Dental Materials Journal
Online ISSN : 1881-1361
Print ISSN : 0287-4547
ISSN-L : 0287-4547
最新号
選択された号の論文の23件中1~23を表示しています
Review
  • Abdul Samad KHAN, Mariam Raza SYED
    2019 年 38 巻 2 号 p. 163-176
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/11/01
    ジャーナル フリー

    Currently, much has been published related to conventional resin-based composites and adhesives; however, little information is available about bioceramics-based restorative materials. The aim was to structure this topic into its component parts and to highlight the translational research that has been conducted up to the present time. A literature search was done from indexed journals up to September 2017. The main search terms used were based on dental resin-based composites, dental adhesives along with bioactive glass and the calcium phosphate family. The results showed that in 123 articles, amorphous calcium phosphate (39.83%), hydroxyapatite (23.5%), bioactive glass (16.2%), dicalcium phosphate (5.69%), monocalcium phosphate monohydrate (3.25%), and tricalcium phosphate (2.43%) have been used in restorative materials. Moreover, seven studies were found related to a newly developed commercial bioactive composite. The utilization of bioactive materials for tooth restorations can promote remineralization and a durable seal of the tooth–material interface.

Original Paper
  • Sasinisa WARANGKULKASEMKIT, Piyapanna PUMPALUK
    2019 年 38 巻 2 号 p. 177-181
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/11/01
    ジャーナル フリー

    Various materials have been used for core build-up when restoring the coronal portion of the tooth. Currently, bulk-fill resin composites have been produced to restore a large posterior cavity in single increment. This study aimed to evaluate the compressive strength, flexural strength, and microhardness of three commercial composite core build-up materials. All data were analyzed by oneway ANOVA and Tukey test methods (α=0.05). Flexural strength data were subjected to Weibull statistics analysis. All three groups presented significant differences in the compressive strength, flexural strength, and Knoop hardness. FiltekTM Z350 XT had the greatest compressive strength (MPa) and Knoop hardness while FiltekTM bulk fill had the highest flexural strength. MultiCore®Flow had the lowest properties; however, it revealed the highest Weibull modulus (m) value. With regard to the properties tested in this study, bulk-fill resin composite can be used as an alternative to conventional resin composite for core build-up material.

  • Blanca I. FLORES-FERREYRA, Rogelio J. SCOUGALL-VILCHIS, Ulises VELAZQU ...
    2019 年 38 巻 2 号 p. 182-188
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/11/01
    ジャーナル フリー

    The surface roughness, morphology and shear bond strength (SBS) of dental zirconia using three different surface treatment techniques were evaluated. Three groups of sintered zirconia blocks were treated as follow, 1) Airborne-particle abrasion (APA) group (G1-APA), 50-µm Al2O3; 2) APA and 9% hydrofluoric acid etching (G2-HF); 3) APA and Sodium Hydroxide (G3-NaOH). The specimens were evaluated for roughness [atomic force microscope (AFM)], morphology [Scanning Electron Microscope (SEM)] and for SBS in the universal testing machine. The AFM revealed changes in the roughness after the surface treatments, however there was not Ra difference between groups, SEM analysis revealed changes in surface morphology for all surface treated specimens. For SBS, significant difference was found between G1-APA=8.4±2.7 MPa and G2-HF=3.3±0.6 MPa (p<0.05) and G2-HF and G3-NaOH=9.0±3.0 MPa (p<0.05). The main fracture mode was mixed failure (63%) for G1-APA and G3-NaOH groups. G2-HF showed 100% adhesive failure. SBS was improved with NaOH, however application of HF significantly decreased SBS.

  • Shaymaa E. ELSAKA, Amr M. ELNAGHY
    2019 年 38 巻 2 号 p. 189-195
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/11/01
    ジャーナル フリー

    This study evaluated the effect of titanium tetrafluoride (TiF4) solution on the bond strength of glass fiber post to resin cement. The specimens were divided into eight groups according to the method of surface treatment performed. Flexural properties and microtensile bond strength (µTBS) were determined. Data were analyzed using two-way ANOVA and Tukey’s post hoc tests. The highest µTBS achieved with the TiF4 (4 wt/v%-4 min) group compared with the other groups (p<0.05). This finding could be attributed to the effectiveness of TiF4 (4 wt/v%-4 min) on removing the surface layer of the resin matrix of fiber posts that provides more uncovered surface areas of posts which improved the micromechanical retention of the resin cement. Surface treatments did not affect the flexural properties of fiber posts (p>0.05). Surface treatment of fiber post with TiF4 (4 wt/v%-4 min) solution exhibited higher bond strength to resin cement compared with other surface treatments.

  • Sufyan GAROUSHI, Pekka VALLITTU, Lippo LASSILA
    2019 年 38 巻 2 号 p. 196-202
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/11/17
    ジャーナル フリー

    The aim was to evaluate the effect of different zirconia discontinuous fiber fractions on radiopacity and other selected properties of glass discontinuous fiber-reinforced flowable composite (Exp-SFRC). Exp-SFRC was prepared by mixing 30 wt% of resin-matrix and 45 wt% of particulate-fillers to 25 wt% of various weight-fractions of E-glass/zirconia discontinuous fiber-fillers (25:0, 20:5, 15:10, 10:15, 0:25 wt%). Flexural strength and fracture toughness were determined for each experimental material. Radiograph of each Exp-SFRC and aluminium step wedge were taken to determine the radiopacity. Degree of conversion and light-transmission were also measured. Scanning electron microscopy was used to evaluate the microstructure of the Exp-SFRC. Analysis of variance (ANOVA) revealed that fractions of E-glass/zirconia discontinuous fiber-fillers had significant effect (p<0.05) on radiopacity and other tested properties of the Exp-SFRCs. Replacing low fraction of E-glass fiber with zirconia fiber-fillers can increase the radiopacity of the fiber-reinforced composite without deteriorating the mechanical properties, although, degree of conversion was decreased.

  • Ruizhi YIN, Min-Ho LEE, Tae-Sung BAE, Kwang-Yeob SONG
    2019 年 38 巻 2 号 p. 203-210
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/12/01
    ジャーナル フリー

    This study was to evaluate the load bearing capacity of monolithic dental zirconia crowns, and the effect of surface finishing on fracture strength. (1) The zirconia plates were divided into 5 groups and polished by various types of polishing bur, every specimen was analyzed by surface roughness testing, and X-ray diffraction (XRD). (2) The zirconia crowns were classified into 4 groups corresponding to different surface treatments and thickness. All the crowns were cemented and subjected to a load of 7 kg for 5 min. Stored in distilled water at 37°C for 24 h. Observe the typical surface using field emission scanning electron microscopy (FE-SEM). The cycling and fracture tests were carried out. The data was statistically analyzed. The groups had better fracture strength after polishing. This suggests the monoclinic phase can be eliminated by optimizing the polishing process. Moreover, the fracture strength increased with occlusal thickness (p<0.05).

  • Peng ZHANG, Lin DING, Shohei KASUGAI
    2019 年 38 巻 2 号 p. 211-217
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/12/01
    ジャーナル フリー

    Bio-Oss (BO), one of the bone substitutes, is extensively used for augmentation in dental field because it is highly biocompatible and osteoconductive, which however does not stimulate bone formation. Doxycycline (DOX), a widely-used antibiotic, shows inhibitory effects on inflammation and osteoclastogenesis, and it has been reported to stimulate bone formation. The objective of this study is to investigate the vertical bone formation with DOX doped BO in guided bone regeneration on rat calvaria. Forty rats underwent calvarial vertical augmentation surgeries. Twenty rats received BO whereas the others received DOX doped BO. The calvarias were harvested and analyzed radiologically, histologically and with RT-PCR at 4 and 8 weeks postoperatively. At 4 weeks, the area of mineralized new bone statistically increased in BO+DOX compared to BO, upregulations of TGFβ1, BMP2 and β-catenin were evident in BO+DOX. The present study demonstrates that BO+DOX improve vertical bone augmentation.

  • Nazmiye DÖNMEZ, Ayça Sarıalioğlu GÜNGÖR, Barış KARABULUT, Şeyda Hergün ...
    2019 年 38 巻 2 号 p. 218-225
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/12/01
    ジャーナル フリー

    The micro-tensile bond strengths (micro-TBSs) of four universal adhesive systems, applied in two different bonding techniques, to carries-affected dentin after Er:YAG laser irradiation were investigated. Twenty-four extracted human molars were divided into four groups, according to the adhesive systems used. Each group was subdivided into two subgroups, depending on the bonding method used: the etch-and-rinse procedure or self-etch procedure. The carious lesions were irradiated using an Er:YAG laser. Resin composites were used to restore the adhesive-treated dentin surfaces. After 2,500 thermal cycles, the vertical composite resin-dentin sticks obtained were subjected to micro-TBS tests. One tooth in each group was examined using scanning electron microscopy (SEM). There were statistically significant differences (p<0.001) in micro-TBS values between universal adhesives. The results of this study suggested that universal adhesives applied both with self and total etch technique can be used for adhesive restorations to caries-affected dentin after Er:YAG laser irradiation. If lasers are preferred as a caries removal method, choosing a dentin bonding agent containing MDP may be recommended in clinical practice due to the property of increasing the bonding strength.

  • Jean-Sean TAY, Billy Bing Liang CHOONG, Ing Hong OOI, Bee Siew TAN
    2019 年 38 巻 2 号 p. 226-232
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/12/01
    ジャーナル フリー

    The purpose of this study was to investigate the effect of substituting triethyleneglycol dimethacrylate (TEGDMA) with 2,2,2-trifluoroethyl methacrylate (TFEMA) on water sorption, water solubility, degree of conversion, polymerization shrinkage, fluoride release and flexural strength of bisphenol-A-glycerolate dimethacrylate (Bis-GMA)/TEGDMA/urethane dimethacrylate (UDMA) dental composites. Flexural strength, water sorption and water solubility were measured according to ISO 4049 standard. Degree of conversion was determined by FTIR technique. Fluoride release rate in deionized water at 37°C was determined by using photometric method. One-way ANOVA and Tukey’s HSD tests were used for statistical significance analysis (p<0.05). The results demonstrated that TFEMA decreased water solubility and volumetric shrinkage significantly but neither reduced water sorption, enhanced flexural strength nor improved degree of conversion. Partial substitution of TEGDMA with TFEMA in Bis-GMA/TEGDMA/UDMA dental composite had positive effect on its water solubility and volumetric shrinkage quality.

  • Dhaifallah ALQARNI, Masatoshi NAKAJIMA, Keiichi HOSAKA, Kurumi IDE, Da ...
    2019 年 38 巻 2 号 p. 233-240
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/11/17
    ジャーナル フリー

    The repair microshear bond strengths (µSBSs) to resin matrices in 4 different cured-composites after water storage (0, 60 s, 1 week, 1 month) were evaluated. Three different adhesive application methods to the cured-composites were performed; (1) none, (2) onestep self-etch adhesive application, and (3) one-step self-etch adhesive application with a silane coupling agent. Degree of conversion (DC) of the composite discs was determined using ATR/FT-IR with a time-based spectrum analysis. Initially, the amount of un-reacted resin monomers in the repaired cured-composite contributed to the bonding performance of newly-filled uncured-composite to resin matrix of the cured-composite. Adhesive application could not improve their repair µSBS. After 1-month of water-storage, the repair µSBS was dependent on material, which either reduced or did not and was not influenced by their amount of un-reacted resin monomers. When repairing aged composite resin, the appropriate adhesive application procedures were different among resin composites.

  • Yener OKUTAN, Munir Tolga YUCEL, Tugce GEZER, Mustafa Borga DONMEZ
    2019 年 38 巻 2 号 p. 241-249
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/12/11
    ジャーナル フリー

    This study examined the surface roughness (Ra) and shear bond strength (SBS) of Yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic after airborne particle abrasion at different pressures and particle sizes, pre- and post-sintering. Ninety specimens, prepared from Y-TZP ceramic blocks (Vita In-Ceram YZ, Vita Zahnfabrik), were divided into nine subgroups: control, and 50 and 110 µm Al2O3 airborne particle abrasion at 3 and 4 bar pressure, before and after sintering, respectively. According to the sintering order, before and after surface treatments, Ra values were measured using a profilometer. SBS to Y-TZP was assessed after thermocycling, using self-adhesive resin cement (Rely X U200, 3M ESPE). Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) were performed on one specimen per group. All surface-treated samples were rougher than the controls. ABS50-4 (50 µm Al2O3 airborne particle abrasion at 4 bar pressure before sintering), ABS110-3, and ABS110-4 showed the highest Ra values, among all cohorts. The controls displayed lower SBS values than the treated groups (p<0.05), which had statistically similar results to each other. Airborne particle abrasion of pre-sintered Y-TZP, followed by sintering, increased the tetragonal structure contents.

  • Shota HAYASHI, Shinya HOMMA, Takuya TAKANASHI, Tomoki HIRANO, Masao YO ...
    2019 年 38 巻 2 号 p. 250-256
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/12/11
    ジャーナル フリー

    To clarify the influence of translucent tetragonal zirconia polycrystals (TZP) on wear properties of esthetic dental materials, two-body wear test was performed using translucent TZP as abrader specimen, and bovine tooth enamel (BTE), two resin composites including hybrid filler (CRH) and nano filler (CRN), two glass ceramics including leucite reinforced feldspar porcelain (POR) and lithium disilicate (LDC), or translucent TZP as substrate specimen. After the wear test, wear volume were determined from substrate specimen and surface roughness were measured from abrader specimen. In addition, Vickers hardness was measured and surface morphologies were observed after wear test using a scanning electron microscope. The wear volume of the esthetic dental material against translucent TZP was greater in glass ceramics (POR, LDC), smaller in resin composite (CRH, CRN) and BTE, and no wear in translucent TZP. Microstructures of the esthetic dental material may play a crucial role for wear behavior against translucent TZP.

  • Amr SAAD, Go INOUE, Toru NIKAIDO, Ahmed M. A ABDOU, Mahmoud SAYED, Mic ...
    2019 年 38 巻 2 号 p. 257-263
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/12/01
    ジャーナル フリー

    This study evaluated the effect of two hemostatic agents on bond strength of resin-modified glass ionomer cement (RMGIC) to root dentin after using different pretreatment solutions compared to resin composite with a 2-step self-etch adhesive. Dentin specimens were either uncontaminated or contaminated with a ferric sulphate or aluminum chloride astringent, RMGIC was applied after conditioning with; Cavity Conditioner, Self Conditioner or Clearfil SE Primer, while a resin composite was bonded using Clearfil SE Bond. Microtensile bond strength (μTBS) values and failure modes were determined. Two-way ANOVA revealed that hemostatic agents did not significantly affect the RMGIC bond strength with any conditioning material (p>0.05). SE Primer pretreatment provided the highest μTBS values among RMGIC groups. For the resin composite, ferric sulphate astringent significantly reduced μTBS value (p≤0.001). Scanning electron micrographs of representative dentin surfaces contaminated with the hemostatic agents showed effects on smear layer removal and dentinal tubule occlusion.

  • Thiago Soares PORTO, Renato Cassio ROPERTO, Anna AKKUS, Ozan AKKUS, So ...
    2019 年 38 巻 2 号 p. 264-270
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/12/11
    ジャーナル フリー

    Computer-aided design/computer-aided manufacturing (CAD/CAM) materials were submitted to thermocycling, to identify changes in mechanical behavior. Four CAD/CAM materials were divided in four subordinate groups (n=9): (1) dry out for 7 days, (2) distilled water at 37oC for 7 days, (3) 60,000 thermocycles, and (4) 120,000 thermocycles. Following thermocycling, samples were submitted to three-point bending test. Two-way ANOVA and post-hoc Tukey’s test were performed (α=0.05). The IPS e.max CAD had a flexural strength of 396±75 MPa and flexural modulus of 84±11 GPa, followed by Vita Enamic with values of 153±17 MPa and 28±5 GPa respectively. The flexural strength recorded for Lava Ultimate was 149±28 MPa and the flexural modulus was 12±3 GPa. Vitablocs Mark II had the lowest flexural strength values (125±10 MPa) and a flexural modulus of 49±15 GPa. Although polymer-based materials have similar mechanical properties compared to ceramics, they are affected by thermo cycling conditions.

  • Masahiro IIJIMA, Rina ISHIKAWA, Kyotaro KAWAGUCHI, Shuichi ITO, Takash ...
    2019 年 38 巻 2 号 p. 271-277
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/12/11
    ジャーナル フリー

    We investigated the effects of the weekly application of pastes containing a surface reaction-type pre-reacted glass-ionomer (S-PRG) filler on dentin remineralization. Human dentin blocks were demineralized and polished using pastes containing S-PRG filler (0, 5, and 30%), and then immersed in remineralizing solution for 1 month. Nanoindentation testing was carried out during the immersion period, and the dentin surfaces were examined using scanning electron microscopy. A nano-hydroxyapatite-containing paste was used for comparison. Immersion in demineralization solution had a marked negative effect on the mechanical properties in all specimens. The mechanical properties of specimens polished with S-PRG filler-containing pastes recovered significantly after immersion in remineralization solution for 1 month compared with the other specimens. After remineralization, the open dentinal tubules were filled with a remineralization layer in specimens polished with S-PRG filler-containing and nano-hydroxyapatite-containing pastes. S-PRG filler-containing pastes can aid dentin remineralization.

  • Ying LI, Baoe LI, Yunjia SONG, Aobo MA, Changyi LI, Xu ZHANG, Hongjie ...
    2019 年 38 巻 2 号 p. 278-286
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2018/12/11
    ジャーナル フリー

    To improve initial osteoblast adhesion and subsequent osseointegration, TiO2 nanotubes layer was constructed on the titanium (Ti) surface by anodic oxidation (AO), with an additional hydroxyapatite (HA) coating to form the AO/HA surface. Tests on in vitro cellular activity displayed that the AO surface, especially the AO/HA surface, promoted initial adhesion, proliferation and differentiation of osteoblast cells. The modified AO and AO/HA surfaces further presented an up-regulated gene expression of osteogenic and adhesion markers collagen type 1 (COL), osteopontin (OPN), osteocalcin (OCN) and vinculin. In addition, in vivo experiments with a rat model demonstrated that the AO surface, particularly the AO/HA surface, achieved earlier osseointegration and a superior bone bonding ability compared with Ti. Our study shed light on a synergistic role played by nanotopography and HA in promoting osteoblast adhesion, proliferation, differentiation and osseointegration, thus suggesting a promising method for better modifying the implant surface.

  • Nattawit NIYOMSUJARIT, Pisol SENAWONGSE, Choltacha HARNIRATTISAI
    2019 年 38 巻 2 号 p. 287-294
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2019/02/01
    ジャーナル フリー

    This study determined the micro-shear bond strength (µSBS) of two self-etching adhesives to dentin surface after smear layer removal with a novel ultrasonic brushing method. Ninety-five dentin discs were ground flat with diamond burs and divided into 5 groups; no treatment (control), brushing with a custom-made brush for 10 and 30 s without and with ultrasonic application. The smear layer thickness was evaluated using SEM. The 24 h µSBS of Clearfil SE Bond (CSE) and Clearfil Tri S Bond (CTS) to these dentin surfaces were evaluated. Smear layer thickness decreased significantly from control, brushing without, and brushing with ultrasonic groups, respectively. The µSBS of CSE were higher than CTS in all groups. The µSBS were improved with ultrasonic brushing for 30 s for both adhesives. Ultrasonic brushing is the effective method in mechanical smear layer removal which can improve bond strength of self-etching adhesives to ground dentin.

  • Mihriban Dudu Gizem GENÇER, Zuhal KIRZIOĞLU
    2019 年 38 巻 2 号 p. 295-302
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2019/02/01
    ジャーナル フリー

    This study aimed to evaluate color masking effect from treatments with resin infiltrant and two different remineralization agents applied with microabrasion to anterior teeth with developmental enamel defects. The incisors of patients aged 8–17 were evaluated. The study involved two groups including fluorosis (Group 1) and hypomineralization (Group 2) cases. These two groups were further divided based on the treatment received: Group A: Icon®, Group B: Opalustre®+Clinpro White Varnish®, and Group C: Opalustre®+Tooth Mousse®. The spectrophotometric values were recorded. Furthermore, the L* and ΔE values were evaluated by repeated measures of ANOVA. The largest increase in L* values over time after treatment was in Group 1A, followed by Group 1C and Group 1B. The largest increase in ΔE values over time after treatment was in Group 1A. Clinically observable difference was achieved as a result of all treatment groups. Especially resin infiltration treatment has been found to be more effective in teeth with fluorosis.

  • Sumiyo SUZUKI, Yu KATAOKA, Masafumi KANEHIRA, Mikihiro KOBAYASHI, Taka ...
    2019 年 38 巻 2 号 p. 303-310
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2019/02/01
    ジャーナル フリー

    This study aimed to non-destructively analyze the progression of subsurface enamel caries using swept-source optical coherence tomography (SS-OCT), a recently developed imaging analysis modality. Artificial enamel caries at various stages of demineralization were created in bovine tooth enamel using a modified lactic acid gel system. Untreated enamel served as a control. OCT images from cross-sections of enamel were collected. Mineral density, distribution, and histological changes were analyzed using an electron probe microanalyzer, scanning electron microscopy, and contact microradiography. The Raman spectrum and X-ray structural analysis of the enamel surfaces were determined. SS-OCT detected significant differences in mineral loss among the samples. A high-brightness image was confirmed, along with changes in the respective brightness graphs proportionate to the degree of demineralization. SS-OCT can potentially be used to evaluate the progression of incipient enamel carious lesions.

  • Hanho GO, Howon PARK, Juhyun LEE, Hyunwoo SEO, Siyoung LEE
    2019 年 38 巻 2 号 p. 311-316
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2019/02/28
    ジャーナル フリー

    To evaluate the effect of various polishing points on surface roughness of pediatric zirconia crowns and to correlate findings with bacterial adhesion. Zirconia discs (n=40) were fabricated and divided into five groups according to point type used to roughen and polish: I (negative control [not roughened]); II (positive control [roughened]); and III–V, representing three commercially available point brands. Atomic force and scanning electron microscopy were used to assess surface roughness. The number of colony forming units were counted after biofilm formation. A statistically significant difference was found in surface roughness and bacterial adhesion between the positive control and the other four groups, with no difference between negative control and the three point groups. Surface roughness and bacterial adhesion were significantly and positively correlated. Surface roughness and bacterial adhesion in pediatric zirconia crowns were not significantly different from other materials regardless of polishing system.

  • Fehmi GÖNÜLDAŞ, Caner ÖZTÜRK, Pelin ATALAY, Derya ÖZTAŞ
    2019 年 38 巻 2 号 p. 317-322
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2019/02/01
    ジャーナル フリー

    The effect of surface finishing techniques on machinable ceramics to obtain optimum smoothness is unclear. The aim of the study was to evaluate the effects of surface finishing techniques on machinable feldspathic and leucite-reinforced ceramics. Forty specimens were divided into four subgroups according to surface finishing techniques and ceramic structure. A profilometer was used to evaluate surface roughness. A spectrophotometer was used to obtain the CIE L*, a* and b* coordinates. All specimens were subjected to a three-point bending test to determine flexural strength. All data were analyzed with two-way ANOVA and Tukey’s HSD tests (p<0.05). Polishing techniques were found to be more effective than the glazing method to obtain smooth surfaces. Glazing technique increased the flexural strength of leucite-reinforced ceramics. Finishing procedures have different effects on the success of the restorations and must be considered by the clinicians.

  • Soichi KURODA, Akikazu SHINYA, Harunori GOMI
    2019 年 38 巻 2 号 p. 323-328
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2019/02/28
    ジャーナル フリー

    In this study, we investigated the effect of frame design on the fracture strength of a zirconia crown and porcelain-faced crown, with the aim of clinically applying a zirconia crown fabricated using computer-aided design and manufacturing. The results showed that the fracture strengths were 645.9 MPa with Frame Design 1, 759.5 MPa with Frame Design 2, and 989.7 MPa with Frame Design 3, suggesting that the fracture strength improved depending upon the frame design. The above information suggests that it is necessary for the zirconia crown frame form to have an occlusal surface table where the crown design has a reduced outer diameter, instead of using the conventional form of covering the abutment tooth with a thickness of 0.5 mm.

  • Hiroyuki ARIKAWA, Yoshito MINESAKI, Koichi MURAGUCHI, Hiroshi KONO, Ma ...
    2019 年 38 巻 2 号 p. 329-336
    発行日: 2019/03/28
    公開日: 2019/03/31
    [早期公開] 公開日: 2019/02/01
    ジャーナル フリー

    The aim of this study was to clarify the temperature dependence of color, i.e. the thermochromism of restorative composite resins at typical intraoral temperatures. Five brands of restorative composite resins were used. The CIE L*a*b* color values were measured using a spectrophotometer at specimen temperatures of 4, 23, 37, 60, and 80ºC. The temperature dependence of the refractive index of the materials at 4–80ºC were also determined using a refractometer. The values of L* for all materials decreased, and those of a* and b* for most of the materials increased, with increasing temperature. The color difference (ΔE*) for all materials increased with increasing specimen temperatures. The refractive index of the A4 shade of the materials consistently decreased with increasing temperatures. Most of the materials exhibited perceptible thermochromism related to intraoral thermal conditions. Optical properties that change in response to temperature could help explain the thermochromism of materials.

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