Radiographic and histologic evaluation of the effect of two concentrations of formocresol on pulpotomized primary and young permanent teeth in monkeys.

The behavior of pulp tissue under two concentrations of formocresol was evaluated radiographically and histologically in pu/potomized primary and young permanent monkey teeth. A faster resorption rate of the roots of the treated primary teeth was observed with both concentrations. Evidence of vital tissue as expressed by continued root development was observed in the permanent teeth of both treated groups, but a milder degree of inflammation was seen in the diluted concentration group. Controversial findings have been reported concerning pulp reaction following formocresol pulpotomy treatment. 1-s Histologic investigations describe several pulpal changes ranging from the ingrowth of connective tissue through the root apex to total coagulation of the pulp and necrosis. 2’9-n The presence of vital tissue in pulpotomized primary molars treated with formocresol has been demonstrated previously. 12’ ~:~ Despite this fact, there is no uniform reaction to formocresol, and a "very capricious behavior" of the pulp under formocresol has been described. 1° Straffon tested the effect of formocresol on hamster connective tissue cells and observed a definite reduction in the number of inflammatory cells and a faster recovery of the tissue with decreased formocresol concentrations. 14 Further biochemical and histochemical investigations confirmed these results. ~’~’~ From these studies it became evident that a 20% dilution was the most favorable, being as effective as the full concentration and yet allowing a faster recovery of the affected cells. ~5-~7 Escobar tested the effect of a 20% dilution of formocresol on monkey primary molars and suggested that this could be an alternate medicament for primary vital pulpotomy procedures. 18 Morawa et al. tested this medicament clinically in primary teeth of children and concluded that it was equal or even better than the full strength formocresol. ~8’ t9 The continued apical formation of immature permanent teeth treated with formocresol has been studied previously. ~° This investigation has been carried out in periods of time not exceeding 150 days. It is generally believed that the success rate of formocresol pulpotomies decreases with time. 2~ The purpose of the present investigation was to evaluate the long-term effects of pulpotomies with two concentrations of formocresol upon the root resorption of primary molars, and the continued apical formation of immature permanent teeth in the rhesus monkey. Methods and Materials Two rhesus monkeys approximately 20 months old were used in this study. Both had noncarious primary molars; the first permanent molars and the permanent incisors had erupted at the beginning of the experiment. The animals were anesthetized by a pentothal solution IV (50 mg per kg bodyweight). Preoperative periapical radiographs taken immediately before treatment revealed both the stage of root resorption of the primary molars and the degree of root development of the permanent teeth. The latter had incomplete roots and their apices were wide open (Figure la). Pulpotomies initially were performed in all the primary molars and in the permanent first molars and central incisors. Subsequently, the other permanent teeth were treated in groups, as soon as the erupting teeth provided enough clinical crown to allow placement of a rubber dam. Each monkey was treated four times.