וְגַם־אֲנִי֩ נָתַ֨תִּי לָכֶ֜ם נִקְי֤וֹן שִׁנַּ֙יִם֙ בְּכָל־עָ֣רֵיכֶ֔ם וְחֹ֣סֶר לֶ֔חֶם בְּכֹ֖ל מְקוֹמֹֽתֵיכֶ֑ם וְלֹֽא־שַׁבְתֶּ֥ם עָדַ֖י נְאֻם־יְהוָֽה׃
און איך אױך האָב אײַך געגעבן לײדיקע צײן אין אַלע אײַערע שטעט, און איר האָט זיך ניט אומגעקערט צו מיר, זאָגט גאָט.
Rashi
Cleanness of teeth Heb. נִקְיוֹן שִׁנַּיִם. Setting your teeth on edge. [I.e, they would have nothing to eat, and their teeth would be set on edge.] Another explanation: cleanness of teeth. This denotes the lack of meat, which goes between the teeth, as it is stated: (Num. 11:33) “The meat was still between their teeth.”