Proposed Diagnostic Reference Levels in the Missouri/Southern Illinois Region Associated with Cone-beam Computed Tomography Use in Endodontics.

INTRODUCTION: Diagnostic reference levels (DRLs) are intended to improve patient safety and ensure that patient ionizing radiation doses are as low as reasonably achievable. The purpose of this dosimetry study was to establish regional DRL levels for cone-beam computed tomography (CBCT) imaging for specialty endodontics. Another aim was to compare phantom-measured ionizing radiation dose index 1 (DI1) index doses to the manufacturer-provided dose area product (DAP) radiation output values for each of the CBCT machines studied, to ascertain their degree of correlation. DAP refers to the dose area product, a measure of radiation dose monitoring which represents the dose within the beam times the area within the beam at that position. METHODS: A thimble ionization chamber and polymethyl methacrylate phantom were used to obtain DI1 values using the SEDENTEXTCT method from 21 different CBCT units. DRLs were calculated based on the 75th percentile (third quartile) of the median output values. RESULTS: The proposed DRL from the CBCT units surveyed has a DAP value of 838 mGy cm2 and a DI1 value of 3.924 mGy. DAP versus DI1 values of 500.6 mGy cm2 versus 2.006 mGy, and 838 mGy cm2 versus 3.906 mGy represented the third quartile of the median values for the 4-cm × 4-cm and 5-cm × 5-cm field of views (FOVs), respectively. CONCLUSIONS: The DI1 and DAP values strongly correlated when 3 outlier CBCT machines (J Morita Veraview X800) using a novel 360° (full rotation) acquisition mode were excluded. The importance of selectable exposure parameters as directly related to ionizing radiation output is illustrated among the CBCT units surveyed. Although the actual FOV that is selected is ultimately dictated by the specific clinical requirements, a 4-cm × 4-cm FOV is recommended for specialist endodontics practice, whenever clinically practical, based on the decreased ionizing radiation output, as compared to that from a 5-cm × 5-cm FOV.

Quantitative Performance Characterization of Radiation Dose for the Carestream CS9600 Cone-Beam Computed Tomography Machine.

INTRODUCTION: Cone-beam computed tomography (CBCT) machines produce relatively low levels of harmful ionizing radiation, as compared with the computed tomography devices used in medical practices. The Carestream CS9600 CBCT imaging device has been recently introduced into the marketplace, and the manufacturer reports the use of an increased x-ray tube voltage (120 kVp) for the device, along with a reduced patient dose that is achieved using added filtration. Independent dosimetry studies are performed to ensure appropriate radiation exposure dose levels are within recommended safety guidelines.The purpose of this study is to independently evaluate and measure the radiation exposure dose performance parameters of the CS9600 CBCT, including its multiple field of view, exposure settings, and filtration options. METHODS: A thimble ionization chamber and PMMA phantom were used to characterize dose index using the established SEDENTEXTCT evaluation method. RESULTS: The phantom-obtained radiation dose index measures ranged from 0.128782-13.848 milligrays (mGy) for the various scanning options evaluated. The field of view, type of filter used, and phantom size all had a direct impact on the relationship between the experimentally obtained dose index measures and the dose area product values reported by the manufacturer. CONCLUSIONS: A strong linear correlation was observed between the experimentally obtained dose index measures and the manufacturer-reported dose area product values. The 0.7 mm Cu filter that has been added to the CS9600 reduced the exposure dose index measures even with the x-ray tube kilovoltage peak (kVp) being increased to 120 kVp, as compared with the 0.15 mm Cu filter at 90 kVp.

Satisfaction of Search in Periapical Radiograph Interpretation.

INTRODUCTION: Several studies in radiology and medicine have evaluated the satisfaction of search (SOS) error effect in chest radiography, abdominal radiography, osteoradiology, and patients with multiple trauma. No research to date has been published evaluating the possible existence of the SOS error phenomenon made during dental periapical radiograph interpretations. The purpose of the present pilot study was to determine if an SOS error effect exists when dental clinicians interpret periapical radiographs. The null hypothesis was that the detection accuracy will be the same or will improve for the detection of native lesions in the presence of an added abnormality. The alternative hypothesis is that there will be a decrease in detection accuracy for native lesions in the presence of an added abnormality. METHODS: Six images were selected to be part of the present experiment. One of the 6 images served as the positive control, and another image served as the negative control. Four images, each including a single subtle carious lesion, were selected to represent the experimental images. The single subtle carious lesion present within the 4 experimental radiographs served as the native pathology, and an abnormality such as a periapical radiolucency, resorption, inadequate nonideal root canal obturation material, or recurrent carious lesion was artificially inserted into the image as the added pathology. Thus, the second set of images consisted of the same 4 images containing the native pathology including an added pathology that was inserted into the image using Adobe Photoshop CS6 (Adobe, Inc, San Jose, CA). Purposive sampling was obtained from 16 examiners including residents from endodontics and periodontics as well as alumni and faculty from the Saint Louis University Center for Advanced Dental Education, St Louis, MO. Each observer participated as a subject during 2 time-separated sessions. Each session was separated by a minimum period of 3 months' duration in order to prevent memory bias. Before starting each interpretation session, the participants were given verbal instructions. Subjects were instructed to provide a location (by tooth number), identify, and rate the presence of all suspected pathology using a Likert scale of 1-5 (1: definitely normal, 2: probably normal, 3: possibly abnormal, 4: probably abnormal, and 5: definitely abnormal). In the second session, the radiographs that were initially presented containing only the native lesion were presented again with the added abnormality, and vice versa. The observers' reports and confidence ratings were recorded and analyzed. Ratings of 3-5 were considered as being positive for the presence of pathology. RESULTS: A true SOS error occurs when the presence of the native lesion is reported correctly without an added abnormality but is not reported (missed) in the presence of an added abnormality. In our study, a true SOS error occurred in 13 of the 64 interpretation sets (20.31%). There was a total of 64 expected native lesions present within the 4 native images viewed by 16 observers. In the 4 added images, there was a total of 64 expected added findings. In the images containing only native lesions, the observers reported 30 of the 64 expected native lesions. In the images containing an artificially added abnormality, the observers reported 58 of the 64 expected added abnormalities and 25 of the 64 expected native lesions. Observers reported fewer native lesions in the presence of an added abnormality. CONCLUSIONS: The current investigation demonstrated the existence of the SOS effect during periapical radiographic interpretations. In 20.31% of interpretations, a true SOS error occurred. This study is clinically relevant because it can help clinicians in reducing false-negative errors made during radiographic interpretation, thus preventing misdiagnosis.

Visual Fixation and Scan Patterns of Dentists Viewing Dental Periapical Radiographs: An Eye Tracking Pilot Study.

INTRODUCTION: The visual search patterns of dentists and the areas that attract their attention when interpreting dental periapical radiographs are currently unknown. This research identifies areas and patterns of visual fixation when observing dental periapical radiographs. METHODS: In an observational study using eye tracking technology and a convenience sample of 44 observers, the interpretations of 4 dental periapical radiographs were recorded using Camtasia Software (TechSmith, Okemos, MI) with a gaze tracking "bubble" denoting where within the radiograph the observers' eyes gazed. The recorded observations included the scanning pattern, the area of first fixation, and revisits of areas. Also noted was whether the area of first fixation or revisit was radiopaque, radiolucent, or of normal radiodensity and whether it was a coronal or radicular area. RESULTS: The first fixation is more likely to be an area of high contrast that is either radiopaque or radiolucent compared with areas that were normal or of average gray scale. Significantly more revisits occurred on areas that were radiopaque and located in the radicular area. Of the 4 categorized scanning patterns, tooth by tooth scanning predominated. CONCLUSIONS: When interpreting dental periapical radiographs, significantly more observers initially fixated on areas of the radiograph that were of high contrast (ie, radiopaque or radiolucent) compared with "normal areas." A tooth by tooth scanning pattern was most commonly used.

Intraradicular Appearances Affect Radiographic Interpretation of the Periapical Area.

INTRODUCTION: No research exists evaluating the influences of specific variables such as obturation length, radiodensity, or the presence of voids on interpretation of periradicular area. The purpose of this study was to evaluate the effects of obturation length, radiodensity, and the presence of voids on the radiographic interpretations of periapical areas. METHODS: In a Web-based survey, 3 test image groups of variable obturation lengths, radiodensities, and numbers of voids were presented to observers for evaluation of the periapical areas. Intracanal areas of the images were altered by using Adobe Photoshop to create 3 test image groups. Each observer reviewed 2 control images and 1 image from each test image group. Responses were recorded in a 5-point Likert-type scale. Within each test image group, the periapical areas were identical. Kruskal-Wallis, Mann-Whitney U, and Cliff's delta statistical tests were used to analyze results. RESULTS: A total of 748 observer responses were analyzed. Significant differences (P ≤ .01) in the median Likert-type scale responses were identified between the following paired groups: 3 mm short and 1 mm short, 3 mm short and flush, lower radiodensity and higher radiodensity, lower radiodensity and intermediate radiodensity, no voids and several voids, and several voids and single void. Effect sizes ranged from 0.19 to 0.41. CONCLUSIONS: Significant differences were noted within all 3 test image groups: length, radiodensity, and presence of voids. Length of obturation had the largest effect on interpretation of the periapical area, with the 3 mm short radiographic obturation length image interpreted less favorably.

Coronal and Intraradicular Appearances Affect Radiographic Perception of the Periapical Region.

INTRODUCTION: The influence of the radiographic appearances of the coronal and intraradicular areas on periapical radiographic interpretation has been minimally evaluated in dentistry and endodontics. The purpose of this study was to evaluate the effects that the coronal and intraradicular radiographic appearance has on endodontists' radiographic interpretations of periapical areas. METHODS: In a split-group study design using an online survey format, 2 pairs of digital periapical radiographic images were evaluated by 2 groups (A and B) of endodontist readers for the presence of a periapical finding. The images in each pair were identical except that 1 image of each image pairs had coronal restorations and/or root canal fillings altered using Adobe Photoshop software (Adobe Systems, San Jose, CA). The periapical areas were not altered. Using a 5-point Likert scale, the endodontist readers were asked to "Please evaluate the periapical area(s)." A Mann-Whitney U test was used to statistically evaluate the difference between the groups. Significance was set at P < .01. RESULTS: There were 417 readers in group A and 442 readers in group B. The Mann-Whitney U test showed a significant difference in the responses between the groups for both image pairs (P < .01). CONCLUSIONS: Because the periapical areas of the image pairs were unaltered, the differing coronal and intraradicular areas of the radiographs appear to have influenced endodontists' interpretations of the periapical areas. This finding has implications for all radiographic outcome assessments.

The effect of the irrigant QMix on removal of canal wall smear layer: an ex vivo study.

The aim of this study is to evaluate the effectiveness over application time of different formulations of a novel endodontic irrigant (QMix™ 2in1) composed of a polyaminocarboxylic acid chelating agent, a bisbiguanide antimicrobial agent, a surfactant and deionized water to remove the root canal smear layer and expose patent dentinal tubules compared to a standard solution of 17% EDTA. Eighty human tooth roots from extracted, single-rooted teeth were instrumented (size 40.06) using 0.2 mL of sodium hypochlorite (6.15%) between each file size with a 3 mL water rinse after final instrumentation. Eight groups of 10 roots were irrigated with 3 mL of different formulations of QMix: QMix A, QMix B, and QMix C, or 17% EDTA for 60 and 90 s, respectively, then rinsed with 5 mL of sterile water. The roots were irrigated using a standard irrigation syringe and a 30 ga side-vent needle with an apical-coronal motion to within 1 mm of the working length. The coronal, middle and apical thirds of one canal surface of each root was evaluated at 1000× using scanning electron microscopy. The presence of smear layer was scored using a 5-point scale. Data were analyzed with the Kruskal-Wallis rank sums test, the Steel-Dwass, all-pairs comparison test, and the Steel method (with control) test. Irrigant type was highly significant (p < 0.007). Combined 60 and 90 s exposure data indicated QMix A (p = 0.014) and QMix C (p = 0.028) were superior to EDTA. While at the 90 s exposure time, smear layer removal by solutions QMix A (p = 0.043), QMix B (p = 0.018), and QMix C (p = 0.011) was superior to EDTA. All irrigants removed smear layer more effectively at the coronal and middle levels compared to the apical level (p < 0.001). Analysis showed all three QMix formulations were superior to EDTA in smear layer removal and exposure of dentinal tubules in the root canal system in single-rooted teeth.

An ex vivo comparison of digital radiography and cone-beam and micro computed tomography in the detection of the number of canals in the mesiobuccal roots of maxillary molars.

INTRODUCTION: The purpose of this study was to compare digital periapical and cone-beam computed tomography (CBCT) images to determine the number of canals in the mesiobuccal root of maxillary molars and to compare these counts with micro computed tomography (µCT), which was also used to determine canal configuration. METHODS: Digital periapical (RVG 6100), CBCT (9000 3D), and µCT images (the reference standard) were obtained of 18 hemi-maxillas. With periapical and CBCT images, 2 endodontists independently counted the number of canals in each molar and repeated the counts 2 weeks later. Teeth were extracted and scanned with µCT, and 2 additional endodontists, by consensus, determined the number and configuration of canals. The Friedman test was used to test for differences. RESULTS: In mesiobuccal roots, 2 canals were present in 100% of maxillary first molars (13 of 13) and 57% of second molars (8 of 14), and 69% (9 of 13) and 100% (8 of 8) of these exited as 2 or more foramina. There was no difference in canal counts for original and repeat reads by the 2 observers with periapical (P = .06) and with CBCT (P = .88) and no difference when CBCT counts were compared with µCT counts (P = .52); however, when periapical counts were compared with µCT counts, there was a significant difference (P = .04). CONCLUSIONS: For cadaver maxillary molars, µCT canal counts were significantly different from digital periapical radiograph counts but not different from Carestream9000 3D CBCT counts.

Localized increases in corticotropin-releasing factor receptors in pulp after dental injury.

Corticotropin-releasing factor (CRF) binds to membrane-bound CRF receptors (CRF-Rs). Among the actions mediated by activated CRF-Rs is beta-endorphin (END) release from immune cells, increasing peripheral antinociception. For assessment of inflammatory regulation of CRF-R expression, rats underwent pulp exposure of left, first mandibular molars and recovered for 6 days. Control pulpal tissue consisted of contralateral, uninjured molars and left, first mandibular molars of uninjured animals. Pulp tissue specimens were incubated with antibodies directed against CRF-R (both isoforms), neurofilament, CD45, and END. We observed (1) increases in pulp CRF-R immunoreactivity after injury, (2) increased CRF-R immunoreactivity expressed in 3 distinct zones in relation to the injury, and (3) increased CD45 and END immunoreactivity in regions surrounding the pulpal abscess. CRF-Rs might provide an additional target for novel analgesics to treat pulpal pain.

Kv1.4 subunit expression is decreased in neurons of painful human pulp.

Kv1.4, a subunit of voltage-gated K(+) channels, plays a large role in regulating neuronal excitability. The level of Kv1.4 expression is unknown in human sensory neurons innervating healthy or painful tissue. Therefore, we examined Kv1.4 immunoreactivity in axons innervating both clinically diagnosed asymptomatic and painful symptomatic human tooth pulp. Antibodies directed against Kv1.4 and PGP9.5, a protein marker for axons, was used to determine the proportion of PGP9.5 immunopositive tissue that was also immunopositive for Kv1.4. We report that on pulpal axons innervating symptomatic teeth Kv1.4 immunoreactivity, a correlate of decreased Kv1.4 expression, is significantly decreased (p < 0.0001), suggestive of a factor responsible for facilitating chronic dental pain and decreases in currents produced, such as I(A), in neurons innervating painful pulp.

Chemical modification of proroot mta to improve handling characteristics and decrease setting time.

Mineral trioxide aggregate (MTA) fulfills many of the ideal properties of a root-end filling material. However, the composition of this material often makes MTA difficult to use, a direct result of its granular consistency, slow setting time, and initial looseness. Additives used by the Portland cement (PC) industry to increase PC's plasticity and decrease its setting time were added first to PC and then to gray MTA in an attempt to improve MTA's handling characteristics, with the combination providing the best handling characteristics tested for its effect on compressive strength (for changes in the original material's properties) and decrease in setting time. An admix of 1% methylcellulose and 2% calcium chloride resulted in a mix of chemically modified MTA that, when compared with unmodified MTA, (1) handled similarly to a reinforced zinc oxide-eugenol cement, (2) gave an approximately equal compressive strength, and (3) set one third faster (57 +/- 3 minutes).

TRPM2 immunoreactivity is increased in fibroblasts, but not nerves, of symptomatic human dental pulp.

Transient receptor potential (TRP) channels function in diverse processes such as acting as second messenger systems, regulating of ionic concentrations, and aiding in thermoception. TRPM2 channels, members of the melastatin subfamily, mediate calcium influx in response to oxidative stress but during pathological states facilitate hyperexcitability and cellular necrosis via calcium excitotoxicity. We hypothesized that TRPM2 channel expression is upregulated in pulpal tissue of symptomatic teeth with signs of irreversible pulpitis. TRPM2 channel expression was significantly increased in pulp from clinically diagnosed symptomatic teeth compared with pulp from asymptomatic teeth. Additionally, increased TRPM2 expression in symptomatic pulp was the result of increased immunoreactivity in fibroblasts, whereas neural expression of TRPM2 was absent. We provide a possible mechanism explaining the association between TRPM2 channel expression with pain and necrosis. We suggest that TRPM2 channel antagonists could be administered in attempts to inhibit the progression of or even reverse pulpal degradation.

Enterococcus faecalis adhesin, Ace, mediates attachment to particulate dentin.

An enzyme linked immunosorbent assay was developed to assess E. faecalis adhesion to particulate dentin. E. faecalis, OG1RF, which expresses the collagen binding protein (Ace+), and a derivative of OG1RF, TX5256, deficient in the collagen binding protein (Ace-) were grown at 46 degrees C, necessary for in vitro expression of Ace, and at 37 degrees C. E. faecalis binding to dentin was measured at 0, 15, 30, 60, 120, and 360 minutes. Compared to TX5256 and OG1RF grown at 37 degrees C, OG1RF grown at 46 degrees C adhered significantly better at all time points except 15 minutes (p < 0.001) exhibiting maximum binding at 120 minutes (17.4% of a positive control). Type I collagen at 100 microg/ml inhibited dentin binding by OG1RF grown at 46 degrees C in both competition (p < 0.005) and displacement assays (p < 0.046). Immunoaffinity purified anti-Ace IgG at 200 microg of protein inhibited adhesion of OG1RF grown at 46 degrees C to dentin.

Biofilm formation in medicated root canals.

The hypothesis that Enterococcus faecalis resists common intracanal medications by forming biofilms was tested. E. faecalis colonization of 46 extracted, medicated roots was observed with scanning electron microscopy (SEM) and scanning confocal laser microscopy. SEM detected colonization of root canals medicated with calcium hydroxide points and the positive control within 2 days. SEM detected biofilms in canals medicated with calcium hydroxide paste in an average of 77 days. Scanning confocal laser microscopy analysis of two calcium hydroxide paste medicated roots showed viable colonies forming in a root canal infected for 86 days, whereas in a canal infected for 160 days, a mushroom-shape typical of a biofilm was observed. Analysis by sodium dodecyl sulfate polyacrylamide gel electrophoresis showed no differences between the protein profiles of bacteria in free-floating (planktonic) and inoculum cultures. Analysis of biofilm bacteria was inconclusive. These observations support potential E. faecalis biofilm formation in vivo in medicated root canals.