ABSTRACT
INTRODUCTION: The finite element method is a promising tool to investigate the material properties and the structural response of the periodontal ligament (PDL). To obtain realistic and reproducible results during finite element simulations of the PDL, suitable bio-fidelic finite element meshes of the geometry are essential. METHODS: In this study, 4 independent coworkers generated altogether 17 volume meshes (3-dimensional) based on the same high-resolution computed-tomography image data set of a tooth obtained in vivo to compare the influence of the different model generation techniques on the predicted response to loading for low orthodontic forces. RESULTS: It was shown that the thickness of the PDL has a significant effect on initial tooth mobility but only a remarkably moderate effect on the observed stress distribution in the PDL. Both the tooth and the bone can be considered effectively rigid when exploring the response of the PDL under low loads. The effect of geometric nonlinearities could be neglected for the applied force system. CONCLUSIONS: Most importantly, this study highlights the sensitivity of the finite element simulation results for accurate geometric reconstruction of the PDL.
Subject(s)
Computer Simulation , Finite Element Analysis , Models, Biological , Periodontal Ligament/physiology , Adolescent , Alveolar Process/physiology , Bicuspid/physiology , Biomechanical Phenomena , Elastic Modulus , Humans , Image Processing, Computer-Assisted/methods , Imaging, Three-Dimensional/methods , Male , Mandible/physiology , Orthodontics, Corrective , Sensitivity and Specificity , Software , Stress, Mechanical , Tomography, X-Ray Computed/methods , Tooth Apex/physiology , Tooth Root/physiologySubject(s)
Dental Alloys/chemistry , Electrochemical Techniques , Nickel/chemistry , Orthodontic Wires , Titanium/chemistry , Adolescent , Biomechanical Phenomena , Cuspid/pathology , Elastic Modulus , Electrochemical Techniques/instrumentation , Female , Humans , Incisor/pathology , Malocclusion/therapy , Maxilla , Orthodontics, Corrective/instrumentation , Palatal Expansion Technique/instrumentation , Rotation , Tooth Eruption, Ectopic/therapy , Tooth Movement Techniques/instrumentation , Tooth, Impacted/therapy , TorqueSubject(s)
Orthodontic Wires , Dental Alloys , Dental Stress Analysis , Elasticity , Humans , Nickel , Pliability , Titanium , Torsion, MechanicalABSTRACT
OBJECTIVE: In an in-vitro experimental set-up, we tested the efficacy of different electric toothbrushes in cleaning teeth with a multibracket appliance. MATERIAL AND METHODS: The efficacy of three sonic and four rotating toothbrushes were compared; the brushes removed artificial plaque from plastic teeth. The amount of removed plaque substitute was determined via a comparative photo-analysis with one picture of the teeth before and one picture after the brushing cycle. Two views of the tooth segment were chosen: one vestibular view and one apical view of the areas behind the bracket wings. All tests were carried out with water, elmex and Pearls and Dents as brushing media. RESULTS: The data showed greater brushing efficacy when Pearls and Dents toothpaste was used. The Sonicare toothbrush was the most efficient. The Sonicmax and rotating Oral-B ProfessionalCare 7000 were also very efficacious. On average, all the other toothbrushes performed less well. All toothbrushes were capable of brushing the undercut areas behind the bracket wings, with plaque removal being the greatest when the Sonicare toothbrush was used together with Pearls and Dents. CONCLUSIONS: The best electric toothbrushes did not demonstrate good tooth cleaning. Longer brushing times, mastery of the proper brushing technique, and/or special toothbrush heads are absolutely necessary.
Subject(s)
Dental Care/instrumentation , Dental Plaque/prevention & control , Orthodontic Brackets , Toothbrushing/instrumentation , Toothbrushing/methods , Dental Care/methods , Equipment Failure Analysis , HumansABSTRACT
To align those teeth in the dental arch that cannot erupt or are displaced, they must be surgically exposed. After the traction device is attached, the tooth is again covered with the mucoperiosteal flap to protect the tissues involved. For this reason, the loss of this traction device must be absolutely avoided in order to prevent another surgical intervention. Here at the University of Ulm, we have developed and tested an optimized traction chain for that purpose. The chain is attached to the tooth with a laser-roughened pad applying the acid-etching technique. The chain links serve as fixation elements for traction devices such as elastic ligatures or piggyback archwires. At the same time, one can determine the distance covered by the tooth by the number of the erupting chain links. We demonstrate the clinical application of this traction device in two cases.
Subject(s)
Extraoral Traction Appliances , Tooth Eruption, Ectopic/surgery , Tooth Migration/surgery , Tooth, Impacted/surgery , Child , Equipment Failure Analysis , Humans , Male , Orthodontic Appliance Design , Treatment OutcomeABSTRACT
BACKGROUND: Second permanent molars often erupt during fixed appliance treatment. When they are to be incorporated into the fixed appliance, it is often not possible to bond the buccal tube in the correct position. MATERIAL AND METHODS: We describe herein a method for aligning second permanent molars by means of a superelastic segmental archwire. This involves the application of a rigid steel archwire extending from the right first molar to the left first molar for anchorage. This method was investigated in-vitro and in its clinical application. The in-vitro test was carried out with a hexapode simulating the vertical deviation of the second molar. RESULTS: A .016'' x .022'' stainless steel archwire achieved forces of 13 N; a TMA archwire attained 5 N (both with a deflection of 2 mm), and the superelastic late-leveler achieved a maximum force of 1.3 N with a 5 mm deflection. The maximum uprighting torquing moments were 55 Nmm with the stainless steel archwire, 25 Nmm with the TMA archwire and 2 mm deflection, and 4 Nmm with the late-leveler and 5 mm deflection. CONCLUSIONS: The forces and moments of stainless-steel and TMA archwires are too high for the alignment of second permanent molars. The moderate forces and moments occurring with the superelastic late-leveler are capable of intruding, derotating and uprighting the second molar. The vertical component prevents artificial opening of the bite.
Subject(s)
Alloys , Molar , Orthodontic Anchorage Procedures , Orthodontic Appliance Design , Orthodontic Wires , Biomechanical Phenomena , Elasticity , Humans , Tooth Movement Techniques/instrumentation , TorqueABSTRACT
BACKGROUND: Canines or premolars must often be derotated during fixed appliance therapy. If such derotation is carried out on the continuous archwire during the leveling phase, it may lead to unwanted side effects on the neighboring teeth. MATERIAL AND METHODS: At the University of Ulm a .018" x .018" nickel-titanium segmental derotation archwire was developed to start derotation as early as possible. This wire can be inserted during leveling. This system consists of a vertical slot bracket, an elastic ligature, and the derotation archwire. We tested the derotation archwire under clinical application. The occurring forces and torquing moments were measured in vitro via a hexapode and a sensor working in three dimensions. RESULTS: In this investigation, a derotation moment of 12 Nmm occurred in the canine with a 140 degrees archwire rotation and a force in lingual direction. This archwire also made overcorrection possible, since it remains active after complete derotation. A complete derotation of the tooth was effected with no reactivation, due to the wire's superelasticity.
Subject(s)
Bicuspid , Bite Force , Cuspid , Dental Alloys , Nickel , Orthodontic Wires , Orthodontics, Corrective/instrumentation , Titanium , Dental Stress Analysis , Equipment Failure Analysis , Female , Humans , Male , Orthodontic Appliance Design , Rotation , Stress, Mechanical , Tooth Movement Techniques , Treatment OutcomeABSTRACT
AIM AND METHOD: We developed a method to measure the forces occurring during rapid maxillary expansion and carried out the University of Ulm rapid maxillary expansion method, similar to that of Chatellier and Chateau, in ten patients. RESULTS: The forces occurring on the maxilla increased up to 120 N. There was considerable variation in force level from patient to patient. After "rupture" of the midpalatal suture, the forces decreased. The remaining forces seemed to be the result from stress on soft tissue and bone.
Subject(s)
Bite Force , Palatal Expansion Technique , Physical Exertion , Adolescent , Child , Female , Humans , Male , Orthodontic Appliances , Stress, MechanicalABSTRACT
AIM: The aim of this investigation was to employ a new in-vitro testing system for manual toothbrushes in order to distinguish the more effective from those less so for dental care during fixed appliance treatment. MATERIALS AND METHODS: The testing apparatus consisted of a sliding carriage able to execute a horizontal brushing movement, and a row of artificial teeth upon which the various toothbrushes were manipulated. The artificial row of teeth was fixed on a sensor that recorded in all three dimensions the forces and moments caused by the toothbrushes on the toothbrush field. All the tests were executed with a weight of 110 g on a tooth field with a multibracket appliance. Tests were also carried out with five toothbrushes having weights of 200 g, 250 g and 300 g. Here, the decisive target values were 1) the degree of exertion necessary in the brushing direction to move a brush over the artificial teeth, and 2) the maximum force occurring in the brushing direction. High target values indicated high interaction between toothbrush bristles and the surfaces being brushed. RESULTS: From testing five toothbrushes with four different weights, we have established profiles confirming the beneficial and less beneficial properties of certain toothbrushes involving various high contact forces.
