In the May, 2018 volume 35 issue of Contemporary Pediatrics, Dr. Farber details several observations and tips for office practices. Among them, he writes about TGuard.
Item 6 on his list of 8 items: “TGuard, formerly ThumbGuard, devices (MED et al, Incorporated; Matthews North Carolina) can be useful for thumb-sucking. Bitter-tasting products that are applied to the thumb seem less likely to work, unless the child is motivated to stop. That is, they appear to operate more as a reminder to that the thumb out, rather than as an actual deterrent.”