Effect of different surface treatments and ceramic primers on shear bond strength of self-adhesive resin cement to zirconia ceramic.

AIMS: To evaluate the effect of different surface treatments and ceramic primers on the shear bond strength (SBS) of self-adhesive resin cement to zirconia ceramic. MATERIALS AND METHODS: A total of 40 zirconia discs (10 mm in diameter and 3 mm in height; StarCeram Z-Med, H.C. Starck, Selb, Germany) were prepared from pre-sintered zirconia blocks. Discs were divided into two groups according to surface treatment: (a) airborne particle abrasion (sandblasting) with 50-µm Al2O3 particles and (b) 9.5% hydrofluoric acid etching. Each of these groups was subdivided into two groups according to the type of primer applied: (a) Z-Prime Plus primer and (b) Clearfil Ceramic Primer. A self-adhesive resin cement (Multilink Speed, Ivoclar Vivadent, Schaan, Liechtenstein) was used to bond with polyethylene molds. All specimens were tested at thermocycled (5000 cycles at 5-55°C for 30 s) conditions. The SBS of the luting cement to the ceramic was measured in a universal testing machine (1 mm/min). RESULTS: The sandblasted groups showed significantly higher SBS values than the acid-etched groups for both primers (P = 0.0001). Independent of the surface treatment, the Z-Prime Plus primer groups showed higher SBS values than the Clearfil Ceramic Primer groups (P = 0.0001). CONCLUSIONS: Sandblasting is a more effective method to increase bond strength on zirconia ceramics than hydrofluoric acid etching, and the application of Z-Prime Plus primer increases SBS better than Clearfil Ceramic Primer.

Nicotine toxicity to the ultrastructure of the testis in rats.

OBJECTIVE: To investigate the influence of nicotine exposure on the ultrastructure of the rat testis. MATERIALS AND METHODS: Twenty rats were injected with nicotine at a dose of 0.4 mg/100 g body weight daily for 3 months; a group of 20 control rats matched for weight and age were injected with saline only for the same duration. The testes were then harvested and examined by transmission electron microscopy. RESULTS: Rats given nicotine showed: thickening of the tunica propria, caused by an increase in the collagen fibres under the irregular basal lamina; degeneration of junctional specializations between the Sertoli cells, with malformed nuclei showing condensed chromatin; Sertoli cells with numerous polymorphic mitochondria with irregular cristae and an electron-dense matrix. The germ cells were degenerated, spermatids retained excess cytoplasm and accumulated electron-dense lipid droplets in the cytoplasm. The acrosomes were irregular and abnormally configured. CONCLUSION: There were ultrastructural alterations in rats exposed to nicotine that could be attributed to the detrimental effects of nicotine on germ cells, peritubular structures and Sertoli cells.

Ultrastructural effects of cigarette smoke on rat testis.

The purpose of this study was to investigate the ultrastructural changes taking place in the testicular tissue of adult male Wistar rats following exposure to cigarette smoke. Twenty rats were exposed to smoke in a smoking machine for 2 h daily for 60 days; 10 control rats were placed in the machine for the same amount of time but were exposed to room air. After ether anesthesia and dissection of the animals, the testes were removed and fixed in 2.5% glutaraldehyde. The sections were examined under a transmission electron microscope. Evident degeneration and dissociation of the spermatogenetic cells were common findings. Basal lamina of the tubuli seminiferi contorti was thickened and significantly irregular. Cigarette smoke inhalation damaged the seminiferous epithelium. The primary spermatocytes as well as Sertoli cells appeared to be targets for the smoke. The results indicated that cigarette smoke inhalation could cause specific lesions in the development of spermatozoon, and it might be either directly or indirectly toxic to spermatogenesis.

Long-term effects of cigarette-smoke exposure on plasma testosterone, luteinizing hormone and follicle-stimulating hormone levels in male rats.

OBJECTIVES: To determine the effects of long-term cigarette smoking on the levels of plasma testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in male adult rats and to examine morphological and histological changes in the testes. MATERIALS AND METHODS: Cigarette smoke was generated by a smoking-machine and 12 rats were exposed to cigarette smoke diluted with 90% air for 60 days (2 h/day). Twelve rats were exposed to room air only under similar conditions as controls. The concentrations of plasma testosterone, LH and FSH were measured before and after exposure using a radio-immunoassay and the testes were examined histologically. RESULTS: In rats exposed to smoke, the mean plasma testosterone level decreased significantly but there were no significant changes in testosterone in the control rats. The mean plasma LH and FSH levels of the two groups did not change significantly after exposure. In rats exposed to smoke, histological examination of the testes showed fewer Leydig cells and degeneration of the remaining cells. CONCLUSION: These results indicate that the decrease in plasma testosterone levels induced by exposure to smoke was not associated with changes in plasma gonadotrophin levels. The decrease in testosterone levels may be related to the toxic effects of smoke on Leydig cells.