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Yes, we can better treat some cases with these new instruments, and there are those cases where surgery is indicated. We should, however, still try to treat all cases nonsurgically if possible. Be patient, don't be so quick to go to surgery!

Abstracted by Keith D. Sonntag, DDS, Graduate Endodontics, University of North Carolina School of Dentistry, Chapel Hill, N.C.

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Scientific Session IV Endodontic Microleakage Panel Ronald W. Anderson, DDS, MS Kenneth L. Zakariasen, DDS, MS, PhD Larz Spangberg, DDS, PhD Melvin Goldman, DDS William P. Saunders, PhD, BDS Paul R. Wesselink, DDS

Six speakers with considerable experience in this area reviewed in detail the past and present status of microleakage research, its strengths and shortcomings, and which directions microleakage research may take into the future. Many techniques for measuring mi- croleakage have been and are still being utilized. Examples are the fluid filtration and electro-chemical methods, linear dye penetration methods with both cleared teeth and longitudinally split teeth, volumetric dye recovery methods and radio isotope methods for measuring linear leakage. The case was made by several speakers that vacuum systems should be uti- lized to evacuate residual air and that dentinal tubules can be pathways for significant microleakage.

It is evident that, historically, much of the microleak- age research in endodontics centered on apical mi- croleakage. However, more recent research has placed considerable emphasis on the importance of coronal microleakage and has shown that such leakage can be substantial, potentially leading to reinfection of the root canal and the periapical area. It was clear from the presentations that the complete significance of coronal microleakage, apical microleakage and their interactions is not fully known at this time.

It is equally clear that the clinical relevance of invitro microleakage research is not known. It appeared to be the consensus in this session that microleakage research must be much better correlated with clinical outcomes and that the various invitro methods for studying microleakage can give widely differing results. This session indicated that, while much research has been accomplished in the area of endodontic microleakage, considerably more research is necessary in new directions and of increasingly sophisticated science.

Abstracted by Kenneth L. Zakariasen, DDS, MS, PhD, Dean, Marquette University School of Dentistry, Milwaukee

Scientific Session V Historical and Contemporary Perspectives on Root-end Filling Materials Mahmoud Torabinejad, DMD, MSD

Root canal therapy is needed for two main reasons: pulpal inflammation secondary to trauma and infection secondary to caries. In either case the treatment of choice is conventional root canal treatment. However, at times, lesions persist or even develop after con- ventional root canal therapy. Often the reason for failure is obvious, on other occasions it is not. In either case, the treatment of choice for a failing root canal therapy is retreatment. If posts are present, removal of the post is indicated, followed by conventional retreatment. How- ever, even with the most conservative of approaches to root canal therapy, root end surgery is sometimes ne- cessary for removal of a continued source of infection when a root canal cannot be instrumented and obturated fully. The standard techniques for apical surgery are well known and fully covered in other texts. Farrah described the apicoectomy in t756 as a radical treatment, and perhaps before anesthetic it was. Today, however, it is just another way to save teeth. The reasons for carrying out apical surgery are to inspect the root for cracks and defects, to remove uncleaned portions of the root and to create an apical seal. Even if surgery is thought to be inevitable, retreatment should always be attempted, as surgical success is always improved if carried out in conjunction with retreatment.

Today the apicoectomy and osteotomy are carried out with a fissure bur. For root end cleaning and shap- ing, an apical ultrasonic tip is employed. Despite the modern technology used in the cleaning phase, we still only have inadequate root end filling materials available: gutta percha, amalgam, Super EBA, composit, glass ionomer cements, IRM and cavit have all been used.

Ideally a root end filling material should have good sealing ability and be biocompatible, antibacterial, stable, easy to use, radio-opaque and non-discoloring of the tooth. At present, the two most widely used root end materials both have their problems: amalgam leaks, corrodes (releasing heavy metal ions), is moisture sen- sitive, stains the tooth and leaves a scatter radio- graphically, being difficult to remove for bone. ZOE- based cements (IRM and Super EBA) are moisture sensitive, irritant, soluble and difficult to handle.

Given these problems, in cooperation with a chemist, a material was produced that is a cross between a glass ionomer cement and concrete. It is a mineral trioxide aggregate (MTA) which is hydrophilic, has a compressive strength greater than amalgam, requires approximately four hours to set and, although radiolucent, can be made opaque by adding BaSO 4.

Given the multiple types of dye penetration studies 432

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and the problems associated with all of them, a three dimensional leakage study was carried out comparing amalgam, Super EBA and MTA using a fluorescent dye and confocal microscopy. The results show amalgam and Super EBA both leak through to the underlying gutta percha (4mm), as has been shown previously, but the MTA only showed leakage four times out of ten and, in each of these cases, it leaked less than 1 mm. Marginal adaptation was examined using Scanning Electron Microscopy showing that amalgam has a gap of 32~m, which is reduced to 19t~m when a varnish is used. Super EBA has a 10~.m gap, MTA has a gap of 2.8~m. From the ortho grade direction, which has been shown to be the reason for RCT failure, a novel approach to test for microleakage has been used. A tooth is prepared with an apicoectomy and retro-fill with one of the test materials such that bacteria can be introduced into the coronal aspect of the tooth and, if leakage occurs, media that the apex is suspended in will become contaminated. The apparatus is very technique sensitive, but initial results show that MTA behaves somewhat better than either amalgam or Su per EBA. Two types of in vitro cytotoxicity test have been carried out to date: agarose gel overlay inhibition and ~lCr release lysis testing. In both tests MTA performed considerably better than either amalgam or Super EBA. No in vivotests have yet been carried out. Anti-bacterial testing has shown that while, surprisingly, neither Super EBA nor amalgam had any antibacterial activity. MTA was active against all test organisms but Streptococcus Faecalis. Solubility and moisture sensitivity tests are incomplete, but MTA seems to compare favorably with amalgam and even seems to leak less after mixing in the presence of either saline or blood; however, the results are inconclusive at present. In clinical usage it is very easy to handle both while mixing and condensing. Histology after 4 months of healing have shown cementum bridge formation over the MTA retrograde filling. Although no long term follow- up studies have been carried out, several cases have been followed for at least a year showing good radiographic healing.

In summary, although MT aggregate is not the ideal material, it shows initial promise and warrants further testing. However, the search for other materials and techniques needs to continue.

Abstracted by Julian Moiseiwitsch, DDS, Graduate Endodontics, University of North Carolina School of Dentistry, Chapel Hill, N.C.

Scientific Session VI Management of Fascial Space Infections of Odontogenic Origin Jeffrey W. Hutter, DMD

This session reviewed principles involved in the assessment and treatment of a patient with invasive

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odontogenic infection of the fascial planes. Of paramount importance in a case such as this is the identification of immediate, life-threatening signs that necessitate a referral. Examples of these signs include respiratory/ swallowing difficulty and CNS involvement. Differences between the bacterial species responsible for an acute and chronic infection were also discussed because the antibiotic regimen prescribed is dependent upon the stage of infection. A thorough examination and evaluation must be undertaken to arrive at an initial diagnosis. This is achieved by collecting historical data, clinical data and laboratory data.

Historical data may be broken down into two cate- gories: general factors and specific factors. General factors include age, alcohol/drug abuse, psychological state, family/social status and nutrition. Specific factors include pre-existing disease states, medications, aller- gies, antibiotic therapy and radiation treatment.

Clinical data is obtained by assessing the patient's physical appearance, monitoring vital signs and per- forming a dental examination. Certain signs are indicative of the extent of the spread of infection, such as ex- amination of the lymph nodes. The location of the lym- phadenopathy may provide a clue as to the source of infection. Systemic involvement may manifest itself through symptoms such as dehydration or toxemia, which result in the patient's inability to function.

Laboratory data includes culture and sensitivity of a specimen. General principles of anaerobic specimen collection and transportation media were discussed.

After establishing the etiology of the infection, the next phase of treatment is eradication of the source through incision and drainage, possible root canal treatment, antibiotic therapy and supportive treatment.

The seminar ended with a discussion of the indica- tions, rationale and selection of antibiotics, concentrating on penicillin, penicillin/metronidazole and clindamycin.

Abstracted by C.A. Koenig, DDS, Graduate Endo- dontics, Baylor College of Dentistry, Dallas, Tex.

Scientific Session VII HIV Infection: Patient Identification, Diagnosis and Management T.L. Green, DMD, MS, MEd

This session highlighted the recognition and man- agement of the HIV infected patient. A brief review of the epidemiology was presented. HIV infection is here to stay with estimates of 30 to 110 million cases world- wide expected by the year 2000. HIV infection repre- sents a spectrum of disease exhibiting different stages. Of importance is the fact that these patients are infec- tious from the time of infection until they die. Methods of transmission were discussed with emphasis on how this may impact on dental care. Recognition of HIV infected patients was presented covering evaluation of patients'

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