Influence of bismuth oxide concentration on the pH level and biocompatibility of white Portland cement

Objectives

To investigate if there is a relation between the increase of bismuth oxide andthe decrease of pH levels and an intensification of toxicity in the Portlandcement.

Material and Methods

White Portland cement (WPC) was mixed with 0, 15, 20, 30 and 50% bismuth oxide, inweight. For the pH level test, polyethylene tubes were filled with the cements andimmersed in Milli-Q water for 15, 30 and 60 days. After each period, the increaseof the pH level was assessed. For the biocompatibility, two polyethylene tubesfilled with the cements were implanted in ninety albino rats (n=6). The analysisof the intensity of the inflammatory infiltrate was performed after 15, 30 and 60days. The statistical analysis was performed using the Kruskal-Wallis, Dunn andFriedman tests for the pH level and the Kruskal-Wallis and Dunn tests for thebiological analysis (p<0.05).

Results

The results showed an increase of the pH level after 15 days, followed by a slightincrease after 30 days and a decrease after 60 days. There were no significantstatistical differences among the groups (p>0.05). For the inflammatoryinfiltrates, no significant statistical differences were found among the groups ineach period (p>0.05). The 15% WPC showed a significant decrease of theinflammatory infiltrate from 15 to 30 and 60 days (p<0.05).

Conclusions

The addition of bismuth oxide into Portland cement did not affect the pH leveland the biological response. The concentration of 15% of bismuth oxide resulted insignificant reduction in inflammatory response in comparison with the otherconcentrations evaluated.