Purpose: To evaluate the efficacy in dental biofilm (DB) removal between electric toothbrushes versus manual toothbrushes in primary dentition using an Image Analysis System (IAS) of digital photographs.<br/> Methods: A prospective, randomized, controlled, blind, crossover clinical trial was conducted for 12 weeks with children between four to six years of age. The amount of DB was evaluated at zero, four, eight and 12 weeks. The degree of acceptance of the type of toothbrush used by the child was assessed at week 12.<br/> Results: Twenty-two children participated and 176 photographs were taken, with 1,408 images of primary incisors being digitally analyzed by IAS. DB was significantly reduced by both types of toothbrushes on day zero (manual=7.44±1.83 percent; electric= 9.80±2.03 percent) and at week four (manual=8.57±2.23 percent; electric= 5.85±2.10 percent). However, there was no statistically significant difference in DB reduction when both types were compared. After week four, when compared prospectively, there was a statistically significant reduction (P <0.05) of DB for the electric toothbrush only. Electric toothbrushes had a significantly greater acceptance by the participants (P <0.01).<br/> Conclusion: Electric toothbrushes eliminated DB better and were more accepted by the children than manual toothbrushes.