Journal of Orthodontics

Late lower incisor crowding and incisor rotations remain a problem in orthodontics. We describe a new fixed retainer which is simple to use, allows physiological tooth movement, but prevents rotational and labio-lingual relapse.

The subjective grading of cases at the Dental Practice Board of England and Wales was compared to the Peer Assessment Rating Index (PAR) and Index of Orthodontic Treatment Need (IOTN) in assessing 1505 cases sampled at the Board between Late 1990 and mid-1991. Whilst some criteria are common to both systems, case by case there is only limited agreement; sources of disagreement are evaluated. The indices are essentially epidemiological tools; whilst they have shortcomings in assessing individual cases, they are related to peer opinion, and show good reliability when used on samples of cases. They can be readily updated, as findings of research or future peer opinion may dictate. Use of PAR and IOTN at the Board, instead of subjective gradings, would require a departure from decisions on withholding payment on a case by case basis. If, however, they were used onsamples of practitioners' caseloads to assess reduction of malocclusion, and residual malocclusion and need for treatment, practitioners fees could be up- or down-graded periodically according to their overall performance, to encourage more to adopt higher standards. Allowances could be made, however, for ‘limited objective treatments’ and cases where poor co-operation had impaired the result.

Targeting, use of appliances, and standards of outcome for General Dental Service orthodontic cases collected between 1990 and 1991 were compared with a sample of cases from an earlier study, collected between 1987 and 1988, using the PAR index and IQTN.

Comparisons are made generally and in relation to the changes in prior approval regulations for cases started since October 1987. More tower-need cases were treated, but there were no more ‘unnecessary’ treatments and there has been a limited improvement in outcomes, as assessed by the indices, associated with increased use of fixed appliances since 1987.

Prior approval appeared to give no tangible benefits in terms of levels of unnecessary treatment or quality of outcome.

A mathematically determined technique which seemed to be valid for the calculation of crowding and spacing in arches with acceptable alignment, was tested on a series of arches with varying degrees of crowding and irregularity.

Upper and lower study casts of 30 individuals with sufficient malalignment and crowding to warrant orthodontic treatment with fixed appliances were examined. Models were measured by three operators, using a reflex microscope interfaced to an IBM compatible PC and a customized calculation program. The degree ofcrowdmg was compared with a ‘clinical’ assessment of each arch, in which the irregularity was measured directly using a steel ruler.

Both the computer calculated and clinical values varied between observers, but the agreement between observers was better using the reflex microscope. Correlation coefficients ranged from 0·92 to 0·96 for the reflex microscope, and between 0·86 and 0·91 for the clinical assessment. Inter-observer agreement for the three operators was high: 0·93 for the reflex microscope and 0·87 where a ruler was used. This suggests that the computer program used to calculate the crowding was valid for the crowded arches under consideration.

The aim of this investigation was to determine the effect of static loading on the measured shear bond strength of steel attachments bonded to enamel. Sixty steel attachments were bond to extracted and prepared premolar teeth with Orthodontic Concise (3M St Paul, Minnesota, USA) and allowed to bench cure for 2 weeks. Half the specimens had 78 g weights suspended from the attachment, close to the bondline, prior to testing. The mean shear bond strenght for the statically loaded sample was 127 N and indicating that static loading prior to shear testing significantly increase shear bond strength.

This study was designed to test the accuracy of measurement methods for assessment of force and tooth movement in orthodontic procedures. Daily in vivo measurements of the force produced by activated archwires showed that the initial force declined substantially (by 20 per cent of mean value) within 3 days. Both the ‘trueness’ (validity) and precision of the force measurements, obtained with a strain gauge, were found to be high (SD values were 1·0 cN and 0·4 cN, respectively). Horizontal tooth movements were measured with three different instruments: a slide calliper, a co-ordinate measuring machine, and laser measuring equipment based on holograms. There was a good level of agreement between these methods. This was also confirmed by calibration data. The precision of the methods was (SD values) 0·06, 0·07, and 0·13 mm, respectively. The benefits of the use of the co-ordinate measuring machine are obvious, since it can measure tooth movements in relation to reference planes in all directions.

Skeletal and dental morphology, and related growth changes during a 3-year period following second permanent molar eruption, were compared in a group of 21 subjects who had no increase in lower arch crowding, with another group of 21 subjects whose lower arch crowding had increased by 1.0 mm or more during the same period.

The crowding group showed a significantly greater increase in M3 space, forward movement of the second permanent molar and increase in the inter-incisal angle than the non-crowding group. None of the other parameters examined differed significantly.

Orthodontists are often concerned about the prognosis of root-filled teeth, particularly when extractions are required for orthodontic treatment. This review provides guidance on assessing the quality of root fillings, as well as the factors which affect the prognosis of root-filled teeth. The implications of previous traumatic injuries and the likelihood of root resorption during orthodontic tooth movement are discussed.

A total of 301 unselected orthodontic referrals were assessed for temporomandibular disorder, using a standardized questionnaire and clinical examination protocol. The mean age of the patients was 13·4 years. Over one-third of the 301 patients were found to exhibit at least one sign of TMD, and two-thirds had a mandibular dysfunction index (MDI) score of 1, 2 or 3, indicating mild to moderate. dysfunction. Only five patients were found to have severe temporomandibular dysfunction. Statistically significant relationships were found between patient age and mandibular opening, and temporomandibular joint noises. No relationship was found between signs detected by clinical examination and symptoms reported by the patients.

Recent developments in material science have lent themselves to improving orthodontic archwire technology. The pace of change has been great, leaving the clinician a bewildering choice of materials for the purposes of force application. The following article characterises the properties of new archwire formulations and is intended to give guidance in choosing archwire material during the first stage of orthodontic therapy.

This article explores the key aspects of business planning and management which are most appropriate for the successful orthodontic practice. It is written by consultants who are experienced in helping individual practices achieve personal and professional goals.