Biological evaluation of novel phosphorylated pullulan-based calcium hydroxide formulations as direct pulp capping materials: An in vivo study on a rat model

Aim

Calcium hydroxide (CH) has been considered as a direct pulp capping materials (DPC) for the last decades despite having some limitations. Phosphorylate pullulan (PPL) incorporated with CH (CHPPL) is a novel biomaterial that was introduced as a promising DPC material. Thus, the aim of the study was to evaluate the inflammatory response and mineralized tissue formation (MTF) ability of PPL-based CH formulations on rat molars after DPC.

Methodology

This study consisted of six groups: CH with 1% PPL (CHPPL-1); 3% PPL (CHPPL-3); 5% PPL (CHPPL-5); Dycal and NEX MTA Cement (N-MTA) as the positive control, and no capping materials (NC). One hundred twenty maxillary first molar cavities were prepared on Wistar rats. After capping, all the cavities were restored with 4-META/MMA-TBB resin and pulpal responses were evaluated at days 1, 7, and 28. Kruskal–Wallis followed by Mann–Whitney U-test was performed with a significance level of 0.05. Immunohistochemical expression of IL-6, Nestin, and DMP-1 was observed.

Results

At day 1, CHPPL-1, N-MTA, and Dycal exhibited no to mild inflammation, whilst CHPPL-3, CHPPL-5, and NC showed mild to moderate inflammation, and the results were significantly different (p < .05). At day 7, mild to moderate inflammation was observed in CHPPL-1, N-MTA, and Dycal, whereas CHPPL-3, CHPPL-5, and NC exhibited moderate to severe inflammation. Significant differences were observed between CHPPL-1 and N-MTA with NC (p < .05), CHPPL-1 and CHPPL-3 with CHPPL-5 and Dycal (p < .05), and CHPPL-3 with N-MTA (p < .05). A thin layer of mineralized tissue formation (MTF) was observed in all groups. At day 28, CHPPL-1, Dycal, and N-MTA showed no to mild inflammation, whilst CHPPL-3, CHPPL-5, and NC exhibited mild to severe inflammation, and statistically significant difference was detected (p < .05). CHPPL-1, Dycal, and N-MTA exhibited continuous MTF, whilst CHPPL-3, CHPPL-5, and NC had thicker and interrupted MTF. Significant differences were observed between CHPPL-1, CHPPL-3, and N-MTA with NC group (p < .05). Variable expressions of IL-6, Nestin, and DMP-1 indicated differences in the materials' impact on odontoblast-like cell formation and tissue mineralization.

Conclusions

These findings suggest that CHPPL-1 has the potential to minimize pulpal inflammation and promote MTF and had similar efficacy as MTA cement.