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Objective To observe the porcelain treated with Nd∶YAG laser irradiation and hydrofluoric acid (HF), and to explore the influence of integrated treatment of Nd ∶ YAG laser irradiation and HF etching in the bond strength of brackets to porcelain.Methods 48 metal ceramic prostheses were randomly divided into untreated control group,HF group,grooved treatment group,0.75W laser group,1.05W laser group,1.45W laser group. All samples were bonded to the brackets.After temperature cycling test,the shear bond strength (SBS)and tensile bond strength (TBS)were measured.Results There were significant differences in SBS and TBS between various surface treatment groups and untreated control group (P < 0.01).The SBS and TBS of brackets bonded in HF group was significantly higher than those in 1.05W laser and 1.45W laser groups (P <0.05).The SBS and TBS in 1.05W laser and 1.45W laser groups were higher than those in HF group (P <0.05).The SBS and TBS in 1.05W laser group were higher than those in other groups (P < 0.05).SBS showed positive correlation with TBS (r =0.426,P =0.000).Conclusion The use of Nd∶YAG laser irradiation with the energy parameter of 1.05W and HF could increase the bonding with formation of composite resin,and the more SBS,the more TBS.
RESUMO
<p><b>OBJECTIVE</b>This study aims to analyze the biomechanical effects of four sutures that are related to maxillary growth during a maxillary protraction treatment cycle based on labiolingual appliance.</p><p><b>METHODS</b>A three-dimensional simulation of labiolingual appliance was performed based on a three-dimensional finite-element maxillofacial model combined with solid-modeled sutures.</p><p><b>RESULTS</b>The displacement and stress distributions were calculated. The labiolingual appliance was suitable for patients with underbites or deep overbites. Sutura frontomaxillaris and sutura zygomaticomaxillaris were vital to the forward displacement and counterclockwise rotation of the maxillary. The changes in sutura zygomaticotemporalis and sutura palatine were not significant.</p><p><b>CONCLUSION</b>The influences of the labiolingual appliance on the sutures during the treatment cycle of maxillary protraction can be effectively simulated by the three-dimensional finite-element maxillofacial model.</p>