Profile of lingual orthodontic users in Australia.

BACKGROUND: The use of lingual orthodontic appliances and the training background of orthodontists in Australia using the lingual orthodontic technique are largely unknown. The aim of this study was to investigate the profile of lingual orthodontic users in Australia. METHODS: Four hundred and fifty questionnaires consisting of 15 questions were sent out to orthodontists in Australia. We obtained a 62 per cent return rate (278) with a 58 per cent rate of completed questionnaires. Statistical analysis using SPSS was performed and various outputs were obtained. RESULTS: Of the completed returns, 23 per cent were current lingual users; 69 per cent were not and 8 per cent were previous users but have stopped using the appliance. The majority (90 per cent) of the current lingual users were males. The highest percentage of users (35 per cent) was in New South Wales while the smallest percentage was in Tasmania (2 per cent). Around 40 per cent of respondents attended lingual courses as part of their specialist training programme, while 73 per cent had attended lingual courses since graduation and 82 per cent would consider attending a lingual course in the future. Of the 60 per cent current users who did not have a lingual component in their specialist training programme, almost nine-tenths had attended lingual courses since graduation. Of the non-lingual users, 14 per cent attended lingual courses as part of their specialist training programme, 28 per cent attended lingual courses since graduation and 38 per cent would consider attending a lingual course in the future. The main reason cited for being a non-lingual user was that lingual orthodontics could not be an integral part of the practice. CONCLUSIONS: Most of the orthodontists who graduated more than 16 years ago from their postgraduate training were non-users of the lingual appliance. It seems that around one in four orthodontists currently use the lingual technique, of which NSW orthodontists make up the largest group. Only one-fifth of users had some lingual component in their formal orthodontic training and about half of them have attended lingual courses after graduation. Almost half of orthodontists in Australia would consider attending a lingual course in the future. This survey provides a sound basis for course co-ordinators to plan for continuing lingual orthodontics in the future.

Validation of two-dimensional measurements of root resorption craters on human premolars after 28 days of force application.

The aims of this study were to develop a three-dimensional (3D) mathematical model of a typical root resorption crater and to correlate two-dimensional (2D) surface area measurements to 3D volumetric measurements of root resorption craters created under light and heavy orthodontic forces. Data were obtained from a previous study of 36 first premolars from 16 subjects requiring extraction of these teeth as part of their orthodontic treatment. Buccal tipping forces of 25 or 225 g were applied for an experimental period of 28 days. After extraction, the samples were prepared for scanning electron microscopy (SEM) imaging, image processing and analysis. Surface area (2D) and volumetric (3D) measurements of all craters were obtained. A mathematical analysis of the 2D/3D relationship enabled the determination of an appropriate digital model for the shape, type and dimensions of resorption craters, which was also able to distinguish between a 'hemispheric' model versus a 'layered' model of craters. The results demonstrated that 2D and 3D measurements were strongly correlated (r = 0.991**). Within the light and heavy force groups, the measurements were also strongly correlated (r = 0.978** and r = 0.994**, respectively). For a 28 day experimental period, 2D measurements of root resorption craters were found to be as reliable as 3D measurements.

Exploring the third dimension in root resorption.

OBJECTIVE: To review and investigate the validity of various 2D quantitative measurement techniques, and to explore the third dimension of root resorption. DESIGN: A review of the literature involving various quantitative evaluation of root resorption. RESULTS: Quantitative evaluation of resorption using radiographs has proven to be highly inaccurate because of magnification errors and their inability to be readily repeated and reproduced. Studies using histology sections of samples have proven to be laborious and technique sensitive. Inherent parallax errors and loss of material in data transfer have denied the true understanding of this 3D event. CONCLUSION: With the evolution in computing technology and digital imaging, the vision of evaluating the extent of root resorption in 3D has materialized. It was demonstrated that 3D volumetric quantitative evaluation of root resorption craters was feasible and its accuracy and repeatability was high.

Root resorption and its association with alterations in physical properties, mineral contents and resorption craters in human premolars following application of light and heavy controlled orthodontic forces.

OBJECTIVES: To study the effect of different orthodontic force levels on cementum, investigating from the point of view of its physical properties, alterations in the mineral components, type and location of the resorption craters and the exploration in 3D of space. DESIGN: In vivo human premolars subjected to heavy and light forces were employed for this study. After a period of movement they were analyzed for hardness and elasticity. Also, the mineral composition measuring Ca, P and F of the cementum root surface was investigated. A new method for volumetric analysis of resorption craters was developed. RESULTS: There were no significant differences for hardness and elastic modulus between the light and heavy force groups and no significant effects for different tooth positions. Significant inter-individual variation in the Ca, P and F concentrations was noted. Force-related data showed that mean volume of the resorption crater in light-force group was 3.49-fold greater than the control group, and the heavy-force group 11.59-fold more than control group. The heavy force group had 3.31-fold greater total resorption volume then light force group. Buccal cervical and lingual apical regions demonstrated significantly more resorption craters than the other regions. The 2D measurements were strongly correlated to 3D measurements. CONCLUSION: The application of light and heavy forces did not show any statistically significant differences in hardness and elastic modulus when compared with untreated teeth. The inconsistent increase or decrease of Ca, P and F contents between control and experimental teeth at sites of compression and tension were difficult to explain. There was more resorption by volume in the heavy force group as compared with the light group and controls. Our data also suggested that the high-pressure zones might be more susceptible to resorption after 28 days of force application.