Computer Dentist,
You'll probably get better answers at the Dental forum and not here at the Pre-Dental forum. But from what I have read, if you study off the Dentaldecks, that itself will be suffice to get you at least 80s on your NDBE Part 1. I've read stories that dental students only study using the Dentaldecks and received 90s in all four of the subsections of NDBE Part 1.
NOTE: this is not my experience, I have no experience with NDBE, THIS IS ONLY WHAT I HAVE READ FROM THE SDN DENTAL FORUM. Try your question there. 😎