Puppies will loose their puppy teeth and develop their adult ones. Teething usually begins at about 16 weeks and continues to six or seven months. You will notice increased and more agressive chewing, possibly the puppy pawing its mouth or running its face and possibly spots of blood on chew toys. You may find teeth on the floor or in toys it chews. This is all normal. The chewing is helping to loosen the first teeth and help them come out, while helping the permanent teeth to come in straight and strong.
        While teething be sure that your puppy has lots of good chew toys. You may also find that ice cubes or cold carrots help - the cold will help ease the discomfort, as will a frozen damp washcloth - all used with supervision. Be extra sure to keep other thigns away from its reach. And - you will survive it even if you think your puppy is going to chew the house down.

    Dog and Puppy teeth info:

puppies have 28 deciduous teeth  I = incisor  C = canine  P = premolar  M = molar   deciduous teeth designated as Di, Dc and Dp  so a puppy is 2 ( Di 3/3 - Dc 1/1 - Dp 3/3 ) = 28 teeth in total

 and permanent teeth  2 ( I 3/3 - C 1/1 - P4/4 - M2/3 ) = 42  thus dogs have 42 permanent teeth

 to further explain the time frame:  Di 1, 2 appear at 4 to 5 weeks  Di 3 at 5 to 6 weeks  Dc at 3 to 4 weeks  Dp 2 and 3 at 4 to 6 weeks  Dp 4 at 6 to 8 weeks

 on to the permanent teeth:  I1and I2 at 2 to 5 months  I3 at 4 to 5 months  C at 5 to 6 months  P1 and P4 at 4 to 5 months  P2 and P3 at 5 to 6 months  M1 at 5 to 6 months  and finally M2 and M3at 6 to 7 months

 the following data was found reliable in ~90% of large dogs with more variation in small breeds especially toybreeds.
 level bites usually produce excessive wear.

 1 1/2 years  cusps worn off lower I1

 2 1/2 yrs cusps worn off lower I2

 3 1/2 yrs cusps worn off upper I1

 4 1/2 yrs cusps worn off upper I2

 5 yrs. cusps of lower I3 slightly worn. Occlusal surface of lower I1 and I2
rectangular. slight wear of canines.

 6 yrs cusps worn off lower I3. canines worn blunt. lower canine shows
impression of upper I3

 7 yrs. Occlusal surface of lower I1 elliptical with the long axis sagittal

 8 yrs.  Occlusal surface of lower I1 inclined forward.

 10 yrs. Lower I2 and upper I1 have elliptical occlusal surfaces.

 12 yrs. Incisors begin to fall out ( unless care has been taken to maintain
healthy gingival and periodental tissues )