An in vitro investigation of wear resistance and hardness of three kinds of new composite resins / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate wear resistance and hardness of three kinds of new composite resins.</p><p><b>METHODS</b>Three kinds of new composite resins, Solidex, Spectrum, Filtek Z350, were tested. Enamel as control group. A refited MG-200 wear machine was used in this study. Scanning electron microscope (SEM) was used to observe the friction surface of each tested material. Hardness of each tested material was determined by Vickers indentation technique. The data of wear and hardness were analyzed by Mann-Whitney test and 1-way ANOVA. The relationship between the hardness of the composites and the amount of wear of them was determined by a regression analysis method.</p><p><b>RESULTS</b>Filtek Z350 showed the lowest volumetric wear and highest Vickers hardness in the composites (P < 0.05). No significant differences in wear and hardness were observed between Solidex and Spectrum (P > 0.05). Significant relationships were observed between the hardness of the composites and the amount of wear of them (r = 0.968 6) (P < 0.05). Different wear characters of the friction surface of the tested materials were observed by SEM.</p><p><b>CONCLUSION</b>Nanofilled composite was superior to the hybrid composite in wear resistance and hardness.</p>

The influence of gilt to the retention of the complete metal crown / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To research the influence of gilt to the retention of the complete metal crown.</p><p><b>METHODS</b>Sixty Ni-Cr alloy complete metal crown were divided into three groups, control group (common Ni-Cr alloy complete metal crown), whole gold-plating group (whole gilding on the tissue surface of the inner Ni-Cr alloy complete metal crown), partial gold-plating group (gilding on the tissue surface of 1/3 cervical inner Ni-Cr alloy complete metal crown). The retention force of complete metal crown was measured by tensile force/pressure ergograph.</p><p><b>RESULTS</b>The retention force of control group, partial gold-plating group, whole gold-plating group were (657 +/- 151) N, (632 +/- 139) N, (569 +/- 103) N, respectively. There were significant differences between control group and whole gold-plating group, whole gold-plating group and partial gold-plating group (P < 0.05). There was no significant difference between control group and partial gold-plating group (P > 0.05).</p><p><b>CONCLUSION</b>The force of retention would decrease after gilding on the tissue surface of the inner Ni-Cr alloy complete metal crown, but have no influence to normal retention requirement of complete crown. Although the retention of partial gold-plating complete metal crown had somewhat decrease, it could be ignored.</p>

Clinical evaluation of two types of fixed partial denture impressions / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the clinic effects of alginate impression and agar/alginate combined impression.</p><p><b>METHODS</b>237 patients of fixed partial denture were collected and divided into group A and group B. Group A was taken impression by aglinate impression, including 81 patients (207 abutments). Group B was taken impression by agar/alginate combined impression, include 156 patients (392 abutments). The impressions were observed by megaloscope, and the number of abutment, the types and number of defect were recorded.</p><p><b>RESULTS</b>In the aglinate impressions, 57.0 percent of abutment had some defect. But in the agar/alginate combined impressions, 36.0 percent of abutment had some defect. There were significant difference between group A and group B in the abutment, air bubbles in cervical margin, unsharpness of the gingival sulcus and shoulders (P<0.05). There were no significant difference between group A and group B in the split and defect of the impressions on the cervical margin.</p><p><b>CONCLUSION</b>There were less defects in the agar/alginate combined impression than in the alginate impression.</p>