A comparative study of lateral condensation, heat-softened gutta-percha, and a modified master cone heat-softened backfilling technique

AIM

The aim of the study was to compare the quality of root fillings completed by lateral condensation (L), Thermafil (TF), and a new technique using Thermafil for backfilling (BF), with special emphasis on control of overfilling.

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 verified with a size 15 K-file. The canals were then filled using three different 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 Thermafil point (20 canals). The same resin-based sealer was used on each occasion. The root fillings were assessed using stereo-microscopy 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 filled with the TF technique, but only three and five 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 fillings 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 overfills than TF. Voids were absent in TF fillings, whilst small voids were found in the LC and BF groups.

A comparison of the quality of root canal treatment in two Danish subpopulations examined 1974-75 and 1997-98

AIM

The aim of this study was to compare the quality of root canal treatment in two Danish subpopulations.

METHODOLOGY

Group 1 (358 patients) was examined 1974-75 and group 2 (244 patients) 1997-98. All patients were more than 20 years old. All had undergone a full-mouth radiographic survey. In root-filled teeth the following parameters were assessed: the quality of the coronal restoration or crown, the lateral seal of the root filling, the length of the root filling, and the periapical status. Chi-squared tests were used for the evaluation of differences between the groups.

RESULTS

In group 1 there were 975 endodontically treated teeth, in group 2 there were 753. In group 1 the majority of root-filled teeth were premolars, in group 2 the majority were molars (P < 0.001). The quality of coronal restorations (P = 0.35) and crowns (P = 0.68) did not differ significantly between the groups. In group 2 more teeth had adequately sealed root canals (P < 0.001) and adequate length of root filling (P < 0.001). More root-filled molar teeth had apical periodontitis (AP) than root-filled premolar and anterior teeth (P < 0.001).

CONCLUSIONS

Whilst the technical quality of endodontic treatment had improved during the last 24 years, basic differences between the populations prevented assessment of the impact of this change on disease frequencies. The study indicates that great care should be taken when comparing different patient populations, in particular more emphasis should be placed on the selection and description of study groups.

Reduction of intracanal bacteria using nickel-titanium rotary instrumentation and various medications

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 signs of chronic apical periodontitis were recruited. The canals were sampled before treatment, during and after instrumentation, and after treatment with calcium hydroxide and the samples incubated anaerobically for 7 days at 37 degrees C. The bacteria from each sample were quantified and the log10 values were used for calculations and comparisons. The initial sample confirmed infection of the canals. There was a significantly greater pattern of reduction of bacteria when NaOCl was used as an irrigant, compared with sterile saline (p < 0.05). After instrumentation with NaOCl irrigation, 61.9% of canals were rendered bacteria-free. The placement of calcium hydroxide for at least 1 wk rendered 92.5% of the canals bacteria free. This was a significant reduction, compared with NaOCl irrigation alone (p = 0.0001). The results of this study indicate that NaOCl irrigation with rotary instrumentation is an important step in the reduction of canal bacteria during endodontic treatment. However this method could not consistently render canals bacteria-free. The addition of calcium hydroxide intracanal medication should be used to more predictably attain this goal.

In vitro susceptibility of Candida albicans to four disinfectants and their combinations

AIM

The aim of this study was to evaluate the susceptibility of seven strains of Candida albicans to four disinfectants: iodine potassium iodide, chlorhexidine acetate, sodium hypochlorite and calcium hydroxide. In addition, all possible pairs of the disinfectants were tested in order to compare the effect of the combination and its components.

METHODOLOGY

Filter paper discs were immersed in standardized yeast suspensions and then transferred to disinfectant solutions of different concentrations and incubated at 37 degrees C for 30 s, 5 min, 1 h and 24 h. After incubation the filter paper discs were transferred to vials with PBS and glass beads that were then vigorously shaken for dispersal of the yeast cells. PBS with resuspended yeasts was serially diluted 10-fold. Droplets of 25 microL from each dilution were inoculated on TSB agar plates and incubated in air at 37 degrees C for 24 h. The number of colony-forming units was then calculated from appropriate dilutions.

RESULTS

C. albicans cells were highly resistant to calcium hydroxide. Sodium hypochlorite (5% and 0.5%) and iodine (2%) potassium iodide (4%) killed all yeast cells within 30 s, whilst chlorhexidine acetate (0.5%) showed complete killing after 5 min. Combinations of disinfectants were equally or less effective than the more effective component. All C. albicans strains tested showed similar susceptibility to the medicaments tested.

CONCLUSIONS

This study indicates that sodium hypochlorite, iodine potassium iodide and chlorhexidine acetate are more effective than calcium hydroxide against C. albicans in vitro. However, combining calcium hydroxide with sodium hypochlorite or chlorhexidine may provide a wide-spectrum antimicrobial preparation with a long-lasting effect.

Bacterial leakage versus dye leakage in obturated root canals

AIM

The aim of this study was to compare in vitro bacterial and dye leakage tests, commonly used to determine the seal of root canal fillings.

METHODOLOGY

Ninety-six single-rooted teeth had their crowns removed at the cemento-enamel junction and their roots instrumented to ISO size 60 within 1 mm of the apex. Three groups of 30 roots were obturated by lateral condensation using gutta-percha and one or other of the sealers. AH26, Ketac Endo, or Roth's 801 sealer. Three roots were used as negative controls and three roots as positive controls. The roots were then exposed at their coronal end first for 38 days to soy broth containing Staphylococcus epidermidis and thereafter for 48 h to basic fuchsin. Bacterial leakage was recorded when the challenging organism could be recovered from the apical end. Dye leakage was checked by microscopy of transverse sections of the apical tip at the end of the experiment.

RESULTS

For the bacterial experiment, there was no significant difference amongst the three sealer groups. The dye experiment showed significantly greater leakage in the AH26 compared to the Ketac Endo group. No correlation between the results of the two tests could be seen.

CONCLUSIONS

The results of this study suggest that the molecular size of the penetrating agent may not be the relevant parameter when attempting to determine an appropriate test for the sealability of root canal fillings.

Endodontic treatment of teeth with apical periodontitis: single vs. multivisit treatment

This study was performed to evaluate radiographic healing of teeth with apical periodontitis, treated in one visit or in two visits (a) with or (b) without calcium hydroxide as an intracanal disinfecting medicament. The patients were assigned one of the three treatment groups by the throwing of a die. The Periapical Index (PAI) Scoring Method was used to compare differences in periapical status from the beginning of treatment to a 52-wk follow-up evaluation. Overall, the periapical status of the treated teeth improved significantly after 52 wk (p < 0.0001). A PAI score of 1 or 2 was considered as representing a "good" periapical status while 3, 4, or 5 was a "bad" status. When base line PAI scores were controlled for, the calcium hydroxide group showed the most improvement in PAI score (3, 4, or 5 to 1 or 2), followed by the one-step group (74% vs. 64%). The teeth that were left empty between visits had clearly inferior healing results. Power statistics were conducted to determine the numbers required for significant differences between the groups, and it was shown that large experimental groups on the order of hundreds of patients would be required to show significant differences.

Susceptibility of oral Candida species to calcium hydroxide in vitro

AIM

The susceptibility of common oral Candida species to saturated aqueous calcium hydroxide solution was studied.

METHODOLOGY

The yeast species tested were C. albicans (16 strains). C. glabrata (three strains), C. guilliermondii (three strains), C. krusei (two strains), and C. tropicalis (two strains). At least one reference strain of each species was used; the others were clinical isolates either from persistent apical periodontitis or from marginal periodontitis. The susceptibility of Enterococcus faecalis (ATCC 29212) was studied for comparative purposes. Standardized inocula of the strains were incubated in aqueous calcium hydroxide solution, pH 12.4, for time-periods ranging from 5 min to 6 h. Volumes of 0.1 mL of the test suspension were cultured directly on Brucella blood agar and incubated in air at 37C. The plates were inspected for growth at 24 and 48 h and the colonies were counted. The time required to reduce the number of colony-forming units to less than 0.1% of the initial number was determined for each strain.

RESULTS

The sensitivity of the C. albicans strains was generally low, with 16 h of incubation required to kill 99.9% of the colony-forming units. No differences in susceptibility between C. albicans strains isolated from root-canal infections and from periodontitis were found. Both strains of C. tropicalis were killed between 3 and 6 h of incubation, whilst strains of C. guilliermondii were killed after only 1020 min of incubation. All strains of C. glabrata survived 20 min, but not 1 h, of incubation, whilst 13 h were required to kill C. krusei. Compared with E. faecalis, all Candida spp. showed either equally high or higher resistance to aqueous calcium hydroxide.

CONCLUSIONS

This study indicates that Candida spp. are resistant to calcium hydroxide in vitro, which may explain the isolation of yeasts from cases of persistent apical periodontitis.

Bacterial reduction with nickel-titanium rotary instrumentation

The purpose of this study was to compare intracanal bacterial reduction on teeth instrumented with 0.04 tapered nickel-titanium (NiTi) rotary instrumentation to bacterial reduction when using a stainless-steel K-file step-back technique using sterile saline irrigation. Forty-eight patients with apical periodontitis were randomly assigned treatment type. The canals were sampled before, during, and after instrumentation. The samples were incubated anaerobically for 7 days at 37 degrees C, colony-forming unit numbers calculated, and a log transformation performed to normalize the counts. Teeth exhibiting apical periodontitis were uniformly infected, whereas vital control teeth were not. A similar and uniform reduction occurred with progressive filing, regardless of technique (p < 0.0001). There was no detectable difference in colony-forming unit count after NiTi rotary or stainless-steel hand instrumentation (p = 0.42). Neither technique could predictably render canals free of bacteria. The results of this study indicate NiTi rotary and stainless-steel hand K-file step-back instrumentation techniques were not significantly different in their ability to reduce intracanal bacteria.

Application of computerised image analysis to monitoring endodontic therapy: reproducibility and comparison with visual assessment

OBJECTIVE

To evaluate the intra- and interexaminer reproducibility of computerised image analysis for the assessment of periapical bone changes based on gray value ratio when compared with a visual method.

METHODS

353 radiographs obtained in a clinical endodontic study were analysed. Densitometric analyses were used to evaluate changes in bone density following endodontic treatment. The diseased area of apical periodontitis' (AP) and 'normal bone area' (AN) were defined and ratios of the gray values (AP/AN) were calculated for each radiograph. Periapical index (PAI) was used as the 'gold standard'. Correlation coefficient (r), Kappa (kappa), and t-test for matched pairs were used for the statistics.

RESULTS

The method proyed to be reproducible for intra-examiner re-examinations, r ranging from 0.7 to 0.84 (P < 0.01). Kappa showed fair to good agreement for data divided into four or three categories (kappa = 0.25-0.64). Dichotomised data showed fair to moderate agreement (kappa = 0.33-0.4) when the whole process was repeated, and good to very good agreement (kappa = 0.64-0.85) for the delineation process alone. The interexaminer comparisons showed fair to moderate agreement (kappa = 0.3-0.49). Comparison with PAI showed a 61% sensitivity and 79% specificity in detecting severe lesions (corresponding PAI scores 4 and 5) and the kappa value of 0.40 showed moderate agreement. The image analysis was sensitive enough to detect healing one month after treatment in a group of teeth with substantial lesions (P < 0.05).

CONCLUSIONS

The computerised image analysis system seems to be an appropriate tool to detect the periapical bone changes in dental radiographs at a group level.

Time-course and risk analyses of the development and healing of chronic apical periodontitis in man

Roots with and without preoperative chronic apical periodontitis were root canal treated and followed clinically and radiographically yearly for up to 4 years. Of 732 roots treated, 599 (82%) were available for evaluation at one or several recalls. Chronic apical periodontitis (CAP) was recorded with the periapical index scoring system. CAP developed in 29 of 473 (6%) of teeth without preoperative signs of disease, whereas 111 of 126 (88%) initially diseased roots showed signs of healing. The rate of healing CAP and the rate of emerging CAP were calculated, and analyses of event occurrence each year of observation were performed. Peak incidence of healing or emerging CAP was at 1 year in both instances. Risk assessments at 2, 3, and 4 years did not indicate an added risk of filled roots developing CAP during this period. Complete healing of preoperative CAP in some instances required 4 years for completion, while signs of initiated, but incomplete, healing were visible in at least 89% of all healing roots after 1 year. Risk analyses may provide relevant information in addition to or in substitution for success/failure analyses.

Nd:YAG laser irradiation in root canal disinfection

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); 6--infected, NaOCl-treated (reference group). After treatment, the root canals were dried and dentinal shavings removed for a post-treatment culture. Quantitative analysis of bacteria surviving the various treatments were performed and the bacterial 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.

A comparison of endodontic treatment results at two dental schools

Endodontic treatment results were assessed in a controlled clinical study in Arhus. Undergraduate students used either Kloroperka or AH26 as sealer in a randomized fashion. The findings were compared with the results from a previous study of identical design in Oslo, which involved Kloroperka, AH26 and ProcoSol. While Kloroperka performed slightly, but significantly less well than AH26 or ProcoSol in the Oslo study, no difference was found between Kloroperka and AH26 in the present study. The overall treatment results were poorer in Arhus than in Oslo, but this might be explained by a marked difference in the preoperative diagnoses and in the technical problems associated with the teeth selected for treatment. When results of endodontic treatment carried out at different locations are compared, variations in case selection and preoperative diagnoses must be corrected for in order to obtain an adequate basis for comparison.

Usage test of four endodontic sealers in Macaca fascicularis monkeys

Root canals with vital pulps in four Macaca fascicularis monkeys were subjected to pulp extirpation and root filling with gutta-percha and sealer, either AH26, Endomethasone, Kloroperka N-phi, or ProcoSol. Observation periods 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 each observation period group and among the four material groups. Radiography indicated periapical pathosis in 6 of the 60 roots--4 at 1 month and 2 at 6 months. Periapical inflammation was observed on histopathologic examination in 17 roots--11 after 1 month and 6 after 6 months. Histologic and radiographic assessment of periapical inflammation was significantly correlated (p less than 0.01, chi 2) at the 6-month observation period. No granuloma or cyst formation was evident on histologic examination. The magnitude of the inflammatory response appeared unrelated to the endodontic sealer used, and several inflammatory foci were not related to foreign bodies in the tissues. Bacteriologic sampling showed growth in thioglycollate broth cultures in 9 of the 60 roots, but the presence of cultivable bacteria by this technique was unrelated to inflammatory changes. Histologic demonstration of bacteria was positive in 4 roots, all of which were associated with inflammatory periapical reactions. The method applied in the present study did not provide a sensitive discrimination among endodontic materials of widely different chemical composition.

In vivo and in vitro studies on soft denture materials: microbial adhesion and tests for antibacterial activity

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 subject-dependence in plaque formation on the materials was noted.

Radiographic evaluation of apical periodontitis and endodontic treatment results: a computer approach

Chronic apical periodontitis is diagnosed primarily by radiography. Whereas subjective, chairside evaluations of radiographs have serious limitations as regards accuracy of endodontic diagnosis, digitalization of radiological data allows quantification of the information obtained. In clinical practice, digitalization may improve the diagnostic sensitivity and reduce the radiation dose; in clinical endodontic research, digitalization of radiographs provides a means of unbiased and quantitative assessment of apical periodontitis. Automated measurements of the radiographic density of the periapical area have been applied in a study of the effect of different endodontic sealers on the healing of apical periodontitis. Changes in radiographic density could be detected as early as 3 weeks after completion of endodontic treatment, and the computer-based analyses provided numeric values for the progression of the healing process in the periapical region.

Effects of extensive apical reaming and calcium hydroxide dressing on bacterial infection during treatment of apical periodontitis: a pilot study

An apical dentine sampling technique was applied in order to monitor the bacteriology of the pulp canal and radicular dentine before and during treatment of teeth with chronic apical periodontitis. Twenty-three teeth with a radiographic diagnosis of apical periodontitis were studied. They were subjected to a standardized two-appointment treatment regimen of extensive apical reaming in the absence of antimicrobial agents and 1-week dressing with calcium hydroxide. Bacteriological samples were taken from the root canal at the start, and apical dentine samples at the end, of each sitting. Provision was made to allow growth of anaerobic bacteria. All root canals but one showed growth at the start of treatment. Dentine samples were positive in 14 of the 23 teeth at the end of the first appointment. Eight of the 23 canals had detectable growth from the canal at the start of the second appointment, but in sufficient numbers for quantification in only one root canal. The subsequent dentine samples were otherwise negative at the second appointment. There was a tendency for teeth causing symptoms to harbour more bacteria than symptomless teeth.

Disinfection by endodontic irrigants and dressings of experimentally infected dentinal tubules

The effect of endodontic irrigants and dressings was tested on bacteria in bovine dentin specimens experimentally infected with Enterococcus faecalis, Streptococcus sanguis, Escherichia coli, or Pseudomonas aeruginosa. Standardized, cylindrical dentin test pieces were prepared and cleaned by ultrasonic treatment with EDTA and sodium hypochlorite. The specimens were infected with the test organism for periods up to 14 days, and the degree of infection into the tubules was monitored using Brown & Brenn stain, scanning electron microscopy, and culturing of dentin dust from sequential bur samples starting from the pulpal side. E. faecalis rapidly infected the whole length of the tubules; S. sanguis required up to 2 weeks for complete infection; E. coli only penetrated to some 600 microns, even after prolonged incubation periods. P. aeruginosa infected dentin quickly, but apparently in very low numbers. E. faecalis persisted for at least 10 d after withdrawal of nutrient support, whereas the other 3 organisms died within 4 to 48 h. Endodontic medicaments were applied to infected specimen for comparison of antibacterial potency. Camphorated p-monochlorophenol was generally more efficient than Calasept, and of the irrigants tested, iodine potassium iodide appeared more potent than sodium hypochlorite or chlorhexidine. The presence of a smear layer delayed, but did not eliminate, the effect of the medicaments.

Mutans streptococci in plaque from margins of amalgam, composite, and glass-ionomer restorations

Levels of mutans streptococci in plaque samples from margins of Class II amalgam (Dispersalloy), composite (P-10), and glass-ionomer (Ketac Silver) restorations were compared. Fifty-one children, each having one of the restorations in a permanent first molar, were part of an inter-individual comparison, giving 17 restorations of each material. The age of the children, the age of the restorations, and the salivary levels of mutans streptococci were comparable in the three groups. Another seven children--each having both a composite and a glass-ionomer restoration of the same age placed on contralateral premolar or molar teeth--were part of an intra-individual comparison. The percentage mutans streptococci of total CFU count in plaque was higher on composite (mean 13.7) and amalgam (mean 4.3) than on glass-ionomer (mean 1.1) restorations in the inter-individual comparison, and higher on composite (mean 4.2) than on glass-ionomer (mean 0.4) restorations in the intra-individual comparison. In both comparisons, the differences in values between samples from glass-ionomer restorations and samples from composite or amalgam restorations were statistically significant (p less than 0.05).

Image analysis of endodontic radiographs: digital subtraction and quantitative densitometry

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 endodontic radiographs; its ability to compensate for angulation distortion of sequential exposures of individual teeth; its potential for application 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 applications. However, the specificity 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.

Adhesion of root canal sealers to bovine dentine and gutta-percha

The adhesive properties of eight root canal sealers, applied as a thin layer between a dentine and a gutta-percha surface, were investigated. Tensile bond strengths ranged from 0.02 MPa (Sealpex) to 2.38 MPa (AH26). Inspection of fractured surfaces indicated failure of adhesion to dentine (Tubli-Seal) and to gutta-percha (AH26, Diaket) as well as failure of cohesion (CRCS, Kloroperka N-O, ProcoSol, rosin chloroform, Sealapex). Pretreatment of the dentine surface with EDTA caused a significant increase in bond strength for ProcoSol, rosin chloroform, Sealapex, and Tubli-Seal.

Evaluation of alternatives to chloroform in endodontic practice

Chloroform is used in endodontics for plasticizing gutta-percha points and for facilitating removal of gutta-percha root canal fillings in need of re-treatment. Adverse health effects from exposure to chloroform have been reported, and to improve occupational health, it would be advantageous if a less hazardous solvent could replace chloroform. In this study, methylene chloride, methyl chloroform, tetrahydrofuran, xylol and eucalyptol were tested for their capacity to dissolve or soften gutta-percha points compared with chloroform. The effect of the test solvents was assessed by measuring the depth of penetration of a small indentor of fixed weight and shape into a gutta-percha disk covered with the test solution for various time periods. Chloroform showed the most pronounced effect, followed by methylene chloride, tetrahydrofuran, and methyl chloroform. When both occupational health and gutta-percha solvent capacity were considered, methyl chloroform seemed to be an interesting alternative to chloroform.

Endodontic materials

Endodontic sealing materials for permanent obturation of root canals are highly variable both in chemistry of setting and in their additives. Conventional materials are based on zinc oxide-eugenol, rosin-chloroform, or synthetic resins. These have been extensively tested for biological and technical properties. Most materials are slightly or moderately cytotoxic, and some - notably paraformaldehyde-containing materials- have been associated with clinical complications such as paresthesia of the mental and/or inferior alveolar nerve. Recently, Ca(OH)2-containing materials have been introduced with claims of improved clinical and biological performance. However, there is little documentation of the alleged benefits of new materials.

The virtual absence of comparative clinical studies on endodontic filling materials appears to be the major obstacle to critical assessment of old materials or to adequate documentation of new formulae. A recently introduced scoring system for the radiographic assessment of apical periodontitis may aid in the future testing of endodontic materials. Results with this scoring system on extensive clinical material indicate that it is possible to discriminate among endodontic materials with small differences in clinical performance.

Bacterial agglutinins in rat salivary glands: effect of glandular stimulation and calcium dependency

The secretory pattern of salivary, bacterial agglutinins was studied in the rat. The three major salivary glands were cannulated bilaterally and their secretions collected separately after parasympathomimetic and sympathetic stimulation. The bacterial aggregating activity of the secretions was tested against four strains of bacteria indigenous to the rat. Agglutinin activity was demonstrated in both parasympathomimetic and sympathetic secretions. The parotid glands tended to show the highest total output of agglutinins, with the highest titers found in parotid saliva on sympathetic stimulation. In submandibular and, particularly, parotid saliva, titers tended to increase when stimulation with pilocarpine was followed by sympathetic stimulation. In contrast, titer in sublingual saliva tended to decrease on sympathetic stimulation. When expressed as titer output per minute, sympathetic parotid secretion showed the highest agglutinin activity. Agglutinin activity appeared unrelated to total protein or to duct-derived amidolytic activity. Titers of parotid or submandibular saliva were increased 5- to 10-fold by the presence of 3.3 mM CaCl2 in the reaction mixture. By contrast, the agglutinating activity of sublingual saliva on parasympathomimetic stimulation was unaffected by extraneous CaCl2. Measurements of Ca concentration in similarly obtained rat salivary secretions did not show patterns of Ca concentration that could be related to the varying sensitivity of the agglutinating activity to Ca.

Reliability of the periapical index scoring system

Data accumulated in one methodological and two longitudinal clinical studies employing the periapical index (PAI) scoring system were analyzed to assess the usefulness and reliability of the PAI system. More than 93% of pairs of PAI scores were either identical or deviated from each other with one step only for intra- and interexaminer agreement in scoring the same radiograph as well as for intraexaminer agreement in scoring two radiographs of the same root. Untreated roots which on completion of the longitudinal studies were judged to have healthy periapices, were scored as diseased less than 3% of the time during the study. Diseased teeth were scored as healthy less than 7% of the time. The results suggest that the PAI scoring system may be used with a high degree of reliability.

In vitro infection and disinfection of dentinal tubules

An in vitro model for dentinal tubule infection of root canals was developed. Cylindrical dentin specimens, 4 mm high with a diameter of 6 mm and a canal 2.3 mm wide, were prepared from freshly extracted bovine incisors. The cementum was removed from all dentin blocks. The tubules were opened by four-minute treatments with 17% EDTA and 5.25% NaOCl before being infected with Enterococcus faecalis ATCC 29212 in yeast extract-glucose broth. Bacteria rapidly invaded the tubules. After three weeks of incubation, a heavy infection was found 400 micron from the canal lumen, and the front of the infection reached 1000 micron in some blocks. Camphorated paramonochlorophenol (CMCP) and a calcium hydroxide compound, Calasept, were tested for their disinfecting efficacy toward E. faecalis-infected dentin. Liquid CMCP rapidly and completely disinfected the dentinal tubules, whereas CMCP in gaseous form disinfected tubules less rapidly. Calasept failed to eliminate, even superficially, E. faecalis in the tubules. The method used in bacteriological sampling allowed for sequential removal of 100-micron-thick zones of dentin from the central canal toward the periphery. Control specimens were uniformly infected and yielded growth in bur samples up to some 500 microns from the surface. The model proved quite sensitive and seems suitable for in vitro testing of root canal medicaments.

Antibacterial properties of and element release from some dental amalgams

Nine commercial dental amalgams were tested for antibacterial properties in vitro. A bactericidal test on salivary bacteria, a growth inhibition test on Streptococcus mutans OMZ 176, and a time-dependent bactericidal test on Strep. mutans were used. All amalgams displayed some antibacterial properties. Dispersalloy and Revalloy were strongly antibacterial in all tests; ANA 2000 and Sybraloy killed Strep. mutans but were less potent in the salivary test and in the growth inhibition experiments. The copper amalgams, Neo-Silbrin and Cupromuc, were the most active in the salivary test but less inhibitory in the growth curve experiments. Spheraloy, Indiloy, and Amalcap showed intermediate activity in the salivary bactericidal test but were relatively weak in the growth inhibition studies. Analysis of Hg, Ag, and Cu in media from the growth inhibition studies showed release of Hg from the copper amalgams and, particularly, from Revalloy; Indiloy gave off Ag, whereas Neo-Silbrin, Cupromuc, Sybraloy, and ANA 2000 released more Cu than the other brands.

Bacteriological studies on endodontic paper points

Four brands of endodontic paper points were subjected to tests for sterility, antibacterial activity, and suitability as vehicles for bacteriological sampling procedures. No brand showed growth in the sterility assay. One brand showed weak but reproducible antibacterial activity. Recovery of viable bacteria after absorption into the points varied and appeared to depend both on the brand of point and on the bacterial strain used. One brand appeared ineffectual for clinical bacteriological sampling procedures.

Influence of antiseptic storage solutions on physical properties of endodontic guttapercha points

The effect of three commonly used antiseptic storage solutions on some physical properties of endodontic guttapercha points was studied. The solutions tested were: 70% isopropyl alcohol, 5% chloramine and 0.5% chlorhexidine. As a control solution, physiologic saline was used. There was a marked decrease in the force necessary to bend the points after 1 month. With few exceptions, the greatest decrease was seen with solutions containing alcohol, i.e. chlorhexidine and isopropyl alcohol. The difference between aqueous and alcoholic storage solutions was also noted for linear dimensional changes. Physiologic saline and chloramine hardly affected the length of the points. The decrease in stiffness may add to the difficulties when handling guttapercha points of small dimensions in curved root canals. From this point of view it is therefore recommended to avoid storage of points in antibacterial solutions. Rather, an effective surface disinfecting of the points immediately prior to use would be desirable.

Mutagenicity of endodontic sealers

Four endodontic sealer materials and some of their chemical constituents were subjected to Ames' test for mutagenicity with the Salmonella/microsome assay. Extracts of two zinc oxide-eugenol based materials and of one gutta-percha-zinc oxide-chloroform based sealer were negative in the test. Extracts of a synthetic polymer material, based on epoxy-bis-phenol A, induced mutations in Salmonella typhimurium TA 100 as did extracts of the epoxy-bis-phenol A resin alone. Formaldehyde, an active ingredient from one of the ZnO-based materials, induced mutations in both Salmonella typhimurium TA 98 and TA 100. The mutagenic activity of formaldehyde as well as of the epoxy material was reduced in the presence of rat liver microsomes.