Ototoxicity of hydrocarbons present in gasoline: a literature review / Ototoxicidade dos hidrocarbonetos presentes na gasolina: uma revisão de literatura

ABSTRACT Purpose: to investigate the toxicity effects of major hydrocarbons present in gasoline on the auditory system and the related mechanisms of action. Methods: a literature review between 2005 and 2015 was conducted using LILACS, MEDLINE and SciELO, by combining descriptors and their respective terms in Portuguese, English and Spanish. Results: studies performed in humans and animals with hearing impairment, confirmed by morphological tests in rats, the influence of factors such as dose, duration, species and type of stimulus in hearing loss, and ineffective protection of workers by the threshold levels of exposure in the mixture of the compounds, were chosen. Conclusion: toluene is regarded as an ototoxic compound that damages outer hair cells in the middle region of the cochlea, with evidence of interaction with noise. Ethylbenzene and xylenes can be considered potentially ototoxic based on the results of animal studies. No sufficient data were found on benzene to form a conclusion.

RESUMO Objetivo: realizar levantamento sobre a toxicidade ao sistema auditivo e os respectivos mecanismos de ação provocados pelos principais hidrocarbonetos presentes na gasolina. Métodos: revisão bibliográfica, entre os anos de 2005 a 2015, realizada nas bases LILACS, MEDLINE e SciELO, por meio da combinação de descritores e seus respectivos termos em português, inglês e espanhol. Resultados: foram identificados estudos em animais e humanos com danos auditivos confirmados por exames morfológicos em ratos; influência de fatores como dose, duração, espécie e tipo de estímulo na perda auditiva; e insuficiência de proteção dos trabalhadores pelos níveis limites de exposição na mistura dos compostos. Conclusão: de acordo com os resultados, tolueno é considerado ototóxico, lesando células ciliadas externas em região média da cóclea, com evidências de interação com ruído; etilbenzeno e xilenos podem ser considerados potencialmente ototóxicos, devido a estudos com animais; e sobre o benzeno não foram encontrados dados suficientes para conclusões.

In vivo assessment of periodontal structures and measurement of gingival sulcus with Optical Coherence Tomography: a pilot study.

There has been increasing interest on the development of clinically acceptable, more sensitive and specific methods for non-invasive diagnosis in Periodontics. In this pilot study, the performance of an Optical Coherence Tomography (OCT) system in imaging periodontal structures in humans was evaluated. Gingival sulcus depth measurements were obtained and compared with traditional probes. In total, 445 sites of 23 periodontally healthy individuals were measured by 3 instruments: North Carolina manual probe, Florida automated probe and OCT at 1325 nm. To obtain quantitative measurements from OCT images, the gingival refractive index was also determined. Discomfort/pain perception and the duration of examinations were compared among the instruments. The analysis of OCT images allowed the identification of relevant anatomic dental and periodontal regions. The average sulcus depth measured by OCT, 0.85 ± 0.27 mm and 0.87 ± 0.28 mm, was lower than the values obtained by manual and automated probing. Discomfort/pain were prevalent for traditional probes, which are invasive methods, than for the non-invasive OCT technique. OCT has the potential to be a reliable tool for in vivo periodontal tissues evaluation and for reproducible sulcus depth measurements in healthy sites. Further technological advances are required to reduce the procedure time and promote evaluation of posterior oral regions. Photonic assessment of periodontal tissue with OCT (top) in a clinical environment, showing tooth/gingiva features (bottom).

Effect of pH values of two bleaching gels on enamel microhardness.

This study evaluated the influence of bleaching gel pH and the effect of remineralizing gels after bleaching in different time intervals. Sixty bovine incisors were divided into 2 groups (n = 30). Group 1 was bleached with a 35% hydrogen peroxide (HP) acid gel and Group 2 was bleached with a 35% HP neutral gel. Each group was then divided into 3 subgroups (n = 10) according to the post-bleaching treatment used: storage in artificial saliva, application of a fluoride gel, or application of a gel consisting of fluoride, potassium nitrate, and nanostructured calcium phosphate. Specimens were stored in artificial saliva, and enamel microhardness was evaluated at 24 hours and 15 days postbleaching. Vickers microhardness data were analyzed by means of 2-way ANOVA, with repeated measurements and Bonferroni's post-hoc test. Twenty-four hours after bleaching, no significant differences were found between the bleaching gels. At 15 days postbleaching, Group 2 samples demonstrated a significant reduction in microhardness. No significant differences were found between the remineralizing gels, though all of the postbleaching treatments after the use of 35% neutral gel were able to re-establish baseline microhardness. It was concluded that neutral bleaching gel significantly reduced enamel microhardness 15 days after bleaching and that the use of remineralizing gels did not significantly enhance the microhardness of bleached enamel. However, in clinical situations, the acquired enamel pellicle protects tooth surfaces, and postbleaching, decalcified enamel would undergo recalcification. This study indicates that it is important to consider the bleaching agent's pH and composition when treating patients with reduced salivary secretion.

Impact of remineralizing agents on enamel microhardness recovery after in-office tooth bleaching therapies.

OBJECTIVE: It has been shown that bleaching with 35/38% hydrogen peroxides may alter both enamel morphology and mineral content. This study aimed to analyze the morphology and microhardness of enamel bleached with in-office hydrogen peroxides and exposed toremineralizing agents. MATERIALS AND METHODS: After recording initial enamel morphology and microhardness, 60 bovine incisors were bleached using either a calcium-containing 35% hydrogen peroxide (Whiteness HP Blue) or a calcium-free 35% hydrogen peroxide (Whitegold Office) (n = 30). Then, the teeth were subjected to one of three post-bleaching remineralizing treatments (n = 10): storage in artificial saliva only, application of a sodium fluoride gel or application of a nanohydroxyapatite-based agent (Nano-P). After 24 h and 14 days of post-bleaching treatments, the enamel morphology and microhardness were re-evaluated. The microhardness data were analyzed by means of two-way ANOVA with repeated measurements and Tukey tests (p < 0.05), while the enamel morphology was analyzed descriptively. RESULTS: Samples exposed to Nano-P presented statistically the highest microhardness 24 h after its application in comparison with other remineralizing agents. The microhardness recovery did not occur in any of the groups 14 days after treatment. The morphology of all samples 14 days after the application of all remineralizing agents presented a higher number of irregularities. CONCLUSION: Although some remineralizing products provided microhardness recovery and a positive effect on enamel morphology at 24 h post-bleaching, none of them were able to maintain microhardness and enamel morphology at 14 days post-bleaching.

Resina composta: estágio atual e indicações / Composite resin: present stage and indications

É frequente a busca dos pacientes pela melhoria da estética dentária cujas técnicas têm obtido grande progresso devido à proliferação de pesquisas em materiais que atendam essa necessidade. Com a evolução das técnicas adesivas a resina composta tem sido intensamente pesquisada em relação as suas indicações, quantidade de partículas, formato, composição e distribuição, no sentido de se encontrar resinas compostas com melhores propriedades físicas. Mesmo com a grande variedade de resinas compostas e o grande número de pesquisas, ainda não surgiu um material restaurador ideal, portanto é importante o conhecimento por parte dos clínicos do material a ser utilizado, com suas indicações corretas, para que sejam obtidos resultados clínicos com sucesso estético e funcional

It is common patients seek aesthetic dentistry, which technique have had a great progress due to the proliferation of researches on material to meet this need. With the development of the adhesive techniques, composite resin has been largely researched, concerning its indications, amount of particles, shape, compositions and distribution, in order to find dental composite resins presenting better physical properties. Even with the wide variety of composites and the large number of researches, it has not yet appeared an ideal restorative material, hence the importance of knowledge by the clinicians of the material used, with adequate indications, so that the clinical results succeed aesthetically and functionally