Objective To analyze the stress state of magnetic attachment in mandibular complete overdenture supported by nature roots and implant, and to provide neference for designing of clinical prosthodentics. Methods Three-dimensional finite models (model,Ⅱ,Ⅲ)of three groups of mandibular overdentures depending on the different location of the implant and natural tooth root, placing three pairs of magnetic attachment, were constructed by application of CT scanning,computer photo processing system,and Solidworks finite element model building software.The natural teeth and implant neck bone stress of the models in three groups under different stress were calculated and compared.Results The stress of the bone around the implant in the area of molar teeth in model with both sides of the implants under oblique load (Model Ⅱ)was significantly increased compared with the model with one side of the implant (Model Ⅲ). The supporting bone stress of oblique load was increased compared with the vertical load;among them under the oblique load at one side’ s molar teeth, the stress of the bone around the implant in the area of molar teeth in modelⅠ,modelⅡ and model Ⅲ was increased about 30%, 43%,and 55%.Conclusion When there only one nature teeth remain,two implants should be at least added, one in the area of opposite cuspid, and the other in the area of molar teeth of the same side. The magnetic attachment is better than other kinds of attachment in preventing the damage of abutment when it suffers inclined load.

OBJECTIVE:To evaluate the rationality and validity of chemical medicine tablet production equipment cleaning pro-cedure. METHODS:Among several chemical medicines prepared by similar production technology as Metoprolol succinate sus-tained-release tablets,Captopril tablets,Isosorbide mononitrate tablet and Metformin hydrochloride tablet,Metoprolol succinate sus-tained-release tablets had strongest toxicity and were included in validation test. The production equipment was cleaned and disinfect-ed according to cleaning procedure. The point which was most difficult to clean could be wiped and sampled by using the cotton swab method. The detection limit and the limit of quantitation of the residue limits were verified as well as the recovery rate of wip-ing,in order to evaluate whether the results meet the requirements. RESULTS:The cotton swab method is adopted to wipe sample and detect the point which is most difficult to clean. The visible foreign body has not been found in each sampling point. The amount of residual drug is <29.75 μg/cotton bud,and microbial limits are <50 CFU/cotton bud,indicating test items are in line with the standard. CONCLUSIONS:The cleaning method can effectively clean the production equipment,and can effectively pre-vent product contamination and cross contamination to ensure the quality,efficacy and safety of the next batch of products.