Experimental procedure 1.
Figure 3 shows the mean amount (in micrograms) of dye released by the teeth under different conditions after 1 h and 48 h. Although dye release was noted in three groups, i.e. propylene glycol without smear layer (PGNS), propylene glycol with smear layer (PGS) and distilled water without smear layer (DWNS) during the first hour, the greatest amount of release was noted in the specimens where safranin O in propylene glycol was applied in the absence of smear layers. The presence of smear layer affected dye diffusion through the tubules greatly during the first hour, when distilled water was used as the vehicle. Statistical analysis using anova revealed that there are significant differences in the amount of dye released after a 48-hour period amongst the four conditions ( P < 0.0001).
Experimental procedure 2.
Figure 4 shows the distribution of the time taken for dye to exit the apical foramen of the specimens. More than half of the specimens that were treated with safranin O in propylene glycol allowed some dye to be released in less than 1 min. In contrast, 53% of the specimens treated with safranin in distilled water showed no dye leakage through the apical foramen in a 24-hour period. The overall median time for some dye to be released was 0.60 min for the propylene glycol group ( n = 28) and 2.19 min for the distilled water group ( n = 14).
Propylene glycol allowed for a greater surface area to be penetrated with dye as compared with distilled water ( P < 0.0001) (Figs 2,5a). The second group of specimens that were not covered with inlay wax revealed similar statistically significant findings (Fig. 5b). In addition, it was observed that propylene glycol actually diffused through cementum in eight of 12 specimens. This was not observed in any of the samples treated with safranin O in distilled water.
Figure 3. Mean amount of dye released through open dentinal tubules within 1 h and 48-hour periods under different conditions. Significant difference exists amongst the four conditions (P < 0.0001). (PGNS - propylene glycol without smear layer; PGS - propylene glycol with smear layer; DWNS - distilled water without smear layer; DWS - distilled water with smear layer).
Figure 4. Time of dye exit from the apical foramen.
Figure 5. Mean area penetrated (in percentage) by dye on the split surfaces when root surfaces were covered with (a) or without (b) inlay wax. Significant difference exists in both conditions (P < 0.0001).