Why do the numbers after quince, such as dieciseis, start to use a different form of spelling?

Why does it start to use the "ten part" instead of an independent name for the number? Does this have to do with a quinceanera, a woman's 15th birthday?
The reason why we have different spelling comes from latin, the natural number formation would be "ten" plus "a number" but languages are not very logic (we don't have diecicinco, diecicuatro, diecitrés, diecidós y dieciuno).

Once, doce, trece, catorce and quince come from undecim, duodecim, tredecim, quattuordecim, quindecim (the latin words underwent some phonological changes such as elission).


Source: http://www.csun.edu/~hcfll004/latin-numbers.html
El ce es un remanente de lo que antiguamente era decim. Sin embargo lo más interesante es por qué el cambio está dado en lo números 16,17,18 y 19, que no conuerdan con el actual modelo diez y (número):
16 sédecim
17 septendecim
18 duodévígintí
19 úndevígintí

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