Effect of bentonite-activated carbon fillers addition to type II dental gypsum on its compressive strength, wettability, setting time, and setting expansion

BACKGROUND: Dental plaster, dental stone, and improved stone are commonly used gypsum products for dental molds. While improved stone is preferred for final molds due to its strength, dental plaster is cheaper but has low compressive strength, limiting its use to temporary models. OBJECTIVE: To evaluate the compressive strength, wettability, setting time, and setting expansion of Type II dental plaster modified with 10 wt% calcium bentonite and activated carbon fibers. METHODS: The modified dental plaster had significantly higher compressive strength (43.5 ± 1.4 MPa) than the conventional dental plaster (24.3 ± 1.3 MPa) and improved stone (36.1 ± 0.4 MPa) (P 0.05). There were no statistical differences between groups regarding initial or final setting times (P > 0.05). RESULTS: The modified dental plaster displayed significantly higher compressive strength (43.5 ± 1.4 MPa) compared to conventional dental plaster (24.3 ± 1.3 MPa) and improved stone (36.1 ± 0.4 MPa) (P < 0.001). Wettability was obviously improved, with a contact angle of 0° ± 0, compared to 99.3° ± 0.2 for conventional plaster and 93.6° ± 0.6 for improved stone (P < 0.001). Setting expansion was significantly decreased in the modified group (0.05% ± 0.01) compared to conventional plaster (1.36% ± 0.01), with no significant difference from improved stone (0.07% ± 0.01) (P > 0.05). No significant differences were shown in initial or final setting times among the groups (P > 0.05). CONCLUSION: Incorporation of 10 wt% Bentonite-activated carbon fillers markedly improve the compressive strength and wettability of Type II dental plaster, reducing setting expansion without compromising setting time. Modified material has the potential to be a tooth and plaster accelerated cement automatic operation, which is a more economical solution than traditional Type IV improved stone for dental model purposes.