  We study the charmonium spectrum using a complete one gluon exchange approach
based on a phenomenological relativistic $q\bar{q}$ potential model with Dirac
spinors in momentum space. We use phenomenological screening factors to include
vacuum quantum effects. Our formulation does not rely on nonrelativistic
approximations. We fit the lowest-lying charmonia (below the $D\bar{D}$
threshold) and predict the higher-lying resonances of the spectrum. In general,
we reproduce the overall structure of the charmonium spectrum and, in
particular, we can reasonably describe the $X(3872)$ resonance mass as (mostly)
a $c\bar{c}$ state. The numerical values of the free parameters of the model
are determined taking into account also the experimental uncertainties of the
resonance energies. In this way, we are able to obtain the uncertainties of the
theoretical resonance masses and the correlation among the free parameters of
the model.
