It’s a subscore on the DAT so it’s still important but not nearly as important as your Academic Average. Scoring well in the PAT section shows schools you possess a skill that’s critical to practicing dentistry. Obviously if you don’t do as well you can still learn this skill, but it’s a metric used by schools, so I would still study for it. Doing 10 practice problems a day will help you find the tricks needed to be successful.
A PAT less than 17 will probably get you screened out by schools since I believe the average PAT of those that matriculate is around ~20.5. So you should try to shoot for that or higher.