Bond strength of self-adhesive resin cements to tooth structure

Objectives

The aim of this study was to evaluate the strength of the bond between newly introduced self-adhesive resin cements and tooth structures (i.e., enamel and dentin).

Methods

Three self-adhesive cements (SmartCem2, RelyX Unicem, seT SDI) were tested. Cylindrical-shaped cement specimens (diameter, 3 mm; height, 3 mm) were bonded to enamel and dentin. Test specimens were incubated at 37 °C for 24 h. The shear bond strength (SBS) was tested in a Zwick Roll testing machine. Results were analyzed by one-way ANOVA and t-test. Statistically significant differences were defined at the α = 0.05 level. Bond failures were categorized as adhesive, cohesive, or mixed.

Results

The SBS values ranged from 3.76 to 6.81 MPa for cements bonded to enamel and from 4.48 to 5.94 MPa for cements bonded to dentin (p > 0.05 between surfaces). There were no statistically significant differences between the SBS values to enamel versus dentin for any given cement type. All cements exhibited adhesive failure at the resin/tooth interface.

Conclusions

Regardless of their clinical simplicity, the self-adhesive resin cements examined in this study exhibit limited bond performance to tooth structures; therefore, these cements must be used with caution.     

原花青素联合乙醇湿粘结技术对乳牙牙本质剪切粘结强度的影响

目的：观察原花青素（PA）联合乙醇湿粘结技术对树脂乳牙牙本质剪切粘结强度的影响。方法：选取乳磨牙35颗,沿近远中向劈开,制成70个样本。将实验牙随机分为5组,分别为PA＋乙醇溶液预处理60 s和120 s组;乙醇单独预处理60 s和120 s组;对照组的牙本质树脂粘结试件。电子万能试验机测定37℃水浴保存24 h和30 d的剪切粘结强度;扫描电镜观察断裂面形态。结果：PA＋乙醇预处理组剪切粘结强度值明显大于乙醇单独预处理组和对照组（P＜0．05）,FESEM观察结果显示PA＋乙醇预处理组断裂主要发生在混合层顶部。结论：原花青素和乙醇湿粘结技术联合使用可以提高树脂乳牙牙本质间的剪切粘结强度。     

一种新型通用型牙本质粘结剂对牙本质粘结强度的体外评价

目的:评价一种新型通用型牙本质粘结剂(All Bond Universal,ABU)对牙本质的粘结强度,为临床选择合适的粘结剂提供参考依据。方法:选取人体12颗无龋坏磨牙,磨除牙釉质暴露牙本质面,分别用酸蚀-冲洗法和一步自酸蚀法使用All Bond Universal粘结剂,在其上堆砌树脂,并与酸蚀-冲洗粘结剂Prime&Bond NT(PBN)和一步法自酸蚀粘结剂G Bond(GB)进行对照。试样于37℃去离子水储存24 h后,每颗牙齿垂直于粘结面制备出0.81 mm2的树脂/牙本质试件,进行牙本质粘结微拉伸强度(μTBS)测试。结果:通用型牙本质粘结剂All Bond Universal在两种粘结方法下,其粘结力均高于对照组;就All Bond Universal本身而言,酸蚀-冲洗技术可以提高其粘结强度。结论:这种新型牙本质粘结剂具有较高的粘结强度,并且酸蚀-冲洗技术能提高其粘结力。     

Phenotypic and metabolic aspects of prostatic epithelial cells in aged gerbils after antisteroidal therapy: Turnover in the state of chromatin condensation and androgen-independent cell replacement

The gerbil is a rodent considered a good model for studies of prostatic morphophysiology under different experimental conditions. Studies involving castration and steroidal blockers of aged gerbils showed that the glandular epithelium persists after long-term therapy, preventing the organ atrophy. Thus, the objective of this study was to evaluate the phenotypic characteristics and behavior of prostatic epithelial cells that remained after different periods of hormone ablation in aged gerbils. The identification of elements that influenced the survival of this cell type was performed by morphometric, nuclear phenotypes, ultrastructural and immune histochemical analysis. The most significant responses to treatment, by analyzing morphometric features, were observed during the first three time points (day 1, day 3, and day 7), after which there appeared to be an adjustment of the gland to the hormone ablation. All treatments led to changes in the state of chromatin condensation, DNA methylation pattern and phenotypic changes indicated cell senescence. Additionally, an increase in the basal cells seemed to guarantee self-renewal properties to the epithelium. These data indicate that changes occur at many levels, including gene expression and nuclear architecture in the epithelial cells, when aging and steroidal blockade are associated. These aspects are important when considering castration-resistant prostate cancer, a malignant tumor posing difficult therapeutic intervention.