The purpose of this study is to evaluate and compare the clinical retention of a resin-based fissure sealant placed with prior application of etch-and-rinse and self-etch modes of universal adhesives.

Sealants will placed on previously unsealed, caries-free permanent first molars, employing a split-mouth design. 100 patients will be included the study. The teeth will be randomized into eight groups according to the adhesive systems and modes placed under the tested resin-based sealant.

Group1: Acid-Etch + Fissure sealant (ClinPro 3M ESPE, U.S.) (Control arm) Group2: All Bond Universal (Bisco Inc., Schaumburg,IL, U.S.) - with self etch technique + Fissure sealant ; Group3: All Bond Universal - total etch technique + Fissure sealant Group4: Scotchbond (Single Bond) Universal (3M ESPE, U.S.) - self etch technique + Fissure sealant Group5: Scotchbond (Single Bond) Universal - total etch technique + Fissure sealant Group6: Clearfil Universal Bond (Kuraray, Tokyo, Japan) - self etch technique + Fissure sealant Group7: Clearfil Universal Bond- total etch technique + Fissure sealant Group8: Single Bond Plus (3M ESPE)- total etch technique + Fissure sealant

Clinical assessments will be performed according to modified USPHS criteria at 3, 6, 12, 18 and 24 months. Retention, seconder caries, marginal adaptation and marginal discoloration of the sealants will be evaluated.

The data will be analyzed statistically using Fisher's Exact test and Kaplan-Meier analysis.

Inclusion Criteria:

• Teeth having clinical indication of sealing with pit and fissure sealant.
• Patients with four fully-erupted permanent molars, with unstained, caries-free and unsealed pit and fissures.

Exclusion Criteria:

• Patients having incipient carious lesions, fewer erupted molars or teeth without pits on buccal/palatal surfaces.
• Patients with systemic diseases.