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Biomedical subjects

T J Freer

Publications and source records attributed to T J Freer.

At least 19 recordsLinked to original sources
PubMed2002

Strength decay of orthodontic elastomeric ligatures.

AIM: To evaluate, over a 12-week period, the tensile strength (TS) and extension to TS of elastomeric ligatures (both clear and coloured) obtained from two companies. SETTING: Ex vivo study. METHOD: Seven replicates of five ligatures from two orthodontic companies were tested using an ex vivo assembly which simulated a clinical situation. RESULTS: The ligatures tested had a similar TS decay pattern, with the TS gradually decreasing over the duration of the study. The Unitek ligatures exhibited a greater TS than their respective Ormco ligatures. Generally, all of the ligatures tested experienced an increase in the extension to TS over time. The pre-stretching procedure used in this study did not produce any long-term detrimental effects on the TS and extension to TS of the ligatures tested. CONCLUSIONS: The results of this study confirm there are differences in TS, and extension to TS between clear and coloured elastomeric ligatures, and that some significant differences also exist between different brands of elastomeric ligatures.

Analysis of Variance↗
PubMed2002

A survey of dental and oral trauma in south-east Queensland during 1998.

BACKGROUND: This project investigated the aetiology of dental and oral trauma in a population in south-east Queensland. The literature shows there is a lack of dental trauma studies which are representative of the general Australian population. METHOD: Twelve suburbs in the south-east district of Queensland were randomly selected according to population density in these suburbs for each 25th percentile. All dental clinics in these suburbs were eligible to participate. Patients presenting with dental and oral trauma were eligible to participate. RESULTS: A total of 197 patients presented with dental/oral trauma over a 12 month period. The age of patients ranged from 1-64 years whilst the most frequently presenting age group was 6-10 years. There was a total of 363 injured teeth with an average of 1.8 injured teeth per patient. Males significantly outnumbered females in the incidence of trauma. CONCLUSIONS: The highest frequency of trauma occurred in the 6-10 year age group. Most injuries in this group occurred while playing or riding bicycles. In the next most prevalent trauma group, 16-20 years, trauma occurred as a result of fighting and playing sport. Overall, males significantly outnumbered females by approximately 1.8:1.0. The majority of injuries in the deciduous dentition were to periodontal tissues. In the secondary dentition most injuries were to hard dental tissue and pulp.

Accidental Falls↗
PubMed2002

Frictional resistance to sliding archwires with repeated displacement.

Fictional resistance between a length of stainless steel archwire and a single bracket was calculated, and the effects of cyclical displacement forces on frictional resistance were tested. With the application of repeated displacement forces to the archwire, the force required to slide the wire through the bracket was substantially reduced. The percentage reduction in the force required to slide the wire was dependent on the size of the displacement force applied to the archwire. Frictional resistance in the mouth may not be satisfactorily reflected by steady mode laboratory models. The clinical implications for different types of orthodontic brackets remain unresolved.

Dental Stress Analysis↗
PubMed2002

Distortions in panoramic radiographs.

This study was designed to investigate the factors affecting linear distortion in orthopantomography A test model was constructed with metallic rods positioned to simulate maxillary teeth from the first permanent molar to the lateral incisor. In addition to examining the effects of varying the tilts of the test rods in a mesiodistal or bucco-palatal direction, spatial position changes (sagittal displacement, transverse displacement and horizontal rotation) of the test model were evaluated by determining the magnification changes in the width and length of the test rods. Results showed that significant errors occurred with all variations in magnification when test rods were inclined buccopalatally (p < 0.001) at or exceeding 5 degrees relative to the true perpendicular, and for spatial positioning errors (p < 0.05) at or exceeding +/- 5 degrees and +/- 5 mm. Bucco-palatally inclined objects in the lateral incisor-canine region were particularly susceptible to large changes in horizontal magnification. Linear measurements and clinical assessments from panoramic radiographs should therefore be undertaken cautiously. To minimise errors in orthopantomography, it is important to position the patient in the focal trough precisely according to the manufacturer's specification.

Artifacts↗
PubMed2002

Pulp-test responses in orthodontic patients.

The diagnosis of orofacial pain is complicated in the orthodontic patient as treatment-induced alterations to pulpal physiology may result in altered responses to pulp-test stimuli. Thirty-three subjects commencing fixed orthodontic treatment and another 15 subjects not undergoing orthodontic treatment were used in this study. Cold and electrical stimuli were applied to the maxillary incisor teeth prior to treatment, after the placement of fixed appliances and at regular intervals for both groups for up to 252 days. At baseline, response thresholds to electric testing were typically higher for orthodontic subjects, particularly for the lateral incisors. For the non-orthodontic group, the response threshold over the 252 days was relatively constant. For the orthodontic group, application of force immediately increased the response threshold to electric pulp testing, which peaked after two months. By day 252, response means for lateral incisors still remained elevated. Responses to thermal testing were more consistent and reliable. The results of this study indicate that dental practitioners should interpret responses to electric pulp testing cautiously in orthodontic patients and that thermal testing with carbon dioxide snow may be more reliable.

Adolescent↗
PubMed2001

An evaluation of the changes in malocclusion index scores over a 25-year period.

BACKGROUND: The measured values of specific traits of occlusion may be subject to significant change due to growth and maturation of the dentofacial structures. Some traits may show improvement while others may show deterioration. Rarely is there an opportunity to examine a sample of occlusions 25 years after the acquisition of the original set of records. This study examines the changes in traits of occlusion in a sample of 46 subjects who were originally examined between 1971-1973 and for whom records were again obtained in 1998. METHODS: The 46 patients were a sub-group of a previously selected randomised school-based sample and study models obtained in 1971-1973 were still available. New models for each patient were obtained in 1998. Of the 46 subjects, only eight had received orthodontic treatment. RESULTS: Assessments of the changes in specific traits were made using the methods proposed in the Harry L Draker, California Modification (HLD Cal Mod) index. This simple index was chosen because the main component traits were well defined and, when analysed separately, reflected changes with time. The total index score gave a broad indication of the global changes in the individual's occlusion. The five basic traits of the HLD index include overjet, overbite, openbite, mandibular protrusion and labio-lingual spread. Three additional traits (ectopic eruption, anterior crowding and posterior crossbite) are used in the HLD Cal Mod index. These traits provided a useful reflection of occlusal changes with time. Measurements were made with reference to specifications and the details outlined in the HLD Cal Mod protocol. The results revealed an increase in total index scores over time with a significant increase in lower labio-lingual spread associated with an increased score in anterior crowding. Overjet and overbite, however, displayed a significant decrease with time. CONCLUSIONS: These findings are in keeping with previous studies and highlight the importance of time as a significant issue in the assessment of occlusion.

Adult↗
PubMed2001

Incidence and aetiology of facial injuries resulting from motor vehicle accidents in Queensland for a three-year period.

BACKGROUND: No studies have been reported on the frequency and aetiology of facial injuries due to MVAs in Queensland. This study aims to investigate the incidence, aetiology, age and sex distribution of facial injuries resulting from MVAs for a period of three years. METHOD: Cases were identified from the Motor Accident Insurance Commission, Queensland. Information including the type of injury sustained, the time, age and role of the patient in the accident were recorded and analysed. RESULTS: There was an average maxillofacial injury incidence of 4.8/100,000 per year, 53.5 per cent in males and 46.5 per cent in females. A peak incidence was found for both sexes aged 18 to 22 years. In males, 57 per cent of facial injuries occurred in this age group compared to 41 per cent in females. CONCLUSIONS: Maxillofacial injuries as a result of MVAs are still relatively high regardless of the legislation for compulsory seatbelt use. Recent advances in seatbelt systems have the potential to reduce the risk of head and face impacts. The airbag is also well established as an effective means of preventing serious head and face injury. However, more research is required to further reduce the incidence of maxillofacial injuries as a result of MVAs.

Accidents, Traffic↗
PubMed2000

Epidemiology of dental trauma: a review of the literature.

This article reviews recent reports describing the aetiology of dental trauma from national and international studies as well as the different classifications currently used to report dental injuries. It also discusses possible preventive measures to reduce the increasing frequency of dental trauma. Reported studies demonstrate that males tend to experience more dental trauma in the permanent dentition than females, however, there does not appear to be a difference between the sexes in the primary dentition. Accidents within and around the home were the major sources of injury to the primary dentition, while accidents at home and school accounted for most of the injuries to the permanent dentition. The most frequent type of injury was a simple crown fracture of the maxillary central incisors in the permanent dentition while injuries to the periodontal tissues were more common in the primary dentition. When preventive measures are being planned, knowledge of aetiology is important. More prospective studies from representative populations are required to understand the complexities of dental trauma epidemiology and to allow implementation of preventive strategies to reduce the increasing frequency of dental trauma.

Accidents↗
PubMed1999

Variations in treatment need using four screening methods.

The study models of 100 Grade Seven students were used to compare the Dental Aesthetic Index (DAI), the Dental Health Component (DHC) and the Aesthetic Component (AC) of the Index of Orthodontic Treatment Need (IOTN), and the Danish Ministry of Health (DMH) screening system. The basis for comparison was the agreed subjective assessment of two orthodontists for each subject. Disagreements between the subjective assessment and each screening method were further analysed in an attempt to identify the specific occlusal traits responsible for the disagreement. The DAI under-estimated treatment need in cases with displaced canine teeth, incisor crowding or rotations and increased overbite. The DAI over-estimated treatment need in cases with increased overjet in otherwise well-aligned arches. The DMH guidelines over-estimated treatment need in cases with increased overjet and crowded arches. The DHC was found to be over-sensitive in cases with increased overjet and contact point displacements greater than 2 mm. The AC under-estimated treatment need in cases with excessive overjet and buccally displaced canines, and over-estimated treatment need in cases with spaced arches and deep overbite.

Adolescent↗
PubMed1999

EICO-1: an orthodontist-maintained expert system in clinical orthodontics.

Expert systems are increasingly being used to provide comprehensive interpretative services for diagnosis and treatment planning. Some of these systems are constrained by the complexities of rule-based strategies and a need for knowledge engineers throughout the maintenance phase. A new approach to knowledge acquisition known as Ripple-Down-Rules was used in the development of EICO-1 (Expert Interpretation in Clinical Orthodontics). This expert-maintained system for automating orthodontic reports has a knowledge base of six hundred and eighty rules, and is maintained by an expert trained only in Orthodontics and without the help of knowledge engineers. EICO-1 is the first expert system in Dentistry to use Ripple-Down-Rules. It has potential as an interactive advisory tool and is applicable in a clinical situation.

Artificial Intelligence↗
PubMed1999

The effect of orthodontic treatment on salivary flow, pH, buffer capacity, and levels of mutans streptococci and lactobacilli.

Fixed orthodontic treatment has been shown to cause an increased incidence of enamel demineralisation. The purpose of this study was to investigate the changes in stimulated salivary flow rate, pH, buffer capacity, and the levels of mutans streptococci (MS) and lactobacilli in patients undergoing therapy with fixed orthodontic appliances. Saliva samples, plaque index scores and dietary histories were taken from 21 sequential patients before the start of treatment, and one month and three months after placement of brackets and bands. There was a statistically significant increase in stimulated salivary flow rate, pH, buffer capacity, plaque index scores, and in the levels of MS and lactobacilli after three months of active treatment. It is postulated that the balance between the cariogenic challenge posed by high levels of MS and lactobacilli, and the reparative effects of concurrent increases in salivary flow rate, pH and buffer capacity, determines the likelihood of mineral loss or gain over time. A failure to follow basic preventive measures may increase the risk for some patients of enamel decalcification during orthodontic treatment with fixed appliances.

Adolescent↗
PubMed1999

Tooth movement and vascularity of the dental pulp: a pilot study.

The effect of orthodontic tooth movement on the dental pulp was assessed histologically in twelve subjects. The participants in this study required the extraction of at least two maxillary first premolars for orthodontic treatment. They were asked to wear a maxillary removable appliance that acted to move a randomly determined premolar in a buccal direction. The appliance was designed to avoid contacting the contra-lateral tooth that was used as the matched control. The appliance was initially worn for a week to ensure patient comfort and cooperation. The appliance was then activated and the patient dismissed. After two weeks, the appliance was reactivated. Both the control and experimental teeth were extracted three weeks later, on the thirty-fifth day of activated appliance wear. The teeth were fixed, decalcified and sectioned. The sections were stained with haematoxylin and eosin for histological examination. This investigation demonstrated that orthodontic tooth movement did have an effect upon the dental pulp, causing vasodilation in the pulp of an orthodontically stressed tooth.

Activator Appliances↗
PubMed1998

Assessing malocclusion--the time factor.

Assessment of occlusal status for orthodontic purposes may be undertaken by subjective assessment or by means of an index of occlusion. The assessment method should be reproducible and should achieve the intended outcomes. This study investigated another possible modifying factor--performance over time. Photographs and dental casts of 45 subjects at 12 years of age were compared with follow-up records at 16 years of age. No orthodontic intervention had occurred during the 4 years. Subjective severity assessments and Aesthetic Component (AC) scores of the Index of Treatment Need (IOTN) for first and second series records were made by four orthodontists. Scores of the Dental Aesthetic Index (DAI) and Dental Health Component (DHC) of the IOTN were made by one of the authors. Implications for hypothetical decisions to treat were considered. There was a significant reduction in the subjective severity and DAI scores across the whole sample and in the mixed dentition subgroup. There was a non-significant reduction in the AC (IOTN) scores across the whole samples, but there was a significant reduction in the AC (IOTN) scores in the mixed dentition subgroup. The DHC (IOTN) categorisations proved to be more stable over the period of study.

Adolescent↗
PubMed1998

The effects of early orthodontic force application on pulp test responses.

The effects of orthodontic tooth movement on pulpal responses are of interest to the clinician. Alterations to pulpal physiology may result in altered responses to external stimuli. This pilot project tested a small group of orthodontic patients during the early stages of treatment. Heat, cold and electrical stimuli were applied prior to treatment, after the placement of fixed appliances and after one month of force application. A smaller group was tested after two months of force application. One month after force application there was a lack of response to electrical stimulation but there was continued response to thermal stimulation. The lack of response to electrical stimulation continued in the smaller group up to two months. The results suggest that the outcome of electric pulp testing during orthodontic treatment should be interpreted cautiously. Thermal testing will offer more reliable data.

Adolescent↗
PubMed1998

Anomalous dental morphology and root resorption during orthodontic treatment: a pilot study.

The present study investigated the relation between anomalous dental morphology and root resorption during orthodontic treatment. One hundred and eleven sets of orthodontic records (a total of 1,630 teeth) were examined. Root resorption was determined from post-treatment panoramic radiographs using a five-grade quantitative measurement. It was found that patients with short or blunt roots before treatment underwent significant root shortening during orthodontic treatment. Patients with any one dental anomaly had a significantly higher degree of root resorption compared with patients with no dental anomaly. Invaginated teeth, teeth with thin or pipette-shaped roots and teeth with short or blunt roots were likely to be more susceptible to root resorption than those without such anomalies. Possible linkages between the aetiological factors of dental anomalies and the susceptibility to root resorption were discussed. The presence of anomalous dental morphology should be taken into account in orthodontic treatment planning.

Adolescent↗
PubMed1998

Prevalence of dental anomalies in orthodontic patients.

The prevalence of dental anomalies including agenesis, crown shape, tooth position, root shape, and invagination were examined in 111 orthodontic patients; 74.77 per cent of the patients exhibited at least one dental anomaly. Invagination was found to be the most prevalent anomaly, whereas supernumerary teeth and root dilaceration were the least frequent anomalies. Dental invagination and short or blunt roots were significantly more prevalent in females than in males. Implications for orthodontic treatment planning are discussed.

Adolescent↗
PubMed1997

Enamel demineralization during orthodontic treatment. Aetiology and prevention.

The aetiology of enamel demineralization during fixed orthodontic treatment and its sequelae are discussed. A summary is given of the various methods available to assess the risk of demineralization prior to active treatment. The best preventive strategy would appear to be an assessment of risk factors prior to banding, coupled with fluoride rinses, regular reinforcement of oral hygiene, and dietary advice throughout the course of treatment.

Cariostatic Agents↗