Influence of surface treatment on bonding of resin luting cement to CAD/CAM composite blocks

The aim of this study was to determine the influence of different surface treatments of CAD/CAM composite blocks on bonding effectiveness of resin cements, based on the shear bond strength test and the surface science examination. Specimens were fabricated from two types of CAD/CAM composite blocks (Cerasmart and VITA Enamic), and the specimen surfaces were alumina sandblasted. Specimen surfaces were treated with i) silane, ii) primer, and iii) silane+primer, then two types of cements (Block HC Cem and Super Bond) were bonded. After 24 h storage, bond strengths were measured. Surface free energy measurements were performed of the treated CAD/CAM composite blocks surfaces. The groups ii) and iii) showed significantly higher bond strengths than the group i), apart from VITA Enamic with Block HC Cem. Although the total surface free energy showed different trends in different surface treatments, a similar trend was found in both CAD/CAM composite blocks.

Influence of air-powder polishing on bond strength and surface-free energy of universal adhesive systems

The influences of air-powder polishing with glycine or sodium bicarbonate powders on shear bond strengths (SBS) and surface-free energies of universal adhesives were examined. Scotchbond Universal Adhesive (SU, 3M ESPE), G-Premio Bond (GP, GC), Adhese Universal (AU, Ivoclar Vivadent), and All-Bond Universal (AB, Bisco) were used in this study. Bovine dentin surfaces were air polished with glycine or sodium bicarbonate powders prior to the bonding procedure, and resin pastes were bonded to the dentin surface using universal adhesives. SBSs were determined after 24-h storage in distilled water at 37°C. Surface-free energy was then determined by measuring contact angles using three test liquids on dentin surfaces. Significantly lower SBSs were observed for dentin that was air-powder polished and surface-free energies were concomitantly lowered. This study indicated that air-powder polishing influences SBSs and surface-free energies. However, glycine powder produced smaller changes in these surface parameters than sodium bicarbonate.

Enamel remineralization effect of a dentifrice containing calcium sodium phosphosilicate: an optical coherence tomography observation

OBJECTIVE

The purpose of this study was to examine the effects of a dentifrice containing 5% calcium sodium phosphosilicate (CSP) on the remineralization of the enamel using optical coherence tomography (OCT).

MATERIALS AND METHODS

Bovine incisors were sliced and shaped in a rectangular form. One group of five specimens was treated with undersaturated 0.1 M lactic acid buffer solution (pH 4.75) for 10 min and then placed in artificial saliva (pH 7.0) (De group). Other specimens were stored in solutions of toothpaste containing CSP for 10 min, followed by 10-min immersion in the lactic acid buffer solution twice a day before storage in artificial saliva (CSP group). An additional group was stored in only artificial saliva (control group). OCT imaging on the selected location of the enamel surface was performed. The peak intensity and width at 1/e² were recorded in each of the six areas on the sample and averaged, and the sample size of each group was six. The integrated value in units (dB × μm) was calculated in the area of peak intensity. The data for each group was subjected to one-way repeated-measures ANOVA and Tukey HSD tests (α = 0.05).

RESULTS

The changes in integrated values of each group were different. A slight but significant increase in the integrated value was observed in the control group, whereas a slight but significant decrease in the value was observed the De group. Integrated values increased in the CSP group.

CONCLUSIONS

Remineralization occurred upon immersion in the toothpaste containing CSP.

Effects of long-term injection of steroid hormone on soluble protein in rat muscles and organellae

Steroid hormone (dexamethasone, 0.1 mg/kg/day) was injected into Wistar strain rats, and its effect on the weight of organellae and skeletal muscles was studied. Steroid was injected for 20, 30 and 40 weeks, and a de-steroid group was obtained by interrupting the steroid injections for three weeks. The body weight of the injected rats decreased by 40 to 60% from that of the control, even when food intake per body weight was increased by more than 20%. The weight of organellae (heart, liver and adrenal glands) apparently decreased. Nevertheless, the weight per body weight tended to recover to the control level in the de-steroid group. Muscle atrophy of the proximal muscles, the rectus femoris and the semimembranosus muscles was observed in the steroid group. Remarkable atrophy appeared in the semimembranosus muscle, named type II fiber, with 40% to 60% of control at the 30th and 40th weeks and the recovery rate of this weight was determined in only 80% in the de-steroid group. A decrease of the 40,000 to 60,000 MW polypeptides of serum and muscle soluble protein fraction was shown in the 40-week group. These results suggested that acceleration of glycolysis, glyconeogenesis and protein catabolism were induced after long-term steroid injection.

Effects of relative metabolic rate and heart rate variation on the performance of flight attendants

The main work of the cabin attendants in an actual flight in service for passengers. The effects of flight attendant duties in flight differ from the effects of the same tasks performed on the ground. In this study, the relative metabolic rate (RMR) and heart rate (HR) of cabin attendants in a cruising aircraft galley and cabin are compared with those of a crew working in a mock-up apparatus on the ground. The types of work tested are: (a) oshibori (steamed towel) service, (b) soft drink service, (c) setting meal tray, (d) putting casserole on tray, (e) meal tray service, (f) walking on aisle. The RMR at each type of work during flight is as indicated: (a) 1.07-2.10, (b) 1.08-1.54, (c) 1.37-1.82, (d) 2.57-3.50, (e) 2.11-3.10 and (f) 1.84. The range of HR was: (a) 105-120, (b) 90-110, (c) 90-120, (d) 100-130 and 100-140 beats/min. In most cases, the RMR and HR levels of work done in the mock-up were lower than those recorded in flight. These results suggest that the oxygen intake of work done in flight is greater than that on a mock-up. One of the reasons might be that the cabin barometric pressure (ca. 660 torr or cabin altitude ca. 1,500 m) or an aisle inclination of about 3 degrees caused a decrease in the efficiency of oxygen intake during flight.