RESUMEN
BACKGROUND: The patients' request for treatment with clear aligners is constantly increasing. The aligners permit to the clinicians a valid way to solve a lot of orthodontic cases but the patients' compliance and the clinicians' capabilities and knowledge of the technique is fundamental for the outcome. METHODS: Seventy-two digital models of 18 consecutive patients treated with Invisalign and Smart Track aligners for 14 weeks were analyzed. The operator positioned 24 points on each model and were obtained the values of arch depth and perimeter of arch before and after the treatment. The variations of measurement were calculated with t student test. RESULTS: A decrease of arch depth and perimeter was found from t0 to t1 and the most relevant difference was observed in the upper arch depth with a decrease of 1.3 mm and in the upper arch perimeter with a difference of 1.1 mm. CONCLUSIONS: There was always a decrease of the values of arch depth and arch perimeter at the end of the treatment, especially in the upper arch. These changes must be considered by the clinicians to perform a better treatment to obtain the most predictable results and a patient's higher satisfaction.