Generally, teething starts after the first two weeks of a puppy’s life. Deciduous teeth fall out by the time a puppy turns twelve weeks. Generally, a puppy’s adult teeth grow by the end of the sixth month. This is a general timeframe for all dog breeds. However, some puppies get their first teeth sooner, or later.  Small deviations shouldn’t be worrying. Teething is a painful process that comes with many symptoms. Mood swings, lack of energy, lack of appetite, or disinterest are completely normal. If you are wondering why your dog is sleeping under the bed - the answer might just be teething. Dogs seek a calm, nurturing environment during this period. The important thing, though, is to keep the dental care of your puppy on a high level.  Regular usage of toothpaste and a toothbrush will reduce the  possibility of tartar build-up on your puppy’s teeth.