You are correct. At the end of the video (timestamp approximately 10:40-10:46), the dentist mentions having SDF (silver diamine fluoride) staining between her back teeth, explaining the dark coloration visible in that area. This is not related to the Autobrush Pro's cleaning ability but is pre-existing staining.
Based solely on the provided transcript, the dentist mentions having SDF (silver diamine fluoride) staining between her back teeth. The transcript does not offer a further explanation of what SDF is.
This video is a dentist's review of the Autobrush Pro U-shaped toothbrush. The dentist discusses a previous study indicating U-shaped brushes are not as effective as traditional brushing, then reviews the Autobrush Pro, its features, and its effectiveness based on personal use and disclosing tablets.