Biting comes naturally to puppies.
In a litter, they play by rolling over and biting each other even before they have developed their teeth.
A younger dog can cause more harm with his sharp teeth in spite of the fact that his lower jaw is week.
By the time he grows up his teeth may become duller but the strength in his jaws can inflict maximum damage.
Teaching young puppies that no teeth can touch human skin or clothes always help in the long term.