Fractographic analysis of separated endodontic file designs.

Endodontic rotary files are cutting instruments used to perform root canal procedures within a tooth interior. Focusing on quantitative fractographic analysis increases necessary, clinical performance understanding of file separation failure. This research employed controlled, dynamic testing to failure of commercial rotary files, analyzing the fractographic, forensic characteristics in relation to Weibull reliability determination, considering: (1) design analysis; (2) stress concentrations; (3) times to failure; (4) number of cycles to failure (NCF). Ex vivo testing included three file designs, each having constant tip size (0.035 mm), taper (0.06 mm/mm), and length (25 mm). Files were individually tested using an electric, torque-controlled handpiece, rotating within a standardized, simulated canal until fracture separation occurred. Fractographic analysis, including critical measurements, was conducted using the scanning electron microscope (SEM) (PhenomProX, PhenomWorld, NL). Weibull statistical analysis established reliability factors per design group. Fractographic analysis identified separation fractures, processing inclusions, flexural-fatigue striations, and stress concentrations at flute pitches. Calculated NCF median values (1277-EE; 899-VB; 713-PI) demonstrated significant statistical differences among groups (p < 0.001). Separated apical fragments yielded statistically significant differences (p ≤ 0.05) for varying file design groups. Weibull moduli among groups were statistically equivalent. Fractographic analysis exposed a presence of multiple failure factors in addition to defect distribution, governing cyclic fatigue failure originating at stress concentration points irrespective of file design. Fractographic analysis indicated that a change in file design, specifically at the working edges, in addition to improved surface finish, has the potential of reducing failures by lowering points of stress concentration and reducing fracture initiating surface cracks.

Accuracy of tuned aperture computed tomography in the diagnosis of radicular fractures in non-restored maxillary anterior teeth--an in vitro study.

OBJECTIVES: This study compared the accuracy of three radiographic imaging modalities for the detection of artificially induced radicular fractures on maxillary anterior teeth. METHODS: Fractures were induced in 28 of 54 maxillary incisors in 15 cadaver specimens using a distally directed force. Radiographs evaluated included conventional two-dimensional direct digital radiographs (DDI), unprocessed Tuned Aperture Computed Tomography (TACT-U) and iteratively restored TACT (TACT-IR). Eight observers recorded their findings using a five-point confidence-rating scale. Receiver Operating Characteristic (ROC) analyses were done, followed by ANOVA to test for significant effects of observers, imaging modality and fracture location. Post hoc tests were carried out in instances where ANOVA indicated significance. RESULTS: The areas under the ROC-curves (A(z)) were, respectively: DDI: 0.53; TACT-U: 0.83 and TACT-IR: 0.97. TACT-IR and TACT-U performed significantly better than DDI (P < 0.001) with TACT-IR providing a higher detection accuracy than TACT-U (P < 0.033). A difference in detection accuracy was also noted based on fracture location (P < 0.001). Tukey's post hoc analyses revealed that fractures extending beyond the middle third of the root were more accurately detected. Inter-observer agreement was 0.68, and intra-examiner agreement, 0.87 (kappa analysis). CONCLUSIONS: TACT performed significantly better than direct digital images in detecting trauma-induced radicular fractures in unrestored, maxillary anterior teeth.

An in-vitro evaluation of Kodak Insight and Ektaspeed Plus film with a CMOS detector for natural proximal caries: ROC analysis.

This study compared the diagnostic efficacy of Kodak Ektaspeed Plus film, Kodak Insight film, a newly introduced E/F-speed film, and Schick CMOS-APS digital sensor, with respect to caries detection in 92 proximal surfaces of extracted unrestored teeth, 51 of which were carious. Ground truth was evaluated histologically and the lesions classified as enamel or dentinal. Eight observers read the radiographs using a five-point confidence rating scale to record their diagnoses. Analyses using receiver operating characteristic curves revealed the areas under each curve that indicated the diagnostic accuracy (Ektaspeed Plus - 0.760, Insight - 0.778 and CMOS-APS sensor - 0.732). ANOVA revealed significant differences with respect to caries depth (p<0.031) and observers (p<0.0001). Weighted kappa analyses indicated moderate to substantial inter- and intra-observer agreement (0.42 and 0.66, respectively). The results suggest that none of the imaging modalities evaluated in this study differed in their diagnostic capabilities with respect to proximal decay detection and that the Insight film which was used with 20% less radiation exposure than Ektaspeed Plus film was as good as the other two sensors for this purpose.

Tuned aperture computed tomography to evaluate osseous healing.

Quantification of osseous healing is a challenging task, requiring expensive advanced imaging modalities. To improve diagnostic osseous imaging, we undertook this prospective study to explore the potential of Tuned Aperture Computed Tomography. Eighty defects in 20 rabbit mandibles, randomly carrying an osteoblast suspension or a polymer matrix or a combination thereof or no treatment, were imaged at 3, 6, 9, and 12 weeks post-surgery. TACT slices, iteratively restored TACT, and conventional digital radiographs were evaluated. Mean-gray-value distribution within regions of interest was correlated with histomorphometric data. Lesions treated with osteoblast/polymer-matrix delivery systems demonstrated the highest mean gray-value, while the diagnostic efficacy of TACT-IR was significantly better than that of other imaging modalities (p < 0.001). Thus, TACT is an accurate imaging modality for non-destructive quantification of osseous dynamics.

Fractal analyses of osseous healing using tuned aperture computed tomography images.

The aim of this study was to evaluate osseous healing in mandibular defects using fractal analyses on conventional radiographs and tuned aperture computed tomography (TACT; OrthoTACT, Instrumentarium Imaging, Helsinki, Finland) images. Eighty test sites on the inferior margins of rabbit mandibles were subject to lesion induction and treated with one of the following: no treatment (controls); osteoblasts only; polymer matrix only; or osteoblast-polymer matrix (OPM) combination. Images were acquired using conventional radiography and TACT, including unprocessed TACT (TACT-U) and iteratively restored TACT (TACT-IR). Healing was followed up over time and images acquired at 3, 6, 9, and 12 weeks post-surgery. Fractal dimension (FD) was computed within regions of interest in the defects using the TACT workbench. Results were analyzed for effects produced by imaging modality, treatment modality, time after surgery and lesion location. Histomorphometric data were available to assess ground truth. Significant differences (p < 0.0001) were noted based on imaging modality with TACT-IR recording the highest mean fractal dimension (MFD), followed by TACT-U and conventional images, in that order. Sites treated with OPM recorded the highest MFDs among all treatment modalities (p < 0.0001). The highest MFD based on time was recorded at 3 weeks and differed significantly with 12 weeks (p < 0.035). Correlation of FD with results of histomorphometric data was high (r = 0.79; p < 0.001). The FD computed on TACT-IR showed the highest correlation with histomorphometric data, thus establishing the fact TACT is a more efficient and accurate imaging modality for quantification of osseous changes within healing bony defects.

Imaging of mandibular trauma: ROC analysis.

OBJECTIVES: To compare the diagnostic efficacies of panoramic radiographs, mandibular trauma series, and digitized radiographs for detection of fractures of the mandible. METHODS: Fractures were induced using blunt trauma in 25 cadaver mandibles. Panoramic radiographs, digitized radiographs, and mandibular series comprising an anteroposterior view, two lateral oblique, and a reverse Towne's were used. Six observers recorded their diagnoses using a five-point confidence rating scale. The data were analyzed using receiver operating characteristic (ROC) curve analysis. RESULTS: Significant differences based on imaging modalities were found (p < 0.0015) in the area under the curves (A(z)): panoramic radiograph, 0.8762; mandibular series, 0.7521; panoramic plus anteroposterior radiographs combination, 0.8886; and digitized mandibular series, 0.7723. No observer-based differences were noted. Condylar and coronoid fractures were difficult to detect than those in other areas of the mandible (p < 0.033). Intra- and inter-observer agreements were high (kappa(w) = 0.81 and 0.76, respectively). CONCLUSIONS: Panoramic radiographs are adequate for detection of mandibular fractures. Addition of an anteroposterior view augments diagnostic accuracy.

Diagnostic accuracy of intraoral film and direct digital images for detection of simulated recurrent decay.

UNLABELLED: This study compared the diagnostic accuracy of bitewing images for detection of simulated recurrent caries using the following imaging modalities: Ektaspeed Plus film and different digital imaging system technologies comprised of a charge-coupled device (CCD) based digital imaging unit, a photo-stimulable phosphor (PSP) based unit and contrast- and brightness-enhanced PSP images. STUDY DESIGN: Twenty-four extracted posterior teeth with MOD inlay preparations were secured in models simulating a natural arrangement of teeth. Lesions were created in proximal boxes using dental burs of varying sizes. Defects were filled with wax and plaster and preparations were restored with composite or amalgam. RESULTS: Averages of receiver operating curve areas (Az) revealed diagnostic performances of Az = 0.74 for film, Az = 0.80 for CCD, Az = 0.73 for unenhanced PSP and Az = 0.64 for enhanced PSP. The differences between these means were significant (MANOVA p < 0.0001). Unenhanced PSP produced significantly poorer performance than other modalities. CCD performance was not significantly better than enhanced PSP. Lesions under radiopaque composite restorations were easier to detect, followed by those under amalgam and radiolucent composites across imaging modalities and lesion locations. Based on lesion location, those located at the buccal point angle were easiest to detect, followed by those at mid-gingival floor and lingual-point angle sites. CONCLUSIONS: Contrast and brightness-enhanced digital images enabled better signal detection and a comparable performance with film for detection of artificially induced recurrent caries.