Dental Composites Research Articles

Dental composite biodeterioration in the presence of oral Streptococci and extracellular metabolic products

ObjectiveSecondary caries is a primary cause of early restoration failure. While primary dental caries has been extensively researched, our knowledge about the impact of secondary caries on dental restorations is relatively limited. In this study, we examined how different clinically relevant microbially-influenced environments impact the degradation of nano-filled (FIL) and micro-hybrid (AEL) dental composites. MethodsMaterial strength of two commercial dental composites was measured following incubation in aqueous media containing: i) cariogenic (Streptococcus mutans) and non-cariogenic bacteria (Streptococcus sanguinis) grown on sucrose or glucose, ii) abiotic mixtures of artificial saliva and sucrose and glucose fermentation products (volatile fatty acids and ethanol) in proportions known to be produced by these microorganisms, and iii) abiotic mixtures of artificial saliva and esterase, a common oral extracellular enzyme. ResultsNano-filled FIL composite strength decreased in all three types of incubations, while micro-hybrid AEL composite strength only decreased significantly in biotic incubations. The strength of both composites was statistically significantly decreased in all biotic incubations containing both cariogenic and non-cariogenic bacteria beyond that induced by either abiotic mixtures of fermentation products or esterase alone. Finally, there were no statistically significant differences in composite strength decrease among the tested biotic conditions. ConclusionsThe results show that conditions created during the growth of both cariogenic and non-cariogenic oral Streptococci substantially reduce commercial composite strength, and this effect warrants further study to identify the mechanism(s). Clinical SignificanceDental biofilms of oral Streptococci bacteria significantly affect the mechanical strength of dental restorations.

Shrinkage Deformation of Three Different Light Cure Composite Resin Using Image Correlation Method

The study performed were to measured the amount of shrinkage deformation of resin composites with and without bonding agent. The shrinkage defor mation of three types of composite resin (Ecusphere, Densply, CHARISMA) in cavities was studied using image correlation method. The cylindrical cavity in extracted teeth ( premolors) are to examine the shrinkage behavior on the top free surface. The cavities filled with resin after spreading a bonding agent are irradiated using LED unit, also performed on the cavities without bonding agent. One way analysis of variance and MOIRE analysis were used for statistical analysis. The shrinkage behavior was different in the cavities prepared with and without bonding agent. Polymerization of dental composites is characterized by heterogeneous deformation patterns with variable shrinkage values at different locations within the material.

Acetanilide‐loaded injectable hydrogels with enhanced bioactivity and biocompatibility for potential treatment of periodontitis

AbstractChronic periodontitis poses long‐term challenges in dentistry, requiring the development of innovative dental composites with biocompatibility, bone regeneration, and antibacterial properties. This study focuses on synthesis of novel injectable thermoresponsive hydrogels composed of chitosan, sodium bicarbonate, bioactive glass (20 and 40% w/w), and acetanilide drug (0.3 and 0.6% w/w). These hydrogels exhibit a sol–gel transition at 37°C, addressing periodontal challenges with reduced gelation time. The smooth flow characteristic was evaluated through 17‐22 gauge syringe needles at low temperature. Rheological studies demonstrated pseudoplastic behavior, with viscosity decreasing as shear rate increases. Fourier transform infrared and x‐ray diffraction analysis confirmed the bioactivity of hydrogels, forming a bone‐like apatite layer in simulated body fluid. The drug‐loaded hydrogels demonstrated promising in vitro antibacterial properties against dental pathogens, specifically Staphylococcus aureus and Pseudomonas aeruginosa. Drug dissolution analysis revealed relatively high release rate at 37°C, highlighting its role in rapidly eliminating bacterial colonies at the target site, while the subsequent sustained release contributes to the prevention of infection recurrence. Finally, biocompatibility was assessed with fibroblast, where the cells were observed anchoring into the polymeric chains of hydrogel through extended filopodia.

The Dependence on Hue, Value and Opacity of Real-Time- and Post-Curing Light Transmission in a Nano-Hybrid Ormocer.

This study aims to quantify the influence of hue, value and opacity on the variation in light transmittance of a full color palette of an ormocer-based dental composite. Samples with a thickness of 2 mm were cured in real time while the incident irradiance and light transmittance were recorded with a spectrophotometer, either in real time during the polymerization or through the polymerized composite at different exposure distances. Across the entire shade range, light attenuation was high, varying between 70.3% and 92.1%. The light transmittance during polymerization increased exponentially with exposure time in all shades. The differences between the cured and uncured composites decrease with increasing value and with increasing opacity within a value. The pattern of variation in light transmittance with increasing value is non-linear and depends on the hue, but not on the opacity within a hue. Small variations in value in lighter shades of hue B reduce the transmitted light more than in hue A, while the opposite is true for darker shades. The results strongly suggest an adequate curing of the lower increments in larger restorations, as the additional light expected from curing the upper increments is very small, regardless of hue, value or opacity. An additional unfavorable condition by increasing the exposure distance consistently contributes to a reduction in light transmission and thus further supports the above statement.

Synthesis and characterisation of microcapsules for self-healing dental resin composites

AimThe purpose of this study was to i) synthesise TEGDMA-DHEPT microcapsules in a laboratory setting; ii) characterise the resultant microcapsules for quality measures.Materials & methodsMicrocapsules were prepared by in situ polymerization of PUF shells. Microcapsules characterisation include size analysis, optical and SEM microscopy to measure the diameter and analyse the morphology of PUF microcapsules. FT-IR spectrometer evaluated microcapsules and benzyl peroxide catalyst polymerization independently.ResultAverage diameter of TEGDMA-DHEPT microcapsules was 120 ± 45 μm (n: 100). SEM imaging of the capsular shell revealed a smooth outer surface with deposits of PUF nanoparticles that facilitate resin matrix retention to the microcapsules upon composite fracture. FT-IR spectra showed that microcapsules crushed with BPO catalyst had degree of conversion reached to 60.3%.ConclusionTEGDMA-DHEPT microcapsules were synthesised according to the selected parameters. The synthesised microcapsules have a self-healing potential when embedded into dental resin composite as will be demonstrated in our future work.Graphical Graphical abstract showing the microcapsule components. The shell contains poly(urea-formaldehyde), and the core consists of TEGDMA-DHEPT healing agents.

Synthesis, monomer conversion, and mechanical properties of polylysine based dental composites

ObjectiveThe aim of this study was to synthesize a new bioactive and antibacterial composite by incorporating reactive calcium phosphate and antibacterial polylysine into a resin matrix and evaluate the effect of these fillers on structural analysis, degree of monomer conversion, mechanical properties, and bioactivity of these newly developed polypropylene based dental composites. MethodologyStock monomers were prepared by mixing urethane dimethacrylate and polypropylene glycol dimethacrylate and combined with 40 wt% silica to make experimental control (E-C). The other three experimental groups contained a fixed percentage of silica (40 wt%), monocalcium phosphate monohydrate, and β-tri calcium phosphate (5 wt% each) with varying amounts of polylysine (PL). These groups include E-CCP0 (0 wt% PL), E-CCP5 (5 wt% PL) and E-CCP10 (10 wt% PL). The commercial control used was Filtek™ Z250 3M ESPE. The degree of conversion was assessed by using Fourier transform infrared spectroscopy (FTIR). Compressive strength and Vicker’s micro hardness testing were evaluated after 24 h of curing the samples. For bioactivity, prepared samples were placed in simulated body fluid for 0, 1, 7, and 28 days and were analyzed using a scanning electron microscope (SEM). SPSS 23 was used to analyze the data and one-way ANOVA and post hoc tukey’s test were done, where the significant level was set ≤0.05. ResultsGroup E-C showed better mechanical properties than other experimental and commercial control groups. Group E-C showed the highest degree of conversion (72.72 ± 1.69%) followed by E-CCP0 (72.43 ± 1.47%), Z250 (72.26 ± 1.75%), E-CCP10 (71.07 ± 0.19%), and lowest value was shown by E-CCP5 (68.85 ± 7.23%). In shear bond testing the maximum value was obtained by E-C. The order in decreasing value of bond strength is E-C (8.13 ± 3.5 MPa) > Z250 (2.15 ± 1.1 MPa) > E-CCP10 (2.08 ± 2.1 MPa) > E-CCP5 (0.94 ± 0.8 MPa) > E-CCP0 (0.66 ± 0.2 MPa). In compressive testing, the maximum strength was observed by commercial control i.e., Z250 (210.36 ± 18 MPa) and E-C (206.55 ± 23 MPa), followed by E-CCP0 (108.06 ± 19 MPa), E-CCP5 (94.16 ± 9 MPa), and E-CCP10 (80.80 ± 13 MPa). The maximum number of hardness was shown by E-C (93.04 ± 8.23) followed by E-CCP0 (38.93 ± 9.21) > E-CCP10 (35.21 ± 12.31) > E-CCP5 (34.34 ± 12.49) > Z250 (25 ± 2.61). SEM images showed that the maximum apatite layer as shown by E-CCP10 and the order followed as E-CCP10 > E-CCP5 > E-CCP0 >Z250> E-C. ConclusionThe experimental formulation showed an optimal degree of conversion with compromised mechanical properties when the polylysine percentage was increased. Apatite layer formation and polylysine at the interface may result in remineralization and ultimately lead to the prevention of secondary caries formation.

Recent Advances in Quaternary Ammonium Monomers for Dental Applications.

Resin-based dental materials have been one of the ideal choices among various materials in the treatment of dental caries. However, resin-based dental materials still have some drawbacks, such as the lack of inherent antibacterial activity. Extensive research has been conducted on the use of novel quaternary ammonium monomers (QAMs) to impart antibacterial activity to dental materials. This review provides a comprehensive overview of the recent advances in quaternary ammonium monomers (QAMs) for dental applications. The current progress and limitations of QAMs are discussed based on the evolution of their structures. The functional diversification and enhancement of QAMs are presented. QAMs have the potential to provide long-term antibacterial activity in dental resin composites, thereby prolonging their service life. However, there is a need to balance antibacterial performance with other material properties and the potential impact on the oral microbiome and general health. Finally, the necessity for further scientific progress in the development of novel quaternary ammonium monomers and the optimization of dental resin formulations is emphasized.

Does Preheating Influence the Cytotoxic Potential of Dental Resin Composites?

Resin-based dental composites (RBC) release cytotoxic components, however the extent of the elution from preheated RBCs is barely investigated. The aim was therefore to determine the cytotoxic effect of preheated conventional, bulk, and thermoviscous RBCs of clinically relevant sizes using different cell viability methods in a contact-free model. Samples (6 × 4 mm) were prepared from conventional [Estelite Sigma Quick (ESQ), Filtek Z250 (FZ)] and bulk-filled [Filtek One BulkFill Restorative (FOB), SDR Plus Bulk Flow (SDR), VisCalor Bulk (VCB)] RBCs. The pre-polymerization temperature was set to room temperature (RT) and 55/65 °C. Pulp cells were cultured, followed by a 2-day exposure to monomers released from solid RBC specimens suspended in the culture medium. Cytotoxicity was assessed using a WST-1, MTT, and LDH colorimetric viability assays. Data were analyzed using one-way ANOVA, Tukey's post hoc test, multivariate analysis, and independent t-test. The effect size (ƞp2) of material and temperature factors was also assessed. All the RBCs demonstrated cytotoxic effect upon exposure to pulp cells, but to a varying extent (ESQ >> VCB > FZ = FOB = SDR). The effect of pre-polymerization temperature was insignificant (ƞp2 < 0.03), except for the thermoviscous RBC, which showed inconsistent findings when subjected to distinct viability tests. Cell viability was predominantly dependent on the type of material used (p < 0.001) which showed a large effect size (ƞp2 > 0.90). Irrespective of the pre-polymerization temperature, RBC samples in a clinically relevant size can release monomers to such an extent, which can substantially decrease the cytocompatibility.

Effect of silanization of poly (urea-formaldehyde) microcapsules on the flexural strength and self-healing efficiency of an experimental self-healing dental resin composite (An in-vitro study)

ObjectivesThis study investigated the impact of using γ-methacryloxypropyl trimethoxy silane (MPS) for surface silanization of poly (urea-formaldehyde) (PUF) microcapsules which enclose a healing liquid of “triethylene glycol dimethacrylate (TEGDMA) and N,N dihydroxyethyl-p-toluidine (DHEPT)” on some mechanical properties of an experimental dental composite as well as its self-healing efficiency. MethodsSynthesis of PUF microcapsules was done via in situ polymerization, followed by silanization with MPS silane. Silanized and non-silanized microcapsules were incorporated into a composite containing 30% polymer matrix and 70% fillers at different weight percentages (0%, 5%, 7.5% and 10%). The composite strength and elastic modulus were evaluated by Flexural testing. Fracture toughness KIc and self-healing efficiency were assessed by utilizing the “single edge notched beam” method. ResultsFlexural strength of all groups containing silanized microcapsules was non-significantly different from control group without microcapsules. However, in contrast to control group, all groups containing non-silanized microcapsules displayed considerably decreased flexural strength. Adding silanized and non-silanized microcapsules didn't show a significant change in the KIc-virgin. The silanized microcapsules' groups achieved a self-healing efficiency of about 49–77% recovery in KIc-virgin compared to 38–69% for their non-silanized counterparts. SignificanceIn order to increase the interfacial adhesion with the polymer matrix, improve the mechanical properties, and increase the efficiency of self-healing of dental resin composite, PUF microcapsules were silanized for the first time in the dental field using MPS silane. This innovative silanized microcapsule-containing self-healing composite may hold promise for repairing the damage caused by restorative cracks and extending their service life.

SURFACE MODIFICATION OF ALUMINA-SILICA BY ADDITIVE AGENT USING SOL-GEL METHOD AS FILLER DENTAL COMPOSITE

Background: Macro-sized and inhomogeneous distribution of ceramic filer particles make it difficult to obtain smooth surfaces of dental composite after polishing. Objective. This study aims to synthesize alumina silica (Al2O3-SiO2) fillers using sol gel method with the additives agent chitosan 5%, 10% and polyethylene glycol (PEG) 5% to produce micro particle size and evenly distributed particle as filler dental composite. Methods. The type of research is descriptive explorative. The sol-gel process was utilized to synthesize filler particles of Al2O3-SiO2. TEOS was dissolved in ethanol and mixed with acetic acid as catalyts. Al2(NO3)3 was added into the solution and mixed homogenously. Subsequently, the additive agents (Chitosan 5%, chitosan 10% and PEG) were mixed into the mixture for 30 minutes. Drying the samples for 48 hours at 60°C in the oven. The Dynamic light scattering (DLS) SZ-1 was used to evaluate the size, particle distribution and zeta potential. Result. The results showed that the addition of chitosan 10% produced a smaller size of Al2O3-SiO2 compared to other samples. A homogeneous particle distribution is shown in the sample with PEG 5%. Meanwhile, zeta potential values of the filler particles Al2O3-SiO2 with the addition of chitosan 10% shows the biggest value. Conclusion: The additive agent of chitosan 10% can modify the surface of filler Al2O3-SiO2 in order to inhibit particle growth more effectively but better particle distribution is shown in samples with PEG 5% due to the lower viscosity than chitosan thus it is easily homogenized in the solution

A novel low shrinkage dimethacrylate monomer as an alternative to BisGMA for adhesive and resin-based composite applications.

The aim of this study was to develop a mixture of dimethacrylate isomers (PG6EMA) as a potential monomer for dental adhesives and composites. PG6EMA was synthesized de novo and characterized in the presence of ethanol (3%, 6% or 9%). BisGMA/TEGDMA (BTEG, 50/50 wt.%) was used as the resin control. Composites were formulated with 60 wt.% of either PG6EMA or BisGMA (40 wt.% TEGDMA and 70 wt.% filler). DMPA (0.2 wt.%) and DPI-PF6 (0.4 wt.%) were added as photoinitiators, irradiated with a mercury arc lamp (320-500 nm, 500 mW/cm2; Acticure). All materials were tested for polymerization kinetics (near-infrared), viscosity (η) and storage modulus (G', oscillatory rheometry). The composites were further characterized for water sorption/solubility, wet/dry flexural strength/modulus and polymerization stress. Data were analyzed with one-way ANOVA/Tukey's test (α = 0.05). The PG6EMA resins showed lower rates of polymerization compared with BTEG (p = 0.001) but high degrees of conversion (p = 0.002). Solvent concentration did not affect RPMAX but the 6% and 9% mixtures showed higher final DC, likely due to reduced viscosity. PG6EMA had much higher viscosity than BTEG (p <0.001) and lower G' (p = 0.003). Composites modified with PG6EMA have slower polymerization rates (p = 0.001) but higher final DC (p = 0.04) than the control. PG6EMA/TEGDMA showed lower dry/wet flexural strength and comparable dry modulus. The PG6EMA/TEGDMA composite showed a 18.4% polymerization stress reduction compared to the BTEG composite. Both base monomers had similar WS/SL and G'. Within its limitations, this study demonstrated that the newly synthesized PG6EMA was a viable alternative to BisGMA in dental composites.

An evaluation of dental paste-like bulk-fill composite wear using intra-oral scanner.

This study evaluates the wear resistance of dental paste-like bulk-fill composites compared to conventional paste-like composite resins using an intraoral scanner and 3-D analyzing software. Six different dental composite materials, including five bulk-fill composites and one conventional composite, were tested alongside natural human enamel as a control group. A computer-controlled chewing simulator for wear testing. A one-way ANOVA test was used to identify any significant differences between the means of the tested dental composite materials α=0.05. The results showed variability among bulk-fill composites, with some demonstrating wear resistance similar to conventional composites (p<0.05). Human enamel displayed the lowest wear values, but some bulk-fill composites matched this resistance(p>0.05). Significant variability was observed among bulk-fill composites but the results were comparable to those of conventional composites. The enamel control group demonstrated the lowest wear values, with some bulk-fill composites showing similar wear resistance. This study provides valuable information about the wear resistance of contemporary bulk-fill composite materials, commonly used in current clinical practice, contributing to enhancing clinical procedures.

Relationship between the polymerization distance of monowave and polywave light-curing units and the irradiance and physical properties of dental resin-based composites.

To evaluate the influence of the polymerization distance of monowave and polywave light curing units (LCUs) on the measured irradiance relative to the value reported by the manufacturer in relation to the physical properties of resin-based composites (RBCs). Four LCUs were used: one monowave and three polywave. The irradiance was measured with a digital radiometer. Depth of cure (DC) and flexural strength (FS) tests were performed according to ISO 4049:2019 at polymerization distances of 0 mm and 5 mm. The irradiance of all LCUs was higher than that reported by the manufacturer (>25-64%). The irradiance of the four LCUs was reduced when polymerization was performed at between 0 to 5 mm (paired t-test, P < 0.001). The DC at 0 mm was similar in all groups but was significantly decreased at 5 mm distance (ANOVA P < 0.001). FS showed differences among the LCUs at 0 mm (ANOVA P < 0.001) and was affected by the polymerization distance. The elastic modulus was unaffected by the LCU used or the distance (ANOVA P > 0.001). The LCU must be positioned as near as possible to RBCs during the polymerization process, as increased distance negatively affects the depth of cure and flexural strength.

A low-shrinkage-stress and anti-bacterial adherent dental resin composite: physicochemical properties and biocompatibility.

Polymerisation shrinkage and biofilm accumulation are the two main problems associated with dental resin composites (DRCs) that induce secondary caries, which can cause restoration failure. Polymerisation shrinkage can lead to microleakage gaps between the tooth and the DRCs, causing the aggregation of bacteria and development of secondary caries. Reducing the shrinkage stress (SS) and improving the resistance to bacterial adhesion have always been the focus of this field in modifying DRCs. A thiol-ene resin system can effectively reduce the polymerisation SS via its step-growth mechanism for delaying the gel point. Fluorinated compounds can reduce the surface free energies, thereby reducing bacterial adhesion. Thus, in this study, a range of mass fractions (0, 10, 20, 30, and 40 wt%) of a fluorinated thiol-ene resin system were added to a fluorinated dimethacrylate resin system/tricyclo decanedimethanol diacrylate to create a fluorinated methacrylate-thiol-ene ternary resin matrix. DRCs were prepared using the obtained ternary resin matrix, and their physical and chemical properties, effect on bacterial adhesion, and biocompatibility were investigated. The results demonstrated that the volumetric shrinkage and SS of the DRCs were reduced with no reduction in conversion degree even after the thiol-ene resin system was added. All DRC-based fluorinated resin systems exhibited an excellent anti-bacterial adhesion effect, as evidenced by the colony-forming unit counts, live/dead bacterial staining, and crystal violet staining tests against Streptococcus mutans (S. mutans). The genetic expressions associated with the bacterial adhesion of S. mutans were substantially affected after being cultured with fluorinated DRCs. All fluorinated DRCs demonstrated good biocompatibility through the in vitro cytotoxicity test and live/dead staining images of the L-929 cells. The above results illustrate that the DRCs based on the fluorinated methacrylate-thiol-ene resin matrix can be potentially applied in clinical practice due to their low SS and anti-bacterial adhesion effect.

Impact of storage conditions on the fracture reliability and physical properties of a dental resin-based composite.

This study investigated the impact of 'storage condition' and 'period of storage' on selected physico-mechanical properties and fracture reliability of a resin-based composite (RBC). Specimens, prepared from a nanofilled RBC (Filtek Z350 XT; 3M ESPE), underwent tests for degree of conversion (DC), flexural strength (σ), flexural modulus (E), and hardness. The specimens were initially grouped into dry storage at 37°C or wet storage in distilled water at 37°C. Subsequently, they were further divided into four subgroups based on the period of storage: 6, 24, 72, or 168 hours. Specimens tested immediately after preparation served as control. Data analysis employed two-way ANOVA and Weibull analysis (α = 5%). Compared to the control, an increase in DC was observed only after 72 hours of dry storage; σ showed higher values after both dry and wet storage, regardless of the storage period (except for the group wet-stored for 168 hours); E increased with dry storage for at least 24 hours or wet storage for 72 hours; and hardness increased after dry storage for at least 24 hours or wet storage for up to 72 hours. The Weibull modulus remained unchanged under any of the distinct storage conditions. Dry storage resulted in greater characteristic strength than the control, whereas wet storage contributed to higher strength values only at shorter periods (up to 24 hours). Overall, the inherent properties of RBCs with a similar composition to that tested in this study may change with varying storage conditions and periods.

Fourier-transform infrared spectroscopic method for assessing sensitivity of light-curable dental restorative composites to ambient light – a pilot study

Fourier-transform infrared spectroscopic method for assessing sensitivity of light-curable dental restorative composites to ambient light – a pilot study

Light-curing units for composite resin polymerization

Light-curing units for light polymerization of composite resins are important instruments of dental practice, and their proper use has a direct impact on the physical characteristics of the material being illuminated, its biocompatibility, as well as on the overall clinical success and durability of dental composites. Irradiance represents the power of radiation per unit of irradiated surface and should be distinguished from irradiance measured directly at the lamp head, which is called output irradiance or emittance. Also, different areas on the surface of the material can be exposed to different radiation powers, which sometimes significantly deviate from the given average value. The reason for this is the inhomogeneity of the radiation beam. The 3D profile of the light beam gives the most precise information about the quality of radiation to which the material will be exposed. Due to the existence of different photoinitiator systems, the use of devices with a wider emission spectrum that covers a larger range of light wavelengths is often recommended today. An important characteristic of the light-curing unit is its power, but the use of lamps of higher power does not mean a proportional reduction in polymerization time. The quality and maintenance of light sources are certainly one of the important factors that influence the success of restorations.

Effects of Water Sorption and Solubility on Degradation of Silorane and Methacrylate-Based Dental Composites.

Wet oral environment may have deleterious effects on performance of the composites due to influences of water sorption and solubility. The study evaluated the hydrolytic degradation caused because of water sorption and solubility of silorane and methacrylate-based dental composites. Ten disc samples (2 mm × 10 mm) were prepared. Samples were analyzed for water solubility and sorption according to ISO 4049:2000 regulations and tested for mass gain or loss following immersion in water or in artificial saliva at 1 day, 15 days, and 30 days period. Student's 't' test, repeated measures analysis of variance (ANOVA), and Tukey's post-hoc tests determined statistical significance of the experimental results with global significance set at P = 0.05. Considerable sorption and solubility was observed with time in both materials on immersion. Silorane composites showed lower water sorption and solubility than methacrylate-based composite (MBC). Artificial saliva demonstrated higher sorption and solubility compared to distilled water. Silorane composites display enhanced hydrolytic stability even after a month of immersion in contrast to conventional methacrylate-based composites (MBCs), making it a better alternative to MBC resins clinically.

Can discolored dental composites be bleached in depth?

Previous in vitro studies determined the whitening effects of bleaching products on stained resin composite surfaces. This in vitro study aimed to verify the effectiveness of a whitening system on composite resin previously subjected to pigmentation, specifically examining the depth of whitening effectiveness within the material structure. A commercially available nano-filled composite resin was used. Specimens were stained using a coffee-based solution and a 10% carbamide peroxide-based gel was employed as the whitening agent. The pigment's penetration and the effect of the bleaching gel were evaluated by measuring color (CieLab values) from the outer edge to the inner part of the specimens. Color measurements were taken at 14 points, starting from 0.1 mm from the external perimeter up to 3.0 mm. Analysis of variance tests showed a statistically significant difference between the Control Group (CG), Pigmentation Group, and Whitening Group. The whitening agent was effective up to 1.5 mm in depth, with Whiteness index (W) values not statistically different from those of CG up to 0.5 mm in depth. Whitening agents on nano-filled resin composite previously pigmented appear effective in restoring the W to values similar to the original, particularly in the superficial layers of the sample.

Recent Advances in Whiskers: Properties and Clinical Applications in Dentistry.

Whiskers are nanoscale, high-strength fibrous crystals with a wide range of potential applications in dentistry owing to their unique mechanical, thermal, electrical, and biological properties. They possess high strength, a high modulus of elasticity and good biocompatibility. Hence, adding these crystals to dental composites as reinforcement can considerably improve the mechanical properties and durability of restorations. Additionally, whiskers are involved in inducing the value-added differentiation of osteoblasts, odontogenic osteocytes, and pulp stem cells, and promoting the regeneration of alveolar bone, periodontal tissue, and pulp tissue. They can also enhance the mucosal barrier function, inhibit the proliferation of tumor cells, control inflammation, and aid in cancer prevention. This review comprehensively summarizes the classification, properties, growth mechanisms and preparation methods of whiskers and focuses on their application in dentistry. Due to their unique physicochemical properties, excellent biological properties, and nanoscale characteristics, whiskers show great potential for application in bone, periodontal, and pulp tissue regeneration. Additionally, they can be used to prevent and treat oral cancer and improve medical devices, thus making them a promising new material in dentistry.