Quenottes is a charming and informal French word for "teeth", often used to refer to baby teeth. It's a bit like saying "pearly whites" in English.
In the song, the singer describes a dramatic transformation. He sings that he used to have 'dents d'loup' (wolf's teeth) but has traded them in for quenottes. This powerful metaphor illustrates how love has tamed him, changing him from a tough guy into someone gentle and devoted.
This song is a hilarious and slightly dark look at falling completely under someone's spell. The singer tells us he used to be a tough guy who never bowed to anyone: "Je n'avais jamais ôté mon chapeau / Devant personne" (I had never taken off my hat / For anyone). He was a "chien méchant" (mean dog) with "dents d'loup" (wolf's teeth). But now? He's been totally tamed by a woman he compares to a doll, saying "Je m'suis fait tout petit devant une poupée" (I made myself very small in front of a doll).
But this isn't just any doll. She has a sweet side, with "dents de lait" (baby teeth) when she smiles, but she also has "dents de loup" (wolf's teeth) when she's angry. The singer knows he's in deep, and even seems to accept his fate with a shrug. He was warned that in her arms he would suffer his "dernier supplice" (final torment), but his attitude is, if you have to give up your freedom, it might as well be for her. It's a funny, fatalistic take on being hopelessly in love.