Dental Materials Journal
Online ISSN : 1881-1361
Print ISSN : 0287-4547
ISSN-L : 0287-4547
Advance online publication
Displaying 1-39 of 39 articles from this issue
  • Murat ALKURT, Zeynep YESİL DUYMUS, Şeyma YILDIZ
    Article type: research-article
    Article ID: 2021-002
    Published: 2022
    Advance online publication: May 19, 2022
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    To assess the effect of 10% carbamide peroxide (CP) and 6% hydrogen peroxide (HP) home bleaching agents on the translucency and color of monolithic zirconia. Ninety disc specimens were fabricated (diameter, 10 mm) from multi-layered (ML), ultra translucent multi-layered (UTML), and super translucent multi-layered (STML) zirconia blocks at three thicknesses (0.4,1,1.5 mm) (n=5). The samples were divided into two subgroups, which were treated with 6% HP (45 min per day) or 10% CP (8 h per day) for 14 days. The color of specimens was measured before bleaching (T0) and after bleaching on the third (T3), seventh (T7), and 14th (T14) day. Color (∆E) and translucency (TP) changes were calculated. The thickness varieties used in the samples and the bleaching agent types used created statistically significant differences only in TP and ∆E00, respectively (p<0.05). Bleaching agents can affect TP and ∆E. Patients who have zirconia restorations should be careful when using home bleaching agents.

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  • Suparaksa YAMOCKUL, Niyom THAMRONGANANSKUL
    Article type: research-article
    Article ID: 2021-301
    Published: 2022
    Advance online publication: May 19, 2022
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    The aim of this study was to develop a polishing paste containing ceria to polish lithium disilicate. The samples were prepared, polished with sandpaper using a polishing-machine, the surface roughness (Ra) was measured using a profilometer and randomly divided into 7 groups (n=10). The control group was polished with diamond paste (D). The 6 remaining groups were polished with alumina-ceria paste with different ratios of deionized water:alumina:ceria by weight: 1:0.5:0.5 (AC0.5), 1:0.5:1 (AC1), 1:0.5:1.5 (AC1.5), 1:0.5:2 (AC2), 1:0.5:2.5 (AC2.5) and 1:0.5:3 (AC3). The specimens were polished for 30 s and their Ra values were determined. The surface roughness measurement was repeated after an additional 30 s of polishing until 120 s of polishing had been performed. The Ra values decreased as the ratio of ceria increased. The surface morphology of the samples analyzed using scanning electron microscopy corresponded with their Ra values.

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  • Zhengfan SUN, Xiaoxiao YOU, Jie XU, Long CHEN, Sihui LI, Zhenghao ZHAN ...
    Article type: research-article
    Article ID: 2021-305
    Published: 2022
    Advance online publication: May 19, 2022
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    The study evaluated the effect of sodium hypochlorite (NaOCl) treatment on fluorotic enamel bonding of four adhesive systems. They were Single Bond 2 (SB2), Prime&Bond NT (PBN), Clearfil SE Bond (CSB), and Single Bond Universal (SBU). One hundred eighteen extracted moderate fluorotic molars were divided into eight groups according to NaOCl pretreatment and four adhesive systems. The microshear bond strength (μSBS), etching pattern, and penetration depth (PD) were observed. The statistical method was two-way ANOVA and least significant difference (LSD) test (α=0.05). The application of NaOCl significantly increased the μSBS of PBN and SBU (p<0.05). The enamel-etching pattern of CSB and SBU was deeper under SEM. A noticeable increase of PD was in SB2 and SBU after the application of NaOCl (p<0.05). Pretreatment of 5.25% NaOCl for the 60 s can increase μSBS of PBN and SBU, PD of SB2 and SBU, and improve enamel-etching pattern of CSB and SBU to fluorotic enamel.

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  • Jasmina BIJELIC-DONOVA, Sufyan GAROUSHI, Lippo VJ LASSILA, Giovanni To ...
    Article type: research-article
    Article ID: 2021-321
    Published: 2022
    Advance online publication: May 19, 2022
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    Clinically relevant parameters, such as stress intensity factor of bilayered resin composite structure with short fiber base and its stability over time, has yet to be investigated. This study investigated the stress intensity factor of pre-cracked bilayered specimens composed of short fiber resin composite base (SFC) and particulate filler resin composite (PFC) as veneering layer, with a crack located in the PFC layer, 0.5 mm away from the PFC-SFC interface. Monolayered specimens served as controls. All specimens were stored in water at 37°C either for 1 week, 1 month or 6 months before testing. Two-way ANOVA (p=0.05) was used to determine the differences among the groups. Results indicated that SFC base improve the brittleness of the PFC. The type of short fibers affected the crack propagation; fiber bridging in millimeter-scale SFC was the main crack arresting mechanism, whereas fiber pulling observed in micrometer-scale SFC mainly deviated the crack path.

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  • Yoshihiro YOSHIKAWA, Atsushi TAMURA, Susumu TSUDA, Eisuke DOMAE, Shuny ...
    Article type: research-article
    Article ID: 2021-331
    Published: 2022
    Advance online publication: May 19, 2022
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    Recently, the potential of β-cyclodextrin-thread acid-degradable polyrotaxane (AdPRX) has been emphasized as a therapeutic agent for cholesterol-related metabolic disorders. In this study, we investigated whether carboxymethyl carbamate-modified AdPRX (CMC-AdPRX) can be used for adsorption to calcium phosphate to treat bone diseases. We first synthesized CMC-AdPRX and used it to coat the calcium phosphate plate. RAW264.7 cells were then differentiated into osteoclasts via a receptor activator of nuclear factor-κB ligand, and the number of osteoclasts and the area of absorption lacunae were determined. The number of tartrate-resistant acid phosphatase-positive multinucleated cells was reduced on the CMC-AdPRX-coated plate. The area of the absorption lacunae was smaller with CMC-AdPRX than with AdPRX, which was not carboxy-modified. Our results suggest that CMC-AdPRX can adsorb to calcium phosphate and act on differentiated osteoclasts to suppress their functional expression.

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  • Idris M. MEHDAWI, Ranna KITAGAWA, Haruaki KITAGAWA, Satoshi YAMAGUCHI, ...
    Article type: research-article
    Article ID: 2022-004
    Published: 2022
    Advance online publication: May 19, 2022
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    The aim of this study was to evaluate the maximum amount of chlorhexidine (CHX) that could be incorporated to self-adhesive resin cements to add antibacterial effect without affecting the physical properties. The CHX was incorporated into a commercial self-adhesive resin cement at mass fractions of 0.5–15 wt%, and the CHX-release profile, antibacterial effect, flexural and bond strengths of experimental cements were evaluated. Increasing the CHX content from 5 to 15 wt% resulted in a higher released concentration of CHX. In agar diffusion tests, experimental cements containing 5, 10, and 15 wt% CHX produced inhibition zones against oral bacteria. In flexural strength and shear bond strength to dentin, no significant reduction was observed with the incorporation of 5 wt% CHX. This in vitro study suggests that the addition of 5 wt% CHX yielded an antibacterial self-adhesive cement and had no adverse effect on the flexural and shear bond strengths.

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  • Yuri SHIMADA, Yoshifumi YOSHIDA, Ryosuke ISOGAI, Koutaro MAKI
    Article type: research-article
    Article ID: 2021-330
    Published: 2022
    Advance online publication: May 11, 2022
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    Recently, the number of patients who request esthetically pleasing aligner-type orthodontic appliances (referred to as aligners) has been increasing. However, the orthodontic forces generated by these aligners are still unknown. This study aimed to verify whether the orthodontic force in aligners can be estimated by measuring near infrared 2D birefringence, and to visualize the orthodontic force. We measured the mechanical and photoelastic properties of transparent orthodontic thermoplastic specimens to correlate the optical retardation with the applied load. The results confirmed equivalence between the mechanical properties and the photoelasticity. In addition, the 2D retardation distribution that occurred when stress was applied to the sample was mapped and visualized. This indicates that it is possible to estimate and visualize the orthodontic force using the retardation obtained by near infrared 2D birefringence measurement.

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  • Dan-Yang WANG, Peng WANG, Na XIE, Xi-Zhang YAN, Wen XU, Lu-Ming WANG, ...
    Article type: research-article
    Article ID: 2021-215
    Published: 2022
    Advance online publication: April 29, 2022
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    Self-etch adhesive systems have the advantages of simple operating steps and low technique sensitivity. However, some deficiencies of self-etch adhesive result that the immediate bonding strength between self-etch adhesive and dentine is not so high. Non-thermal atmospheric pressure plasma (NTAPP) can be used for surface modification. Previous studies of our research group have proven that NTAPP can improve bonding durability between dentine and etch-and-rinse adhesive. However, it is still unknown whether NTAPP can improve bonding strength between dentine and self-etch adhesive. The study observed the contact angle on dentine surface, the adhesive permeability and MTBS. The study proved that NTAPP can improve dentine surface wettability, clear up smear layer, and enhanced the self-etch adhesive permeability in dentine bonding interface. In conclusion, NTAPP could improve the bonding strength between dentine and self-etch adhesive systems. The most optimum treating time was 15 s.

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  • Junko IIZUKA, Yuichi KUNIMATSU, Yuko MIKUNI-TAKAGAKI, Yoshiharu MUKAI
    Article type: research-article
    Article ID: 2021-229
    Published: 2022
    Advance online publication: April 29, 2022
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    The aim of this study was to investigate the mineral-promoting effects of in-office bleaching agent on enamel subsurface lesions. Enamel subsurface lesions were divided into following groups; D: demineralized samples without any further treatment, DS: samples were further immersed in fresh saliva, DSR: samples were immersed in saliva followed by remineralization buffer, and DSBR: samples were immersed in saliva, subjected to in-office bleaching, and then immersed in remineralization buffer. The control group (CONT) consisted of untreated enamel specimens. Transverse microradiography showed that integrated mineral loss was significantly lower in the DSBR group than in the DSR group. Confocal laser Raman analysis revealed that ν1 phosphate peak height of 959 cm−1 and mineral to matrix ratio of peak heights 959 cm−1 to 1,610 cm−1 in the DSBR group were similar to those in the CONT. In-office bleaching can promote enamel remineralization by altering or removing proteins infiltrated to enamel subsurface lesions.

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  • Masao KUROSAKA, Yu KATAOKA, Takashi MIYAZAKI
    Article type: research-article
    Article ID: 2021-231
    Published: 2022
    Advance online publication: April 29, 2022
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    The fixation of titanium implants in bone tissue is affected by the presence of a passive titanium oxide (TiO2) layer. Specifically, oxidation products in the amorphous TiO2 matrix enhance the mechanical properties of mineralized tissues. In addition, in vitro mineralization mediated by primary osteoblasts on amorphous TiO2 generates stiff tissues in a process that resembles pathological mechanisms connected with tumors and proceeds through hydrogen peroxide-inducible clone-5 (Hic-5) expression. However, the relationship between surface-based peroxidation and stiff mineralized tissue formation remains unclear. In this study, titanium samples were processed using wire electrical discharge machining to generate oxidation products in amorphous TiO2. The gene expression profiles of primary osteoblasts cultured on these specimens were characterized. Increased expression of Hic-5 was correlated with the presence of peroxidation products. The crystallization of amorphous TiO2 in these samples reduced the expression of both Hic-5 and lysyl oxidase, an enzyme that promotes matrix cross-linking.

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  • Aya KASAKAWA, Shinichi SEKINE, Kenji TANAKA, Jumpei MURAKAMI, Sota KON ...
    Article type: research-article
    Article ID: 2021-281
    Published: 2022
    Advance online publication: April 29, 2022
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    The use of Q-switched erbium:yttrium-aluminum-garnet laser (Er:YAG laser), which have much less thermal effects than conventional Er:YAG lasers, has been proposed mainly in the medical field. The purpose of this study was to evaluate the bonding ability of dentin after Q-switched Er:YAG laser irradiation.The effects of dentin irradiation with Q-switched and conventional lasers were evaluated in terms of dentin morphology, roughness, hardness, elemental content, and resin bonding strength. Q-switched Er:YAG laser at average power densities of 20, 40, and 60 W/cm2 and conventional Er:YAG laser at 909 W/cm2 were used, and their performance was compared with that of the untreated group. Significant differences (p<0.05) were observed between 20 W/cm2 and the other groups in term of surface roughness and surface hardness. The resin adhesion of the 20 W/cm2 group was significantly higher than that of the other groups (p<0.05).

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  • Longqiang YANG, Tadashi MIURA, Masataka KASAHARA
    Article type: research-article
    Article ID: 2021-136
    Published: 2022
    Advance online publication: April 13, 2022
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    Atelocollagen-gelatin (ACG) sponge was fabricated from atelocollagen and gelatin by lyophilization without introducing toxic substances. This study aimed to investigate the effects of heat treatment on the 3-dimensional structural stability of ACG sponge biomaterial. ACG sponge samples were fabricated and heat treated at 125oC for 12 h in the vacuum. The results revealed that heat treatment did not affect porosity, pore size and mechanical compressive strength. Heat-treated ACG sponge showed decreased absorbance and peak shift of amid I (C=O) stretches, slightly higher water uptake degree and significantly decreased in vitro degradation rate. Moreover, heat-treated ACG sponge maintained good 3-dimensional surface morphology and porous microstructure throughout 7 days, while non-heat-treated ACG sponge collapsed in less than 24 h. The human mesenchymal stromal cells (hMSCs) were shown to adhere and grow well on heat-treated ACG sponges. These results indicate that heat treatment is effective and safe to stabilize 3-dimensional ACG sponge biomaterial for tissue engineering.

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  • Kei TAKAHASHI, Tomohiro YOSHIYAMA, Akihito YOKOYAMA, Yasushi SHIMADA, ...
    Article type: research-article
    Article ID: 2021-268
    Published: 2022
    Advance online publication: April 13, 2022
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    The aim of this study was to evaluate the effect of decontamination agents against saliva contamination on the bonding of computer-aided design/computer-aided manufacturing (CAD/CAM) resin block. Three commercially available decontamination agents were used in this study. The samples were subjected to microtensile bond strength test. A saliva protein staining test was performed by the pigment binding method to investigate the effect of removing saliva protein. All the decontamination agents could significantly restore the bond strength from the saliva contamination, and KATANA Cleaner showed no significant difference with the control. From the results of the saliva protein staining test, KATANA Cleaner showed higher removal effect of saliva protein for CAD/CAM resin block surface than the other materials due to the surface active effect of MDP salt. It was suggested that cleaners containing MDP salt were more effective in removing artificial saliva contamination than cleaners containing other ingredients for CAD/CAM resin blocks.

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  • Kensuke TAKAKUSAKI, Natsuko MURAKAMI, Junichiro WADA, Taihei KASAI, Hi ...
    Article type: research-article
    Article ID: 2021-328
    Published: 2022
    Advance online publication: April 13, 2022
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    This study aimed to evaluate the effect of retention hole designs in artificial teeth on failure resistance of the connection with a thermoplastic denture base resin. Artificial teeth with the following retention hole designs were attached to polyester and polyamide resins: no hole, vertical hole, horizontal hole, and vertical and horizontal holes. An artificial tooth with no hole attached to polymethyl methacrylate was prepared as the control. The load was applied until connection failure occurred between the artificial tooth and resin, and failure resistance was detected. Although the control showed the highest resistance, the artificial tooth with vertical and horizontal holes showed higher resistance than those with other retention hole designs in both thermoplastic resins. Providing vertical and horizontal retention holes in artificial teeth may be effective in improving failure resistance of the connection with thermoplastic resins.

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  • Thomas STOCKER, Haoyan LI, Elias P. BAMIDIS, Uwe BAUMERT, Lea HOFFMANN ...
    Article type: research-article
    Article ID: 2021-112
    Published: 2022
    Advance online publication: April 01, 2022
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    The aim of the present work was measuring the effect of varying normal forces on frictional forces applied to different bracket types in combination with archwires made of NiTi and stainless steel of variable cross section. The measurements were carried out in artificial saliva. Three-way ANOVA and Bonferroni post-hoc tests (α=0.05) were applied. Except for one subgroup the combination of normal force, bracket system and wire dimension had significant effect on friction (p<0.001) as friction increased with increasing normal forces. Only moderately tied ligatures or passive self-ligating brackets generate low friction forces. There was a statistically significant order (0.016"×0.022"<0.018"×0.025"<0.019"×0.025") for stainless steel wire material. Finite element modeling simulation showed the increasing effect of active clip force on friction especially for 0.025" wire profiles. If compared to NiTi wires, stainless steel archwires delivered higher friction. Combinations between wire-type and ligation should be chosen carefully for the intended treatment step.

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  • Bruna L. PORTO, Fabíola J. BARBON, Cristina P. ISOLAN, Alexandre L. BO ...
    Article type: research-article
    Article ID: 2021-246
    Published: 2022
    Advance online publication: April 01, 2022
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    This study investigated the effect of ultrasound application when luting ceramic using two preheated composites that show distinct responses to preheating at 69°C: Filtek Z100 and Z350XT. RelyX Veneer was the control. Feldspar disks were luted using the resin-based luting agents (RBLAs), and ultrasound was tested. Biaxial flexure strength (σbf) was calculated at z-axial positions of the luted disks (z=0; z=−t2). Microtensile bond strength (μTBS) to ceramic was tested (n=30). Data were analyzed at α=0.05. At z=0, the σbf was higher for Z350 when ultrasound was not used. When ultrasound was applied, the σbf was similar between Z350 and Z100. At z=−t2, differences across the RBLAs were observed: Z350 was superior than Z100 and control without ultrasound. Ultrasound increased σbf for Z100 at both axial positions. The preheated composites yielded higher μTBS than the control. Ultrasonication increased the mechanical performance of ceramic luted with Z100 without influencing the film thickness.

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  • Woorham HAN, Jae-Hoon KIM, Ho-Beom KWON, Jeong-Kil PARK, Deog-Gyu SEO
    Article type: research-article
    Article ID: 2021-306
    Published: 2022
    Advance online publication: April 01, 2022
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    This study aimed to evaluate the stress distribution that results from temperature changes in teeth restored with gold inlay and to predict the fatigue life of the teeth. A thermal load regimen for finite element analysis (FEA) was established in an in vivo experiment, in which participants with gold inlays drank hot and cold water. An extracted human maxillary molar was converted into a 3D FEA model. The tooth models with Class I and II preparations were restored with gold inlay in the experimental groups. The stress distribution was analyzed under the thermal loads. Also, lifetime prediction was conducted using Basquin’s formulation. The gold inlay groups showed a higher stress distribution than the preparation-only groups regardless of the type of preparation. The Class II gold inlay group showed the shortest fatigue life of 2.48×1011 cycles, whereas the Class I preparation group showed the longest fatigue life of 4.49×1016 cycles.

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  • Yurie TAKARA, Shugo HAGA, Hitoshi KIMURA, Koutaro MAKI
    Article type: research-article
    Article ID: 2021-176
    Published: 2022
    Advance online publication: March 24, 2022
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    It is difficult to control corrective forces in orthodontic treatment with clear aligners. The grip of aligners on teeth is important to ensure accurate corrective forces from aligners. This study aimed to measure the gripping force of aligners under various conditions to clarify factors that influence it. We created aligners with different attachment morphologies and placement sites and different margin lengths. We developed a device to measure the mechanics involved in the removal of these aligners. The gripping force was evaluated at five different aligner removal sites on the teeth. We found that the gripping force of the aligner was the weakest on the lingual side of the first molar and strongest on the labial side of the central incisors and that the attachment morphology and placement sites affected the gripping force of aligners.

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  • Xin-Rong MA, Xiao-Ming ZHU, Jing LI, Xuan QI, He-Ping LI, Jianguo TAN
    Article type: research-article
    Article ID: 2021-207
    Published: 2022
    Advance online publication: March 24, 2022
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    The aim of this study was to evaluate the crosslinking effect of the radio-frequency atmospheric-pressure glow discharge (RF-APGD) plasma jet treatment on dentin collagen. The dentin collagen was treated by an RF-APGD plasma jet with the gas temperature of 4°C under different treatment times, while the control was a non-treatment group. The dentin collagen was characterized in terms of atomic force microscopy-based nanoindentation, differential scanning calorimeter, Raman analysis and X-ray photoelectron spectroscopy (XPS) measurement. The crosslinking effect of the plasma-treated dentin collagen was found compared to that of the control group. The elastic modulus and denaturation temperature of the dentin collagen after plasma treatment for 30 s were significantly higher than those in the control group (p<0.05). The RF-APGD plasma jet treatment can promote the crosslinking of the dentin collagen, which is of great significance to improve its mechanical and thermal stabilities.

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  • Haochen GAO, Kuikui GE, Yuqiang XU, Yihan WANG, Min LU, Yibo WEI, Qian ...
    Article type: research-article
    Article ID: 2021-217
    Published: 2022
    Advance online publication: March 24, 2022
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    The aim was to obtain bone repair materials with sustained release of minocycline and evaluate the effect in periodontal bone defect repair. Two complex material, hydroxyapatite/chitosan (HA/CS) and minocycline-hydroxyapatite/chitosan (Mino-HA/CS), were prepared by the co-precipitation method. The physical and chemical property, cytotoxicity, release of minocycline and the bacteriostasis examination of the materials were evaluated, they were applied to the rabbit model of mandible bone defect to evaluate their effects on the regeneration of periodontal bone defect. After minocycline was added to HA/CS, the setting time of the material was prolonged, the compressive strength was reduced and the pore size and porosity were increased significantly. The pH value did not change obviously and stayed in the neutral range. Mino-HA/CS could promote the growth of osteoblasts effectively compared with control medium. In vivo, Mino-HA/CS material showed better effect of promoting periodontal bone formation.

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  • Kei KYOGOKU, Tomoko SOMEYA, Masaaki KASAHARA, Koji HASEGAWA, Shinji TA ...
    Article type: research-article
    Article ID: 2021-287
    Published: 2022
    Advance online publication: March 24, 2022
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    This study aimed to clarify the effects of vertical bone defect width and a ferrule on fracture of the fragments of fractured tooth reattached with adhesive resin cement (reattached tooth). The reattached tooth was built up by a fiber post and composite resin core for abutment and formed to the abutment with or without a ferrule. The vertical bone defect was fabricated with a V-shaped defect in different widths. The fracture load was evaluated using a universal testing machine. The vertical bone defect did not affect the fracture load, but a ferrule increased the root fracture load. For the specimens without a ferrule, debonding between the composite resin core and the root at the coronal loading side and fractures at the apical side of the root were found. In conclusion, the ferrule at abutment could affect fracture load and modes, and the bone defect width did not.

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  • Mone SHOJI, Hiroyasu KUROKAWA, Nao TAKAHASHI, Runa SUGIMURA, Toshiki T ...
    Article type: research-article
    Article ID: 2021-318
    Published: 2022
    Advance online publication: March 24, 2022
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    The purpose of this study was to investigate the protective effect of a glass ionomer cement (GIC) consisting of fluoro-zinc-silicate glass on the demineralization of bovine dentin using the ultrasonic pulse-echo method. The findings were compared with those obtained using a conventional GIC. Slabs of dentin from bovine teeth were sliced, shaped into a rectangular form, and immersed in 0.5 M ethylenediaminetetraacetic acid solution at 25ºC for 6 days, followed by storage in distilled water for 3 days. After demineralization, they were immersed in artificial saliva with and without the GIC specimens. The propagation times of the longitudinal ultrasonic waves in the samples were measured. The ultrasonic velocities of the fluoro-zinc-silicate glass-containing GICs were significantly increased 2–3 days after the start of the experiment and showed an upward trend thereafter. These findings indicate that the GICs containing fluoro-zinc-silicate glass might exhibit the potential to promote remineralization in the dentin.

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  • Yuka YOKOYAMA-SATO, Takashi NISHIOKA, Yukihiro NAGANUMA, Masatoshi TAK ...
    Article type: research-article
    Article ID: 2021-234
    Published: 2022
    Advance online publication: March 10, 2022
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    The aim of this study was to assess the utility of an actuator-driven pulsed water jet (ADPJ) as a hardness-dependent carious dentin removal device by using different outputs. Thirty-six plane surface dental caries samples were treated with the ADPJ at 150, 200, and 250 voltage (12 teeth each). The Knoop hardness number (KHN) and Ca/P mass ratio were measured at 70 μm from the deepest point of the removing groove. Furthermore, three other teeth samples were manually treated with the ADPJ at the three above mentioned voltages (one tooth each) for 1 min. The KHN and Ca/P mass ratio were measured at 70 μm from the surface of the residual dentin part. In both the KHN and Ca/P mass ratio, higher residual dentin depended on the applied voltage of ADPJ. The ADPJ enabled the removal of softened carious dentin in an applied voltage-dependent manner.

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  • Mariko NAKAI, Koichi IMAI, Yoshiya HASHIMOTO
    Article type: research-article
    Article ID: 2021-261
    Published: 2022
    Advance online publication: March 10, 2022
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    Resin blocks and ceramic blocks for CAD/CAM crowns were cut into powders and separated into three particle size groups. Oxidative stress and cell viability were measured in 3T3 and FRSK cells. The results of cytotoxicity tended to be slightly higher for resin than for ceramics. The values also increased as the particle size decreased in the powders. In addition, incorporation into cells was frequently observed under SEM, suggesting that the particle size of easily incorporated dust is different among cell types. Fluorescence-activated cell sorter (FACS) showed an increase in apoptosis and a decrease in cell viability in most of the sample groups compared to the control group. Hematoxylin and eosin staining of the cells showed deep staining of the nuclei in the sample groups. It was found that oxidative stress cell viability and apoptosis appeared differently depending on the size of the particles and the type of cells.

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  • Jumpei TOKUNAGA, Hiroshi IKEDA, Yuki NAGAMATSU, Shuji AWANO, Hiroshi S ...
    Article type: research-article
    Article ID: 2021-299
    Published: 2022
    Advance online publication: March 10, 2022
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    This study aimed to develop a novel polymer-infiltrated ceramic network (PICN) composite fabricated via a slip-casting method for a dental training model tooth with machinability compatible to human enamel. A PICN model tooth comprised of silica/acrylic-resin was fabricated via the slip-casting method. A commercial resin-based model tooth and human enamel were used as the control sample. The samples were evaluated based on Vickers hardness, inorganic contents, density, and machinability. The machinability was characterized by a grinding amount obtained from the grinding test using a device equipped with a dental micromotor handpiece with a diamond bur. The properties of the PICN model tooth yielded a silica content of 84.7% and a density of 1.99 g/cm3, and its Vickers hardness (312) was comparable with that of enamel (348). The grinding amount was comparable with that of enamel. The castable PICN model tooth was compatible to enamel in terms of hardness and machinability.

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  • Tadashi YOKOYAMA, Koichi IMAI, Yoshiya HASHIMOTO
    Article type: research-article
    Article ID: 2021-302
    Published: 2022
    Advance online publication: March 10, 2022
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    The study was done to compare cell viability between ES-D3 and Balb/c 3T3 cells, and evaluate the difference in cell viability between these cell lines using denture-base lining materials for prosthetic dentistry. To compare the cytotoxicity, three acrylic and three silicone dental materials were used. The cell viability was examined by MTT and lactate dehydrogenase (LDH) methods. The cell viability immediately after malaxation or light irradiation was lower only for the acrylic materials in 3T3 cells, and for both silicone and acrylic materials in ES-D3 cells. However, the cell viability determined 24 h after malaxation or light irradiation by the MTT and LDH methods did not significantly differ between samples. It was observed that ES-D3 cells are more sensitive depending on the type of material. The results suggest that ES-D3 cells can be used as in vitro systems for conducting biosafety assessment to predict embryotoxicity.

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  • Yuta MATSUKI, Hiroko SATO, Noboru KAJIMOTO, Emi UYAMA, Shinya HORIUCHI ...
    Article type: research-article
    Article ID: 2021-322
    Published: 2022
    Advance online publication: March 10, 2022
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    Advancements in dental cements have considerably improved their bond strengths. However, high bond strength often makes the removal of restorations difficult. Thus, smart dental cements that show controllable bond strength are required. A conventional resin-modified glass-ionomer-cement demonstrated a significant reduction in the bond strength after current application. However, for this system, the ions in the cement are released into the oral cavity, resulting in a reduction of the electrical conductivity and in losses of the expected on-demand debonding property. Herein, the effects of immersion in 0.9 and 15% NaCl solutions on the electrical conductivity and debonding properties were investigated. The cement immersed in 0.9% NaCl solution from 1 to 28 days maintained similar bond strength reductions after current application, whereas that in 15% NaCl solution initially showed no bond strength reduction after 1 day but exhibited an increase in the bond strength reduction after immersion for 28 days.

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  • Keiichiro UCHIKURA, Natsuko MURAKAMI, Toshiki YAMAZAKI, Huaxin LYU, Ko ...
    Article type: research-article
    Article ID: 2021-224
    Published: 2022
    Advance online publication: March 04, 2022
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    To evaluate the fracture resistance of computer-aided design and computer-assisted manufacturing restorations as the abutment of removable partial dentures, experimental blocks, with the rest seat made of feldspar, hybrid resin composite, lithium disilicate glass ceramic, or zirconia, were subjected to loading by a metallic occlusal rest. The rest contacted the rest seat with an accurate fit and two mismatch contact conditions: bottom and sidewall contact. Zirconia exhibited the highest fracture load, and the fracture load of the accurate fit was significantly higher than that of the sidewall contact (p<0.05) and insignificantly higher than that of the bottom contact (p>0.05). A finite element analysis of the sidewall contact revealed a higher tensile stress concentration at the bottom of the rest seat than the other contact conditions. The mismatch between the rest and the restoration reduced fracture resistance, while zirconia as the abutment withstood the average occlusal force of the posterior region.

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  • Rong WANG, Tyler STANLEY, Xiaomei YAO, Hang LIU, Yong WANG
    Article type: research-article
    Article ID: 2021-247
    Published: 2022
    Advance online publication: March 04, 2022
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    Due to its low tolerance to external factors such as enzymes, dentin collagen often requires stabilization, which can be achieved through cross-linking. In this study, qualitative and quantitative Fourier transform infrared (FTIR) analyses were used to assess dentin collagen stabilization effects of three structurally-different flavonoids —A-type linkage proanthocyanidins (A-PA), B-type linkage proanthocyanidins (B-PA), and epigallocatechin gallate (EGCG), all from natural extracts. Particularly, transmission FTIR spectroscopy was used for the first time to quantitatively assess the biodegradation of fresh ultra-thin (10 µm) dentin collagen films caused by collagenase digestion. Two traditional analytical methods, namely the hydroxyproline assay and weight loss analysis, were also used for comparison purposes. The results from all three methods showed consistently that A-PA and B-PA provide better collagen stabilization than EGCG at concentrations of 0.65% and 1.3% (p<0.01). FTIR is demonstrated to be a valuable and reliable analytical tool for qualitative and quantitative evaluation of ultra-thin collagen films.

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  • Chun FAN, Zhiyuan LI, Qiuxia JI, Hui SUN, Ye LIANG, Pishan YANG
    Article type: research-article
    Article ID: 2021-250
    Published: 2022
    Advance online publication: March 04, 2022
    JOURNAL FREE ACCESS ADVANCE PUBLICATION

    Human periodontal ligament stem cells (hPDLSCs) are seeding cells for tissue-engineered treatment of alveolar bone regeneration. To elucidate carboxymethyl chitosan (CMCTS) and carboxymethyl chitin (CMCT) effect on osteogenic differentiation, hPDLSCs were isolated and treated with CMCTS or CMCT. Cell viability and multiplication capacity were measured. The expression of classic osteogenic related molecules, including Alkaline Phosphatase (ALP), Phosphoprotein 1 (OPN), RUNX family transcription factor 2 (Runx2) and Osteocalcin (OCN), were determined. Mineralization levels were detected by Alizarin Red staining. Results showed that both CMCTS and CMCT treatment had the maximal promoting ability for hPDLSCs viability below the concentration of 100 μg/mL, while CMCTS improved hPDLSCs mineralization significantly. CMCTS induced multiple-factor high expression, including ALP, Runx2, OPN and OCN, whereas slightly osteoinductive bioactivity of CMCT was mainly due to ALP. Therefore, CMCTS had a more significant advantage for osteoinductive differentiation of hPDLSCs than CMCT, which may be a promising material for periodontal regeneration.

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  • Yusuke TAKARABE, Masahiro TO, Noriyuki HOSHI, Tohru HAYAKAWA, Chikahir ...
    Article type: research-article
    Article ID: 2021-276
    Published: 2022
    Advance online publication: March 04, 2022
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    Pure titanium is widely used as a material in dental implants. However, it possesses inferior mechanical strength. This study aimed to elucidate the efficacy of acid treated multi-directionally forged (MDF) pure titanium in vivo. We verified the temporal changes until osseointegration in beagle dogs. Using two types of experimental materials (conventional pure titanium or MDF pure titanium), new bone formation was assessed using morphological examinations, and the bone-to-implant contact (BIC) value was evaluated at each time point (14, 30, and 90 days after the operation). As such, new bone formation was observed around the acid-etched MDF group, in which the BIC value was highest, followed by that in the acid-etched pure titanium group. MDF pure titanium implants showed early promotion of new bone formation compared to conventional titanium implants. The new acid-treated MDF made of pure titanium could be applied to humans in the future to prove its practicality.

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  • Hiromitsu SATO, Peng CHEN, Maki ASHIDA, Yusuke TSUTSUMI, Hiroyuki HARA ...
    Article type: research-article
    Article ID: 2021-169
    Published: 2022
    Advance online publication: February 09, 2022
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    The cytocompatibility and osteoconductivity of the Zr-14Nb-5Ta-1Mo alloy were investigated using a mouse osteoblastic cell line (MC3T3-E1) to promote the application of this newly developed alloy in dental/medical treatment. The initial cell-attached morphology was visualized by fluorescent staining, and cells cultured on the Zr alloy showed similar cell adhesion behavior to cells cultured on titanium (Ti). In our 5-day proliferation investigation, similar cell numbers were obtained with both Zr alloy and Ti. These results indicate that the cytocompatibility of Zr alloy is similar to that of Ti. In addition, the similar results in the evaluation of alkaline phosphatase (ALP) activity and staining of deposited calcium using alizarin red S with both Zr alloy and Ti indicated that the osteoconductivity of the Zr alloy is similar to that of Ti. Our results prove the good cytocompatibility and osteoconductivity of the Zr-14Nb-5Ta-1Mo alloy, enabling its promotion for use in dental/medical applications.

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  • Aline Garcia HALLAK, Ricardo Armini CALDAS, Isaias Donizeti SILVA, Mil ...
    Article type: research-article
    Article ID: 2021-245
    Published: 2022
    Advance online publication: February 09, 2022
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    This study evaluated stresses generated at maxillary central incisor (21) root restored with lithium disilicate crown (LDC), and glass fiber (GFP) or polyetheretherketone (PEEK) post. 3D models created by computed tomographic image (i-CAT Cone Beam 3D Dental Imaging System) reproduced maxillary central incisor. Each model had prosthetic LDCs (2.0 mm thick) cemented to GFP or PEEK posts with dual resin cement. Different loads were applied to each model (cervical, incisal, axial, middle). At maximum principal stress, PEEK showed higher stress than GFP in all loads, but with qualitative similarity. At minimum principal stress, PEEK and GFP showed qualitative and quantitative similarities, except axial load. Maxillary central incisor restored with GFP or PEEK and LDC presented, in general, similar stress intensity and distribution for main occlusal loads. Only two of sixteen occlusal loads tested (cervical for maximum principal; axial for minimum principal) showed significant quantitative difference.

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  • Masao IRIE, Masahiro OKADA, Akio YOSHIMOTO, Yukinori MARUO, Goro NISHI ...
    Article type: research-article
    Article ID: 2021-278
    Published: 2022
    Advance online publication: February 09, 2022
    JOURNAL FREE ACCESS ADVANCE PUBLICATION

    We sought to compare the bond strength of resin cement on moist dentin to that on dry dentin, and determine the relationship between the bond strength and flexural strength of resin cement. The water content of the moist and dry dentins was estimated using infrared spectroscopy. Four adhesive and three self-adhesive resin cements were used. At three times of immediately, after one-day storage, and after 20,000 thermocycles (TC 20k), the shear bond strengths were measured. For all resin cements, both the shear bond strength and the flexural strength were the lowest immediately after setting; however, after one day of water storage or TC 20k, these resin cements had the highest values. Regardless of the condition of the dentin surface upon shear bond strength, the flexural strength of each resin cement was correlated with the shear bond strength of the dentin surface.

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  • Ryota MARUO, Hidemasa SHIMPO, Katsuhiko KIMOTO, Tohru HAYAKAWA, Hiromi ...
    Article type: research-article
    Article ID: 2021-285
    Published: 2022
    Advance online publication: February 09, 2022
    JOURNAL FREE ACCESS ADVANCE PUBLICATION

    Since cast titanium prostheses have many drawbacks, multi-directionally forged titanium grade 2 (MDF) was developed, and the application of the milling process was proposed for improving the titanium clasp. This in vitro study evaluated milled titanium clasps, including MDF titanium. Milling clasps were manufactured with commercially pure (CP) titanium grade 2 (CP 2), grade 4 (CP 4), Ti-6-Al-4V, and MDF. As a control, a CP 2 cast titanium clasp was fabricated in the conventional manner. No porosities and catastrophic failures were observed in the four milled titanium clasps. Fitness accuracy and retentive forces of milled CP 2 and CP 4 tended to be worse, and the milled MDF showed the higher retentive forces (12.45 N) than did cast and milled CP 2 clasps (9.32 N and 4.42 N). Milled titanium clasps can be recommended for longer-term clinical use as compared to cast clasps.

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  • Yuan LI, Jing ZHAO, Zhe SUN, Nengjie LIN, Yuanna ZHENG
    Article type: research-article
    Article ID: 2021-236
    Published: 2022
    Advance online publication: January 29, 2022
    JOURNAL FREE ACCESS ADVANCE PUBLICATION

    This study evaluated the 3-dimensional (3D) fit of self-glazed zirconia monolithic crowns fabricated by wet deposition, in comparison with milled zirconia and lithium disilicate monolithic crowns. Dual-scan protocol was used to assess the fit of crowns. Root mean squares (RMS) and uniformity index (UI) were calculated to describe the gap size and uniformity. The self-glazed zirconia crowns had significantly lower RMS values for the gaps at axial wall and transition regions than the milled zirconia crowns, and for the gaps at occlusal region than both milled crowns. All 3 types of crowns had comparable RMS values for the gaps at marginal and chamfer regions and comparable UI values for both marginal and internal gaps. The 3D fit of the self-glazed zirconia monolithic crowns was clinically acceptable and they exhibited better fit at occlusal region than the milled crowns.

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  • Hitomi KIMURA, Hiroki TSUKA, Koji MORITA, Isao HIRATA, Fumiko NISHIO, ...
    Article type: research-article
    Article ID: 2020-036
    Published: 2022
    Advance online publication: January 25, 2022
    JOURNAL FREE ACCESS ADVANCE PUBLICATION

    The purpose of this study was to investigate the effect of various surface treatments on the shear bond strength between dental polyetheretherketone (PEEK) and adhesive resin cement. Two hundred and forty specimens were randomly classified into four groups: no treatment, sandblasted, sulfuric-acid-etched, and laser-grooved treatment. Each group was classified into two adhesive resin cement subgroups. Surface roughness, water contact angle, shear bond strength, and failure mode were measured; SEM and XPS results were obtained. The data were statistically analyzed using one-way or two-way analysis of variance and Tukey’s honest significant difference test (α=0.05). Laser-grooved PEEK surface showed regular grooves and carbonization by thermal degradation; the surface roughness as well as water contact angle of were the highest in all groups. Shear bond strength values were significantly higher in the laser-groove-treated and sulfuric-acid-etched groups. Laser-groove-treated specimens showed cohesive failure. Laser-grooved treatment can improve shear bond strength between PEEK and adhesive resin cement.

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  • Zhang HONGBO, Akira HASEBE, Arefin ALAM, Liu YUNQING, Shuhei HOSHIKA, ...
    Article type: research-article
    Article ID: 2021-203
    Published: 2022
    Advance online publication: January 25, 2022
    JOURNAL FREE ACCESS ADVANCE PUBLICATION

    This study evaluated the antibacterial activity of colloidal platinum nanoparticles (CPNs) toward Streptococcus mutans (S. mutans) viability. S. mutans 109c was treated with water and three CPN solutions at 37°C for 24 h (i.e., control, PAA-Pt, C-Pt, C-CyD-Pt). Dilution series (10–1–10–5) were prepared using brain heart infusion (BHI) broth for all samples, and a 100 µL suspension of each dilution was spread onto a BHI agar plate. Colony-forming units (CFU/mL) were determined after 24 h. The effects of CPNs on S. mutans survival and biofilm formation were investigated using fluorescence and scanning electron microscopies. The antibacterial rate of S. mutans increased with increasing concentrations of all three CPNs, with PAA-Pt nanoparticles exhibiting the highest antibacterial efficacy. CPNs were found to reduce S. mutans growth and inhibit biofilm formation remarkably.

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  • Kittisak SANON, Takashi HATAYAMA, Antonin TICHY, Ornnicha THANATVARAKO ...
    Article type: research-article
    Article ID: 2021-208
    Published: 2022
    Advance online publication: January 25, 2022
    JOURNAL FREE ACCESS ADVANCE PUBLICATION

    This study investigated the influence of application/wash-out times of sodium hypochlorite (NaOCl) and hypochlorous acid (HOCl) on dentin bond strength of one-step self-etch adhesives (1-SEAs). Human coronal dentin discs with a standardized smear layer were pretreated with 6% NaOCl or 100 ppm HOCl for 5 s, 15 s, or 30 s, and washed out with water for 5 s, 15 s or 30 s with or without the application of Clearfil DC Activator (CDA). No pretreatment was used as a control. The discs were bonded with a 1-SEA (Bond Force II or Clearfil Universal Bond Quick) and microtensile bond strength (µTBS) was measured after 24 h. Pretreatment with NaOCl for 15 s and 30 s significantly decreased µTBS (p<0.05), irrespective of wash-out time. The application of CDA recovered µTBS but did not outperform the control group. Conversely, pretreatment with HOCl for 15 s and 30 s followed by 30 s wash-out time significantly increased µTBS of 1-SEAs (p<0.05), regardless of CDA application.

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