OBJECTIVEThis study aims to evaluate the bond strength of a self-adhesive resin cement to dentin by ethylene diamine tetraacetic acid (EDTA) and NaClO.

METHODSTwenty-seven freshly extracted non-carious human premolars were prepared to expose the buccal dentin and randomly divided into three groups: control group (A group), EDTA group (B group) and NaClO group (C group). All teeth were bonded to dentin using a self-adhesive resin cement after the teeth in the A group were processed with distilled water. The B and C group were processed with 3%EDTA and 1%NaClO, respectively. After 24 hours at 37 °C water, the shear bond strengths of the twenty-four specimens were measured. All statistical analysis was performed using SPSS 17.0 software package. Each fractured specimen was examined under dental microscope. Three new specimens were cut, and the morphologies of the cement-dentin interface were observed under scanning electron microscope (SEM).

RESULTSThe shear bond strength in the A group, B group and C group was (8.55±0.63), (8.47±0.56) and (12.97± 0.59) MPa, respectively. The difference between A group and B group was no statistically significant (P>0.05), whereas the difference between C group and B group (or A group) was statistically significant (P<0.05). SEM observation of the cement-dentin interface in the C group showed good adaptation, but resin tags were not observed. The other two groups showed poor bonding interface. Most of the fractured adhesive dentin surfaces exhibited cohesive failure in the A group and B group. All the fractured adhesive dentin surfaces exhibited cohesive failure in the C group.

CONCLUSION1% NaClO can increase the bond strength of self-adhesive resin cement to dentin, but 3%EDTA has no effect.

Adhesives ; Dental Bonding ; Dental Stress Analysis ; Dentin ; chemistry ; Dentin-Bonding Agents ; Detergents ; chemistry ; Humans ; Resin Cements

Objective: To understand the current situation of the lack of knowledge about sexual and reproductive health among female college students, and to provide a reference for conducting feasible and effective interventions to improve their reproductive health. Methods: Female college students from a higher vocational college in Yantai were randomly sampled and questionnaires were conducted before and after the sexual and reproductive health education, 2 153 baseline questionnaires were obtained before intervention. After intervention for half a year, 2 110 valid questionnaires were obtained. Results: After the intervention, female college students’ awareness of normal menstrual cycle, menstrual days, menstrual health knowledge, female ovulation time, ovulation and menstruation significantly improved(P<0.01). The proportion of female college students taking an open attitudes of towards to premarital sex increased, and the number of contraceptives was significantly increased during premarital sex, and the rate reported with the intention of unwanted pregnancies to help parents, friends, and teachers was increased significantly, and the rate of choosing abortion in the illegal clinic decreased significantly (P<0.05). After intervention, students were concerned about contraceptive knowledge, STD prevention, and human flow harm. The cognition was significantly improved(P<0.01). Conclusion Reproductive health education for female college students can have a good effect and significantly increase the awareness rate of related knowledge.

OBJECTIVEThis study aims to identify highly accurate quantitative methods for evaluating the occlusal vertical dimension by using cephalometric radiographs to analyze the craniofacial hard tissue landmarks in 30 cases with normal occlusions.

METHODSA total of 30 subjects with normal occlusions and aged between 20 and 30 years old were included in the study. Cephalometric radiographs were obtained and analyzed using the Winceph 8.0 measurement software. Landmark points were identified and measured.

RESULTSThe mean distribution difference of the center angle (CA) and lower angle (LA) of the face was not statistically significant (t = -1.490, P = 0.147). The CA and LA had a significantly linear correlation (r = 0.976, P = 0.000), and the regression equation was y = 0.298 + 0.997x.

CONCLUSIONThe CA can be used to assess and quantify the occlusal vertical dimension in clinical practice.

Adult ; Cephalometry ; Face ; Female ; Humans ; Male ; Pilot Projects ; Vertical Dimension ; Young Adult