Experimental and numerical analysis of the biomechanical characteristics of orthodontic mini-implants

Objective: Mini-implants are being utilised as anchorage units in orthodontic treatment. Nevertheless, there seem to be influencing factors that interfere with their clinical performance. The aim of this study was to experimentally and theoretically examine four different parameters, which may have an influence on the primary stability of orthodontic mini-implants. These were 1) implant type, 2) implant length, 3) implant diameter and 4) insertion angle. Material and Methods: A total of 90 mini-implants were inserted in fresh segments of bovine ribs. Implants were of two types, the Aarhus and the LOMAS mini-implant, of two lengths (7 mm and 9 mm) and of two diameters (1.5 mm and 2 mm, LOMAS only). A closed NiTi coil-spring was attached to each mini-screw. Half of the preparations were loaded with a low force of 0.5 N, the other half with a high force of 2.5 N. Mini-implant deflections during force application were non-invasively registered using a 3D laser-optical system. A subsequent finite element analysis of the applied force systems and the resulting mini-screw deflections was performed. Results: In the small force group, implant displacements showed no statistically significant difference according to the investigated parameters. In the high force group the 9mm mini-implants displaced significantly less (mean 11±8 μm) than the 7 mm long (mean 22±11 μm, p Conclusion: Implant length and implant diameter become statistically significant influencing parameters on implant stability only when a high force level is applied. Numerical results showed a good correlation to the experimental ones.Experimentelle und numerische Untersuchung des biomechanischen Verhaltens orthodontischer Mini-Implantate Seit einigen Jahren werden verstärkt orthodontische Mini-Schrauben oder Mini-Implantate zur Verankerungsverstärkung eingesetzt. Trotz zahlreicher Vorteile bestehen nach wie vor widersprüchliche Ansichten in Bezug auf Einflussfaktoren, die ihre klinischen Eigenschaften bestimmen. Ziel dieser Untersuchung war es, vier verschiedene Parameter experimentell und theoretisch zu untersuchen, die einen Einfluss auf die Stabilität der Verankerungsschrauben haben könnten. Diese waren: 1) Implantattyp, 2) Implantatlänge, 3) Implantatdurchmesser und 4) Positionierung. Zwei verschiedene Kräfte, eine geringe von 0,5 N und eine höhere von 2,5 N wurden durch eine Nickel-Titan-Zugfeder (NiTi) angelegt. Das Material bestand aus 90 Mini-Schrauben, die in frische Segmente von Rinderrippen eingesetzt wurden. Jeweils vierzig Aarhus- (American Orthodontics, Wisconsin, USA) und Lomas-Schrauben (Mondeal, Mühlheim, Deutschland) in zwei unterschiedlichen Längen (7 mm, 9 mm) und mit einem Durchmesser von 1,5 mm wurden untersucht. Die Lomas-Schrauben standen in der Länge 7 mm auch mit dem Durchmesser 2 mm zur Verfügung, um den Einfluss des Durchmessers untersuchen zu können. Die Mini-Schrauben wurden mit zwei Winkeln positioniert, jeweils eine Hälfte senkrecht, die andere Hälfte mit einer Angulation von 45° nach mesial. An den Präparaten wurden Kraft/Auslenkungs-Diagramme im Mobilitäts-Mess-System (MOMS) des Labors der Stiftungsprofessur für Oralmedizinische Technologie, mit Kräften bis 0,5 N und 2,5 N in distaler Richtung gemessen. Die NiTi-Feder wurde auf den Hals des Mini-Implantates an der einen Seite und auf dem mechanischen 3D Kraft/Drehmoment-Sensor an der anderen Seite befestigt. Die Kraftrichtung war parallel zur Knochenoberfläche und zur Horizontalen. Jede Einzelmessung wurde zweimal durchgeführt. Anschließend wurden die Präparate in einem µCT (µCT40, Scanco Medical) gescannt und die Geometrien wurden mit dem speziell für diese Aufgabe entwickelten Programm ADOR-3D rekonstruiert. Die so entwickelten Finite-Elemente(FE)-Modelle wurden im FE-System MSC.Marc/Mentat2007r1 berechnet. Die Statistik umfasste eine univariante Varianzanalyse (three-way ANOVA) zur Analyse des Einflusses der Parameter Schraubentyp, Länge, Positionierung und Kraft, einen Studentschen t-test für die Auswertung des Durchmessers und einen Altman-Bland-Test für den Vergleich der beiden Messdurchgänge und den Vergleich zwischen den experimentellen und numerischen Ergebnissen. Zusätzlich wurde ein Youden-Plot für den Vergleich der experimentellen und numerischen Ergebnisse angefertigt. Die Ergebnisse zeigten, dass sich das biomechanische Verhalten der Mini-Schrauben zwischen den zwei Kraftgruppen unterschied. Wenn eine geringe Kraft von 0,5 N angewendet wurde, wurden Auslenkungen des Schraubenkopfes von 4 bis 9 µm in Kraftrichtung gemessen, die Rotationen lagen bei 0,006° bis 0,025°. Die Ergebnisse schwankten zwischen den verschiedenen Mini-Implantaten, die Varianzanalyse zeigte jedoch keine statistisch signifikanten Unterschiede in den Auslenkungen. Bei der Anwendung der höheren Kraft von 2,5 N konnte festgestellt werden, dass die 9 mm langen Mini-Implantate eine statistisch signifikant kleinere Auslenkung (Mittelwert 10±7 μm) als die 7mm langen (Mittelwert 22±11 μm, p Zusammenfassend kann festgestellt werden, dass in klinischen Situationen, bei denen die angewandte Kraft kleiner als 1 N ist, wie zum Beispiel bei Zahnintrusionen oder indirekter Verankerung, Mini-Implantate mit kleineren Dimensionen zuverlässig eingesetzt werden können. Bei Einsatz höherer Kräfte sind entsprechende Mini-Implantat-Dimensionen entscheidend für die Primärstabilität. Jedoch sind beim klinischen Einsatz sowohl der Abstand der Zahnwurzeln als auch die anatomische Lage sorgfältig zu bedenken

Craniofacial morphology and dental maturity in children with reduced somatic growth of different aetiology and the effect of growth hormone treatment

Abstract Children with reduced somatic growth may present various endocrinal diseases, especially growth hormone deficiency (GHD), idiopathic short stature (ISS), chromosomal aberrations, or genetic disorders. In an attempt to normalize the short stature, growth hormone (GH) is administered to these children. The aim of this literature review was to collect information about the craniofacial morphology and dental maturity in these children and to present the existing knowledge on the effect of GH treatment on the above structures. This review demonstrated that regardless of the origin of the somatic growth retardation, these children show similar craniofacial features, such as short length of the cranial base and the mandible, increased lower facial height, retropositioned mandible, and obtuse gonion angle. On the other hand, dental maturation does not demonstrate a specific pattern. Except for the above findings, muscle alterations seem to be present in individuals with short stature, who present low body muscle mass and strength, while studies on their craniofacial muscles seem to be lacking. After GH administration, the exact amount and pattern of craniofacial growth is unpredictable; however, the facial convexity decreases, mandibular length increases, and posterior facial height increases, while tooth eruption remains unaffected. Thus, it is of great importance to gain more insight into the craniofacial growth of treated and untreated children with reduced somatic growth so that the influence of GH therapy on the various craniofacial structures could be ascertained and proper orthodontic treatment could be selected

Crouzon Syndrome: a Comprehensive Review

Crouzon syndrome is a rare genetic disorder with autosomal dominant inheritance. The underlying pathological process is premature synostosis of the cranial sutures with subsequent phenotypic alterations of the affected person. A review of the literature has been conducted in order to resume the overall characteristics of Crouzon syndrome such as craniomaxillofacial malformations, clinical features, dentoalveolar characteristics, aesthetic impairments, and psychological background, as well as, the different therapeutic procedures, which combine surgical and orthodontic interventions. Facial and functional malformations in individuals with Crouzon syndrome could be significantly improved after a series of surgical and orthodontic procedures in almost all cases. A multidisciplinary treatment approach would provide the best outcomes in affected patients

Vertical and Orovestibular Forces Generated by Beta-Titanium and Stainless-Steel Rectangular Wires in Labial and Fully Customized Lingual Bracket Systems

This study aimed to investigate the force values exerted from rectangular wires when combined with conventional labial and fully customized lingual appliances under predefined, idealized activation. Fully customized lingual brackets of two brands Incognito™ (3M Unitek, Monrovia, CA, USA) and WIN (DW Lingual Systems, Bad Essen, Germany) and labial brackets of another brand, discovery® MIM and discovery® smart systems (Dentaurum, Ispringen, Germany), were chosen. Stainless-steel and beta-titanium wires of 0.018” × 0.025” were examined. For IncognitoTM, 0.0182” × 0.025” beta-titanium wires were tested. Intrusion/extrusion and orovestibular movements were performed in a range of 0.2 mm, and the forces were recorded for each 0.1 mm of the movement. Mean values and standard deviations were calculated for all measurements, and ANOVA was performed for statistical analysis. Slight differences were observed between the forces generated from beta-titanium and stainless-steel wires. The same wire generated in some cases 5–53% higher forces with the lingual appliance due to the vertical orientation of the long walls during intrusion/extrusion and increased wire stiffness at the anterior region. Beta-titanium and stainless-steel 0.018” × 0.025” wires can generate similar force values during the final stages of the orthodontic therapy; thus, possibly only one of the two alloys could be used in each orthodontic wire sequence

Dental, Skeletal, and Soft Tissue Changes after Bone-Borne Surgically Assisted Rapid Maxillary Expansion: A Systematic Review and Meta-Analysis

(1) Background: For non-growing patients with marked transverse maxillary deficiency, bone-borne surgically assisted rapid maxillary expansion (SARME) has been proposed as an effective treatment option. Objective: To evaluate the dental, skeletal, and soft tissue changes following bone-borne SARME. (2) Methods: An unrestricted systematic electronic search of six databases, supplemented by manual searches, was performed up to April 2023. The eligibility criteria included prospective/retrospective clinical studies with outcomes pertaining to objective measurements of dental/skeletal/soft tissue effects of bone-borne SARME in healthy patients. (3) Results: Overall, 27 studies satisfied the inclusion criteria. The risk of bias of the non-randomized trials ranged between moderate (20) and serious (4). For the two RCTs, there were some concerns of bias. Trials with outcomes measured at the same landmarks within the scope of the prespecified timeframe were deemed eligible for quantitative synthesis. Eventually, five trials were included in the meta-analysis. SARME was associated with a statistically significant lengthening of the dental arch perimeter immediately after expansion, along with a marginally significant decrease in palatal depth during the post-SARME retention period. Post-treatment SNA values exhibited no statistically significant change. (4) Conclusion: Current evidence indicates that bone-borne SARME constitutes an effective treatment option for adult patients with maxillary transverse deficiency. Further long-term randomized clinical trials with robust methodology, large sample sizes, and 3D evaluation of the outcomes are needed