Dry foods prevent dental disease better than canned or semi-moist foods.
Dry foods may indeed provide better cleaning action on the sides of the teeth than a canned or semi-moist food. However, there are several important factors to consider beyond the food being simply moist or dry. The nutrient composition is an important food factor in addition to the texture of the food in managing dental disease. Breed, age, immune status, chewing behavior, and dental structure are all animal factors that must be taken into consideration. Only pet foods with the Veterinary Oral Health Council [VOHC] seal of acceptance have been shown to aid in oral health. We recommend you look for this seal when looking for a diet to help your pet's oral health.
If you have more specific questions - Ask the Nutritionist.