Fluid accumulation in the hollow spaces of obturator is a continuing problem when fabricating hollow obturator prostheses using the conventional method. To address this problem, the three-dimensional (3D) digital technology was used to evaluate water absorption in the inner hollow obturator spaces. Solid and hollow obturator specimens were fabricated using a 3D printer with photocurable resin. Then, the hermeticity was examined by leak testing. These specimens were immersed in distilled water at 37°C. Each specimen was weighed every 24 h for 120 days, and weight changes between each group were compared. Water accumulation in the hollow obturator was not visually observed. Although water absorption was significantly higher in solid specimens, the weight increase rate was also significantly higher in hollow specimens. Applying a laminating 3D photo fabrication made the fabrication of a completely unified hollow obturator model possible.

This study compared the biocompatibility, mechanical properties, and surface roughness of a pre-polymerized polymethyl methacrylate (PMMA) resin for CAD/CAM complete removable dental prostheses (CRDPs) and a traditional heat-polymerized PMMA resin. Two groups of resin substrates [Control (RC): conventional PMMA; Test (RA): CAD/CAM PMMA] were fabricated. Human primary osteoblasts and mouse embryonic-fibroblasts were cultured for biocompatibility assays. Mechanical properties and surface roughness were compared. ANOVA revealed no difference between the resin groups in the biocompatibility assays. RA demonstrated a higher elastic modulus (p=0.002), young’s modulus (p=0.002), plastic energy (p=0.002), ultimate strength (p=0.0004), yield point (p=0.016), strain at yield point (p=0.037), and toughness (p<0.0001); while RC displayed a higher elastic energy (p<0.0001). Laser profilometry concluded a rougher surface profile (p<0.0001) for RA. This study concluded that the tested CAD/CAM resin was equally biocompatible and presented with improved mechanical properties than the traditional heat-polymerized PMMA resin used in the fabrication of CRDPs.

In this study, we investigated the effect of light irradiation and primer/adhesive application on the polymerization reaction and elastic modulus (E) of self-adhesive resin cement (SAC) through ultrasonic velocity (V) measurements. The V values of longitudinal and shear waves were determined based on the transit time through the specimens and specimen thicknesses, and were used to calculate the E values. Analysis of variance and Tukey tests revealed that V increased rapidly, reaching a plateau at 2,700–2,900 m/s, when the SACs were light-irradiated. However, the increasing rate of V was retarded for the non-irradiated SACs. In addition, when the primer/adhesive was applied, higher E values were obtained after 24 h. Finally, the polymerization behavior of the SACs was affected by light irradiation and primer application, and the use of prime/adhesive might improve mechanical properties. In clinical situations, use of primer/adhesive is recommended for getting proper adhesion.

The purpose of this study was to investigate the effect of acid erosion on the bonding performance of universal adhesives. Freshly extracted bovine teeth were cut into enamel slabs and assigned to either the Er or the control group. Specimens in the Er group were immersed in citric acid solution (pH 2.1) twice a day and stored in artificial saliva, while control specimens were simply stored in artificial saliva. Differences in the mean values between the control and Er groups were greater than expected, despite accounting for the effect of differences in the adhesive systems (p=0.016). The Er group mainly exhibited cohesive failure in the enamel, while adhesive failure was more frequent in the control group. The sonic velocity was found to decrease over time in the acid attacked specimens. The results indicated that bond strengths of universal adhesive tested increased in eroded enamel.

This study aimed to investigate mechanical properties related to flexibility and fracture resistance of controlled memory wiremanufactured nickel-titanium rotary glide path files [HyFlex EDM Glide Path File (EDM) and HyFlex GPF (GPF)]. Scout RaCe (RaCe) served as control. Bending loads, torsional/cyclic fatigue resistance, and screw-in forces were measured. EDM showed a significantly larger torque at fracture, a longer time to cyclic fracture in reciprocation and a larger screw-in force compared with GPF and RaCe. GPF showed significantly lower bending loads and higher angular deflection values than EDM and RaCe, and a significantly longer time to cyclic fracture than RaCe. The time to cyclic fracture was significantly longer in reciprocation compared with continuous rotation in EDM and GPF. It can be concluded that EDM and/or GPF showed higher flexibility and cyclic/torsional fatigue resistance compared with RaCe; and that reciprocation conferred better cyclic fatigue resistance to EDM and GPF.

Enamel demineralization is one of the most undesired side effects of fixed orthodontic treatment, which will lead to white spot lesions (WSLs) on tooth surfaces. The development of WSLs is due to prolonged accumulation of bacterial plaque and associated acid production. Self-etching adhesives have been used in orthodontic treatments with several advantages over the more traditional acid-etch method. However, current self-etching adhesives in orthodontic treatments have no antibacterial activity. The objectives of this study were to develop a self-etching and antibacterial orthodontic adhesive, and to investigate its enamel bond strength and antibacterial properties. A novel quaternary ammonium monomer dimethylaminohexadecyl methacrylate (DMAHDM) was incorporated into a commercial self-etching adhesive (Adper Easy One, 3M). It showed that the 5% DMAHDM appeared to be optimal in obtaining the strongest antibacterial function without compromising the enamel bond strength both at 15 min and after 30 days of immersion plus thermal cycling.

The purpose of this study was to investigate the effect of remaining dentin thickness (RDT) and long term water storage on dentin bond strength in-vitro. Twenty-seven third molars were randomly divided into 3 groups: Clearfil Bond SE ONE (SE1, Kuraray Noritake Dental, Okayama, Japan), G-Bond plus (GB, GC, Tokyo, Japan) and Clearfil Mega Bond (MB, Kuraray Noritake Dental). Bonded specimens were stored in water at 37ºC for 24 h. The teeth were then sectioned perpendicular to the adhesive interface to produce beams. RDT of each beam was measured digital calliper. Microtensile bond strength testing was carried out at a crosshead speed of 1 mm/min after 24 h and 1 year water storage. Thicker RDT produced higher bond strengths with one/two-step self-etch materials tested except for the group of 24 h MB. Nevertheless water storage time and RDT affected µTBS in all materials used.

The purpose of this study was to investigate the formation of acid-base resistant zone (ABRZ) of enamel surface during bracket bonding by using three self-etch adhesives presently available in the orthodontic treatment. Also, the relation between the thickness of the ABRZ and bonding strength, the relation between the thickness of the ABRZ and the concentration of fluoride ions contained in the adhesives, were discussed respectively. The ABRZ was formed with all self-etch orthodontic adhesives. ABRZ thicknesses of two self-etch adhesives were approximately 0.8–1.0 μm, whereas ABRZ thickness of other one was about 0.1 μm. The bond strengths of all self-etch orthodontic adhesives indicated over 10 MPa, and ABRZ thickness observed in the enamel surface seemed to have no influence to the bond strengths among self-etch adhesives. Moreover, the thickness of ABRZ appeared to be associated with the amount of fluoride ion released from the primer.

Heparin binds to and modulates various growth factors, potentially augmenting the bone-forming capability of biomaterials. Here, α-tricalcium phosphate (α-TCP) granules were modified with peptide containing the marine mussel-derived adhesive sequence, which reacts with α-TCP surface, and cationic sequence, which binds to heparin (α-Ph). α-Ph retained the α-TCP phase and intergranule spaces after the surface modification. The existence of heparin on α-Ph granules was confirmed using X-ray photoelectron spectroscopy. Granules of α-TCP and α-Ph were implanted into critical-size defects in rat calvaria for 4 weeks. Micro-computed tomography, histological evaluation, and Alcian blue staining revealed that α-Ph induced superior bone formation compared with α-TCP. Newly formed bone on α-Ph was preferentially in contact with the Alcian blue-stained surfaces of granules. These results suggested that heparinization enhanced the early osteogenic capacity of α-TCP, possibly by modulating the secretion of Alcian blue-stained extracellular matrixes.

This study aimed to investigate amount of γ-methacryloxypropyltrimethoxysilane (MPS) silanized on experimental nanosilica particles (NPs), amount of NP and amount of MPS silanized NP on flexural strength (FS), flexural modulus (FM), and fracture toughness (FT) of NP reinforced polymethyl methacrylate (PMMA). The chemisorbed amount of MPS was determined using elemental analysis. Six groups (n=8) were prepared with chemisorbed amount and mixed with PMMA-monomer to make 0.25, 0.5, 1, 5, 10 and 15% (w/w) of NP reinforced PMMA. PMMA without NP served as control. Seven groups (n=8) were prepared with 1% of NP silanized with 0, 0.061, 0.123, 0.246, 0.493, 0.987, and 1.974 g_MPS/g_silica and mixed with PMMA-monomer to make NP reinforced PMMA. FS, FM, and FT were determined using 3-point bending test. One-way ANOVA and multiple comparisons showed that 0.246 g_MPS/g_silica of 1% amount of silanized NP group was significantly highest in FS, FM, and FT compared to the others (p<0.05).

The torsional fracture strength at the interface between a base plate and veneering material was evaluated for three kinds of veneered restoration: porcelain fused to zirconia (PFZ), porcelain fused to metal (PFM), and composite resin veneered metal (CRVM). The metal and zirconia base plate (30×4×0.4 mm) were prepared and these plates were veneered as test specimens using each material to a total thickness of 1.2 mm. Torsional force was applied to each specimen using a rotational speed of 1.0 deg/min until the veneering material underwent fracture or exfoliation. The torsional fracture values were measured and the data were statistically analyzed using one-way ANOVA. The torsional fracture strength for PFZ, PFM, and CRVM was 3.0, 3.1, and 11.1 N•cm, respectively.

This study was to investigate the effects of O₂ plasma-etching of the 3D polycaprolactone (PCL) scaffold surface on preosteoblast cell proliferation and differentiation, and early new bone formation. The PCL scaffolds were fabricated by 3D printing technique. After O₂ plasma treatment, surface characterizations were examined by scanning electron microscopy, atomic force microscopy, and contact angle. MTT assay was used to determine cell proliferation. To investigate the early new bone formation, rabbits were sacrificed at 2 weeks for histological analyses. As the O₂ plasma etching time is increased, roughness and hydrophilicity of the PCL scaffold surface increased. The cell proliferation and differentiation on plasma-etched samples was significantly increased than on untreated samples. At 2 weeks, early new bone formation in O₂ plasma-etched PCL scaffolds was the higher than that of untreated scaffolds. The O₂ plasma-etched PCL scaffolds showed increased preosteoblast differentiation as well as increased new bone formation.

Ca-P spots modified zirconia by liquid precursor infiltration and the cell responses were investigated. Pre-sintered zirconia specimens were immersed in Ca-P precursor solution. After dense sintering, scanning electron microscopy showed Ca-P spots were formed on the zirconia and anchored with zirconia substrates. The distribution density was increased with the extension of immersion time. Energy dispersive spectrometer confirmed the stoichiometric Ca/P ratio was about 1.67. After hydrothermal treatment, Ca-P spots turned into rod crystals where diffraction peaks of tricalcium phosphate and hydroxyapatite were detected by X-ray diffraction, and Ca²⁺ and PO₄³⁻ release decreased slightly (p>0.05). There was no significant decrease on three-point bending strength (p>0.05). Osteoblast-like MC3T3-E1 cells attached and spread well and showed higher proliferation on Ca-P spots modified zirconia (p<0.05), though its initial alkaline phosphatase activity was not significant high (p>0.05). In conclusion, Ca-P liquid precursor infiltration is a potential method to modify the zirconia ceramics for improving bioactivity.

The 12-methacryloxydodecylpyridium bromide (MDPB) has been reported to act as a matrix metalloprotease (MMP) inhibitor. In this study, the effects of application of MDPB on resin-dentin bonds were evaluated. The resin-dentin bonded specimens were prepared with a commercial MDPB-containing self-etching primer or a self-etching primer without MDPB, and stored 24 h or 1 year. Surfaces were pretreated with chlorhexidine or MDPB-containing cavity disinfectant. Additionally, we compared the degradation patterns between the two self-etching adhesives and etch and rinse system. Water tree formations were observed as the typical morphological phase of the two tested self-etching adhesives for both 24 h and 1 year groups. The degradation phase of collagen network depletion was observed in the adhesive interface of the etch-and-rinse system in the 1 year group. Pretreatment with chlorhexidine did not prevent bond strength reduction after 1 year. The cavity disinfectant improved the bond durability for the self-etching adhesive.

We compared the accuracy of digital models generated by desktop-scanning of conventional impression/plaster models versus intraoral scanning. Eight ceramic spheres were attached to the buccal molar regions of dental epoxy models, and reference linear-distance measurement were determined using a contact-type coordinate measuring instrument. Alginate (AI group) and silicone (SI group) impressions were taken and converted into cast models using dental stone; the models were scanned using desktop scanner. As an alternative, intraoral scans were taken using an intraoral scanner, and digital models were generated from these scans (IOS group). Twelve linear-distance measurement combinations were calculated between different sphere-centers for all digital models. There were no significant differences among the three groups using total of six linear-distance measurements. When limited to five lineardistance measurement, the IOS group showed significantly higher accuracy compared to the AI and SI groups. Intraoral scans may be more accurate compared to scans of conventional impression/plaster models.

This study was performed to evaluate the comparative radiopacity of adhesive/resin composite materials in cylindrical cavities using micro-computed X-ray tomography (μCT). The two-step self-etch adhesive systems, Clearfil SE Bond (SE) and FL-Bond II (FL), and flowable resin composites, Beautifil Flow F10 (BF) and Clearfil Majesty ES Flow High (MJ), were used. The radiopacity of bovine tooth structures and restorative materials was measured by μCT. In addition, cylindrical cavities prepared in bovine teeth were restored with the following adhesive/composite combinations: SE-BF, SE-MJ, FL-BF, and FL-MJ. The mean gray values of the composite restorations were calculated. The threshold values of the μCT images were evaluated using the Otsu’s thresholding method. The current results show that the comparative radiopacity of the materials and tooth structure varied, which affected distinguishing the μCT images of the composite restorations in the cylindrical cavity. The proper combination of restorative materials should be considered when conducting in vitro μCT assessments of composite restorations.

The aims of this study were to assess the diagnostic accuracy of swept-source optical coherence tomography (SS-OCT) for detection of caries beneath composite restorations and to compare the results with those obtained by radiography. Flat dentin surfaces with and without natural caries were bonded with 1- or 2-mm thick composite restorations. SS-OCT scanning was performed over the composite restorations to construct three-dimensional (3D) images of the resin-dentin interface. Images were chosen from the 3D constructions to detect caries beneath the restorations. The sensitivity, specificity, false positive and negative predictive values for caries detection, and Az values from receiver-operating characteristic analysis were calculated and compared with those of digital dental radiography at a significance level of α=0.05. Intraexaminer and interexaminer reproducibility was compared between SSOCT and radiography. SS-OCT could detect caries, which appeared as a bright zone beneath composite up to 2-mm thick. SS-OCT provided greater diagnostic accuracy than radiography.

This study examined the influence of the time-dependent wettability of different surface topographies on initial cellular behavior. Titanium disks with smooth topography (SM) and three kinds of rough topography (sandblasted (SA), microtopography (M) and nanotopography (N)) were prepared. Time-dependent changes in surface wettability were observed in all surfaces as shown in previous studies. On SM surfaces, hydrophobic alteration influenced cell spreading and the activity of RhoA (a small GTPase protein of the Rho family), while no alterations were observed on rough surfaces except for the number of adherent cells. Serum adsorption could recover these functional deteriorations by hydrophobic alteration. These findings suggest that surface topography is a more potent regulator in initial cellular behaviors such as cell spreading and RhoA activation than surface wettability.

We evaluated effectiveness of tea tree oil (TO) and lemongrass oil (LO) for removal of Candida biofilm from denture base resin and their influence on that surface. Biofilm of C. albicans was formed on resins, and immersed in various concentrations of each oil and distilled water (DW). The biofilm removal effect was determined by incubating specimens in RPMI medium containing Alamar blue (AB) and measuring absorbance. Wear test was also conducted, and surface condition of resins was determined using laser scanning microscope and digital microscope. Specimens immersed in the TO and LO solutions tended to have a lower AB value at higher concentrations and longer soaking times. Use of these agents resulted in less surface roughness as compared to DW. Our results suggest that TO and LO were valid to remove biofilm attached to resin with lower levels of abrasion, and these are effective for use in denture cleaner.

This study aimed to compare the mechanical properties of differently-tapered EndoWave nickel-titanium endodontic rotary instruments (size #30/0.04 taper and #30/0.06 taper; Group 0.04 and 0.06, respectively). Torsional and bending properties were evaluated with the cyclic fatigue test and the cantilever bending test, respectively. Canal transportation was assessed following instrumentation of curved canals in resin blocks. Torque and apical force during instrumentation were determined using an automated instrumentation and torque/force analyzing device. The number of cycles to fracture was Group 0.04>Group 0.06 (p<0.05). The bending load values were Group 0.06>Group 0.04 (p<0.05). Group 0.04 better maintained the original canal shape compared with Group 0.06. The median clockwise torque value was Group 0.06>Group 0.04 (p<0.05), whereas no significant differences were detected in the median counterclockwise torque and apical force values (p>0.05). Under the present experimental condition, 0.04- and 0.06-tapered EndoWave instruments exhibited different mechanical properties.

The aim of this study was to determine and compare the dimensional changes of polyether and vinyl polyether siloxane impression materials under immersion disinfection with two different disinfectants in three time periods. Impressions were obtained from an edentulous master model. Sodium hypochlorite (5.25%) and glutaraldehyde (2%) were used for disinfection and measurements were done 30 min later after making impression before disinfection, after required disinfection period (10 min), and after 24 h storage at room temperature. Impressions were scanned using 3D scanner with 10 microns accuracy and 3D software was used to evaluate the dimensional changes with superimpositioning. Positive and negative deviations were calculated and compared with master model. There was no significant difference between two elastomeric impression materials (p>0.05). It was concluded that dimensional accuracy and stability of two impression materials were excellent and similar.

The effects of the water concentration in an experimental 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based all-in-one (EX) adhesive were examined on the ability of MDP to remove the smear layer from the ground dentin surface and on the dentin bonding performance. Four types of EX adhesives were prepared by varying the amount of water (46.6, 93.2, 149.8 and 208.1 mg/g), but the MDP concentration was kept a constant at 49.9 mg/g. Scanning electron microscopy and bond strength measurements were performed on the dentin surface demineralized by each EX adhesive. Increased amount of water in the EX adhesive increased the ability of MDP to remove the smear layer. However, the solubilization of the smear layer into the EX adhesive decreased the dentin bond strength. The water concentration in the EX adhesive affected the efficacies of smear layer removal and dentin bonding performance more strongly than the pH value of the EX adhesive.

The acidic monomers utilized in all-in-one adhesives play a key role in the enamel and dentin bonding performance. The purpose of this study is to investigate the mechanism by which 10-methacryloyloxydecyl dihydrogen phosphate (MDP) demineralizes the enamel and dentin surfaces prepared by a diamond bur in three types of experimental MDP-based all-in-one (EX) adhesives containing different amounts of water (46.6, 93.2 and 208.1 mg/g). The enamel and dentin reactants of EX adhesives were analyzed using solidstate phosphorous-31 nuclear magnetic resonance and X-ray diffraction. Increased amount of water led to increases in the efficacy by which MDP demineralizes the enamel and dentin surfaces. However, the rate of calcium salts of MDP produced slowed down at the water concentrations above 93.2 mg/g. The dentin yielded greater amounts of di-calcium salts of the MDP monomer and dimer than the enamel, which develops a different type of layered structure of MDP from the enamel.