A primary embodiment of the invention is a composition for an antimicrobial dental gypsum comprising a calcined gypsum, an additive, an antimicrobial agent and an antimicrobial enhancing substance. The antimicrobial agent comprises a benzoic acid and/or a benzoic derivative. The antimicrobial agent is in the range of 0.001 to 0.02% by weight of the composition. The antimicrobial enhancing substance comprises IPBC in the range of 0.0001 to 0.01% by weight of the composition. The benzoic derivative can be sodium benzoate, potassium benzoate and/or calcium benzoate. The additive can be a thickener, a retardant, an accelerator, a defoamer, a pigment, a stabilizer and/or a dye in the range of 2.5 to 3.5 percent by weight of the composition. The antimicrobial enhancing substance can further comprises citric acid, propionic acid, tartaric acid, acetic acid, oxalic acid, malic acid, salicylic acid, lactic acid, gluconic acid, hydroxyacetic acid and/or methylisothiazolinone.
