wet does not cause teeth problems and dry does very little to help. Maybe it will put off the amount of time it takes for teeth to rot but not by much. Dogs teeth will slowly go bad on any commercial kibble or wet food, the only dogs/cats who keep really nice teeth all their lives IME are raw fed animals. Wet food is generally higher in protein than dry food. I know for cats dry food is extremely unhealthy because of carbohydrate content that wet does not have. Dogs do handle carbs much better than cats (although I do believe dry food contributes to obesity in dogs as well) but I would not hesitate to say wet is healthier than dry in general. BUT it is expensive and for a dog (cats are a different story) there is nothing wrong with feeding dry, so don't worry about having to feed all wet food.
As far as that wet food goes, I would not feed it. First off there is more water in it than anything (first ingredient is the most abundant ingredient). Poultry is not specific, it could be chicken, turkey, duck, goose, etc. you should KNOW what is in your food, this product could even use a different poultry (chicken in one batch, duck in another) each time which could lead to tummy upsets in a sensitive dog and can make dealing with any allergies impossible.
Meat-By-Products are the parts of an animal other than meat. Again you have no idea what animal this is coming from at all, when the term "meat" is used, according to the dog food project website
The animal parts used can be obtained from any source, so there is no control over quality or contamination. Any kind of animal can be included: "4-D animals" (dead, diseased, disabled, or dying prior to slaughter), goats, pigs, horses, rats, misc. roadkill, animals euthanized at shelters and so on. It can also include pus, cancerous tissue, and decomposed (spoiled) tissue.
Not all by products are bad, organs are always nice and other parts are fine. The big problem is you still don't know what you are feeding. Again the amount of by product may be different in every batch. One batch might be liver and other organs, next batch might be feet and bones, next might be eggs found inside slaughtered animal. It's inconsistent, unknown nutrition and much of it IS indeed inferior nutrition.
finally, wheat flour and wheat gluten are automatic rejects for me they serve absolutely no purpose in a pet food, they are nutritionally empty for a dog. They cause poor overall condition to the dog because they are used instead of lots of nice healthy, nutritious meat. wheat is also a very common allergen in dogs.
So I don't think this is a good food. If you do not know about dog nutrition yet then chances are that the dry food is worse, it tends to be more grain heavy than wet food. But I also doubt that switching to a high quality food will do too much to your dog's teeth, it will help him in other areas (coat, energy, stench, nail quality, etc.) but not teeth.
Would you like some food suggestions?
I agree with ACampbell that raw meaty bones are great for cleaning teeth. I don't feel comfortable with recreational bones (risk of teeth breaking), but edible ones like necks and backs as were mentioned along with some others are great.
Dog tooth brushes and tooth paste are also available and work to remove plaque (not tartar), they don't work as well as the bones but they will definitely slow the build up of nastiness no your dog's teeth if they are brushed at least every three days. However your dog's teeth are already bad so he will probably still need a cleaning even if you start brushing and feeding raw bones right away. After the cleaning (ask the vet if he needs one but by the sound of it he does) start working hard on that oral health.
