Nick Silikas

The University of Manchester · School of Dentistry

Background: Nanoparticles (NPs) have gained significant attention in various fields due to their unique properties and potential applications. Polymethyl methacrylate (PMMA) is an acrylic resin widely used in dentistry and medicine. However, the effect of different types of NP fillers on the physical properties of PMMA-based resins has not been tho...

Purpose To develop a biocompatible denture base resin/ TiO 2 nanocomposite material with antifungal characteristics that is suitable for 3D‐printing denture bases. Materials and methods TiO 2 nanoparticles (NPs) with a 0.10, 0.25, 0.50, and 0.75 weight percent (wt.%) were incorporated into a commercially available 3D‐printed resin material. The re...

Objective: To measure the flexural strength (FS) of bulk-fill resin composites and assess their long-term water absorption and solubility properties with and without the inclusion of short glass fibres. Methods: One resin composite, everX Flow with fibres, and four commercially available bulk-fill composites without fibres, namely, PALFIQUE, Act...

Background To study the effect of water storage (3 months) on the creep deformation of various CAD-CAM composite structures at the nanoscale and compare it to that at the macroscale. Methods Seven CAD-CAM blocks were investigated: five resin-composite blocks (RCB), one polymer-infiltrated ceramic network (PICN) block, and one ceramic-filled polyet...

Objectives: To investigate the effect of different surface treatments on optical, topographical and mechanical properties of CAD/CAM lithium silicate-based glass ceramics (LSC's) and their combined effect on the output of a light curing unit (LCU). Methods: Four CAD/CAM LSC's were investigated: Lithium Disilicate (Emax CAD; EC), Zirconia-reinfor...

Objectives: to characterize the effects of graphene oxide (GO) on polymethyl methacrylate's (PMMA) reliability and lifetime. The hypothesis tested was that GO would increase both Weibull parameters and decreased strength degradation over time. Methods: PMMA disks containing GO (0.01, 0.05, 0.1, or 0.5 wt%) were subjected to a biaxial flexural te...

Purpose: Evaluate the effect of different mini-implant numbers on overdenture retention and evaluate attachment wear following one year of simulated placement/removal. Material and Methods. Nine models simulating atrophic mandibles held 27 mini dental implants in three groups of 2, 3, and 4 mini-implants. A total of 1080 simulated placement/remova...

Purpose: Orthodontic treatment involving premolar extractions might improve the angulation of lower third molars, which are the teeth most often impacted. This study analyzes the impact of first/second lower premolar extraction during orthodontic therapy on the angulation of mandibular third molars. Methods: A total of 120 patients treated non-e...

To investigate the flexural strength of hot isostatically pressed nano 3 mol% yttria partially stabilised zirconia and conventionally sintered micro 3 mole% yttria partially stabilised zirconia. Methods: A total of 40 bar-shaped (2 mm × 4 mm × 16 mm) specimens were prepared from hot isostatically pressed nano 3 mol% yttria partially stabilised zirc...

Objectives This study investigated potential variations in polymerisation of light- and dual-cured (LC and DC) resin cements photoactivated through four CAD/CAM restorative materials as a function of substrate thickness. Methods Four CAD/CAM materials [two resin composites CeraSmart (CS) and Grandio Blocs (GB); a polymer infiltrated ceramic Vita E...

Objectives To determine degree of conversion (DC), maximum polymerization rate (RPmax), polymerization shrinkage (PS), maximum shrinkage rate (PS Rmax) and fracture toughness (KIC) of different types of bulk-fill (BF) composites plus the effect of viscosity reduction techniques. Methods BF specimens were created in 2 mm deep molds: SonicFill 3 (S...

Objective Three-dimensional (3D) printing is increasingly being utilised in the dental field because of its time-saving potential and cost effectiveness. It enables dental practitioners to eliminate several fabrication steps, achieve higher precision, and attain consistency in complex prosthetic models. The properties of 3D-printed resin materials...

Objectives To investigate the depth of cure (DoC), fracture toughness (KIC) and wear of ion releasing resin-based composite (RBC) restorative materials. Methods Two ion releasing RBCs, Activa (ACT) and Cention-N (CN) were compared to a conventional RBC (Z350) and a resin-modified glass ionomer cement (Fuji-II-LC). The DoC was measured in a 10-mm d...

Candida albicans and methicillin-resistant Staphylococcus aureus (MRSA) synergize in cross-kingdom biofilms to increase risk of mortality and morbidity due to high resistance to immune and antimicrobial defenses. Biomedical devices and implants made with titanium are vulnerable to infections that may demand their surgical removal from the infected...

Purpose This randomized clinical trial aimed to evaluate the postoperative sensitivity of different resin composite/adhesive materials, placed either by an incremental or bulk-fill technique in posterior resin composite replacement of amalgam restorations. Methods and Materials A total of 47 patients with good overall health and at least four clas...

Purpose: To assess the surface roughness of two different light-cured resin-composites when opposed by monolithic zirconia after simulated mastication. Materials and methods: Materials included a direct restorative nanohybrid (n = 10) and an indirect microhybrid (n = 10) resin-composite (Tetric EvoCeram and Sinfony, respectively). The antagonist...

Introduction Orthodontic fixed retainers are preferred as they depend less on patient compliance. Recently, researchers tried to use fiber-reinforced composite (FRC) to replace the multistranded stainless-steel wire (MSW) of the fixed retainers to enhance the mechanical properties and esthetics. This systematic review aimed to analyze the effective...

Objectives This study investigated the effect of ageing in three food-simulating liquids (FSLs) on mechanical properties of three prosthodontic CAD/CAM polymer composites intended for construction of implant-supported frameworks. Methods Materials investigated were: (i) a carbon fibre-reinforced composite (CarboCAD 3D dream frame; CC), (ii) a glas...

Objective: We aimed to evaluate the failure resistance of different lengths of mini dental implants from the same manufacturer, and to assess their failure following overloading. Materials and Methods: According to the ISO 14801, 15 mini dental implants 2.4 mm in diameter, with lengths of 8.5 mm, 10 mm, or 13 mm, were subjected to compression loadi...

This in vitro study synthetized hybrid composite nanoparticles of graphene oxide (GO) and montmorillonite MMt (GO-MMt) by ultrasound treatments. Samples were characterized by X-ray diffraction, FT-Raman, FTIR, TEM and SEM. The effect of their incorporation (0.3% and 0.5%) on the mechanical properties in a resin-based composite (RBC) and their bioac...

Objectives This study was designed to investigate CAD/CAM restorative blocks and other resin-based materials by (i) determining their chemical composition, (ii) comparing their radiopacity and (iii) correlating their radiopacity with specimen thickness. Methods Disk specimens, of 1and 2 mm thickness (n = 3), were prepared from five CAD/CAM and six...

The rotational movement of mini dental implants (MDIs) overdenture disturbs the function of the prosthesis. Many dentists place more MDIs to improve the overdenture stability; however, the influence of the MDIs number and distribution on the overdenture resistance to para-axial dislodgment has not been investigated. Seven resin models simulating at...

This study aimed to evaluate the colour stability of polymethyl methacrylate (PMMA) denture base reinforced with ZrO2 nanoparticles, E-glass fibres, and TiO2 nanoparticles at various concentrations over 180-day storage in Steradent™ (STD) denture cleaner or coffee (CF). A total of 130 disc-shaped specimens were fabricated at various filler concentr...

Objective Implant-supported frameworks constructed from high-performance polymer CAD/CAM composites are exposed to liquids from the oral environment and routine care maintenance. Therefore, this study investigated the effect of food-simulating liquids (FSLs) on surface properties of three CAD/CAM polymer composite blocks. Methods The composites in...

Objectives The aim of this in vitro investigation was to assess and compare surface characteristics and nanomechanics of model polymer infiltrated ceramic network (PICN) materials compared to CAD/CAM resin composite blocks. Material and methods Four model PICN materials sintered at different temperatures (Exp.125, Exp.130, Exp.135 and Exp.155) wer...

Objective To explore the effect of two curing modes, for dual-cure resin cements, on their monomer elution, water sorption and solubility after 30 d water storage and 30 d dry reconditioning. Methods Eight dual-cure resin-cements were investigated (Bifix SE, Nexus Third Generation, PANAVIA SA, PANAVIA V5, RelyX Ultimate Universal, RelyX Unicem 2,...

Aim: The purpose of this study was to evaluate the mechanical properties of an experimental self-healing dental composite model (SHDC) composed of SiO2 nanoparticles with varying percentages of triethylene glycol dimethacrylate (TEGDMA) monomer and N,N-dihydroxyethyl-p-toluidine (DHEPT) amine microcapsules. Materials and methods: Microcapsules w...

Objective To investigate the effect of sandblasting with fluorapatite glass-ceramic (FGC) powder on zirconia surface roughness, crystallinity, and shear bond strength (SBS) of indirect repairing composite to zirconia using different primers/adhesives. Methods Zirconia blocks were treated as follows: no treatment (control group), blasting with 30-μ...

When PMMA denture base acrylics are exposed to oral environments for prolonged periods, the denture base absorbs water, which has a negative influence on the denture material and the degree to which the denture base will be clinically effective. This study assessed the water sorption, desorption, and hygroscopic expansion processes within PMMA dent...

A convenience sample of 154 edentulous patients referred for implant provision at a Regional National Health Service Dental Hospital in the North West of England were identified. The cephalometric radiographs that were taken as part of the patient baseline investigation were assessed. Digital tracing was used to measure the anterior maxillary and m...

This study aimed to assess water sorption and solubility of CAD/CAM composite blocks compared to CAD/CAM ceramic after 8 months storage in water and artificial saliva. Eight CAD/CAM blocks were investigated: Five resin-composite blocks (RCBs), one polymer-infiltrated ceramic network (PICN) block, one ceramic-filled polyetheretherketone (PEEK) block...

Objective To explore the effect of curing modes of dual-cure resin cements on their degree of conversion (DC) and polymerization shrinkage (PS) over specific post-activation periods. Methods Five self-adhesive (PANAVIA SA, RelyX Universal Resin, RelyX Unicem 2, Bifix SE, and SpeedCEM Plus) and three conventional (PANAVIA V5, Nexus Third Generation...

Objective To explore the effect of different curing modes of conventional and self-adhesive dual-cure resin cements on their rates of thermal decomposition, hardness development and network integrity. Methods Five self-adhesive (PANAVIA SA, RelyX Universal Resin, RelyX Unicem 2, Bifix SE and SpeedCEM Plus) and three conventional (PANAVIA V5, Nexus...

Objective The presence of metallic species around failed implants raises concerns about the stability of titanium alloy (Ti-6Al-4V). Graphene nanocoating on titanium alloy (GN) has promising anti-corrosion properties, but its long-term protective potential and structural stability remains unknown. The objective was to determine GN’s anti-corrosion...

Statement of Problem: Polymethyl methacrylate (PMMA) denture resins commonly fracture as a result of the denture being dropped or when in use due to heavy occlusal forces. Purpose: To investigate the effects of E-glass fibre, ZrO2 and TiO2 nanoparticles at different concentrations on the fracture toughness and impact strength of PMMA denture base....

Titanium implants present 2 major drawbacks—namely, the long time needed for osseointegration and the lack of inherent antimicrobial properties. Surface modifications and coatings to improve biomaterials can lose their integrity and biological potential when exposed to stressful microenvironments. Graphene nanocoating (GN) can be deposited onto act...

Objectives. To investigate the effects of material composition and storage condition on compressive creep deformation and recovery of different resin-based composites (RBCs) and to determine the effect of pre-heating time on compressive creep behaviour of Viscalor. Methods. A creep apparatus was used to measure creep deformation and recovery of RB...

Objectives: The objective of this study was to investigate the mechanical properties of high-impact (HI) heat-cured acrylic resin (PMMA) reinforced with silane-treated zirconia nanoparticles. Methods: Forty-five PMMA specimens reinforced with zirconia were fabricated and divided into three groups: Pure HI PMMA (control group), PMMA reinforced with...

Artificial biomaterials are being developed for use in denture base with symmetrical properties to restore the aesthetics and functionalities. The rough surface of denture base resin promotes the adhesion of microorganisms and plaque accumulation. This study aimed to explore the consequences of polishing times on the surface roughness of high-impac...

The aim of this work was to evaluate the flexural strength and surface hardness of heat-cured Polymethyl methacrylate (PMMA) modified by the addition of ZrO2 nanoparticles, TiO2 nanoparticles, and E-glass fibre at different wt.% concentrations. Specimens were fabricated and separated into four groups (n = 10) to measure both flexural strength and s...

Objective This study aimed to assess the effect of different storage media on the hardness and monomer elution of CAD/CAM composite blocks. Methods Five resin-composite blocks (RCB), one polymer-infiltrated ceramic network (PICN) block (Enamic (EN)), one ceramic-filled poly ether ether ketone (PEEK) block (Dentokeep (DK)), and one feldspathic cera...

The objective of this study was to determine the long-term water sorption, solubility and hygroscopic expansion of resin composites with and without incorporated short fibers. Three resin composites incorporating fibers were examined: everX Posterior (EVX), NovoPro Universal (NPU) and NovoPro Flow (NPF). Four Particulate filled composites were used...

Zirconia repair could be a feasible alternative option to total replacement in fractured zirconia-based restorations. Maximising the bond strength by enriching zirconia with fluorapatite glass-ceramics (FGC) powder has been addressed and compared to other surface treatments. Besides resin composite, other repair materials have been proposed and com...

Objective To determine the polymerization shrinkage (%) and shrinkage stress (MPa) characteristics of ultra-rapid photo-polymerized bulk fill resin composites. Methods Two ultra-rapid photo-polymerized bulk fill (URPBF) materials: PFill and PFlow were studied, along with their comparators ECeram and EFlow. PFill contains an addition fragmentation...

Objectives To evaluate the effect of laser fused and air abraded fluorapatite particles on flexural strength σf and fracture toughness (KIC) of Yttria tetragonal zirconia polycrystal (Y-TZP). Methods 160 polished Y-TZP bars received one of the following surface treatments: airborne particle abrasion (APA) with fluorapatite glass-ceramics (FGC), AP...

Loading and unloading rates a b s t r a c t Objectives. To evaluate nanoindentation as an experimental tool for characterizing the viscoelastic time-dependent creep of resin-composites and to compare the resulting parameters with those obtained by bulk compressive creep. Methods. Ten dental resin-composites: five conventional, three bulk-fill and t...

Nanohardness Filler loading a b s t r a c t Objective. To determine by nanoindentation the hardness and elastic modulus of resin-composites, including a series with systematically varied filler loading, plus other representative materials that fall into the categories of flowable, bulk-fill and conventional nano-hybrid types. Methods. Ten dental re...

d e n t a l m a t e r i a l s 2 8 (2 0 1 2) 928-935 Bulk-fill Viscoelastic time-dependent creep Water storage a b s t r a c t Objectives. To determine the creep deformation of several "bulk-fill" resin-composite formulations in comparison with some other types. Methods. Six resin-composites; four bulk-fill and two conventional were investigated. St...

Objectives: To determine the effect of temperature, over a clinically relevant range, on the creep behaviour of a set of conventional and flowable resin-composites including two subgroups having the same resin matrix and varied filler loading. Methods: Eight dental resin-composites: four flowable and four conventional were investigated. Stainless s...

Objective: To evaluate and compare the surface roughness and gloss of a DMA-free composite and Bis-GMA-free composite with a DMA-based composite before and after toothbrushing simulation. Materials and methods: Fifteen dimensionally standardised composite specimens of three nano-hybrid resin composites (Tetric EvoCeram, Admira Fusion, and Venus...

Objective Viruses on environmental surfaces, in saliva and other body fluids represent risk of contamination for general population and healthcare professionals. The development of vaccines and medicines is costly and time consuming. Thus, the development of novel materials and technologies to decrease viral availability, viability, infectivity, an...

Background: Different materials have been incorporated into the polymethylmethacrylate matrix to improve its performance. The aim of this study was to evaluate the degree of conversion (DC), the flexural strength (FS), the elasticity modulus (EM), and the effect of exposure to food-simulating liquids prior to brushing simulation on the gloss loss...

Purpose: This study evaluated tensile bond strength (TBS) between anterior acrylic teeth and denture bases made of high-impact heat-cured acrylic resin (HI PMMA) impregnated wi