We investigated the viscoelastic response of direct and indirect dental restorative composites by the novel technique of AM-FM atomic force microscopy. We selected four composites for direct restorations (Adonis, Optifil, EPH, CME) and three composites for indirect restorations (Gradia, Estenia, Signum). Scanning electron microscopy with micro-analysis was also used to support the results. The mean storage modulus of all composites was in the range of 10.2–15.2 GPa. EPH was the stiffest (p<0.05 vs. all other composites but Adonis and Estenia), while no significant difference was observed between direct and indirect group (p≥0.05). For the loss tangent, Gradia had the highest value (~0.3), different (p<0.05) from Optifil (~0.01) and EPH (~0.04) despite the large coefficient of variation (24%), and the direct composites showed higher loss tangent (p<0.01) than the indirect composites. All composites exhibited minor contrast at the edge of fillers, showing that these are pre-polymerized, as confirmed by EDS.

The aim of the study was to evaluate the cytotoxicity of three epoxy resin-based endodontic sealer, AH Plus, Sicura Seal and Top Seal. Direct and indirect cytotoxicity were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and LIVE/DEAD^® Viability/Cytotoxicity Assay on MG63 osteoblasts-like cells. Data were statistically analyzed by analysis of variance and Tukey test, setting a significance level of 5%. Both results related to direct and indirect cell viability tests showed that all groups were significantly more cytotoxic than the negative control group. The cytotoxicity activity after one week of culture showed the absence of direct cytotoxicity, while a medium rate of indirect cytotoxicity. All the three epoxy resin-based sealers (AH Plus, Top Seal and Sicura Seal) showed a medium rate of cytotoxicity on osteoblasts-like cells in vitro. No significant difference was found among the sealers analyzed.

Hybrid nanoparticles (CuChNP) comprising of copper nanoparticles with a chitosan shell were synthesized. Antimicrobial properties of CuChNP were assessed against Streptococcus mutans (S. mutans), one of the main bacterium that causes tooth decay. Antibacterial activity of CuChNP against S. mutans was comparable to that of oral antimicrobial agents, such as chlorhexidine, and cetylpyridinium chloride. Particularly, CuChNP exhibited superior capacity to prevent the S. mutans growth on human tooth surface as well as disrupt and kill the bacterial cells in an established dental biofilm. Chitosan may interact with both tooth hydroxyapatite and bacterial cell wall, which improves the adherence of copper to the tooth surface and potentiates their anti-biofilm action. The antimicrobial properties exhibited by CuChNP could be useful for the future development of more effective treatments for the control of dental plaque biofilms.

This study evaluated the effects of surface pretreatment with different concentrations of sulfuric acid etching on surface properties and bonding between Polyetheretherketone (PEEK) and a resin composite. Six groups of surface pretreatment (no pretreatment, etched with 70, 80, 85, 90, and 98% sulfuric acid for 60 s) were treated on PEEK. Surface roughness, scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses were examined. Shear bond strength (SBS) and cross-sectional observations of the interfaces were performed. One-way ANOVA analysis revealed differences in surface roughness and SBS between groups. The 90 and 98% sulfuric acid etching significantly achieved the highest SBS (p<0.05). SEM and AFM demonstrated etched surfaces with wide and deep pores. The 90 and 98% sulfuric acid etching were suggested to be the optimal concentration to improve adhesion between PEEK and the resin composite.

The understanding of cuspal deflection and volumetric shrinkage of resin composites is necessary to assess and improve the placement techniques of resin-based materials. The aim of this study was to investigate the cuspal deflection and its relationship with volumetric polymerization shrinkage of different bulk-fill resin composites. The investigation was conducted using non-contact phase microscopy and micro-computed tomography. Thirty custom-milled aluminum blocks were fabricated for microscopy analysis and thirty-six tooth models with standardized Class I cavities were used for micro-computed tomography analysis. Results showed that high-viscosity composites present higher cuspal deflection compared to bulk-fill composites. The filler loading of resin composites seems to have an effect on cusp deflection, since the higher the filler content percentage, the higher the cusp deflection. On the other hand, it seems to have an opposite effect on volumetric shrinkage, since higher filler loadings produced lower volumetric shrinkage percentages.

Several new urethane-based dimethacrylates were synthesized, characterized and used to formulate the resin composites. Compressive strength (CS) was used as a screen tool to evaluate the mechanical property of the formed composites. Flexural strength, diametral tensile strength, water sorption, degree of conversion and shrinkage of the composites were also evaluated. The results show that most of the synthesized urethane-based dimethacrylates were solid, which are not suitable to dental filling restorations. However, it was found that liquid urethane-based dimethacrylates could be derivatized using asymmetrical methacrylate synthesis. Not only the newly synthesized urethane-based dimethacrylates showed lower viscosity values but also their constructed composites exhibited higher mechanical strengths. Without triethyleneglycol dimethacrylate (TEGDMA) addition, the new urethane-constructed composites showed significantly lower water sorption and shrinkage.

Fluoridated hydroxyapatite (FHA) was investigated for application as an implant coating for titanium bone substitute materials in dental implants. A KrF pulsed excimer deposition technique was used for film preparation on a titanium plate. The compacts were ablated by laser irradiation at an energy density of 1 J/cm² on an area 1×1 mm² with the substrate at room temparature. Energydispersive spectrometric analysis of the FHA film revealed peaks of fluorine in addition to calcium and phosphorus. X-ray diffraction revealed the presence of crystalline FHA on the FHA film after a 10 h post annealing treatment at 450°C. The FHA film coating exhibited significant dissolution resistance to sodium phosphate buffer for up to 21 days, and favorable cell attachment of human mesenchymal stem cells compared with HA film. The results of this study suggest that FHA coatings are suitable for real-world implantation applications.

The shark-fin test was modified to convey the clinical application of a single-step/double-mix technique assessing the behavior of two viscosities applied at one point in time. A medium and light body polyether (PE), a medium and light body polyvinylsiloxane (PVS), and a medium as well as heavy and light body vinyl polyether silicone (PVXE) impression material were analyzed solely, and in a layered mixture of 1:1 and 3:1 at working times of 50, 80, and 120 s. The fin heights were measured with a digital ruler. The wettability was measured 50 and 80 s after mixing by drop shape analysis. The results showed a synergistic effect of the medium and light body PE. This was not observed in PVXE and PVS. Interestingly, PVXE showed an antagonistic flow behavior in 3:1 mixture with medium body. PVXE was more hydrophilic than PE and PVS. Future rheological studies should clarify the detected flow effects.

To determine the effect of titanium (Ti) surface modification by ultraviolet irradiation (UVI) on the bond strength between Ti and porcelain. Grade 2 Ti plates were allotted to five groups: sandblasted (SA), 15 min UVI (UV), SA+5 min UVI (SA+UV5), SA+10 min UVI (SA+UV10), and SA+15 min UVI (SA+UV15). After surface treatment, porcelain was added. A precious metal (MC) was used for comparison with Ti. The effects of 24-h storage at room temperature versus thermal cycling only at 5 and 55°C in water were evaluated. Subsequently, the tensile strength of each sample was tested. Data were analyzed using one-way analysis of variance and the Tukey test. In both the room temperature and thermal cycling groups, the MC and SA+15 min UVI samples showed significantly greater bond strengths than the other samples (p<0.05). UVI processing efficiently increases the bond strength between porcelain and the Ti surface.

This study aimed to investigate how different compositions of experimental silane-based primers in a methyl methacrylate solution containing 3-(trimethoxysilyl)propyl methacrylate (3-TMSPMA) or 3-(4-methacryloyloxyphenyl)propyl trimethoxysilane (3-MPPTS) might act as silicon dioxide bonding agents. With or without post-silanization heat treatment, primer-treated quartz discs were bonded using the MMA-TBB resin and their bond strengths were evaluated. The disks were primed with one of the following materials: 1 mol% 3-TMSPMA, 2 mol% 3-TMSPMA, 1 mol% 3-MPPTS, and 2 mol% 3-MPPTS. Shear bond strength was determined both before and after thermocycling. Statistical analyses were performed with non-parametric procedure (Kruskal-Wallis, Mann-Whitney U, and Steel-Dwass tests). Both primers were effective with heat treatment to enhance bonding between quartz and the MMA-TBB, and the bonding durability of the 1 and 2 mol% 3-MPPTS (16.8 and 24.9 MPa) with heat groups was significantly higher than in the 1 and 2 mol% 3-TMSPMA (5.4 and 9.8 MPa) with heat groups.

The purpose of the present study was to develop an antibacterial mouthguard (MG) material using a masterbatch of silvernanoparticle–embedded ethylene-vinyl acetate (EVA) copolymers. In order to verify that the testing material was clinically applicable as an antibacterial MG material, we conducted an antibacterial test, a shock absorption test, and analysis of in vitro silver release. The colony-forming activity of Streptococcus sobrinus, Porphyromonas gingivalis, and Escherichia coli were significantly inhibited on the testing materials compared with the commercial EVA sheet (p<0.05). The shock absorption capability of the testing material was not significantly different from that of the commercial EVA sheet. Cumulative silver release (in pure water) from the testing materials were infinitesimal after soaking for 20 days, which implied that there could be no harm in wearing the MG during exercise. These results showed that this testing material could be clinically applicable as an antibacterial MG material.

The aim of this study was to evaluate the effect of curcuminoids on the dentin endogenous protease activity. Demineralized dentin were pretreated with 50 or 100 µM of three different curcuminoids for 60 s and incubated up to 3 months. Untreated beams served as controls. Dry dentin mass was measured after incubation. Aliquots were analyzed for the quantity of ICTP and CTX releases for MMP and cathepsin-K mediated degradation, respectively. The effect of curcuminoids on matrix-bound MMP and soluble rhMMP-9 were measured using an activity assay. Data were subjected to repeated-measures-ANOVA (α=0.05). Gelatinolytic activity was analyzed using zymography. ICTP and CTX release and dry mass loss of curcuminoid-treated groups were significantly lower than the control. Inhibition of rhMMP-9 varied from 29–49% among curcumonoid-treated groups, whereas no inhibition was observed at untreated control (p>0.05). Results were confirmed by zymography. The study showed that the pretreatment of dentin matrices by curcuminoids decreases endogenous protease activity-mediated degradation in dentin.

We investigated the effects of incorporation of surface pre-reacted glass ionomer (S-PRG) filler in tissue conditioner (TC) on Candida albicans adhesion. We prepared specimens containing 0, 5, 10, or 20 wt% of S-PRG filler, and measured the amount of C. albicans on the surface using a colony forming unit (CFU) assay and scanning electron microscopic images. In addition, we measured the consistency, penetration depth, and surface roughness (Ra). CFU values for 10 and 20 wt% were significantly lower than that for the control (p<0.05). Hyphal density on the surface was greater in the control. The 10 and 20 wt% specimens showed significantly higher consistency and Ra, lower penetration depth ratio than control (p<0.05). These results suggest that incorporation of S-PRG filler may reduce C. albicans adhesion onto TC surface; however, the optimal amount of filler is dictated by the influence of filler incorporation on mechanical and surface characters of TC.

The aim of this study was to evaluate the antibacterial activity and dentin bonding ability of a commercial self-etch adhesive Clearfil SE Protect (Kuraray Noritake Dental, Tokyo, Japan) in combination with sodium hypochlorite (NaOCl). Agar disc diffusion tests and measurement of minimum inhibitory/bactericidal concentrations (MIC/MBC) against Streptococcus mutans were performed to evaluate antibacterial effects. The mixture solution of 5.25% NaOCl and the primer of Clearfil SE Protect demonstrated less antibacterial activity than primer only. In microtensile bond strength tests using non-carious human molars, pretreatment with 5.25% NaOCl aqueous solution had no influence on the bond strength of Clearfil SE Protect. These results indicate that pretreatment with NaOCl does not influence the bonding ability of Clearfil SE Protect, while their combined use does not enhance cavity disinfecting effects.

This study evaluated the influence in the biocompatibility of human periodontal ligament (hPDL) mesenchymal stromal cell onto poly lactic-acid (PLA) films and PLA fiber membrane. Fiber scaffold was prepared via air jet spinning (AJS) from PLA solutions (6, 7, and 10%) and analyzed using SEM, AFM and FTIR. Biocompatibility was evaluated by adhesion, proliferation and cell-material interaction. PLA film exhibited a smooth and homogenously surface topography in comparison with random orientation of PLA fiber with roughness structure where diameter size depends on PLA solution. Moreover, cell adhesion; proliferation and cell-material interaction has the best respond on random orientation nanofiber of 10, followed by 7, and 6% of PLA in comparison with PLA films. It could be concluded that AJS is an attractive alternative technique for manufacture fiber scaffolds with a tunable random orientation geometry of fibers that allow to produce interconnected porous formed by nanometric fiber diameter structures that could be a potential scaffold for periodontal tissue engineering applications.

This study aimed to evaluate influence of different post-end positions in alveolar bone level on stress distributions in resin-core build-up tooth under different load directions. Three-dimensional mathematical models of a root-filled mandibular premolar tooth were constructed. Resin post and core were built-up with six post lengths: 0, 1, 2, 3, 4, and 6 mm. Finite element analysis calculated stress distributions with oblique load of 400 N to buccal cusp 45 degree from buccal side or from lingual side. The 3 mm-post length (post-end position equal to cancellous bone level) caused highest equivalent stress of post-end compared with the shorter or longer post length. When change of load direction, the direction of maximum shear stress became completely opposite at mesiodistal cervical edge of core-part without a change of the magnitude. Changing shear stress direction would increase risk of debonding at mesiodistal cervical edge.

This study investigated the reinforcing effect of discontinuous-glass fiber fillers with different loading-fractions on selected mechanical properties and wear of resin-modified glass ionomer cement (RMGIC). Experimental fiber-reinforced RMGIC (Exp-RMGIC) was prepared by adding discontinuous-glass fiber of 200–500 µm in length to the powder of RMGIC (GC Fuji II LC) with different weight ratios (15, 20, 25 and 30 wt%). Mechanical properties and wear were determined for each experimental and control material. Scanning electron microscopy was used to evaluate the microstructure of the Exp-RMGICs. Wear pattern was analyzed by a three-dimensional (3D) noncontact optical profilometer. Fiber-reinforced RMGIC (30 wt%) had significantly higher mechanical performance of fracture toughness (1.9 MPa•m^1/2), flexural strength (90.3 MPa), and diametral tensile strength (31 MPa) (p<0.05) compared to unreinforced material (0.8 MPa•m^1/2, 51.9 and 20.7 MPa). The use of discontinuous-glass fiber fillers with RMGIC matrix is novel reinforcement and yielded superior toughening and flexural performance compared to conventional RMGIC.

An endodontically treated tooth with mesial-occlusal-distal (MOD) cavity is often restored with composite resin. Palatal and buccal cusp reduction (MODP, MODPB), and/or fiber-reinforced composite posts (P), are used in an attempt to improve the longevity of the restoration. The aim of this study was to determine the effects of these procedures on von Mises stress values and distribution in dental tissues and restorative materials using finite element analysis. Based on CT scans of an extracted second upper premolar, six 3D endodontically treated tooth models (MOD, MODP, MODPB, MOD+P, MODP+P, MODPB+P) were created. Each model was subjected to a summary force of 150 N on the occlusal surface simulating the normal biting pattern and maximal von Mises stresses were calculated. MODP seems to reduce von Mises stress values in dental tissues and P seems to transfer some of the stresses from dental tissues to the composite filling.

The objective was to evaluate effect of dimethyl sulfoxide (DMSO) on microtensile bond strength (µTBS) and nanoleakage (NL). Superficial dentin was acid-etched and pretreated with DMSO. Etch-and-rinse adhesive was applied and restored with resin composite incrementally. After 24 h, teeth were sectioned, stored in artificial saliva for 24-h or 6-months before µTBS evaluation. Failure modes were examined. Six beams per group were submitted to nanoleakage evaluation using SEM. Data were analyzed using ANOVA and Tukey’s test (α=0.05). Pretreatment had no significant effect on µTBS after 24 h (p>0.05). After 6 months storage, µTBS of control decreased significantly, more than with the groups treated with 0.01% or higher (p<0.05). DMSO-pretreated groups preserved µTBS in all groups. After 6-months, all groups except 0.001% showed significantly lower nanoleakege compared to control (p<0.05). DMSO (0.01–20%) may improve the hybrid layer integrity and bonding durability. The best results were seen with low (1–5%) of DMSO concentrations.

We evaluated the effect of different curing strategies for universal adhesives on micro-tensile bond strength (μTBS) between resin cement and dentin and/or between resin cement and indirect resin composite. Flat coronal dentin surfaces and composite resin disks were pretreated with silane-containing universal adhesives, with or without light-curing on the dentin-side and/or composite resin disk-side. Resin disks were luted onto the pretreated dentin surfaces with the corresponding dual-cure adhesive resin cements and light-cured, and cut into beams after 24-h water storage. After 0 or 10,000 thermocycles (5ºC/55ºC) in a water bath, the μTBS of the composite resin disk–dentin beam was tested. The μTBS was highest when universal adhesives were applied to both the dentin- and the indirect composite resin disk-side, followed by light-curing. Thermocycling decreased μTBS in all but the Scotchbond Universaltreated group, with light-curing on both sides. The effect of curing strategies is dependent upon the materials.