**3. Results**

Mean CFU comparison for *E. coli* with the control for each disinfecting regime and growth time is presented in Table 1. From the results, it was found that all the specimens incubated at 24, 36, 48 and 96 h and exposed to MW-DW-DC and MW-DW disinfection for 1, 2 and 3 min demonstrated significant difference in mean CFU of *E. coli* compared to the control without disinfection. However, for the MW-DW-DC group, complete disinfection was achieved at 2 min of disinfection at any growth time (*p*-value < 0.05). Conversely, for MW-DW disinfection, CFU was significantly zero at 3 min when compared with control at any growth time (*p*-value ≤ 0.05). For DC-DW specimens, CFU levels were approximately zero at five minutes when compared with the control at different growth durations (*p*-value ≤ 0.05) (Table 1).

Mean CFU comparison for *S. aureus* among the control for each disinfecting regime and growth times is presented in Table 2. For MW-DW-DC, CFU were significantly zero at 2 min of disinfection when compared with control at any growth time (*p*-value ≤ 0.05). For MW-DW specimens, CFU were significantly zero at 3 min of disinfection when compared with control at each growth time (*p*-value ≤ 0.05). For DC-DW disinfection, CFU were significantly zero at five minutes when compared with control at each growth time (*p*-value ≤ 0.05) (Table 2).

Mean CFU comparison for *S. mutans* with the control for each disinfecting regime and growth time is presented in Table 3. For MW-DW-DC, CFU were significantly zero at 2 min when compared with control (*p*-value ≤ 0.05). For MW-DW disinfection, CFU were significantly zero at three mins when compared it with control at each growth time (*p*-value ≤ 0.05). For DC-DW, CFU were significantly zero at 5 min when compared with control at each growth time (*p*-value ≤ 0.05) (Table 3).


**Table 1.** Presenting Mean CFU difference among the test and control (non-disinfected) samples for *E. coli*.

\* Significant at 5% using Mann–Whitney Test; MW: Microwave; DW: Distilled Water; MD: Mean Difference.

**Table 2.** Presenting Mean CFU difference among the test and control (non-disinfected) samples for *S. aureus*.


\* Significant at 5% using Mann–Whitney Test; MW: Microwave; DW: Distil Water; Tab: Tablet; MD: Mean Difference.


**Table 3.** Presenting Mean CFU difference among the test and control (non-disinfected) samples for *S. mutans*.

\* Significant at 5% using Mann–Whitney Test; MW: Microwave; DW: Distil Water; Tab: Tablet; MD: Mean Difference.

SEM analysis of the samples showed positive consortia-harboring cocci and bacilli (Figure 5). Using SEM, live cells of *E. coli* (rods), *S. aureus* and *S. mutans* (cocci) attached to the PMMA specimens were observed. After the disinfection procedure, dead cells were observed attached to the PMMA surface in the form of a small, agglomerated, mass of irregular-shaped cells (Figure 5).

**Figure 5.** *Cont.*

**Figure 5.** (**A**) Micrograph of biofilm positive consortia harboring cocci and bacilli. (**B**) Observe the attachment of mixture of live cells *E. coli* (rods) *S. aureus* and *S. mutans* (Cocci) on PMMA prior to disinfection. (**C**) Dead cells attached to the surface of acrylic slide, disinfected by exposure to MW at 450 W for 1 min (24 h). (**D**) Dead cells attached to the PMMA surface, disinfected by exposure to MW at 450 W for 1 min (48 h). (**E**) Dead cells on PMMA surface disinfected by MW with DC for 2 min (36 h). (**F**) PMMA surface disinfected with DW with DC for 5 min (24 h).
