There is nothing wrong with breast implants or enlargement for one who has had a breast removed or who is suffering because they are small, because that comes under the heading of removing a fault or restoring something to the way it was created by Allah.
The evidence for that is the report narrated by Abu Dawood (4232), al-Tirmidhi (1770) and al-Nasaa’i (5161) from ‘Abd al-Rahmaan ibn Tarafah, that the nose of his grandfather ‘Arjafah ibn As‘ad was cut off in the battle of al-Kulaab, and he wore a nose made of silver, but it began to stink, so the Prophet (blessings and peace of Allah be upon him) told him to get a nose made of gold. This hadeeth was classed as hasan by al-Albaani in Saheeh Abi Dawood.
Please see the comments of the scholars concerning this matter in the answer to question no. 138273 and 108860.
It is permissible to use botox if it is free from harm, because the Prophet (blessings and peace of Allah be upon him) said: “There should be neither harm nor reciprocating harm.”
Narrated by Ahmad (2865), Ibn Maajah (2341) and classed as saheeh by al-Albaani in Saheeh Ibn Maajah.
And Allah knows best.