Biomedical subjects
Publications and source records attributed to N J McGuinness.
Ameloblastic fibroma is a rare mixed odontogenic tumour, which is extremely uncommon in the anterior maxillary region. A case report is presented where failure of eruption of an upper central incisor was the presenting feature.
There is some concern that patients treated by postgraduate students during their specialty training may be disadvantaged in the quality of treatment result and subject to longer treatment times if they are treated by more than one operator. This study analysed the pre- and post-treatment study models of orthodontic patients from a district general hospital department, debonded by one junior member of junior staff in the calendar years 1991 and 1992. All patients were treated using the same pre-adjusted edgewise appliance in both arches. Two groups of patients were identified: patients whose treatment was started and finished by the same operator (registrar A), and those whose treatment was begun by another operator (registrar B), but finished by registrar A. A random sample of 30 patients from each group was selected and the study models at the start and end of treatment were scored using the PAR (Peer Assessment Rating) Index. No significant differences were found between the average PAR scores for each group at the beginning of treatment, or between groups A and B at the end of treatment; the average treatment time for the patients treated by one operator was 17.67 months (SD 4.15 months), while the average treatment time for the patients treated by more than one operator was 26.1 months (SD 6.78 months). Statistically, this difference was highly significant (P < 0.001). A highly linear relationship (R2 = 0.92) was found between the percentage PAR score reduction and the initial PAR score. The findings and their implications are discussed.
In the past, vertical intrusive movement of teeth has been considered difficult and most routine clinical vertical movement of teeth has been confined to extrusion. It has been suggested that attempts at intrusion may result in an increased incidence of root resorption and also in occasional devitalization. The displacement and resulting stress fields associated with such treatment can be successfully studied using the finite element method. In the case being considered initial movements are known to be small; therefore, the assumption in the study that the material behaves linear-elastically is considered to be reasonable. This study of vertical tooth movement demonstrated that the maximum cervical margin stress in the periodontal ligament was 0.0046 N/mm2, whilst the highest apical stress was 0.00205 N/mm2 when intrusive and extrusive forces of 1 Newton were applied to the buccal surface of the crown of a tooth model. These stresses were evaluated in the light of previous studies and found to be within the suggested clinical optimum level. However, the periodontal stress distribution following orthodontic loading within this three-dimensional finite element model was found to be highly complex.
Orthodontic indices have been used for many years to assess the severity of a patient's malocclusion and hence determine the need for treatment. Two indices--the Index of Orthodontics Treatment Need (IOTN) and the Peer Assessment Rating (PAR) Index--have recently been developed. The use of indices is likely to become more widespread in the future so that more uniformity is achieved in assessing need for treatment and its success. This article describes how the two indices are applied.
A selection of 30 sets of study models, representing a wide range of malocclusions, was drawn from the records of a clinical orthodontic department. Four holograms were made of each set of models; the study models and their corresponding holograms were then scored using the Peer Assessment Rating (PAR) Index of malocclusion. Significantly lower scores (P < 0.01) were obtained from the holograms, which were ascribed to three out of the seven components which make up the index.
Explore the source record for details and available documents.
Orthodontic study models form an essential part of the dental records of patients undergoing diagnosis and treatment. In order to ascertain the problems encountered by hospital orthodontic units in the utilization and storage of study models, a questionnaire was circulated in February 1991 to members of the Consultant Orthodontists Group. All respondents took pretreatment study models, while 9 per cent took their final study models at some time other than the end of active treatment; 85.5 per cent of respondents stored their study models in their units, but most were beginning to experience difficulties in this regard. There was a wide range for storage times, and only 10 per cent of employing authorities had a stated policy on the storage of study models. There was a highly significant difference (P much less than 0.001) between the time that models are stored at present, and the desired storage times. Most respondents appeared to be rather uncertain about the precise medico-legal requirements concerning model storage. The implications for audit and medico-legal matters are discussed in the light of these findings.
Increasing numbers of patients are being orthodontically treated by specialist and general dental practitioners, after postgraduate courses and clinical assistantships. The potential for iatrogenic damage to the teeth and supporting structures has, therefore, also increased. This paper examines these problems and outlines measures for their prevention.
The accurate modelling of teeth under orthodontic load in the laboratory has many shortcomings in that it has not been possible to integrate methods, such as three-dimensional models, photo-elastic stress analysis, laser holographic interferometry, and animal studies, to give comprehensive and repeatable results. In this study, using a three-dimensional finite element model of a human maxillary canine tooth, the maximum principal stresses in the periodontal ligament produced by various orthodontic forces were determined. 1 Newton tipping forces produced stresses at the cervical margin of the periodontal ligament as high as 0.196 N/mm2 and apical stresses up to -0.034 N/mm2, while rotatory forces of two equal, but opposing forces of 0.5 Newton at the cervical margin of the crown produced cervical margin stresses ranging between -0.035 and 0.051 N/mm2, and apical stresses of between 0.0018 and 0.0027 N/mm2. These stresses are examined and discussed in relation to previous clinical, laboratory, and histological studies.
Explore the source record for details and available documents.