MDPIActa Medica Okayama2073-43601552023Shear Bond Strength of Resin Luting Materials to Lithium Disilicate Ceramic: Correlation between Flexural Strength and Modulus of Elasticity1128ENMasaoIrieDepartment of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical ScienceMasahiroOkadaDepartment of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical ScienceYukinoriMaruoDepartment of Prosthodontics, Division of Dentistry, Okayama UniversityGoroNishigawaDepartment of Prosthodontics, Division of Dentistry, Okayama UniversityTakuyaMatsumotoDepartment of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical ScienceThis study investigates the effect of the curing mode (dual-cure vs. self-cure) of resin cements (four self-adhesive and seven conventional cements) on their flexural strength and flexural modulus of elasticity, alongside their shear bond strength to lithium disilicate ceramics (LDS). The study aims to determine the relationship between the bond strength and LDS, and the flexural strength and flexural modulus of elasticity of resin cements. Twelve conventional or adhesive and self-adhesive resin cements were tested. The manufacturer's recommended pretreating agents were used where indicated. The shear bond strengths to LDS and the flexural strength and flexural modulus of elasticity of the cement were measured immediately after setting, after one day of storage in distilled water at 37 degrees C, and after 20,000 thermocycles (TC 20k). The relationship between the bond strength to LDS, flexural strength, and flexural modulus of elasticity of resin cements was investigated using a multiple linear regression analysis. For all resin cements, the shear bond strength, flexural strength, and flexural modulus of elasticity were lowest immediately after setting. A clear and significant difference between dual-curing and self-curing modes was observed in all resin cements immediately after setting, except for ResiCem EX. Regardless of the difference of the core-mode condition of all resin cements, flexural strengths were correlated with the LDS surface upon shear bond strengths (R-2 = 0.24, n = 69, p < 0.001) and the flexural modulus of elasticity was correlated with them (R-2 = 0.14, n = 69, p < 0.001). Multiple linear regression analyses revealed that the shear bond strength was 17.877 + 0.166, the flexural strength was 0.643, and the flexural modulus was (R-2 = 0.51, n = 69, p < 0.001). The flexural strength or flexural modulus of elasticity may be used to predict the bond strength of resin cements to LDS.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2252005Root-surface gap-formation with RMGIC restorations minimized by reduced P/L ratio of the first increment and delayed polishing486497ENMasaoIrieRosalinaTjandrawinataKazuomiSuzukiDavid C.Watts<p><b>Objectives</b><br />
This in vitro study evaluated the effect on interfacial gap-formation around resin-modified glass–ionomer (RMGIC) root surface restorations with (a) variations in powder/liquid ratio (P/L) of the first increment of an incremental procedure, compared with a bulk restoration technique, and (b) delayed versus immediate polishing, to permit maturation.</p>
<p><b>Methods</b><br />
Cavity preparations were placed in premolar teeth on upper facial root surfaces. Two RMGICs were studied (Fuji II LC and Vitremer), with their associated conditioner or primer, applied with an incremental technique. The P/L ratio of the first increment was reduced to fractional (normalized) values between 0.2 and 1.0 of the manufacturers' recommended P/L, and the manufacturers' P/L was used for the second increment. Control groups were bulk filled. After polishing, either: (i) immediately after light-activation or (ii) after 24 h storage, the restored teeth were sectioned in a buccolingual direction through the center of the restoration and the presence or absence of marginal gaps was measured at ×1000 magnification at 14 points (each 0.5-mm apart) along the cavity restoration interface; (n=10; total points measured per group=140).</p>
<p><b>Results</b><br />
For both RMGICs, significant differences (p<0.05) in gap-incidence were observed between polishing (i) immediately and (ii) after one-day storage. In the former case, 30–70 gaps were found, with or without the incremental technique. In the latter case, only 2–14 gaps were observed. With fluid mixes (normalized P/L ratios between 0.3 and 0.6) for the first increment, gap-formation was greatly reduced, especially with Fuji II LC.</p>
<p><b>Significance</b><br />
To minimize gap formation, more fluid mixes could be used especially with Fuji II LC to give improved adaptation to the dentin. Secondly, whenever possible, polishing should be delayed on the final increment to permit maturation and minimize mechanical disruption of both increments.</p>No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2012004Marginal and flexural integrity of three classes of luting cement, with early finishing and water storage311ENMasaoIrieKazuomiSuzukiDavid C.Watts<p><b>Objectives.</b> The aims of this investigation were to clarify the effects of finishing-time and 24 h water-storage on mechanical properties and marginal adaptation to dentin of seven modern luting cements, representing three chemical types.</p>
<p><b>Methods.</b> Bistite II, Chemiace II, Compolute, XenoCem, PermaCem, Fuji Cem and Fuji Plus were investigated with specimen sub-groups (N=10) for each property measured. The principal series of experiments was conducted in dentin cavities with interfacial polishing either immediately (3 min) after setting or after 24 h water-storage. After the finishing procedure, the maximum marginal gap width and the opposing width (if any) per cavity were measured microscopically, and summed. Then the overall sum of gap-widths (per group; N=10) was calculated. Marginal gaps were similarly measured in Teflon cavities, together with shear-bond-strengths to dentin and early flexural strengths, moduli and swelling data.</p>
<p><b>Results.</b> For specimen-sets polished immediately after setting, summed marginal gaps of 23–121 μm were observed, for all luting cements except Compolute. A significantly different (p<0.05) result of either no gap or 6–28 μm summed gap-widths occurred in specimens polished after 24 h. For all materials, their shear-bond-strengths, flexural strength and moduli significantly increased after 24 h storage.</p>
<p><b>Significance.</b> The marginal behavior can be interpreted in terms of the contributions of bonding, shrinkage, swelling and compliance of components, along with compositional features of the cements. With these types of cement it is generally inadvisable to polish the interfacial luting surface immediately after cementing. The polishing procedures should be carried out not less than 24 h later. One resin-cement was able to withstand immediate finishing.</p>No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2292006Immediate versus water-storage performance of Class V flowable composite restoratives875883ENMasaoIrieKenjiHatanakaKazuomiSuzukiDavid C.Watts<p><b>Objectives</b><br />
The aims of this investigation were to clarify the effects of 24 h water-storage and finishing time on mechanical properties and marginal adaptation to a Class V cavity of eight modern flowable resin-composites.</p>
<p><b>Methods</b><br />
Eight flowable composites, plus two controls (one microfilled and one hybrid composite), were investigated with specimen sub-groups (n = 10) for each property measured. The principal series of experiments was conducted in model Class V cavities with interfacial polishing either immediately (3 min) after setting or after 24 h water-storage. After the finishing procedure, each tooth was sectioned in a buccolingual direction through the center of the restoration, and the presence or absence of marginal-gaps was measured (and then summed for each cavity) at 14 points (each 0.5 mm apart) along the cavity restoration interface (n = 10 per group; total points measured = 140). The shear bond-strengths to enamel and to dentin, and flexural strengths and moduli data were also measured at 3 min and after 24 h water-storage.</p>
<p><b>Results</b><br />
For all flowable composites, polished immediately after setting, 14–30 summed gaps were observed (controls: 64 and 42). For specimens polished after 24 h, a significantly (p < 0.05) reduced number of 8–17 summed gaps occurred for only 3 flowable composites; whereas for 5 flowable composites there were non-significantly-different (p > 0.05) numbers (11–17) of summed gaps (controls: 28 and 22). After 24 h storage, shear bond-strengths to enamel and to dentin, flexural strengths and moduli increased highly significantly (p < 0.001) for all materials, except Silux Plus.</p>
<p><b>Significance</b><br />
A post-cure interval of 24 h resulted in enhanced mechanical and adhesive properties of flowable dental composites. In a minority of cases there was also a reduced incidence of marginal-gap formation. However the latter effect may be partly attributed to 24 h delayed polishing, even though such a delay is not usual clinical practice.</p>No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2092004Immediate performance of self-etching versus system adhesives with multiple light-activated restoratives873880ENMasaoIrieKazuomiSuzukiDavid C.Watts<p><b>Objectives:</b> The purpose of this study was to evaluate the performance of both single and double applications of (Adper Prompt L-Pop) self-etching dental adhesive, when used with three classes of light-activated restorative materials, in comparison to the performance of each restorative system adhesive. Evaluation parameters to be considered for the adhesive systems were (a) immediate marginal adaptation (or gap formation) in tooth cavities, (b) free setting shrinkage-strain determined by the immediate marginal gap-width in a non-bonding Teflon cavity, and (c) their immediate shear bond-strengths to enamel and to dentin.</p>
<p><b>Methods:</b> The maximum marginal gap-width and the opposing-width (if any) in the tooth cavities and in the Teflon cavities were measured immediately (3 min) after light-activation. The shear bond-strengths to enamel and to dentin were also measured at 3 min.</b>
</p>
<p><b>Results:</b> For light-activated restorative materials during early setting (<3 min), application of Adper Prompt L-Pop exhibited generally superior marginal adaptation to most system adhesives. But there was no additional benefit from double application. The marginal-gaps in tooth cavities and the marginal-gaps in Teflon cavities were highly correlated (r=0.86–0.89, p<0.02–0.01). For enamel and dentin shear bond-strengths, there were no significant differences between single and double applications, for all materials tested except Toughwell and Z 250 with enamel.</p>
<p><b>Significance:</b> Single application of a self-etch adhesive was a feasible and beneficial alternative to system adhesives for several classes of restorative. Marginal gap-widths in tooth cavities correlated more strongly with free shrinkage-strain magnitudes than with bond-strengths to tooth structure.</p>No potential conflict of interest relevant to this article was reported.SAGE PublicationsActa Medica Okayama2280-8000182020Flexural properties, bond ability, and crystallographic phase of highly translucent multi-layered zirconia2280800020942717ENYukinoriMaruoDepartment of Occlusion and Removable Prosthodontics, Okayama UniversityKumikoYoshiharaNational Institute of Advanced Industrial Science and Technology, Health Research InstituteMasaoIrieDepartment of Biomaterials, Okayama UniversityGoroNishigawaDepartment of Occlusion and Removable ProsthodonticsNoriyukiNagaokaAdvanced Research Center for Oral and Craniofacial Sciences, Okayama UniversityTakuyaMatsumotoDepartment of Biomaterials, Okayama UniversityShogoMinagiAdvanced Research Center for Oral and Craniofacial Sciences, Okayama UniversityThis study investigated the mechanical properties, bond ability, and crystallographic forms of different sites in a highly translucent, multi-layered zirconia disk. Flexural properties, bond ability to resin cement, and phase composition were investigated at three sites of a highly translucent, multi-layered zirconia disk: incisal, middle, and cervical. Flexural strength (FS) and flexural modulus (FM) were measured with static three-point flexural test. Shear bond strength (SB) to resin cement was measured after 24 h storage (37°C). Phase composition under mechanical stress was analyzed using X-ray diffraction. Without air abrasion, FS at the incisal site yielded the lowest value and was significantly lower than the middle and cervical sites. Air abrasion lowered the FS of each site. FM at the incisal site without air abrasion showed the significantly lowest value, and air abrasion increased its FM value. At the middle and cervical sites, their FM values were higher than the incisal site but were not significantly affected by air abrasion. SB value did not show significant differences among the sites. After sintering, cubic zirconia was detected at each site. Rhombohedral phase transformation occurred after mirror polishing. In highly translucent, multi-layered zirconia which was mainly composed of cubic zirconia, rhombohedral phase transformation occurred under mechanical stress and resulted in weakened mechanical properties.No potential conflict of interest relevant to this article was reported.MDPIActa Medica Okayama2073-436012122020Flexural Strength of Resin Core Build-Up Materials: Correlation to Root Dentin Shear Bond Strength and Pull-Out Force2947ENMasaoIrieDepartment of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical ScienceYukinoriMaruoDepartment of Occlusion and Removable Prosthodontics, Okayama UniversityGoroNishigawaDepartment of Occlusion and Removable Prosthodontics, Okayama UniversityKumikoYoshiharaNational Institute of Advanced Industrial Science and Technology (AIST), Health and Medical Research InstituteTakuyaMatsumotoDepartment of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical ScienceThe aims of this study were to investigate the effects of root dentin shear bond strength and pull-out force of resin core build-up materials on flexural strength immediately after setting, after one-day water storage, and after 20,000 thermocycles. Eight core build-up and three luting materials were investigated, using 10 specimens (n = 10) per subgroup. At three time periods-immediately after setting, after one-day water storage, and after 20,000 thermocycles, shear bond strengths to root dentin and pull-out forces were measured. Flexural strengths were measured using a 3-point bending test. For all core build-up and luting materials, the mean data of flexural strength, shear bond strength and pull-out force were the lowest immediately after setting. After one-day storage, almost all the materials yielded their highest results. A weak, but statistically significant, correlation was found between flexural strength and shear bond strength (r = 0.508, p = 0.0026, n = 33). As the pull-out force increased, the flexural strength of core build-up materials also increased (r = 0.398, p = 0.0218, n = 33). Multiple linear regression analyses were conducted using these three independent factors of flexural strength, pull-out force and root dentin shear bond strength, which showed this relationship: Flexural strength = 3.264 x Shear bond strength + 1.533 x Pull out force + 10.870, p = 0.002). For all the 11 core build-up and luting materials investigated immediately after setting, after one-day storage and after 20,000 thermocycles, their shear bond strengths to root dentin and pull-out forces were correlated to the flexural strength in core build-up materials. It was concluded that the flexural strength results of the core build-up material be used in research and quality control for the predictor of the shear bond strength to the root dentin and the retentive force of the post.No potential conflict of interest relevant to this article was reported.MDPIActa Medica Okayama2504-477X5102021Flexural Property of a Composite Biomaterial in Three Applications282ENMasaoIrieDepartment of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical ScienceYukinoriMaruoDepartment of Occlusion and Removable Prosthodontics, Okayama University HospitalGoroNishigawaDepartment of Occlusion and Removable Prosthodontics, Okayama University HospitalTakuyaMatsumotoDepartment of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical ScienceResin composite is widely used in the dental field in clinics as a biomaterial. For example, it has been used as a composite material, a type of biomaterial, to repair caries and restore masticatory function, and as a luting agent to adhere the restoration to the tooth substrate. In order to demonstrate its function, we have measured the mechanical strength. From such basic research, we explain the potential of a dental material through the measurement of flexural strength and modulus of elasticity. In this research, we introduce commercial products that are actually used as composite materials suitable for tooth substrate and provide readers with their properties based on flexural strength and modulus of elasticity. In clinical performance, it might be advisable to delay polishing when a composite material is used for a luting material, a filling material and a core build-up material, as the flexural strength and the flexural modulus of elasticity were improved after 1 day of storage, and flexural strength and characteristics are considered as important mechanical properties of oral biomaterials.</p>No potential conflict of interest relevant to this article was reported.MDPIActa Medica Okayama1996-194415212022Does Multifunctional Acrylate's Addition to Methacrylate Improve Its Flexural Properties and Bond Ability to CAD/CAM PMMA Block?7564ENYukinoriMaruoDepartment of Prosthodontics, Okayama UniversityKumikoYoshiharaHealth Research Institute, National Institute of Advanced Industrial Science and TechnologyMasaoIrieDepartment of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical SciencesNoriyukiNagaokaAdvanced Research Center for Oral and Craniofacial Sciences, Okayama University Dental SchoolTakuyaMatsumotoDepartment of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical SciencesShogoMinagiDepartment of Prosthodontics, Okayama UniversityThis study investigated the effects of a multifunctional acrylate copolymer-Trimethylolpropane Triacrylate (TMPTA) and Di-pentaerythritol Polyacrylate (A-DPH)-on the mechanical properties of chemically polymerized acrylic resin and its bond strength to a CAD/CAM polymethyl methacrylate (PMMA) disk. The methyl methacrylate (MMA) samples were doped with one of the following comonomers: TMPTA, A-DPH, or Trimethylolpropane Trimethacrylate (TMPTMA). The doping ratio ranged from 10 wt% to 50 wt% in 10 wt% increments. The flexural strength (FS) and modulus (FM) of PMMA with and without comonomer doping, as well as the shear bond strength (SBS) between the comonomer-doped PMMA and CAD/CAM PMMA disk, were evaluated. The highest FS (93.2 +/- 4.2 MPa) was obtained when doped with 20 wt% of TMPTA. For TMPTMA, the FS decreased with the increase in the doping ratio. For SBS, TMPTA showed almost constant values (ranging from 7.0 to 8.2 MPa) regardless of the doping amount, and A-DPH peaked at 10 wt% doping (8.7 +/- 2.2 MPa). TMPTMA showed two peaks at 10 wt% (7.2 +/- 2.6 MPa) and 40 wt% (6.5 +/- 2.3 MPa). Regarding the failure mode, TMPTMA showed mostly adhesive failure between the CAD/CAM PMMA disk and acrylic resin while TMPTA and A-DPH showed an increased rate of cohesive or mixed failures. Acrylate's addition as a comonomer to PMMA provided improved mechanical properties and bond strength to the CAD/CAM PMMA disk.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama3322008Class I Gap-formation in Highly-viscous Glass-ionomer Restorations: Delayed vs Immediate Polishing196202ENMasaoIrieYukinoriMaruoGoroNishgawaKazuomiSuzukiDavid CWatts<p>This in vitro study evaluated the effects of delayed versus immediate polishing to permit maturation of interfacial gap-formation around highly viscous conventional glass-ionomer cement (HV-GIC) in Class I restorations, together with determining the associated mechanical properties. Cavity preparations were made on the occlusal surfaces of premolars. Three HV-GICs (Fuji IX GP, GlasIonomer FX-II and Ketac Molar) and one conventional glass-ionomer cement (C-GIC, Fuji II, as a control) were studied, with specimen subgroups (n=10) for each property measured. After polishing, either immediately (six minutes) after setting or after 24 hours storage, the restored teeth were sectioned in a mesiodistal direction through the center of the model Class I restorations. The presence or absence of interfacial-gaps was measured at 1000× magnification at 14 points (each 0.5-mm apart) along the cavity restoration interface (n=10; total points measured per group = 140). Marginal gaps were similarly measured in Teflon molds as swelling data, together with shear-bond-strength to enamel and dentin, flexural strength and moduli. For three HV-GICs and one C-GIC, significant differences (p<0.05) in gap-incidence were observed between polishing immediately and after one-day storage. In the former case, 80–100 gaps were found. In the latter case, only 9–21 gaps were observed. For all materials, their shear-bond-strengths, flexural strength and moduli increased significantly after 24-hour storage.</p>No potential conflict of interest relevant to this article was reported.