Abstract:Objective: To compare the masticatory performance (MP) of patients with old removable partial denture (RPD), recently inserted RPD and already adapted RPD by means of the simple sieve test. Material and Methods: Twenty-nine adult (>18 years old) volunteer patients were recruited, with lower and upper RPD, excluding total edentulous subjects in the upper and lower jaw, with temporomandibular disorders, severe periodontal disease, mental disability or systemic disease compromising the masticatory or nervous system. Dentures were designed and fabricated by an expert operator. MP was evaluated in old RPD (MP1), recently inserted RPD (MP2) and adapted RPD (MP3). The simple sieve test used was Edlund-Lamm in percentage of MP, using Optosil® Comfort condensation silicone tablets, with standard sizes (5.0x20mm). In each phase, the patient chewed the tablet with 20 masticatory strokes. The crushed fragments were dried at 80°C for 60 minutes and weighed on an analytical scale. A multiple vibration sieve analysis was performed, using sieves with opening sizes of 2.8mm and 1.4mm. Shapiro-Wilk test and Anova test with Bonferroni correction were performed. Results: It was observed that MP1 presented a mean of 8.40% (SD±5.59), MP2 a mean of 8.56% (SD±5.56), and MP3 a mean of 18.26% (SD±8.12). There was a significant difference (p<0.05) between the MP1-MP3 groups, as well as between the MP2-MP3 (p<0.05). Conclusion: There is a significant increase in MP thirty days after the insertion of RPD, checkups, and adjustments performed by the dentist.