Influence of blood contamination on bond strength of a self-etching system.

OBJECTIVES: To detect the influence of blood contamination (BC) on the bond strength (BS) of a self-etching bonding system (SES) to enamel and dentine. METHODS: 25 human molars were longitudinally sectioned on the mesio-distal axis in order to obtain 50 specimens, which were embedded in acrylic resin. At first, the specimens were ground to expose a flat surface of enamel, and a bond strength test was performed. Afterwards, the samples were ground again in order to obtain a flat surface of dentine. Ten groups (total: n=100) were assigned according to substrate (enamel and dentine), step in the bonding sequence when contamination occurred (before the acidic primer and after the bonding resin), and contamination treatment (dry or rinse and dry procedure). Fresh human blood was introduced either before or after SES application (Clearfil SE Bond) and treated with air drying, or by rinsing and drying following application. Composite resin (Filtek Z-250,3M ESPE) was applied as inverted, truncated cured cones that were debonded in tension. RESULTS: The mean tensile BS values (MPa) for enamel/dentine were 19.4/23.0 and 17.1/10.0 for rinse-and-dry treatment (contamination before and after SES, respectively); while the measurements for the dry treatment, 16.2/23.3 and 0.0/0.0 contamination before and after SES, respectively. CONCLUSIONS: It was determined that blood contamination impaired adhesion to enamel and dentine when it occurred after bond light curing. Among the tested contamination treatments, the rinse-and-dry treatment produced the highest bond strength with BC after SES application, but it was not sufficient to recover the BS in the contamination-free group.

Longitudinal evaluation of the effect of saliva contamination during the bonding protocol with a self-etch adhesive system

Aim: To evaluate the influence of saliva contamination on the short- and long-term bond strength of a self-etch adhesive system. Methods: One hundred and twelve non-carious human molars were randomly divided according to: substrate (enamel/dentin); presence of saliva [none (control- C), before primer (BP), after primer (AP) and after bonding agent (AB)]; treatment of the contamination [none (1), rinsing + drying (2), drying (3) and primer re-application (4)] and specimen storage (24 h or 6 months). A self-etch adhesive system was applied to the dental surfaces followed by incremental insertions of composite resin. After storage in water at 37oC, the specimens were perpendicularly cut into beams for microtensile bond strength testing. Data in MPa were compared by A NOVA followed by Tukey’s test (p< 0.05). Micrographs were obtained by low vacuum scanning electron microscopy. Results: Control groups (G1 and G8) presented higher bond strength than all other groups. The factors presence of saliva, treatments of the contaminant and specimen storage showed no statistically significant results for the two dental substrates. Contaminants could be detected by LV-SEM. Six-month storage did not affect bond strength. Conclusions: The presence of saliva during the application of the self-etch system was deleterious to the bond to enamel and dentin, irrespective of the operative step in which the contamination occurred.

Effect of saliva contamination on the bond strength of an etch-and-rinse adhesive system to dentin / Efeito da contaminação salivar na resistência de união de um adesivo etch-and-rinse em dentina

Purpose: The aim of this study was to investigate the effect of saliva contamination on bond strength of an etch-and-rinse system to dentin. Methods: Fifty bovine incisors were embedded in acrylic resin and divided into 5 groups: G1 (control) - application of the adhesive system (Adper Single Bond 2 - 3M-ESPE); G2 - saliva contamination after acid etching of dentin, rinsing and drying; G3 - saliva contamination after acid etching of dentin and drying; G4 - saliva contamination after adhesive application, rinsing and drying; G5 - saliva contamination after adhesive application and drying. Contamination was performed by using 4 µL of simulated human saliva for 20 s. The adhesive system was applied according to the manufacturer's instructions; a composite resin was built as an inverted cone and was tested after 24 h at a cross-head speed of 0.5 mm/min. Results: When saliva contamination occurred after the adhesive photo-polymerization, bond strength was significantly reduced. The adhesive strength (MPa) mean values were: G1 = 18.1(±4.7) a; G2 = 20.5(±5.7) a; G3 = 17.3(±3.4) a; G4 = 12.6(±4.0) b; G5 = 9.8(±2.1) b (means followed by distinct letters are statistically different, P < 0.05). Conclusion: Saliva contamination negatively influenced bond strength of an etch-and-rinse adhesive, especially after the final polymerization of the adhesive system; in this condition, treatments were not efficient to recover adhesion.

Objetivo: Investigar o efeito da contaminação salivar na resistência de união de um adesivo condicione-e-lave em dentina. Metodologia: Cinquenta incisivos bovinos foram divididos em 5 grupos: G1 = (controle) aplicação do sistema adesivo (Adper Single Bond 2 - 3M-ESPE); G2 = contaminação com saliva após condicionamento ácido da dentina + lavagem e secagem; G3 = contaminação após o condicionamento ácido da dentina + secagem; G4 = contaminação com saliva após a aplicação do adesivo + lavagem e secagem; G5 = contaminação com saliva após a aplicação do adesivo + secagem. A contaminação foi realizada com 4 µL de saliva humana estimulada por 20 s. O sistema adesivo foi usado de acordo com as instruções do fabricante. A resina composta foi aplicada na forma de cone invertido, com o teste de tração realizado após24 h a 0,5 mm/min de velocidade. Resultados: As médias de resistência de união (em MPa): G1 = 18,1(±4,7) a; G2 = 20,5(±5,7) a; G3 = 17,3(±3,4) a; G4 = 12,6(±4,0) b; G5 = 9,8(±2,1) b, demonstrando que a resistência de união foi reduzida significativamente quando a contaminação salivar ocorreu após a fotopolimerização do adesivo. Conclusão: A contaminação influenciou negativamente a resistência de união do adesivo somente após a sua polimerização; nesta condição os tratamentos realizados não foram eficientes para recuperar a adesão.

[Genotypying of clinical isolates of Helicobacter pylori by cagA, vacA and babA2 virulence associated genes. First detection of a babA2 positive strain in Chilean patients]. / Genotipificación de aislados clínicos de Helicobacter pylori en base a genes asociados a virulencia cagA, vacA y babA2. Primer aislamiento de una cepa babA2 positiva en pacientes chilenos.

BACKGROUND: Helicobacter pylori-associated gastroduodenal diseases depends on host characteristics, environmental conditions and bacterial virulence factors, such as cagA, vacA y babA2 gene products. Moreover, peptic ulcer disease has been related with cagA+, vacAs1m1 strains, while metaplasia and gastric cancer has been associated to cagA+, vacAs1 and babA2+ H pylori strains. Gene babA2 has not yet been described in clinical isolates from Chilean patients. AIM: To investigate the presence of cagA, vacA (s and m) and babA2 genes in clinical isolates of H pylori from Chilean patients. MATERIAL AND METHODS: Sixty six isolates from 41 patients were genotyped by PCR, using primers for s1a, s1b, s2, m1, m2, cagA and babA2 genes as previously described. RESULTS: cagA gene was detected in 16 isolates (24.2%) while vacAs1a, vacAs1b, vacAs2, vacAm1 and vacAm2 were detected in 28 (42.4%), 14 (21.2%), 17 (25.8%), 21 (31.8%) and 29 isolates (43.9%), respectively. One isolate (1.5%) was babA2 positive, being the first isolate with this genotype described in Chile. Besides the babA2+ genotype this clinical isolate also presented cagA+ and vacAs1a which has been related with metaplasia or gastric cancer. Five isolates showed an ulcerogenic profile cagA+, vacAs1m1. CONCLUSIONS: The results presented indicate the prevalence of vacAs1m1 genotype among the clinical isolates analyzed, and a low frequency of babA2 genotype.

Increased in-vitro and in-vivo biological activity of lipopolysaccharide extracted from clinical low virulence vacA genotype Helicobacter pylori strains.

Helicobacter pylori infection in man is associated with chronic gastritis and peptic ulcer disease. The virulence factors of the species are still under investigation. Among these, the lipopolysaccharide (LPS) is a potential pathogenic factor of the micro-organism, whose biological activity can be estimated by immunological parameters. The aim of this study was to determine the ability of pure LPS extracted from clinical isolates of H. pylori to induce mitogenicity, secretion of tumour necrosis factor-alpha (TNF-alpha), and spleen growth in a murine model. Rough and smooth LPS from Salmonella typhimurium were used as controls. The results showed that, like the control LPS, all extracts of LPS induced mitogenic activity, stimulated synthesis of TNF-alpha and induced spleen growth, although the effects produced by the majority of the H. pylori LPS samples analysed were less intensive than those produced by the S. typhimurium LPS. The immunological parameters analysed allowed the detection of two types of H. pylori LPS: one of low biological activity and one of high biological activity. The most active LPS was extracted from strains isolated from patients with increased mucous damage associated with epithelial regeneration. Surprisingly, these strains were cagA negative and belonged to a low virulence genotype according to vacA gene (slbm2 and s2m2). The results suggest the need to re-evaluate the role of the LPSas a virulence factor for some strains of H. pylori.