Objective: The aim of this study was to evaluate the performance of a new glass ionomer filling material (ChemFlex™) using the atraumatic restorative treatment (ART) approach in class I cavities in the permanent dentition of Latvian schoolchildren. Methods: A total of 63 fillings (40 test and 23 control) were placed using the ART technique in 41 schoolchildren in Riga at the Stomatology Institute of the Medical Academy of Latvia. These fillings were then blindly assessed after 2 years. Results: The complete success rate for both the test and the control material fillings were 92.5 and 94.9%, respectively. Conclusion: The new glass ionomer filling has shown a good performance in terms of retention, marginal failure and fractures in class I cavities.