Plastic isn't a great material for a hamster to digest. It wouldn't harm them to chew on it however if you notice your hamster eating the plastic you will need to remove it from the cage immediately. Plastic is a very common material used for modular cages and is able to be chewed through. But plastic is a very nice material for hamsters who are not big chewers. 

Ceramic houses are very easy to clean. However, they are very fragile. They are also very heavy. If you are going to place on of these in your hamsters cage you must be sure it is not too heavy. If it is to heavy, it will be sink into the bedding. If it's falling in the bedding to the bottom your hamsters cage your hamster may happen to be under it at that time and may get crushed. So be sure it's not to heavy or you bury it a bit so that it touches the base of the cage.

Wood is a very natural material used for some hamster houses. They can be sanitizes by simply filling a reasonably sized pot with water, placing it on a burner. Once it has began a soft boil you may take some sort of utensil, such as tongs, and place the wooden item into the boiling water. Keep a close eye on this because if it's boiling for to long it may break apart or become ruined.