Department of Endodontics

Leakage of bacteria from the coronal aspect may cause failure of root canal therapy when an inadequate coronal seal is present. Chlorhexidine, by its ability to bind to dentin and elicit long-term antibacmrial activity, may be an effective intracanal medicament in retarding bacterial leakage. The purpose of this study was to determine if pretreaIment of the root canal system with chlorhexidine will retard or prevent bacterial leakage through the obtur~ed root canal. Standardized and sterilized roots of extracted human teeth were completely instrumented to ISO size 60 and incubated in saturated calcium hydroxide (n=20), 0.12 percent chlorhexidine digluconate (n=20), or sterile water (n=6). After ten

The purpose of this study was to evaluate the extent of bacterial reduction with nickel-titanium rotary instrumentation and 1.25% NaOCl irrigation. Also, the additional antibacterial effect of calcium hydroxide for >1 wk was tested. Forty-two subjects with radiographic and clinical ...

The attachment of Srreprococcus 01 5 to the acquired pellicle difTered from its sorption to uncoated tooth enamel surfaces. Attachment was mediated by specific components of the pellicle. Pre-incubation of the saliva used for pellicle formation with Strep. 01 5 removed the pellicle components responsible for attachment: pellicles formed from absorbed saliva showed impaired affinity for the test strain. Pellicles derived from saliva treated with hydroxyapatite had lowered affinity for Srrrp. 01 5: apparently. the components responsible for attachment adsorbed to hydroxyapatite. Salivary components could be adsorbed on and eluted from cells of Smp. 01 5. The eluate agglutinated the test strain and could be used to produce a pellicle which greatly promoted attachment of the test strain. The eluate fractionated with one saliva-specific peak when filtered through a Sephadex G-200 column: no fraction showed agglutinating or attachment-promoting activity alone. The eluate reacted weakly with an antiserum to human whole saliva. It was rich in lysozyme but showed only traces of amylase activity. It did not contain detectable amounts of immunoglobulins. ISTWODI'CllON Dental plaque formation is gcncrally initiated by the attachment of salivary bacteria to the acquired cnamcl pclliclc (Saxton. 1973). Attachment appears to involve specific reactions of pclliclc components with sclccted bacterial spccics (Hillman, van Houtc and Gibbons. 1970: van Houtc. Gibbons and Banghart. 1970: cjrstavik. Kraus and Hcnshaw. 1974). The specificity of the attachment reaction may be reflected in the bacterial composition of early plaque; Srwprococcus sanyuis is abundant in young plaque (Carlsson. 1965) and shows high affinity for the acquired pellicle in rirro (Orstavik er a/.. 1974). Knowledge of the nature of the interactions between pioneer bacteria and pellicle components would improve our understanding of how plaque formation is initiated, and may provide guidelines for preventive measures directed at the inhibition of plaque formation.

The microbiological properties of four tissue conditioners, one soft liner, and one acrylic resin were studied. The tissue conditioners showed no or negligible antimicrobial effects toward salivary microorganisms by two different in vitro tests. In in vitro adhesion experiments, more Streptococcus mutans and Candida albicans adhered to the tissue conditioners and the soft liner in comparison with conventional acrylic resin used for denture-base fabrication. No difference in bacterial adhesion was found among the tissue conditioners. The microbial colonization of two tissue conditioners lined on maxillary dentures in three volunteers was followed for 14 days. No difference among the materials was found, but a tendency for subjectdependence in plaque formation on the materials was noted.

The change in temperature in cylindrical specimens of 7 different dental cements was measured under various storage conditions after removal from a water bath at 37~ The strength of these cements was also measured using the same type of specimens in water at 37~ and at 0.5, 1, 5 and 60 rain after removal from the water bath. All cements showed a rapid drop in temperature after removal from the water, somewhat dependent on the handling of the specimens. A significant increase in strength was shown for all cements during the first minutes after removal from the water bath. Testing cements at room temperature requires specific instructions with regard to the handling of the specimens and to the time after removal from the water bath for application of the load. Testing in water at 37~ eliminates these problems.

A long-term test was started in 1979 to evaluate the clinical serviceability of a zinc-phosphate and a polycarboxylate cement. After 54 months observation both cements had served equally well. One crown had come loose in either group, but that was due to loosening of separately cemented posts and not to loosening of the outer crown. The results of the PAI scores indicated a possible difference in pulpal compatibility between the 2 cements, polycarboxylate cement giving the lowest scores.

The purpose of this study was to assess the efficacy of Nd:YAG laser irradiation in disinfecting the root canal system. Seventy-five teeth were uniformly instrumented and sterilized, and their root canals were infected for 60 min with an overnight culture of Enterococcus faecalis in Tryptic Soy Broth. The teeth were divided into 6 groups: 1-non-infected controls; 2 " infected controls; 3-infected, laser treated; 4-infected, laser dummy (dye only); 5-infected, laser dummy (dye and air-water spray); 6infected, NaOCl-treated (reference group). After treatment, the root canals were dried and dentinal sha\ings removed for a posttreatment culture. Quantitative analysis of bacteria surviving the various treatments were performed, and the baeterial counts for each group were compared. SEM analysis of teeth split longitudinally was used to illustrate the effect of treatment on the smear layer and on surface bacteria. Nd:YAG laser irradiation (group 3) significantly reduced the number of bacteria while NaOCl irrigation (group 6) effectively disinfected the canals.

Aim The aim of the study was to compare the quality of root ¢llings completed by lateral condensation (LC), Therma¢l (TF), and a new technique using Ther-ma¢l for back¢lling (BF), with special emphasis on control of over¢lling. Methodology Sixty curved canals in plastic blocks were prepared with the ProFile system to size 40/04 taper in the apical half and to 06 taper in the coronal half. The canals were divided into three groups of 20. Apical patency was veri¢ed with a size 15 K-¢le. The canals were then ¢lled using three di¡erent techniques: LC (20 canals), TF (20 canals), and BF, where a size 40 master point with sealer was seated prior to the introduction of a size 30 Therma¢l point (20 canals). The same resin-based sealer was used on each occasion. The root ¢llings were assessed using stereomicroscopy for material extrusion, digital radiography for occurrence of voids, and microscopy of sections for voids and thickness of sealer layer. Results Extrusion of both gutta-percha and sealer occurred in all 20 canals ¢lled with the TF technique, but only three and ¢ve cases of sealer extrusion were detected with LC and BF techniques, respectively. No voids were detected in the TF group, whereas small voids were present in most ¢llings in the LC and BF groups. The average total length of the voids was less than 1 mm per canal. The thickness of the sealer layer in the middle and apical parts was greater in the LC and BF groups than in the TF group. Conclusions LC and BF techniques resulted in fewer over¢lls than TF. Voids were absent in TF ¢llings, whilst small voids were found in the LC and BF groups.

Yeasts belong to a separate kingdom of living organisms, fungi. Contrary to bacteria, fungi are eukaryotic organisms, i.e., their genome is organized in a nucleus which is surrounded by a membrane. This membrane is continuous with the endoplasmic reticulum, and organelles, such as mitochondria, ribosomes, and different storage inclusions, are present. Fungal cell walls are rigid structures composed mainly of glucan, mannan, and chitin. For nutrition, fungal organisms are dependent on nitrogen and carbon compounds which are taken up through the cell wall (De Hoog and Guarro, 1995). Yeasts are present in various sites in the human body as members of the normal flora. They occur, e.g., in the gastrointestinal tract, vagina, and perineal area (Jarvis, 1996). The oral cavity has suitable environmental conditions for yeast colonization. Oral yeasts belong to the division Ascomycota and class Endomycetes, which is divided further into four families:

from the coronal aspect may cause failure of root canal therapy when an inadequate coronal seal is present. Chlorhexidine, by its ability to bind to dentin and elicit long-term antibacmrial activity, may be an effective intracanal medicament in retarding bacterial leakage. The purpose of this study was to determine if pretreaIment of the root canal system with chlorhexidine will retard or prevent bacterial leakage through the obtur~ed root canal. Standardized and sterilized roots of extracted human teeth were completely instrumented to ISO size 60 and incubated in saturated calcium hydroxide (n=20), 0.12 percent chlorhexidine digluconate (n=20), or sterile water (n=6). After ten days, the medicaments were removed and the teeth were sonicated in sterile water for five minutes. The teeth were dried and obturated to within 1 mm of the apex with gu~a percha and Po01's sealer using lateral condensation. Each obmrated root was then sealed with wax between an upper chamber containing a streptomycinresistant strw of Staphylococcus epiderraidis in broth, and a lower

A standardized and reproducible method of radiopacity measurements of dental materials is presented. The method entails densitometric comparison of standard-sized specimens with an aluminum step wedge under controlled conditions for exposure and film processing. Methodologic aspects have been evaluated and discussed. Measurements of forty root canal sealers demonstrated wide variations among the different types. Visual examination could not provide reproducible measurements of the radiopacity of the materials.

The antibacterial activity of chlorhexidine digluconate and iodine potassium iodide on Enterococcus faecalis A197A was tested in the presence of dentin, dentin matrix, dentin pretreated by EDTA and citric acid, collagen, and heat-killed cells of Enterococcus faecalis and Candida albicans. Medications were preincubated for 1 h with each of the potential inhibitors and tested for their antibacterial activity against E. faecalis, strain A197A. Surviving bacteria were sampled after 1 and 24 h of incubation. Dentin matrix and heat-killed microbial cells were the most effective inhibitors of chlorhexidine, whereas dentin pretreated by citric acid or EDTA showed only slight inhibition. Dentin and skin collagen showed some inhibition at 1 h but not after 24 h. Iodine potassium iodide was effectively inhibited by dentin, dentin matrix, and heat-killed microbial cells. Skin collagen and dentin pretreated by EDTA or by citric acid showed little or no inhibitory effect on iodine potassium iodid...

The microscopic details of the debonded interfaces between endodontic sealers and dentin or gutta-percha were assessed in this study. Dentin, conditioned with 37% H3PO4 for 30 s, 25% citric acid for 30 s, 17% EDTA for 5 min, or a rinse with 10 ml of distilled H2O (control), and gutta-percha surfaces were coated with freshly mixed sealer: Grossman's sealer, Apexit, Ketac-Endo, AH Plus, RoekoSeal Automix, or RoekoSeal Automix with an experimental primer. The surfaces were pressed together and the sealers were allowed to set. After tensile bond strength testing, the morphological aspects of the fractured surfaces were assessed by scanning electron microscopy and energy dispersive spectroscopy. The energy dispersive spectroscopy successfully traced sealer components to the debonded surfaces. Some of the sealers penetrated into the dentinal tubules when the dentin surface had been pretreated with acids. However, these sealer tags remained occluding the tubules after bond failure in s...

The antibacterial efficacy of irrigating solutions and local disinfectants used in endodontics appears poorer in vivo than in vitro. One explanation may be inactivation by compounds present in the root canal. MTAD (a mixture of tetracycline isomer, acid, and detergent) is a new root canal irrigation solution with antibacterial activity. The aim of this study was to investigate the antibacterial activity of MTAD and chlorhexidine towards two strains of Enterococcus faecalis and the inhibitory effects of dentine and bovine serum albumin on the antibacterial activity. Survival of bacteria exposed to the medicaments in the presence or absence of inhibitors was monitored in an in vitro model. Full concentration (100%) MTAD and 0.2% chlorhexidine rapidly killed both strains. Combining chlorhexidine with cetrimide further reduced the time required for killing. The presence of dentine or BSA caused a marked delay in killing by both medicaments. The two E. faecalis strains tested showed mino...

An in vitro model was developed for investigation of Candida albicans penetration into human dentinal tubules. The model consisted of a dentin disc mounted between two cuvettes that each had a circular opening facing the disc. The cuvettes were filled with Tryptic-Soy-Broth, and the pulpal side cuvette was inoculated with C. albicans and incubated at 37 degrees C in air until growth occurred in the uninoculated cuvette or up to 30 days. The system was also used with Enterococcus faecalis. Completely glue-covered dentin specimens served as negative controls. Brown & Brenn-stained histological preparations of the specimens were examined with light microscopy. The time needed before growth occurred in the uninoculated cuvette showed great variation with C. albicans, whereas E. faecalis penetrated within 1 to 5 days of incubation. Slight penetration both by hyphae and yeast cells was observed in specimens inoculated with C. albicans, whereas specimens inoculated with E. faecalis showed ...

In this study computerized image analysis procedures were applied to endodontic radiographs. Kontron IBAS 2000 is a commercially available image analysis system with processing routines applicable to radiograph digitizing and transformations. The system was evaluated for: its ability to harmonize blackening and contrast in endodontie radiographs; its ability to compensate for angulation distortion of sequential exposures of individual teeth; its potential for applieation of digital subtraction methods; and its use in automated gray-level analyses of diseased and healthy bone areas in endodontic radiographs. The Kontron IBAS 2000 system proved suitable for all applieations. However, the speciflcity of the subtraction procedure was limited by some inherent problems in the harmonization of blackening and in the subtraction process itself. On the other hand, automated gray level measurements proved to be a robust method for unbiased and quantitative assessment of healing of apical periodontitis.

One-hundred and twenty-three polyethylene tube implants of 12 endodontic sealers were placed subcutaneously into rats. The implants were left in situ for periods of 14 and 90 days. The tissue response was analyzed histologically and by scanning X-ray microanalysis. The tissue responses differed markedly in the intensity, extent, and cellular characterislics. A slight long-term tissue response was noted for polymeric resin-based materials; zinc oxide-eugenol-based sealers gave a stronger reaction; and a chloroform-based and two paste-type materials caused the least favorable reactions. X-ray microanalysis of tissue sections revealed material components in the reactive capsule and in the peripheral connective tissue of most specimens investigated. Implants of the resin-based sealers, AH26 and Hydron, were surrounded by macrophages, phagocytosing heavy metal components (Bi, Ba) of the materials. Zinc oxide-eugenol-and chloroform-based materials appeared more frequently to fragment into particles of sizes too large for monocellular phagocytosis.

NIOM-SCANDINAVIAN INSTITUTE OF DENTAL MATERIALS Root canals with vital pulps in four Macaca fascicularis monkeys were subjected to pulp extirpation and root filling with1 gutta-percha and sealer, either AH26, Endomethasone, Kloroperka N-G, or ProcoSol. Observation pleriods were 1 and 6 months. The results of treatment were evaluated by radiographic analysis (periapical index scores) and by histopathologic assessment of the remaining pulp and periapical tissues. Sixty roots with acceptable termination (between 0.5 and 3 mm from apex) of the root fillings and adequate histopathologic specimens were available for analysis. These roots were equally distributed in