Pixel intensity and fractal dimension of periapical lesions visually indiscernible in radiographs.

INTRODUCTION: The purpose of the study was to analyze pixel intensity (PI) and fractal dimension (FD) values in radiographs of chemically created but visually undetectable periapical lesions. METHODS: Artificial lesions were created by applying 70% perchloric acid to the sockets of left and right first premolars in 12 cadaver mandibles. For preparation of relatively small lesions, the acid was applied for 30 and 60 minutes. Before and after each acid application, radiographs were taken (60 kVp, 7 mA, and 1.5 mm Al equivalent filtration for 0.12 second) with storage phosphor plates. An optical bench was used to standardize projection geometry. Image plates were scanned immediately after exposure, and the acquired images were saved uncompressed in TIF format. Six observers evaluated the images by using a 5-grade scale, and the images scored as "definitely absent" by all observers were used for the calculations of PI and FD. Box-counting FDs and differences in mean PI were computed for regions of interest at the apical areas of each premolar. Repeated-measures analysis of variance, Tukey test, and Pearson correlation coefficient test were used for statistical analysis. RESULTS: A significant difference was found in FD values after both acid application periods (P < .05), whereas a difference in PI was detected only in images obtained after 60-minute acid application (P < .05). There was a negative correlation between FD and PI values (-0.754, P < .05). CONCLUSIONS: Calculation of FD can be a tool for the early detection of periapical lesions given the presence of baseline radiographs.

Otosclerosis: anatomy and pathology in the temporal bone assessed by multi-slice and cone-beam CT.

OBJECTIVE: To assess the use of cone beam computed tomography (CBCT) compared with multi-slice computed tomography (MSCT) in otosclerosis, with special emphasis on middle- and inner-ear anatomy. STUDY DESIGN: Prospective study. PATIENTS: Twenty patients who underwent a stapedectomy 30 years ago were selected on the basis of bone conduction threshold values. Their mean age was 65 years (range, 48-76 yr). INTERVENTION: All patients underwent CBCT and MSCT with a slice thickness of 0.5 to 0.6 mm. MAIN OUTCOME MEASURES: Sixteen middle- and inner-ear anatomic structures and stapedial prostheses were analyzed by visual grading analysis. To assess critical reproduction and thereby the clinical applicability of CBCT, a dichotomization was made. Assessment of otosclerotic foci was performed using a grading system dividing the lesions in; (1) sole fenestral lesions, (2) retrofenestral lesions with or without fenestral lesions and (3) severe retrofenestral lesions. RESULTS: The 16 anatomic structures were clearly reproduced by both imaging techniques. However, there was an interobserver variation in judging the superiority of 1 method in favor of the other. Otosclerotic lesions were diagnosed in 80/95% using MSCT and 50/85% using CBCT (evaluators 1 and 2, respectively). Retrofenestral lesions were diagnosed in 5 of 10 of ears with severe-to-profound hearing loss, whereas no retrofenestral lesions were diagnosed in the 10 ears with mild-to-moderate hearing loss. The stapedial prostheses were adequately or very well reproduced by both methods. CONCLUSION: CBCT is a new imaging technique with a considerably lower radiation dose than conventional MSCT. Our study indicates that CBCT is suitable and, in many ways, equivalent to MSCT, for temporal bone imaging in otosclerosis.

Cone beam computed tomography evaluations of marginal alveolar bone before and after orthodontic treatment combined with premolar extractions.

Using cone beam computed tomography (CBCT) we investigated the distance between the cemento-enamel junction (CEJ) and the marginal bone crest (MBC) at buccal, lingual, mesial, and distal surfaces of incisors to first molars in adolescents before (baseline) and after extractive orthodontic treatment (study end point). Patients with Class I malocclusion, crowding and an overjet of ≤ 5 mm were examined with a CBCT unit using a 60 × 60-mm field of view and a 0.125-mm voxel size. Large differences in marginal bone height were found at baseline, particularly between tooth surfaces. There was a slight correlation between age and CEJ-MBC distance. From baseline to the study end point, large bone-height changes among teeth and tooth surfaces could be seen. Lingual surfaces, followed by buccal surfaces, showed the largest changes. Eighty-four per cent of lingual surfaces of mandibular central incisors exhibited a bone-height decrease of > 2 mm. The bone-height decrease was larger at lingual surfaces in the mandible than in the maxilla, and larger in girls (mean=1.8 mm) than in boys (mean=1.5 mm). Fewer than 1% of proximal surfaces exhibited changes of > 2 mm. It is unknown whether the changes in marginal bone height are transitory. A high-quality CBCT technique may help to determine this by providing a deeper insight into the long-term side effects of orthodontic treatment.

Does a combination of two radiographs increase accuracy in detecting acid-induced periapical lesions and does it approach the accuracy of cone-beam computed tomography scanning?

INTRODUCTION: The purpose of this study was to determine whether the use of a combination of 2 images (storage phosphor plates [SPPs] and F-speed films [Eastman Kodak, Rochester, NY]) with a 10° difference in horizontal beam angulation resulted in better detectability of chemically created periapical defects than when only 1 image was used and whether a detectability as good as that achieved by limited cone-beam computed tomography (LCBCT) scanning could be achieved. METHODS: Lesions were created by 1, 1.5, and 2 hours of acid application apical to extracted teeth in jaw specimens. After repositioning, teeth were radiographed with Accu-I-Tomo LCBCT, Digora Optime SPP system, and F-speed films. The SPPs and films were exposed at 0° and 10° horizontal angulations. The diagnostic accuracy (Az) was compared using 2-way analysis of variance; pair-wise comparisons were performed using the post hoc t test. Kappa was used to measure interobserver agreement. RESULTS: A combination of 2 exposures with a 10° difference in horizontal angulation caused an increase, although not statistically significant, in the accuracy of both films and SPPs for all acid durations (P > .05) compared with when only 1 exposure was used. The accuracy did not approach that of LCBCT. CONCLUSIONS: Using a combination of 2 exposures instead of 1 did not significantly increase the accuracy in detecting acid-induced lesions at the apices of single-rooted premolars. The accuracy of LCBCT was superior.

Apical root resorption during orthodontic treatment. A prospective study using cone beam CT.

OBJECTIVE: To investigate the incidence and severity of root resorption during orthodontic treatment by means of cone beam computed tomography (CBCT) and to explore factors affecting orthodontically induced inflammatory root resorption (OIIRR). MATERIALS AND METHODS: CBCT examinations were performed on 152 patients with Class I malocclusion. All roots from incisors to first molars were assessed on two or three occasions. RESULTS: At treatment end, 94% of patients had ≥1 root with shortening >1 mm, and 6.6% had ≥1 tooth where it exceeded 4 mm. Among teeth, 56.3% of upper lateral incisors had root shortening >1 mm. Of upper incisors and the palatal root of upper premolars, 2.6% showed root shortenings >4 mm. Slanted surface resorptions of buccal and palatal surfaces were found in 15.1% of upper central and 11.5% of lateral incisors. Monthly root shortening was greater after 6-month control than before. Upper jaw teeth and anterior teeth were significantly associated with the degree of root shortening. Gender, root length at baseline, and treatment duration were not. CONCLUSION: Practically all patients and up to 91% of all teeth showed some degree of root shortening, but few patients and teeth had root shortenings >4 mm. Slanted root resorption was found on root surfaces that could be evaluated only by a tomographic technique. A CBCT technique can provide more valid and accurate information about root resorption.

Sleeping implant in the temporal bone: report of a case with 20-year follow-up.

BACKGROUND: There is limited knowledge of the long-term fate of "sleeping" or nonloaded implants in the temporal bone. PURPOSE: This article describes the fate of a fixture installed in the temporal bone that remained unloaded for 20 years. PATIENT AND METHODS: A 25-year-old male with hemifacial microsomia had three osseointegrated implants installed for an auricular episthesis and bone-anchored hearing aid (BAHA) in the left temporal bone in 1988. Two of the implants for the ear episthesis were activated the same year, but the fixture for the hearing aid was not uncovered until 2008. When the patient experienced hearing problems at his office, he wanted to reactivate the sleeping implant. An audiogram showed a maximum conductive hearing loss with good preserved cochlear function. Before reactivation, an Accuitomo three-dimensional, cone beam computed tomography was performed. Resonance frequency analysis (RFA) using the Ostell technique was done when the implant was uncovered. RESULTS: Preoperative x-ray investigation showed the sleeping implant to be well integrated in the temporal bone, covered with 1 mm bone, and with no signs of resorption. Geometric measurements correlating to the two loaded implants showed the sleeping implant to be positioned too close to these to be able to anchor a BAHA without interference with the episthesis. Surgical exploration was done to analyze the implant. The clinical status correlated well to that diagnosed from the x-ray investigation. RFA revealed the implant to be well integrated. A new fixture and abutment for BAHA was installed in the temporal line and activated 2 months after surgery. The patient is today supplied with a BAHA. CONCLUSION: It seems possible to use sleeping implants in the temporal bone even 20 years after installation.

Characteristics of patients referred for Cone Beam Computed Tomography (CBCT) of ectopically erupting maxillary canines.

The aim was to study the characteristics of patients referred for tomographic examinations of maxillary canines suspected of ectopic eruption and evaluate whether the criteria used for referring the patients could be considered appropriate. During a 1-year-period all patients (n=63) referred for tomographic examinations of ectopically erupting maxillary canines, when intra-oral x-ray examinations were insufficient to describe the position of the canine and the conditions at adjacent teeth, were examined by means of Cone Beam Computed Tomography (CBCT). There was a statistically significant overrepresentation of girls (63.5%) among the referred patients. The mean age for the girls was 146.0 +/- 22.2 months and for the boys 151.8 +/- 17.8 months, a statistically non-significant difference. In total, 91 maxillary canine sites were examined and in 33 of the examined sites (36%) a resorption was found in the root surface of an adjacent tooth, in the vast majority the lateral incisor. Since more than one tooth was occasionally affected the total number of resorptions was 38 of which 14 had reached the pulp (37%). Considering the frequency of teeth, adjacent to ectopically erupting maxillary canines, that were affected by resorptions it can be concluded that the referral criteria used were appropriate. Given theyoung age of the patients it can be recommended that tomography should be performed with CBCT techniques that permit the examination of small volumes and result in high quality images.

Imaging of osseointegrated implants in the temporal bone by accuitomo 3-dimensional cone beam computed tomography.

OBJECTIVE: Follow-ups of osseointegrated implants in the temporal bone have been limited to clinical stability and resonance frequency measurements. Standard computed tomographic scanning is restricted because of the high radiation doses to the brain and the presence of disturbing metal artifacts. The present study was undertaken to evaluate the use of cone beam computed tomography preoperatively and postoperatively. STUDY DESIGN: Prospective investigation of patients intended for implant surgery and patients participating in a follow-up protocol. SETTING: Tertiary referral center. PATIENTS AND METHODS: Patients with osseointegrated implants and patients intended for implants in the temporal bone for bone-anchored epistheses and bone conduction hearing devices were investigated by a 3-D Accuitomo cone beam computed tomography machine. Images in sagittal, coronal, and axial planes were obtained and analyzed in a personal computer. Preoperative and postoperative views were analyzed regarding implant integration, bone resorption, anatomic landmarks, and implant failure. RESULTS: Eighteen patients were included in the study. With the used technique, it was easy to detect air cells, the sigmoid sinus, and posterior fossa and to recommend an ideal implant installation site. Bone resorption, bone overgrowth, and implant connex to air cells and dura were easy to detect. CONCLUSION: Accuitomo cone beam tomography showed to be a reliable method for investigating osseointegrated implants in the temporal bone.

Cone beam computed tomography for assessment of root length and marginal bone level during orthodontic treatment.

OBJECTIVE: To evaluate the accuracy and precision of cone beam computed tomography (CBCT) with regard to measurements of root length and marginal bone level in vitro and in vivo during the course of orthodontic treatment. MATERIALS AND METHODS: Thirteen patients (aged 12-18 years) from an ongoing study and a dry skull were examined with CBCT using multiplanar reformatting for measurements of root length and marginal bone level. For in vivo evaluation of changes in root length, an index according to Malmgren et al was used, along with a modification of this method. RESULTS: The in vitro mean difference between physical and radiographic measurements was 0.05 mm (SD 0.75) for root length and -0.04 mm (SD 0.54) for marginal bone level. In vivo the error was <0.35 mm for root length determinations and <0.40 mm for marginal bone level assessments. CONCLUSION: Despite changes in tooth positions, the CBCT technique yields a high level of reproducibility, enhancing its usefulness in orthodontic research.

Effectiveness of limited cone-beam computed tomography in the detection of horizontal root fracture.

To compare the diagnostic accuracy of conventional film radiography, charge coupled device (CCD) and photostimulable phosphor plate (PSP) digital images and limited cone-beam computed tomography in detecting simulated horizontal root fracture. Root fractures were created in the horizontal plane in 18 teeth by a mechanical force and fragments were relocated. Another 18 intact teeth with no horizontal root fracture served as a control group. Thirty-six teeth were placed in the respective empty maxillary anterior sockets of a human dry skull in groups three by three. Intraoral radiographs were obtained in three different vertical views by utilizing Eastman Kodak E-speed film, CCD sensor, RVG 5.0 Trophy and a PSP sensor Digora, Optime. Cone beam CT images were taken with a unit (3D Accuitomo; J Morita MFG. Corp, Kyoto, Japan). Three dental radiologists separately examined the intraoral film, PSP, CCD and cone beam CT images for the presence of horizontal root fracture. Specificity and sensitivity for each radiographic technique were calculated. Kappa statistics was used for assessing the agreement between observers. Chi-square statistics was used to determine whether there were differences between the systems. Results were considered significant at P < 0.05. Cone beam CT images revealed significantly higher sensitivities (P < 0.05) than the intraoral systems between which no significant differences were found. Specificities did not show any statistically significant differences between any of the four systems. The kappa values for inter-observer agreement between observers (four pairs) ranged between 0.82-0.90 for the 3DX evaluations and between 0.63-0.71 for the different types of intraoral images. Limited cone beam CT, outperformed the two-dimensional intraoral, conventional as well as digital, radiographic methods in detecting simulated horizontal root fracture.

LCD and CRT display of storage phosphor plate and limited cone beam computed tomography images for the evaluation of root canal fillings.

The aim was to compare quality of liquid crystal display (LCD) and high resolution cathode ray tube (CRT) screens for the evaluation of length and homogeneity of root canal fillings in storage phosphor plate (SPP) and limited cone beam computed tomography (LCBCT) images. Endodontic treatment was performed to 17 extracted permanent lower incisor teeth. Images of each tooth positioned in a dried mandible were obtained with Digora SPP and Accu-I-Tomo LCBCT systems. Six observers scored the quality of all images on CRT and LCD screens. Results were compared using McNemar's and Cochran's Q tests (p < 0.05). The differences among the LCBCT and SPP images were determined by binomial test. No significant difference was found between ratings of CRT and LCD displays (p > 0.05). Agreement among observers' scores was higher with CRT display. Within the limits of this ex vivo study, differences between LCD and CRT monitors for the evaluation of root canal fillings are clinically insignificant independent on whether conventional radiographs, captured by means of image plates, or cone beam images are being displayed.

Limited cone-beam CT and intraoral radiography for the diagnosis of periapical pathology.

OBJECTIVE: To compare intraoral periapical radiography with 3D images for the diagnosis of periapical pathology. STUDY DESIGN: Maxillary molars and premolars and mandibular molars with endodontic problems and examined with periapical radiographs and a 3D technique (3D Accuitomo) were retrospectively selected and evaluated by 3 oral radiologists. Numbers of roots and root canals, presence and location of periapical lesions, and their relation to neighboring structures were studied. RESULTS: Among 46 teeth, both techniques demonstrated lesions in 32 teeth, and an additional 10 teeth were found in the Accuitomo images. As regards individual roots, 53 lesions were found in both techniques, and 33 more roots were found to have lesions in Accuitomo images. Artefacts were sometimes a problem in Accuitomo images. In 32 of the 46 cases, all observers agreed that additional clinically relevant information was obtained with Accuitomo images. CONCLUSIONS: A high-resolution 3D technique can be of value for diagnosis of periapical problems.

Image registration based on lifting process: an application to digital subtraction radiography.

In this paper, a digital subtraction radiology scheme is presented based on a new method for the automatic registration of dental radiographs acquired with or without rigorous a priori standardization. The scheme is comprised of an automatic registration method and a subtraction process. The proposed registration method can be considered as an object-based registration method without imposing the prerequisite of image segmentation in order to detect the boundary of the objects of interest or the automatic detection of matching landmarks. This is achieved by augmenting the dimensionality of the problem from two-dimensional gray-level matching to three-dimensional surface matching using the process of lifting in combination with a surface-matching technique. The pseudo three-dimensional affine transformation that matches the lifted images incorporates advantageous characteristics including spatial alignment of the surfaces, anisotropic correction of brightness/contrast differences, and stable convergence of the similarity function to its optimal value. The performance of the proposed automatic registration method is assessed against a manual method based on the projective transformation. The qualitative and quantitative assessments of the experiments have shown advantageous performance of the proposed automatic registration method against the manual one. Finally, the proposed registration method has been further improved in terms of execution time by the implementation of a surface decimation process.

Accuracy of proximal caries depth measurements: comparison between limited cone beam computed tomography, storage phosphor and film radiography.

The aim of this study was to compare the accuracy of limited cone beam computed tomography (LCBCT), an image plate system and F-speed film in assessing the depth of proximal carious lesions. Radiographs of a dry mandible with sound and carious teeth were obtained with all three methods. In 41 molar and premolar proximal surfaces, 2 observers independently measured lesion depth on the images from the three modalities. The correlation of measurements was assessed with Pearson's correlation analysis. Results from imaging modalities and histological sectioning (gold standard) were compared using Bland-Altman plots. Overall comparison of the depth measurements from the imaging modalities and the gold standard was done using repeated-measures ANOVA. Pairwise comparisons of systems were done by the Bonferroni t test. The correlation between the measurements of the two observers was 0.977 for film, 0.997 for image plate system and 0.998 for LCBCT. Bland-Altman plots revealed that LCBCT agreed very closely with the gold standard while the agreement between the latter and the image plate--or film--images was moderate. The mean difference and 95% limits of agreement between LCBCT and the gold standard were smaller than those between either image plate or F-speed film and the gold standard. The LCBCT method appears as a promising tool for detection and monitoring of proximal carious lesions.

Effect of delayed scanning of storage phosphor plates.

OBJECTIVE: To test longevity of image quality in storage phosphor plates (SPPs) at various exposure settings, storage conditions, and delays in scanning. STUDY DESIGN: Fifteen Digora plates were exposed from 0.08 to 0.20 seconds and scanned immediately, 10, 30, and 60 minutes, and 24 hours after exposure. Plates were stored both in daylight and in a light-tight box. Mean gray values (MGVs) were compared using 2 x 5 x 5 factorial ANOVA. Interaction between variables was tested using Bonferroni/Dunn multiple comparisons test. RESULTS: MGVs decreased with increase in exposure but increased with the scan delay. Only MGVs of plates scanned within 10 minutes after exposure were not significantly different from the ones scanned immediately ( P > .05). MGVs increased with scan delay for all exposure times no matter how the plates were stored ( P < .05). CONCLUSION: Based on the time delays examined, it is recommended to scan the Digora SPP no later than 10 minutes after exposure. Longer periods may cause loss of quality.

Effect of iterative restoration on the detection of artificially induced vertical radicular fractures by Tuned Aperture Computed Tomography.

OBJECTIVE: The purpose of this study was to evaluate the effect of the number of iterative restorations (IR) on the diagnostic accuracy of Tuned Aperture Computed Tomography images (TACT) for detection of induced vertical/oblique root fractures in mandibular teeth. STUDY DESIGN: Fractures were induced in 28 single-rooted, endodontically treated cadaver mandibular teeth while another 26 such teeth served as controls. TACT slices reconstructed by using 9 arbitrary projections (angular disparity of 9 degrees -20 degrees) were iteratively restored 1, 2, and 3 times. Eight observers scored their diagnoses by using a confidence rating scale. Ground truth was available from direct examination with transillumination, following extraction. RESULTS: Mean areas under the representative ROC curves for the 3 operations were 0.96 (3 IRs), 0.87 (2 IRs), and 0.86 (1 IRs). Analysis of variance demonstrated significant differences between 3 and 1 to 2 IRs (P <.01), as well as between observers (P <.01). CONCLUSION: Diagnostic accuracy of TACT for vertical/oblique root fracture detection improved after 3 IRs.