La reabsorcion radicular asociada al movimiento dental es un efecto indeseado durante la terapia ortodoncica. El proposito de este estudio fue el de identificar los cambios dentinopulpares, el grado de reabsorcion radicular externa (RRE) y la cantidad de movimiento dental en pacientes medicados con rofecoxib durante la aplicacion de fuerzas ortodoncicas intrusivas de 2 onzas. La muestra la constituyeron 6 sujetos (12 dientes) en quienes se evaluaron 8 dientes para el grupo experimental (rofecoxib) y 4 dientes para el grupo control (placebo). Se utilizo un aparato fijo tipo barra transpalatina y un bracket adherido a tercio medio de la cara vestibular de los primeros bicuspides superiores, en cada segmento se instalo un alambre TMA con dobleces intrusivos que fueron activados cada seis semanas. El protocolo de administracion del medicamento y del placebo se planteo teniendo en cuenta la estabilizacion de su concentracion tras su administracion en forma regular. Como parte del tratamiento los premolares fueron extraidos y se realizaron los cortes respectivos, se utilizo coloracion de hematoxilina-eosina y tricromica de Masson para observar los cortes al microscopio de luz. En los cortes histologicos se observo en la capa odontoblastica mayores cambios morfologicos, aumento de las fibras colagenas y angiogenesis en el grupo experimental. Se encontro que el grupo control presento mayor cantidad de lesiones radiculares que el grupo experimental. Al medir la cantidad de movimiento dental, se observo que los rangos de movimiento bajo el rofecoxib fueron mayores que con el placebo. El rofecoxib mostro ser eficaz en la inhibicion de la RRE, comparado con un medicamento placebo en esta muestra. Con las actuales limitaciones del uso del rofecoxib, se puede decir que los inhibidores preferenciales de la ciclooxigenasa-2 (COX -2) presentan mejor control que los inhibidores especificos de la COX-2 en los cambios dentinopulpares deletereos que se presentan luego del movimiento intrusivo. ABSTRACT. Root resorption associated to dental movement is an undesired side effect during orthodontic therapy. The purpose of this study was to identify the changes in the pulp-dentine organ, the degree of external root resorption, and the amount of dental movement in patients under Rofecoxib treatment, during the application of 2 ounce-intrusive orthodontic forces. The sample consisted of 6 subjects (12 teeth) on whom 8 teeth were evaluated as the experimental group (Rofecoxib) and 4 teeth as the control group (placebo). A fixed device (transpalatal bar) was used and a bracket was attached to the middle third of the buccal surface of the first upper premolar. On each segment a TMA wire with intrusive bends was set and activated every 6 weeks. The protocol of drug and placebo intake was determined by taking into account the stabilization of their concentration after regular administration. As part of the treatment, the premolars were extracted and prepared for histological examination. These cuts were dyed with Hematoxilin-Eosin colorants and Masson’s Trichoromic in order to observe them under the light microscope. The histological cuts showed more morphological changes at the odontoblastic layer, with increase in the number of collagen fibers and angiogenesis for the experimental group. In contrast, the control group presented more root damage than the experimental group. The range of dental movement under Rofecoxib was greater than the range under placebo after measuring the degree of dental movement. The rofecoxib showed to be effective in the inhibition of the RRE, compared with a medication placebo in this sample. With the current limitations to the rofecoxib use, one can say that the preferential inhibitors of the COX-2 present a better control that the specific inhibitors of the COX-2 in the dentinopulpar deleterious changes that are presented after the intrusive movement.