This is the only study I could find
Taillefer A, Casasoprana A, Cascarigny F, Claudet I.
Journal
Arch Pediatr. 2012 Oct;19(10):1058-64. doi: 10.1016/j.arcped.2012.07.003. Epub 2012 Aug 24. Article in French.
Affiliation
Abstract
Numerous infants wear teething necklaces, a quack remedy with a real risk of strangulation or aspiration of small beads.
AIMS: Evaluate parental perceptions and beliefs about the use of teething necklaces and analyze parental knowledge about the associated dangers.
MATERIAL AND METHODS: Between March and July 2011, in three different pediatric units of a tertiary children's hospital and a general hospital in Toulouse and Montauban (southwest France), voluntary parents were invited to be interviewed about their child wearing a teething necklace. The interviews were conducted following an anthropological approach: they were recorded and then fully transcribed and analyzed. Parents were informed that the conversation was recorded.
RESULTS: During the study period, 48 children were eligible. Eleven families refused to participate, 29 parents were interviewed face to face. The children's mean age was 14 years ± 7 months, the male:female ratio was equal to 0.8 (12 boys, 15 girls). The mean age of children when necklace wearing was started was equal to 4 ± 2 months. The mean mother's age was 31 ± 5 years and 33 ± 4 years for fathers. The parents' religion was mostly Catholic (60%). Teething necklaces were mainly made of amber (n=23). Sales information about the risks associated with the necklaces was for the most part absent (92%). The most frequent positive parental perceptions were analgesic properties and a soothing remedy (73%); a birth accessory and memory (64%); an esthetic accessory (60%); a protective amulet (60%); and an alternative or additional element to other traditional therapeutics (55%). The negative parental perceptions (n=4) were an unnecessary accessory, costume jewelry, a pure commercial abuse of a popular belief, a dangerous item with a risk of strangulation, and the absence of proof of its efficacy.
COMMENTS: Although parents concede that teeth eruption is benign, they fear its related symptoms. To a natural phenomenon a natural response: they use a necklace to satisfy the analogy. The parental approach of this usage is consistent with accessorizing the child to protect and help them during a difficult stage. When informed of the danger of strangulation, numerous families preferred to continue this practice; their irrational fear of seeing their child suffer surpassed their fear of the risk of strangulation.
CONCLUSION: Putting necklaces on young children is dangerous. This risk must be diffused by all professionals working with small children in order to stop any publicity or sale of this ineffective product implicated in infant deaths by strangulation.