Sainsburys have Arm & Hammer's Advanced Whitening Toothpaste for just 50p for a 75ml which is fantastic value! Other ones available but this is the cheapest, and nicest in my opinion!
Other dental deals include:
Half price Colgate Smiles Toothbrushes and Toothpaste (all £1 each)
Other Arm & Hammer toothpastes 1/2 price
Aquafresh Little Smiles toothpastes save 33% now 66p
Aquafresh adult toothpastes save 50%