A HISTOLOGICAL AND QUANTITATIVE HISTOMORPHOMETRIC STUDY OF APEXIFICATION OF NONVITAL PERMANENT INCISORS OF VERVET MONKEYS AFTER REPEATED ROOT FILLING WITH A CALCIUM HYDROXIDE PASTE

The purpose of this study was to compare the effect of a monthly refil ling of the root canals with calcium hydroxide paste with a single pac king or replacement of the paste at 3 months on the apexification of n onvital maxillary incisors of vervet monkeys. Forty-eight maxillary in cisors from 12 monkeys were used following radiographic determination that root development was incomplete. The pulps were extirpated under general anesthesia and the root canals filed and cleaned. The root can als were filled with a commercial calcium hydroxide paste, Calxyl, and a temporary cavity filling placed. Twelve teeth were left without fur ther treatment. The calcium hydroxide paste was replaced in 12 teeth a fter a 3-month interval, and in the remaining 24 teeth the calcium hyd roxide root filling was replaced five times at monthly intervals. The monkeys were killed after 6 months, and blocks of the teeth and surrou nding tissues were embedded, decalcified and 6 mu m serial sections pr epared and stained. The sections were studied histologically to evalua te 11 parameters. Significant differences were found in the amount of calcium hydroxide at the apices, the presence of new cementum on the r oots and the degree of inflammation, all of which were better in the m onthly refill group. Histomorphometric measurements to evaluate the ob turation of the open apices and the volume of new primary osteocementu m showed no significant difference between the three groups. It was su ggested that after the initial root filling with calcium hydroxide the re was nothing to be gained by repeated root filling either monthly or after 3 months, for at least 6 months.