## 1 Introduction  
During mixed dentition, important dento-alveolar, occlusal and skeletal changes occur and can be diagnosed. Some of these require early treatment (interceptive) in order to prevent the aggravation of the problem during the active growth period. The main clinical problem that often arises is the provision of an anchorage zone with the included permanent tooth. This may be provided by usage of personal rigidly printed dento-alveolar anchorage (PDaA), which connects these teeth. Orthodontic mini-implants are not applicable in vestibular areas with developing tooth germs. The available stable permanent teeth in the early mixed dentition are often an insufficient support unit, which is placed away from the active area. The use of a metal orthodontic PDaA, designed and printed digitally, has expanded the limits of orthodontic treatment, especially in its interceptive phase. The establishment of impacted first permanent molars and incisors in the period of early mixed dentition is most favourable. In this period of dentition development, sufficiently stable supporting teeth are not available, root resorption processes are observed in the temporary molars and the germs of the permanent teeth develop in the alveolar ridges.  
Advancements in digitization have created many possibilities for customizing orthodontic appliances. CAD-CAM technologies allow one to perform a momentary intraoral scan of both dental arches and their occlusal relationships and carry out a digital analysis of all paraclinical studies as well as create a computerized individual design of appliances or additional auxiliary devices [1; 2; 3; 4]. In orthodontics, most printed devices are derived from biocompatible composites or metal. Today, the 3D-printing of laser-sintered metal orthodontic devices is the basis for the development of modern orthodontics [5; 6]. A reduction in the stages of an appliance's production (intraoral scanning-computer design-printing) occurs in combination with the minimization of human error and without the necessity of heavy physical activity [7; 8]. The modern laser-sintered orthodontic appliances provide exceptional detail precision [9; 10; 11; 12; 13] and have predictable tooth movement geometry [8]. The construction of the appliances can be adjusted to the geometry of the forces for the biomechanical action and moments produced by it. The extreme accuracy of the devices does not allow for the occurrence of residual tension voltages. There is already a lot of research on the topic in regard to their mechanical properties, electrochemical behaviour and biocompatibility. Most often, the printed devices are made of cobalt-chromium (Co-Cr) alloys [10], which are strong. Their mechanical properties, such as hardness, strength and elasticity modulus, are known to be optimal for appliance design. The printed devices should not be dangerous to the hard tissues (teeth) on which they are placed and debonded; therefore, they can also undergo deformation [14]. The appliances must be strong enough to withstand masticatory forces during chewing without any permanent deformation [15; 16]. They increase the predictability of the result but require the orthodontist's technical knowledge and equipment financing [17; 18].  
As every orthodontic force produces a reactive force of equal magnitude, the success of the orthodontic treatment depends on the anchorage and elimination of side effects, including unwanted tooth movement or tooth segments.  
Our aim is to describe a fully digitally designed appliance for providing anchorage during the orthodontic surgical traction of impacted teeth in the mixed dentition period. We shall critically describe and discuss metal-printed appliances to support the orthodontic treatment.