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The demand for clear sequential aligner therapy has increased dramatically in recent years. An improved system utilising small neodymium-iron-boron (NdFeB) magnetic attachments has been proposed to enhance appliance capabilities.The aim of the investigation was to analyse the force system diagrams produced by small attracting NdFeB magnets to determine, 1) whether the force levels were sufficient to induce tooth movement, 2) the effect of magnet morphology on force characteristics and, 3) the most appropriate magnet dimensions that could be utilised for this application.Twenty-nine NdFeB rectangular magnets of varying dimensions were tested. A Mach-1 universal testing machine (Biosyntech Inc, Quebec, Canada) was used to measure the attractive force of pairs of magnets. Measurements commenced with a magnetic pair in contact and subsequently vertically separated a distance of 10 mm at a speed of 12 mm/minute. For all magnetic configurations four repeat measurements were performed on five magnetic pairs of the same size.The force-distance diagrams for all magnet configurations demonstrated a dramatic decrease in force with increasing magnet separation. Rather than a suggested inverse square law, the experimental data followed an inverse fourth law when an offset determined by a regression analysis was applied to the distance. For the majority of magnets, insignificant forces were attained beyond 2 mm of separation. Magnets with large pole face areas and longer magnetic axes provided the greatest force.A select range of magnet configurations exhibited suitable and reliable attractive forces and therefore could be advocated for prescribed clinical application.

The aim of the present study was to determine whether high and low fluoride concentrations in drinking water affected the early stages of tooth movement when heavy and light orthodontic forces were applied for 4 weeks. A further aim was to compare and evaluate the resulting two-dimensional (2-D) and three-dimensional (3-D) orthodontic tooth movement.The sample consisted of 96 maxillary upper first premolars from 48 patients who required premolar extractions as part of their orthodontic treatment. Patients were selected from two different cities in Turkey with low and high fluoride concentrations of 0.05 and 2 ppm, respectively. The patient sample was divided into four groups according to the magnitude of force applied to the first premolars and the concentration of fluoride in the public water supply; Group 1, High fluoride intake (or = 2 ppm)-Heavy force (225 g); Group 2, Low fluoride intake (or = 0.05 ppm)-Heavy force; Group 3, High fluoride intake-Light force (25 g); and Group 4, Low fluoride intake-Light force. A light or heavy buccal tipping orthodontic force was applied to the upper first premolars for 4 weeks. The first three palatal rugae were used for the superimposition of patient casts in a 2-D and 3-D evaluation of generated movements.It was found that heavy force application and fluoride intake increased the average rate of tooth movement. It was further shown that age was negatively correlated with tooth movement in the 2-D and 3-D measurements.The average rate of tooth movement was found to be greater in the heavy force and high fluoride intake group (Group 1HH). Age was negatively correlated with orthodontic tooth movement. Two- and three-dimensional methods were accurate for the assessment of tooth movement after four weeks of buccal tipping force application when the palatal rugae were used for superimposition.

Well-finished orthodontic treatment begins with accurate positioning of the brackets on the teeth.To compare the positions of orthodontic brackets placed by experienced clinicians and inexperienced trainees.Twenty orthodontists (13 male, 7 female) representing experienced specialists, and 20 final year dental students (10 male, 10 female) representing inexperienced trainees, were asked to bond pre-adjusted straight-wire brackets at the centres of the clinical crowns of the teeth in a Class I crowded typodont set-up. The teeth were removed from the typodont, placed in a standardised jig and photographed. The vertical, mesiodistal and angular (tip) positions of the brackets, relative to the centres of the clinical crowns, were measured with the aid of imaging software. The accuracy of bracket placement by the groups was compared.The dental students took significantly longer than orthodontists to place the brackets (50.65 +/- 16.33 minutes vs 28.53 +/- 9.51 minutes, p0.001), but were more accurate than the orthodontists at positioning the brackets vertically (0.90 +/- 0.21 mm vs 1.19 +/- 0.23 mm, p0.001). There were no statistically significant differences between the dental students and the specialists in either the mesio-distal or the angular/tip positions of the brackets (p0.05). Both groups tended to bond the brackets with a distal tip. The students had slightly more right-left differences than the orthodontists. Mesio-distal errors in bracket placement were associated with rotated and displaced teeth.Accurate direct bonding of orthodontic brackets to teeth does not appear to be related to clinical experience or specialist training.

Orthodontic treatment can result in root resorption.To determine if apical root resorption is related to the type of appliance used and/or the direction and amount of tooth movement.The pre- and post-treatment tooth lengths of the maxillary and mandibular first molars and incisors were measured on panoramic radiographs of 114 subjects. Associations between changes in the lengths of the incisors and positional changes in the upper and lower central incisors were determined for 45 subjects with pre- and post-treatment cephalometric radiographs.Taking into account the gender and OPT machine seven statistically significant differences were found between the appliance groups for the lengths of teeth 31 and 41. Within the groups four teeth decreased significantly in length when the pre-adjusted appliance was used (teeth 12, 11, 21, 26) and four teeth when the Speed appliance was used (teeth 26, 31, 41, 42). Only tooth 31 was shorter when the Tip-Edge appliance was used. Lower incisors were significantly shorter post-treatment if the apices were moved close to the lingual cortex.When panoramic radiographs are used to assess treatment-induced changes in the lengths of the incisors, apical resorption is only one factor that should be considered. The images of lower incisors proclined during treatment may be foreshortened and/or the apices may lie outside the focal plane: both may result in 'shorter' teeth post-treatment. Because of the confounding factors panoramic radiographs may not be a reliable method of determining apical root resorption.

To determine the forces applied by coil springs used to open spaces for blocked out lateral incisors, and to compare the actual forces used with clinicans' concepts of an 'ideal' force.Twelve postgraduate orthodontic students (7M, 5F) and 12 orthodontic tutors (9M, 3F) participated in this study. They were asked to state what they considered was an ideal orthodontic force, and then to cut appropriate lengths of stainless steel and nickel titanium open coil springs to open spaces for blocked out maxillary and mandibular permanent lateral incisors on a typodont set-up. The forces generated by the open coil springs were measured and compared to the stated ideal forces.The mean ideal force was 76.75 g (Range: 25-200 g). The mean applied force was 314 g (Range: 21-519 g). There were no significant differences in the forces used by the male and female postgraduates, but the male tutors used a significantly higher force than the male postgraduate students (p = 0.007) and the female tutors (p0.001). The female tutors used a significantly lower force than the female postgraduates (p = 0.024) and the male postgraduates (p = 0.003). Higher forces were produced by the stainless steel coil springs in both arches (Maxillary arch: p = 0.007; Mandibular arch: p0.005).The clinicians could not agree on an ideal force to open spaces for blocked out lateral incisors. There were substantial differences between the forces applied by the coil springs and the forces considered by the clinicians to be ideal. There were large differences in the forces used by the different groups of orthodontists.

To determine if the cementum on the maxillary right and left first premolars has identical physical properties.Ten normal maxillary first premolar teeth, extracted from five orthodontic patients with a mean age of 14.0 years, were used. The teeth had not been subjected to an orthodontic force. The hardness and elastic modulus of the cementum were measured on the buccal and lingual surfaces of the roots at three locations: cervical third, middle third and apical third.There were no significant side-to-side differences in cementum hardness (Mean side-to-side difference: 0.0063 GPa; SD: 0.0279; p = 0.525) or elastic modulus (Mean side-to-side difference: -0.027 GPa; SD: 0.111; p = 0.814). The hardness and elastic modulus of the cementum decreased from cervical to apical regions on both root surfaces.Similar physical properties of the cementum on the maxillary right and left first premolars suggest that intra-arch comparisons can be used to investigate root resorption caused by orthodontic forces.

To review the management of transposed teeth, and to illustrate the treatment options with four case reports.The aetiology and management of transposed teeth are reviewed. Three management options are discussed: correcting the order of transposed teeth, maintaining the order of transposed teeth, and extraction of one of the transposed teeth. Methods of camouflaging transposed teeth are described in detail. The treatment options are illustrated with case reports.

One of the difficulties in assessing the causes of root resorption is to separate the contribution made by genetic factors from those due to environmental factors, such as treatment.The aim of this study was to investigate the genetic contribution to orthodontic root resorption.The subjects of this investigation were 16 monozygotic (MZ) and 10 dizygotic (DZ) twins. All twins had zygosity diagnosed using microsatellite analysis. Each twin-pair had same type of malocclusion, were treated with the same type of appliance, and by the same clinician. The lengths of the maxillary incisors, mandibular incisors, and mandibular molars were assessed both qualitatively and quantitatively, on pre- and post-treatment panoramic films. The genetic contribution to external apical root resorption was assessed using concordance and heritability estimates.Concordance estimates from the qualitatively and quantitatively measured external apical root resorption were 44.9 per cent and 49.2 per cent respectively for the MZ twins, and 24.7 per cent and 28.3 per cent respectively for DZ twins. An overall heritability estimate of 0.34 was obtained.External apical root resorption was not dependent on the pretreatment root length. Qualitatively and quantitatively determined estimates of concordance indicate a genetic component to root resorption. A larger sample is needed before models of heritability can be used to determine the components contributing to the variance.

With the increasing use of computed tomography (CT) in oral diagnosis and treatment planning, concern has been expressed about the high levels of radiation used, and the associated risks.The purpose of this study was to compare the radiation doses of facial CT scans with the radiation doses taking a lateral cephalometric radiograph, a panoramic radiograph (OPG), an occlusal film, and an intra-oral periapical radiograph.An Alderson-Rando anthropomorphic phantom head was used for the analysis. Thirty-six lithium fluoride thermoluminescent dosimeters were placed in the phantom head in locations representing radiosensitive sites. Standard facial CT scans and conventional radiographs (lateral cephalometric, OPG, maxillary occlusal, intra-oral periapical) were then taken of the phantom head.The following radiation doses were measured: maxillo-mandibular CT scan, 2.1 mSv; maxillary CT scan, 1.40 mSv; mandibular CT scan, 1.32 mSv; lateral cephalometric radiograph, 0.005 mSv; OPG, 0.010 mSv; maxillary occlusal, 0.007 mSv; intra-oral periapical radiograph, 0.005 mSv.CT scans produce significantly more ionising radiation than conventional radiographs. This factor should be taken into account when considering a CT scan as an alternative to a survey with conventional radiographs. While CT scans offer many advantages over conventional radiography the high radiation dose to patients, and the cost of this procedure should be considered.