Effect of incorporation of copper nanoparticles at varying percentages into irreversible hydrocolloid impression material on its tear strength and flow. Materials and Methods: A total of 120 samples are fabricated and divided into 4 groups (1 control group and 3 experimental groups) consisting of 30 samples in each group. 30 samples are further divided into 2 subgroups each consisting of 15 samples to evaluate tear strength and flow. Sample preparation for tear strength: Impression material IMPRECEED (GC Corporation Tokyo, Japan) was mixed as recommended by the manufacturer and poured in to a customized mould with a dimensions of [8 X 1 X 0.5] cms. A glass slab is placed on the top of the mould and a standard weight of 1kg was applied on glass slab to ensure a uniform thickness of the specimen. After the material has set, the specimen was removed carefully from the mould. Similarly, samples were prepared for irreversible hydrocolloid impression material incorporated with copper nanoparticles of 0.25wt%, 0.5wt%, 1.0wt%. Testing of specimens for tear strength: Strain gauge is used to measure tear strength. Specimen is placed in between the jigs. Load is applied and gradually increased. The load at which the specimen tears was noted from the console of the strain gauge. Measurement of flowability: 0.5 ml of hydrocolloid irreversible impression material IMPRECEED (GC Corporation Tokyo, Japan) is injected onto a glass slab using a 2ml disposable syringe within 60 seconds of mixing as recommended by the manufacturer. Another glass slab was placed on top of the impression material and a standard weight of 1.5kg is placed on the outer surface of the upper glass slab. After the final set, the weight was removed and the perimeter of the impression disc was measured with the help of a matlab software called edge detector. The sample was scanned with the help of a scanner. The scanned impression discs are programmed in the mat software. This program detects the perimeter and diameter of the discs, thus the flowability is evaluated. Similarly, all the 15 samples of each group are tested for flow and recorded. Results: The comparison of mean tear strength between the Groups A1, B1, C1 and D1 was done using Mann-Witney U test. It was observed that the mean tear strength was higher in control group A1 (241±2.84). The mean tear strength was lower in test specimens of Group B1 (166.7±23.2) followed by Group C1 (94.7±20.6) and Group D1 (64.2±21.6) (p=0.000*). The mean comparison of flowabiltiy between the Groups A2, B2, C2 and D2 was done using kruskal-wallis test. It was observed that the mean flowabilty was significantly higher in Control Group A2 (3.71±0.02). The mean flowability was lower in samples of Group B2 (3.62±0.04) followed by Group C2 (3.52±0.05) and Group D2 (3.39±0.04) (p=0.000*). Conclusion: The results of the present study concluded that, among the Groups tested (A1, B1, C1, D1), the tear strength of irreversible hydrocolloid impression material decreased progressively in descending order with addition of copper nanoparticles at 0.25 wt%, 0.5 wt% and 1.0 wt% respectively. The test specimens of Group A1 (unmodified) showed the highest values of tear strength in comparison with Group B1, Group C1 and Group D1 (modified). Among the Groups tested (A2, B2, C2, D2), the flowability of irreversible hydrocolloid impression material decreased progressively in descending order with addition of copper nanoparticles at 0.25 wt%, 0.5 wt% and 1.0 wt% respectively. The test specimens of Group A2 (unmodified) showed the highest values in comparison with Group B2, Group C2 and Group D2 (modified).