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.

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 degrees to 75 degrees or of the horizontal position of the tube is warranted. The limitations of axial (true, cross-sectional, vertex) occlusal radiographs are also explored.

Radiographic localization of unerupted maxillary anterior teeth using the vertical tube shift technique: the history and application of the method with some case reports.

The preferred means of radiographic localization is the parallax method introduced by Clark in 1910. He used 2 periapical radiographs and shifted the tube in the horizontal plane. In 1952, Richards appreciated that a vertical tube shift could also be carried out. No major changes then occurred in the technique until Keur, in Australia, in 1986 replaced the periapical radiographs with occlusal radiographs. This modification enables a greater tube movement and therefore a greater shift of the image of the impacted tooth; it also ensures that the whole of the tooth is captured on the radiograph. For the vertical tube shift, Keur introduced the use of a rotational panoramic radiograph with an occlusal radiograph. In 1987, Southall and Gravely discussed this vertical tube shift combination in the English dental literature, and it is now the preferred combination of radiographs for localizing impacted maxillary anterior teeth. Jacobs introduced this method to the American literature in 1999, but it has yet to gain acceptance in the continental European literature. Jacobs recommended, when using this combination, to routinely increase the vertical angulation for the occlusal radiograph by 10 degrees to achieve a greater image shift. Four case reports are presented in this article. Three have photographs taken at surgical exposure to illustrate how the position of the impacted tooth can be accurately predicted by appropriate interpretation of the radiographs.

Localization of the unerupted maxillary canine: how to and when to.

Reasons for localizing impacted maxillary canines are outlined and methods of localization described. The favored method of radiographic localization is the parallax method (image/tube shift method). Tube shifts can be carried out in both the horizontal and the vertical planes. For a horizontal tube shift, two occlusal radiographs are recommended; for a vertical tube shift, a rotational panoramic radiograph and an occlusal radiograph are recommended. This latter combination is usually the combination of choice because the panoramic radiograph, which provides information about all the teeth in both arches, the two jaws, and the surrounding structures, is often taken as an initial radiograph and this combination only requires one additional exposure, the occlusal radiograph. To facilitate the interpretation of a vertical tube shift, the angle of the tube in the occlusal radiograph should be increased from the customary 60 degrees to 65 degrees to 70 degrees to 75 degrees. Less accurate methods of radiographic localization are to use (1) image magnification of the impacted maxillary canines and (2) image superimposition of the impacted maxillary canines on the central or lateral incisor. Reasons why periapical radiographs are not recommended to be used for a horizontal tube shift or for a vertical tube shift in combination with a panoramic radiograph are explained. Indications to suspect palatal impaction may occur in the future if the patient is less than 10 years of age, and indications to suspect impaction may have occurred if the patient is more than 10 years of age are discussed. Patient questionnaires are advocated to aid the clinician in anticipating palatal impaction, the most frequent impaction.

Reducing the incidence of unerupted palatally displaced canines by extraction of deciduous canines. The history and application of this procedure with some case reports.

The procedure of extracting the deciduous canine to reduce the incidence of the unerupted palatally displaced canine was first described in 1951, and an article solely devoted to the technique appeared in 1959. The procedure then virtually vanished until 1981. A prospective study published in 1988 created the first widespread interest in the method which now appears in major texts. Why the procedure succeeds is uncertain. In the 1950s non-resorption of the deciduous canine was thought to cause palatal deflection of its successor and therefore it appeared appropriate to extract the obstructing deciduous tooth. It has been estimated that the technique should be successful in approximately one in three of all cases in the population aged 10 to 13 years. The earlier the detection the better the prognosis, because the unerupted canine frequently moves more mesially with time. Before the procedure is attempted it is important to discuss possible outcomes with the patient. Three successfully treated cases are illustrated. The first conformed with the guidelines of having an uncrowded maxillary arch and being aged between 10 and 13 years. The second was aged 15 years 2 months at commencement. An unsuccessful surgical exposure of the permanent canines followed by extraction of the deciduous canines was carried out in the third case.

The impacted maxillary canine. Further observations on aetiology, radiographic localization, prevention/interception of impaction, and when to suspect impaction.

Adjacent anomalous or missing maxillary lateral incisors have been implicated in the aetiology of palatally displaced canines by not providing proper guidance to the canine during its eruption. However, a recent review of the literature suggests that the aetiology of palatally displaced canines is genetic in origin. The aetiology of labially impacted canines differs, being due to inadequate arch space. Vertex occlusal radiographs have been recommended for localization but have limitations, and a case is illustrated where this radiograph is deceptive. The prevention/interception of a palatally displaced canine by the extraction of the deciduous canine is best carried out as early as the displacement is detected, mostly soon after 10 years of age. Usually, prevention/interception will avoid the surgical and orthodontic treatment needed to align a palatally impacted canine and may help prevent resorption of the adjacent incisor root. Suspicions that an impaction could occur or has occurred arise a) before the age of 10 years if there is a familial history and/or the maxillary lateral incisors are anomalous or missing; b) after the age of 10 years if there is asymmetry in palpation or a pronounced difference in eruption of canines between the left and right side; or the canines cannot be palpated and occlusal development is advanced; or, the lateral incisor is proclined and tipped distally; and, on a panoramic radiograph of the late mixed dentition if the incisal up of the canine overlaps the root of the lateral incisor.

The treatment of traumatized permanent anterior teeth: case report & literature review. Part I--Management of intruded incisors.

A case is reported in which an intruded incisor was initially treated by an endodontic dressing with calcium hydroxide and then extruded using a removable orthodontic appliance. A follow-up examination seven years after completion of endodontic therapy and bleaching showed a favourable response. A review of the relevant literature indicates that intrusion occurs in five to twelve per cent of luxation cases. In this type of injury maximum damage occurs to the pulp and all supporting structures because the tooth is driven into the alveolar process. Complications which have been reported include: pulp necrosis, apical radiolucencies, partial or total pulp calcification, root resorption (surface, inflammatory or replacement), marginal periodontal bone breakdown, and arrested or disturbed root development. The prognosis for pulp survival after intrusion is much more favourable for teeth with incomplete root formation than for teeth with complete root formation. Treatment options available to bring an intruded tooth into alignment are: to await spontaneous re-eruption which may occur if root formation is incomplete, uncovering of the intruded crown, orthodontic extrusion which is allied with gentle luxation if the tooth does not move, and immediate surgical repositioning.

Palatally impacted canines: aetiology of impaction and the scope for interception. Report of cases outside the guidelines for interception.

Patients with palatally impacted canines have an increased incidence of missing or anomalous lateral incisors adjacent to the impacted canines. Their arches are often uncrowded and this, in part, is linked to the increased incidence of missing or anomalous lateral incisors. Other teeth are also more frequently missing. The present guidelines for the relief of palatally impacted canines by extraction of the deciduous canine require that the patient is aged between 10-13 years and that normal space conditions are present. Two successful case reports are presented which were outside the recommended guidelines. The technique of relieving a palatal impaction by extraction of the deciduous canine has wide application.

Localisation of the unerupted maxillary canine: additional observations.

Occlusal radiographs are recommended for the tube shift method used to localise the unerupted maxillary canine. Several case histories are presented to explore how diagnostic occlusal films may be obtained. The initial maxillary incisor inclination determines the vertical angulation of the tube, while the mesio-distal position of the canine crown determines the horizontal angulation of the tube to the mid-sagittal plane. Increased distances aid localisation: both the distance between the impacted tooth and its reference tooth, and the distance between the positions of the tube at exposure are significant. If an orthopantomogram and an occlusal film are to be taken as initial radiographs, the orthopantomogram should be read first to determine the position of the tube for the occlusal film. Radiographs taken previously may provide information on centring the tube for the occlusal film. The horizontal tube shift between two occlusal films is a more sensitive means of localising canines than is the vertical tube shift available between an orthopantomogram and an occlusal film.

Reducing the incidence of palatally impacted maxillary canines by extraction of deciduous canines: a useful preventive/interceptive orthodontic procedure. Case reports.

The early detection of palatally impacted permanent maxillary canines is stressed. Appropriate radiographs to determine impactions are suggested and removal of deciduous canines to eliminate impactions in patients who have good dental arches with no space deficiency is recommended. Two case histories are presented to illustrate the method.

Treatment planning in orthodontics and orthognathic surgery: the significance of tooth inclination and dental compensations.

The scope of orthodontic treatment is examined and the importance of the initial tooth inclinations and skeletal base relationships is explained. Dental compensations which occur in all three planes of space are discussed. Special attention is given to the importance of dental compensations in the antero-posterior plane in orthognathic surgery treatment planning. There is a necessity for early definitive decision-making in the borderline orthognathic surgery patient and the role of orthodontic camouflage is pointed out. Case selection for treatment with removable appliances is explored.

Proliferative activity of gonocytes, Sertoli cells and interstitial cells during testicular development in mice.

Developing mouse testis was studied from Day 14 post coitum (p.c.) until Day 35 post partum (p.p.) by [3H]thymidine autoradiography. The gonocytes proliferated actively at Day 14 p.c., the [3H]thymidine labelling index (L.I.) being 7.5%, and were quiescent from Day 16 p.c. up to the first day of life, when spermatogenesis started. The L.I. increased to 20% at Day 2 p.p. The L.I. for the Sertoli cells was approximately 20% before birth. After birth the proliferative activity decreased. After Day 11 p.p., the Sertoli cells showed their typical adult appearance. After Day 17 p.p. no labelled Sertoli cells were observed. The Leydig cells featured a very low proliferative activity up to Day 21 p.p. (L.I. of maximal 1.9%). At Day 29 p.p. there was a peak of 7.4% in L.I., followed by a sharp decrease to 0.35% at Day 35 p.p. The L.I. of mesenchymal cells decreased from 11.4% at Day 14 p.c. to 1.1% at Day 14 p.p. and remained more or less constant thereafter. The proliferative activity of myoid, endothelial and perivascular cells followed a similar course to that of mesenchymal cells, their L.I.s being high before birth (16, 12.5 and 19%, respectively, decreasing until Day 14 p.p. (0.6, 2.0 and 1.2%, respectively) and thereafter being more or less constant. There was an increase in the relative number of Leydig cells from approximately 4% of the total interstitial cell number at Day 14 p.p. to 29.5% at Day 35 p.p. At the same time, the relative number of mesenchymal cells decreased from 55 to 13%. The diameter of the seminiferous tubules showed a peak of 92 microns at Day 16 p.c., decreased to 44 microns at Day 1 p.p. and increased again to 204 microns at Day 33 p.p. These results show that, except for the Leydig cells, the proliferative activity of testicular cell types is highest during the pre- and early postnatal period. The major outgrowth of the Leydig cell population occurs around the fourth week after birth. The results are in accordance with the hypothesis that the mesenchymal cells are the progenitors of Leydig cells.

Intracoronal radiolucencies in unerupted teeth of orthodontic patients: three case reports.

Three cases of intracoronal radiolucencies in unerupted teeth are reported. The aetiology and treatment of this condition which may first be detected by the orthodontist are discussed. In extreme cases, involved teeth may be lost.

Ankylosis of permanent teeth: a case report and literature review.

A case report describing an ankylosed permanent maxillary canine which was brought into the arch by a combination of surgery and orthodontics is used as a basis to review the literature concerning many aspects of the management of ankylosed permanent teeth. The literature indicates surgical luxation is a two edged sword, that is, it may cause ankylosis if used with surgical exposures but it can also be the only means of treating ankylosis. The treatment of the canine which is the subject of this case report resulted in damage to the tooth. Vanarsdall's recent contributions in this field are detailed.

Teeth in cross-bite: the role of removable appliances.

The role of removable appliances with springs for the treatment of teeth in anterior and posterior cross-bite is discussed. The indications for their use (that is, case selection), and their manipulation are examined. Cases are presented where removable appliances are the appliances of choice in the first stage of the correction of a posterior cross-bite, the final treatment being completed with fixed appliances. The ease of correcting and retaining various maxillary teeth which may be in cross-bite is discussed.