Evaluation of the effect of the bleaching agent and the subsequent application of sodium fluoride on intra-coronal dentine microhardness / Avaliação do efeito do agente clareador e da subseqüente aplicação de fluoreto de sódio na microdureza da dentina intracoronária

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The aim of the present study was to evaluate the microhardness of intra-coronal dentine submitted to bleaching with 38% hydrogen peroxide, photo-activated with LED-Laser and followed by the application of 2% sodium fluoride gel or 5% varnish. Crowns of 45 human maxillary canines were sectioned in the buccal-lingual direction and a sample of 25 mm of internal dentine obtained from each crown hemi-section. The 90 samples were embedded in acrylic resin blocks and randomly divided in 3 groups: GI- no bleaching (control); GII- bleaching without LED-Laser light; GIII-bleaching with LEDLaser light. Each group was subdivided in 3 (n=10): A- no fluoride application; Bapplication of 2% sodium fluoride gel; C- application of 5% sodium fluoride varnish. The bleaching protocol used 38% hydrogen peroxide, followed or not by LED-Laser application during 45 s, and was repeated 3 times (10 minutes each). The specimens were washed in distilled water during 10 min, dried with gauze and received a thin layer of sodium fluoride on the dentine, during 4 min, removed with 5 mL of distilled water. The internal surfaces were made flat with 280 and 400 grit SIC paper, and polished with 1200 grit SIC paper and aluminum oxide. The specimens were submitted to the microhardness Knoop test with a 25 g load cell. The Tukey test showed a significant decrease (p<0.05) in microhardness of the specimens that were bleached and photoactivated (54.8111.48) or not with LED-Laser (58.0411.40), and were statistically different (p<0.05) from the specimens not bleached (69.0110.19) that presented the highest values. The specimens that did not receive sodium fluoride application presented the lowest hardness results (55.0911.47), and were statistically similar (p>0.05) to the group that received 2% sodium fluoride gel (59.3912.30), and statistically different (p<0.05) from the specimens that received 5% sodium fluoride (67.3810.82). The interaction between bleaching and sodium fluoride showed a statistically significant difference (p<0.05), with the reestablishment of microhardness, in the specimens that received 5% sodium fluoride varnish application, regardless of photo-activation, when compared to the specimens that received no sodium fluoride or 2% sodium fluoride application. It can be concluded that bleaching with 38% sodium hypochlorite, activated or no by the LED-laser system, reduced the microhardness of intra-coronal dentine and that the application of 5% sodium fluoride varnish reestablished the hardness values to the level of non-bleached teeth.

ASSUNTO(S)

fluoride dentistry dentistry odontologia endodontia endodontics clareamento - odontologia odontologia flúor - odontologia bleaching denstistry

ACESSO AO ARTIGO

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