Effects of plasma-induced grafting modification on the adhesive strength and mechanical properties of fiber posts.

OBJECTIVE: This study aimed to assess the effects of plasma grafting modification on the micro-push-out adhesive strength and mechanical properties of fiber posts and to assess the stability of these treatment effects. MATERIALS AND METHODS: Glass-fiber posts were divided into four groups based on the treatment methods used, as follows: (1) Group NT: no treatment; (2) Group PT: Helium (He) plasma treatment; (3) Group PIG: He-plasma-induced post-irradiation grafting; and (4) Group SIG: He-plasma-induced syn-irradiation grafting. The treated fiber posts were bonded using self-adhesive resin cement exposure to air for 0, 1, 6 or 12 hours separately after surface treatment. Micro-push-out adhesive strength, flexural modulus, and flexural strength were measured. RESULTS: Plasma treatment, post-irradiation grafting, and syn-irradiation grafting improved adhesive strength at the 0-hours level. However, the improved adhesive strength disappeared in group PT after exposure for one or more hours. In group PIG, the adhesive strength after 1-hour exposure was 20.5% lower than that of 0-hour exposure (adhesive immediately after treatment), and no statistically significant differences in adhesive strength were observed between the 1, 6, and 12-hour exposure. In group SIG, no statistically significant differences in adhesive strength were observed among the 0, 1, and 6-hour exposure. Although the adhesive strength was 23% lower at the 12-hour exposure than that of 0-hour exposure in group SIG, the adhesive strength of fiber posts received syn-irradiation grafting still presented the best adhesive strength compared with the other treatment methods. The three-point flexural modulus and strength remained unaffected by the treatment methods used. CONCLUSIONS: Plasma-induced syn-irradiation grafting provided the ideal improvement and stability in adhesive strength in fiber posts. In addition, plasma-induced grafting modification successfully overcame the surface aging effect caused by plasma treatment alone without affecting the bulk mechanical properties of fiber posts.

[Effect of SiO2-ZrO2 slurry coating on shear bond strength of zirconia to resin cement].

Objective: To evaluate the effect of shear bond strength between resin cement and zirconia using SiO2-ZrO2 slurry coating. Methods: One hundred and forty pre-sintered zirconia discs were randomly divided into seven groups (n=20) according to the surface treatments: AS (as-sintered), SB (sand blasting with Al2O3), 2SiO2-1ZrO2 (2∶1 mole ratio SiO2-ZrO2 coating), 1SiO2-1ZrO2 (mole ratio 1∶1 SiO2-ZrO2 coating), 1SiO2-2ZrO2 (mole ratio 1∶2 SiO2-ZrO2 coating), 1SiO2-3ZrO2 (mole ratio 1∶3 SiO2-ZrO2 coating), 1SiO2-4ZrO2 (mole ratio 1∶4 SiO2-ZrO2 coating). Each zirconia disc was bonded to composite resin cylinder using resin cement. All specimens were stored in distilled water (37 ℃, 24 h). Each group was divided into two subgroups in which half specimens were tested using universal testing machine and another half specimens accepted artificial aging of 5 000 times thermocycling then tested. Scaning electron microscopy (SEM) was used to observe the micro-morphology of coating surface etched by hydrofluoric acid,then the coating thickness was measured. Results: Before artificial aging, 1SiO2-1ZrO2 showed a higher shear bond strength [(41.69±6.28) MPa] than all the other group (P<0.05). 1SiO2-2ZrO2 gained a higher strength than AS, SB, 1SiO2-3ZrO2 and 1SiO2-4ZrO2 (P<0.05). However, 1SiO2-2ZrO2 did not get a significant higher shear bond strength than 2SiO2-1ZrO2 (P>0.05). No significant differences were found among SB, 2SiO2-1ZrO2 and 1SiO2-3ZrO2 (P>0.05). After artificial aging, shear bond strength of all groups were decreased significantly besides 2SiO2-1ZrO2. 2SiO2-1ZrO2, 1SiO2-1ZrO2 and 1SiO2-2ZrO2 [(24.13±5.50), (22.28±4.40), (23.11±4.80) MPa] showed higher shear bond strength than SB and 1SiO2-3ZrO2 (P<0.05),no intergroup differences were observed (P>0.05). Shear bond strength of AS and 1SiO2-4ZrO2 fell to 0 MPa approximately. The SEM images of etched coating surface showed contraction fissure due to different thermal expansion coefficient between SiO2 and ZrO2 and intercrystal pores of zirconia. The thickness of coating was measured to be less than 30 µm. Conclusions: Mole ratio 1∶1 SiO2-1ZrO2 slurry coating showed the highest shear bond strength of resin cement to zirconia.

[Effects of zirconia micron coating on the proliferation and differentiation of osteoblasts].

Objective: To investigate the effects of zirconia micro coating on the proliferation and differentiation of osteoblasts on the surface of zirconia ceramic, and to provide a strategy for zirconia implant surface treatment. Methods: Forty tablets of zirconia ceramic, with the diameter of 15 mm and the thickness of 1.5 mm, were prepared. Then, twenty tablets polished by water sandpaper were taken as the control group, and 20 pieces of the zirconia coating after sintering micron were taken as the experimental group. The micromorphology of the surface of the two groups were observed by scanning electron microscope. The cell morphology after inoculation with MC3T3-E1 of osteoblasts on the surface of the material was investigated for 1, 3, and 5 days by scanning electron microscope. The cell proliferation was detected at 1 and 3 days by methyl thiazolyl tetrazolium. The cell differentiation ability was detected at 3 and 7 days by real-time quantitative PCR. Statistical analysis was conducted by independent sample t test. Results: After coating with zirconia micron particles, pores with the diameter of 1-20 µm could be observed on the surface of the test group of tiles through high temperature sintering. The growth of osteoblasts on the surface of the ceramic chip in the test group and control group exhibited the similar cell morphology. As they were cultured for 1 day, the experimental group exhibited a similar quality of cells as those in the test group (P>0.05). After 3 days' incubation, comparing with the cell quality of the test group (1.067 ± 0.077) (P<0.05), the quality of osteoblasts on the surface of zirconia ceramics coating increased to 1.763±0.165, and the expression of mRNA in alkaline phosphatase (ALP), osteopotin (OPN) and osteocalcin (OCN) also increased with the amount of 1.63±0.28, 1.99±0.41 and 1.60±0.30, respectively, compared with the test group (1.00± 0.00) (P<0.05). Seven days later, the expression of mRNA in Runt-related transcription factor-2 (RNUX2) (1.33±0.19), special AT-rich sequence binding protein-2 (SATB2) (1.64 ± 0.36), as well as alkaline phosphatase (ALP) (1.78±0.40), OPN (2.25±0.36), and OCN (1.88±0.21), showed a remarkably increase compared with the test group (1.00±0.00) (P<0.05). Conclusions: Zirconia micro coating on the surface of zirconia ceramics promoted the proliferation and differentiation of osteoblasts adhered.

Interleukin-12 cDNA skin transfection potentiates human papillomavirus E6 DNA vaccine-induced antitumor immune response.

Human papillomaviruses are associated with >90% of all cases of uterine cervical tumors. The E6 and E7 oncoproteins of human papillomavirus are potentially ideal targets of immune therapy for cervical cancer, because their expression is necessary for cellular transformation. Although both E6 and E7 proteins contain numerous predicted cytotoxic T lymphocyte (CTL) epitopes that are capable of binding to human leukocyte antigens, the majority of earlier in vivo tumor rejection studies have focused on E7. We show here that gene gun-mediated skin transfection of plasmid vector encoding the nontransforming, amino-terminal half of E6 resulted in the induction of E6-specific CTL activity and tumor rejection in a murine model. The use of recombinant murine interleukin-12 (rmIL-12) as a vaccine adjuvant has been shown to result in both an enhancement and suppression of immune responses, depending upon the doses of rmIL-12 and the experimental systems used. We demonstrate here that local expression of transgenic mIL-12 at the E6 DNA vaccination site potentiated E6-specific CTL responses and increased vaccine-induced antitumor therapeutic efficacy. Our results indicate that transfection of the mIL-12 gene at the vaccination site may represent an attractive adjuvant for cancer gene immunotherapy.