The aim of this study is to evaluate the effect of shortening the etching time on the 18-month clinical performance of resin composite restorations in primary molars after partial carious removal. This randomized clinical trial will include subjects (5-10 year-old children) selected at Pediatric Clinic of Federal University of Santa Maria. The sample will consist of 70 primary molars presenting active cavitated carious lesions (with radiographic involvement of the outer half of the dentin), located on the occlusal surface. The sample will be randomly divided into two groups according to the etching time of the dentin prior adhesive application (Adper Single Bond 2; 3M ESPE): recommend by manufacturers (15 seconds) and half-reduced etching time (7 seconds). The restorations will be clinically followed every 6 months for up to 18-month using the FDI criteria for clinical evaluation. Survival estimates for restoration longevity will be evaluated using the Kaplan-Meier method.

The aim of this study is to evaluate the effect of shortening the etching time on the 18-month clinical performance of resin composite restorations in primary molars after partial carious removal. This randomized clinical trial will include subjects (5-10 year-old children) selected at Pediatric Clinic of Federal University of Santa Maria. The sample will consist of 70 primary molars presenting active cavitated carious lesions (with radiographic involvement of the outer half of the dentin), located on the occlusal surface. The sample will be randomly divided into two groups according to the etching time of the dentin prior adhesive application (Adper Single Bond 2; 3M ESPE): applying of 35% phosphoric acid by 15 s - recommend by manufacturers and half-reduced etching time (7 s). The restorations will be clinically followed every 6 months for up to 18-month using the FDI criteria for clinical evaluation. Survival estimates for restoration longevity will be evaluated using the Kaplan-Meier method.

Inclusion Criteria:

*Active carious lesion in middle dentin limited to the occlusal surfaces of primary molars.

Exclusion Criteria:

• Children who refuse or fail to cooperate with the completion of clinical procedure;
• Teeth without antagonist;
• Carious lesions in inner half of dentin;
• Presence of painful symptoms or signs of pulpal changes.