Comparative evaluation of bond strength of resin cements with and without 10-methacryloyloxydecyl dihydrogen phosphate (mdp) to zirconia and effect of thermocycling on bond strength - An in vitro study.

Background: To compare bond strength of resin cements with and without 10-Methacryloyloxydecyl Dihydrogen Phosphate (MDP) to zirconia and evaluate effect of thermocycling on bond strength. Material and Methods: Standardised test specimens were fabricated as per ADA specification 131. Each Zirconia specimen was mounted in autopolymerzing acrylic resin material. The specimens were divided into 2 groups: Group 1 - specimens bonded with resin cement containing 10-MDP and Group II - specimens bonded with resin cement without 10-MDP. Forty samples of resin cement cylinders were prepared with dimensions of 6mm height and 4mm diameter in line with ADA specification 27 were cured onto the zirconia surface of 10mm x10mm x5mm using customised moulds. Specimens from each cement group were further divided into 2 subgroups: Subgroup A - Specimens that were not thermocycled and Subgroup B - Specimens that were thermocycled. Specimens were then subjected to tensile bond testing by using a Universal testing machine, the data were analysed using independent sample t test for bond strength and paired t test for effect of thermocycling. Statistical analysis used: Data was subjected to normalcy test (Shapiro-wilk test). Data showed normal distribution. Hence parametric test paired t test were applied. Results: Paired t test revealed that the thermocycling affected the bond strength to zirconia. The highest bond strength was achieved for the resin cement with 10-MDP before thermocycling, whereas the lowest bond strength values were recorded for resin cement without 10-MDP after thermocycling. Conclusions: Resin cement with 10-MDP showed superior bond strength to Zirconia than resin cement without 10-MDP. Adhesive failure was predominant at Zirconia and resin cement interface. Thermocycling had a significant effect on the bond strength of resin cements to zirconia, showing decreased bond strength. Key words:10-MDP, Tensile Strength, Zirconia.

Economic methods used in fabrication of tissue microarray: A pilot study.

BACKGROUND AND OBJECTIVE: Tissue microarray (TMA) is a method of harvesting small disks of tissue from a range of standard paraffin tissue blocks and placing them in an array on a recipient paraffin block such that hundreds of cases can be analyzed simultaneously by using only a few microliters of antibody in immunohistochemistry as a single experiment. The TMA construction done with the help of automated tissue arrayer or commercially available rubber molds are expensive. This study involved the fabrication of TMA using rubber-based additional silicone mold constructed in the department and comparison of this method with two other methods of fabricating TMA. MATERIALS AND METHODS: The TMA mold was fabricated using silicone material in the department. The recipient blocks were prepared. The tissue core prepared from donor blocks were inserted into the recipient blocks. The sections taken from this were compared with the TMA using double-sided adhesive tape technique and TMA by punching out holes in prefabricated dummy paraffin recipient block for insertion of tissue core. RESULTS: The TMA using a mold made of silicone showed more advantages than other two methods. CONCLUSION: Fabricating TMA mold using silicone in the department is inexpensive and yet efficient.