Background:Giving a time gap and distance during curing can decrease the polymerization shrinkage.Aim:To evaluate the effect of time gap and distance between the curing tip and restoration on the polymerization shrinkage, degree of monomer conversion (DOC), and microhardness of a nanohybrid composite.Materials and Methods:A total of 50 standardized cylindrical specimens (Z350, 3M ESPE) were fabricated using a brass mould. The curing was done in contact with the sample surface for 20 seconds in the control group. In the four experimental groups, curing was initiated at 1-cm distance, followed by variation in the time gap and the curing cycle. The polymerization shrinkage, DOC, microhardness was calculated.Statistical Analysis:One-way analysis of variance (ANOVA) and post hoc-Dunnett test were used to analyze the data.Results:Curing at 1-cm distance for 10 seconds with a gap of 10 seconds and finishing the curing cycle with 20 seconds at 0 cm proved to be an appropriate technique to reduce the polymerization shrinkage without significantly affecting the DOC and microhardness.Conclusion:A simple innovative modification of varying the distance of curing and a time gap in the curing cycle can decrease the polymerization shrinkage without affecting the DOC and microhardness.
The ultimate purpose of the project is to manufacture a composite shaft using a lathe machine (conventional method). For this process, we have designed a special lathe attachment over which our fiber will be worn. We use an E-glass fiber and the solution is an epoxy resin mixed with hardener.Initially, the fiber is taken to the required amount and weighed. The equitant amount of epoxy resin is weighed. Then 10% of the weight of hardener to epoxy resin is mixed. The lathe attachment consists of a resin bath in which the resin is poured. The fiber is made to dip into the resin bath so that the fiber is completely covered with resin. On the other end of the attachment, the fiber with resin is taken out and rolled over the mandrel ( stainless steel rod of required dimension ).The mandrel is initially wound with butter paper and coated with wax ( For easy removal). As the fiber rolled over the mandrel with engaging the tool post with the lead screw. The required gear attachment for the lead screw speed is set. The Lathe is rotated at the least speed. The required number of windings on the mandrel is given by moving it back and forth. Them the mandrel is removed from the chuck and made to dry. After this process, the mandrel is removed by taking out the butter paper. We get a hollow shaft that is made of compound material i.e.fiber and epoxy resin. The product is of improved strength and is used for the replacement of propeller shafts. This is a conventional way of fabricating a composite shaft with the help of a lathe machine. The design of part of it is the special lathe attachment.
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