Journal of Orthodontics

The effects of cleft lip and palate on facial growth and dental occlusion are reported for a pair of genetically identical twins only one of which has a cleft of lip and palate. Mandibular growth and arch form are similar for both patients but downward growth of the maxilla has been less for the cleft twin and the maxilla is contracted compared with that of the normal twin.

Indications for the use of extra-oral traction during orthodontic treatment with removable appliances are discussed and a typical case is described.

The Oblique Lateral Jaw Radiograph has been used as a routine diagnostic x-ray view for many years as an aid to orthodontic diagnosis and for the assessment of the positions of unerupted third molar teeth.

Many methods for obtaining clear undistorted views of the teeth have been suggested from a freehand setting up of film, patient and x-ray tube, to the use of simple orientated devices.

The present article describes a method of standardizing the relationship of film and x-ray tube to one another so that it is only necessary for the radiographer thereafter to place the patient on the film area in a manner depending on whether a view. is required of the third molars only or of the complete upper and lower buccal segments.

The maxilla projects a poor shadow on a lateral radiograph, and its reference points are correspondingly vague. If the mandibular canal is relatively stable in the growing mandible, it is not unreasonable to assume that the incisive foramen may well be so in the maxilla. This anatomical investigation of five cadavers gives evidence to show that the palatine foramen is consistently related to the papilla and can be simply identified with a radio opaque marker. Repetition of accuracy would appear superior to Downs' point “A”.

The use of a plastic embedding technique has been described and its relevance in orthodontic teaching and clinical practice discussed. We have found that many aspects of orthodontic instruction benefit from the use of these materials.

A sample of 62 cases of supernumerary teeth found in the lateral incisor area was selected and analysed. The great majority of these teeth were supplemental teeth, with deciduous precedents. Both teeth (the normal incisor and supernumerary) showed reduction in size as compared to the unaffected side. Differences were found between the mesial unit and the distal—the mesial being larger and having an incisor shape and the distal smaller and resembling a canine. Many of the pairs were similar to supernumerary teeth found in cleft lip and palate and there were also effects upon the other teeth particularly central incisors. Stigmata of cleft were observed in the alveolus, nasal floor and hard palate in a significant proportion of cases. It is concluded that supernumerary laterals arise by gemination or failure of development of normal odontogenic material. The anomaly fulfils the hypothetical criteria for a microform of cleft and may be the result of a minor error in embryonic fusion.

The commonly used radiographic techniques to locate unerupted teeth are described. This information is valuable in deciding whether the unerupted tooth could be brought into the dental arch with a resultant improvement in the occlusion both functionally and aesthetically. If the accommodation of the unerupted tooth is not possible or desirable a decision has to be made either to retain or remove it. The various management decisions are illustrated radiographically.

A variety of orthodontic elastics were investigated: firstly to determine any change in length and consequent loss of force of selected orthodontic elastics when subjected to intra and intermaxillary forces under a simulated intra-oral environment (creep test); and secondly, to produce and interpret average stiffness graphs for each type of elastic tested.

Some types of elastic showed a considerable amount of creep and the force produced would fall off even after 1 hour of use, especially when they were employed for intermaxillary traction.

An Instron testing machine was used to produce stiffness graphs. The thinner elastics gave lower stiffness figures but the forces these elastics produced in the mouth were more predictable.

Recent research on the problem of communicating with the patient is reviewed. It is shown that the frequent failures of both informative and persuasive communications are due in part to patients not understanding and to their forgetting what they are told.

Factors making for difficulties in communication are outlined, and methods are described for reducing failures of understanding and for increasing memory of what is said. Evidence on the effectiveness of these remedial methods is presented.