While using lucida fonts, I have big problems with the height of the horizontal line of the radix or root symbol. Sometimes
\[ \sqrt[x^2 + x} \]
comes out allright, but for example, in a fraction
\[ \frac{x^2 + x}{x^2 + x} \]
, the exponents "2" stick literally to the horizontal radix line. I tried to fix that using a vertical strut
$\newcommand{\S}{\rule[0pt]{0pt}{1.6 ex}}$
and variants of it and write
\[ \frac{ \sqrt{\S x^2 + x} }{ \sqrt{\S x^2 + x} } \]
but this does not help. Does anyone have better ideas?