In Vitro Penetration of the Pulp Chamber by Three Brands of Carbamide Peroxide

Abstract: Purpose : Vital tooth bleaching has become a popular procedure for whitening teeth. Most home bleaching products contain 10% carbamide peroxide. The purpose of this in vitro study was to measure the quantity of hydrogen peroxide that reaches the pulp chamber from three carbamide peroxide products: Opalescence™, Sparkle™, and Rembrandt™.
Materials and Methods : Seventy roots of extracted premolars were amputated approximately 3 mm apical to the cementoenamel junction, and the pulp tissues were removed. They were divided into three experimental groups (n = 20) and a control group of 10 teeth. An acetate buffer solution was placed in the pulp chamber before the crown was exposed to the bleaching agent at 37°C for 25 minutes. The buffer solution was removed and reacted with leukocrystal violet and horseradish peroxidase. The optical density of blue color that developed was measured at a wavelength of 596 nm and read from a standard curve for hydrogen peroxide quantity.
Results : The measured amounts of hydrogen peroxide were 3.605 ± 1.405,1.282 ± 0.762, and 0.339 ± 0.251 pg for the Opalescence™, Sparkle™, and Rembrandt™ groups, respectively. A statistically significant difference in the hydrogen peroxide levels was observed by analysis of variance ( p < .05) among the three groups. It was concluded that the penetration of commercial bleach ing products was different even though the products were labeled as having the same 10% carbamide peroxide.     

Angioarchitecture of the coeliac sympathetic ganglion complex in the common tree shrew (Tupaia glis)

The angioarchitecture of the coeliac sympathetic ganglion complex (CGC) of the common tree shrew ( Tupaia glis ) was studied by the vascular corrosion cast technique in conjunction with scanning electron microscopy. The CGC of the tree shrew was found to be a highly vascularised organ. It normally received arterial blood supply from branches of the inferior phrenic, superior suprarenal and inferior suprarenal arteries and of the abdominal aorta. In some animals, its blood supply was also derived from branches of the middle suprarenal arteries, coeliac artery, superior mesenteric artery and lumbar arteries. These arteries penetrated the ganglion at variable points and in slightly different patterns. They gave off peripheral branches to form a subcapsular capillary plexus while their main trunks traversed deeply into the inner part before branching into the densely packed intraganglionic capillary networks. The capillaries merged to form venules before draining into collecting veins at the peripheral region of the ganglion complex. Finally, the veins coursed to the dorsal aspect of the ganglion to drain into the renal and inferior phrenic veins and the inferior vena cava. The capillaries on the coeliac ganglion complex do not possess fenestrations.