ObjectivesThe purpose of this study was to evaluate in situ the occurrence of corrosion in the soldering point areas between the wire, silver brazing and band in Haas expanders. Material and MethodsThirty-four 7-12-year-old patients who needed maxillary expansion with a Haas expander were randomly assigned to two groups of 17 individuals each, according to the oral hygiene protocol adopted during the orthodontic treatment: Group I (control), toothbrushing with a fluoride dentifrice and Group II (experimental), toothbrushing with the same dentifrice plus 0.12% chlorhexidine gluconate (Periogard®) mouthrinses twice a week. The appliances were removed after approximately 4 months. Fragments of the appliances containing a metallic band with a soldered wire were sectioned at random for examination by stereomicroscopy, scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Data were analyzed statistically by Fisher's test at 5% significance level. ResultsThe analysis by optical microscopy revealed areas with color change suggestive of corrosion in the soldering point areas joining the band and the wire in all specimens of both groups, with no statistically significant difference between the groups (p=1). The peaks of chemical elements (Ni, Fe, Cr, O, C and P) revealed by EDS were also similar in both groups. Conclusion: Color changes and peaks of chemical elements suggestive of corrosion were observed in the soldering point areas between the wire, silver brazing and band in both control and experimental groups, which indicate that the 0.12% chlorhexidine gluconate mouthrinses did not influence the occurrence of corrosion in situ.

Orthodontic appliances causes specific alterations in oral environment, including reduction of pH, increase of dental biofilm and elevation of salivary microbial levels, causing an increased risk for dental caries. This study evaluated, using microbial culture and scanning electron microscopy (SEM), the in situ contamination by mutans streptococci (MS) of different surfaces of Haas palatal expanders with and without use of chlorhexidine gluconate mouthrinses (CHX). Thirty-four patients were randomly assigned to two groups (n = 17/group), using placebo (Group I) and 0.12% CHX (Group II-Periogard ) mouthrinses twice a week. After 4 months, appliances were submitted to microbiological processing and after fragments were analyzed by SEM. Mann-Whitney U test (α = 5%) was used to assess differences between groups on the appliances' different surfaces and to compare the contamination on the free and nonfree surfaces of these components. There was no difference (p = 0.999) between groups regarding the number of MS colonies/biofilms on the nonfree surfaces, which showed intense contamination. However, free surfaces of Group II presented less contamination (p < 0.001) than those of Group I in all appliances' components. Results of the microbial culture were confirmed by SEM. Use of 0.12% CHX was effective in reducing the formation of MS colonies/biofilms on free surfaces of Haas expanders, in situ.

À pós-graduanda e amiga Raquel Assed Bezerra da Silva, grande incentivadora desta nova trajetória da minha vida. Exemplo de responsabilidade, dedicação e competência, tenho orgulho de ser sua amiga. Conte sempre comigo. Registro aqui meu carinho e gratidão a você. À pós-graduanda e amiga Regina Aparecida Segato Saiani, pelo início de uma grande amizade nas dificuldades compartilhadas. Pelas palavras de incentivo fundamentais nos momentos difíceis, com cumplicidade e afeto. Você é para mim um grande exemplo de responsabilidade e, acima de tudo, competência e profissionalismo. Muito obrigada. À querida pós-graduanda Maria Stella Gaspar Gomes Raffaini, pela parceria e ajuda incondicionais durante toda esta jornada. Minha admiração e gratidão, com muito carinho. Sua disposição, apoio e dedicação constantes mostram o grande ser humano que é.