Influence of intracoronal bleaching agents on the ultimate strength and ultrastructure morphology of dentine.

OBJECTIVE: To evaluate the effects of intracoronal bleaching on ultimate tensile strength (UTS) of sound and etched dentine and its ultrastructure morphology. METHODOLOGY: Bovine dentine specimens with (e) or without previous etching with 37% phosphoric acid for 15 s were used for the intracoronal bleaching experiments. Teeth were randomly assigned to five treatments (n = 10): (C) control--no bleaching, (SP) sodium perborate, (CP) 35% carbamide peroxide, (25% HP) 25% hydrogen peroxide and (35% HP) 35% hydrogen peroxide. Bleaching was performed four times within a 72 h interval and afterwards, dentine pulp chamber blocks were obtained. The blocks were sectioned in 0.7 mm-thick slices and these were trimmed to reduce the inner dentine to a dumbbell shape with a cross-sectional area of 0.8 mm(2). Specimens were tested with the microtensile method (0.5 mm min(-1)) and data were analysed (two-way ANOVA-Tukey test, P < 0.05). Additional teeth were prepared for transmission electron microscopy (TEM) to evaluate dentine ultramorphology. RESULTS: The mean values of the UTS (SD) in MPa for sound dentine were: C = 48.3(8.5)a, SP = 34.6 (8.2)b, CP = 32.9 (8.9)b, 25% HP = 28.0(4.6)b, 35% HP = 26.4(6.6)b, and pre-etched dentine: Ce = 38.9(13.8)a, SPe = 31.3 (9.3)ab, CPe = 28.4 (6.2)ab, 25% HPe = 30.0 (7.9)ab, 35% HPe = 19.9(4.6)b. Significant differences between the means are indicated by the letters. TEM observations exhibited demineralization areas for all bleaching treatments. CONCLUSION: Bleaching decreased dentine UTS after treatment. Pre-etched not-bleached dentine (Ce) presented UTS similar to pre-etched bleached dentine, except for 35% HPe. The decrease of UTS of bleached dentine could be attributed to ultrastructural alterations such as loss of inorganic components.

In vitro microleakage of composite restorations after nonvital bleaching.

OBJECTIVE: After bleaching treatment, esthetic restorations often need to be replaced due to color changes. Some papers have shown alterations in the bond of adhesive restorations to bleached teeth. The purpose of this study was to evaluate tooth and resin composite adhesion when submitted to nonvital dental bleaching. METHOD AND MATERIALS: One hundred and twenty bovine teeth were assigned to 3 groups (n = 40); paste of sodium perborate and water; 37% carbamide peroxide gel; and no bleaching (control). After 3 weeks of continuous bleaching treatment, standardized Class V cavities were prepared at the cementoenamel junction and restored with Single Bond adhesive system and Z100 resin composite. The samples were thermocycled 1,500 times (5 +/- 1/55 +/- 1 degrees C) with a 1-minute dwell time. Then, they were immersed in a 2% methylene blue solution (pH 7) for 4 hours, sectioned, and analyzed by stereomicroscopy. Microleakage analyses were done, using scores from 0 to 4, considering leakage on the incisal wall (enamel) and the cervical wall (dentin). Data were analyzed by Kruskal-Wallis and Mann-Whitney tests (alpha = 0.05). RESULTS: The results showed that sodium perborate and carbamide peroxide gel significantly increase the microleakage in Class V resin composite restorations to dentin but not to enamel margins. CONCLUSION: The risk of microleakage in dentin margins is increased soon after bleaching treatment.

Corticosteroids in the treatment of the acute phase of Kawasaki disease.

OBJECTIVES: Corticosteroids are considered to be contraindicated during the acute phase of Kawasaki disease (KD) based on unfavorable results in early studies. In our hospital, however, corticosteroids have been used in some cases of KD with satisfactory results. We analyzed outcomes of patients with KD treated with or without corticosteroids. STUDY DESIGN: Medical records of 299 children with KD treated with one of the 4 regimens were reviewed retrospectively. Regimen 1 consisted of aspirin, dipyridamole, and propranolol; regimen 2 was regimen 1 plus prednisolone, 2 mg/kg/d, for 1 week, followed by tapering over 2 weeks; regimen 3 was regimen 1 plus intravenous gamma-globulin (IVGG), 200 or 400 mg/kg/d, for 5 consecutive days; and regimen 4 was regimen 1 plus both prednisolone and IVGG. RESULTS: Although patients treated with regimens 2 and 4 were more ill at presentation than those treated with regimens 1 and 3, respectively, the duration of fever was shorter in the former patient groups (P =.0013). Coronary aneurysms developed least frequently in patients treated with regimen 4 and less frequently with regimen 2 than with regimen 1 (P =.0730). Multiple regression analysis showed significant reductions of fever and coronary aneurysm incidence with prednisolone (P <.0001 and P =.0307, respectively). CONCLUSION: Our data suggest a possible role of corticosteroids in the treatment of the acute phase of KD.