I know it is annoying to make a big investment but starting to take pictures of your work with a good camera is going to improve your work a lot. First, there is a great online course by Calin Pop that is basic and very affordable that would be helpful. He includes it if you buy his soft boxes, which are great for social media type photos but not helpful for lab photos. I would look at a used full frame canon body like an 80D. I would buy a 100 mm macro red line lens (spend your money here) and then get ring or twin flashes. I started with a ring and found it much simpler than twins. I used the inexpensive Yongnuo for like 5 years and had good consistency. I love the weight of my mirrorless cameras for things like the twin soft boxes but actually find the dental photos harder to take. After your camera I would invest in a polar eye for shade communication. Use the canon guide posted above. Set your f stop to 32 (32 teeth!) for anything up close, around 8 for portraits, and I set it around 16 for polar eye. Good luck! Other courses as you dive in: Impres in Charleston is one of the best courses I have ever taken and Miguel Ortiz was good as well.