in the early days in hospital, when we were having a bit of a tricky time getting the hang of breastfeeding, arty was getting quite distressed by the process. he was hungry, and we couldn't get him latched on and feeding efficiently. he would get so upset, and in the end his frustrated crying was stopping him from even attempting to feed.
one of the midwives suggested that we give him our litte finger to suck on when he got this upset, because the physical act of suckling is very soothing to babies. it worked instantly, and really helped us calm him and get on with learning to feed.
but then we found that we were sticking our fingers in his mouth six or seven times a day, and we couldn't always be sure hat they were as clean as we'd have liked them to be. we decided that using a dummy would be more hygienic.
importantly, we don't use the dummy in place of other forms of comfort, but it is one tool that often goes well with a cuddle, a song, and some reassuring words.