Diane J. Flint

Computer‐aided Dental Identification: An Objective Method for Assessment of Radiographic Image Similarity*

Abstract:  A pilot study evaluated a computer‐based method for comparing digital dental images, utilizing a registration algorithm to correct for variations in projection geometry between images prior to a subtraction analysis. A numerical assessment of similarity was generated for pairs of images. Using well‐controlled laboratory settings, the method was evaluated as to its ability to identify the correct specimen with positive results. A subsequent clinical study examined longitudinal radiographic examinations of selected anatomical areas on 47 patients, analyzing the computer‐based method in making the correct identification based upon a threshold level of similarity. The results showed that at a threshold of 0.855, there were two false negative and two false positive identifications out of 957 analyses. Based on these initial findings, 25 dental records having two sets of full mouth series of radiographs were selected. The radiographs were digitized and grouped into six anatomical regions. The more recent set of films served as postmortem images. Each postmortem image was analyzed against all other images within the region. Images were registered to correct for differences in projection geometry prior to analysis. An area of interest was selected to assess image similarity. Analysis of variance was used to determine that there was a significant difference between images from the same individual and those from different individuals. Results showed that the threshold level of concordance will vary with the anatomical region of the mouth examined. This method may provide the most objective and reliable method for postmortem dental identification using intra‐oral images.

The assessment of impacted maxillary canine position with panoramic radiography and cone beam CT

OBJECTIVE The aim of this study was to correlate the position of impacted maxillary canines on panoramic radiography with cone beam CT (CBCT) and analyse the labiopalatal position of canines and root resorption of permanent incisors in CBCT according to the mesiodistal position of canines on panoramic radiographs. METHODS This study was a retrospective radiographic review of 63 patients with 73 impacted maxillary canines. The mesiodistal position of the canine cusp tip was classified by sector location and analysed on 73 impacted canines from 63 panoramic radiographs. The labiopalatal position of the impacted canines and root resorption of permanent incisors were evaluated with CBCT. The sector location on panoramic radiographs was compared with the labiopalatal position of impacted maxillary canines on CBCT. The statistical correlation between panoramic and CBCT findings was examined using the χ(2) test and the Fishers exact test. RESULTS Labially impacted canines in CBCT were more frequent in Panoramic Sectors 1, 2 and 3, mid-alveolus impacted canines were more frequent in Sector 4 and palatally impacted canines were more frequent in Sector 5. There was a statistically significant association between the panoramic sectors of the impacted canines and the labiopalatal position of the canines (p < 0.001). Root resorption of permanent incisors showed a significant difference according to sector location (p < 0.001) and was observed in Sectors 3, 4 and 5. CONCLUSIONS This study suggests that the labiopalatal position of impacted canines and resorption of permanent incisors might be predicted using sector location on panoramic radiography.

Advances in diagnostic imaging for pathologic conditions of the jaws.

Advances in dental and maxillofacial imaging are delineated along with the advantages and disadvantages of each imaging modality. The imaging modalities that are included are intraoral radiography, panoramic radiography, cone-beam computed tomography, multidetector computed tomography, magnetic resonance imaging, nuclear medicine, and ultrasound.

Why should we insist patients remove all jewellery

Body piercing is now a popular trend among adolescents and adults. According to Armstrong et al,1 body piercing is defined as the insertion of a needle to create an opening into either cartilage or skin for the introduction of decorative jewellery. A study at one US college found the prevalence of body piercing was 51% among 454 undergraduate students who completed a survey in 2001.2 Another study at an urban hospital-based adolescent clinic found that, among 225 participants aged between 12 and 21 years in 2000, 48% had a body piercing. Among this sample of pierced participants the most common sites for body piercings were the ears (74%), nose (34%), tongue (30%), navel (27%) and eyebrow (15%), with fewer than 7% reported piercings in other places.3 Of concern for oral and maxillofacial imaging are piercings in the ears, nose and tongue owing to the potential for metallic artefacts in the radiographic images. A 30-year-old female attended the emergency dental clinic in the Oral and Maxillofacial Radiology Clinic at Texas A & M Health Science Center, Baylor College of Dentistry and a panoramic projection (Figure 1) was taken. The patient stated that she could not remove the earrings before the X-ray exposure. As a result, the image had large ghost images across the maxillary sinuses from the retained earrings. During a surgical procedure the same day, the oral and maxillofacial surgeon extracted a non-restorable right maxillary second molar and tooth fragments/odontomas distal to this second molar. Owing to the serous fluid expressed from a sinus fistula in that area, the oral and maxillofacial surgeon ordered a follow-up appointment with a new panoramic projection. The patient was informed that she must remove all of her earrings before the second radiograph to clearly visualize the entire right maxillary sinus and rule out the possibility of a cystic lesion. The panoramic projection (Figure 2) was taken at the Oral and Maxillofacial Radiology Clinic 1 week later. A displaced impacted tooth was noted at the superior border of the right maxillary sinus. A cone beam CT (CBCT) study was acquired 2 days later. A cystic lesion associated with the impacted tooth in the right maxillary sinus/orbit area was noted (Figure 3). Biopsy and surgical treatment are pending. Figure 1 Panoramic radiograph for the extraction of right maxillary second molar and ghost images of earrings noted (arrow heads) Figure 2 Panoramic radiograph 1 week later and a displaced impacted tooth noted in the right maxillary sinus region (arrow) Figure 3 Cone beam CT images. (a) Coronal view; (b) frontal three-dimensional image Earrings are the most popular type of body piercing. It is common today to find both male and female patients with unilateral or bilateral ear lobe jewellery, in single or multiple pierced sites. Some patients are unable to remove the piercings because of permanent soldering of the metals. To remove or not to remove… that is the question. In a well-positioned panoramic projection the metal-based earrings will be visible, along with the ghosting caused by these objects. The non-midline ghost images appear more superior on the contralateral side and reversed with less definition than the image of the actual objects. Along with earrings, an increasing number of patients present to dental clinics wearing jewellery inserted into the perioral (lips and cheeks) and intraoral tissues (tongue and uvula), or any combination of these sites.4 While some practitioners routinely recommend that all jewellery be removed, others feel that a selective approach to removal of jewellery is appropriate. If the object is thought to interfere with the diagnostic quality of the film then it should be removed.5 When metal jewellery is present during radiographic examination, it may prevent visualization of normal anatomy and/or pathoses, as in this case. Non-diagnostic images may lead to retakes, with an increase in ionizing radiation exposure to the patient. By avoiding production of these artefacts when possible, we can reduce radiation exposure to patients while obtaining the most diagnostically acceptable images possible.5 In summary, patients should be strongly advised to remove any piercings of the head and oral cavity that will be visualized in the radiographs before X-ray exposure and counselled as to the consequences of failure to do so.