Vol. 25, No. 4, Apri l 1999 Journal of Endodontics • 305

Pr~n I A scanning electron microscope evaluation of abrasives used in conjunction with ultrasonics for cleaning of root canals. L.E. Osnas, A.K. Mickel, N.Y El.Refai* Case Western Reserve University

The purpose of this study was to determine whether the addition of abrasives to ultrasonics and irrigation improved the efficacy of cleansing the root canal system in extracted human teeth. This study examined the use of abrasives as a means of increasing the effectiveness of ultrasonics in cleaning root canals. 73 extracted human teeth were selected and stored in sterile saline at 4°C. An access opening was created, working length established with a #15 file, then pre-flared with #2-4 GG drills, apical prepared (minimum #35) and step-back with SS K-files, and Profile 0.06 taper, lmL of sodium hypochlorite was applied after 3 files were used. Each treated group consisted of 21 teeth. The treatments were: 1) sodium hypochlorite and ultrasonics; 2) sodium chloride crystals, glycerine and ultrasonics; 3) aluminum oxide crystals, glycerine and ultrasonics. The controls were 5 teeth each: negative control with no treatment and positive control with micro-etching only. The teeth were sectioned buccal to lingual, prepared for the SEM and examined at 5mm from the apex. Th..___e.e analysis of the results showed a statistically significant difference in the removal of more smear laver b7 aluminum oxide than by sodium chloride or sodium hypochlorite treatments when used in conjunction with ultrasonics for cleaning root canals (P <0.05).

P)~[ Periradicular pathosis and the maxillary sinus: histologic, anatomic, and radiographic evaluation. HA Grote*, RE Walton, EM Rivera. The University of Iowa

Periradicular lesions likely impact the floor of the sinus because of their close anatomic relationship. Obiecti'~.es: 1) describe the histology of these inflammatory lesions and approximating sinus tissues, 2) examine bacteriological aspects of this relationship, and 3) correlate radiographic and gross anatomic features with histological findings. The hypothesis was that periradicular lesions alter sinus structures, but do not demonstrate bacteria. Study design: Blocks including maxillary sinus and associated teeth were obtained from cadavers and radiographed. Those demonstrating periradicular pathosis were the experimental group. Blocks without pathoses or periodontal defects, as viewed radiographically and grossly, were controls. Specimens were decalcified and embedded; step serial sections (0.5 ram), inclusive of apices, periradicular tissues, and sinus floor were stained with H+E and Brown and Brenn. Sections were evaluated with light microscopy, and a descriptive analysis performed. Results: Gross examination showed some lesions to be visible on the sinus floor. Histologically, lesions in close proximity to the sinus showed a variety of changes, but often had bone interposed between lesions and the sinus membrane, which was usually uninflamed. Bacteria were confined to the canal space. Lesions demonstrated accumulations of neutrophils, lymphocytes, and evidence of epithelial proliferation. Conclusions: The maxillary periradicular lesions examined did not generally alter structures of the sinus or demonstrate the presence of bacteria.

Comparison of radiation exposure rates necessary to produce computerized digital images and conventional radiographs. K. Foroughi*, N. Mastromihalis*, A. Goren, G. Bruder, T. Button, W. Moore, S. Friedman SUNY at Stony Brook

This study was designed to compare the radiation exposure essential to produce a Computer Dental Radiography (CDR) image with that of a conventional Kodak Class D and E films. An eleven-step aluminum wedge was used to expose both films and digital sensors. Four digital Schick sensors and conventional Kodak D and E films were exposed using four x-ray units; three (Gendex GX-770) units with factory settings at 70kVp and 7mA and one (MDT Castle Model HDX) preset at 65kVp and 7mA. The exposures for each group ranged from 3 to 24 pulses. All radiographic films were processed manually using Time- temperature technique. The film images were scanned using an ultrascan XC densitometer to obtain density tracings. Tracings of the scans were used to determine what exposures yielded similar densities. The D and E films with similar densities were saved for analysis on 3.5" high-density diskettes, without any contrast changes. The four sets of radiographs from the x-ray units were then imported into their corresponding Schick digital system where histograms were created. These were matched to compare and calculate the differences in exposure times for digital images and conventional films. This study confirms that Computer Dental Radiography (CDR) images reduce radiation exposure amounts by 53.1%-58.7% (average 55%) when compared to Class D (Ultraspeed) film and from 42.5-50.3% (average 45%) in comparison to Class E (Ektaspeed Plus) film.

The accuracy of RooIZX apex locator in the presence of gutta-percha solvents. A Hartoonian*, and AK Mickel, Case Western Reserve University.

The purpose of the present study was to determine the accuracy of the electronic apex locator Root ZX in the presence of most commonly used gutta-percha solvents chloroform and xylene. The goal of endodontic retreatment is to access the root canal system by rotary, hand instruments and solvents in order to eliminate the microorganisms, disinfect the canal(s) and re- obturate three dimensionally. Accurate location of apical constriction is critical in this process and plays an important role in the outcome of retreatment. Many studies have shown that overfilling reduces the success rate of retreatment. Ninety extracted single canal maxillary and mandibular teeth were selected. The actual location of the apical constrictions was determined by using a Zeiss stereomicroscope. Teeth were divided into two group of 45 teeth each and mounted in an in vitro model. Root ZX was used to determine the apical constrictions and working lengths. Instrumentation was completed using the electronic measurements. Canals were then obturated with gutta-percha and Kerr EWT sealer. After 24 hours the root canals were retreated using chloroform in group A and xylene in group B. Root canals were remeasured while they were filled with a mixture of dissolved gutta-perch and solvent. The results showed that the anex locator measured the root canals an average of 0.20 mm longer in the presence of xylene; this difference was found to be statistically sianificant (n=0.0001).