The impact of Digital Technologies in Orthodontics: 3D Imaging, Additive manufacturing, In Vitro testing and Clinical Outcomes of Materials and Therapeutic Devices

The aim of this PhD thesis was to evaluate, through both in vitro and in vivo studies, the impact of digital orthodontics on 3D imaging and the additive manufacturing of appliances. A total of ten papers were included: six of an experimental nature and four illustrating the application of the topics discussed herein. With regard to 3D imaging, two experimental studies were conducted. The first assessed the preference between intra-oral scanning and alginate impressions in children, revealing that intraoral scanning is faster, more comfortable and it is preferred by young patients. The emergence of intra-oral scanning has enabled the acquisition of 3D models, which serve as a valuable tool for evaluating various treatment outcomes without exposing patients to radiation. The accuracy of 3D model superimposition was examined in a sample of adult patients, demonstrating that it is a reliable and reproducible method. However, further research is necessary to establish a reliable reference area for these superimpositions, particularly in growing patients or those presenting significant changes in the occlusal plane. When combined with cephalometric radiographs, this approach serves as an effective means of illustrating 3D tooth movement without the superimposition of other anatomical structures, as demonstrated in the paper entitled “A diagnostic and treatment planning checklist for vertical problems in orthodontic patients” included in the appendix. Stereolithography has enabled the conversion of intra-oral scans into dental models or appliances that are constructed directly from these .stl files. The 3D printing process is performed by the sequential deposition of resin layers, utilizing a variety of printers and resins available on the market, with new materials continually being introduced. As a result, extensive evaluation is required to determine the properties of these materials and the methods by which they are handled. Accordingly, the in vitro studies assessed the physical characteristics of different resins, considering variables such as printing orientation, exposure to water ageing, and the resultant surface roughness and gloss. The findings indicated that the printing orientation and water ageing affect flexural strength and modulus of 3D printing resins for occlusal splints, as well as surface roughness and gloss of 3D printed aligners. However, perhaps the most significant transformation in orthodontics brought about by the digital workflow has been the development and improvement of aligners. This represents a complete shic, both aesthetically and mechanically, from conventional fixed appliances. Aligner treatment now offers numerous possibilities, ranging from outsourced to in-house fabrication, each utilizing different printers and materials. The production of in-house aligners remains somewhat cumbersome, as illustrated by the three practical guidelines included in the appendix of this thesis. Nevertheless, there exists a clinical niche for their use, particularly in low complexity cases. The expansion of the upper arch using in-house aligners was evaluated in a prospective clinical study, with results demonstrating that it is more effective in the premolar area than in the canine area, with canine torque control that is affected by agachment positioning. Despite these advancements, much remains to be explored in aligner therapy, especially as treatment outcomes now rely heavily on patient cooperation. Patient cooperation has long posed challenges for orthodontists, a situation further complicated when extra-oral appliances are required. The advent of 3D printing offers the potential to customize these devices, aiming to enhance patient comfort. This hypothesis was explored by comparing standard facemasks with those personalized via additive manufacturing in a crossover randomized clinical trial. While there was a slight preference for the personalized facemasks, the findings ultimately revealed no significant differences in terms of wear time, pain, or sleep-related discomfort. Larger-scale studies are necessary to determine whether the customization of facemasks is truly beneficial.