Cristiane Franco Pinto

Effect of 10% carbamide peroxide bleaching on sound and artificial enamel carious lesions

This study evaluated the effect of 10% carbamide peroxide (CP) bleaching on Knoop surface microhardness (KHN) and morphology of sound enamel and enamel with early artificial caries lesions (CL) after pH-cycling model (pHcm). Human dental enamel blocks were randomly divided into 6 groups (n=10): 1 - sound enamel bleached (S) with CP (Rembrandt/Den-Mat); 2 - S and submitted to pHcm; 3 - CL bleached with CP; 4 - CL stored in artificial saliva and submitted to pHcm; 5 - CL treated with placebo gel and submitted to pHcm; 6 - CL bleached with CP and submitted to pHcm. Enamel blocks with known initial KHN values were demineralized (groups 3 to 6) and submitted to 12 day pHcm (groups 2, 4, 5 and 6). After demineralization and treatments, KHN was determined and the specimens were examined using scanning electron microscopy (SEM). Data were analyzed statistically by ANOVA and Tukeys test at 5% significance level. The results showed that among CL groups (3 to 6) only the group 3 presented remineralization after treatments. S groups (1 and 2) showed higher KHN and presented less formation of porosities on enamel surface than CL groups after treatments. In conclusion, bleaching procedures on enamel with CL did not exacerbate the demineralization, but should be indicated with caution.

In Vitro Secondary Caries Inhibition by Adhesive Systems in Enamel Around Composite Restorations

This study compared the ability of adhesive systems to inhibit in vitro caries lesions in enamel under high cariogenic challenge. Bovine enamel blocks with cavity preparations were restored with AP-X resin composite (Kuraray Med) using four adhesives systems: Clearfil SE Bond (Kuraray Med); Clearfil Protect Bond (Kuraray Med); One-Up Bond F (Tokuyama) and Single Bond (3M ESPE). The specimens were submitted to an eight-day pH-cycling regimen. After cariogenic challenge, the enamel was evaluated to detect caries lesions using cross-sectional microhardness, polarized light microscopy and scanning electronic microscopy. Data from cross-sectional microhardness and polarized light microscopy evaluations were statistically analyzed by ANOVA and Tukeys test. The mineral % volume showed no statistical difference among adhesives (p > 0.05); however, polarized light microscopy analysis showed lower caries lesions with Clearfil Protect Bond (p < 0.05). The scanning electron microscopy images showed greater caries lesions and demineralization areas close to restorations for Clearfil SE Bond, One-Up Bond F and Single Bond compared to Clearfil Protect Bond. The pH-cycling regimen promoted subsurface enamel demineralization in all specimens treated. The polarized light microscopy and scanning electronic microscopy analyses showed that Clearfil Protect Bond seems to produce lower enamel demineralization around restorations; however, cross-sectional microhardness did not demonstrate differences among the adhesives.

Enamel and dentin bond strength, interfacial ultramorphology and fluoride ion release of self-etching adhesives during a pH-cycling regime.

PURPOSE This study evaluated the effects of pH cycling on fluoride release and bond strength of two self-etching adhesive systems to both enamel and dentin. The ultramorphology of the interfaces produced by the adhesive systems were also analyzed. MATERIALS AND METHODS The buccal surfaces of bovine incisors were flattened to expose enamel and dentin, which were bonded with either Clearfil Protect Bond (CPB) or One-Up Bond F Plus (OBP). The bonded samples were prepared for microtensile bond strength (μTBS) testing, fluoride ion release, and transmission electron microscopy. pH cycling comprised demineralization (8 h/day) and remineralization (16 h/day) cycles for 8 days. The μTBS data were analyzed by two-way ANOVA, while fluoride release was analyzed using the Friedman and Wilcoxon tests. RESULTS The adhesives presented similar bond strengths to enamel. However, the dentin bond strength of CPB was higher than that of OBP. pH cycling did not influence enamel or dentin μTBS. The amount of fluoride released from the bonded enamel and dentin was low and varied among the groups. The morphological evaluation showed that the thickness of the dentin hybrid layers was similar for both adhesives. CONCLUSION The pH-cycling regime did not affect enamel or dentin bond strengths. In enamel, both the self-etching adhesives tested presented similar bond strengths, but in dentin, Clearfil Protect Bond showed higher dentin bonding than One-Up Bond F Plus.

Influência da formação de película adquirida e aplicação tópica de flúor na microdureza do esmalte tratado com peróxido de hidrogênio 35

O objetivo deste estudo foi avaliar a influencia da formacao da pelicula adquirida (PEA) e da aplicacao topica de fluor (ATF) apos o tratamento com peroxido de hidrogenio a 35% na microdureza Knoop do esmalte. Foram obtidas 120 amostras de esmalte (4x4x4mm) a partir das superficies vestibulares de 60 incisivos bovinos. As amostras foram preparadas para a leitura de microdureza de superficie (inicial) e aleatoriamente divididas em quatro grupos (n=20): (1) Esmalte sem formacao de PEA e sem ATF pos-tratamento clareador (controle); (2) Esmalte sem formacao de PEA e com ATF pos-tratamento clareador; (3) Esmalte com formacao de PEA e sem ATF pos-tratamento clareador; (4) Esmalte com formacao de PEA e com ATF pos-tratamento clareador. Os dentes foram submetidos a 12 dias de ciclagem de pH, concomitante com o clareamento (Pola Office, SDI) que foi realizado no 1o, 6o e 12o dias de ciclagem. Apos a ciclagem de pH, foi realizada a leitura da microdureza superficial final e da microdureza longitudinal do esmalte tratado. Todos os grupos experimentais mostraram reducao da microdureza superficial do esmalte apos os tratamentos realizados. Os valores medios (iniciais e finais) foram semelhantes entre os grupos experimentais. Com relacao a microdureza longitudinal, somente na primeira profundidade (10 µm) observou-se reducao significativa da microdureza, com relacao as demais profundidades analisadas. Esses valores medios, em 10 µm, nao diferiram entre os grupos experimentais, assim como, as outras profundidades analisadas tambem nao diferiram entre os grupos. A microdureza do esmalte nao foi afetada pela formacao de PEA, nem pela ATF.