X-ray diagnosis of impacted upper canines in panoramic radiographs and computed tomographs.

Ten orthodontists were asked to diagnose the number of impacted upper canines and the number of resorbed lateral and/or central incisor roots in 30 panoramic radiographs (P1) from 30 patients. In order to objectify these diagnoses, transversal CT images of all 30 patients were examined in addition. Addition of the recordings in the 30 patients revealed that the 10 orthodontists had diagnosed 350 impacted/displaced canines. On comparison of the P1 and CT results, the latter revealed that, in fact, 390 canines were impacted or displaced, not just 350. Addition of the recordings further showed that, based on P1, the investigators had diagnosed 73 resorptions in the 1,200 incisors examined. However, the CT showed 160 resorptions; this corresponds to a sensitivity value of 45.6%. The CT showed 1,040 incisors with no resorptions, whereas the investigators diagnosed only 925 teeth as not resorbed in the P1. The specificity was thus 88.9%. These results show that, due to their low reliability, panoramic radiographs are not an appropriate means of diagnosing resorptions in front teeth in connection with impacted canines.

Assessment of the space for the lower wisdom teeth. Panoramic radiography in comparison with computed tomography.

From 13 patients a computed tomograph (CT-scan) and a panoramic radiograph (Orthophos, program 1, P1) were examined with respect to the spatial conditions of the lower wisdom teeth. In the panoramic radiograph the available space for the third molars of the lower jaw was determined by calculating the ratio (Q) of 2 distances: the mesiodistal crown diameter and the retromolar space. In the axial CT 3 different positions of the third molar were distinguished: third molar located anterior to the ramus mandibulae = sufficient space, partially within the ramus = restricted space, totally within the ramus = deficient space. These positions were compared with the findings in the panoramic radiograph, firstly in relation to the ramus and secondly in relation to a line (L) perpendicular to the occlusal plane at the intersection of the anterior border of the ramus and the crista temporalis. Furthermore, the mesial rotation of the third molar was measured and the relation of the bony structures surrounding the teeth were described. Comparison of the CT results with the quotients of the P1 showed that, for those wisdom teeth molars with an available space above 50% to under 100%, any of the 3 CT gradings was found. Assessing the projection of the ramus over the third molar as seen in the P1, 60% of the P1- and CT-results corresponded. The relation between the line L and the third molar showed coincidence in 76% of all cases. These results and the mesial rotation of the wisdom teeth as well as their different relation to the bony environment are possibly important factors concerning their eruption prognosis. The three-dimensional CT-scan gives new possibilities for further investigations of third-molar problems.

[Incisor roots in the mandibular symphysis in the computed tomogram and in the lateral teleradiogram]. / Die Schneidezahnwurzel in der Unterkiefersymphyse in Computertomogramm und in der Fernröntgenseitenaufnahme.

On the basis of lateral cephalograms and computer tomograms (CT) the position of the incisor roots and the bone structure surrounding them were studied. Nine patients each had an axial CT of the mandibular symphysis area and, in addition, 6 of these patients had lateral cephalograms. In order to compare both images, we defined a classification scheme as follows: Class 1 = the incisor roots are projected into the midst of the oral corticalis of the symphysis; class 2 = the roots are in contact with the oral corticalis; class 3 = the incisor roots are at a distance to the oral corticalis. The results from the 2 types of visualization were then compared. When looking at the bone structures surrounding the incisor roots, the lateral cephalograms failed to yield an exact differentiation. Such details can be best examined in the axial CT layers, because in the lateral cephalogram the 4 incisor roots are over projected to 1 root. The space for movement of the incisors is narrow. The root of each and every patient showed a different position in oro-buccal direction. This fact must be taken into consideration in clinical practice, especially when employing fixed appliances with 3-dimensional root control.

[The maxillary sixth-year molar and its relation to the maxillary sinus. A comparative study between the panoramic tomogram and the computed tomogram]. / Der Oberkiefer-Sechsjahrmolar und seine Beziehung zur Kieferhöhle. Eine Vergleichsstudie zwischen Panoramaschichtaufnahme und Computertomogramm.

Panoramic radiographs (OPGs) and computer tomograms (CTs) of 30 patients, the latter taken on average 2.5 months later, were evaluated for the purpose of comparing the relation of their roots to the bottom of the maxillary sinus. The CT and OPG images yielded significant differences in the topographic relations between the roots and the maxillary sinus. In the OPG 64 out of 129 roots seemed to penetrate the maxillary sinus. In the CT transversal slices, on the other hand, penetration could be observed for only 37 roots. This phenomenon became more apparent when the relations between the mesial, distal, buccal, and oral root surfaces and their relations to the sinus were assessed. Applying a three stage scoring scheme, it was found that in the large majority of cases only the apices were in contact with the mucosa of the sinus. Thus, the possible loss of anchorage in these cases is below five percent.

The application of computerized tomography (CT) in cases of impacted maxillary canines.

A comparison is made between conventional X-rays and computerized tomography (CT) based on eight patients with thirteen impacted upper permanent canines. The use of CT yields information which is much more detailed than that observed on conventional X-rays, such as: pathological resorption on adjacent teeth caused by aberrant canines; the localization of the injury and the position of the canine in relation to one or both incisors. The amount of radiation per exposure is still rather high for the CT (Köster and Ewen, 1986). Further research is necessary in order to reduce this exposure and to determine the appropriate and most effective use of CT in the dental field.

[Damage to the remaining teeth from displaced upper canines]. / Die Schädigung bleibender Zähne durch verlagerte obere Eckzähne.

25 patients with 35 retained upper canines were examined by high resolution CT; only 5 patients did not show evidence of damage to the remaining teeth. 8 patients showed resorption related to medial and lateral incisors. 19 teeth were in contact with the crowns of the displaced canines and were therefore liable to damage. The average extent of the resorption was 4.5 mm. Contact between teeth was demonstrable by means of two consecutive CT cuts.

[Schmuth's group findings--a simple system for classifying dysgnathias]. / Die Befund-Gruppen nach Schmuth--ein einfaches Einteilungssystem der Dysgnathien.

The advantages and disadvantages of Schmuth's findings, which classify eugnathic as well as dysgnathic dentition are opposed to Angle's classification. Using Schmuth's findings is a way of classifying without ignoring the physiological variability in the area of the first molars, which can lead to false diagnosis. 386 models were examined at the beginning of the patients' treatment. The results are discussed.