Did a quick Google search on Mentadent because it was the only toothpaste my mom would use and it suddenly fell off the face of the earth. Good news! It's available on Amazon for a mere $200.
Btw people. You can still get it here. It's completely worth it!! ARM & Hammer Mentadent Advanced Whitening 2 refills 5.25 Oz https://www.amazon.com/dp/B00CBZ8NT2/ref=cm_sw_r_cp_apa_i_ziXwDbSGDWNYP
I didnt think the three pack was a good price
https://www.amazon.com/dp/B018IVNV80/ref=cm_sw_r_cp_awdb_t1_fkXwDbZPCETJ5
Um, if you're rich it's on Amazon. $200.00 for a two pack.