This study has demonstrated that it is possible to extend the application of quantitative methods to aspects of OPD's functioning other than the appointment system. To prove that point it has not been necessary to collect much more information than what is needed to change an appointment system. In any case, the little extra effort required is more than compensated by the valuable insights provided by the simulation of a different work organization. Moreover, the relative insensitivity of results to changes in assumptions reveals that the latter are secondary elements whereas work organization is a primary factor and deserves careful attention. We do not mean that our conclusions about parallel treatments are directly applicable to any Dental Clinic nor that a modified work organization should produce ""miracles"" in any type of Clinic. We rather mean that the above results should be an encouragement towards a better use of data and a more ambitious way of formulating the problems that should and can be solved