Influence of different surface treatments on porcelain surface topography / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the influence of different surface treatments on porcelain surface topography.</p><p><b>METHODS</b>Metal ceramic prostheses in 6 groups were treated according to the different surface treatment methods, and the surface topography was observed through scanning electron microscope (SEM). Group A was the control one (untreated), group B was etched by 9.6% hydrofluoric acid(HF), group C was deglazed by grinding and then etched by 9.6% HF, group D was treated with Nd: YAG laser irradiation(0.75 W) and HF etching, group E was treated with Nd: YAG laser irradiation (1.05 W) and HF etching, and group F was treated with laser irradiation (1.45 W) and HF etching.</p><p><b>RESULTS</b>Surface topography was different in different groups. A lot of inerratic cracks with the shapes of rhombuses and grid, and crater with a shape of circle were observed on the ceramic surface after treatment with energy parameters of 1.05 W Nd: YAG laser irradiation and 9.6% HF etching (group E). Surface topography showed a lot of concaves on the inner wall of the cracks, and the concaves with diameter of 1-5 microm could be observed on the inner wall of the holes, which had a diameter of 20 microm under SEM.</p><p><b>CONCLUSION</b>The use of Nd: YAG laser irradiation with the energy parameters of 1.05 W and the HF with a concentration of 9.6% can evenly coarsen the porcelain surface, that is an effective surface treatment method.</p>

Three dimensional finite element analysis of tooth movement tendency in maxilla using mini-screw cooperated with upper accentuated-curve to close tooth space / 华西口腔医学杂志

<p><b>OBJECTIVE</b>In order to find out the cause of molar intrusion and how to avoid molar intrusion, we analyze the movement tendency of tooth by changing the angles of upper accentuated-curve and the height of free traction hook.</p><p><b>METHODS</b>Spiral CT scanning and Mimics 10.0 software were employed in this study to construct the three dimensional finite element model of maxillary teeth, periodontal ligaments and alveolar bone as well as the inch stainless steel upper accentuated-curve archwires with different angles (5 degrees, 10 degrees, 15 degrees, 20 degrees, 25 degrees) and the free traction hook with different height (2.1, 4.0, 5.5 mm). By exerting 1.5 N backward force to analysis the displacement trend of maxillary tooth.</p><p><b>RESULTS</b>Upper accentuated-curve archwires made the incisors labially tip, intruse, distally upright and mesilabially torsion; made the canines labially tip, prolong, mesial-tipped and mesi-labially torsion; made the second premolars and the first molars buccal tip, intruse, distal upright and mesi-labially torsion. With the angle of upper accentuated-curve archwires increased, all tooth movement tendency increased; while with the height of free traction hook increased, all tooth movement tendency decreased.</p><p><b>CONCLUSION</b>When the angle of upper accentuated-curve archwires increased, the extent of molar intrusion increased, but when the height of free traction hook increased, the degree of molar intrusion decreased. The degree of molar intrusion was minimum using 5 degrees upper accentuated-curve archwires cooperated with 5.5 mm free traction hook.</p>