This aayah does not mean that it is not allowed to have one’s teeth straightened
Question

Allaah says (interpretation of the meaning): “Verily, We created man in the best stature (mould)” [al-Teen 95:4], yet nowadays we find people going to orthodontists to have their teeth straightened. What is the ruling on that?.
Praise be to Allah.What is meant by the verse (interpretation of the meaning): “Verily, We created man in the best stature (mould)” [al-Teen 95:4] is that Allaah created man in the best form and shape, sound and good-looking, as Ibn Katheer (may Allaah have mercy on him) said in his Tafseer (4/680). 
Al-Qurtubi (may Allaah have mercy on him) said: “in the best stature (mould)” means: he is upright and sound in his youth, as most of the mufassireen said, and he is the best that he can be, because He created everything else looking face down, but He created him upright, with a tongue, and a hand and fingers with which to grasp things. Abu Bakr ibn Taahir said: Adorned with reason, able to follow commands, guided by means of discernment, standing upright, picking up his food with his hand. End quote from Tafseer al-Qurtubi (20/105). 
This does not mean that a person should not have his teeth treated, or have them straightened if they are crooked, just as he is not prevented from treating any other sicknesses. What matters is that he should not do that merely for the purpose of beautification, because the general principle with regard to cosmetic procedures is that if they are done to remove a deformity or fault, there is nothing wrong with them, but if they are done merely for purposes of beautification, then they are not allowed. See: Majmoo’ Fataawa al-Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him), vol. 17, question no. 4. 
He (may Allaah have mercy on him) was asked: What is the ruling on having the teeth straightened? 
He replied: Straightening the teeth falls into two categories. 
1 – Where the purpose is to increase beauty. This is haraam and is not permissible. The Prophet (peace and blessings of Allaah be upon him) cursed the women who filed teeth for the purpose of beauty and altered the creation of Allaah, even though women are required to look beautiful and they are the ones who grow up with adornments, so it is even more forbidden in the case of men. 
2 – Where they are straightened because of a fault; there is nothing wrong with that. Some people may have teeth that stick out – either the incisors or other teeth – in a way that makes them appear ugly to others. In this case there is nothing wrong with straightening the teeth, because this is removing a fault and not increasing beauty. This is indicated by the fact that the Prophet (peace and blessings of Allaah be upon him) told a man whose nose had been cut off to get a nose made of silver, then when that caused a foul smell he told him to get a nose made of gold. This was a case of removing a fault; the aim was not to increase beauty. End quote from Majmoo’ Fataawa al-Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him), vol. 17, question no. 6. 
See also the answer to question no. 21255. 
Conclusion: The verse does not mean that it is forbidden to have the teeth treated and straightened in order to remove a deformity or fault.  
And Allaah knows best.