• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.1
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• pp.67-78
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• 2012

The purpose of this study was to determine whether there were differences in shear bond strength to human dentin using IDS technique compared with DDS. Forty freshly extracted human molars were and devided into 4 groups. The control group specimens were, on the morrow of tooth preparation, light-cured after application of dentin bonding agent and cemented with resin cement. The IDS/SE(immediate dentin sealing, Clearfil$^{TM}$ SE Bond) and IDS/SB (immediate dentin sealing, Adapter$^{TM}$ Single Bond 2) specimens were, on the morrow of tooth preparation, light-cured after application of dentin bonding agent(Clearfil$^{TM}$ SE Bond and Adapter$^{TM}$ Sing Bond 2, respectively), whereas DDS specimens were not treated with any dentin bonding agent. IDS/SE, IDS/SB and DDS specimens were thermocycled. Following that delay, specimens were cemented with resin cement. The dentin bonding agent was left unpolymerized until the application of porcelain restoration. Shear bond strengths were measured using a universal testing machine. Specimens also were evaluated for mode of fracture using an optical microscope. The mean shear bond strengths of control group and IDS/SE groups were not statistically different from one another. The bond strength of IDS/SE group had a significantly higher mean than that of DDS group. There was no significant difference in the mean shear bond strength between IDS/SB(4.11MPa) and DDS group. The evaluation of failure modes indicates that most failures in the control group and IDS/SE groups were mixed, whereas failures in the DDS group were interfacial. When preparing teeth for indirect ceramic restoration, IDS with Clearfil$^{TM}$ SE Bond results in improved shear bond strength compared with DDS.

• Restorative Dentistry and Endodontics
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• v.24 no.4
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• pp.647-656
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• 1999

The purpose of this study was to investigate the shear bond strength and marginal microleakage of composite to enamel and dentin according to different treatment methods when the applied bonding agent was contaminated by artificial saliva. For the shear bond strength test, the buccal and occlusal surfaces of one hundred twenty molar teeth were ground to expose enamel(n=60) and dentin surfaces(n=60). The specimens were randomly assigned into control and 5 experimental groups with 10 samples in each group. In control group, a bonding system(Scotchbond$^{TM}$ Multi-Purpose plus) and a composite resin(Z-100$^{TM}$) was bonded on the specimens according to manufacture's directions. Experimental groups were subdivided into 5 groups. After polymerization of an adhesive, they were contaminated with at artificial saliva on enamel and dentin surfaces: Experimental group 1 ; artificial saliva was dried with compressed air. Experimental group 2 ; artificial saliva was rinsed with air-water spray and dried. Experimental group 3 ; artificial saliva was rinsed, dried and applied an adhesive. Experimental group 4 ; artificial saliva was rinsed, dried, and then etched using phosphoric acid followed by an adhesive. Experimental group 5, artificial saliva was rinsed, dried, and then etched with phosphoric acid followed by consecutive application of both a primer and an adhesive. Composite resin(Z-100$^{TM}$) was bonded on saliva-treated enamel and dentin surfaces. The shear bond strengths were measured by universal testing machine(AGS-1000 4D, Shimaduzu Co. Japan) with a crosshead speed of 5mm/minute under 50kg load cell. Failure modes of fracture sites were examined under stereomicroscope. The data were analyzed by one-way ANOVA and Tukey's test. For the marginal microleakage test, Class V cavities were prepared on the buccal surfaces of sixty molars. The specimens were divided into control and experimental groups. Cavities in experimental group were contaminated with artificial saliva and those surfaces in each experimental groups received the same treatments as for the shear test. Cavities were filled with Z-100. Specimens were immersed in 0.5% basic fuchsin dye for 24 hours and embedded in transparent acrylic resin and sectioned buccolingually with diamond wheel saw. Four sections were obtained from the one specimen. Marginal microleakages of enamel and dentin were scored under streomicroscope and averaged from four sections. The data were analyzed by Kruskal-Wallis test and Fisher's LSD. The results of this study were as follows. 1. The shear bond strength to enamel showed lower value in experimental group 1(13.20${\pm}$2.94MPa) and experimental group 2(13.20${\pm}$2.94MPa) than in control(20.03${\pm}$4.47MPa), experimental group 4(20.96${\pm}$4.25MPa) and experimental group 5(21.25${\pm}$4.48MPa) (p<0.05). 2. The shear bond strength to dentin showed lower value in experimental group 1(9.35${\pm}$4.11MPa) and experimental group 2(9.83${\pm}$4.11MPa) than in control group(17.86${\pm}$4.03MPa), experimental group 4(15.04${\pm}$3.22MPa) and experimental group 5(14.33${\pm}$3.00MPa) (p<0.05). 3. Both on enamel and dentin surfaces, experimental group 1 and 2 showed many adhesive failures, but control and experimental group 3, 4 and 5 showed mixed and cohesive failures. 4. Enamel marginal microleakage was the highest in experimental group 1 and there was a significant difference in comparison with other groups (p<0.05). 5. Dentin marginal microleakages of experimental group 1 and 2 were higher than those of other groups (p<0.05). This result suggests that treatment methods, re-etching with 35% phosphoric acid followed by re-application of adhesive or repeating all adhesive procedures, will produce good effect on both shear bond strength and microleakage of composite to enamel and dentin if the polymerized bonding agent was contaminated by saliva.

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.2
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• pp.135-142
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• 2022

Purpose. This study aims to evaluate the combined effect of reduced thickness in different regions on the fracture resistance of monolithic zirconia crowns. Materials and methods. Seven nickel-chromium dies were generated from a 3D model of mandibular first molar using the digital scanner with the following geometries: 1.5 mm occlusal reduction, 1.0 mm deep chamfer. Based on the abutment model, Zirconia blocks (Luxen Zirconia) were selected to fabricate Sixty-three zirconia crowns with occlusal thicknesses of 0.3 mm, 0.5 mm, and 1.5 mm, and different axial thicknesses of 0.3 mm, 0.5 mm, and 1.0 mm. All crowns were cemented by resin cement. Next, the crowns were subjected to load-to-fracture test until fracture using an electronic universal testing machine. In addition, fracture patterns were observed with a scanning electron microscope (SEM). Two-way ANOVA and the Tuckey HSD test for post hoc analysis were used for statistical analysis (P < .05). Results. The mean values of fracture resistancerecorded was higher than the average biting force in the posterior region. The two-way ANOVA showed that the occlusal and axial thickness affected the fracture resistance significantly (P < .05). However, the effect of axial thickness on fracture resistance did not show a statistical difference when thicker than 0.5 mm. The observed failure modes were partial or complete fracture depending on the severity of crack propagation. Conclusion. Within the limitations of the present study, the CAD-CAM monolithic zirconia crown with extremely reduced thickness showed adequate fracture resistance to withstand occlusal load in molar regions. In addition, both occlusal and axial thickness affected the fracture resistance of the zirconia crown and showed different results as combined.

• Journal of Distribution Science
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• v.10 no.2
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• pp.29-41
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• 2012

This paper undertakes a conceptual review of transaction cost to broaden the understanding of the transaction cost analysis (TCA) approach. More than 40 years have passed since Coase's fundamental insight that transaction, coordination, and contracting costs must be considered explicitly in explaining the extent of vertical integration. Coase (1937) forced economists to identify previously neglected constraints on the trading process to foster efficient intrafirm, rather than interfirm, transactions. The transaction cost approach to economic organization study regards transactions as the basic units of analysis and holds that understanding transaction cost economy is central to organizational study. The approach applies to determining efficient boundaries, as between firms and markets, and to internal transaction organization, including employment relations design. TCA, developed principally by Oliver Williamson (1975,1979,1981a) blends institutional economics, organizational theory, and contract law. Further progress in transaction costs research awaits the identification of critical dimensions in which transaction costs differ and an examination of the economizing properties of alternative institutional modes for organizing transactions. The crucial investment distinction is: To what degree are transaction-specific (non-marketable) expenses incurred? Unspecialized items pose few hazards, since buyers can turn toalternative sources, and suppliers can sell output intended for one order to other buyers. Non-marketability problems arise when specific parties' identities have important cost-bearing consequences. Transactions of this kind are labeled idiosyncratic. The summarized results of the review are as follows. First, firms' distribution decisions often prompt examination of the make-or-buy question: Should a marketing activity be performed within the organization by company employees or contracted to an external agent? Second, manufacturers introducing an industrial product to a foreign market face a difficult decision. Should the product be marketed primarily by captive agents (the company sales force and distribution division) or independent intermediaries (outside sales agents and distribution)? Third, the authors develop a theoretical extension to the basic transaction cost model by combining insights from various theories with the TCA approach. Fourth, other such extensions are likely required for the general model to be applied to different channel situations. It is naive to assume the basic model appliesacross markedly different channel contexts without modifications and extensions. Although this study contributes to scholastic research, it is limited by several factors. First, the theoretical perspective of TCA has attracted considerable recent interest in the area of marketing channels. The analysis aims to match the properties of efficient governance structures with the attributes of the transaction. Second, empirical evidence about TCA's basic propositions is sketchy. Apart from Anderson's (1985) study of the vertical integration of the selling function and John's (1984) study of opportunism by franchised dealers, virtually no marketing studies involving the constructs implicated in the analysis have been reported. We hope, therefore, that further research will clarify distinctions between the different aspects of specific assets. Another important line of future research is the integration of efficiency-oriented TCA with organizational approaches that emphasize specific assets' conceptual definition and industry structure. Finally, research of transaction costs, uncertainty, opportunism, and switching costs is critical to future study.

• Tuberculosis and Respiratory Diseases
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• v.48 no.5
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• pp.766-772
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• 2000

Background : Pressure rise time (PRT) is the time in which the ventilator aclieves the set airway pressure in pressure-targeted modes, such as pressure control ventilation (PCV). With varying PRT, in principle, the peak inspiratory flow rate of the ventilator also varies. And if PRT is set to a shorter duration, the effective duration of target pressure level would be prolonged, which in turn would increase inspiratory tidal volume(Vti) and mean airway pressure (Pmean). We also postulated that the increase in Vti with shortening of PRT may relate inversely to the patients' basal airway resistance. Methods : In 13 paralyzed patients on PCV (pressure control 18$\pm$9.5 cm $H_2O$ $FIO_2\;0.6\pm0.3$, PEEP 5$\pm$3 cm $H_2O$, f 20/min, I : E1 : 2) with Servo 300 (Siemens-Elema, Solna, Sweden) from various causes of respiratory failure, PRT of 10 %, 5 % and 0 % were randomly applied. At 30 min of each PRT trial, peak inspiratory flow (PIF, L/sec), Vti (ml), Pmean (cm $H_2O$) and ABGA were determined. Results : At PRT 10%, 5%, and 0%, PIF were 0.69$\pm$0.13, 0.77$\pm$0.19, 0.83$\pm$0.22, respectively (p<0.001). Vti were 425$\pm$94, 439$\pm$101, 456$\pm$106, respectively (p<0.001), and Pmean were 11.2$\pm$3.7, 12.0$\pm$3.7, 12.5$\pm$3.8, respectively (p<0.001). pH were 7.40$\pm$0.08, 7.40$\pm$0.92, 7.41$\pm$0.96, respectively (p=0.00) ; $PaCO_2$ (mm Hg) were 47.4$\pm$15.8, 47.2 $\pm$15.7, 44.6$\pm$16.2, respectively (p=0.004) ; $PAO_2-PaO_2$ (mm Hg) were 220$\pm$98, 224$\pm$95, 227$\pm$94, respectively (p=0.004) ; and $V_n/V_T$ as determined by ($PaCO_2-P_E-CO_2$)/$PaCO_2$ were 0.67$\pm$0.07, 0.67$\pm$0.08, 0.66$\pm$0.08, respectively (p=0.007). The correlation between airway resistance and change of Vti from PRT 10% to 0% were r= -0.243 (p=0.498). Conclusion : Shortening of pressure rise timee during PCV was associated with increased tidal volume, increased mean airway pressure and lower $PaCO_2$.

• Tuberculosis and Respiratory Diseases
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• v.46 no.6
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• pp.803-810
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• 1999

Background : The patient's work of breathing(WOBp) during assisted ventilation may vary according to many factors including ventilatory demand of the patients and applied ventilatory setting by the physician. Pressure-controlled ventilation(PCV) which delivers gas with decelerating flow may better meet patients' demand to improve patient-ventilator synchrony compared with volume-controlled ventilation(VCV) with constant flow. This study was conducted to compare the difference in WOBp in two assisted modes of ventilation, PCV and VCV with constant flow. Methods : Ten patients with respiratory failure were included in this study. Initially, the patients were placed on VCV with constant flow at low tidal volume($V_{T,\;LOW}$)(6-8 ml/kg) or high tidal volume($V_{T,\;HIGH}$)(10-12 ml/kg). After a 15 minute stabilization period, VCV with constant flow was switched to PCV and pressure was adjusted to maintain the same tidal volume($V_T$) received on VCV. Other ventilator settings were kept constant. Before changing the ventilatory mode, WOBp, $V_T$, minute ventilation($V_E$), respiratory rate(RR), peak airway pressure (Ppeak), peak inspiratory flow rate(PIFR) and pressure-time product(PTP) were measured. Results : The mean $V_E$ and RR were not different between PCV and VCV during the study period. The Ppeak was significantly lower in PCV than in VCV during $V_{T,\;HIGH}$. HIGH ventilation(p<0.05). PIFR was significantly higher in PCV than in VCV at both $V_T$ (p<0.05). During $V_{T,\;LOW}$ ventilation, WOBp and PTP in PCV($0.80{\pm}0.37\;J/min$, $164.5{\pm}74.4\;cmH_2O.S$) were significantly lower than in VCV($1.06{\pm}0.39J/mm$, $256.4{\pm}107.5\;cmH_2O.S$)(p<0.05). During $V_{T,\;HIGH}$ ventilation, WOBp and PTP in PCV($0.33{\pm}0.14\;J/min$, $65.7{\pm}26.3\;cmH_2O.S$) were also significantly lower than in VCV($0.40{\pm}0.14\;J/min$, $83.4{\pm}35.1\;cmH_2O.S$)(p<0.05). Conclusion : During assisted ventilation, PCV with decelerating flow was more effective in reducing WOBp than VCV with constant flow. But since individual variability was shown, further studies are needed to confirm these results.