<p>To evaluate the synergistic effect of erbium lasers irradiation and remineralizing agents on the surface microhardness of primary tooth enamel. A total of 380 primary molars were collected. Teeth were embedded in acrylic resin such that only their buccal surface were exposed. The baseline (A) surface microhardness (SMH) was measured and the teeth were allocated into 19 groups: Group-1-Positive control, Group-2-Negative control, Group-3-Er: YAG laser, Group-4- Er, Cr: YSGG laser, Group-5-Fluorovil^®, Group-6-Fluor Protector^® varnish, Group-7-MI Paste^®, Group-8-MI Paste Plus^®, Group-9-MI varnish^®, Group-10-Er: YAG + Fluorovil^®, Group-11-Er: YAG + Fluor Protector^® varnish, Group-12-Er: YAG + MI Paste^®, Group-13-Er: YAG + MI Paste Plus^®, Group-14-Er: YAG + MI Varnish^®, Group-15-Er, Cr: YSGG + Fluorovil^®, Group-16-Er, Cr: YSGG + Fluor Protector^® varnish, Group-17-Er, Cr: YSGG + MI Paste^®, Group-18-Er, Cr: YSGG + MI Paste Plus^® and Group-19-Er, Cr: YSGG + MI Varnish^®. After the planned enamel surface treatments, SMH of enamel (B) was again measured. ment. The samples were then subjected to a demineralization-remineralization cycle, followed by the SMH measurement (C). The highest SMH after the demineralization-remineralization cycle (C) was recorded with the use of Er: YAG laser in combination with Fluor Protector^® varnish (Group 11) (418.40 ± 4.17), while the lowest value was seen with the use of Er, Cr: YSGG laser alone (Group 4) (259 ± 15.53). The results indicate that irradiation with erbium lasers, followed by the application of remineralizing agents, has a synergistic effect in increasing enamel SMH. This suggests the potential use of such treatments as a preventive measure for dental caries.</p>