Objectives: To assess aligners’ potential to induce labiopalatal bodily movement or achieve torque control of incisors and evaluate the scientific evidence related to the impact of aligner modifications and their recommended geometries. Materials and methods: The electronic databases PubMed, Science Direct, Cochrane Central Register of Controlled Clinical Trials, IEEE Xplore, National Library of Medicine Catalog and Google Scholar were screened from January 1991 to February 2020. Quality assessment was performed using an individual scoring system and a 4-point grading system based on the Grading of Recommendations Assessment, Development and Evaluation tool. The studies were classified according to the aligner system, material and aligner modifications used. Results: Six studies were included for qualitative analysis: two experimental in vitro studies, one prospective study and three retrospective clinical trials. In total, the quality score for all the included studies was 26.2 points, corresponding to a grade C (low quality of evidence). The labiopalatal bodily movement and torque control of incisors using aligners were transmitted inconsistently. When comparing aligner modifications, the accuracy for torque movement was higher using Power Ridges (Align Technology, San Jose, CA, USA) (51.5%) than attachments (49.1%), with torque values of 7.9 and 6.7 Nmm, respectively. As yet, there is no specific recommendation for the modification geometry. Conclusion: The potential of aligners to induce labiopalatal bodily movement or achieve torque control of incisors without modifications is limited. The implementation of aligner modifications and adequate aligner system–dependent staging might increase the efficacy of these forms of movement. More studies, especially randomised controlled trials, are required to clarify the predictability of these tooth movements. Keywords: aligner modifications, bodily tooth movement, forces, incisors, moments, root torque

Neben der Thematisierung allgemeiner diagnostischer und therapeutischer Aspekte bei Zahnnichtanlagen fokussiert dieser Beitrag auf die Entscheidungspfade bei Aplasie der oberen seitlichen Schneidezähne. Bei Vorliegen dieser Anomalie basiert die individuell optimale Therapie üblicherweise entweder auf einem orthodontischen Lückenschluss oder einer prothetischen Lösung (Adhäsivbrücke oder Implantatkrone). Dabei stehen insbesondere ästhetische Faktoren im oberen Frontzahnbereich im Fokus, was durch drei Patientenbeispiele praktisch demonstriert und vertieft wird. Die Einführung der skelettalen Verankerung von Multibracketapparaturen mittels Mini-Implantaten hat das Spektrum des orthodontischen Lückenschlusses beträchtlich erweitert, sodass mittlerweile kollaterale Aspekte von Malokklusionen weitgehend unabhängig von den Therapieoptionen bei Zahnnichtanlagen betrachtet werden können. Ein entscheidender Faktor ist die gute interdisziplinäre Kommunikation zwischen Zahnarzt, Kieferorthopäde, Oralchirurg und Eltern bzw. Erziehungsberechtigten. Üblicherweise sollte diese Absprache spätestens zum Beginn der späten Wechselgebissphase abgeschlossen sein. Manuskripteingang: 26.11.2021, Manuskriptannahme: 14.02.2022 Keywords: Dentale Aplasie, Nichtanlage, obere seitliche Schneidezähne, obere seitliche Inzisivi, OK-2er, Therapieoptionen, Behandlungsstrategie

Objectives: For experimental evaluation of sequential aligner systems, the conventional sequence of aligner thickness (0.5 to 0.8 mm) and a novel sequence using thinner 0.4- and 0.3-mm films were investigated biomechanically in four mechanical in-vitro studies. Materials and methods: The first two studies focused on determining mechanical loads exerted during labio-palatal translation of a maxillary central incisor and derotation of a mandibular canine when using aligners with conventional thicknesses of 0.5 to 0.75 mm. The third and fourth studies examined the mechanical load during different movements of a maxillary central incisor by use of 0.3- and 0.4-mm novel, thinner aligners. All experiments were performed on specifically designed test setups equipped with acrylic casts from which the corresponding measurement tooth was separated and mounted on a three-dimensional (3D) movement unit via a 3D force-moment (F/M) sensor. Results: Even for small movements of 0.5 mm and 10 degrees, quite high F/M values, up to 8.4 N and 89.2 Nmm, respectively, were recorded for the 0.5-mm aligner. Use of aligners thermoformed from novel 0.4-mm film resulted in mean reduction in force and moment of 35% and 45%, respectively, for translation and rotation of the maxillary right central incisor (tooth 11). Aligners fabricated from 0.3-mm film showed insufficient form stability during repeated seating and removal from the test cast, and should therefore also be unsuitable for clinical application. Conclusions: When using the thinnest 0.5-mm film, the risk of overloading the periodontal structures is quite high. Based on these in-vitro experiments, a novel aligner thickness sequence is recommended using 0.4-, 0.5- and 0.75-mm aligners. This sequence substantially reduces the F/M values exerted by the first and thinnest aligner and ensures relatively constant load increases for each individual setup step. Keywords: aligner sequence, aligner thickness, force, orthodontic aligner, overloading

Introduction: An increase in transverse maxillary width can be facilitated using tooth-borne, bone-borne or combined tooth-bone-borne appliances. The advantage of bone-supported expansion is the direct transfer of the expansion forces on to the bone, thus leading to a reduction in the negative side effects such as buccal tipping of the anchor teeth, root resorption and bone dehiscence associated with dental anchored expansion appliances. Ready-made skeletal anchored distractors are mostly fixed submucosally in the bone. However, this procedure is more invasive, patient comfort is reduced and the activation process complicated. Materials and Methods: A new patient-specific distraction device was developed using a standard Hyrax expansion screw made of titanium and standard titanium locking miniplates. After individual positioning and fixation of the locking plates and the Hyrax screw on the model of the patient's jaw, these components were laser welded. The appliance is fixed intraoperatively using standard-locking mini screws. Results: Treatment with this method was successfully completed in five cases. The activation of the screw by the patient seemed to be similar to standard removable appliances or dental anchored rapid maxillary extension appliances and was therefore very reliable. Removal of the devices is less invasive in comparison to the submucosally fixed appliances due to the epimucosal plate position. Conclusion: This newly described method combines the advantages of the hyrax appliances with skeletal anchored distractors. Patient compliance is increased, and the interdisciplinary treatment of these patients between maxillofacial surgeons and orthodontists is supported. Keywords: rapid palatal expansion, distraction osteogenesis