A comparison of canal centering ability of four instrumentation techniques

The purpose of this study was to compare three engine driven (nickel-titanium) NiTi instrument systems with hand files for their effect on canal transportation. Mesial roots of mature lower first molars with separate canals were paired on the basis of curvature and morphology. Canal lengths were standardized to 11 mm from orifice to apical foramen. Profile, Lightspeed, McXIM, and Flex-R hand filing techniques respectively were randomly assigned to one of the four canals of each tooth pair. The roots were mounted and sectioned at 1 mm, 3 mm, and 5 mm from working length using a modified Bramante technique. All sections were video imaged preoperatively after instrumentation to size #30 and after final instrumentation to size #40. The images were computer analyzed for changes in canal area and centering at each stage of instrumentation. Preparation time was also recorded. Data were analyzed using ANOVA. The NiTi systems remained better centered in the canal than stainless steel hand files. There were no significant differences among the NiTi systems at any level. The difference between hand filing and the NiTi techniques was more pronounced at size #40 than at size #30. The NiTi systems were all significantly faster than hand filing. No significant differences in preparation were found between the NiTi systems when canals were instrumented to the size nearest #40.

Comparison of ultrasonic and high-speed-bur root-end preparations using bilaterally matched teeth

The purpose of this study was to compare ultrasonic and high-speed-bur root-end preparations. Seventy-six roots from 29 bilaterally matched pairs of human teeth in cadavers were used in this study. In group 1 ultrasonic preparations were made in 38 roots and filled with amalgam. In group 2 high-speed bur preparations were made in 38 roots and filled with amalgam. The size of the bony crypt was measured and the teeth were extracted and radiographed mesial-distally and buccal-lingually. None of the root-end preparations resulted in root perforation. The mean mesial-distal minimum depth of ultrasonic and high-speed bur preparations were 2.11 mm and 1.39 mm, respectively. The mean buccal-lingual minimum depth of preparation was 2.51 mm for the ultrasonic and 2.05 mm for the high-speed bur preparations. The depth of the ultrasonic preparations was significantly greater for both measurements. A significantly greater bevel angle was associated with the bur preparations, 35.1 degrees versus 16.0 degrees for the ultrasonic preparations. The incidence of ultrasonic root-end preparations deviating from the uninstrumented canal spaces was found to be 2.6%. All bur root-end preparations were at an acute angle to the long axis of the root. The bony crypt size for bur preparations was significantly greater than that for ultrasonic preparations.

Demineralization of resected root-ends with methylene blue dye

OBJECTIVES

This study evaluated the ability of methylene blue solutions of different concentration, pH, and time exposure to remove the smear layer from resected root-ends.

STUDY DESIGN

Resected root-ends were treated with either 2% methylene blue dye for intervals of 5 to 11 minutes or 1% methylene blue for 7 to 9 minutes and examined with a scanning electron microscope for smear layer removal. Two minute applications of saline solution and 50% citric acid served as controls.

RESULTS

All methylene blue solutions were found to be ineffective in removing the smear layer at all time intervals tested. An experimental solution of 1% methylene blue in 50% citric acid was found to predictably remove the smear layer during a 2 minute application and retained all the favorable staining characteristics of the dye. Fifty percent citric acid solutions applied for 3 minutes appeared to overdemineralize the root-end and gave poorer results than 2 minute applications.

CONCLUSIONS

Smear layer removal was pH dependent. Methylene blue solutions are clinically unsuitable for smear layer removal.

Evaluation for cracks associated with ultrasonic root-end preparation of gutta-percha filled canals

Many clinicians use ultrasonics for root-end preparations. The purpose of this study was to evaluate resected root-end surfaces of bilaterally matched human teeth for cracks before and after ultrasonic root-end preparation. Twenty matched pairs of extracted single rooted teeth were divided into two experimental groups. In group 1, root-end resection was performed on uninstrumented teeth. In group 2, root-end resection was performed after the canals were instrumented and filled with gutta-percha. All teeth in both groups received root-end preparations using ultrasonic instrumentation at low power. Two examiners evaluated the root-ends after root-end resection and again after root-end preparation using zoom magnification of 20x to 63x. The number, types, and location of cracks were mapped. There were no significant differences when gutta-percha filled roots were compared to uninstrumented roots with regard to the number or type of cracks after root-end resection or root-end preparation. In addition, there were no significant differences in the number or type of cracks following root resection and ultrasonic root-end preparation when compared to teeth with root resection alone.

Evaluation of cracks associated with ultrasonic root-end preparation

The purpose of this study was to evaluate the integrity of resected root-end surfaces of extracted human teeth after using ultrasonic tips at low or high frequencies for root-end preparation. Thirty bilaterally matched pairs of single-rooted human teeth had root-end resections using a low-speed diamond saw and were examined for root-end cracks. The matched pairs of teeth were then divided into two experimental groups, with one member of each pair being placed in each group. In group 1, root-end preparations were made with an ultrasonic tip on the lowest frequency setting. The preparations in group 2 were done on the highest power setting. Two investigators again examined the resected root-ends using a stereomicroscope at x20 to x63 and recorded the numbers, types, and location of the cracks. Three types of cracks were observed: canal cracks, intradentin cracks, and cemental cracks. There were significantly more root-ends with cracks after ultrasonic root-end preparation than after root-end resection only. In root-ends that had any cracks, significantly more canal cracks per root occurred when the ultrasonic tip was used on the high-frequency setting for root-end preparation than when the ultrasonic tip was used on the low power setting.

Evaluation of root thickness in curved canals after flaring

Root thickness in the mesial canals of lower first and second molars was compared before and after flaring by using a muffle system. Gates Glidden burs or M-Series Canal Openers were used with either a straight up-and-down motion or with an anticurvature motion. It was found that Gates Glidden burs used straight up and down removed statistically more dentin at the level of the furcation than Canal Openers used straight up and down or in an anticurvature fashion. At a level 2 mm apical to the furcation, Gates Glidden burs used in an anticurvature fashion removed statistically more dentin than any other method tested.

Practical application of infection control in endodontics

The transmission of infections in an endodontic practice is a significant concern for both patients and dental health care providers. This article offers a review and practical application of infection control methods in the practice of endodontics.

Effects of a carbon dioxide laser on human root dentin

The effects of the Luxar LX-20 CO2 dental laser on resected apical root dentin were examined using stereomicroscopy and scanning electron microscopy. The surfaces of 2-mm-thick sections of dentin from freshly extracted human teeth were exposed to CO2 laser radiation. Fluences used ranged from 2.1 to 625.0 J/cm2. The effects of the laser energy on the dentin ranged from no visible effects, to charring, cracking, cratering, and glazing. The most dramatic effect was cracking. Cracking was evident on all specimens having any visible modification of the dentin. A prototype-curved laser tip was used and compared with a standard straight tip. The curved tip did not deliver laser energy to the dentin as efficiently as a straight tip. CO2 laser radiation did not consistently obliterate dentin tubules.

Adult pulpal diagnosis. I. Evaluation of the positive and negative responses to cold and electrical pulp tests

This study investigated the positive and negative responses of 1488 teeth in 60 patients to two electric pulp testers and a cold thermal pulp test. Three subgroups of known pulpless or pulpally diseased teeth (teeth receiving root canal therapy, teeth with root canal fillings, or teeth with confirmed associated apical radiolucencies) were identified and their responses evaluated separately. Testing was performed on two tooth surfaces, the facio-occlusal and faciocervical, and on all restorations. The gingival tissue of each patient also was tested using both electrical tests. The primary findings were: (a) teeth not responding to cold and either not responding or responding at readings greater than the tissue response to electrical had a high probability of being in the known pulpless or pulpally diseased subgroups; (b) the only false positive responses to cold in the three subgroups were in multirooted teeth with probable vital tissue remaining in at least one canal; and (c) in the three subgroups, if the false positive responses to electrical that responded at levels higher than the patient's tissue response were considered to be negative responses, the difference in false positives between cold and electrical became not statistically significant (p = 0.07).

Development of chronic mandibular osteomyelitis in a miniswine model

Previous attempts to develop a reproducible model of chronic mandibular osteomyelitis have met with limited success. In this study, osteomyelitis was produced in the mandibles of eight adult Yucatan miniswine by the intramedullary application of sodium morrhuate, Staphylococcus aureus, and either polymethylmethacrylate bone cement or bone wax. At 8 weeks' postinfection, the mandibles were surgically debrided and specimens were obtained for culture. Although all of the animals developed clinical evidence of osteomyelitis that was supported by positive cultures, the original organism (S aureus) was recovered only from those animals where bone wax had been used to seal the cortical defects. This animal model may be useful for evaluating newer treatment modalities for chronic osteomyelitis.

Efficacy of several concentrations of sodium hypochlorite for root canal irrigation

Sodium hypochlorite (NaOCl) has been recommended for irrigation during root canal preparation. This investigation used scanning electron microscopy to examine instrumented and uninstrumented surfaces in the middle third of root canals following the use of several concentrations of NaOCl (5.25%, 2.5%, 1.0%, and 0.5%). NaOCl was delivered with either an endodontic irrigation needle or an ultrasonic device. All of the concentrations of NaOCl with either delivery system were very effective in flushing out loose debris from the root canals. A smear layer with some exposed dentinal tubules was seen on all instrumented surfaces regardless of concentration of NaOCl or irrigation device. NaOCl in concentrations of 5.25%, 2.5%, and 1% completely removed pulpal remnants and predentin from the uninstrumented surfaces. Although 0.5% NaOCl removed the majority of pulpal remnants and predentin from the uninstrumented surfaces, it left some fibrils on the surface.

Histomorphometric comparison of canals prepared by four techniques

Numerous methods of root canal preparation have been recommended and used by clinicians. This study used histomorphometrics to determine the area of root canal preparations using four currently popular techniques. Clinicians that were highly skilled in each technique prepared curved canals in acrylic blocks. Each clinician described this technique and discussed the technique with regard to the use of acrylic blocks as compared with dentin. Analysis of the areas of the root canals after preparation revealed a significant difference among the groups. The mean areas after treatment were step-back technique, 17.33 mm2; Cavi-Endo technique, 15.87 mm2; Canal Master technique, 13.56 mm2; and balanced force technique, 17.31 mm2. Photographs of the blocks used in the study were included for inspection by the reader.

Experimentally induced infection by oral anaerobic microorganisms in a mouse model

A mouse model was developed to study the abscessogenic potential of pure and mixed cultures of oral anaerobes associated with infections of endodontic origin. Maximum subcutaneous lesions were seen on their backs between 3 and 14 d after inoculation. Strains of Fusobacterium nucleatum, Peptostreptococcus anaerobius, and Veillonella parvula were pathogenic in pure culture. A mixed culture of F. nucleatum with either Porphyromonas gingivalis or Prevotella intermedia was significantly more pathogenic than F. nucleatum in pure culture. Histopathological examination of tissue sections from control mice injected with India ink in the medium demonstrated a pathway of particulate migration from the backs of the mice to their abdomen.

Serum IgG reactive with oral anaerobic microorganisms associated with infections of endodontic origin

Numerous species of bacteria have been implicated with infections of endodontic origin. The purpose of this study was to compare the levels of serum IgG antibodies reactive with a panel of 10 oral anaerobic microorganisms implicated in infections of endodontic origin. Serum samples were collected from 4 patient groups that included healthy patients without endodontic or periodontal disease, patients with chronic adult periodontal disease, patients with endodontic disease and patients with combined endodontic-periodontal disease. When Prevotella intermedia was allowed to react with sera from the 4 patient groups, significant pairwise differences were shown between the healthy group and each of the other 3 groups. In addition, there was a significant difference between the periodontal disease group and the combined endodontic-periodontal disease group. When Porphyromonas gingivalis was allowed to react with sera from the 4 patient groups, significant pairwise differences were shown between the healthy group and the periodontal disease group, the healthy group and the combined endodontic-periodontal disease group, the endodontic disease group and the periodontal disease group and the endodontic disease group and the combined endodontic-periodontal disease group. The results of this investigation support other studies that associate P. intermedia with both endodontic disease and chronic adult periodontal disease. The results also support studies that implicate P. gingivalis as a periodontopathogen.

Microbiologic and pathologic aspects of endodontics

Oral microorganisms, either directly or indirectly, produce the majority of cases of pulpal and periapical disease. Because microorganisms play such an important role in the pathogenesis of pulpal and periapical disease, a fundamental understanding of the disease process is important. Culture studies have identified infections of endodontic origin as being polymicrobial and predominantly anaerobic. Although several species of bacteria have been associated with infections of endodontic origin, there is no absolute correlation with signs and symptoms. The use of immunologic studies in addition to traditional microbiologic studies provides a better understanding of the mechanisms involved in the pathogenesis of pulpal and periapical disease.

Bacteria in the apical 5 mm of infected root canals

Ten freshly extracted teeth which had carious pulpal exposures and periapical lesions contiguous with the root apex were placed inside an anaerobic chamber and the apical 5 mm of the root canals cultured. In addition to anaerobic incubation, duplicate cultures were incubated aerobically. Fifty strains of bacteria from the 10 root canals were isolated and identified. The most prominent bacteria cultured from the 10 root canals were Actinomyces, Lactobacillus, black-pigmented Bacteroides, Peptostreptococcus, nonpigmented Bacteroides, Veillonella, Enterococcus faecalis, Fusobacterium nucleatum, and Streptococcus mutans. Of the 50 bacterial isolates, 34 (68%) were strict anaerobes. This study demonstrates the presence of predominantly anaerobic bacteria in the apical 5 mm of infected root canals in teeth with carious pulpal exposures and periapical lesions.

Reactivity of IgG from explant cultures of periapical lesions with implicated microorganisms

The presence of IgG in periapical inflammatory lesions suggests that immune responses participate in the disease process. The purpose of this investigation was to study the reactivity of IgG from the supernatant fluids of explant cultures of periapical lesions with microorganisms implicated in infections of endodontic origin. Ninety periapical lesions that had been contiguous with the apex of a root were removed and maintained in explant cultures. A dot-enzyme-linked immunosorbent assay (dot-ELISA) was used to demonstrate the presence of IgG in the supernatant fluids of the explant cultures reactive with a panel of microorganisms associated with infections of endodontic origin. The percentages of reactivity by dot-ELISA follow: Bacteroides intermedius (84%), B. buccae (12%), Porphyromonas (Bacteroides) gingivalis (50%), P. endodontalis (58%), P. asaccharolyticus (17%), Peptostreptococcus micros (44%), P. anaerobius (26%), Eubacterium alactolyticum (34%), Fusobacterium nucleatum (14%), and Actinomyces israelii (6%). At least one of the three species of B. intermedius, P. gingivalis, or P. endodontalis tested gave a positive dot-ELISA with 89% of the supernatant fluids from explant cultures of periapical lesions. A lack of cross reactivity of IgG in supernatant fluids from explants of periapical lesions was demonstrated for the four strains of black-pigmented Bacteroides/Porphyromonas by dot-ELISA.

Biosynthesis of IgG in periapical lesion explant cultures

The presence of immunoglobulins has been demonstrated in periapical inflammatory lesions associated with endodontic disease. The purpose of this study was to determine if IgG is synthesized in vitro in explant cultures of untreated periapical inflammatory lesions and to determine the level of IgG in isolated samples. Periapical lesions associated with infected root canals were removed from the roots and cultured in tissue culture medium containing tritiated amino acids. Supernatant fluids from the explant tissue cultures were passed through staphylococcal protein A affinity columns to isolate IgG. When the staphylococcal protein A eluents (24-h samples) from six periapical lesions were used in double diffusion in agarose assays, the presence of IgG was demonstrated in all the samples. Radial immunodiffusion assays to quantitate the IgG in staphylococcal protein A eluents showed that the levels of IgG detected in each successive daily supernatant fluid always decreased or else fell below the lower limits of detection. The in vitro biosynthesis of IgG in explant cultures of periapical lesions was demonstrated by the incorporation of tritiated amino acids into isolated IgG.

Detection of immunoglobulins from explant cultures of periapical lesions

The presence of immunoreactive cells in periapical inflammatory lesions suggests that immune responses participate in the disease process. The purpose of this study was to determine the presence and concentration of immunoglobulins in the supernatant fluids of explant cultures of periapical lesions. Ninety periapical lesions that had been contiguous with the apex of a root were removed and maintained in explant cultures for 96 h. Tissue culture medium was replenished at 24, 48, 72, and 96 h. Double diffusion in agarose assays demonstrated the presence of IgG in 100% of the 24-h supernatant fluids and IgA in 65% of the 24-h supernatant fluids. However, IgM was not detected. Radial immunodiffusion assays were used to detect and quantitate IgG, IgA, and IgM in samples of 24-h supernatant fluids from 90 explant cultures. IgG was the predominant immunoglobulin followed by IgA. A radioimmunosorbent test was used to detect and quantitate IgE in samples of 24-h supernatant fluids from 90 explant cultures. Forty of the 90 supernatant fluids contained measurable IgE. All detected immunoglobulins decreased in concentration in daily supernatant fluids with time (24, 48, 72, and 96 h) in the culture.