• Applied Chemistry for Engineering
• /
• v.3 no.1
• /
• pp.148-155
• /
• 1992

For the enhancement of the concrete durability, we developed high - durable portland cement (ACTPC) by physical treatment of ordinary portland cement with asphalt and carbon black. In this research, the hydration reaction characteristics of ACTPC were studied by using SEM, X-Ray, Conduction Micro Calolimeter etc. When the ACTPC is mixed with water, it is believed the asphalt films on cement particles suppress the early stage of hydration reactions of cements, because the films hinder the contact with water and the elusion of soluble ions from particles. But the carbon blacks on the cement particles accelerated the hydration reactions of cement after a while, because the micro particles can be used as seed crystals in $CaO-SiO_2-H_2O$ gel formation.

• The Journal of Advanced Prosthodontics
• /
• v.12 no.4
• /
• pp.197-203
• /
• 2020

PURPOSE. The aim of this study was to evaluate the effect of multiple firings on the bond strength between yttriatetragonal zirconia polycrystals (Y-TZP) and 2 types of resin cements. MATERIALS AND METHODS. Sixty 3Y-TZP specimens (LAVA Frame Multi) were divided into 3 groups depending on the following firing procedures: (1) 2-firing cycles, (2) 5-firing cycles, (3) 10-firing cycles. Two samples from each group were investigated by using SEM to determine the morphological changes. All specimens were treated with 125 ㎛ airborne-particle abrasion and the surface roughness of each specimen was measured. The specimens from each firing group were then further divided into 2 subgroups (n = 9) to apply 2 types of resin cement (MDP-free resin cement: RelyX Unicem-RU, and MDP containing resin cement: Panavia F 2.0-PA). The shear bond strength (SBS) test was performed and failure types of all the debonded specimens were classified by using a stereomicroscope as adhesive, cohesive, and mixed. The statistical analysis of surface roughness and SBS data were performed by using 1-way ANOVA and 2-way ANOVA followed by Tukey-HSD tests (α=.05). Failure modes were calculated as a percentage for each group. RESULTS. The bond strength of RU and PA to the specimens obtained with 2 firings were not statistically different from each other (P=.1). However, the SBS values of PA were found to be significantly higher than RU for the specimens obtained with 5 and 10 firing cycles (P=.001 and P=.02, respectively). Surface roughness analysis revealed no statistical difference between groups (P=.2). The SEM analysis of samples fired 5- and 10- times showed irregularities and boundary loss in zirconia grains, and empty spaces between zirconia grains. CONCLUSION. The bond strength of PA cement was higher than that of RU to the zirconia subjected to repeated firings (5 and 10 firing cycles). When zirconia is subjected to multiple firings, using MDP-containing resin cement can be recommended.

• The Journal of Advanced Prosthodontics
• /
• v.5 no.2
• /
• pp.104-109
• /
• 2013

PURPOSE. Among the surface treatment methods suggested to enhance the adhesion of resin cement to fiberreinforced composite posts, conflicting results have been obtained with silanization. In this study, the effects of silanization, heat activation after silanization, on the bond strength between fiber-reinforced composite post and resin cement were determined. MATERIALS AND METHODS. Six groups (n=7) were established to evaluate two types of fiber post (FRC Postec Plus, D.T. Light Post) and three surface treatments (no treatment; air drying; drying at $38^{\circ}C$). Every specimen were bonded with dual-curing resin cement (Variolink N) and stored in distilled water for 24 hours at $37^{\circ}C$. Shear-bond strength (MPa) between the fiber post and the resin cement were measured using universal testing device. The data were analyzed with 1-way ANOVA and by multiple comparisons according to Tukey's HSD (${\alpha}$=0.05). The effect of surface treatment, fiber post type, and the interactions between these two factors were analyzed using 2-way ANOVA and independent sample T-tests. RESULTS. Silanization of the FRC Postec Plus significantly increased bond strength compared with the respective non-treated control, whereas no effect was determined for the D.T. Light Post. Heat drying the silane coupling agent on to the fiberreinforced post did not significantly improve bond strength compared to air-syringe drying. CONCLUSION. The bond strength between the fiber-reinforced post and the resin cement was significantly increased with silanization in regards to the FRC Postec Plus post. Bond strength was not significantly improved by heat activation of the silane coupling agent.

• Advances in concrete construction
• /
• v.3 no.3
• /
• pp.203-221
• /
• 2015

This paper presents the results of a study undertaken to investigate the enhancement of concrete strength using Silpozz and Rice Husk Ash (RHA). The total percentage of supplementary cementitious material (SCM) substituted in this study was 20%. Six different concrete mixes were prepared such as without replacement of cement with silpozz and RHA (0% silpozz and 0% RHA) is treated as conventional concrete, whereas in other five concrete mixes cement was replaced by 20% of silpozz and RHA as (0% silpozz and 20% RHA), (5% silpozz and 15% RHA), (10% silpozz and 10% RHA), (15% silpozz and 5% RHA) and (20% silpozz and 0% RHA) with decreasing water-binder (w/b) ratio i.e. 0.375, 0.325 and 0.275 and increasing super plasticiser dose. New generation polycarboxylate base water reducing admixture i.e., Cera Hyperplast XR-W40 was used in this study. The results of this research indicate that as w/b decreases, super plasticiser dose need to be increased so as to increase the workability of concrete. The effects of replacing cement by silpozz and RHA on the compressive strength, split tensile strength and flexural strength were evaluated. The concrete mixture with different combination of silpozz and RHA gives higher strength as compared to control specimen for all w/b ratios and also observed that the early age strength of concrete is more as compared to the later age strength. It is also observed that the strength enhancement of concrete mixture prepared with the combination of cement, silpozz and RHA is higher as compared to the concrete mixture prepared with cement and silpozz or cement and RHA.

• Clinics in Shoulder and Elbow
• /
• v.25 no.3
• /
• pp.202-209
• /
• 2022

Background: The purpose of our study was to investigate short-term outcomes of two-stage reverse total shoulder arthroplasty (RTSA) with an antibiotic-loaded cement spacer for shoulder infection. Methods: Eleven patients with shoulder infection were treated by two-stage RTSA following temporary antibiotic-loaded cement spacer. Of the 11 shoulders, nine had pyogenic arthritis combined with complex conditions such as recurrent infection, extensive osteomyelitis, osteoarthritis, or massive rotator cuff tear and two had periprosthetic joint infection (PJI). The mean follow-up period was 29.9 months (range, 12-48 months) after RTSA. Clinical and radiographic outcomes were evaluated using the visual analog scale (VAS) score for pain, American Shoulder and Elbow Surgeons (ASES) score, subjective shoulder value (SSV), and serial plain radiographs. Results: The mean time from antibiotic-loaded cement spacer to RTSA was 9.2 months (range, 1-35 months). All patients had no clinical and radiographic signs of recurrent infection at final follow-up. The mean final VAS score, ASES score, and SSV were significantly improved from 4.5, 38.6, and 29.1% before RTSA to 1.7, 75.1, and 75.9% at final follow-up, respectively. The mean forward flexion, abduction, external rotation, and internal rotation were improved from 50.0°, 50.9°, 17.7°, and sacrum level before RTSA to 127.3°, 110.0°, 51.8°, and L2 level at final follow-up, respectively. Conclusions: Two-stage RTSA with antibiotic-loaded cement spacer yields satisfactory short-term clinical and radiographic outcomes. In patients with pyogenic arthritis combined with complex conditions or PJI, two-stage RTSA with an antibiotic-loaded cement spacer would be a successful approach to eradicate infection and to improve function with pain relief.

• Geomechanics and Engineering
• /
• v.21 no.5
• /
• pp.433-445
• /
• 2020

The weakening and softening behavior of soft clay subjected to cyclic loading due to the build-up of excess pore water pressure is well-known. During the design stage of the foundation of highways and coastal high-rise buildings, it is important to study the mechanical behavior of marine soils under cyclic loading as they undergo greater settlement during cyclic loading than under static loading. Therefore, this research evaluates the cyclic stress-strain and shear strength of untreated and treated marine clay under the effects of wind, earthquake, and traffic loadings. A series of laboratory stress-controlled cyclic triaxial tests have been conducted on both untreated and treated marine clay using different effective confining pressures and a frequency of 0.5 and 1.0 Hz. In addition, treated samples were cured for 28 and 90 days and tested under a frequency of 2.0 Hz. The results revealed significant differences in the performance of treated marine clay samples than that of untreated samples under cyclic loading. The treated marine clay samples were able to stand up to 2000 loading cycles before failure, while untreated marine clay samples could not stand few loading cycles. The untreated marine clay displayed a higher permanent axial strain rate under cyclic loading than the treated clay due to the existence of new cementing compounds after the treatment with recycled tiles and low amount (2%) of cement. The effect of the effective confining pressure was found to be significant on untreated marine clay while its effect was not crucial for the treated samples cured for 90 days. Treated samples cured for 90 days performed better under cyclic loading than the ones cured for 28 days and this is due to the higher amount of cementitious compounds formed with time. The highest deformation was found at 0.5 Hz, which cannot be considered as a critical frequency since smaller frequencies were not used. Therefore, it is recommended to consider testing the treated marine clay using smaller frequencies than 0.5 Hz.

• Journal of Korean Neurosurgical Society
• /
• v.48 no.6
• /
• pp.490-495
• /
• 2010

Objective : Bone cement augmentation procedures such as percutaneous vertebroplasty and balloon kyphoplasty have been shown to be effective treatment for acute or subacute osteoporotic vertebral compression fractures. The purpose of this study was to determine the efficacy of bone cement augmentation procedures for long standing osteoporotic vertebral compression fracture with late vertebral collapse and persistent back pain. Methods : Among 278 single level osteoporotic vertebral compression fractures that were treated by vertebral augmentation procedures at our institute, 18 consecutive patients were included in this study. Study inclusion was limited to initially, minimal compression fractures, but showing a poor prognosis due to late vertebral collapse, intravertebral vacuum clefts and continuous back pain despite conservative treatment for more than one year. The subjects included three men and 15 women. The mean age was 70.7 with a range from 64 to 85 years of age. After postural reduction for two days, bone cement augmentation procedures following intraoperative pressure reduction were performed. Imaging and clinical findings, including the level of the vertebra involved, vertebral height restoration, injected cement volume, local kyphosis, clinical outcome and complications were analyzed. Results : The mean follow-up period after bone cement augmentation procedures was 14.3 months (range 12-27 months). The mean injected cement volume was 4.1 mL (range 2.4-5.9 mL). The unipedicular approach was possible in 15 patients. The mean pain score (visual analogue scale) prior to surgery was 7.1, which decreased to 3.1 at 7 days after the procedure. The pain relief was maintained at the final follow up. The kyphotic angle improved significantly from $21.2{\pm}4.9^{\circ}$ before surgery to $10.4{\pm}3.8^{\circ}$ after surgery. The fraction of vertebral height increased from 30% to 60% after bone cement augmentation, and the restored vertebral height was maintained at the final follow up. There were no serious complications related to cement leakage. Conclusion : In the management of even long-standing osteoporotic vertebral compression fracture for over one year, bone cement augmentation procedures following postural reduction were considered safe and effective treatment in cases of non-healing evidence.

• The Journal of Advanced Prosthodontics
• /
• v.9 no.2
• /
• pp.130-137
• /
• 2017

PURPOSE. The purpose of this study was to evaluate the effect of nano-structured alumina surface coating on shear bond strength between Y-TZP ceramic and various dual-cured resin cements. MATERIALS AND METHODS. A total of 90 disk-shaped zirconia specimens (HASS CO., Gangneung, Korea) were divided into three groups by surface treatment method: (1) airborne particle abrasion, (2) tribochemicalsilica coating, and (3) nano-structured alumina coating. Each group was categorized into three subgroups of ten specimens and bonded with three different types of dual-cured resin cements. After thermocycling, shear bond strength was measured and failure modes were observed through FE-SEM. Two-way ANOVA and the Tukey's HSD test were performed to determine the effects of surface treatment method and type of cement on bond strength (P<.05). To confirm the correlation of surface treatment and failure mode, the Chi-square test was used. RESULTS. Groups treated with the nano-structured alumina coating showed significantly higher shear bond strength compared to other groups treated with airborne particle abrasion or tribochemical silica coating. Clearfil SA Luting showed a significantly higher shear bond strength compared to RelyX ARC and RelyX Unicem. The cohesive failure mode was observed to be dominant in the groups treated with nano-structured alumina coating, while the adhesive failure mode was prevalent in the groups treated with either airborne particle abrasion or tribochemical silica coating. CONCLUSION. Nano-structured alumina coating is an effective zirconia surface treatment method for enhancing the bond strength between Y-TZP ceramic and various dual-cured resin cements.

• Restorative Dentistry and Endodontics
• /
• v.3 no.1
• /
• pp.17-21
• /
• 1977

After a vital pulpotomy in dogs' teeth, the responses of the remaining pulp tissue under calcium hydroxide and formocresol were studied histologically. The class I and V cavities were prepared on the teeth and the pulp was amputated. Calcium hydroxide and formocresol were placed over the amputated tissue and the cavities were sealed with zine oxide eugenol cement and zinc phosphate cement. Animals. were sacrifice after 1, 2, and 3 weeks following the operation. The teeth were decalcfied, sectioned and stained with hematoxylin and eosin. Microscopic examination reveals as follows; 1. Healing of the pulp at the amputation site did not occur in the pulps treated with formocresol. 2. At one week, a thin layer of darker staining tissues just below the necrotic zone was presented in the pulps treated with formocresol. In this stage the tissues beneath the darker staining layer were normal. 3. At two weeks, the cells of the palest staining layer were showed indistinct nucleus which suggested the karyolysis and the karyorrhexis in the pulps treated with formocoresol. As reached to the middle third of the pulp, the odontoblasts were scarcely evident or missed in this stage. 4. At three weeks, the necrotic zone was reached to the middle third of the pulp canal. The cells beneath the zone showed massive infiltration of inflammatory cells in the pulps treated with formocresol. 5. Dentin bridge in the control group was deposited below the necrotic zone from the two. weeks later. 6. Normal tissues were observed ill the apical third of all. the dental pulps in all case of calcium hydroxide and formocresol.

• 한국도로학회:학술대회논문집
• /
• 2009.11a
• /
• pp.391-396
• /
• 2009