If the filed asked about is regarded as a blemish or deformity then there is nothing wrong with correcting the teeth in that case, and that is not included in the hadeeth of ‘Abd-Allaah ibn Mas’ood (may Allaah be pleased with him) who said: “May Allaah curse the women who do tattoos and the women who have them done, the women who pluck eyebrows and the women who file their teeth, altering the creation of Allaah.” Narrated by al-Bukhaari (4886) and Muslim (2125). 

Filing teeth was done to make the woman look younger or make the teeth look more beautiful. 

Al-Nawawi (may Allaah have mercy on him) said: 

As for the words “women who file teeth for the purpose of beauty”, what this means is that they do that with the aim of beautification. This implies that what is forbidden is that which is done for the sake of beautification. But if it is needed for medical reasons or to correct a fault in the teeth and so on, there is nothing wrong with it. 

And Allaah knows best. End quote. 

See also the answer to question no. 47694. 

And Allaah knows best.