All dogs are born without teeth. Between the ages of 3 and 6 weeks, however, a dog will get its milk, or deciduous, teeth. On emerging, these 28 teeth are sharp enough to help the animal transition to eating solid foods. Deciduous teeth last between four months and a year, during which time the dog's permanent teeth gradually replace them, absorbing the roots of the milk teeth as they do.
This replacement process is known as teething. When it's completed, the dog will have 42 adult teeth.
Although dogs experience the discomfort of teething most intensely between the ages of 2 and 7 months, minor discomfort may occur for as long as a year until the adult teeth have fully emerged.
Dogs get their permanent incisors between the ages of 2 and 5 months. Their premolars will erupt at between 4 and 6 months, while their canine teeth and molars appear between 5 and 7 months.
So yes the teeth you observe are Deciduous not permanent. They will be replaced by permanent teeth but it doesnt happen like human teeth where they fall off and a new one erupts.
I used Samolac for my puppy and she liked to have it but I feel one should be slow on giving supplements if you're giving him proper puppy food as it can upset the mineral balance of the pups body. Im not sure what you should do here as your vet is suggesting it. Try going for a second opinion.
It doesnt matter if you prepare it paste-like or syrupy as long as you mix the right amount of the powder in the water.