set one's teeth on edge; cringeworthy; saccharine
Describes something so overly sweet, flattering, or sentimental that it makes one cringe, as if one's teeth are floating. Often used for insincere compliments or cheesy lines.
I'm fed up with his cringeworthy flattery.
The love scenes in that movie were full of saccharine lines.
Literally 'as if one's teeth are floating'. The phrase evokes the unpleasant sensation of teeth loosening or floating, metaphorically applied to overly sweet or cloying words.