I have not heard of Mama bonsai. Do you mean Mame?
All trees put on layers of new wood every season. If they grow a lot the layers are thicker. If they don't grow much layers are thin. Mame bonsai that are carefully controlled thicken very slowly so they can have the same pot for many years. Eventually the trunk will get too thick to look good in the original pot and it will need a larger pot.
Some species thicken quicker than others, even when growth is restricted. My ficus rubiginosa just grow fatter every year despite careful and regular trimming. A couple I started as shohin size have had to have pots upsized twice in 30 years.