ANAMARIA BECHIR, MARIANA PACURAR, EDWIN SEVER BECHIR, MONICA RALUCA COMANEANU,MANUELA CHIBELEAN CIRES, MARIUS MARIS, HORIA BARBU AESTHETIC IMPORTANCE OF RESIN BASED DENTAL MATERIALS USED FOR ORTHODONTIC APPLIANCES Orthodontic appliances are intraoral devices used to induce changes in relations between the teeth and the underlying bone structures. Removable orthodontic appliances, which contribute to the alignment of misaligned teeth and to the development of maxillaries, are not fixed to teeth and can be inserted/removed easily on/off the teeth of the dental arches. The aim of this study was to evaluate some characteristics of removable orthodontic appliances achieved by two different technologies (heat-curing and vacuum-forming), realised by using two dental materials (Superacryl Plus-SpofaDental thermo-cured acrylic resin and Biocryl® C and Biocryl® M -Scheu thermoplastic materials). The study included 123 adolescent patients, to which were manufactured one or two removable orthodontic appliances, on one or both of the dental arches. A total of 141 removable orthodontic appliances were manufactured for the selected adolescent patients. The manufacturing of all types of removable orthodontic appliances followed the same technological procedures, specific to each type of used material. The results of the study demonstrate that the aesthetic effect of the two dental materials presented different results, and the best results were observed at the orthodontic appliances achieved by the vacuum-forming technology, using Biocryl® C and Biocryl® M–Scheu thermoplastic materials.