Journal of Orthodontics

In order to investigate both the relationship between perioral muscular activity and tooth position and also the clinical indicators of this activity, two quantitative EMG studies were carried out. The first investigated the reproducibility of the method in 16 adults. Subsequently, a study employing the same protocol was conducted on 41 subjects with untreated malocclusions. Activity was measured during speech, whilst chewing biscuit, swallowing saliva, resting, and in those subjects with incompetent lips, during lip-seal. In addition to the EMG recordings, measurements were taken from study models, lateral skull radiographs and of the clinical lip heights. In general, between visits random variability was sufficiently small for the method to be applied experimentally. The results suggest that the effects of perioral muscular activity are determined by the presence or absence of competent lips. This was despite similar levels of activity in both groups except during chewing. Resting activity did influence incisor position in subjects with competent lips but the intermittent activity from chewing, speaking and swallowing, did not. No clinical indicators of the level of perioral activity were found.

The anchorage bend is an essential feature of the Begg technique. The factors which affect the degree of the anchorage bend include operator preferences as well as certain mechanical features of the case being treated. A test jig was constructed so as to be able to measure on the bench the intrusive forces developed by an anchorage bend over the six anterior teeth for a selection of different archwires. The amount of force developed was proportional to the degree of anchorage bend and also to the diameter of the archwire. The jig was modified in order to measure the frictional resistance to distal movement generated by the anchorage bend. The resistance was found to be greater than the usually quoted forces designed to slide the upper archwire distally. An oval tube was placed on to the test jig and doubled back archwires used. A reduction in intrusive force for a particular degree of anchorage bend was seen although frictional resistance was not affected when using doubled back archwires.

Alternative methods for recording the shape of the facial soft tissue integument in three dimensions are discussed. The requirements for and problems associated with head positioning are indicated, and a technique is described by which head positioning errors can be overcome. The results of three-dimensional analysis of a sample of human subjects are described, with particular reference to the method of analysis and orientation planes selected. Finally, possible clinical uses for three-dimensional recording are suggested.

The study set out to investigate the problems of the implementation of the Court Report's suggestion that every child in its tenth year should be screened for orthodontic treatment by ‘a dentist with special training in orthodontics’ using Grainger's Treatment Priority Index (TPI). The study was divided into two parts. The standardization exercises used 31 orthodontic models of children in their tenth year. The problem of examiner variability, using a Community Dental Officer instead of an orthodontist and of bias that the TPI might have were examined. The main study involved the examination of 362 children in ten separate schools in Oxfordshire and investigated the problem of orthodontic screening at annual school inspections. The findings showed that the TPI may be able to provide a method for screening children in their tenth year if the weights of the clinical entities which are reducing the level of validity of the TPI are identified. The problem of scoring tooth displacements consistently would have to be taken into consideration when training personnel to use the TPI.

Three groups of Class II/I patients were compared where treatment was carried out using Begg, Andresen and removable appliance techniques. Skeletal growth, as assessed by the dimensions S-Me, N-Me, ALFH and Me-Ar did not show any difference between the groups. All three groups showed an apparent improvement in skeletal pattern during treatment.

There was a fall in the birthrate in England and Wales from 1964 until 1977 from 875,972 to 569,259 per annum. This short paper draws attention to the implications for the provision of orthodontic treatment and suggests that, since fewer patients are likely to present for treatment, an opportunity exists to improve the standard of care provided.

A case is reported in which considerable external resorption of the crown of a lateral incisor occurred during storage in a buccal pouch.

The angulation of the maxillary central incisor crown to its root has been measured in 191 patients representing the four classes of incisor malocclusion. Significant differences were only found between Class II Division 1 and Class II Division 2 groups.

A lower removable appliance utilizing a buccal baseplate and lingual clasps is described. Its successful use is illustrated with a case history.

The use of a 1·0 mm auxiliary archwire to reinforce anchorage and provide an attachment for an orthodontic force is described. The use of tie-back circles in flexible archwires to stabilize long buccal spans is described.