brushing teeth, my cousin's dog taught me something

I don't have a pet of my own but last month my cousin went to Bangkok for work and left me her Shih Tzu, Lek, for 10 days. I was the one who had to do everything for him, and the teeth thing was a surprise. His breath was so bad I thought something was wrong with his stomach. I asked the vet at the local clinic in Lipa Noi. She said most small dogs get tartar by age 4 if nobody brushes, and once it builds up you need a cleaning under anesthesia, which is not cheap. She showed me how to use a soft brush and a dog toothpaste with the flavour, not the human one, because human toothpaste has things dogs should not swallow. We did it every night for 10 days with him sitting on my lap. At first he hated it. By day 6 he was waiting by the bathroom door. Lek is going home to my cousin on Saturday and I already bought a small brush for her. The main thing I learned is that the smell tells you more than you think. If the breath is strong, it is not normal.