Effect of Metal Primers on Bond Strength of a Composite Resin to Nickel-Chrome Metal Alloy

Abstract This study evaluated the effects of three metal primers and one multi-mode adhesive system on the shear bond strength (SBS) of a flowable composite resin to nickel-chrome metal alloy (Ni-Cr). Ninety plates were cast from Ni-Cr and divided in nine groups (n=10). The surfaces were sandblasted with Al2O3 and primed with three adhesive primers: Alloy Primer (AP), Universal Primer (TP) and RelyX Ceramic Primer (CP), and a multi-mode adhesive (Scotchbond Universal, SU). The Adper Single Bond Plus (SB) and SU adhesives were also combined with adhesive primers. Control group did not have any surface treatment. The groups were: AP, AP+SB, AP+SU, TP+SB, TP+SU, CP+SB, CP+SU and SU. Composite cylinders were built on alloy surface. After 24 h, half the specimens were subjected to SBS and the other half to thermal cycling before testing. Data were analyzed by two-way ANOVA and Tukey’s test (a=0.05). Failure modes were assessed by SEM observation. Higher SBS were obtained with AP and TP combined with adhesives at 24 h and the lowest one for control group. Thermocycling reduced SBS for AP, CP+SU and SU. Combination between TP and SU resulted in the highest SBS after the thermocycling. TP groups showed all types of failures and high incidence of mixed failures. The use of AP and UP metal primers before application of SU and SB adhesive systems increased the SBS of composite to Ni-Cr. These combinations between metal primers and adhesives had the highest SBS after thermocycling.

Resumo Este estudo avaliou os efeitos de três primers para metais e um sistema adesivo multi-mode na resistência da união por cisalhamento (SBS) de um compósito resinoso de baixa viscosidade a uma liga niquel-cromo (Ni-Cr). Noventa placas Ni-Cr foram divididas em 9 grupos (n=10). As superfícies foram jateadas com Al2O3 e condicionadas com três primers adesivos: Alloy Primer (AP), Universal Primer (TP) e Rely X Ceramic Primer (CP) e um adesivo multi-mode (Scotchbond Universal, SU). Os adesivos Adper Single Bond Plus (SB) e SU foram combinados com os primers para metais. O grupo controle não recebeu nenhum tipo de tratamento superficial. Os grupos foram: AP, AP+SB, AP+SU, TP+SB, TP+SU, CP+SB, CP+SU e SU. Cilindros de resina foram construídos na superfície da liga. Após 24 h, metade dos espécimes foi submetido ao SBS, a outra metade foi termociclada previamente. Os dados foram analisados pelos testes ANOVA dois fatores e Tukey (a=0.05). Os tipos de fraturas foram determinados utilizando microscopia eletrônica de varredura (MEV). Os maiores valores de SBS foram obtidos com AP e TP combinados com adesivos após 24 h e o menor valor foi obtido no grupo controle. A ciclagem térmica reduziu a SBS para AP, CP+SU e SU. Combinação entre TP e SU resultou em altos valores de SBS após termociclagem. Os grupos TP apresentaram todos os modos de fratura e alta incidência de fraturas mistas. O uso dos primers AP e UP para metais antes da aplicação dos sistemas adesivos SU e SB aumentou a SBS entre o Ni-Cr e a resina composta. Essa combinação entre primers e adesivos mostrou os maiores valores de SBS após a termociclagem.

Socioeconomic, nutritional and behavioral factors associated with severe childhood caries in children aged 18-36 months

Objective:To relate the occurrence of severe childhood caries with nutritional, socioeconomic and behavioral factors among preschool children. Material and Methods:This cross-sectional study included 111 children aged 18-36 months who sought dental care in basic health units of São Luis, Brazil. The oral health status was measured by the DMFT index (number of decayed, missing and filled teeth), IPV/ISG. Socioeconomic, nutritional and behavioral data were collected through a questionnaire applied to parents. Caries Group was defined as DMFT ≥ 1. Data were analyzed using the Chi-square test and Fisher exact test. Poisson regression models and incidence rate ratio (IRR)were used for multivariate analysis, adopting significance level of 5% and confidence interval (CI) of 95%. Results:It was observed that 61 children (55%) were free from caries and 50 (45%) had the disease. In the Caries Group, 38 (76%) had white spot lesions, 70% had the habit of consuming sweets between meals (p=0.04) and the sucrose intake frequency was considered high (3x daily). After multivariate analysis, age (IRR=1.05, 95%CI=1.03 to 1.07, p <0.001) and consumption of sweets (IRR=1.46, 95%CI=1.11 to 1.92 p=0.006) were associated with increased incidence of caries. Conclusion:The findings of this study suggest that frequent exposure to sugars in the form of sweets between meals, lack of guidance of mothers on oral hygiene and increased age were determining factors for the occurrence of severe childhood caries