This present study investigated the effect of ultraviolet (UV) irradiation on bioactivity of micro-arc oxidized (MAO) titanium surface in vitro by cell culture medium immersion test and interactions with rat-derived mesenchymal stem cells (MSCs). UV-irradiated MAO surface exhibited no obvious changes in surface roughness, morphology, and phase composition when compared with MAO-only surface. However, in cell culture medium immersion test, markedly more bone-like apatite was formed on UV-modified samples than on MAO sample. Rat bone marrow- and adipose tissue-derived MSCs cultured on UV-modified samples displayed accelerated attachment, significant higher levels of alkaline phosphatase (ALP) activity, and up-regulated osteogenesis-related mRNA expression than MAO sample. XPS results provided direct evidence that the amount of basic hydroxyl groups increased with UV irradiation time, which could be one of the key mechanisms underlying their improved bioactivity.

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The present in vitro study sought to determine the effects of myrrh-containing solutions on common suture materials used in periodontal surgery. Three commonly used suture materials (silk, polyglactin 910, polytetrafluoroethylene) were immersed in four thermostatically controlled experimental media to simulate daily oral rinsing activity, namely —artificial saliva, normal saline solution with 0.2% Commiphora myrrh, full-concentration (100%) Commiphora myrrh oil, and a myrrh-containing commercial mouthwash. Tensile strength was measured at the end of each day using an Instron tensile testing machine. Silk sutures were susceptible to tensile strength loss when exposed to 0.2% myrrh solution once daily for 5 days. Myrrh-containing commercial mouthwash had no effect on tensile strength, but all three suture materials lost tensile strength when exposed to 100% myrrh oil. For patients that routinely use myrrh mouthwashes postoperatively, findings of this study suggested that silk sutures might not be the optimal material choice.

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To evaluate the cytotoxicity of resin cements on dental pulp-derived cells (bDPCs), Bifix QM (BQM), Choice 2(C2), RelyX U200(RU200), Maxcem Elite(ME), and Multilink Automix(MA) were tested. The materials were incubated in DMEM for 72 h. A real-time cell analyzer was used to evaluate cell survival. The statistical analyses used were one-way ANOVA and Tukey-Kramer tests. BQM, RU200, and ME demonstrated a significant decrease in the bDPCs’ index at 24 and 72 h (p≤0.001). These materials were found to be the most toxic resin cements, as compared to the control and other tested materials (C2 and MA). However, C2 and MA showed a better survival rate, compared to BQM, RU200, and ME, and had lower cell index than the control group. The cytotoxic effects of resin cements on pulpa should be evaluated during the selection of proper cements.

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This study evaluated the repair bond strength of a nanohybrid resin composite to a novel CAD/CAM hybrid ceramic based on four intraoral ceramic repair systems. Vita Enamic (VE) CAD/CAM hybrid ceramic was used in this study. Specimens were divided into five test groups according to the repair method performed on the ceramic surface: Gr C (No treatment; control); Gr CZ (Cimara Zircon); Gr PR (Porcelain Repair); Gr CR (Clearfil Repair); and Gr CS (CoJet system). Nanohybrid resin composite (GrandioSO) was packed onto treated ceramic surfaces for adhesion testing using microtensile bond strength test. Debonded specimens were examined with a stereomicroscope and SEM to determine the fracture mode. Data were analyzed using ANOVA and Tukey’s HSD test. PR and CZ repair systems significantly enhanced the bond strength of nanohybrid resin composite to VE CAD/CAM hybrid ceramic when compared with the other tested repair systems.

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As a lining or restoration material, flowable composites are popular due to their ease in use and agreeable marginal adaptation of tooth cavity. The purpose of the present study was to evaluate various properties of flowable composites which were claimed to be of high or low flowability by the manufacturers. For the study, twelve flowable composites from six different manufacturers were used. Based on the manufacturers’ claim, they were divided into two groups: high or low flowability. The products grouped in high flowability showed significantly higher (p<0.05) flow rate (flow distance), polymerization shrinkage, and microhardness (on the top surface), regardless of light-curing unit, than those grouped in low flowability. On the other hand, water sorption and solubility showed nonsignificantly different values regardless of flowability. Through the study, flow rate had low correlation with microhardness (R<0.23), polymerization shrinkage (R<0.60), and water sorption and solubility (R<0.36) regardless of light-curing unit.

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This study evaluated the fracture resistance of endodontically treated teeth restored with different base materials and mesioocclusal-distal (MOD) ceramic inlays. Fifty mandibular molars were assigned into five groups (n=10 per group). Group1 (control) comprised intact molar teeth without any treatment. Teeth in other groups were subjected to root canal treatment and restored with MOD ceramic inlays on different base materials. In Group 2, base material was zinc phosphate cement; Group 3’s was glass ionomer cement; Group 4’s was composite resin, and Group 5’s was composite resin reinforced with fiber. Finally, a continuous occlusal load was applied until fracture occurred. Mean fracture resistance of Group 1 (3,027 N) was significantly higher than the other groups (890, 1,070, 1,670, 1,226 N respectively). Fracture resistance of Group 4 was statistically comparable with Group 5 and significantly higher than Groups 2 and 3 (p<0.05; Tukey’s HSD). Use of different base materials under ceramic inlay restorations could affect the fracture resistance of endodontically treated teeth.

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The purpose of this study was to evaluate the effect of remaining dentin thickness (RDT) on the bond strength of current adhesive systems. Third molars were randomly allocated among four groups depending on the adhesive system used: Clearfil SE Bond ONE (SE1), G-Bond PLUS (GB), BeautiBond (BB), and Clearfil Mega Bond (MB). Bonded specimens were stored in water at 37°C for 24 h. Teeth were then sectioned perpendicular to the adhesive interface to produce beams. After measuring RDT of each beam, microtensile bond strength test was carried out using a universal testing machine at a crosshead speed of 1 mm/min. All data were analyzed by linear regression analysis. Bond strengths of one-step self-etch materials used in this study increased with an increase in RDT. In contrast, that of two-step self-etch adhesive system was not affected by RDT.

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This study investigated high-cycle fatigue behavior in three β-Ti wires (TMA, Resolve, Gummetal). Fatigue was evaluated using a static three-point bending test and a high-cycle fatigue test with a three-point bending mode. The surfaces of fractured wires were observed with scanning electron microscopy, and the post-fatigue crystal structures were determined by micro-X-ray diffraction. The Gummetal wire exhibited the lowest elastic modulus, bending strength and fatigue limit, and exhibited the highest resilience of the three types of wire studied. However, no difference in the number of cycles to failure was observed among the three types of wire. The fatigue crack propagation and rapid propagation regions of all wires contained single-phase β-Ti. The elastic modulus and bending strength influenced the fatigue limit, although these properties did not affect the number of cycles to fracture. The three types of β-Ti wires exhibited similar risks of wire fracture.

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The purpose of the present study was to evaluate the mechanical and chemical properties of a novel glass ionomer cement for use as a pit and fissure sealant containing a porous hydroxyapatite, namely, apatite ionomer cement (AIC). Control sealant samples were used Fuji III (GIC-S). The experiment sealant samples (AIC-S) consisted of porous spherical hydroxyapatite (HApS) particles added at 28 wt% to GIC-S powder. The GIC-S and AIC-S samples were evaluated through mechanical strength measurements, scanning electron microscopy observations, energy dispersive X-ray spectroscopy analysis, fluoride ion release tests, and antibacterial tests. The flexural strength of the AIC-S was significantly higher than that of GIC-S for each period, 1 h, 24 h and 1 year. The fluoride release dose for AIC-S was consistently higher than that for GIC-S. In addition, the antibacterial properties of AIC-S were superior to those of GIC-S. The novel AIC-S may be a more suitable sealant material for pits and fissures with intact and/or infected enamel.

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This study evaluated the effects of several low-concentration bleaching products on microtensile bond strength (µTBS) to enamel at different elapsed times after the bleaching treatment. One hundred and fifty bovine incisors were divided into five groups: No treatment, 10% carbamide peroxide (Opalescence), 10% hydrogen peroxide (Opalescence Treswhite Supreme), 3% carbamide peroxide plus lactoperoxidase (WhiteKin), or 3% carbamide peroxide plus 2.7% carbamide peroxide (Clysiden Kit Express). All treatments lasted 4 weeks. After bleaching treatment or non-treatment, teeth were restored immediately, at 1, 3, 7, or 14 days after bleaching and submitted to µTBS test. Data were analyzed by ANOVA and Tukey’s test (p<0.05). For WhiteKin and Clysiden, µTBS to enamel was significantly reduced immediately, at 1, 3 and 7 days after bleaching. At 14 days after bleaching, similar µTBS values were obtained regardless of bleaching product. Therefore, while over-the-counter (OTC) products might affect bond strength to enamel, this effect was no longer observed after 14 days.

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This study assessed methods for evaluation of glass transition temperature (T_g) of autopolymerized hard direct denture reline resins using dynamic mechanical analysis and differential scanning calorimetry in addition to the dynamic mechanical properties. The T_g values of 3 different reline resins were determined using a dynamic viscoelastometer and differential scanning calorimeter, and rheological parameters were also determined. Although all materials exhibited higher storage modulus and loss modulus values, and a lower loss tangent at 37˚C with a higher frequency, the frequency dependence was not large. T_g values obtained by dynamic mechanical analysis were higher than those by differential scanning calorimetry and higher frequency led to higher T_g, while more stable T_g values were also obtained by that method. These results suggest that dynamic mechanical analysis is more advantageous for characterization of autopolymerized hard direct denture reline resins than differential scanning calorimetry.

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The purpose of this study was to evaluate the shear bond strength and durability of 4-META/MMA-TBB resin to human enamel. A self-etching primer that contained 4-META (Teeth Primer, TP) and 35–45% or 60–65% concentrations of phosphoric acid (K-Etchant Gel, KE, and Super Bond C&B Red Activator, RA) were used as the surface treatment agents. A methyl methacrylate (MMA)-based self-polymerizing resin (Super-Bond C&B) was used as a luting agent. The shear bond strength was determined both pre and post thermocycling. The results were statistically analyzed with a non-parametric procedure. The post-thermocycling shear bond strength of the TP group was significantly higher than that of other groups, and that of the KE group was significantly higher compared with the RA group. These results demonstrated that 4-META was effective. Furthermore, when the degree of tooth demineralization was compared, surface treatment with less demineralization using TP was the most effective treatment.

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The purpose of this study was to evaluate the role of 10-methacryloyloxydecyl dihydrogen phosphate (MDP) contained in the bonding resin of a two-step self-etch adhesive system. An experimental adhesive (M0) containing MDP only in the primer, but not in the bonding resin was prepared. Clearfil SE Bond (MM) and M0 were compared in terms of microtensile bond strength to dentin, ultimate tensile strength of the bonding resin, and dentin-resin bonding interface morphology under SEM and TEM. The immediate µTBS values of MM significantly decreased after thermal cycles while M0 were stable even after 10,000 cycles. In the SEM observations, formation of erosion was observed beneath the acid-base resistant zone only in M0. The results suggested that MDP in the bonding resin of the two-step self-etching system; 1) improved the immediate bond strength, but caused reduction in long-term bond durability; 2) offered the advantages of acid-base resistance at the ABRZ forefront area.

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Polymethyl methacrylate (PMMA)-made prostheses used in the oral cavity were evaluated by multimodal assessment in order to elucidate the biodeterioration of PMMA. In used dentures (UD), the micro-Vickers hardness of the polished denture surface and denture basal surface was lower than that of the torn surface (p<0.05), whereas the shaved surface approximately 100 µm from the polished surface showed a similar value to the torn surface. By contrast, there were no differences among these surfaces in new resin (NR). The volatile content of UD was higher than that of NR (p<0.05). Component analysis by ATR-FTIR showed specific spectra (1,700–1,400 cm⁻¹) only in UD. This study revealed that PMMA deteriorated during long-term use in the oral cavity in terms of hardness and volatile content with component alteration, and suggests the involvement of biodeterioration, possibly due to saliva and oral microbiota.

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Fluorine (F) and strontium (Sr) are key elements in the de- and remineralization of teeth. To quantitatively analyze the distribution of F and Sr, micro-particle-induced gamma/X-ray emission (PIGE/PIXE) technique was used. The cavities were prepared and filled with the fluoride- and Sr-containing restorative materials (FSCMs) in extracted human molars. The single-section enamel specimens were prepared by slicing from the buccal to lingual surface including the FSCMs. After 5 weeks of automatic pH cycling, the demineralization was calculated by integrated mineral loss (ΔIML) from transverse-microradiography. The distributions of F and Sr were analyzed by the PIGE/PIXE technique. The micro-PIGE/PIXE technique indicated a fluorine uptake difference between the enamel surface and enamel cavity wall. ΔIML of FSCMs were significantly lower than intact enamel. The micro-PIGE/PIXE technique enables measurement of F and Sr uptake from FSCMs into enamel, which would be beneficial for research on caries development and prevention.

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The aim of this study was to investigate the influence of denture cleansers on surface roughness (Ra, µm) of two hard permanent reline resins and a conventional acrylic denture base resin. Fifty specimens of each material, measuring 10 mm×2 mm were randomly divided into 1 control and 4 experimental subgroups (n=10). Surface roughness values were measured using profilometer before and after immersion in distilled water and in 4 different denture cleansers for 8 h for 140 days. The Kruskal Wallis and Wilcoxon Signed Ranks tests were used for comparison among groups with a significance level of α=0.05. Immersion in denture cleansers significantly increased the surface roughness of reline resins and the difference among the cleansers was statistically significant (p=0.059). Denture cleansers can cause significant surface roughness alterations on hard permanent reline resins and denture base resin where their effect may differ according to the selected resin material.

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The clinical feasibility of a novel device called a Cariotester was investigated by measuring the Knoop hardness (KHN) of white spot lesions diagnosed as ICDAS code 1, 2 or 3. To obtain an equation for converting the Cariotester indentation depth into the KHN, a regression analysis was performed between the depth and measured KHN for human enamel. The Cariotester was then used to measure the indentation depth for white spots (ICDAS code 1, 2 or 3) in extracted teeth, and the KHN values were determined using the above equation. The KHN was 219.9±19.7, 162.4±24.0 and 31.7±17.5 for code 1, 2 and 3 lesions, respectively, which was 30, 49 and 90% lower than that for healthy enamel. Using the formula reported in the literature, the mineral density was calculated to be 87.7 vol.% for healthy enamel, and 75.1, 66.1 and 35.5 vol.% for code 1, 2 and 3 lesions, respectively.

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The purpose of this study is to evaluate the fitting accuracy and fracture resistance of crowns using a hybrid zirconia frame made of both porous and dense zirconia. Commercial semi-sintered zirconia, sintered dense zirconia and sintered hybrid zirconia were used. Sintered zirconia was milled using the CAD/CAM system, and semi-sintered zirconia was milled and sintered to fabricate molar crown frames. Completed frames were veneered with tooth-colored porcelain. The marginal and internal gaps between frames/crowns and abutments were measured. Each crown specimen was subjected to a fracture test. There were no significant differences in marginal and internal gap among all the frames and crowns. The crown with the hybrid zirconia frame had a 31–35% greater fracture load than that with the commercial or dense zirconia frame (p<0.01). This suggests that the all-ceramic crowns with a hybrid zirconia frame have a high fracture resistance.

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Aim of this study was to develop a novel fluorapatite-forming calcium phosphate cement (FA-CPC) with tricalcium silicate (TCS) for endodontic applications and to examine its in vitro and in vivo characteristics. The FA-CPC powder consisted of 62.8% CaHPO₄, 30.8% CaCO₃, and 6.4% NaF. One part of TCS was combined with 9 parts of FA-CPC powder (FA-CPC with TCS). A 1.5 M phosphate solution was used as cement liquid. Setting time (ST), diametral tensile strength (DTS), phase composition by X-ray diffraction (XRD), and cement alkalinity were analyzed. Cement biocompatibility was assessed using rat subcutaneous model. Cement ST was 10.3±0.6 min and DTS was 3.89±0.76 MPa. XRD patterns showed that highly crystalline apatitic material was the only significant phase present and pH value was approximate 11.0. FA-CPC with TCS demonstrated similar biocompatibility as that of mineral trioxide aggregate control. These results suggest that FA-CPC with TCS may be useful for endodontic applications.

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Enamel and dentin particles were added to an experimental 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based one-step adhesive to react for 30 s. After enamel and dentin reactants were analyzed using X-ray diffraction (XRD) and phosphorus-31 nuclear magnetic resonance (³¹P NMR) techniques, curve-fitting analysis was performed on the ³¹P NMR spectra of enamel and dentin reactants. By varying the molar ratio of calcium chloride to MDP, a series of three types of MDP-Ca salts were synthesized. The molecular species of calcium salts of MDP (MDP-Ca salts) produced by decalcification of enamel or dentin were determined based on the XRD and ³¹P NMR analysis results of these three types of synthesized MDP-Ca salts. Curve-fitting analysis showed that enamel and dentin developed several types of MDP-Ca salts and amorphous dicalcium phosphate dihydrate (DCPD) during decalcification. The molecular species of MDP-Ca salts produced by enamel and dentin were mono-calcium salts of MDP monomer and MDP dimer. In addition, dentin produced a di-calcium of MDP dimer.

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