Zirconia (ZrO2) ceramic is widely used in dentistry as a clinical dental biomaterial. In this review, we are focusing on and summarizing the biological performance of zirconia under different surface characteristics. We have included an initial tissue cell attachment study on zirconia and bacterial adhesion on zirconia. Our results suggest that surface modifications applied on zirconia may change the interfacial surface characteristics e.g. surface roughness, surface free energy, and chemistry of zirconia. The modifications also result in advanced biological performance of zirconia, including enhanced tissue cell attachment and reduction of bacterial adhesion. The recent laboratory research has provided many interesting modification methods and showed clinically interesting and promising outcomes. A few of the outcomes are validated and have been applied in clinical dentistry.
Computer-aided design and manufacturing (CAD/CAM) resin-produced restorations were approved by a health insurance system in Japan from the year 2014. In this study, we investigated the use of CAD/CAM resin blocks in Japan since 2014, and the clinical use of adhesive systems for CAD/CAM resin-produced restorations in dentistry. Our findings indicated a rise in the clinical application of these products; however, some studies have reported instances of debonding and fracture of the restorations. CAD/CAM resin blocks were implemented in the health insurance system in Japan as an alternative for alloys due to the continuous rise in the prices of gold and palladium. Thus, in order to reduce the number of failures in CAD/CAM resin-produced restorations due to debonding and fracture, the integration of these restorations with the tooth structures is of utmost importance.
Self-etch adhesive (SEA) systems simplify bonding procedures. It is believed that good mechanical retention and chemical bonding are both important factors to obtain reliable bonding to enamel. The enamel acid-base resistant zone (ABRZ) has been confirmed at the adhesive/enamel interface by scanning electron microscopic observation. However, the formation of enamel ABRZ is influenced by the type and components of adhesive systems. Chemical interactions by a functional monomer with hydroxyapatite strongly support the explanation of the mechanism for enamel ABRZ formation. The ABRZ created by MDP-containing SEA systems has shown good potential to resist acid attack from simulated recurrent caries models. In addition, fluoride release may enhance acid resistance. It has been proposed that such a reinforced enamel be termed “Super Enamel”. The concept of the formation of super enamel may contribute to protecting enamel, and conserve tooth structure leading to improved restoration longevity.
Elastic properties of Aryl-Ketone-Polymer (UAKP) and tensile bond strength (TBS) to denture resin (PalaXpress) were tested. Indentation modulus (EIT) and indentation hardness (HIT) were measured via Martens hardness (n=10 specimens) with 4.2±0.6 kN/mm2 and 261±8 N/mm2 respectively. TBS was tested in dependence of different adhesives (visio.link (VL), Adhese Universal (AU), All-Bond Universal (ABU), CLEARFIL UNIVERSAL BOND (CUB), G-Premio BOND (GPB), iBOND Universal (IBU), ONE COAT 7 UNIVERSAL (OCU), Scotchbond Universal (SBU) and without adhesive (CG), n=18/group) and the application of opaquer (n=9/group) after thermocycling (5°C/55°C, 10,000×). TBS was affected by the adhesive (η (P2=0.715, p<0.001) followed by the opaquer (ηP2=0.335, p<0.001). VL and CG showed highest TBS followed by AU and ABU. IBU and GPB resulted in lowest TBS. Opaquer increased TBS for all adhesives (p<0.05), except VL and CG (p<0.258). Elastic properties are well-suited for the indication of removable partial dentures. Bonding to denture resin is no limiting factor.
BioUnion filler incorporated into restorative/coating materials is a new bio-functional glass powder. The most unique function of BioUnion filler is its ability to release Zn2+ in acidic environments. In this study, the ion release profile of BioUnion filler under acidic conditions and its antibacterial effects against Streptococcus mutans were evaluated. The concentrations of Zn2+ released from BioUnion fillers into acetic acids were greater than those released into water. S. mutans inhibition by BioUnion fillers was greater with sucrose than without sucrose, reflecting a decrease in suspension pH in response to the addition of sucrose. Exposure to acids increased Zn2+ release from BioUnion fillers, and the fillers after repeated exposure to acids demonstrated inhibitory effects against S. mutans. These findings suggest that BioUnion filler accelerated the release of Zn2+ under acidic conditions, which induced bactericidal/inhibitory effects against S. mutans.
The aim was to evaluate the effects of different irrigation protocols on the bonding ability of fiber posts on root canal dentin through push-out test and the dentin tubule penetration of luting cement by confocal laser scanning microscope (CLSM). Forty-eight single-rooted premolars were divided into six groups (n=8) based on post space irrigation protocols: Saline 0.85%; Etidronate 18% (HEBP); EDTA 17%; NaOCl 5.25%+EDTA 17%; NaOCl 2.5%/HEBP 9% combination; SmearOFF. Two specimens per group were assessed with CLSM. The push-out test and the failure analysis were performed. Whilst EDTA had the highest bond strength at the coronal and middle thirds, it was not statistically significant compared to saline, HEBP, and NaOCl/HEBP at the middle third (p>0.05). Cement/dentin adhesive failures were predominant (41.9%) and the intratubular fluorescence intensity was significant among the groups (p<0.05). EDTA resulted in highest bond strength values and dentinal penetration.
The aim was to assess the effect of powder to liquid ratio (PLR) on setting time, fluoride release, and compressive strength of conventional glass ionomer cements (GICs) containing pre-reacted spherical glass fillers (SPG). GICs were prepared by mixing SPG with Fuji IX Universal liquid using PLR of 1:1, 1.5:1, 2:1, 2.5:1, 3:1. Setting time decreased from 221 to 51 s upon rising PLR. Increasing PLR decreased cumulative fluoride release (33 to 13 ppm). Diffusion coefficient of fluoride of experimental GICs (1.6–1.8×10−8 cm2/s) was comparable with that of Fuji IX Universal (1.6×10−8 cm2/s). Compressive strength of PLR 2:1 to 3:1 (93–140 MPa) were comparable with that of Fuji IX Universal (124 MPa). These results demonstrated that rising powder ratio reduced setting time, fluoride release, and compressive strength of GICs. However, the setting time and strength experimental GICs with PLR greater than 2:1 were in the acceptable range of the ISO standard.
The purpose of this study was to evaluate the effects of commercialized denture adhesives and mouth moisturizers using direct and indirect cell cultures for in vitro examinations with human fibroblast and epithelial cells. Denture adhesives (Faston, Poligrip Powder, New Poligrip Free, Tafugurippu Kurimu, Polident Adhesive, Tafugurippu Tomei) and mouth moisturizers (Concool Mouth Gel, Biotene Oral Balance Gel) were subjected to live and dead detection and pH level determination. The mouth moisturizers showed higher cytotoxicity effects comparing with control on every cell cultures and cells, and pH level did not show any significant differences. However, there was no correlation of type of denture adhesive or mouth moisturizer with cytotoxicity. We concluded that cytotoxicity affects human cells regardless of type of material, though some dependence was noted.
The objective of this study was to investigate the low temperature degradation characteristics of 2 types of high strength yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) in order to evaluate its suitability for implant body, implant superstructure or abutment. Disk-shaped conventional Y-TZP (0.25 mass% alumina) subjected to hot isostatic press treatment (HIP-Y-TZP) and Y-TZP/4Al2O3 with additional alumina (4.0 mass%) were mirror-polished. Accelerated aging tests with 134°C for 5 h at 0.2 MPa and 180°C for 5 h at 1.0 MPa were performed using an autoclave. Biaxial flexural strength and crystal phases were evaluated. Strength decreased as the proportion of monoclinic phase increased after accelerated aging treatment for both types of high-strength Y-TZPs. Despite the low alumina content, HIP-Y-TZP showed higher static strength and strength after accelerated aging treatment compared to Y-TZP/4Al2O3. However, both types of Y-TZP had adequate strength to be used as dental restorations even after accelerated aging treatment, therefore, its clinical suitability was considered high.
Biomaterials are subjected to various factors during endodontic workflow. The aim was to evaluate the influence of different concentrations of sodium hypochlorite and ultrasound activation on the features and chemical composition of Biodentine. Fifty-four Biodentine samples were divided into 3 groups based on the material setting time. They were subjected to different modes and times of 2% and 5.25% NaOCl irrigation with or without ultrasounds, 12 min (group I), 45 min (group II) and 24 h (group III) after the material mixing. Visual assessment of the sample’s surface was performed using the scanning electron microscope and chemical analysis was made with energy dispersive spectroscopy. Both NaOCl irrigation and ultrasounds affected the surface of the material; however, they did not change its chemical composition. The irrigation enhanced by ultrasounds following the placement of Biodentine should be performed after a longer material setting time. The immediate use of ultrasounds is not recommended.
We investigated the surface modification of orthodontic stainless steel wire using electrophoretic deposition (EPD) of bioactive glass (BG). BG coatings were characterized by spectrophotometry, three-dimensional (3D) focal laser scanning microscopy and scanning electron microscopy. The mechanical properties of the BG-coated wires were estimated nanoindentation, three-point bending and drawing friction tests. BG-coated specimens prepared at higher voltage showed higher values for both reflectance and L* compared to those prepared at lower voltage. Specimens coated at higher voltage had significantly lower surface roughness than those coated at lower voltage, and their BG layers had higher hardness and elastic modulus values. In the three-point bending test, BG-coated wires produced significantly lower elastic modulus than non-coated wires. Most BG-coated specimens produced similar frictional forces to those produced by non-coated specimens. The surface modification technique applying EPD and BG coating to orthodontic stainless steel wire could be used to develop new esthetical orthodontic wire.
The aim of this study was to evaluate the physical properties of calcium-silicate based cements as retrograde filling in different pH and blood conditions using micro-CT. Eighty-four teeth were obturated and after root-end resection, 3 mm-deep root-end cavity was ultrasonically prepared. The samples were divided into four test groups (n=21). Cements were freshly prepared and analyzed with micro-CT before and after exposed. The test groups were exposed for four days to environments containing acid, alkali, or blood. An acidic pH significantly reduced the volume of all materials after four days and differed from the other environments. Biodentine has the highest percentage of loss in volume and density after treatment in an acidic environment. Porosity formation in the acidic medium was observed in Biodentine amongst all materials. The three-dimensional structures of all materials changed after exposed to an acidic pH, while fewer changes were observed in the structures of materials treated with blood and alkali.
The aim of this study was to assess monomer conversion, dimensional stability (mass and volume changes), biaxial flexural strength (BFS), and fluoride release of recently developed resin composites containing alkaline fillers (Cention N; CN) compared with resin-modified glass ionomer cements (RMGICs: Riva LC; RL and Fuji II LC; FL), and conventional composite (Z350). FL showed highest monomer conversion (88±2%) followed by RL (73±10%), CN (59±2%), and Z350 (50±2%). RL exhibited highest mass and volume increase (10.22±0.04 wt% and 19.4±0.2 vol%). CN exhibited higher BFS (180±20 MPa) than RMGICs but lower than Z350 (248±27 MPa). The highest cumulative fluoride release at 6 weeks was observed with RL (136±22 ppm) followed by CN (36±4 ppm) and FL (30±3 ppm). CN exhibited monomer conversion higher than the composite. CN also released fluoride in the range of that observed with RMGICs but with higher flexural strength.
This study aimed to determine the role of the 10-methacryloyloxydecyl dihydrogen phosphate (MDP) in dentin bond durability of universal adhesive in etch-&-rinse mode through bond strength tests after different degradation conditions. This study used the MDP-containing universal adhesive, Clearfil Universal Bond Quick (CU), and an experimental adhesive (NM) made with the same ingredients as CU, excluding MDP. Shear bond strength (SBS) to dentin were obtained in etch-&-rinse mode with or without MDP. CU in self-etch mode was used as a comparison. The groups were divided into three types: 1) subjected to thermal cycling; 2) subjected to long-term water storage; and 3) stored in water for 24 h, as a baseline. The discrepancies in the mean SBS of the CU and NM groups become prominent with prolonged degradation periods. This study indicates that the MDP in universal adhesive might play a key role in enhancing dentin bond quality even when etch-&-rinse mode is used.
The study evaluated the quality of gingival margins created by cervical margin relocation (CMR) technique using different materials and assessed the consistency of the results obtained by two in vitro methods: microleakage test and scanning electron microscopy (SEM). Mesio-occlusal-distal cavities with subgingival proximal margins were prepared. Mesial margins were elevated supragingivally with total-etch adhesive and flowable composite (Group 1) or with universal adhesive and bulk-fill flowable composite (Group 2). Distal margins were not elevated. Teeth were restored with CAD/CAM overlays. Marginal quality was evaluated by microleakage test and SEM observation of epoxy resin replicas. Statistical analyses showed no significant correlations between microleakage scores and percentage of marginal integrity observed under SEM at CMR margins, lower microleakage scores at margins without CMR compared to CMR margins, lower microleakage scores in Group 2 than in Group 1 and no difference in SEM integrity between groups at CMR margins.
White Silicon nitride (Si3N4) ceramic has unique characteristics. Because of its high fracture toughness, strength, and biocompatibility, it can therefore be used to fabricate dental restorations. The purpose of this study was to produce partially-sintered block of Si3N4 for fabrication of CAD/CAM dental restorations. The related properties of this novel Si3N4 were evaluated including sintered shrinkage, flexural strength and fracture toughness. Partially sintered Si3N4 ceramic blocks were prepared by heating at 1,400°C for 2 h under N2 gas. After full sintering at 1,650oC for 2 h, the linear shrinkage value was recorded at 19.88±0.56%. The flexural strength and fracture toughness were measured, the results were 891.21±37.25 MPa and 6.33±0.30 MPa•m1/2, respectively. These results showed that flexural strength and fracture toughness of Si3N4 were more than 800 MPa and 5 MPa•m1/2, the white Si3N4 developed in this study can be used to fabricate multi-unit dental restorations According to ISO 6872.
This study investigated the efficacy of copper (Cu) as an antibacterial element incorporated on titanium (Ti) surface by electrochemical treatment. Cu was incorporated onto Ti surface by micro-arc oxidation (MAO). A small amount of Cu was incorporated into the oxide layer and was found to be in oxidized states. Cu-incorporated samples exhibited no-harmful effect on the proliferation of osteoblastlike cells. Moreover, the difference in antibacterial property between fresh and incubated samples was evaluated using gram-positive and gram-negative facultative anaerobic bacteria. The specific antibacterial property of Cu incorporated into the Ti surface were confirmed. The antibacterial property prolonged upon immersion in physiological saline for 28 days. In other words, MAO-treated Ti containing Cu in this study is expected to achieve long-term antibacterial property in practical usage.
The aim of this study was to establish a measurement method for filler and matrix in cured resin composite (RC) using Python programming and to investigate the correlation between matrix ratio and curing temperature rise. Eight kinds of RCs were used. Backscattered electron images were taken for each cured specimen. Matrix and filler contents were calculated using Python programming with the K-means or area segmentation method. Volume measurement methods were assessed for comparison. Heat released during the polymerization reaction was measured. The matrix ratio was calculated without human intervention. Three specimens contained only inorganic filler, and other specimens contained multiple types of fillers. Almost the same values of the matrix ratio were obtained by programming and the volume measurement methods for specimens containing a single type of inorganic filler. Moreover, a strong correlation was found between the matrix ratio obtained by the programming method and curing temperature rise (R=0.9826).
In the oral environment dental materials are subject to a wet condition what might in time change their elastic properties. In this article, we evaluated the influence of the storage condition (dry versus wet) on the Young’s modulus and the Poisson ratio in compression of three composite materials. The data of the Young’s modulus and Poisson ratio published of dental composite materials are not always comparable, due to different test methods and sample dimensions influencing the results. Therefore, we established the degree of exactness of the results out of the test set-up used. Since the present study depicted differences of the properties after dry and wet storage, the elastic properties should be measured after wet storage. The bonding between the matrix and the filler particles showed to have an influence on the elastic properties and on the influence of a wet environment.
Determining whether tea extracts are effective in removing Candida albicans (C. albicans) from dentures is of interest. This study aimed to investigate the antifungal effect of tea extracts on C. albicans. One green tea (Anji white tea, AGW) and 2 oolong teas (Tie Guan Yin, TGY; Da Hong Pao, DHP) of different concentrations were tested. C. albicans suspensions were inoculated on the plates and the numbers of colony-forming units (CFU) in the culture medium were used to screen for the optimum tea extracts. Polymethyl methacrylate (PMMA) specimens that contained C. albicans biofilms were then treated with the tea extracts and the numbers of CFU were counted. The antifungal activities of the tea extracts were not significantly correlated with their catechin concentrations. Although AGW at 10.0 mg/mL and DHP at 2.5 mg/mL significantly inhibited C. albicans in the culture medium, the extracts failed to exert inhibitory effects against C. albicans biofilms on the PMMA surfaces.
The aim of this study was clarify the effects of reducing various functional pressures essential for the maintenance of bone homeostasis. Femoral bone mineral density (BMD) and biological apatite (BAp) crystallite alignment were measured in conventionally reared and hindlimb-unloaded mice. The femur was divided into 10 equal segments perpendicular to the longitudinal axis of the bone and measurements were performed on the cortical bone in the five segments closest to the midpoint of the femur. Significantly lower BMD and BAp alignment in the longitudinal (Z-axis) direction were observed in the hindlimb-unloaded group. The present findings suggest that unloading by tail suspension significantly decreases not only mouse femoral bone mass but also BAp crystallite alignment, although minimal uniaxial preferential alignment is retained.
Short-term studies on calcium-phosphate (CaP) ion-rechargeable composites were reported. The long-term rechargeability is important but unknown. The objectives of this study were to investigate nanocomposite with strong antibacterial and ion-recharge capabilities containing dimethylaminododecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and evaluate long-term ion-recharge by testing for 12 cycles (taking 6 months to complete) for the first time. Three groups were tested: (1) Heliomolar control; (2) Resin+20%NACP+50%glass; (3) Resin+3%DMAHDM+20%NACP+50%glass. Biofilm acid and colony-forming units (CFU) were measured. Ion-recharge was tested for 12 cycles. NACP-DMAHDM composite reduced biofilm acid, and reduced CFU by 4 logs. High levels of ion releases were maintained throughout 12 cycles of recharge, maintaining steady-state releases without reduction in 6 months (p>0.1), representing long-term remineralization potential. Bioactive nanocomposite demonstrated long-term ion-rechargeability for the first time, showed remineralization and potent anti-biofilm functions, with promise for tooth restorations to combat caries.
We investigated the inhibitory effect of antibacterial agents mixed with experimental fluoride varnish (EFV) on Streptococcus mutans. The antibacterial agents used were (1 and 10) mM of xanthorrhizol, bakuchiol, bavachalcone, isobavachromene, and bavachromene. Agar diffusion tests were performed on S. mutans (1.1×1010 CFU/mL), using antibacterial agents without and with EFV. Bavachalcone showed the highest inhibition zone without and with EFV at both (1 and 10) mM (p<0.05). All EFV with antibacterial agents showed greater inhibition and semi-inhibition zones than EFV alone (p<0.05). The cell viability of each antibacterial agent was not significantly different from the vehicle controls (p>0.05), except xanthorrhizol and bakuchiol at 1 mM. All antibacterial agents were effective, while antibacterial agents with EFV co-formulations were more effective than EFV alone. Bavachalcone was the most effective agent against S. mutans, indicating its potential usefulness with fluoride varnish in preventing dental caries.