Andrea Wichelhaus

Load-Deflection Characteristics of Superelastic Nickel-Titanium Wires

OBJECTIVE To determine the mechanical properties of commercially available thermodynamic wires and to classify these wires mathematically into different groups. MATERIALS AND METHODS The samples examined were 48 nickel-titanium (NiTi) alloy orthodontic wires commercially available from five manufacturers. These samples included 0.016-inch, 0.016- x 0.022-inch, 0.017- x 0.025-inch, and 0.018- x 0.025-inch wires. The superelastic properties of the NiTi wires were evaluated by conducting the three-point bending test under uniform testing conditions. The group classification was made under mathematically restricted parameters, and the final classification was according to their clinical plateau length. RESULTS The orthodontic wires tested are classified as follows: (1) true superelastic wires, which presented a clinical plateau length of >/=0.5 mm; (2) borderline superelastic with a clinical plateau length of <0.5 mm and >0.05 mm; and (3) nonsuperelastic, with a clinical plateau length of </=0.05 mm. The results showed that the range of products displays big variations in quantitative and qualitative behavior. A fraction of the tested wires showed weak superelasticity, and others showed no superelasticity. Some of the products showed permanent deformation after the three-point bending test. CONCLUSION A significant fraction of the tested wires showed no or only weak superelasticity. The practitioner should be informed for the load-deflection characteristics of the NiTi orthodontic wires to choose the proper products for the given treatment needs.

Mechanical behavior and clinical application of nickel-titanium closed-coil springs under different stress levels and mechanical loading cycles

INTRODUCTION The main advantage of superelastic nickel-titanium (NiTi) products is their unique characteristic of force plateaus, which allow for clinically precise control of the force. The aims of this study were to define the mechanical characteristics of several currently available closed-coil retraction springs and to compare these products. METHODS A universal test frame was used to acquire force-deflection diagrams of 24 NiTi closed-coil springs at body temperature. Data analysis was performed with the superelastic algorithm. Also, the influence of temperature cycles and mechanical microcycles simulating ingestion of different foods and mastication, respectively, were considered. RESULTS Mechanical testing showed significant differences between the various spring types (ANOVA, < or =0.05), but constant intrabatch behavior (t test). Four groups were formed according to the mechanical properties of the springs: strong superelasticity without bias stress, weak superelasticity without bias stress, strong superelasticity with bias stress, and weak superelasticity with bias stress. CONCLUSIONS In sliding mechanics, the strongly superelastic closed-coil springs with preactivation are recommended. In addition, we found that the oral environment seems to have only a minor influence on their mechanical properties.

Biomechanical Analysis of Maxillary Expansion in CLP Patients

OBJECTIVE To carry out a comparative biomechanical analysis of maxillary low force expansion using the quadhelix appliance in cleft and noncleft patients. We also intended to determine whether a sufficient transverse skeletal effect could be achieved among cleft patients using the quadhelix appliance. MATERIALS AND METHODS Three finite element models of the viscerocranium and neurocranium were established in which a transverse expansion of the maxilla using a quadhelix (transverse force of 2 N) was simulated. RESULTS The skeletal effects at the anatomic structures of the midface and the cranial base were far more marked in the simulation models with clefts compared to the morphologically normal state. The highest expansions were measured for bilateral cleft palates. Thus, the expansion measured at the supraorbital margin was 4.7 mustrain with a bilateral cleft, 2.1 mustrain with a unilateral cleft, and only 0.2 mustrain with the morphologically normal state. For bilateral and also for unilateral bone clefts, the skeletal effect of a maxillary low force expansion with a quadhelix on the anatomical structures of the viscerocranium and neurocranium is very much larger than is the case for individuals without clefts. CONCLUSION In the presence of a continuous cleft in the jaw and palate area, orthodontic forces (quadhelix) are apparently already sufficient to allow a skeletal expansion of the maxilla. Maxillary expansion using the quadhelix appliance represents a reasonable alternative to using conventional rapid maxillary expansion appliances among cleft patients.

Influence of decontamination procedures on shear forces after contamination with blood or saliva

INTRODUCTION Despite rapid development in adhesive technology, contamination of bonding surfaces remains a major problem. The aims of this study were to evaluate the influence of contamination on bond strength and to investigate possible decontamination procedures. METHODS Four bonding systems were evaluated for their shear bond strengths under 5 bonding situations: control (without contamination and decontamination); contamination with blood; contamination with saliva; decontamination with water and air, and repriming after blood contamination; and decontamination with water and air, and repriming after saliva contamination. The 25 specimens of each group consisted of composite blocks bonded to bovine teeth. Shear forces were measured with a testing machine after thermocycling. RESULTS The 3 composite primers showed similar behavior. With the exception of Transbond SEP (3M Unitek, Monrovia, Calif) with saliva contamination, all contaminated samples showed greatly reduced shear forces. The control and decontaminated groups showed shear forces about 20 MPa. The resin-modified glass ionomer, however, did not reach clinically sufficient bond strengths in either setup. CONCLUSIONS Decontamination with water and air and repriming is sufficient after contamination with blood or saliva. Etching again is not necessary. The bond strength of Transbond SEP was not significantly altered by saliva contamination and can be recommended for conventional bonding procedures.

Corrosion of Orthodontic Pliers Using Different Sterilization Procedures

Aim:The aim of this study was to investigate the corrosion resistance of orthodontic pliers from several manufacturers following different sterilization procedures, namely heat sterilization and the use of a disinfectant agent (Sekusept Extra N®) in an ultrasonic bath.Material and Methods:Employed in this study were ten distal-end cutters and ten Weingart pliers manufactured by Aesculap®, ETM and Hu-Friedy®, examined under electron microscopy for evidence of corrosion following 500 sterilization cycles. The corrosion data were recorded photographically and graphically. Metallographic microsections were prepared from each pair of pliers and were then analyzed by means of EDX measurements to assess the chemical alloy composition.Results:The light and electron microscopic evaluation showed that both heat sterilization and high level disinfection caused corrosive changes on the pliers. However, the type of corrosion differed between the two sterilization methods. The main type of corrosion with Sekusept Extra N® was pitting, while with heat sterilization it was surface corrosion. Heat sterilization was the type of corrosion that caused the most corrosive changes, regardless of which type of corrosion was considered. However, these results must be viewed critically, because pitting corrosion is obviously a more severe problem than surface corrosion.In comparing the pliers of various manufacturers, differences were noted. However, it was difficult to rank them when the correct maintenance regime was adhered to.The soldered joint gap was revealed to be a specific weak point, and that area proved to be inadequate due to qualities related to their production, particularly in the Hu-Friedy® pliers.Conclusions:This study showed that heat sterilization leads to less corrosion than cold disinfection. Corroded pliers can be restored to a useable condition by re-polishing, though it is important that the instructions for their care be strictly adhered to.ZusammenfassungZiel:Das Ziel dieser Studie war es, kieferorthopädische Zangen verschiedener Hersteller auf ihre Korrosionsbeständigkeit nach mehreren Sterilisationsdurchgängen mit Hitzesterilisation und einem Desinfektionsmittel (Sekusept Extra N®) im Ultraschallbad zu vergleichen.Material und Methoden:Bei der Studie wurden zehn Distalendcutter und zehn Weingartzangen der Firmen Aesculap®, ETM und Hu-Friedy® nach 500 Sterilisationsdurchgängen sowohl lichtmikroskopisch als auch rasterelektronenmikroskopisch auf Korrosionserscheinungen untersucht. Die Korrosionserscheinungen wurden dabei sowohl fotografisch als auch statistisch in einem dafür angefertigten Auswertungsbogen festgehalten. Zudem wurden Schliffe der Zangen hergestellt, über die mit der EDX-Analyse die Legierung der jeweiligen Zangen ermittelt werden konnte.Ergebnisse:Bei den licht- und rasterelektronischen Untersuchungen ergaben sich sowohl nach der Behandlung mit Hitzesterilisation als auch mit der High-level-Desinfektion korrosive Veränderungen an den Zangen. Es stellte sich heraus, dass Lochfraß die Hauptkorrosionsart bei der Behandlung der Zangen mit dem chemischen Desinfektionsmittel Sekusept Extra N® war, während durch Hitzesterilisation hauptsächlich Flächenkorrosion verursacht wurde. Die Hitzesterilisation war das Sterilisationsverfahren, bei welchem unabhängig von der Korrosionsart mehr Korrosionsveränderungen auftraten. Dies muss jedoch kritisch betrachtet werden, da es sich bei Lochfraß um die eindeutig schwerwiegendere Korrosionsform handelt.Wenn man die Hersteller miteinander vergleicht, so schnitten die Zangen unterschiedlich ab. Eine Rangfolge war schwierig aufzustellen, wenn der Anwender sich korrekt an die Pflegehinweise hielt.Der Lötspalt kristallisierte sich als besonderer Schwachpunkt heraus. Herstellungsbedingt waren dort, vor allem bei den Zangen von Hu-Friedy®, insuffiziente Bereiche auszumachen.Schlussfolgerungen:Die Studie zeigt, dass die Hitzesterilisation weniger Korrosionsschäden verursacht als die Kaltdesinfektion. Korrodierte Zangen können durch Politur wieder nutzbar gemacht werden. Es empfiehlt sich jedoch, die Pflegehinweise genau zu beachten.

Active and passive self-ligation-a myth?

OBJECTIVE To compare the frictional behavior of several self-ligating brackets with that of normal brackets both with and without tipping force-moments and in combination with different archwire dimensions. MATERIALS AND METHODS The resistance to sliding (RS) of seven self-ligating brackets, a conventional bracket, and a ceramic bracket with a low-friction clip were evaluated in combination with three different archwires and tipping force-moments of 0 and 10 Nmm. The center of rotation for the measurements was set within the center of the bracket or with a 10-mm offset. Resistance to sliding was measured using an Instron 3344 at a cross-head speed of 10 mm/min at a temperature of 36°C. RESULTS Without a tipping moment, RS increased with the active self-ligating brackets with increasing archwire size. No RS was found for any of the passive self-ligating brackets. The 10-Nmm tipping moment resulted in more RS and was similar for all bracket and archwire combinations. RS was approximately doubled when the center of rotation was located at the bracket rather than with a 10-mm offset. CONCLUSIONS RS between brackets and archwires is highly dependent on the experimental setup. Different setups can result in contradictory results. Almost 1 N of traction force is lost in RS when a moment of 10 Nmm is placed at a rotational center 10 mm from the bracket.

Effective Disinfection of Orthodontic Pliers

Objective:Pathogenic microbes may be transmitted directly from the orthodontist to the patient or from the patient to the doctor, and indirectly from patient to patient. The latter may occur via contaminated instruments or surfaces, and is referred to as cross-contamination. The objective of this study was to evaluate the extent of bacterial contamination of orthodontic pliers and the efficacy of the disinfection techniques applied after clinical use. We also sought to examine under standardized conditions the virucidal, bactericidal and fungicidal effects of disinfection techniques used in practice.Materials and Methods:The efficacy of various disinfection methods was determined after clinical use in-vivo on 10 test subjects and in-vitro with deliberate contamination. The following disinfection methods were tested:1. Iso-Septol spray2. Incidur® spray3. Trough disinfection in combination with 5% Sekusept® Plus solution4. Ultrasound bath in combination with 5% Sekusept® Plus solution5. Thermal disinfectionFor in-vitro contamination we used the test organisms Staphylococcus aureus, Escherichia coli, Candida albicans, Coxsackie virus B4, HSV 1, and Adenovirus type 5. The tests were carried out six to eight times for each organism. The Weingart pliers and distalend cutters were tested. The criteria for effective disinfection were a reduction in infectiosity of five log steps (for bacteria and fungi) or four log steps (viruses). Statistical analysis was carried out using the Wilcoxon and Whitney U-test.Results:The presence of contamination following clinical use was not adequately eliminated with all disinfection methods. The spray methods exhibited shortcomings in disinfection. For the type of contamination defined, trough disinfection with 5% Sekusept® Plus and the Incidur® and Iso-Septol spray disinfection methods provided insufficient disinfection. Conversely, the ultrasound bath with 5% Sekusept® Plus solution and steam disinfection met the criteria for effective disinfection for all microbes. No statistically significant difference was found between the oiled and unoiled states. In some cases, there were slightly higher rates of contamination with the Weingart pliers as with the distalend cutters. However, these were not statistically significant.Conclusions:It should be possible to disinfect lipophilic viruses and the usual bacterial infections adequately with all methods, provided that the use of sprays and trough disinfection is preceded by cleaning with brush and water, followed by drying. With hydrophilic viruses, however, the spray and trough disinfection methods are limited in their efficacy and cannot be considered adequate. Exclusively chemical methods are therefore less effective than thermal or physical-chemical methods.Thermal disinfection and the ultrasound bath in combination with 5% Sekusept® Plus are clearly superior to spray disinfection and trough disinfection alone. The ultrasound bath and thermal disinfection can therefore be recommended for the disinfection of orthodontic pliers. We recommend that the pliers be cleaned beforehand due to their uneven surfaces.ZusammenfassungZiel:Eine Übertragung pathogener Keime ist auf direktem Weg vom Behandler zum Patienten, vom Patienten zum Arzt und auf indirektem Weg von Patient zu Patient möglich—Letzteres über keimbeladene Instrumente oder Oberflächen, die so genannte Kreuzkontamination. Ziel dieser Studie war es, das Ausmaß der bakteriellen Kontamination von kieferorthopädischen Zangen und die Effizienz der Desinfektionsmaßnahmen nach klinischem Gebrauch zu evaluieren. Weiterhin sollte unter standardisierten Bedingungen der viruzide, der bakterizide und fungizide Effekt von in der Praxis verwendeten Desinfektionsmaßnahmen untersucht werden.Material und Methodik:Die Effektivität von verschiedenen Desinfektionsverfahren wurde nach klinischem Gebrauch in vivo an zehn Probanden und in vitro mit gezielter Keimkontamination ermittelt. Die folgenden Desinfektionsverfahren wurden untersucht:1. Iso-Septol Spray2. Incidur® Spray3. Bottichdesinfektion in Kombination mit Sekusept® Plus 5% Lösung4. Ultraschallbad in Kombination mit Sekusept® Plus 5% Lösung5. ThermodesinfektionDie In-vitro-Kontamination erfolgte mit den Testkeimen Staphylococcus aureus, Escherichia coli, Candida albicans, Coxsackievirus B4, Herpes-simplex-Virus Typ I, Adenovirus Typ 5. Die Versuche erfolgten pro Keim sechs- bis achtmal. Untersucht wurden die Weingartzange und der Distalendcutter. Die Kriterien für eine erfolgreiche Desinfektion bestanden in einer Reduktion der Infektiosität um 5 log-Stufen (Bakterien, Pilze) bzw. 4 log-Stufen (Viren). Die statistische Auswertung erfolgte mit dem Wilcoxon- und Whitney-U-Test.Ergebnisse:Die Keimbelastung nach klinischem Gebrauch konnte nicht mit allen Desinfektionsmethoden ausreichend beseitigt werden. Die Sprayverfahren zeigten Lücken in der Desinfektion auf. Bei der definierten Keimkontamination zeigten die Bottichdesinfektion mit Sekusept® Plus 5% und die Spraydesinfektionsmethodiken Incidur® Spray und Iso-Septol Spray eine insuffiziente Desinfektion. Gegensätzlich dazu erfüllten das Ultraschallbad mit 5% Sekusept® Plus Lösung und die Dampfdesinfektion bei allen Keimen die Kriterien für eine erfolgreiche Desinfektion. Zwischen den Zuständen „geölt“ und „nicht geölt“ konnte kein statistisch signifikanter Unterschied festgestellt werden. In einigen Fällen zeigten sich gering erhöhte Kontaminationsraten bei der Weingartzange gegenüber dem Distalendcutter. Diese waren jedoch statistisch nicht signifikant.Schlussfolgerungen:Lipophile Viren und die üblichen bakteriellen Belastungen dürften mit allen Methoden ausreichend desinfizierbar sein, wenn bei der Anwendung von Spray und bei der Bottichdesinfektion eine Vorreinigung mit Wasser und Bürste und anschließendem Abtrocknen erfolgt. Bei hydrophilen Viren zeigt sich jedoch die Grenze der Leistungsfähigkeit der Spray- und Bottichdesinfektion. Sie ist als nicht ausreichend zu erachten. Ausschließlich chemische Methoden sind daher weniger effektiv als thermische oder physikalisch-chemische Methoden.Die Thermodesinfektion und das Ultraschallbad in Kombination mit Sekusept® Plus 5% ist der Spraydesinfektion und ausschließlicher Bottichdesinfektion deutlich überlegen. Das Ultraschallbad und die Thermodesinfektion können daher für die Desinfektion von kieferorthopädischen Zangen empfohlen werden. Eine Vorreinigung der Zangen ist jedoch aufgrund der Unebenheiten der Zangenoberflächen zu empfehlen.

Active and passive self-ligation: a myth? Part 1: torque control.

OBJECTIVE To determine the amount of torque expressed by various self-ligating brackets and to evaluate the influence of active clip designs. MATERIALS AND METHODS Torque moments were measured for nine different bracket types in combination with a 0.019 × 0.025 inch stainless-steel archwire. All active brackets were measured in an open and a closed configuration to evaluate the influence of the self-ligating spring clip. In addition, slot dimensions were optically measured and compared to the torque expression. RESULTS Moments between 3.1 Nmm and 22.6 Nmm were observed at an angulation of 30° between archwire and slot. The amount of torque contributed by the spring clip of active self-ligating brackets was approximately 1 Nmm; 10 Nmm of torque was achieved with most brackets with a 20°-25° angulation between archwire and slot. The slot dimensions ranged from 0.0222 inch (0.563 mm) to 0.0241 inch (0.613 mm). CONCLUSION The influence of the ligature or the active or passive self-ligating mechanism is minimal, and slot dimensions are far more important for the transmission of torque. The amount of torque exerted by the active spring clip is approximately 1/10th of the torquing moments recommended in the literature.

Shear modulus of 5 flowable composites to the EverStick Ortho fiber-reinforced composite retainer: An in-vitro study

INTRODUCTION Although fiber-reinforced composites (FRC) are now available for use as orthodontic retainers, little is known about their bonding properties. Our aim in this study was to investigate the adhesive properties of various composites to a commercially available FRC retainer. METHODS Five flowable composites (Grandio Flow [Voco GmbH, Cuxhaven, Germany], Synergy Flow [Coltène/Whaledent AG, Genf, Switzerland], Tetric Flow [Ivoclar Vivadent AG, Schaan Fürstentum, Liechtenstein], Tetric Flow Chroma [Ivoclar Vivadent AG], and Transbond LR [3M Unitek, Monrovia, Calif) were tested for their shear bond strengths to the EverStick Ortho (Stick Tech Ltd Oy, Turku, Finland) FRC retainer stick. Each group contained 15 samples and underwent 1000 aging cycles between 5 degrees C and 55 degrees C. A testing machine was used to measure the shear bond strengths at the composite-FRC interface. All specimens were visually controlled for the location of the fracture line. RESULTS Typical shear bond strengths were measured at 40 N or 8 MPa. No significant difference was found between the 5 composites (ANOVA, P < or = 0.05). The fracture line was consistently in the FRC retainer. CONCLUSIONS All composites had similar bonding characteristics, and visual inspection consistently showed fractures in the FRC retainer. Because the point of least resistance was in the retainer, we concluded that all tested composites were equally effective.

Direct versus indirect loading of orthodontic miniscrew implants—an FEM analysis

ObjectiveThe mesialization of molars in the lower jaw represents a particularly demanding scenario for the quality of orthodontic anchorage. The use of miniscrew implants has proven particularly effective; whereby, these orthodontic implants are either directly loaded (direct anchorage) or employed indirectly to stabilize a dental anchorage block (indirect anchorage). The objective of this study was to analyze the biomechanical differences between direct and indirect anchorage and their effects on the primary stability of the miniscrew implants.Materials and methodsFor this purpose, several computer-aided design/computer-aided manufacturing (CAD-CAM)-models were prepared from the CT data of a 21-year-old patient, and these were combined with virtually constructed models of brackets, arches, and miniscrew implants. Based on this, four finite element method (FEM) models were generated by three-dimensional meshing. Material properties, boundary conditions, and the quality of applied forces (direction and magnitude) were defined. After solving the FEM equations, strain values were recorded at predefined measuring points. The calculations made using the FEM models with direct and indirect anchorage were statistically evaluated.ResultsThe loading of the compact bone in the proximity of the miniscrew was clearly greater with direct than it was with indirect anchorage. The more anchor teeth were integrated into the anchoring block with indirect anchorage, the smaller was the peri-implant loading of the bone.ConclusionsIndirect miniscrew anchorage is a reliable possibility to reduce the peri-implant loading of the bone and to reduce the risk of losing the miniscrew. The more teeth are integrated into the anchoring block, the higher is this protective effect.Clinical relevanceIn clinical situations requiring major orthodontic forces, it is better to choose an indirect anchorage in order to minimize the risk of losing the miniscrew.