ABSTRACTS OF PAPERS SUBMITTED TO THE AMERICAN ASSOCIATION OF ENDODONTISTS

45th Annual Session April 20-24, 1988 Anaheim Marriott

Anaheim, California

Due to the enthusiasm and interest of our members in sharing their findings with others, a large number of abstracts were received for oral presentation at our 45th Annual Session in Anaheim. In order to select the "cream of the crop" and to ensure impartiality in their selections, the abstracts were given numerical codes and were sent to all members of the Committee on Research and Scientific Affairs of our Association. The abstracts were graded based on their scientific merits, and the results were tabulated anonymously. The top 20 abstracts from each category (regular and graduate) were selected and categorized according to the topic subjects. Despite adding an additional session to our research seminars, some abstracts were turned down due to lack of space for oral presentations. These researchers were informed and were asked to consider submitting their abstracts for presentation at the table and poster clinics.

I would like to thank all of the people who submitted their abstracts as well as the members of the Committee on Research and Scientific Affairs for reviewing these abstracts.

Mahmoud Torabinejad, DMD, MSD Chairman, Committee on Research and Scientific Affairs

(Please bring your copy of the Journal with you to the meeting as the abstracts will not appear in the program.)

1

HUMAN PULPAL RESPONSES FOLLOWING TREATMENT WITH THE CARIDEX SYSTEM. D.S. Brunell*, H. Schilder, and A. Bloom; Boston University.

The objective of this study was to histologically evaluate the responses of the human pulp following caries removal by the Caridex system under clinical conditions. Fifteen human teeth previously scheduled to be extracted and possessing a carious lesion involving only enamel and dentin were util ized in this investigation. Vi ta l i ty of the pulp was confirmed through a series of diagnostic tests. Following caries removal by the Caridex system, a temporary ZOE restoration was placed in the cavity preparation. The teeth were extracted either 7 days or 30 days post-operatively, and then histologically prepared and examined. Histological evaluation of the dental pulps revealed 6 specimens which demonstrated a possible hyperemic response; 2 specimens showed a generalized inflammatory response; I specimen displayed a localized inflammatory response; and 6 specimens revealed normal pulp tissue. Analysis of the histologic sections also revealed 6 of the 15 specimens showed evidence of dental caries remaining on the surface of the cavity preparation and extending into the dentlnal tubules. Additionally, caries removal by the Caridex system was found to be a time consuming process. Actual caries removal time ranged from 9 to 22 minutes, with an average caries removal treatment phase of 15.5 minutes.

2

FLOW CYTO~TRIC ANALYSIS OF ANTIGEN PRESENTING CELLS IN THE DENTAL PULP. M. Hunt*; University of North Carolina.

Dendritic cells and macrophages, expressing Class I I antigens on their surface, have been indentifled by immunohistochemical techniques in the normal human dental pulp (Jontell et a l . , 1986). The expression of Class I I antigens is indicative of the abi l i ty for these pulpal cells to present a foreign antigen to T-lymphocytes, thus

192

in i t iat ing the immune response. The present research describes the use of immunofluorescence and flew cytometry in classifying, separating and enumerating these antigen presenting cells. This information is vital for future studies on the role of Class I I antigen expressing cells in the immune response of the pulp. The specific aim of this study is to construct a model permitting co~arison between the normal and the inflamed pulp. Rat maxillary incisors were extracted, cracked open and the pulps were dissected out. The pulps were minced with scissors and digested with collagenase in a ro l ler tube apparatus. The cell suspension was incubated with red flourescent beads to separate phagocytic from non-phagocytic cells. Class I I antigen-expressing cells were labeled by using meuse anti-rat Class I I antigen-antibodies and rabbit anti-mouse IgG (Fab2 fragment) conjugated to F.I.T.C. Flew cytometry was used to analyze the frequency and quantity of cells expressing Class I I antigen and to determine their phagocytic capacity.

This study demonstrated that our research design , u t i l i z in 9 flow cytometr~, is an effective model for future study of the defense mechanism in the dental pulp.

Supported by BRSG RR05553-26

3

I~UNOHISTOCHEMICAL ANALYSIS OF IMMUNOCOMPETENT CELLS IN PULPS OF CARIOUS TEETH. A. Abdullah*, M. Jontell, and G. Bergenholtz; University of North Carolina.

Recent research ut i l iz ing immunohistochemical techniques has demonstrated that the normal dental pulp is equipped with a variety of immunocompetent (Ic) cells (Jontell et a l . , 1987). The aim of this study was to determine the type and frequency of various Ic cells in pulps of teeth with different depths of carious involvement. Teeth without carious lesions, teeth with caries into the dentin, and teeth with carious pulp exposures were obtained from individuals 15 to 40 years of age. Pulp tissue (5 from each group) were obtained from extracted teeth and teeth undergoing root canal

...continued

Vol. 14, No. 4, April 1988

#~erapY- Frozen and acetone fixed pulp tissue sections were ~;epared and incubated with monoclonal antibodies to the ~011owing cell types: al l T cel ls , B cel ls, macrophages, and r expressing Class II antigen. Immunohistochemical reactions were examined at the l igh t microscopic level. pulps of normal teeth exhibited an even but sparse d|stribution of various Ic cel ls, except B cells, throughout the pulp. Pulps from teeth with dentinal caries presented with an increased frequency of a l l Ic cells. T helper cel ls dominated over T suppressor cel ls and B cells were not Observed. Teeth with carious exposures showed significant |ncrease in al l Ic cells including a sparse distribution of B cells in sites near the pulp exposure. Results of this study |ndicate an association of the severity Of carious ~vvement. with increased_ HLA-DR expression and the number ~ r r -ce l l s present. ~ p p o r t e d by BRSG #5-0-101-4375-3401g-2611

4

ANESTHETIC EFFICACY OF LIDOCAINE AND EPINEPHRINE IN HUMAN IAN BLOCK. M. Wall*, A. Reader, M. Beck and W. Meyers; The Ohio State University.

The purpose of this study was to compare, with the use of the electric pulp tester, the anesthetic efficacy of 1.8 ml of 2% lidocaine with 1:100,000 epinephrine to 3.6 ml of 2% lidocaine with 1:50,000 epinephrine and 1.8 ml of 2% lidocaine with 1:50,000 epinephrine in human infer ior alveolar nerve block.

Thirty subjects randomly received in fer ior alveolar nerve block injections of each solution at three successive appointments. The experimental teeth studied were the f i r s t molar, f i r s t premolar and latera l incisors. The teeth were tested with an Analytic Technology pulp tester at various time intervals up to 59 minutes. Complete anesthesia was defined as an 80/80 reading with the pulp tester.

No significant differences were found between the solutions as to the onset or incidence of profound pulpal inesthesia. Successful puIpal anesthesia (attainin 9 an 80/80 readin 9 within 16 minutes and continuously sustaining ~his reading for the 59 minutes) occurred in: 43% of the molars, 60% of the ~remolars and 37% of the lateral incisors with 1.8 ml of ~% hdecaine with l:lou,uou epinephrine; 37% of the molars, 57% of the premolars and 47% of the lateral incisors with 3.b ml of Z% lidocaine With l:SO,UO0 ~pinephrine; 33% of the molars, 50% of the premolars and 37% of the lateral incisors with 1.8 ml of 2% lidocaine with !:50,000 epinephrine.

This study was supported by The Ohio Association of ~ndodontists, J. David B r i l l i an t Memorial Fund.

5

ANESTHETIC EFFICACY OF LIDOCAINE & BUPIVACAINE IN HUMAN MAXILLARY INFILTRATIONS. R. Gross*, A. Reader, M. Beck and W. Meyers; The Ohio State University.

The purpose of this study was to con~)are, with the use of the electric pulp tester, the anesthetic efficacy of 1.8 ml of Z% lidocaine with 1:I00,000 epinephrine and 1.8 ml of 0.5% bupivacaine with 1:200,000 epinephrine in human maxillary in f i l t ra t ion injections.

Sixty-f ive subjects randomly received maxillary in f i l t ra t ion injections of each solution at two successive appointments. The experimental teeth studied were the lateral incisors and f i r s t molars. The teeth were tested With an Analytic Technology pulp tester at various time intervals up to Z hours. Complete anesthesia was defined as an 80/80 reading with the pulp tester.

Successful pulpal anesthesia (attaining an 80/80 readin~ ~thin 7 minutes and continuously sustain~n 9 this reading o~-r the 60 minutes) occurred in: Z5% of the lateral incisors ~ 3 3 % of the molars with Z% lidocaine with i:IOO,O00

and in 6% of the lateral incisors and Z4% of molars with 0.5% bupivacaine. The duration of

an~re~thesia was signif icantly better, in the lateral ~ i s o r s , with 2% ]idocaine with I:100,000 epinephrine when co.o~oared to 0.5% bupivacaine with I:ZO0,OOU epinephrine.

This study was supported by The Ohio Association of Endodontists, J. David B r i l l l an t Memorial Fund.

6

AAE Abstracts of Papers 193

HISTOLOGIC STUDY OF HEALING ABILITY OF HORIZONTAL ROOT FRACTURES IN MONKEYS. J.A. Herweijer*, L.K. Bakland, and M. Torabinejad; Loma Linda University.

Traumatic injur ies can cause horizontal root fractures involving periodontal ligament, cementum, dentin, and pulp. Histologic studies on the effects of trauma on these tissues and their potential for healing are lacking. The purpose of this study was to investigate the repair process in experimentally induced horizontal root fractures in Vervet monkeys.

Six teeth in three monkeys were surgically fractured at mid-root levels and splinted for 12 weeks. Six months postoperatively, c l in ical examinations showed that f ive root fractures had apparently healed successfully, while one root fracture had developed a draining f is tu la . Block sections of the teeth with their surrounding structures were fixed, decalcified, and sectioned for histologic examination. Depending on the proximity of the root segments, the fracture sites were f i l l e d with either soft or hard tissues. Despite a signif icant reduction in pulpal size, this tissue remained v i ta l and uninflamed in cases which had healed successfully.

The results of this study indicate that intra-alveolar horizontal root fractures in monkeys have a potential to heal and that the pulps appear to survive this type of trauma. ~ o r t e d in part by a Grant-ln-Aid from the American Association of Endodontists Endowment and Memorial Foundation.

7

ENDODONTIC VERSUS RESTORATIVE PROCEDURES: WHICH IS THE MAJOR FACTOR WEAKENING THE TOOTH? E.S. Reeh*, W.H. Douglas, and H.H. Messer; University of Minnesota.

Endodontically treated teeth are thought to be more susceptible to fracture as a result of endodontic procedures. This study was designed to compare the contributions of endodontic versus restorative procedures on the loss of strength, using occlusal loading on extracted teeth. Caries-free unrestored, maxillary second bicuspids were cleaned and stored in water plus thymel. An encapsulated strain gauge was bonded on enamel just above the cemento-enamel junction on both the buccal and lingual surfaces using an acid etch technique and enamel bond resin. The teeth were mounted in nylon rings with orthodontic resin, leaving 2 mmof root surface exposed. Under load control, each tooth was loaded at a rate of 37 N/sec for three seconds and unloaded at the same rate in an MTS closed-loop servo-hydraulic system, to measure stiffness. (Morin 1984) A stress-strain curve was generated from each gauge pr ior to alteration of the tooth and after each procedure performed on the tooth. Cuspal stiffness, as a measure of tooth strength, was evaluated on one of two series of sequentially performed procedures: I. a) unaltered tooth; b) access preparation; c) instrumentation; d) obturation; e) MOO cavity preparation OR I f . a) unaltered tooth; b) occlusal cavity preparation; c) two surface cavity preparation; d) MOD cavity preparation; e) access; f) instrumentation; g) obturation. Results on 26 teeth indicate that the effects of endodontic procedures have only a small effect on the tooth reducin~ the relat ive stiffness by 6.7%. This was less than that of an ecclusal cavity preparation IIB.~%I. By tar the largest losses in st i f fness were related to the loss of marginal ridge Integrity. MOD c_avlty preparation resulted in an average of a 6Z% loss in ~elative cuspal stiffness. Endodontic procedures do not weaken teeth with intact marginal ridges.

8

EFFECTS OF ENDO ACCESS PREPARATION UPON EXISTING INCISOR CROWN RETENTION. A.F. McMuIlen I l l * , Y.T. Himel and N.K. Sarkar; Louisiana State University.

The need to cut endodontic access preparation through ...con~nued

194 AAE Abstracts of Papers

existing crowns is a problem facing many dentists. This vibratory and mechanical deformation of the crown and i ts cement seal may alter retention. This study examines the effect of endodontlc access preparation on the retention of an existing PFM crown.

Ten extracted human maxillary central incisors were used in the study. Conventional PFM crown preparations were cut on the teeth. Crowns were fabricated and cemented with ZnPo4 cement and allowed to set. Tensile forces were measured with an Instron machine and recorded. After the f i r s t "pu1]" the crowns were treated with 30% HN03 in an ultrasonic cleaner to remove all the residual cement. (This was proven in a p i lo t study to restore retention to a level not significantly different from the original level.) Next, the crowns were recemented with ZnPo4 cement, allowed to set, and access preparation cut through the crown. The Instron machine was again used to measure retention.

Results from the testing showed an average of 60.7% reduction in crown retention. A student's "t" test was conducted to I l lustrate that this Is a very significant difference from the O.Ol level. Based on these observations, i t Is concluded that endodontic access preparation through existing PFM access in a maxillary central incisor siqnificantly decreases retention in vitro.

9 IN VIVO EFFICACY OF A STEP-BACK VERSUS A STEP-BACK/ULTRASONIC TECHNIQUE. J. Haidet*, A. Reader, M. Beck and W. Meyers; The Ohlo State University.

The purpose of this in rive study was to histologically compare the effect of the step-back preparation versus a step-back/ultrasound preparation on tissue removal from the mesial root canals of v i ta l , human mandibular molars.

Group I consisted of 15 teeth prepared with a step-back technique using intermittent irr igation of 5.Z5~ sodium hypochlorlte. Group 2 consisted of Z3 teeth prepared with a step-back technique, as in group 1, followed by 3 minutes of ultrasonic instrumentation (Cavi-endo) using 5.25% sodium hypochlorlte (30 cc/min). Group 3 consisted of 21 teeth which were uninstrumented and served as controls. Following extraction and histologic preparation, the I - and 3-mm levels were evaluated for percentage of tissue removal within each canal and isthmus using a compensating polar planimeter.

At the l-mm level, statistical analysis indicated that the step-back/ultrasonic technique was superior to the step-back technique in canal (99.6% vs 88%) and isthmus (86% vs 10%) cleanliness. At the 3-mm level, there were no stat ist ical differences in canal or isthmus cleanliness between the two techniques.

This study was supported by The Ohio Association of Endodontists, J. David Br i l l iant Memorial Fund.

10 COMPARISON OF FLEX-R FILES AND K-FILES IN CURVED CANALS. A.O. Seplc*, E.A. Pantera, Jr . , E.J. Neaverth and R.W. Anderson; Medical College of Georgia.

This investigation was designed to measure and compare the amount of root canal alteration resulting from balanced force (BF) instrumentation with Flex-R f i les and step-back (SB) technique using K type f i les during cleaning and shaping procedures.

A double exposure radiographic technique providing fixed source-object-film distance and position, was utilized in which pre and post instrumentation radiographs were generated on a single film, thereby permitting each canal to serve as i ts own control. The mesio-buccal roots from 80 extracted human teeth with curvatures ranging from 300 to 730 (Schneider) were examined from clinical and proximal radiographic views by computer digit ization following experimental instrumentation. Teeth were paired according to the degree of curvature and prepared wlth a largest f i l e to working length of #30 (SB) or #35 (BF).

The BF technique produced a mean canal alteration of 0.050 mm and 0.049 mm as measured on the clinlcal and proximal radiographic views respectively. In those canals prepared using the SB technique, the mean canal alteration was O.Z32mm and 0.141 mm as measured from the clinical and proximal radiographic views respectively.

Journal of Endodonticl

Analysis of the clinical views and proximal views indicated significantly less apical transportation with the use of the balanced force technique when compared to a step-back technique.

11

THE EFFECTIVENESS OF THE CANAL FINDER SYSTEM: A SCANNING ELECTRON MICROSCOPIC INVESTIGATION. H. EI-Tagourl*, M. Czonstkowsky, F. Holstein, N. Piesco, and A.E. Michanowicz; University of Pittsburgh.

A new system (Canal Finder System) has been introduced to instrument and obturate the root canal system. The effectiveness of this new system in instrumenting and cleaning the root canal was investigated by means of the Scanning Electron Microscope and compared to two other instrumentation techniques.

Thirty freshly extracted single rooted teeth were included in this study. The teeth were stored in sodium hypochlerlte solution for 24 hours to remove any debris. The crowns were removed to faci l i tate instrumentation, and the teeth were divided into three groups. In group l , teeth were instrumented by conventional f i l l i ng with step-back preparation; in group 2, teeth were instrumented by Roane technique; and In group 3, teeth were instrumented by the Canal Finder System. The teeth were irrigated with sodium hypochlorlte solution during and after instrumentation. Five teeth of each group received a final irr igation with 17% EDTA. The teeth were sectioned, prepared, and examined under the SEM.

The results show that all three techniques were able to remove the pulp tissue, and the smear layer was present in all groups that were irrigated with sodium hypochlorite only. When the canals were irrigated ut i l iz ing EDTA as a final irrigation, the amount of the smear layer was significantly decreased In the coronal and middle third of the root. However, the smear layer was present In the apical third re(jardless of the technique and irr igation so lu t lon used.

12 CLINICAL INCIDENCE OF CANAL LEDGING WIIH A NEW ENDODONTIC FILE. D.J. McKendry, K.V. Krell and L.L. McKendry*; University of Iowa.

Deviation of f i les from the original root canal curvature during instrumentation is an undesirable event. When Instrument deviation is severe, ledging of the canal wall occurs. Inadequate debridement of the original canal apical to the ledge, and obturation short of optimal length are eminent once the canal has been ledged. Either may adversely influence prognosis. Recent research has demonstrated, in the laboratory, that modifications in f i le design reduced the extent of f i l e deviation from original canal curvature (Powell, Simon and Maze, 1986).

The purpose of this clinical investigation was to c ~ a r e the incidence of canal ledging between the newly designed flex-Rtm f i l e (the Union Broach Co., Emigsville, PA) and the K-flex tm f i l e (SYBRON/Kerr Co., Romulus, MI). All canal instrumentation was performed by dental students, ut i l iz ing a step-back f i l i ng technique, under close supervision in the undergraduate endodontlc cl inic. To control for differences in operator abi l i ty throughout the academic year, one group of students performed endodontic instrumentation using K-flex f i les prior to switching to flex-R f i les for the second group of students. For a third group of students, K-flex f i les were returned to the clinic to provide a comparison of operator abi l i ty with group I . A total of 12/ completed molar cases, providing 394 canals, were coded for blinded ~ a t i o n . Two endodontists independently evaluated radiographs to determine the presence or absence of a ledge. A ledge was determined to exlstwhen: l ) both the master gutta percha cone and the final obturatlon ~ re short of the predetermined working length and, 2) the aplcal terminus of the obturation devlated from the original canal curvature. Canals were categorized as to severity of original canal curvature using Schneider's technique. Additionally, the largest f i l e size used In apical preparation was obtained from the treatment

...continued

VoI. 14, No. 4, April1988

record. Results indicate a 31% incidence of canal ledglng for al l molars evaluated. The K-flex f i l e ledged 37% of ~anals c~ared to ZI% ledglng observed with the flex-R r Incidence of canal ledging was determined to be ~|gnlficantly di f ferent (p .01) using Chl square test. There was.no slgnlflcant difference between groups I and I I I which born used ~-f lex f i les . Ut l l iz ln~ a step-back f i l i n q technique, the flex-R f l l e created signlf icantly fewer e d ~ d canals than the K-flex f i l e .

13 DE~TIN COLLAGEN CROSS-LINKS OF ROOT-FILLED AND NORMAL TEETH. E. Rivera', M. Yamauchi, G. Chandler and G. Bergenholtz; University of North Carolina .

I t is a cl inical impression that root - f i l led teeth are weaker and more b r i t t l e than teeth with vi tal pulps. This has been attributed to a decrease in the moisture content ind/or to physico-mechanical loss of tooth structure. Since collagen covalent intermolecular crosslinks provide the dentin matrix with s tab i l i ty and tensile strength, changes in collagen cross-llnking may relate to the brittleness of root - f i l led teeth. L i t t l e research has been performed in this area.

The main objective of this research was to determine i f any structural changes of collagen occur after endodontic treatment. In this study, ~ focused on the quantification of dentin collagen cross-llnks in root - f i l led and normal extracted human teeth. Human dentin collagen was prepared (Mechanic 1974), reduced with standardized NaB3H4, hydrolyzed, and subjected to cross-llnk analysis (Yamauchi 1986). Preliminary results indicate that there are more immature {reducible) and less mature (non-reducible) cross-links in roo t - f i l l ed teeth. This change in collagen cross-linking may refect one aspect of the brittleness of Toot-f l l led teeth.

14

RESPONSE OF PE~IAPICAL TISSUES TO TOPICAL CORTICOSTEROID AFTER DELIBERATE OVERINSTRUMENTATION. E. Stec*, H. Messer, M. EIDeeb and R. Edmunds; University of Minnesota.

The use of topical corticosteroids is being increasingly advocated in the management of acute apical periodontitis following overinstrumentation. This study was designed to evaluate histologically the effects of a steroid preparation (Aristocort, triameinolone O.l%), af ter deliberate overinstrumen- tation with a @40 f i l e 2mm beyond the apex on the periapical tissue of dogs. A total of IZO roots (4 maxillary and 6 mandibular premolars, and 4 incisors in each o6 5 dogs) were used. In premolars steroid was used in one root and the other served as control {saline). The incisors were used as steroid or control {saline). In each dog, B roots were treated at each of Z, 4, and 11 days; yielding 20 steroid and 20 control roots for each time period. Block sections were prepared. Semiserial 5u sections were cut and stained with hematoxylin and eosin for evaluation. The severity of inflammation was graded (none, mild, moderate, severe) by an independent oral pathologist.

A wide range of acute inflammatory reactions were demonstrated in both the steroid and control groups at al l t i ~ periods examined. In some instances, inflammation was evident at a distance from the site of overinstrumentation, l'ncludin 9 a high percentage of cases with inflammation in the mandibular canal. Results of this study indicate that the application of a steroid preparation (Aristocort 0.1%) did not signif icantly i n f luence t~e severity or duration of the inflammatory response of dog periapical tissues surroundinq deliberately overinstrumented roots.

15

AAE Abstracts of Papers 195

BIOCOMPATIBILITY OF GLASS IONOMER-SILVER CEMENT IN RAT CONNECTIVE TISSUE. R. Blackman*, M. Gross and S. Seltzer; Temple University.

A number of materials have been proposed for apical re t ro f i l l i ng during periapical surgery. The purpose of this study was to evaluate the Inflammatory response to, and repair potential of, a glass ionomer-silver cement implanted in the hard and the soft connective tissues of rats. Pellets of the glass ionomer-silver cement and zinc oxide- eugenol were implanted into the soft tissues and bones of 30 rats. Following experimental periods of 14, 30, and 80 days, the animals were sacrificed and tissue sections were prepared and examined. The responses to each of the materials at 30 days consisted of mild inflammation. No severe inflammatory responses were noted in any of the groups. By 80 days, although mild inflammation persisted, the materials appeared to be well tolerated. Bone apposition occured tn the glass ionomer-silver cement group; the zinc oxide-eugenol group produced f ibrosis.

I t would appear from the findings of this study that both zinc oxide-eupenol and glass ionomer- si lver cements are not benign but are relat ively biocompaEible and would be useful for endodontic r e t r o f i l l i n 9 procedures.

This "study was funded by ESPE, Germany.

16

THE ANTIMICROBIAL EFFECT OF CALCIUM HYDROXIDE IN ROOT CANALS OF EXTRACTED TEETH. K.G. Stuart*, C.W. Newton, C.H. Mi l ler and C.E. Brown Jr.; Indiana University.

The purpose of this study was to evaluate the antimicrobial effectiveness of calcium hydroxide in-v i t ro as an intracanal medication. An inoculum of Streptococcus mutans, Actinomyces viscosus, and Bacteroides 9ingivalis, or f rap i l i s was exposed to CMCP, formocresol, calcium hydroxide or Pulpdent for one hour in canals of extracted adult human teeth.

Ninety teeth were divided into f ive groups. One group of TO teeth had no inoculum or medicament. The remaining four groups had 20 teeth each, IO controls and TO test teeth. Fifteen microllters of Inoculum was added and the access was sealed without and with a medication. The teeth were opened, f i led , and rinsed with l.O ml of B-RTF. Serial dilutions were plated for a quantitative analyses. The results indicated that calcium hydroxide, PuIpdent an-d- formocresol are very effective antimicrobial agents after one hour against the three microorganisms.

17

PERMEABILITY OF APICAL BARRIERS W.J. Beeler*, and F. J. Marshall; Oregon Health Sciences University.

The purpose of this work was to measure the hydraulic permeability of root canal apical barriers In-vi t ro. These barriers were placed in 30 extracted human ~et-~--a~ter the pulp tissue was removed and the apical canals were enlarged in a standard way using endodontic f i les . Barriers one millimeter thick were placed just inside the apical opening using either autogenous dentin chips, calcium hydroxide powder, or durapatite particles. The prepared teeth were placed in a special chamber which permitted applying known water pressures to the barrier and measuring the resultant flow. Scanning electron micrographs (S.E.M.) were made of selected barriers to evaluate consistency and density.

The standardized canals with the autogenous dentin chip barriers gave a permeability average of O.O01O ul/second/psi at ZO Ibs applied pressure. The permeability of calcium hydroxide barriers averaged O.OOIZ ullsecond/psi. Durapatite part icle barrier permeability averaged O.OZZO ul/second/psi. The S.E.M. photographs showed densities consistent with the measured permeability.

I t was concluded that autopenous dentin chips and calcium hydroxide barriers showed s ta t is t ica l ly significant less permeability than did durapatite barriers (p=O.5) and that a useful technic had been developed for the measurement of hydraulic conductance across a barrier.

196 AAE Abstracts of Papers

18

SEALING ABILITY OF FOUR REVERSE FILLING TECHNIQUES. C. Shaw*, P. Bery, E. Jacobsen and E. Begole; University of I l l i no is at Chicago.

The primary ob~ectlve of endodontic therapy is the restoration of endodontically treated teeth to their proper form and function. The conventional method of treatment is by a non-surgical approach, however this Is not always possible. In some instances treatment requlres a surgical approach to adequately seal the apices of teeth. The present study sought to evaluate some of the ~thods and materials used for that purpose.

The apical seal obtained by four d i f ferent reverse f i l l i ng techniques was examined using 50 human single rooted teeth. The four f i l l i n g techniques were cold burnished gutta-percha, amalgam, amalgam with varnish, and injectable gutta-percha with varnish. The teeth were immersed in methylene blue dye for a period of l week after which they were sectioned and the dye penetration measured using a dissecting microscope. The results showed that there was a stat ist ical difference in leakage between the four experimental groups. Amalgam wlth varnish showed the least amount of leakage however, cold burnished g u t t a - ~ showed the greatest. The study also d e m o n s t r a s those

~ roups in which varnish was used had signif icant ly less eakage than any of the other experimental groups.

19

INFLUENCE OF ENTRAPPED AIR ON LEAKAGE STUDY USING DYE PENETRATION METHOD. Y. Cha, T. Acierno* and L. Spangberg; University of Connecticut.

The endodontic l i terature is abundant with reports of studies of apical leakage. Results of such studies, which are often undertaken using dye leakage methodology, are often conflicting. No clear understanding exists of the re l iab i l i t y of the methods used. Entrapped ai r can inhibi t dye penetration resulting in fai lure to demonstrate the entire void. A new approach to study voids was developed where the air in the void was f i r s t evacuated before the dye was introduced. This method was compared to the regular technique of passive dye diffusion. Uniformly prepared root canal specimens were obturated with AHZ6. A known and identical void was introduced in each specimen. After sealer was completely set, nail varnish was applied to the entire surface of the specimen except the apical end. Specimens were immersed passively in 2% methylene blue for a week. Other specimens were placed In the vacuum chamber with 35 psi negative pressure. The dye was introduced while the negative pressure was maintained. Leakage was measured stereomicroscopically. Controls with no voids had minimal leakage under both experimental conditions. Passive dye penetration showed incomplete f i l l i n g of known voids, while dye penetration under the negative pressure showed complete f i l l i ng of known voids. Results of this study suggest that entrapped ai r produces art i facts in passive immerslon technique., lhese art i facts render such leakage studies unreliable. . Introduction of dye after evacuation of a i r completely . f i l l s existing voids.

20 MICROLEAKAGE OF RETROGRADE AMALGAMS: IN VITRO STUDY USING ELECTROCHEMICAL TECHNIQUE. W.W. Cox*, J.F. Corcoran, J.M. Powers and R.M. Z i l l lch; University of Michigan.

The study was designed to measure marginal leakage in teeth with di f ferent thicknesses of and types of retrograde amalgam f i l l i ngs . An in vi t ro study, using the electrochemical means of measuring microleakage developed by Jacobsen and yon Fraunhofer, was conducted to determine i f a difference in marginal leakage existed between the type of apical preparation, horizontal cut vs. a 450 beveled cut, depth of retrograde f i l l i n g , 3 mm vs. 5 mm and type of amalgam used, spherical vs mixed, in a retrograde f i l l i ng . Teeth were sectioned coronally, prepared endodontically to a size #80 f i l e and then coated with an impermeable coating (fingernail polish) on all surfaces except the apically sectioned portion. A copper wire was inserted into the

Journal of Endodonties

coronal opening and advanced down the canal to within I mm of the retrograde amalgam f i l l i ng . A solution of I% potassium chloride was used as the electrolyt lc medium. When an electric potential is presented across the tooth through the electrolyt ic medium and the retrograde amalgam to the copper wire inside the tooth, leakage of the electrolyte into the tooth can be measured as a direct increase In electr ic current detected with an ammeter. Using this method, daily fluctuations In marginal leakage was observed with 90 single rooted teeth over a 3U-day period.

Results from this study indicate that teeth with a 5 mm retrograde amalgam f i l l i n g had less leakage then those'teeth with ) mm retrograde amalgams. AlSo, horlzontall~ c u t apices Inolcate less apical leakage tnan 4b ~ oeveled apices.

Supported by the University of Michigan School of Dentistry LeGro Fund.

21

A COOLING DEVICE TO LOWER TEMPERATURE WITHIN THE PULP CHAMBER. H. Goodis*, L. Watanabe and R. Rosenberg; University of California at San Francisco.

The pulp is vulnerable to increased temperature generated during many restorative procedures. Cooling the tooth before such procedures could prevent an increase In intrapulpal temperature and resulting increase in intrapulpal pressure. The device we developed can lower the temperature within the pulp chamber to IO-15oc for 20 min. The device i t se l f consists of interconnected, miniature valves attached by tubing to rubber dam clamp forceps. The tubing permits continuous circulat ion of cooled water via a pump, and the temperature is maintained by circulating the water through an ice bath. To test the device, extracted teeth were sectioned mesiodistally, implanted with temperature probes in the pulp chamber, and reassembled using a cyanoacrylate adhesive. The temperature probes were attached to a flatbed recorder. The test teeth were mounted in a constant temperature water bath maintained at 37oc. The cooling device was positioned to contact occlusal, facial, and lingual surfaces. The cooled water was then circulated, and successfully maintained the temperature within the pulp chamber at 15oc for 20 mln, then at lOOC for 20 min. I t is thought that lowering the temperature within the pulp chamber prior to operative procedures will protect the tissue from the trauma of preparation and restoration. This vemperature range and time interval should adequately protect the pulp from temperature increases believed to be harmful. Studies wil l be continued using the Cynomelagus monkey to explore the use of the device in vivo.

22

RADIATION DOSES ABSORBED BY VARIOUS TISSUES DURING SIMULATED ROOT CANAL THERAPY. M. Torablnejad, R. Danforth*, K. Andrews and C. Chart; Loma Linda Unlver~ity.

Concerns regarding the harmful effects of radiation have been evident since the i n i t i a l use of x-rays for diagnostic imaging. Radiographs are commonly used during endodontic therapy to perform accurate treatment. Many patients are concerned about the nu~er of films sometimes required during treatment and direct data concerning doses during endodontic treatment seem to be lacking.

The purpose of this investigation was to measure radiation doses to di f ferent oragans and regions during simulated endodontic therapy using 70 kVp and 90 kVp exposure techniques and to determine the potential health risks associated with endodontic radiography.

After placing chip dosimeters on selected sites of a human-like x-ray phantom and exposing them to radiation during a simulated endodontic therapy, the amount of absorbed doses by various organs and the potential health risks were determined. The results show that the endodontiC x-ray doses received by the patients are low and potential risks are minimal compared to other radiographic procedures.

The study shows that endodontic x-ray doses are variable L but relatively low to the cr i t ica l organs at risk wVnen compared to biological effect and medlcal therapeutic/diagnostic radiation.

~/ol. 14, No. 4, April 1988

E%PoSURE TIMES AT WHICH DENTAL XERORADIOGRAPHS AND IB~DIOGRAPHS HAVE COMPARABLE OPTICAL DENSITY. J. Alexander Im d J. Andrews*; University of Texas Health Sciences Center at San Antonio.

A xerorad iographic system has been developed fo r imaging dental s t ruc tures which requ i res less rad ia t i on and less exposure time than does convent ional radiography. ~factioners can also maintain a conventional radiography System should the xeroradiography system become inoperative. This study was designed to determine the changes in the exposure time required to produce ~eroradiographs and radiography with comparable image densities.

Xeroradiographs and conventional radiographs were made of I dentulous human cadaver maxilla s t i l l covered with soft tissue. The times of exposure for the xeroradiographs started at 6 Impulses (l Impulse - 1/60 sec) and were increased by increments of 3 impulses through 48 for subsequent images while the radiographs were made using B-speed film and exposure times from 21 through 63 impulses, again at every third reading. The same dental x-ray machine was used as the source of radiation for al l images using 70 kVP and 15 mA. Film/cassette to jaw relationship as well as focal spot to film/cassette distance were standardize. Transmission optical density of the resulting images was determined.

The results showed that radlographs with transmission o~1~cal densities comparable to xeroradiographs were p_[oduc~ ~ r : ~ o s ~ e h ~ i ~ s t ~ p r o x i ~ a t e ~ , 3 times those used f "o~ p " lowe p a t of the range observed. This factor decreased to approximately 1.3 as o p ' ~ e n s l t y increased.

24 MARGINAL LEAKAGE OF BONDED COMPOSITE RESTORATIONS. A. Chohayeb*, Howard University, and N.W. Rupp; ADAHF PRC National Bureau of Standards.

Hypersensitivity and pulpal i r r i ta t ion following the placement of composite restorations has been attributed to marginal leakage. The purpose of this study was to evaluate the effectiveness of bonding agents in preventing microleakage. Two Class V cavities were prepared in the opposite sides of extracted human teeth with the gingival margin below the enamel cementum junction. Two commercial bonding agents (Bondllte and Prisma Universal) were applied to the cavities on one slde of the t ee th , while the two experimental bonding systems were applied to the other. These experimental systems were Ferric Oxalate N-phenyl glyci ne Z-hydroxethyl Methacrylate + Pyromel I i t ic Dianhydride (FNP) and Aluminum Oxalate N-phenylglycine 2-Hydroxethyl Methacryl ate + Pyromel I i t ic Dianhydri de (ANP). Twenty cavities were treated using each of the four bonding systems. The cavities were restored using a light-cured composite, Herculite or Silux. The restored teeth were then thermocycled at 5-55oc for seven days. Microleakage was tested using the silver nitrate technique (scoring 0-4}. The results showed that there were higher mlcroleakage scores at the gingival margins of al l restorations. Herculite, having the thicker consistency, showed more microleakage than the more f luid composite "Silux." The experlmental bondin~ systems FNP and ANP had lower microleakage scores than the commercial systems tested.

25 MICROLEAKAGE OF TEMPORARY RESTORATIONS IN COMPLEX ENDODONTIC ACCESS PREPARATIONS. R.W. Anderson*, B.J. Powell and D.H. Pashley; Medical College of Georgia.

The purpose of thls study was to evaluate the mlcroleakage of three materials used as temporary restorations in teeth with endodontic access preparations and multisurface Cavity preparations. Extracted human incisor, canine and premolar teeth with extensive carious involvement were prepared and restored with either IRM, Cavit, or TERM. Ten teeth were in each group. Microleakage Was measured by a f luid f i l t ra t i on technique Ib minutes

AAE Abstracts of Papers 197

after inserting the restoration. The teeth were then immersed in Rlnger's solution and incubated at 3/oc. Microleakage was again measured after I hour, 24 hours and / days. The teeth were then thermally stressed for bU cycles by placing them alternatively in water baths at 4oc and bboc for Z minutes each. After thermal stress, microleakage was again measured.

The results indicated that Cavit and TERM provided the best seals. IRM restorations demonstrated significantl~ greater microleaka~e after thermal stress. Cavit restorations, while providin~ a 9o6d seal, were deemed to be clinica11~ unacceptable because of extensive defects characterized by cracks, expansion and l i f t i n 9 out of the tooth prepaTation. None of these defects were observed in the IRM and TERM restorations. TERM proved to be the best restorative material of those tested for restoring complex endodontic access preparations.

26 CHROMATIC COMPARISON OF THREE NON VITAL BLEACHING TECHNIQUES. A.I. Marujo*, H. Schilder; Boston University.

This study presents an in-vitro comparison of three different non-vital bleach~g techniques: the Walking Bleach technique, the non-vital B.U. Bleaching technique and the combination of Walking and Thermocatalytic techniques as proposed in the l i terature. Extracted teeth were stained using human blood forced into the dentina] tubuli in a process involving high speed centrifugation. Blood staining simulated pulpal hemorrhage which is the primary cause of discoloration. The efficacy of each bleaching technique was evaluated by changes in the teeth shades recorded during the three stages of the investigation: before any procedure (original shades), after blood staining and after the bleachlng procedures (final shades). Instead of traditional shade guides or other subjective color evaluation, shades were measured by a chromometer device from MinoIta Co. known as Chroma Meter CR-IZI. The measurements were based on the CIElab color system.

Results indicated that all three techniques performed reasonably well. The non-vital B.U. Bleaching technique outperformed the others for presenting the smallest standard deviations and the smallest values for Aa and Ab in the CIELab system. This indicated that the non-vital B.U. Bleaching technique was the most consistent and effective in terms of correctin 9 chroma and hue stainin 9 effects.

27 MOLAR ENDODONTIC ACCESS OPENINGS: SIZE, SHAPE AND LOCATION. L.R. Wi lcox* and R.E. Walton; U n i v e r s i t y of lowa.

The cor rec t l o c a t i o n , s lze and shape o f endodontic access openings have not been wide ly i nves t i ga ted . Although e n t i r e chapters of textbooks are w r i t t e n on access prepara t ion , i t is an area of f requen t e r ro r . An example o f apparent a r b i t r a r y designs are molar access openings which tend to be depicted to the mesial in relation to the root canal orifices. This study was designed to relate the access outline on the occlusal to the canal orif ices in molars. 4U Mx and Z3 Md molars with intact or minimally restored crowns were mounted in acrylic. The occlusals were photographed and prints made. The crowns were then sectioned at the CEJ to expose the Canal orif ices. Color slides were made from the occlusal with the camera in the same position as before. The image from the slide was then projected on the previous photograph of the occlusal; the location of the canals could then be marked directly on the print. For Mx molars the MB or i f ice was never mesial to the lingual triangular ridge of the MB cusp and about midway on the ridge. The DB or i f ice was usually close to the buccal groove. The L canal was usually sl ightly distal and buccaI to the L cusp tip. In Md molars the mesial canals were never mesial to the lingual triangular ridge of the MB cusp. The ML canal was close to the central groove. The D canal often was found as far distal as the lingual trlangular ridge of the DB cusp. The results of this study indicate that classical textbook drawings of access locations are too far mesial relative to the canal orifices.

198 AAE Abstracts of Papers

28

AN IN VIVO ASSESSMENT OF NEW ENDODONIIC ELECIRONLC APEX LOCATOR. M. Czonstkowsky*, M. Grassi , H. E l -Tagour i , and F. Hols te in ; Un i ve rs i t y of P i t t sbu rgh .

The purpose of t h i s study was to i n v e s t i g a t e the e f f i c i e n c y of a new e l ec t r on i c apex l o c a t o r , (Endocator) . F i f t y pat ients were randomly selected f o r t h i s s tudy. Medica l ly compromised pa t i en t s were excluded from the study. A complete diagnosis and t reatment plan was establ ished fo r each case. The tee th were i so la ted and conventional access was made in to the pulp c h a ~ e r . The condi t ion of the canals was recorded f o r a l l cases as to the presence of sodium hypoch lo r i t e so l u t i on , local anes the t ic so lu t ion , blood, exudate. The Endocator was used according to the manufacturer 's i n s t r u c t i o n s .

When the instrument i nd ica ted the l oca t i on o f the apica l cons t r i c t i on a measurement was recorded and a v e r i f i c a t i o n by radiographic examinat ion was made. S t a t i s t i c a l ana lys is showed tha t the Endocator was accurate in determin in 9 the position of the constriction at the cementodentinal junction in 96% of the cases, regardless of the v i t a l i t y or contents of the root canal system.

29 HISTOLOGICAL EVALUATION OF BACIERIAL PRESENCE IN INDUCED PERIAPICAL LESIONS IN MONKEY MOLARS. K. Ardjmand and R.E. Walton*; University of Iowa.

The incidence and location of bacteria in endodontic periapical lesions is d i f f i c u l t to determine with accuracy. Histologic evaluation following surgical removal of tissue, or sampling through the canal or a surgical opening have been attempted; these techniques are questionable because of possible contamination and limitation of access to al l the tissue. More accurate histologic determination would be by bacterial staining of tissue removed in block. This study was to determine, i f bacteria were present in necrotic tissue in the canal, would they also be in the periapical lesion?

Pulps were exposed with a #I round bur and the chan~)ers le f t open for a week. Chambers were then sealed with amalgam to induce necrosis. Lesions were obvious radiographically af ter a period of / months. The monkeys were sacrificed and blocks removed that included the tooth and surrounding tissues. Histologic sections were stained by the B & B method and examined for l)incidence and 2)location of bacteria.

Bacteria, primarily gram + cocci, were seen in the canals with necrotic tissue. The colonies extended to and inside the apical foramina. However, there were no colonies or free bacteria in the periapical inflammatory tissue surrounding the root apices. Occasional isolated bacteria were in the tissue adjacent to the foramen, most were intracellular.

In this model system, 9ross bacterial contamination of necrotic material within the canal did not extend into the adjacent inflammatory lesion.

30 IDENTIFICATION OF BACTERIA INVOLVED IN PATHOGENESIS OF HUMAN PERIAPICAL LESIONS BY THE ELISA TECHNIQUE. J. Kettering*, M. Torabinejad and S. Jones; Lema Linda University.

Various classes of immunoglobulins have been found in human periapical lesions. The specif icity of secreted antibodies against antigens within the root canal system has yet to be investigated. The purpose of this study was to identify the microorganisms which cause the production of antibodies in human periapical lesions.

Human periapical biopsies were removed and cultured as organ culture explants. Antibodies produced within the lesion materials were extracted in the cell culture fluids. The use of an enzyme-lined immunosorbant assay {ELISA) can determine the presence, type, and concentration of different antibodies. The sensi t iv i ty of this procedure was increased by using an ELISA Amplification System. By u t i l i z ing this modified technique, the characteristics of various

Journal of Endodontict

antibodies present in perlaplcal lesions were determined against a number of bacterial species commonly found in the root canal system.

The data shows the presence of specific immunoglobulins (IgG and IgA) against Bacteroides gingivalis, Peptostreptococcus micros, Actinomyces is rae l i i , Staphylococcus epidermidis, Streptococcus sanguis, Streptococcus intermedius, and Streptococcus intermedius MG in f ive of eight samples tested. Our results indicate that periapical lesions are multibacterial in origin and are not induced by a single bacterium.

31

STERILIZATION OF BACTERIALLY CONTAMI-ROOT APICES BY CO Z LASER IRRADIATION. L.J. Miserendlno*, W. Kos, C.A. Miserendino and N. Luebke; Marquette University.

The steri l izing potential of CO t laser irradiation was tested on f i f t y - f i ve IOmm sections of endodontically treated human roots. The roots were intentionally instrumented and sealed 2 mm short of the anatomic apex leaving apical tissues intact. The root sections were suspended by orthodontic wire into individual culture tubes and steri l ized by the ethylene oxide gas. Forty-five specimens (15 in each group) were innoculated with one of three bacterial cultures and incubated at 37Uc for 96hrs. Ten specimens served as un-innoculated negative controls. Treatments consisted of: lasing of root apices and surface dentin (Ig of each group); or i r r igat ion with steri le saline and ai r drying for Z min. (b of each group). Root sections were then re-incubated for I wk. in PRG indicator broth to evaluate bacterial growth.

Lased specimens resulted in absence of bacterial growth at 90%, /0%, and BU% for each of the three cultures tested. One of ten negative controls became positive, and Ib of Ib positive controls remained positive. Re-lasing and reincubation of positive specimens resulted in complete inhibition of bacterial growth.

32

A HISTOLOGIC EVALUATION OF APICAL ROOT CANAL DEBRIDEMENT COMPARING TWO ENDODONTIC INSTRUMENTATION TECHNIQUES. D.J. McKendry*; University of Iowa, and R.J. Oswald; University of Washington.

One of the goals of root canal instrumentation is to thoroughly debride the canal system of pulpal and bacterial substrates. Recently an instrumentation technique advocated by Roane has been demonstrated capable of maintaining substantially larger f i l e sizes within the original canal curvature than conventional step-back f i l i ng techniques. The purpose of this study was to determine i f instrumentation with larger f i l e sizes using Roane's Balanced Forces technique produces greater apical canal debridement compared to a step-back f i l i ng technique taught at the University of Washington.

Instrumentation was performed in v i t ro on extracted human teeth using buccal canals of maxi a r ~ l a r s and mosial canals of mandibular molars. F i f t y canals, matched on the basis of curvature, were randomly assigned to one of the two instrumentation techniques. Following instrumentation by the prescribed technique, apical root specimens were harvested and prepared histological ly for evaluation. Serial root cross-sections stained with H & E were evaluated by tracing the total canal outline and the canal outline which had been debrided, determined by Walton's cr i ter ia {planed canal walls). Tracings were digitized using the Quantimet 720 image analysis con~)uter system and the planed canal wall perimeter was expressed for each section as a percentage of the total canal perimeter. Mean apical canal debridement for the Balanced Forces technique was ?b% vs. 66% for the UW technique. Statist ical analysis of the data demonstrated that the Balanced Forces technique debrided the apical canal preparation signi f icant ly better (p. Ub). However, the canal d i f f i cu l t y , determined by the sum perimeter of fins and isthmuses of al l canal cross sections, appears to have been greater in the UW group compared to the Balanced Forces group. Canal d i f f i cu l t y determined by this

...continued

Vol. 14, No. 4, April 1988

icethOd was highly significant in relation to canal debrldement (P. Ul). A two factor ANOYA revealed no significant difference In canal debrldement between |nstrumentatlon techniques when canal d i f f i cu l t y is related as a co-varlable.

I t is concluded that the Balanced Forces technique deb~rlded the apical canal at least as adequatelx as the ~ b a c k f i l ing technique.

33 IHE uSE OF A CHELATING AGENT AND Z.b% NaOCI WITH SONIC AND ULTRASONIC ENDODONTIC INSIRUMENTATION. K.V. Kretl* and D.J. McKendry; University of Iowa.

Previous research has demonstrated that smear layer is generated on dentinal surfaces of small canals where any endodontic instrument touches the canal wall {Krell & Dang, �9 IgB/). Yamada (1g~3) showed that smear layer could be removed using a high volume final flush of b.Z5% NaOCl followed by 17% EDTA. The purpose of this research was to examine the length of the canal wall for presence or absence of smear layer, after sonic or ultrasonic instrumentation with irr igation alternating a chelating agent and hypochlorite. Twenty single rooted teeth were randomly divided into four groups as follows: Group l - Cavi-Endo; Group Z - MM-3ODD with Triosonic f i les; Group 3 - ~-3UOD with Rispisonic f i les; Group 4 - F~I-3UOU with Shaper f i les. All teeth were instrumented Imm short of the apex unti l a fine finger plugger could reach within Imm of working length. Teeth were dried, sp l i t buccal-Iingually and examined using SEM.

All teeth were found to have the majority of the coronal canal--wall free of smear layer. All instrumentation groups had teeth with areas of pulp debris in the apical portion of the canal that showed smear layer intact. Despite frequent exchanges of i rr igant, remaining pulpal debris apparently impaired the ab i l i ty of the chelating agent and hypochlorite to always reach the apical portion of the canal.

The results of this study show that sonic or ultrasonic instrumentation used with alternate i r r igat ion usin 9 ~elatin~ agents and h~pochlorite can completely remove smear Iayer from the canal wall in unobstructed canal spaces.

34 PULPAL IISSUE IN ACCESSORY CAICALS AND IIS REACIION TO ENDODONTIC PROCEDURES. K. Langeland* and E. Pascon; University of Connecticut.

The existence of ramifications of the root canal system of teeth is known (Hess & Zurcher, 1925). The purpose was to study the status of the pulp tissue in accessory canals and apical ramifications [a.c. & a.r . ) of teeth and its relations in endodontology. The material consisted of intact teeth, teeth exposed to plaque, to caries, to debridement, to obturation with various methods and devices. In intact teeth, v i ta l pulp tissue was consistently found in a.c. & a.r. When plaque closed a.c. & a.r., circulation was cut, but inflammation of adjacent pulp tissue was minimal. When plaque cut circulation of the main foramen ~a), necrosis involved root pulp; v i ta l tissue remained in the pulp chamber of multirooted teeth. During disintegration of the main canal pulp, the tissue in the a.c. & a.r. remained vi tal as far as the tissue in the main canal, but was part ia l ly necrotic when necrosis reached the level of the pulpal entrance of a.c. & a.r. Debridement partially removed l iquif ied tissue from the pulpal entrance to a.c. & a . r . , the adjacent tissue was inflamed with a p.a. lesion. Vital tissue in a.c. & a.r. was not eliminated by debridement. Particles of endodontic materials were observed in the remaining v i ta l tissue of the a.c. & a.r. Eonclusion: The tissue in the a.c. & a . r . : l ) remained vital until necrosis of the main canal reached the main apical foramen(a); Z) circulation from periodontal ligament was the main factor; 3) particles of endodontic obturation ~ te r ia ls , when pushed into a.c. & a . r . , caused an Tnflammation and a foreign bod~ reaction. Supported by U.S. Fublic Health Service Urant NO. DEU4U~b.

35

AAE Abstracts of Papers 199

ATTACIIMENT OF PDL DERIVED CELLS I0 EXPERIMENTALLY TREATED ROOT SURFACES. P. Bery" and J. Daniel, Depts. of Endodontics and Histology, University of I l l i no is at Chicago.

Loss of the periodontal ligament is a common occurrence for avulsed teeth. Following replantation of these teeth, ankylosis or resorption usually occurs. In v i t ro studies have dealt with the reattachment of periodontal cells to chemically treated root surfaces in an attempt to find an optimal substrate for those cells. The purpose of this study was to compare different root surface treatments in order to determine the best environment for attachment and growth of human PDL-derived cells in v i t ro. Cells from the healthy PDL of orthodontically extracted teeth were obtained and cultured in the laboratory. Those cells were transferred to root surfaces that had been either planed or unplaned, exposed to enzymes (collagenase, hyaluronidase), fixatives (glutaraldehyde) and fibronectin. For easy identification, the cells were labeled with t r i t ia ted thymidine. After Z4 or 4B hours of contact with the root surface, the cells were exposed to photographic emulsion. After processing, the cells showed clearly on the root surface and could be easily counted under microscopic examination. Attachment and growth were compared among the different samples. Statistical analysis shows that there was no difference in the amount of attachment in v i t ro , as long as clean, ster i le surfaces were used.

Supported by a grant from the NIH.

36 NIIINOL ROOI CANAL FILES: A PRELIMINARY STUDY. H. Walia ", W.A. Brantley, N.H. Luebke and L.J. Miserendino; Marquette University.

Previous studies on stainless steel root canal f i les and reamers have reported an increase in stiffness with an increase in instrument size. This stiffness may significantly alter the original canal shape, especially in curved canals. The purpose of this study is to compare the f l ex ib i l i t y of Nitinol alloy f i |es with stainless steel alloy f i les.

The size #35 Nitinol f i l e was evaluated in cantilever bending test mode with the #3b f i les of Kerr Standard, Kerr K-Flex, Unitek Type K, Union Broach Flex-R and Quality Dental Products Super Flex. A manual loading apparatus based upon the original form of ADA specification #Z~ was used for analysis.

Analysis of the test plots revealed all stainless steel f i les exhibited permanent deformation at angular deflections between 30 and 40 degrees, while the Nitinol f i l e largely exhibited no deformation, even at 90 degrees.

The Nitinol f i les exhibited two to three times the elastic f l ex ib i l i t y of stainless steel alloys, a property well desired for instrumentation of curved canals.

37 A PRELIMINARY INVESTIGATION OF THE TORSIONAL PROPERTIES OF THE GATES-GLIDDEN BUR. N.H Luebke*, H. Walia and W.A. Brantley; Marquette University.

Gates-Glidden burs used in endodontics carry the inherent risk of separation in the canal. The purpose of this laboratory study was to characterize the type of fracture and the corresponding torsional duct i l i ty applied in a counter clock-wise manner. We have not encountered any other information on this subject.

Five burs in sizes #l, #2, and #3 were tested in a hand operated torque meter assembly based upon the original ADA Specification #2B. Both torque moment and angular deflection were continuously recorded for counter clock-wise torsional testing unti l fracture occurred. SEM photomicrographs were used to characterize the fracture surfaces.

The results of this study showed that the performance of the burs successively decreased in a significant manner with decreasing bur size when evaluated for mean torque and mean revolutions to failure. The following data were obtained for the mean values (standard deviation) of torsional moment

...continued

200 AAE Abstracts of Papers

and revolutions to failure: #I - 2.34 in-oz (0.9} and 0.875 rev; #2 - 4.22 in-oz (0.13) and 1.25 rev; #3 - 5.25 in-oz (0.21) and 1.25 rev. The #2 and #3 burs fractured closer to the bur shank than the #I bur which fracture~ very close to the bur head. The burs separated in a ductile mode of fracture. Further studies are in progress to establish base- line information for all rotary endodontic instruments.

38

ANALYSIS OF THE INTERNAL COMPACTNESS OF SEVEN OBTURATION METHODS USING GUTTA-PERCHA. E. Jacobsen" and E. BeGole; University of I l l inois at Chicago.

The purpose of the investigation was to compare the internal compactness of the seven commonly used gutta-percha obturation methods: (1) lateral; (2) single cone #II0 gutta-percha; (3) chloroform dipped gutta-percha (5 sec); (4) chlorofom dipped gutta-percha (lO sec); (5) warm lateral; (6) thermomechanical; and (7) thermoplastic condensations with the incorporation of a control group consisting of a highly polished metal rod. Each obturation technique was carried out on five different occasions in a metal mold representing a root canal system. Following obturation, the gutta-percha was retrieved from the mold and fractured in liquid nitrogen at 1.0, 3.5 and 6.6mm, measured from the apex. The samples were placed in a scanning electron microscope and the image transferred to a digit izer which converted the image to digital data consisting of a matrix of dots (pixels) each representing varying shades of gray. The pixels in digitized form were transferred to a computer where each image was delineated by polygonal boundaries. A mathematical method for computing the surface compactness was util ized, and coefficients were stat ist ical ly analyzed using analysis of variance.

The results demonstrated that lateral condensation produced'a more compact surface than thermomechanical, thermoplastic, single cone gutta-percha, 5-sec and lO-sec chloroform dipped 9utta-percha whereas, statistically~ lateral condensation did not d i f fer from warm lateral condensation or the control,

39

AN EVALUATION OF APATITE ROOT SEALER. R.A. Barkhordar*, M.M. Stark and K. Soelberg; U n i v e r s i t y o f Ca l i f o rn i a at San Francisco.

Sol id core f i l l i n g mater ia l such as gut ta-percha has been used to f i l l the root canal system in conjunction with a sealer to prevent apical leakage. The purpose of this study was to evaluate the apical seal produced by an apatite root sealer. Seventy roots of maxillary central incisors were cleansed and shaped and randomly assigned to one of seven groups of ten roots each. The root canals were obturated with gutta-percha and one sealer using vertical condensation

Journal of Endodontics

technique. Group I , I I , l iT, IV, V and VI consisted of roots in which the canal was f i l led with Grossman's sealer, Sealpex, Kerr root canal sealer, Sankin apatite root sealer Type I , Sankin apatite root sealer Type I I , or Sankin apatite root sealer Type I l l respectively. Group VII was f i l led with gutta-percha and without sealer to serve as a control. The access opening was f i l l ed with amalgam. Each root was then placed in a capped vial containing 2x2 gauze pads saturated with d is t i l led water, and the sealer was allowed to set at 37oc in humidor for 48 hours. The roots, except 2mm of the apical area were coated with two layers of clear varnish. The roots were then immersed in a vial containing si lver nitrate. The roots were sectioned longitudinally and the degree of dye penetration was measured under a dissecting microscope. The mean of apical leakage (mm) is as follows: I = 3.68; IT = 0.91; I l l = 3.66; IV = 2.20; V = 1.77; Vl = 2.61; and VII = 7.71. Results indicated that Seal~ex had the best sealln 9 abi l i ty followed by Sankin -- apatlte root seale~ Type I I while Grossman's cement showed the maximum dye penetration. Canals that were obturated with 9utta-percha and without isealer showed significantly ~reater apical leakage (p .ul).

40 i i

EVALUATION OF PERIRADICULAR TISSUE HEALING FOLLOWING ENDODONTIC SURGERY. C. Mangkornkarn* and J.W. Harrison; Baylor College of Dentistry

The purpose of this study was to evaluate and compare the periradicular tissue healing associated with amalgam and thermoplasticized gutta-percha (TGP) retrofi l l ings following endodontic surgery. Amalgam is currently the most commonly used re t ro f i l l ing material. However, numerous materials have been suggested for use as retrof i l l ing. TGP has been recommended for this purpose because i t provides a good seal, is easy to manipulate and would reduce surgical chairside time.

TGP has been shown to be as effective as other methods of obturation for i ts sealing abi l i ty and adaptability to canal walls. But, to date, no histologic studies regarding periradicular tissue response and osseous biocompatibility of TGP has been reported.

The study was done in six monkeys, involving 24 maxillary incisors. Conventional root canal therapy was done in three maxillary incisors in each monkey. The remaining incisor received no treatment and served as a control. Periapical surgery was performed on 18 experimental teeth and amalgam and TGP ret rof i l l ing materials were placed in the resected root ends. The animals were sacrificed at 4, 8 and 16 weeks. Histologic sections were prepared for examination under l ight and polarizing microscopy.

The results of this study indicated no significant difference in osseous heal'ing of tissue adjacent to amalgam and TGP retrof i l l ings at ]6 weeks. However, in i t ia l bony regeneration associated with TGP was s l ight l } slower than the amalgam group at 4 and B weeks. TGP ret rof i l l in~ appeared to be we11-tolerated and biocompatible to periapi~al tissues.