Chemical Composition and Microhardness of Human Enamel Treated with Fluoridated Whintening Agents. A Study in Situ

BACKGROUND: Dental whitening has been increasingly sought out to improve dental aesthetics, but may cause chemical and morphological changes in dental enamel surfaces. OBJECTIVE: Assess in situ the effects of high-concentration hydrogen peroxide with and without fluoride on human dental enamel using the ion chromatography test (IC) and the Knoop hardness test (KHN). MATERIAL AND METHODS: Nineteen enamel specimens were prepared using third human molars. These specimens were fixed on molars of volunteers and were divided into groups: OP38-Opalescence Boost PF38%, PO37-Pola Office 37.5% and CO-Control group. For chemical analysis (n= 3), the dentin layer was removed, keeping only the enamel, which was subjected to acidic digestion by microwave radiation. It was necessary to perform sample dilutions for the elements fluorine (F), calcium (Ca) and phosphorus (P) for quantification using the IC test. The KHN (n= 5) was performed before and after the treatments. Five indentations were made, separated by 100 µm, for each specimen using a load of 25 gf for 5 seconds in the microdurometer. The data were analyzed using ANOVA with a 5% significance level. RESULTS: The OP38 group had the largest concentrations of F, Ca and P ions. The PO37 group showed the lowest concentrations of F and Ca ions. The average KHN was not significantly different between the OP38 and PO37 groups. CONCLUSION: Enamel whitened with hydrogen peroxide containing fluoride had greater concentrations of F, Ca and P ions. The presence of fluoride in the whitening agent did not influence the enamel microhardness

Study of Euglenophyta in the Jacuí Delta State Park, Rio Grande do Sul, Brazil. 1. Euglena Ehr., Lepocinclis Perty Estudo de Euglenophyta no Parque Estadual Delta do Jacuí, Rio Grande do Sul, Brasil, 1. Euglena Ehr., Lepocinclis Perty

This paper is the result of the study of pigmented Euglenaceae performed within the area of the Jacuí Delta State Park, located between parallels 29º56' and 30º03'S and meridians 51º12'and 51º18'W, with qualitative samplings at 25 stations, distributed over 8 islands, 8 "sacos" (i.e. small bays), 4 river mouths, 2 stream mouths and 3 channels in December/1993 and January/1994, and from February/1998 to December/1999. One hundred and fifty taxa of the Euglenophyceae were identified in the area. Currently 23 specific and infraspecific taxa of genus Euglena and 12 taxa of Lepocinclis are presented. E. acus Ehr. var. acus, and L. salina Fritsch var. salina were the taxa best represented in the region since they occured in over 40% of the samples studied. E. bonettoi (Tell & Zaloc.) Couté & Thérez., L. playfairiana Defl. var. striata Conf. and L. caudata (Cunha) Conr. were recorded exclusively for South America; sixteen taxa identified have a cosmopolitan distribution. Ranges of some abiotic variables of the environments in which each taxon occurred in the study area are mentioned.<br>Este trabalho é o resultado do estudo de Euglenaceae pigmentadas realizado na área do Parque Estadual Delta do Jacuí, localizado entre paralelos 29º56' e 30º03'S e os meridianos 51º12'e 51º18'W, com amostragens qualitativas em 25 estações de coletas distribuídas em 8 ilhas, 8 sacos, 6 desembocaduras de rios e 3 canais, em dezembro/1993 e janeiro/1994 e de fevereiro/1998 a dezembro/1999. Foram identificados na área cerca de 150 táxons de Euglenophyceae. São apresentados, neste trabalho, 23 táxons específicos e infra-específicos do gênero Euglena e 12 táxons de Lepocinclis. E. acus Ehr. var. acus e L. salina Fritsch var. salina foram os táxons melhor representados na área por ocorrerem em mais de 40% dos biótopos estudados. E. bonettoi (Tell & Zaloc.) Couté & Thérez., L. playfairiana Defl. var. striata Conf. e L. caudata (Cunha) Conr. foram registrados exclusivamente para o América do Sul e 16 táxons identificados possuem distribuição cosmopolita. São fornecidas as amplitudes de algumas variáveis abióticas dos ambientes em que cada táxon ocorreu na área de estudo