Rotational Panoramic Radiography Research Articles

A Convolutional Neural Network Based Auto-Positioning Method For Dental Arch In Rotational Panoramic Radiography.

Dental panoramic radiography (DPR), a widely used medical examination method, has its intrinsic weakness in high requirement to the positioning of patient. Although positioning devices like chin support can provide a relatively stable and guaranteed environment for exposure, problems including morphological differences of jaw between patients and their improper standing postures still put the reconstructed image at high risk of getting blurred, especially in the anterior segment of dental arch. This paper proposes a novel method based on convolutional neural network (CNN) to estimate the positioning error of patient's dental arch, and thereby reconstruct the panoramic image with the corrected dental curvature, so that the blur gets reduced. Experiment results demonstrate the method's effectiveness in providing reconstructed images of stable quality for further diagnosis.

Metal Artifacts From Posterior Mandibular Implants as Seen in CBCT

Metal artifacts from dental implants have not been clarified in cone-beam computed tomography (CBCT) images in previous studies. Hence, only mesiodistal metal artifacts from dental implants in the posterior mandibular region were assessed using CBCT. Twenty-two patients with a total of 61 dental implants in posterior mandibular sites were enrolled. The pixel values surrounding dental implants were measured using CBCT and rotational panoramic radiography, and then the means were calculated. The mean pixel values between dental implants, between dental implants and neighboring teeth, and posterior to dental implants were significantly lower than between neighboring teeth in CBCT. In addition, the mean pixel value between dental implants did not significantly differ from that between neighboring teeth in rotational panoramic radiography. It was concluded that mesiodistal metal artifacts surrounding dental implants are demonstrated on CBCT.

Accuracy of vertical height measurements on direct digital panoramic radiographs using posterior mandibular implants and metal balls as reference objects

Conventional panoramic radiography, a widely used radiographic examination tool in implant treatment planning, allows evaluation of the available bone height before inserting posterior mandibular implants. Image distortion and vertical magnification due to projection geometry is well described for rotational panoramic radiographs. To assess the accuracy of vertical height measurements on direct digital panoramic radiographs, implants and metal balls positioned in the posterior mandible were used as radio-opaque reference objects. The reproducibility of the measuring method was assessed by the inter- and intraobserver agreements. Direct digital panoramic radiographs, performed using a Kodak 8000C (Eastman Kodak Company, Rochester, NY), of 17 partially edentulous patients (10 females, 7 males, mean age 65 years) were selected from an X-ray database gathered during routine clinical evaluation of implant sites. Proprietary software and a mouse-driven calliper were used to measure the radiological length of 25 implants and 18 metal reference balls, positioned in mandibular posterior segments. The distortion ratio (DR) was calculated by dividing the radiological implant length by the implant's real length and the radiological ball height by the ball's real height. Mean vertical DR was 0.99 for implants and 0.97 for balls, and was unrelated to mandibular sites, side, age, gender or observer. Inter- and intraobserver agreements were acceptable for both reference objects. Vertical measurements had acceptable accuracy and reproducibility when a software-based calibrated measurement tool was used, confirming that digital panoramic radiography can be reliably utilized to determine the pre-operative implant length in premolar and molar mandibular segments.

Accessory Mental Foramen Assessment of Rotational Panoramic Radiography in Dry Mandible Using Para-Panoramic Images

Accessory Mental Foramen Assessment of Rotational Panoramic Radiography in Dry Mandible Using Para-Panoramic Images

Maxillofacial cone beam computed tomography: essence, elements and steps to interpretation

Maxillofacial cone beam computed tomography (CBCT) is one of the most significant advances in dental imaging since rotational panoramic radiography. While the acquisition of CBCT data is technically simple, numerous parameters should be considered so that CBCT imaging is performed appropriately and 'task specific'. This involves an understanding of not only exposure (e.g. geometric and software parameters to minimize patient dose, while sustaining diagnostic image quality) but also image formatting options to maximize image display. CBCT images contain far more detailed information of the maxillofacial region than do panoramic or other 2-D images and necessitate a thorough knowledge of the 3-D anatomy of the region and considerations of variability in the range of the anatomically normal. These principles, procedures and protocols, together with the interpretation of CBCT images form the basis of best practices in maxillofacial CBCT imaging. This communication aims to provide: (1) an overview of the fundamental principles of operation of maxillofacial CBCT technology; (2) an understanding of 'task specific' equipment, image selection and image display modes; and (3) a systematic methodology for sequencing interpretation of CBCT images.

Guest Editorial

The aim of this supplement on dentomaxillofacial radiology (DMFR) is to enhance the knowledge base of dentists in the area of DMFR and to promote the specialty of DMFR. As Guest Editor it is my role to guide readers through a series of papers selected both because of the expertise of the contributor/s as well as an enhancement of the services offered to patients as a routine part of their oral health care. The first commercially produced rotational panoramic radiography unit became available in 1961 and virtually revolutionized maxillofacial radiology. The interest and uptake of this technology was almost unprecedented and understandably the manufacturers have accepted the challenge and now produce radiology machines capable not only of producing panoramic imaging but a range of other techniques. The recent introduction of cone beam volumetric tomography (CBVT) is reactivating this fervour. Interest in DMFR and demands for continuing professional development in this specialty are at an all-time high and so it is with great pleasure and pride in my specialty that I am presenting this supplement. This supplement, following in the wake of previous very successful supplements, is designed to complement and add to our existing knowledge in the field of DMFR. Experts from around the world and Australia were invited to contribute cutting edge review articles covering many aspects of DMFR. As you might expect, a relatively large number of articles focus on different aspects of CBVT. However, there are also articles covering the basics of DMFR including: dose, radiographic interpretation, forensic radiology and radiological jurisprudence. We are a profession responsible for guiding the health of our patients and should be ever mindful that ionizing radiation has the potential to adversely affect the patient’s health. It is our responsibility to use ionizing radiation only when it is appropriate and when we do expose our patients to X-rays, we must gain maximum return from that exposure. All too often dentists fail to use the clinical skills that they acquired during their training and in practice, prior to irradiating patients. Only after all clinical avenues of assessment have failed to solve the problem or elucidate the cause of the problem should we resort to ionizing radiation. This supplement will hopefully give the reader information that will help them decide whether diagnostic imaging is appropriate given the patient’s treatment requirements. We are being negligent if we irradiate the patient unnecessarily, but also if we fail to use diagnostic radiography when appropriate. We are also being negligent if we do not get the most from each radiographic examination that we undertake or request from a third party provider. That means scanning every radiograph and data set for incidental findings that may or may not relate to the original diagnostic indication. Also, as indicated in the article on radiological jurisprudence, the whole radiograph and the whole data set is the responsibility of the person performing the examination. This can be particularly significant when examinations using wide-field of view cone beam units are performed in dental practices. Due care requires that all available imaging is reported and the clinician accepts this responsibility every time an image is exposed. I encourage you all to read the articles presented in this supplement and renew your excitement in a field that is exploding with new technology and advancements. You and your patients will benefit greatly from your expanded knowledge base in the field of dentomaxillofacial radiology.

Demonstration of the accessory mental foramen using rotational panoramic radiography compared with cone‐beam computed tomography

Rotational panoramic radiography is routinely used in dental practice. It has not been clarified, however, whether an accessory mental foramen can be demonstrated using this technique. The visibility of accessory mental foramina on rotational panoramic radiographs was compared with those on para-panoramic images reconstructed from cone-beam computed tomographic (CBCT) images. A total of 365 patients (130 males and 235 females) were retrospectively analyzed. Para-panoramic images were reconstructed from CBCT images with the accessory mental foramen/foramina using three-dimensional visualization and measurement software, and then the accessory mental foramen on rotational panoramic images was compared with that on para-panoramic images. A total of 37 accessory mental foramina were observed in 28 patients on CBCT images. The rate of being able to visualize the accessory mental foramen or bony canal between the point of bifurcation from the mandibular canal and the accessory mental foramen on rotational panoramic radiographs was 48.6% (18 of 37 accessory mental foramina). Approximately half of the accessory mental foramina-positive CBCT images demonstrated the accessory mental foramen, or bony canal between the point of bifurcation from the mandibular canal and accessory mental foramen on rotational panoramic radiographs.

Inferior alveolar canal course: a radiographic study

To describe the morphology and course of the inferior alveolar canal (IAC) as it appears in digital panoramic radiographs. Three hundred and eighty-six digital rotational panoramic radiographs (OPG) were studied using the Clinview Software (6.1.3.7 version, Instrumentarium). Among the 386 radiographs, 86 radiographs with 5-mm steel balls were used to calculate the magnification. The average magnification of radiographs in this study was 7.24+/-7.55%. The course of IAC as seen in the panoramic radiograph may be classified into four types: (1) linear curve, 12.75%, (2) spoon-shaped curve, 29.25%, (3) elliptic-arc curve, 48.5%, and (4) turning curve, 9.5%. On panoramic radiographs, the IAC appeared closest to the inferior border of the mandible in the region of the first molar. In relation to the teeth, on panoramic radiographs, the IAC appeared closest to the distal root tip of the third molar and furthest from the mesial root tip of the first molar. In the OPG, there are four types of IAC: linear, spoon shape, elliptic-arc, and turning curve. The data found in the study may be useful for dental implant, mandibule surgery, and dental anesthesia. The limitations of the panoramic radiograph in depicting the true three-dimensional (3D) morphology of the IAC are recognized, computed tomography (CT) and cone beam (CB)3D imaging being more precise.

Mandibular metastases from follicular carcinoma of the thyroid gland: a case report

A case of metastatic thyroid carcinoma near the left mandibular ramus with a cyst-like appearance on rotational panoramic radiographs is reported. A 55-year-old woman complained of a continuous sense of incongruity for 3–4 years since extraction of the left mandibular third molar. The lesion, with apparent gingival swelling around the left second molar, was painless and was cyst-like in appearance on plain radiographs. On the basis of the radiological findings, a benign odontogenic tumor was suspected, but computed tomography (CT) showed destruction of the lingual cortical bone with soft tissue invasion to the masticator space. The final histopathological diagnosis was metastatic follicular carcinoma of the thyroid gland. When investigating cyst-like radiolucent lesions with thick sclerotic margins and irregular areas on plain radiographs, we recommend using CT to evaluate the effect of the lesion on cortical bone.

Stability of Vertical Height Measurements on Digital Panoramic Radiographs Using Posterior Mandibular Implants as Reference Objects

Background. Panoramic radiographs have been used as standard examination tools for implant treatment planning and have been reported to give the best radiographic survey, impart a low radiation dose, and appear sufficient to evaluate available bone height before inserting posterior mandibular implants. Image distortion in rotational panoramic radiography has been well described.

Usefulness of cone beam computed tomography for odontogenic myxoma

A case of odontogenic myxoma is reported as showing a cyst-like pattern with a partially thick but vague and unclear radiopaque border between the left mandibular second premolar and first molar on rotational panoramic radiography. Internal structure of the lesion displayed radiolucency with a sparse and coarse trabecular pattern. No expansion of bucco-lingual cortical bone was apparent. The radiographic pattern of odontogenic myxoma did not resemble a tennis racket-like or straight, curved and coarse septal appearance on panoramic radiography, but characteristic findings were noted on cone beam CT. Cone beam CT may prove extremely useful in clarifying detailed internal structure and the state of margins.

Radiological and clinical follow‐up of machined‐ and anodized‐surface implants after mean functional loading for 33 months

The purpose of this retrospective study was to compare peri-implant bone loss and mucosal conditions around machined-surface (MS) and anodized-surface (AS) interforaminal implants in the mandible at least 30 months after placement. Fifty patients, each treated with four interforaminal screw-type implants consecutively, were included. Thirty-one patients (62%) with a total number of 124 implants (64 MS and 60 AS implants, both Brånemark type MKIII) were available for follow-up. Rotational panoramic radiographs were used for evaluating marginal bone loss. Clinically, marginal plaque index (mPI), bleeding on probing (BOP) and pocket probing depth (PPD) were evaluated. AS implants showed significantly less marginal bone loss than MS implants (-1.17+/-0.13 vs. -1.42+/-0.13 mm; P=0.03). Marginal bone loss around distal implants was less pronounced at AS implants (-1.05+/-0.14 mm) when compared with MS implants (-1.46+/-0.14 mm; P=0.05). Within the smoking group, there was less peri-implant bone loss around AS implants than around MS implants (-1.08+/-0.27 vs. -1.83+/-0.2; P=0.04). No differences between MS and AS implants were found with respect to mPI (57% vs. 67%), BOP (21% vs. 17%) and mean PPD (2.59+/-0.29 vs. 2.56+/-0.28 mm). Overall, both types of implants, in combination with bar-supported overdentures, can produce excellent long-term results in the interforaminal edentulous mandible with less peri-implant bone loss around rough implant surfaces, which had beneficial effects at distal implants and in smokers.

Radiographic features of enostosis determined with limited cone-beam computed tomography in comparison with rotational panoramic radiography

Radiographic findings of enostosis often resemble those of focal condensing osteomyelitis of inflammatory origin, and the location and state of these lesions cannot be precisely diagnosed using rotational panoramic radiography. Consequently, a differential diagnosis approach is required. This study examined the situation and characteristics of mandibular enostosis using limited cone-beam computed tomography (CBCT) in comparison with rotational panoramic radiography. Forty-four radiopaque lesions were examined on rotational panoramic radiography and CBCT. The lesions were diagnosed as enostosis from radiographic features on CBCT that had been performed for other clinical diagnoses or dental treatments. For each lesion, the site, margin, density, and relationship to tooth roots were determined on rotational panoramic radiography, and the shape of the cortical bone was determined on CBCT. Enostosis occurred in the premolar region of the mandible in 25 cases (57%) and displayed numerous patterns of relationships to adjacent teeth on rotational panoramic radiography. All lesions displayed an ovoid external form on rotational panoramic radiography. On CBCT, enostosis arose from buccal cortical bone in 13 cases and from lingual cortical bone in 25 cases; a lingual origin was suspected in the remaining six cases. The periodontal ligament space of adjacent teeth near the lesion was clearly apparent on both rotational panoramic radiography and CBCT. Rotational panoramic radiography and occlusal radiography cannot diagnose exactly the location and state of enostosis. The diagnosis of enostosis can be difficult for lesions influenced by secondary infection in the roots of surrounding teeth; diagnosis in these cases may be facilitated by clarifying the manifestation involving the periodontal ligament space of adjacent teeth and confirming bone thickening arising from the inner surface of cortical bone.

Narrowing of the inferior dental canal in relation to the lower third molars

To assess narrowing of the inferior dental canal in the lower third molar regions using computed tomography (CT) and to determine the value of radiographic markers on rotational panoramic radiographs in assessing the true relationships of the inferior dental canal. Patients referred for CT assessment of impacted lower third molars were used in this study. The lower third molars were assessed using CT to determine the position and morphology of the inferior dental canal relative to the roots and the cortical plates. The radiographic markers on rotational panoramic radiographs were correlated with the CT findings when rotational panoramic radiographs were available. The patients referred had 202 lower third molars. Inferior positioning of the inferior dental canal was the most common location on CT. Narrowing of the inferior dental canal was found in relation to the lower third molars in 66.8% of cases. The chance of narrowing of the inferior dental canal as shown using CT increased when at least one of the radiographic markers, superimposition, narrowing, deviation or reduction in density was present on the rotational panoramic radiograph. Deviation of the inferior dental canal on rotational panoramic radiographs was found to be the most significant predictor of narrowing of the inferior dental canal and a close relationship to the roots, as shown in CT. Narrowing of the inferior dental canal is a common finding when impacted lower third molars are assessed using CT. On rotational panoramic radiographs deviation of the inferior dental canal is the best predictor of narrowing of the inferior dental canal and a close relationship to the roots.

Radiologic diagnosis of enostosis in the mandible

Enostosis occurs from the inner surface of cordal bone and grows into the cancellous bone. This lesion has not been understood in detail. Three-dimensional images by cone-beam CT for dental use can be useful to diagnose this lesion. Although osteosclerosis, focal condensing osteomyelitis, and dysplastic lesions of the jaw bone occur near the root of tooth, their shape and aspect observed on rotational panoramic radiographs are often similar to enostosis. Therefore we attempted to differentiate these lesions from enostosis using radiographic features. Enostosis is usually not extracted; therefore the diagnosis of enostosis is actually done by cone-beam CT for dental use (3DX multi-image microCT; Morita, Kiyoto, Japan), which can precisely observe the relationship between the lesion and adjacent cortical bone. Forty radiopaque lesions diagnosed as enostosis from their radiographic features by 3DX images were used in the study. The radiographic features of these 40 lesions were investigated using panoramic, periapical and occlusal radiographs. The appearance of 40 lesions was observed according to occurrence site, relationship with the roots of teeth by these radiographs, relationship with the mandibular canal, and the shape of lesions by 3DX images. Fifty percent of the cases of enostosis were located in the premolar region in the mandible and observed osteosclerosis-like images surrounding the mental foramen or mandibular canal on 3DX images. Twelve cases of enostosis arose from buccal cortical bone, 23 from lingual cortical bone, and 5 unclassified. On the rotational panoramic radiographs, 40% of the enostosis masses made contact with tooth roots, 40% were located in the body of the mandible, and the remainder were edentulous. The enostosis presented as an ovoid radiopaque lesion on the rotational panoramic radiographs, and their internal structure showed either uniform radiopacity or not. Lamina dura of adjacent teeth nearby the lesion showed clearly. Neither rotational panoramic radiograph nor occlusal radiograph can exactly diagnose the location and state of the enostosis. 3DX images can diagnose this lesion in detail.

Radiographic findings on 3rd molars removed in 20‐year‐old men

In this study we assess radiographic findings characteristic of mandibular 3rd molars that had required either routine or surgical extraction. X‐ray findings relating to acute pericoronitis were also examined. The material was collected by investigating patient records and rotational panoramic radiographs of 20‐year‐old Finnish male conscripts (n = 738) treated during military service because of 3rd‐molar‐related problems. The follicle around the crown of mandibular 3rd molars with acute pericoronitis was enlarged in 19% of cases and in 13% of chronic symptom‐free pericoronitis cases (not statistically significant difference). Mandibular 3rd molars extracted surgically were more often mesially inclined than those extracted routinely (61% vs. 23%; P < 0.001), partially or totally intrabony impacted (92% vs. 66%; P < 0.001) and deep situated (on average 4.2 mm vs. 2.5 mm under the occlusal plane). Surgical extraction was also associated with the roots completely developed [92% vs. 84% of the teeth routinely extracted, odds ratio (OR) 2.6, 95% confidence interval (CI) 1.2–5.5] and with the absence of radiographic pericoronitis [around 27% vs. 39% of the teeth routinely extracted (OR 0.5, 95% CI 0.3–0.8)]. In 86% of cases the space between 2nd molar and ramus of the mandible was narrower than the 3rd molar extracted surgically, whereas this was 62% in routine extraction cases (P < 0.001). We conclude that there are some typical 3rd‐molar findings in rotational panoramic radiographs that show a need for surgical extraction.

Paediatric absorbed doses from rotational panoramic radiography.

To determine the paediatric doses in rotational panoramic radiography with film/screen and photostimulable phosphor receptors. A paediatric anthropomorphic head and neck phantom was used. Absorbed doses were measured for two panoramic systems, the Orthophos (Sirona Dental Systems, Bensheim, Germany) and the PM 2002 CC (Planmeca Oy, Helsinki, Finland), with and without programmable child settings, using both screen/film and photostimulable phosphor receptors. Absorbed doses to the eye ranged from 5 to 24 micro Gy. Doses to the dental arches with the Orthophos unit ranged from 50 to 555 micro Gy with the adult and from 27 to 436 micro Gy with the child program; using the PM 2002 CC unit, doses ranged from 56 to 1040 micro Gy using the adult settings, and from 60 to 890 micro Gy with the paediatric settings. The paediatric exposure settings reduced doses at most locations for both panoramic systems. The highest doses were measured near the rotational axes of the X-ray beam. Paediatric settings with the Orthophos P10 resulted in the dose reduction more than 50% to the thyroid but not with the PM 2002 CC. When lower kVcp or mA settings were used, absorbed doses were effectively reduced for all combinations of machines, programs and detectors. Specific program settings for children reduced the absorbed doses from panoramic radiography irrespective of the machine or receptor used.

Paediatric absorbed doses from rotational panoramic radiography

Paediatric absorbed doses from rotational panoramic radiography

Radiographic localization of unerupted teeth: Further findings about the vertical tube shift method and other localization techniques

The parallax method (image/tube shift method, Clark's rule, Richards' buccal object rule) is recommended to localize unerupted teeth. Richards' contribution to the development of the parallax method is discussed. The favored method for localization uses a rotational panoramic radiograph in combination with an occlusal radiograph involving a vertical shift of the x-ray tube. The use of this combination when localizing teeth and supernumeraries in the premolar region is illustrated. When taking an occlusal radiograph to localize an unerupted maxillary canine, clinical situations are presented where modification of the vertical angulation of the tube of 70° to 75° or of the horizontal position of the tube is warranted. The limitations of axial (true, cross-sectional, vertex) occlusal radiographs are also explored. (Am J Orthod Dentofacial Orthop 2000;118:439-47)

Radiographic localization of unerupted mandibular anterior teeth

The parallax method and the use of 2 radiographs taken at right angles to each other are the 2 methods generally used to accurately localize teeth. For the parallax method, the combination of a rotational panoramic radiograph with an occlusal radiograph is recommended. This combination involves a vertical x-ray tube shift. Three case reports are presented that illustrate: (1) how this combination can accurately localize unerupted mandibular anterior teeth, (2) how a deceptive appearance of the labiolingual position of the unerupted tooth can be produced in an occlusal radiograph, (3) how increasing the vertical angle of the tube for the occlusal radiograph makes the tube shift easier to discern, (4) why occlusal radiographs are preferable to periapical radiographs for tube shifts, and (5) how localization can also be carried out with 2 radiographs at right angles to each other, one of which is an occlusal radiograph taken with the x-ray tube directed along the long axis of the reference tooth. (Am J Orthod Dentofacial Orthop 2000;118:432-8)