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Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. I am tired of searching coupons, but I found one for you…
Link: Banggood product page
Coupon (28.22 USD): 00c906
(CouponsFromChina.com tip: just apply this code in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BGBTJU50, BGHU0275, BGBTJUT6, BGFE25ZXY, BGAFF10OFF, BGPFHC01, BGMASE01, BGORALIRRI2, BGitIPX6, BGMA2904, BGAP2713, BGGREE1002, BGMAR2406, BGwhielabel, 13f142, BG10OFFAFF1, BGSEXP152, BGHealth06
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for Electric Dental Calculus Remover is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).