Effect of different dentin cleaning agents on the bond strength of self-adhesive resin cement to dentin / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This study aims to evaluate the bond strength of a self-adhesive resin cement to dentin by ethylene diamine tetraacetic acid (EDTA) and NaClO.</p><p><b>METHODS</b>Twenty-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).</p><p><b>RESULTS</b>The 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.</p><p><b>CONCLUSION</b>1% NaClO can increase the bond strength of self-adhesive resin cement to dentin, but 3%EDTA has no effect.</p>

Assessment of occlusal vertical dimension using angles: a pilot study / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This 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.</p><p><b>METHODS</b>A 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.</p><p><b>RESULTS</b>The 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.</p><p><b>CONCLUSION</b>The CA can be used to assess and quantify the occlusal vertical dimension in clinical practice.</p>