This study evaluated the wear resistance and sealing property of endodontic temporary restoratives by means of functional stressing using a wear simulator. The pulp chamber of 28 extracted molars was opened and filled with cotton, and then the cavity was filled with a temporary material — Caviton, Temporary Pack, Neodyne-α, or TERM. Specimens were subjected to a wear test, and data for wear and dye penetration were analyzed by one-way ANOVA independently (p<0.05) . Wear values of Neodyne-α (0.09±0.05 mm) and TERM (0.24±0.06 mm) were significantly less than those of Caviton (1.79±0.15 mm) and Temporary Pack (1.02±0.40 mm) . In terms of dye penetration, Neodyne-α leaked significantly less than the other materials at 0.40±0.32 mm. On the other hand, there were no significant differences between TERM (1.30±0.57 mm) and Temporary Pack (2.10±0.12 mm) , and between Caviton (2.60±0.41 mm) and Temporary Pack.

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Methyl methacrylate (MMA) is the main component of methyl methacrylic resin, which is widely used in dentistry. Previous studies have investigated whether MMA has any adverse effects on growth and gene expression in mouse fibroblast L929 cells. The present study was designed to further understand the effects of MMA by focusing on cDNA microarray data after L929 cells were exposed to MMA.
MMA was found to inhibit cell growth and induce detoxification response genes in L929 cells. One of the most highly up-regulated genes was glutathione S-transferase, alpha 1 (Ya) (Gsta1) , which has recently been shown to participate in Nrf2 regulation and is considered to be related to detoxification response. Molecular biological data obtained in the present study may therefore provide useful insights into the effects of MMA on living tissue.

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The purpose of this study was to investigate the effect of laser irradiation on the enamel surface spectroscopically. Polished bovine enamel surface was irradiated with an Er:YAG laser apparatus and chemically analyzed using X-ray photoelectron spectroscopy (XPS). XPS detected core electron peaks such as carbon (C 1s) and nitrogen (N 1s), as well as calcium (Ca 2s, Ca 2p, Ca 3s, Ca 3p), phosphorous (P 2s, P 2p), and oxygen (O 1s), from the control enamel surface. After irradiation, XPS revealed that the intensity of C 1s peak slightly decreased while that of N 1s diminished below the detection limit. Detailed C 1s narrow scan spectrum of the Er:YAG laser-irradiated enamel surface showed that C-O/ C-N, C=O/ -CON=, -COO-, and CO₃^2- components, attributed to the specific composition of enamel and any common carbon contamination in surplus, relatively decreased. The binding energies of Ca 2p and P 2p, Δ (Ca 2p, P 2p) , and the Ca/P ratio of lased enamel were found to be different from those of non-lased enamel. It was also shown that Er:YAG laser ablation caused surface alterations to the apatitic inorganic components of tooth tissue.

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Bioresorption and biocompatibility of carbonate apatites, both sintered and non-sintered (S-CAP and N-CAP) , and of sintered β-tricalcium phosphate (β-TCP) were compared by implanting particles of these materials into the back of adult rats. Bioresorption — when evaluated non-destructively with non-decalcified tissues using microfocus X-ray tomography — was essentially the same for N-CAP and β-TCP, while S-CAP exhibited statistically lower bioresorption at 2, 4, and 12 weeks postoperatively. Biocompatibility — when evaluated by ED1 immunostaining — was in the order of β-TCP > N-CAP > S-CAP. The intensity of ED1 immunostaining decreased with time, but persisted longer in β-TCP than in S-CAP and N-CAP, indicating that β-TCP produced the strongest and most enduring stimulation of macrophages. Although no statistical differences were found in tartrate-resistant acid phosphatase (TRAP) staining among the materials at each implantation period, the degree of TRAP staining for S-CAP was statistically greater at 12 weeks than at 2 and 4 weeks, indicating that osteoclast-like cells were in part responsible for the resorption of the carbonate apatite.

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The purpose of this study was to investigate the failure progression process of fiber-reinforced ceramic by finite element (FE) analysis. The three-dimensional FE model for three-point bending simulation was 40 mm long, 4 mm wide, 3 mm thick, and with a span length of 30 mm. Nodal force with load increment of 20 N was applied at the center of the upper surface of the beam. To evaluate matrix fracture and fiber fracture, von Mises criterion and Tsai-Hill criterion were used respectively. Consequently, the stress-deflection curve obtained from FE simulation agreed with that obtained from the experimental testing. Differences in flexural strength and modulus between the analytical and experimental results were 1.3 and -2.9% respectively — demonstrating a close agreement between both results. In conclusion, the FE model applied in the present study was shown to be valid for predicting the failure progression of fiber-reinforced ceramics.

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The present study evaluated the dynamic viscoelastic behavior of commercially available dental composites by a Split Hopkinson pressure bar (SHPB) test machine. Five commercially available composite resins — namely, two conventional hybrid composites (Filtek^TM Z100, Z100; Filtek^TM Z250, Z250) , a packable composite (Filtek^TM P60, P60) , a flowable composite (Filtek^TM Flow, FL) , and a nanofill composite (Filtek^TM Supreme, SU) — were evaluated. By means of SHPB technique, the dynamic stress-strain curve, storage modulus, and loss tangent of the five dental composites were calculated. All specimens exhibited a nonlinear stress-strain curve in the loading process, which resulted not only from the viscoelasticity — but also from the plasticity — of matrix. In terms of storage modulus, no significant differences were exhibited among the five dental composites (p>0.05) . In terms of loss tangent, Z100 showed a significantly higher value than P60, FL, and SU (p<0.05) . Within the limitations of this investigation using SHPB, it was indicated that the loss tangent increased with increasing filler content.

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This study assessed the effect of the molecular structure of newly synthesized methacrylate monomers on their chemical stability in human saliva, whereby these monomers can be used as dental composite resins. Six model monomethacrylates and two urethane-modified BisGMA monomers were added to human saliva, and their change in concentration after 24, 48, and 72 hours were measured by high-performance liquid chromatography. Degradation of the six model monomethacrylate monomers was found to be influenced by the molecular structure, such as steric hindrance and presence of urethane bond in chemical backbone. Based on the degradation test results of these six monomers, urethane-modified BisGMA derivatives — in which the hydroxyl groups in original BisGMA monomer were substituted with alkyl isocyanate — were synthesized and subjected to degradation test. The urethane-modified BisGMA monomers showed a particular resistance to salivary hydrolysis. Results of this study thus suggested that urethane groups should be considered when designing new monomers for dental composite systems as they demonstrated improved resistance to hydrolysis.

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The purpose of this study was to investigate the application of nondestructive testing in cyclic fatigue evaluation of endodontic ProFile^® nickel-titanium (NiTi) rotary instruments. As-received ProFile^® instruments were made to rotate freely in sloped metal blocks by a contra-angle handpiece mounted on a testing machine. Rotation was interrupted periodically, and the instrument removed and engaged onto a device to monitor its stiffness by using two strain gauges in four different directions. This monitoring method has the potential to be developed into a convenient, nondestructive turnkey system that allows in situ assessment of the integrity of NiTi instruments in the clinic. Upon fracture, which was indicated by a change in instrument stiffness, the fractured surface would be examined under a scanning electron microscope. Microscopic evaluation indicated a small area of fatigue fracture with a large area of final ductile fracture, whereby the latter was the major cyclic failure mode. Based on the results of this study, we concluded that a potential nondestructive integrity assessment method for NiTi rotary instruments was developed.

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Adsorption behavior and stabilization/ destabilization effects of 2-hydroxyethyl methacrylate (HEMA) on a bovine tendon collagen (BTC) (type I) , either native (N) or thermally denatured (D) , were studied by IR spectroscopy and differential scanning calorimetry (DSC) . The amount of HEMA adsorbed was larger on BTC (D) than on BTC (N) , because BTC (D) had a larger specific surface area (SSA) as revealed from SSA measurement. Denaturation temperature (T_d) of BTC (N) , measured by DSC in aqueous HEMA solution, decreased from 63°C to 40°C with increasing HEMA concentration (C_HEMA) up to 20 wt%. This destabilization might be caused by the loss of hydrophobic stabilization of the helix structure as C_HEMA was increased. At C_HEMA>20 wt%, the structure of collagen was restabilized presumably due to the dehydration effect conferred by HEMA at higher concentration. BTC (D) with little helix content, however, showed only a weak endothermic peak in the DSC measurement and the T_d at 40°C was independent of C_HEMA.

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The purpose of this study was to evaluate fluoride ion release from a resin-modified glass ionomer cement (Fuji IILC improved, FLC) and a fluoridated resin cement (Panavia F, PF) following different curing methods and storage conditions. The specimens, which were either light-cured (LC) or chemical-cured (CC) , were stored in either distilled water (DW) or demineralizing solution (DS; pH 4.5) for 1, 3, 7, 15, 30, 60, and 90 days. Fluoride ion release was measured using a fluoride ion-specific electrode. Data (n=5) were statistically analyzed using one- and three-way ANOVA (p=0.05) . A “burst effect” was observed in the first week from both materials. However, fluoride ion release from FLC was seven times higher than that from PF. Storage in demineralizing solution accelerated the amount of fluoride release from both materials. In addition, LC yielded a lower amount of fluoride ion release from both materials, as compared to CC. It was concluded that both curing mode and storage medium influenced the amount of fluoride release from the tested materials.

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In this study, cytotoxicity of two different composites with/ without fibers (Adoro/ Vectris and SculpturePlus/ FiberKor) and one nanohybrid composite (Artglass) were investigated and compared. Composites used in the study were prepared as cylindrical discs of 2 mm depth and 8 mm diameter according to ISO 10993 recommendation. Adoro/ Vectris and SculpturePlus/ FiberKor groups were divided into composite, fiber, and composite+fiber groups. Agar diffusion method was employed, and cytotoxicity rankings were determined using lysis index scores. For statistical analysis, Kruskal-Wallis and Mann-Whitney U tests were used. Amongst the composites, Adoro was found to be less cytotoxic than Sculpture Plus and Artglass materials — which were of the same cytotoxicity ranking. Between the fiber and composite materials, the former were found to be more cytotoxic than the latter; in particular, Vectris was found to be more cytotoxic than FiberKor. It was observed that upon combining with the fibers, the cytotoxic effect of the composites increased. This cytotoxicity enhancement was manifested as an additional effect in Adoro/ Vectris group but as a synergistic effect in SculpturePlus/ FiberKor group.

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The purpose of this study was to evaluate the effect of a resin coating technique on the microtensile bond strength (μTBS) of resin cement to dentin in composite crown restorations. Crown preparations were done on human molars. A resin coating material, Hybrid Bond, was immediately applied to the prepared dentin and light-cured, while the tooth without resin coating acted as the control. An impression of the resin-coated tooth was taken, and a composite crown fabricated on the working cast. The composite crown was then bonded with a resin cement, Chemiace II. μTBSs were measured at a cross-head speed of 1 mm/ min, and the resin-coated group yielded significantly higher μTBSs than the non-coated group (p<0.05) . In terms of μTBS values between the axial and occlusal surfaces, no regional differences in resin-dentin bond strength were detected (p<0.05) . It was concluded that resin coating with Hybrid Bond significantly improved the μTBS of resin cement to dentin in composite crown restorations.

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The aim of this study was to develop and evaluate an automatic pH-cycling system, which was intended for performing time-lapse analyses of dental caries. Two single-section specimens prepared from each of the five extracted human incisors were studied under a condition of 3- or 9-cycles/ day for seven weeks. Increase of mineral loss (ΔΔZ) and increase of Ld (ΔLd) were examined and compared at the end of every week during the study. In the 3-cycles/ day condition, ΔΔZ and ΔLd significantly increased only at Week 7. In the 9-cycles/ day condition, ΔΔZ increased significantly from Week 5. ΔLd increased from Week 2, and then there were no further increases for the subsequent five weeks. Based on the results of this study, progression pattern was found to be significantly different between the two conditions. We therefore concluded that the automatic pH-cycling system which we have developed qualified as a model system that simulated the human oral cavity. As such, it could be beneficially employed to clarify the roles of many factors that cause or prevent caries development in human teeth.

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This study aimed to evaluate the bonding behavior of two acrylic resin adhesives joined to titanium-aluminum-niobium (Ti-6Al-7Nb) alloy primed with two metal conditioners. Cast Ti-6Al-7Nb alloy disks were air-abraded with alumina and bonded with six combinations of two resin adhesives (Super-Bond C&B and Multi Bond) and three surface conditions (Alloy Primer, M.L. Primer, and unprimed control) . Shear bond strengths were determined both before and after 20,000 thermal cycles. The tri-n-butylborane initiated Super-Bond C&B resin exhibited greater bond strength than the BPO-amine initiated Multi-Bond resin. Both the Alloy Primer with a hydrophobic phosphate and the M.L. Primer with a phosphonoacetate effectively improved the 24-hour bond strength of Multi-Bond resin as well as the post-thermocycling bond strength of Super-Bond C&B resin.

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The present study examined the effect of the molecular weight of poly (methyl methacrylate) (PMMA) used in PMMA/ MMA-tributylborane (TBB) resin cement on the durability of adhesion to titanium against repeated thermal stress in water. PMMA beads with the same diameter and molecular weights of 1427, 239, 116, 78, and 66 (X10³) were used. Titanium disks bonded to stainless steel or acrylic rods with the PMMA/ MMA-TBB resin were subjected to a thermal cycling test (500 and 2,000 cycles) in water followed by tensile testing. Change in molecular weight of the resin cements collected after thermocycling and tensile testing was examined using size exclusion chromatography (SEC) . The acrylic specimens exhibited a significant decrease in post-thermocycling bond strength as compared to the stainless steel specimens. It was also found that the molecular weight of PMMA powder in PMMA/ MMA-TBB resin had little influence on adhesion durability to titanium. In terms of the molecular weight of resin cements, they decreased and then increased after 500 and 2,000 cycles respectively.

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The purpose of this study was to clarify the stability of benzoyl peroxide (BPO) in some solvents. BPO was dissolved in acetone, acetonitrile (AcCN) , 50% acetonitrile-50% distilled water (50% AcCN) , ethyl alcohol (EtOH) , and methyl alcohol (MeOH) . Solutions containing BPO were incubated for eight days at 25°C. In MeOH, BPO rapidly decomposed into benzoic acid (BA) and methyl benzoate (MeBA) time-dependently, whereas BPO in acetone, AcCN, and 50% AcCN was relatively stable. Although BPO in EtOH was slightly stable within the first 24 hours, it decomposed time-dependently such that BA and EtBA as decomposition products of BPO were produced. These results indicated that the stability of BPO in a solution was dependent on the solvent and the decomposition rate of BPO dissolved in MeOH was the fastest. These suggest that BPO can decompose even in lower-than-activation temperature by the solvent to use for its dissolution.

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The aim of this study was to explore the effect of bleaching agents on the release of metal ions and change in physical and chemical characteristics of amalgams. Amalgam surface changes resulting from bleaching on amalgam were assessed with inductively coupled plasma atomic emission spectrophotometer, an automatic mercury analyzer, a colorimeter, and atomic force microscopy. Analysis of the release of metal ions indicated that the bleaching agent caused more copper, tin, and mercury ions to be released into the immersion solution. Furthermore, metal ion release increased progressively as immersion time was increased from 42 to 84 hours. Morphological examination revealed no significant effects of the 10% carbamide peroxide bleaching agent on the surface morphology of any of the amalgams tested. These results demonstrated that bleaching using 10% carbamide peroxide did not adversely affect the two types of amalgam tested. In other words, a 10% carbamide peroxide bleaching agent can be safely used on a short-term basis in dentist-monitored bleaching of the dental amalgam.

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Third-generation LEDs have high irradiance and efficiency, but the associated temperature rise is potentially hazardous to the pulp of teeth. We evaluated, during composite polymerization, the irradiance and temperature rise of a prototype high-power LED light curing unit (LCU) with optimal pulse width modulation (PWM) , and then compared the results with four off-the-shelf high-power LCUs. A cavity was prepared in a tooth, and a composite resin layer was applied and cured. For each LCU, the irradiance and temperature changes at the pulp-dentin junction were measured. Microhardness (Vickers hardness) of cured composite samples was measured for each LCU. Our prototype had a final temperature of 36.4±1.3°C and irradiance of 1,182±1 mW/ cm². The unit with the highest temperature had a temperature of 48.7±1.2°C and an irradiance of 1,194±1 mW/ cm². Based on the results of the present study, it was shown that PWM technology reduced the curing temperature while retaining the polymerization effectiveness of a high-power LED LCU.

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Commercial Ag-based alloy (46Ag-20Pd-12Au-20Cu alloy) is widely used in Japan as a casting alloy. As opposed to the commercial composition, we prepared five experimental Ag-based alloys with reduced Pd content of 10 or 12%, increased Au content of 20 to 30%, and reduced Cu content of 12 to 20%. We then evaluated their sulfuration resistance by analyzing cast specimen surfaces dipped in 0.1% Na₂S solution with SEM/ EPMA, TF-XRD, and XPS. It became evident that all alloys were susceptible to sulfuration in the segregated Ag-rich Pd-poor phases. The degree and speed of sulfuration, however, differed among the six alloys examined. In particular, one experimental alloy (46Ag-10Pd-30Au-12Cu) possessed a sulfuration resistance equal or superior to that of commercial Ag-based alloy, while the other four experimental alloys were inferior in sulfuration resistance. Based on the results of this study, we concluded that our newly developed 46Ag-10Pd-30Au-12Cu alloy could be employed as a new sulfuration-resistant Ag-based casting alloy - which is especially useful if the price of Pd is skyrocketing again.

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The purpose of this study was to evaluate the microtensile bond strength (MTBS) of a waterless all-in-one adhesive system, Absolute, to dentin. Eighteen human molars were either ground with 600-grit SiC paper or cut with a diamond bur. The following dentin bonding procedures were then performed: dentin surface was kept moist; dentin surface was dried; or dentin surface was dried but equivalent amount of water was added to the adhesive (1:1 by volume). After adhesive curing, a resin composite was incrementally built up. After the specimens were kept in water for one day, MTBSs were measured at a cross-head speed of 1 mm/min. Two-way ANOVA (p=0.05) indicated that the MTBS of the adhesive system was not influenced by surface texture, but enhanced by the presence of water on tooth surface. It was concluded that water is essential to obtaining good dentin bonding for this adhesive system.

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This study assessed the effect of acetic NaF solutions on stainless steel orthodontic brackets. Acetic acid was added to a 0.1% NaF solution to make two solutions, one with pH 3.5 and the other with pH 6. For the two different stainless steel brackets (Tomy, Dentaurum) used in this study, they had a similar elemental composition — except with Mo (molybdenum) in the Tomy bracket. The brackets were then immersed in the prepared test solutions for three days and their responses evaluated. In terms of hydrofluoric acid (HF) concentration, the 0.1%/pH 3.5 solution showed a high HF concentration at 227 ppm, while that of 0.1%/pH 6 solution was very low at 7 ppm. In terms of color change and element release, only the Dentaurum brackets in 0.1%/pH 3.5 solution showed an appreciable color change (ΔE^*=4.0) and released a great amount of elements (Fe, Cr, Ni, Mn) after three days. Otherwise, regardless of pH value and product, only minor color change (ΔE^*<1.0) and negligible element release occurred. In terms of surface modification, no visible changes in surface morphology were observed in any product after immersion in test solutions.

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The purpose of the present study was to investigate the efficacy of four different fluoride etchants in titanium bonding. The etchants were aqueous solutions of 5wt% sodium fluoride (NaF), ammonium fluoride (NH₄F), sodium hydrogen fluoride (NaFHF), and ammonium hydrogen fluoride (NH₄FHF). Cast specimens of commercially pure titanium were air-abraded with alumina, etched for 30 seconds, and then primed with a phosphate primer. An acrylic rod was bonded to the specimen with a tri-n-butylborane-initiated self-curing luting agent. Shear bond strengths were determined before and after 10,000 thermocycles. Regarding pre-thermocycling bond strength, there were no significant differences among the etchants. After thermocycling, there was a decrease in bond strength for all groups. Nonetheless, the bond strengths of NaFHF and NH₄FHF were significantly higher than those of NaF, NH₄F, and non-etched control. In terms of bonding durability between resin and titanium, it was significantly improved when the titanium surface was microscopically roughened with alumina blasting and etching using NaFHF or NH₄FHF.

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Recently, an esthetic tooth coating material has been developed. The material consisted of a primer solution, a base coat, and a top coat. The purpose of this study, therefore, was to evaluate the color change of this tooth coating material and two resin composites after immersion in food-simulating, staining solutions. To this end, the newly developed coating material with and without its top coat, a flowable resin composite, and a hybrid resin composite were employed for the evaluation.
The specimens were subjected to an experimental 24-hour staining cycle: 7-hour immersion in coffee, green tea or red wine, then 17-hour immersion in artificial saliva solution containing 0.3% mucin. After 24 hours, 3 days, 1, 2, and 4 weeks of immersion, the color changes of all specimen surfaces were measured.
Compared with the other materials, the ΔE^* value of coating material without its top coat tended to increase as the immersion period increased until 4 weeks. On the other hand, the ΔE^* value of coating material with its top coat measured the lowest among the materials tested. Based on the results obtained, it was concluded that when using this recently developed tooth coating material in dental clinics, its top coat should be properly applied.

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Non-collagenous proteins in hard tissue matrix are thought to play a pivotal role in regulating the crystal growth of hydroxyapatite (HAp). As most non-collagenous proteins are acidic proteins containing acidic amino acid-rich sequences, we examined the growth of HAp crystals from HAp seed crystals in the presence/ absence of acidic amino acid. New HAp formation generally started from the P-surface of HAp. However, in the presence of acidic amino acid, new HAp formation was observed on both P-surface and C-surface of HAp seed crystals. Furthermore, newly formed HAp showed specific orientation along the long-axis direction of HAp seed crystals. In terms of crystallinity, HAp formed in the presence of acidic amino acid showed low crystallinity. These results suggested that, in biomineralization, the adsorbed or free state of acidic amino acid would influence crystal formation and orientation as follows: 1) If free in solution, acidic amino acid would inhibit HAp crystal growth; 2) If adsorbed or immobilized on matrix, acidic amino acid would become HAp nucleation site and regulate the orientation of HAp crystals.

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This study assessed the plasma and blood concentrations of Cr, Co, and Ni among subjects using removable partial dentures. A comparison was made between subjects with and without RPD treatment history. Control group consisted of 10 healthy individuals without dentures. Concentrations of Cr, Co, and Ni in subjects' plasma and blood were measured with an atomic absorption spectrophotometer. Data were statistically analyzed by ANOVA, and multiple comparison test (α=0.05) was used to identify significant differences between groups. RPD use had a significant effect on the concentrations of Cr (P<0.001) and Ni (P<0.05) in blood and plasma. As such, there were statistically significant differences between the control and study groups for the concentrations of Cr and Ni in blood and plasma. However, RPD use exhibited no significant effect on Co concentration in plasma. In conclusion, the use of removable partial dentures with metal frameworks led to an increase in the concentrations of Cr and Ni in both blood and plasma.

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The purpose of this study was to evaluate the discoloration of two nanohybrids, two microhybrids, and a posterior composite resin restorative material upon exposure to different drinks — namely tea, cola, coffee, red wine, and water. The colors of all specimens before and after storage in the solutions were measured by a colorimeter based on CIE Lab system, and the color differences thereby calculated. Data were analyzed by two-way analysis of variance (ANOVA) and Tukey's HSD test. According to ANOVA, the restorative material, staining agent, and their interaction were found to play a statistically significant role (P=0.0001) in color change. Among the staining agents, water consistently showed the lowest ΔE^* value for all materials, whereas red wine showed the highest ΔE^* value. In other words, for all the materials tested, their color change in staining agents ranked in this increasing order: water < cola < tea < coffee < red wine. In terms of comparison among the five restorative materials, Filtek P60 and Z250 were observed to manifest less color change than the nanohybrids and Quadrant LC.

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The aim of this investigation was to measure the flexural and compressive strengths and the corresponding moduli of cylindrical composite specimens reinforced with woven glass fiber. Test specimens were made by light-curing urethane dimethacrylate oligomer with woven glass fiber of 0.18-mm standard thickness. Tests were conducted using four reinforcement methods and two specimen diameters. Flexural strength and modulus of woven glass fiber-reinforced specimens were significantly greater than those without woven glass fiber (p<0.01). Likewise, compressive strength of reinforced specimens was significantly greater than those without woven glass fiber (p<0.01), except for specimens reinforced with woven glass fiber oriented at a tilt direction in the texture (p>0.05). In terms of comparison between the two specimen diameters, no statistically significant differences in flexural strength and compressive strength (p>0.05) were observed.

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Commercially pure titanium (cpTi) was etched using three concentrated acids: 18% HCl, 43% H₃PO₄, and 48% H₂SO₄. The bond strengths between five types of veneering composite resin and eight cpTi treatments (involving combinations of sandblasting, acid etching in 48% H₂SO₄, and vacuum firing) were determined before and after 10,000 and 20,000 thermal cycles. There were no significant differences in the bond strength of resin to cpTi after etching in 48% H₂SO₄ at 90°C for 15 minutes, at 60°C for 15, 30, or 60 minutes, and after sandblasting with and without vacuum firing (p>0.05); moreover, these treatments yielded the highest values. As for vacuum firing, it had no significant effect on resin bond strength to cpTi before or after 10,000 and 20,000 thermal cycles. We therefore concluded that acid etching in concentrated H₂SO₄ is a simple and effective surface modification method of titanium for bonding to veneering composite resins.

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The purpose of this study was to investigate the possible use of quick heating method for titanium casting using two commercial investments (Rematitan Plus and Tancovest). The resulting characteristics of the investments with the quick heating method were as follows: residual thermal expansion at the casting temperature was in the range of 0.39 to 0.64%; green strength and fired strength ranged from 4.4 to 10.3 MPa and from 13.8 to 17.6 MPa, respectively. Five full crown titanium castings from each casting condition were obtained using an argon arc melting and gas pressure casting machine. The thickness of cast surface reaction layer was approximately 200μm, regardless of heating methods or investments. Further, the heating method did not significantly influence either the accuracy or surface roughness of the titanium castings. These results therefore suggested that these commercial investments for titanium could be used for the quick heating method.

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The purpose of this study was to evaluate the effect of two different ratios of silanized mica filler and milled glass fiber reinforcement on the color of acrylic denture teeth materials. Ten acrylic resin discs made of acrylic denture teeth material (PMMA) obtained from the manufacturer were used as the control group. Four experimental groups were modified from the control group's PMMA material by adding a ratio of 5% or 10% by weight of silane-treated mica filler or milled glass fibers. Each group consisted of 10 specimens. Measurements were performed using a spectrophotometer CM-2600d, and the color changes were characterized in the Commission Internationale d'Eclairage L^*a^*b^* color space. ΔE^* values of 5% mica-, 10% mica-, 5% glass-, and 10% glass-containing sample groups were 2.46, 3.03, 2.16, and 2.59 respectively. There were statistically significant differences in L^*, a^*, and b^* values between the control group and each test group. It was shown that when PMMA denture teeth material was modified with silane-treated mica filler or silane-treated milled glass fibers for the purpose of reinforcement, it would also cause significant changes to the original color of the material.

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