[Mechanical analysis of tooth movement (I). Single tooth movement].
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Biomechanical Phenomena↗
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[The design of removable appliances for tooth movement and tooth migration].
Removable/functional appliance therapy can still be further expanded and developed. Retentive elements in the anterior region increase anchorage. Thereby, active forces can be utilised without anchorage loss. Functional appliances are indicated following extraction, to maximise on tooth migration. In first molar extraction cases, treatment with activators is relatively straightforward. When considering premolar extraction cases with possible need for extraction later of the third molars as well, then one should consider extraction of the first permanent molars. With correct use of the appliance, it is possible to optimally align the second molar teeth as well as favourably influencing the soft tissue profile.
Activator Appliances↗
Electric currents, bone remodeling, and orthodontic tooth movement. II. Increase in rate of tooth movement and periodontal cyclic nucleotide levels by combined force and electric current.
Piezoelectric currents in mechanically stressed bone were implicated in the activation of bone cells. The objectives of this experiment were to determine the usefulness of exogenous electric currents in accelerating orthodontic tooth movement and to study the effect of electric-orthodontic treatment on periodontal cyclic nucleotides. Maxillary canines were tipped in five cats by 80 g force. Two groups of five cats each were treated by an electric-orthodontic procedure to one maxillary canine for 7 and 14 days, respectively. Teeth treated by force and electricity moved significantly faster than those treated by force alone. Enhanced bone resorption was observed near the anode (PDL compression site), while bone formation was pronounced near the cathode (PDL tension site). Staining for cyclic nucleotides was increased when electric stimulation was added to the mechanical force. These results suggest that orthodontic tooth movement may be accelerated by the use of locally applied electric currents.
Alveolar Process↗
Histomorphometric study of dental pulp during orthodontic tooth movement.
Orthodontic tooth movement has been implicated in secondary changes to the dental pulp. The purpose of this study was to correlate the effects of orthodontic tooth movement on the dental pulp by histomorphometric parameters. Four groups, each consisting of 36 male adult Sprague-Dawley strain rats, were studied with differing force magnitudes. These included a sham group in addition to groups with bilaterally placed appliances activated to 20, 40, and 60 g of initial force designed to mesially tip the maxillary first molars. Six rats were killed at 1, 3, 5, 7, 10, and 14 days. Specimens were fixed, embedded, and stained with tetrachrome. Pulpal measurements were made with an image analyzer and included changes in predentin and vascularity. Findings indicated a significant increase (p < or = 0.05) relative to time and force magnitude in capillary number. An initial pulpal hyperemia was observed following activation of orthodontic force which was unrelated to force magnitude. A force-dependent increase in predentin width was measured at the peak of the tooth movement cycle.
Animals↗
Treatment with Tip-Edge brackets and differential tooth movement.
Differential tooth movement has been associated with the Begg technique and ribbon arch-type brackets since 1954. Its efficiency and effectiveness have been demonstrated and documented over the past 30 years. A relatively new edgewise-type bracket has been designed to permit differential tooth movement within predetermined limits. The following case reports describe the treatment of three differing malocclusions by means of Tip-Edge brackets and straight arch wires. The first was treated with the aid of mesiodistal crown size reduction, the second with the pretreatment removal of the four first premolars, and the third without the removal of any permanent teeth.
Bicuspid↗
Measurement of tooth movement.
1. Tooth movement relative to the alveolar bone can be precisely described only by superimposing on fixed points in the bone. Implants are the best known way today. Over short-term studies laminagraphy and the use of bony trabeculations are also useful. Remodeling occurs extensively on bony surfaces, making them too labile for use as stable landmarks. To project small amounts of tooth movement based on the use of such methods is so questionable as to represent little better than a guess or a clinical impression. 2. Growth can be separated into vertical and anteroposterior vectors with respect to the dentition. Since the occlusion is the concern, orientation of vertical and anteroposterior vectors to the occlusal plane is a reasonable baseline. The vertical and anteroposterior dental changes may not show a linear relationship in the anterior and posterior parts of the mouth when jaw rotations are occurring. 3. Growth can be disproportionate in either the vertical and/or the anteroposteroir plane of space. If the vertical increments of the anterior face differ from the vertical increments at the posterior face, mandibular rotations occur. This growth is accompanied by dental compensations that tend to mask the rotation. Therefore, open bite and deep bite are frequently skeletal growth problems. 4. Disproportional forward growth of the maxilla or mandible in an anteroposterior direction can lead to Class II or III relations. The growth that leads to Class II or Class III is accompanied by dental migrations that tend to mask this disproportionate growth. Orthodontic treatment of growth disproportionalities usually represents attempts to make the teeth further compensate. If surgical options are elected, the dental compensations should be removed prior to surgery in order to achieve a full surgical correction. 5. The teeth tend to move and grow in the opposite direction of the growth disproportionality. The teeth tend to mask the disproportionality. Thus, in an open bite, the incisors tend to move vertically further than in deep bites. Vertical imbalances may be more difficult to mask. Backward rotation of the mandible requires more vertical movement at the incisor than at the molar just to maintain vertical incisor relationships.
Child↗
[Continuous radiographic observation of orthodontic tooth movement. 1. Clinical radiographic findings in tooth movement].
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Adolescent↗
[The importance of the center of resistance for the biology of tooth movement].
The tooth movement of loaded premolars was investigated in four two-years-old beagle dogs under general anesthesia. Two supragingival registrations were performed to calculate the center of rotation in order to estimate the amount of tipping. Loads of 5 to 20 N were applied for two to four seconds. The amount of tipping was found to be load- and time-dependent. The discrepancy between these findings and the models of analytical mechanics were explained by bone bending in our experiments. Biology and localization of periodontal remodelling is supposed to be dependent on load magnitude, load duration and physical properties of all periodontal tissues including bone.
Animals↗
Reconstitution of the human oxytalan system during orthodontic tooth movement.
Orthodontic tooth movement in man has revealed that the oxytalan fiber system possesses a high order of maintenance. Oxytalan fibers did not merely increase in number during orthodontic movement. On the contrary, the oxytalan fiber system underwent reconstruction and adaptation to extensive metabolic and anatomic changes within the periodontium. With the use of light orthodontic forces, the oxytalan fiber system was constantly remodeled on both the tension and compression sides and maintained a characteristic cementum-vascular relationship even when teeth were moved a significant distance through the alveolar bone. In contrast, heavier forces caused localized destruction of the oxytalan system in regions of excessive pressure and tension. Reconstitution of the oxytalan system provided evidence against the concept that oxytalan fibers are stretched by orthodontic movement and subsequently contribute to relapse by elastic rebound. In man the oxytalan fiber system of the periodontal ligament is arranged as a three-dimensional fiber meshwork and exhibits a complex geometry like other fiber systems in the connective tissues. Knowledge of the interaction between elastic and collagen fibrillar assemblies has been used to derive some speculative concepts of oxytalan-collagen interaction. These concepts have been put forward with the intention of stimulating further interest in the oxytalan fiber meshwork. The present investigation emphasizes that the use of the light microscope to examine and record static images of complex biologic changes can provide new knowledge of the structure and function of human connective tissues.
Adolescent↗
Histochemistry of enzymes associated with tissue degradation incident to orthodontic tooth movement.
Orthodontic tooth movement in rats was examined by histochemical techniques for some enzymes associated with bone resorption and tissue damage. The maxillary first molar was moved buccally by means of a fixed appliance with predetermined forces for periods of from 10 hours to 6 days. The activities of acid phosphatase and lactate dehydrogenase were higher in cells in the connective tissue of the periodontal membrane (PDM) than in the oral mucosa. A low orthodontic force resulted in an initial redistribution of acid phosphatase-containing cells in the PDM followed by an increased activity of acid phosphatase. The activity of lactate dehydrogenase in the PDM was not affected by low orthodontic forces. The changes in distribution and activity of acid phosphatase and lactate dehydrogenase incident to a high orthodontic force were similar to those seen incident to a low force. However, there was one definite difference. A zone which lacked acid phosphatase activity and lactate dehydrogenase activity developed in the most compressed areas of the PDM. Prostaglandin synthetase activity was found exclusively in the bone marrow and seemed not to be affected by the orthodontic forces. However, some prostaglandin synthetase activity was found in the oral mucosa corresponding to the site of the orthodontic appliance. The adjacent bone surface was covered with cells showing an intense acid phosphatase activity. In the present study the magnitude of the orthodontic force seemed to be a determining factor for the vitality of the PDM but not for the tissue-degradation activity.
Acid Phosphatase↗
Analysis of moment/force ratios in the mechanics of tooth movement.
Orthodontic tooth movement is analyzed by means of the center of rotation model and the concept of moment/force ratios. Several equivalent force systems are considered at both the bracket and the center of resistance of the tooth. When moment/force ratios are evaluated at the bracket, the laws of physics appear to be suspended: inconsistencies occurring as single forces applied at different points claim equivalent results and pure translational movements purport to be nonzero moment/force ratios. These paradoxes can be reconciled only if the moment/force ratios are analyzed at the center of resistance of the tooth. Here, all of the moments applied to the tooth by the force system are included in the analysis. Only when the force system is evaluated around the center of resistance of the tooth is the concept of moment/force ratios consistently correct.
Biomechanical Phenomena↗
Adult tooth movement: alteration of the occlusal vertical dimension preparatory to tooth movement.
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Adult↗
Changes of the marginal periodontium as a result of labial tooth movement in monkeys.
Tooth position has been suggested to be an important factor in gingival recession. Due to conflicting reports in the literature, this study was undertaken to examine the effects of labial tooth movement on changes in the marginal periodontium. Orthodontic tooth movement was performed in five monkeys (Macaca nemistrina). Oral health was established and exploratory surgery was performed to assess the level of the connective tissue attachment and marginal bone. Measurements of the gingival margin and mucogingival junction were taken and orthodontic forces were applied. The central incisors were moved labially a mean distance of 3.05 mm. Posttherapy measurements were performed to assess the change which occurred as a result of tooth movement. Significant recession of the gingival margin, connective tissue level and marginal bone was found.
Animals↗
[Anatomy and physiology of the periodontium in adults under the conditions of orthodontic tooth movement].
During orthodontic tooth movement, the periodontal ligament (PDL) transduces the applied forces to the surrounding bone and is involved in the induced remodelling of periodontal fibres and alveolar bone. Due to its delicate localization between two hard tissues, the PDL is, however, prone to traumatic injuries resulting from excessive forces. With regard to the necessary remodelling processes, the adult PDL is illprepared, as all relevant physiologic cell activities, such as rate of mitosis or fibre and bone turnover, are considerably slower and have to be activated first. Furthermore, these cell activities apparently cannot be stimulated to the same level as in juvenile tissues. Thus, tooth movement, particularly in the beginning of treatment, is inevitably slower in adults than in young individuals. Any attempt to accelerate movement by applying heavier forces bears the risk of possible traumatic injuries to periodontal and root tissues.
Adult↗
[Retrospective evaluation and experimental radiographic study on bone reaction concomitant with orthodontic tooth movement].
Concomitant with orthodontic tooth movement a radiographically dense zone of high mineralisation can be observed on the periodontal tension side. This zone consists of the alveolar cortical bone and mineralized osteoid. This bone reaction has not evoked much interest in orthodontic literature in the past. In a retrospective study, orthopantomograms of children in orthodontic treatment were evaluated, and the discussed reaction was studied in relation with different treatment parameters. Opaque bone layers were found in cases in whom the orthopantomogram was made within 6 months after initiating tooth movement. When using elastics for tooth movement the bone reaction under discussion was comparatively rare. There is no proneness to root resorption in teeth showing the described adjacent bone reaction. Bone reaction was also studied with a densitometric radiological procedure. In all 9 cases the bone reaction was observed.
Adolescent↗
Centers of rotation for combined vertical and transverse tooth movements.
For purely transverse orthodontic tooth movements, the center of rotation is defined as that point on the long axis or its extension which remains stationary during the movement and around which the rotational component of the tooth displacement takes place. For tooth movements having both vertical and transverse components, no point on the long-axis line remains fixed in space. The two-dimensional theory proposed herein suggests the more general definition of the center of rotation as that point on the long-axis line which displaced the shortest distance during the tooth movement. The center of rotation can be located for the combined transverse and vertical tooth displacement. It is found to move along a path coincident with a segment of a line in a position depicting the tooth angulation midway through the movement. Formulas, which can be used in conjunction with a composite pre- and post-displacement cephalometric tracing, are presented herein to define the center-of-rotation location for such tooth movements.
Biomechanical Phenomena↗
[Biomechanical study on orthodontic tooth movement: changes in biomechanical property of the periodontal tissue in terms of tooth mobility].
The magnitude of tooth mobility has been frequently used for evaluating biomechanical response of the periodontal tissue to applied forces. However, tooth mobility during orthodontic tooth movement has not been measured. The purpose of this study was to investigate changes in biomechanical property of the periodontal tissue during canine retraction, in terms of tooth mobility. The upper canines on both sides of ten orthodontic patients were moved in the distal direction for about four weeks with an initial force of 200 gf. An amount of tooth movement and a magnitude of tooth mobility were measured every 3 or 4 days during retraction. A distally directed force up to 500 gf was continuously applied to each canine and tooth mobility was measured with a noncontact type of eddy current displacement sensor. A two-dimensional finite element model was constructed and displacements of the finite element model were calculated with various Young's moduli in loading with a 100 gf force in the distal direction. In comparison with the magnitudes of the tooth mobility, Young's modulus of the periodontal membrane before retraction and the influence of the biomechanical factors on changes in tooth mobility were investigated. The tooth movement curve was divided into three phases; an initial phase, a lag phase and a post-lag phase. The magnitudes of tooth mobility at the initial phase were significantly larger than those before retraction within the range of 250 gf to 500 gf and these magnitudes decreased during the lag phase. The magnitudes of tooth mobility at the post-lag phase significantly increased, within the range of 50 gf to 500 gf, than those before retraction. As a result of curveliniar regression analysis, the tooth mobility curves approximated to delta = AFB, where delta and F denote tooth mobility and force respectively. The coefficients A and B changed according to the phases of tooth movement. An inclination of the tooth mobility curve expressed by a tangent at the 400 gf force was the largest at the initial phase, and this inclination at the 100 gf force was the largest at the post-lag phase. Young's modulus of the periodontal membrane before retraction was determined to be approximately 35 gf/mm2 and Young's modulus of the periodontal membrane was the most important factor on the increase of tooth mobility. Tooth mobility significantly varied associated with tooth movement. It was indicated that biomechanical property of the periodontal tissue changes in response to each phase of tooth movement. In particular, Young's modulus of the periodontal membrane decreased at the post-lag phase of the orthodontic tooth movement.
Cuspid↗
Recent results concerning physiological tooth movement and anterior guidance.
Physiological tooth movements during mandibular excursions with and without occlusion have been considered. Using electronic and pantographic techniques, anterior guidance and tooth movements during simulated mastication (without a bolus) were investigated. Investigations in the absence of occlusion showed that elastic deformation of the mandible gave rise to tooth movements. During occlusion three-dimensional tooth movements of up to 60 micro m in each direction occurred. Pantographic measurements of anterior guidance showed that each type of occlusion (balanced occlusion, group function and canine protected occlusion) has its own characteristic. Only canine protected occlusion gave values which corresponded to physiological data.
Cuspid↗