This uses the stackengine package to construct the glyph from \circ.
\documentclass{article}
\usepackage{stackengine}
\usepackage{xcolor}
\usepackage{graphicx}
\def\dottedcirc{\color{white}%
\stackinset{c}{}{c}{-.4pt}{--}{%
\stackinset{c}{}{c}{-.5pt}{--}{%
\stackinset{c}{}{c}{.1pt}{\rotatebox{90}{$-$}}{%
\stackinset{c}{}{c}{.1pt}{\rotatebox{45}{$-$}}{%
\stackinset{c}{}{c}{.1pt}{\rotatebox{-45}{$-$}}{%
\textcolor{black}{$\circ$}%
}%
}}}}\color{black}}
\begin{document}
x\dottedcirc y
\end{document}

I EDITED the solution when I found that a lower-case o immediately preceding the \dottedcirc was slightly overlapped. Here I use two slightly overlapped n-dashes (--) in lieu of a minus sign ($-$) for the horizontal whiteout stroke.
If you substitute red for white, you can see how the stack is formed:

Based on comment from OP, I cannot easily make the dashed circle dotted in the sense of using small circles around the perimeter. However, I can subdivide the sircle more frequently with smaller dashes, giving a similar appearance:
\documentclass{article}
\usepackage{stackengine}
\usepackage{xcolor}
\usepackage{graphicx}
\def\dottedcirc{\color{white}%
\stackinset{c}{}{c}{-.4pt}{--}{%
\stackinset{c}{}{c}{-.5pt}{--}{%
\stackinset{c}{}{c}{.2pt}{\rotatebox{90}{$-$}}{%
\stackinset{c}{}{c}{.2pt}{\rotatebox{30}{$-$}}{%
\stackinset{c}{}{c}{.2pt}{\rotatebox{60}{$-$}}{%
\stackinset{c}{}{c}{.2pt}{\rotatebox{-30}{$-$}}{%
\stackinset{c}{}{c}{.2pt}{\rotatebox{-60}{$-$}}{%
\textcolor{black}{$\circ$}%
}%
}}}}}}\color{black}}
\begin{document}
x\dottedcirc y
\end{document}

which, blown up, is

Look for V3.21 of stackengine to be propagated in the coming days, to fix a bug associated with \stackinset, when using l or r horizontal justification.
\usepackage{fontspec}and removeinputencandfontenc? See http://tex.stackexchange.com/questions/2984/frequently-loaded-packages-differences-between-pdflatex-and-xelatex. – doncherry Oct 15 '13 at 11:57\dottedcircle– David Carlisle Oct 15 '13 at 14:37