The dental diet is pretty fatty in general, I've seen many pets become chunky after eating it with no exercise. A food we recommend is Purina veterinary OM (overweight management) for our obese cats, I see more success with it than the royal canin satiety support.
Wet food is key to a healthy cat as it greatly improves urinary health (kidneys, bladder, stones, crystals). Reasoning to this is that wet food has about 80% moisture making your kitty pee more and flush out her kidneys. OM comes in wet and dry giving your kitty a nice variety.
Exercise is also important though I see she goes outside, in addition to this you may buy one of those automatic lazer pointers that zoom around the room for you.
For dental health, brush daily with a soft finger brush and pet approved tooth paste - smearing the toothpaste on the teeth/gums will also help if you have difficulties brushing. There are feline dental chews you can get as well such as greenies or enzadent oral cat chews. Stay away from hard chew toys such as bones as they can become lodged in their intestinal tract or break teeth (most commonly seen in dogs).
I'll add a little extra in regards to her going outside. I highly recommend making an outdoor play area that makes her and the wildlife safe. Cats are killing vast amounts of wildlife and making certain species of birds, lizards and turtles extinct. This enclosure will keep your cat safe from predators like eagles, foxes and coyotes. The danger of getting hit by a car is another thing to consider or if she gets lost (microchip is key here).