(1/426) Arrested eruption of the permanent lower second molar.
The incidence of retention/impaction of the permanent lower second molar (M2inf) lies between 0.6/1000 and 3/1000. Therefore, the purpose of the present study was to investigate the craniofacial morphology, the frequency of dental anomalies and the inclination of the affected M2inf and the adjacent first molar in patients with arrested eruption of M2inf. The overall goal was to elucidate the aetiology of arrested tooth eruption and to present the characteristics of these patients in order to improve diagnosis and treatment planning. Radiographic material (profile radiographs and orthopantomograms) from 19 patients (nine females and 10 males; 13-19 years of age at the time of referral) were analysed. The ages of the patients when profile radiographs were taken for cephalometric analysis varied from 8 to 16 years. The study shows that this group of patients, compared with a reference group, had an increased sagittal jaw relationship (Class II). Specifically, the mandibular prognathism was less, the mandibular gonial angle smaller, the mandibular alveolar prognathism enlarged and the maxillary incisor inclination less than in the reference group. Furthermore, this group of patients had a more frequent occurrence of morphological tooth anomalies, such as root deflections, invaginations, and taurodontism. However, none of the patients with arrested eruption of M2inf had agenesis of the lower third molar. The study did not reveal an association between the degree of inclination of the M2inf and that of the first molar in the same region. The results of this investigation show that conditions such as the craniofacial morphology and deviations in the dentition are associated with arrested eruption of M2inf. Therefore, it is important to evaluate these conditions in future diagnosis and treatment planning of patients with arrested eruption of M2inf. (+info)
(2/426) Imaging of a Stafne bone cavity: what MR adds and why a new name is needed.
Stafne bone cavities are asymptomatic radiolucencies seen at the angle of the mandible. Although plain films are often sufficient for diagnosis, confirmatory imaging is needed in atypical cases. We describe the MR imaging findings of a Stafne bone cavity, describe the contents, explain why a new name is needed, and discuss the relative merits of different radiologic techniques for establishing this diagnosis. (+info)
(3/426) Temporomandibular joint pantomography using charge-coupled device, photostimulable phosphor, and film receptors: a comparison.
Our objective was to compare the accuracy and practicality in use of three available imaging receptors for temporomandibular joint (TMJ) imaging; namely, two computer-assisted and one traditional analog x-ray film system. A standardized tissue-equivalent encased human skull specimen was imaged using lateral and posteroanterior (PA) pantomographic projections with the Orthopantomograph OP 100 (Instrumentarium Imaging, Tuusula, Finland) and three different receptor modalities: (1) Ektavision film with Ektavision screens (Eastman Kodak, Rochester, NY); (2) DenOptix photostimulable phosphor screens (Dentsply/Gendex, Chicago, IL); and (3) the charge-coupled device (CCD) receptor, DigiPan (TREX/Trophy Radiology, Marne-la-Vallee, France). The effective focal trough was found for each receptor using lead resolution grids placed at fractional millimeter distances along empirically determined beam projection angulations. The time to acquire and process images was also established. We found that the CCD system permitted real-time display, whereas the use of traditional film took 2 minutes to load the cassette in a darkroom and perform the exposure, and then a further 2 minutes to unload and process. The storage phosphor took 3 minutes to unload the cassette and process the image and a further 20 seconds to clear the plate following laser scanning. Film produced the greatest maximum resolution followed by the storage phosphor and the CCD. In conclusion, CCD-based TMJ pantomography provided an instant image. The photostimulable phosphor system used was the least satisfactory in terms of the time expended to obtain an image, but provided better spatial resolution than the CCD. Ektavision film/screens provided the best spatial resolution in this investigation. (+info)
(4/426) Osteometry of the mandible performed using dental MR imaging.
BACKGROUND AND PURPOSE: On cross-sectional and panoramic reformatted images from axial (dental) CT scans of the mandible it may be difficult to identify the inferior alveolar neurovascular bundle (IANB) in patients lacking a clear-cut bony delimitation of the mandibular canal. Dental MR images are comparable to dental CT scans, which directly show the IANB; however, measurements of length may not be reliable owing to susceptibility artifacts and field inhomogeneities in the oral cavity. Therefore, the accuracy of length measurements on dental MR images was compared with that on dental CT scans and direct osteometry. METHODS: Dental T1-weighted MR imaging using a high-resolution turbo gradient-echo sequence and dental CT were performed in six anatomic specimens. The axial scans were reformatted as panoramic and cross-sectional reconstructions on a workstation and characteristic cross sections were obtained from all mandibles. The longest axis in the bucco-lingual and apico-basal directions, the distances from the top of the mandibular canal to the top of the alveolar ridge and from the bottom of the mandibular canal to the base of the mandible, and the diameter of the bone cortex at the alveolar ridge were measured with direct osteometry on the cross sections and compared with measurements on corresponding MR and CT reformatted images. RESULTS: The correlation between direct osteometry and dental MR and CT was strong, except for the bone cortex diameter at the top of the alveolar ridge, where only a moderate correlation was found. Means of comparable length measurements were not significantly different among the three methods. CONCLUSION: The accuracy of length measurements in the jaw bones obtained using dental MR is comparable to that of dental CT and is not significantly different from direct osteometry. Thus, dental MR is a potential alternative to CT for dental imaging. (+info)
(5/426) The effect of tooth position on the image of unerupted canines on panoramic radiographs.
The purpose of this study was to evaluate whether panoramic tomograms, which are routinely used in orthodontic practice, can provide adequate information to localize an impacted canine. The effect of changes in position and inclination of an impacted canine on orthopantomograms was investigated in an experimental set-up. An upper canine was removed from a human skull and replaced in a positioning system, enabling simulated positional variations in impactions. In comparison with the image of a contralateral well-aligned canine, the length of the impacted tooth always decreased or remained unchanged, whereas the tooth width increased or remained unchanged. The angulation of the image was unaffected by varying the position of the impacted canine, but altered when the inclination of the tooth in a sagittal or frontal direction was changed. If there was any transversal shift of the impacted canine on the orthopantomogram, it was always towards the mid-sagittal plane. The curvature of the tooth increased after dorsal inclination and decreased after ventral inclination (in comparison with the contralateral well-aligned canine). (+info)
(6/426) Delayed dental age in boys with constitutionally delayed puberty.
It was the purpose of this study to evaluate dental age in boys with delayed puberty and to compare them with a group of normal, healthy boys. The study group consisted of eight boys with constitutional delay of growth and puberty (CDGP), older than 14 years, and with a testis volume smaller than 4 ml. The control group comprised 38 normal, healthy boys, aged between 12.4 and 14.3 years. Dental age was assessed using the Demirjian method and, on the basis of this evaluation, a dental delay score (i.e. dental age minus chronological age) was calculated in the CDGP and the control group. It was found that Demirjian's dental age assessment is a valid method for scoring dental age in Belgian boys between 12 and 14 years of age, and that CDGP boys showed a significant delay in dental development compared with normal boys (P = 0.0085). This study revealed a significant retardation in dental maturation of boys with CDGP. (+info)
(7/426) Radiographic factors affecting the management of impacted upper permanent canines.
The aim of the investigation was to evaluate which radiographic factors influenced the orthodontists' decision whether to expose or remove an impacted upper permanent canine and was a retrospective, cross-sectional design. The sample consisted of all radiographic records of patients referred to the Orthodontic Department at Manchester University Dental Hospital with impacted upper permanent canines between 1994-1998 (n = 44). The following canine position measurements were made from the OPG: angulation to the midline, vertical height, antero-posterior position of the root, overlap of the adjacent incisor, and presence of root resorption of adjacent incisor(s). The labio-palatal position of the impacted canine was assessed from the lateral skull radiograph. Whether the impacted canine had been exposed and orthodontically aligned or removed was also recorded. Stepwise logistic regression analysis showed that the labio-palatal position of the crown influenced the treatment decision, with palatally positioned impacted canines more likely to be surgically exposed and those in the line of the arch, or labially situated, removed (P < 0.05). Additionally, as the canine angulation to the midline increased, the canine was more likely to be removed (P < 0.05). The orthodontists' decision to expose or remove an impacted upper permanent canine, based on radiographic information, seems to be primarily guided by two factors: labio-palatal crown position and angulation to the midline. (+info)
(8/426) Persistence of deciduous molars in subjects with agenesis of the second premolars.
The purpose of the present study was to investigate persistent primary second molars in a group of young people in their late twenties with agenesis of one or two second premolars. In 1982-83 it was decided, in connection with the orthodontic evaluation of 25 patients, to allow 35 primary molars (one or two in each patient) to remain in situ. All patients had mixed dentitions and agenesis of one or two premolars. The primary teeth were generally in good condition, although root resorption and infra-occlusion (compensated by occlusal composite onlays) occurred. In 1997, 18 of the 25 patients with a total of 26 retained primary molars were reexamined, comprising a clinical examination for exfoliation, extraction, loosening, and ankylosis, and a radiographic examination for root resorption, tooth morphology (crown and root), and alveolar bone contour. The examination showed that the degree of root resorption was unaltered in 20 of the 26 primary molars. In the permanent dentitions, where these primary molars persisted, there were no morphological deviations. Three of the six remaining primary molars had been extracted and three showed extensive resorption. In three of the 26 primary molars the infra-occlusion had worsened. The present study shows that persistence of primary second molars in subjects with agenesis of one or two premolars, and normal morphology of the permanent dentition can be an acceptable, semi-permanent solution for the patient. Whether this could also be an acceptable long-term solution will be shown by follow-up studies. (+info)