Is it permissible for a woman to have her teeth treated and braces fitted by a male dentist, especially if she is unable to afford private treatment and free treatment is available through a trainee dental student?

It is permissible for a male doctor to treat you out of necessity, such as the absence of a female doctor who can perform the required treatment, or the inability to afford the treatment with a female doctor. However, if there is a female doctor whose fees you can afford, then it is not permissible for a male doctor to treat you.