specimens of two conventional composites containing BPA-based monomers, two “BPA-free” composites, and two RM-GICs were polymerized from one side for 20 s at 1300 mW/cm2 or for 5 s at 3000 mW/cm2. The amounts of BPA released in artificial saliva and methanol after 1, 4, 9, 16, 35, 65, 130, and 260 days were measured using liquid chromatography–tandem mass spectrometry. The highest amounts of BPA were released from conventional composites, followed by RM-GICs, while the least was released from “BPA-free” composites. Amounts of released BPA were significantly higher in methanol and decreased gradually after the first day. Fast polymerization (5 s at 3000 mW/cm2) resulted in a significantly higher release of BPA after 1 day, but the effect of polymerization conditions was not significant overall. In conclusion, fast polymerization increased the initial release of BPA, but the released amounts were significantly lower than the current tolerable daily intake (4 μg/kg body weight/day) even in methanol, representing the worst-case scenario of BPA release.