pc.l Apical and Coronal Microleakage of Two Root Canal Filling Techniques. M. Carter, S. Frost, V. Karapanou*, C. Pastan, M. Goldman, R. White, Tufts University, Boston, MA

This study assessed apical and coronal dye leakage of a single gutta percha cone, resin sealer, filling technique compared with lateral condensation of gutta percha and sealer. 68 single canal teeth were instrumented to an apical size of 40 using a crown-down, step-back technique. To remove the smear layer, final irrigation with 15% E.D.T.A. was followed by 5.25% NaOCl. The teeth were then randomly divided into 2 groups of 30 and 4 controls. 30 samples in Gr. A were filled using lat. condensed g.p. and Z.O.E. sealer. A single fitted cone and resin sealer were used to fill the 30 teethin Gr. B. (+) controls were filled with loosely fitted g.p. w/out sealer. (-) controls were covered with sticky wax. Wax covered all but the apical foramen in 15 teeth from Gr. A and B. Wax covered all surfaces except the coronal access of the remaining 15 teeth in each group. After 7 days, all samples were placed in 2% methylene blue under a vacuum. The samples were then split longitudinally and measured for leakage by 2 examiners. Inter-examiner reliability correlated_. A students' "T" test demonstrated that the resin sealer demonstrated siqnificantly less coronal leakaqe than lateral conden- sation. There was no siqnificant difference in the apical leakaqe.

PIP C l Localization of superoxide dismutase immunoreactivity

t 9_9 in rat tooth following preparation. A.S. LAW* K.R.

BAUMGARDNER, and G.F. GEBHART. (Univ. of Iowa, Colleges of Dentistry and Medicine)

he oxygen radical superoxide has been implicated as a mediator of tissue damage during inflammation. A means by which cells can protect against superoxide is via superoxide dismutase (SOD), which catalyzes the conversion of superoxide to O 2 and HeOz . This study examined if pulp cells have this protection by determining the distribution of SOD- immunoreactivity (SOD-i) in the rat tooth following preparation. Dentin was removed from maxillary right t]rst molars of anesthetized rats. At 4 to 10 days rats were perfused with 2% paraformaldehyde and maxillary jaw segments were removed, post-fixed, decalcified, cryoprotected and serially sectioned (20 pan) for immunohistochemistry. Sections were stained with H&E or were reacted for Manganese-SOD (MnSOD-I:4,000), or Copper-Zinc SOD (CuZnSOD-I:4,000) inmmoreactivity. H&E sections showed pulp inflammation adjacent to prepared dentin. Most teeth had an area of necrosis directly beneath the prepared dentin. Both MnSOD-i and CuZnSOD-i were increased in cells adjacent to the prepared dentin and bordering the area of necrosis when compared to pulp tissue further from the inflammatory lesion, and. controls (unexposed pulps). Distribution of CuZnSOD-i and MnSOD-i was not limited to inflammatory cells, suggesting the possible presence in undifferentiated mesenchynml ceils. These rest/Its stjggest that superoxidc disnmtasc may intquencc the inflammatory process in the tooth pulp folloxving preparatiol3.

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PPG I An In Vitro Evaluation Of Sealer Placement Methods G. Korthals*, F. H. Kahn, P.A. Rosenberg, P. Nguyen New York University College of Dentistry, New York, N. Y.

Objective: Evaluation of the efficacy of six sealer delivery systems. Methods and materials: One hundred resin blocks with simulated root canals having a curvature of approximately 33 degrees were used as a test model. Working lengths were established and the canals were enlarged up to a #40 K-file using the step back technique. Ninety six of the blocks were randomly divided into six test groups, with the remaining four blocks serving as negative controls. The six sealer placement modalities were: absorbent paper points, #25 K-file, lentulo spiral, ultrasonically and sonically activated endodontic files, and a pressure syringe. AH26 sealer was used. Following setting of the sealer, the blocks were cut into 2.0 mm sections perpendicular to the long axis of the block. Attention was focused on the apical third of each canal. Under the stereo microscope at 6X magnification, the lumen of the canal in each section was divided into quadrants, and evaluated for the presence or absence of a complete layer of sealer at the surface of the section. The efficacy of each sealer system was determined by the percentage of total quadrants surveyed which contained a complete layer of sealer.

Results: The lentulo spiral delivered a complete layer of sealer in 100% of the quadrants from the apical third. The pressure syringe. ultrasonic files, and sonic files were the next most effective delivery systems. Least effective were the #40 K-file and paper point. The data was evaluated utilizing one-way analysis of variance and the results were statistically significant (p>.05).

This project was supported by a grant from Smith & Nephew MPL

SEM Examination of Apical Root Resorption due to Periapical Inflammation. L. MALUEG*, W. JOHNSON University of Iowa College of Dentistry

Ideal termination of the root canal filling remains a subject of debate. Extrusion of obturating material beyond the apical foramen has been shown to increase the incidence of failure following root canal treatment. This study examines the incidence and appearance of external apical root resorption (EARR) in the presence of periapical inflammation. Twenty roots from extracted human teeth were examined for presence of EARR. A pulpal diagnosis was established prior to extraction, based on patient signs, symptoms and pulp testing. A periapical diagnosis was determined based on radiographic changes and the patients response to percussion/palpation. A pulpal diagnosis of either normal, irreversible pulpitis or pulp necrosis was made. Teeth diagnosed with pulpal necrosis radiographically demonstrated either normal apical structures or apical bone resorption. After extraction, the roots were prepared for SEM examination. Photographs of the root apices were made at 60x magnification. Results indicate that apical inflammatory root resorption was present in roots of teeth with a clinical diagnosis of pulp necrosis and radiographic bone resorption regardless of radiographic evidence of apical root resorption. This finding suggests that ideal termination for the preparation and o_bturation of teeth with a diagnosis of pulp necrosis and ~ r a p h i c evidence of periapical .inflammation may be d_ifferent from that of other diagnostic categories.

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