Aim & Objectives:
To compare the impact strength and Porosity of denture base resins polymerized using short and long curing cycles by water bath and microwave techniques, and to evaluate which method is better (water bath or microwave polymerization technique).
A stainless steel die was prepared with dimensions 60 mm × 12 mm × 3 mm, as standardized by the American Standards for Testing and Materials (ASTM). 128 samples were made (64 cured by microwave energy and 64 cured by conventional water bath technique in which 32 each were acrylized using long curing cycle and short curing cycle). Each sample was to be scanned in three premarked areas for surface porosities using the Digital microscope (CS02 USB Powered , China). Portion of the sample being scanned was displayed on the computer and with the help of software area of each pore was measured. A digital caliper (Neiko 01407A) was used to locate the midpoint of sample. The impact strength was measured in Universal testing machine (Instron 3360). All data obtained were analyzed by unpaired T-test, Two way analysis of Variance (ANOVA) and One way analysis of Covariance (ANCOVA).
There is a significant difference between the long and short cycles of both the groups irrespective of materials being used for both impact strength and Porosity. When two groups were compared, there was significant increase in porosity for the microwave group for the similar cycles. For impact strength it was found that microwave group had the highest strength.
The result obtained showed that the microwave polymerization technique produced denture bases with highest impact strength, while water bath polymerization technique also produced equally good results. The conventional water bath technique produced the least Porosity while microwave technique showed equally good result. In all the techniques, the long curing cycle proved to be better in producing denture bases with higher impact strength and less Porosity as compared to short curing cycle. According to this both conventional water bath and microwave technique showed Porosity less than 11% and Impact strength almost similar for both the groups, hence both the methods can be used in fabrication of complete dentures.
Polymethacrylate, Microwave polymerization, Impact strength, Porosity, Water bath polymerization.