The aim of this study will be to evaluate the effect of reduced dentin etching time on the 6- and 12-months clinical performance of two universal adhesive systems used as etch-and-rinse application mode in non-carious cervical lesions (NCCLs).

Materials & Methods: 140 restorations will be randomly placed in 35 subjects according to the following groups: SUP5 (Scotchbond Universal Plus adhesive on dentin etched for 5 seconds); SUP15 (Scotchbond Universal Plus adhesive on dentin etched for 15 seconds); GBU5 (Gluma Universal Bond adhesive on dentin etched for 5 seconds); GBU15 (Gluma Universal Bond adhesive on dentin etched for 15 seconds). All groups will be light-cured for 10s/1,000 mW/cm2. A resin composite will be placed by applying three increments and each one will be light cured for 20s/1,000 mW/cm2. The restorations will be finished immediately with fine diamond burs and polishers. The restorations will be evaluated at baseline and after 6- and 12-months by using the FDI criteria. The following outcomes will be evaluated: retention, marginal staining, marginal adaptation, post-operative sensitivity and recurrence of caries. The differences among the groups will be calculated using Friedman repeated measures analysis of variance rank (α = 0.05).

This is a four-arm, double-blind, randomized controlled clinical trial. Experimental group 1: 35 non-carious cervical lesions (NCCL) will receive composite resin restorations using an universal adhesive (Scotchbond Universal Plus; 3M) on dentin etched for 5 seconds in the etch-and-rinse application strategy.

Experimental group 2: 35 non-carious cervical lesions (NCCL) will receive composite resin restorations using an universal adhesive (Gluma Universal Bond; Kulzer) on dentin etched for 5 seconds in the etch-and-rinse application strategy.

Control group 1: 35 non-carious cervical lesions (NCCL) will receive composite resin restorations using an universal adhesive (Scotchbond Universal Plus; 3M) on dentin etched for 15 seconds in the etch-and-rinse application strategy.

Control group 2: 35 non-carious cervical lesions (NCCL) will receive composite resin restorations using an universal adhesive (Gluma Universal Bond; Kulzer) on dentin etched for 15 seconds in the etch-and-rinse application strategy.

LCNCs will be randomized to universal adhesive usage and dentin etching time. All groups will be light-cured with a lightcuring device (SmartLite Focus, Dentsply) with a light intensity of 900 mW/cm² for 10 seconds. Operators will restore the cervical area by applying three increments of resin (Vittra APS, FGM Prod. Odont.Ltda, Joinville, SC, Brazil). Each increment will light cure for 20 s at 900 mW/cm2 (SmartLite Focus, Dentsply). Restorations will be finished immediately with fine and extra fine diamond burs and polished with polishing gums.

Inclusion Criteria:

• Patients older than 18 years.
• Presence of at least two Non-Carious Cervical Lesions in the dental arch with a need for restorative treatment.
• Acceptable level of oral hygiene according to the Simplified Oral Hygiene Index.
• At least 20 teeth in function.
• Non-Carious Cervical Lesions with a maximum of 50% of enamel margin.

Exclusion Criteria:

• Driving difficulties that prevent adequate oral hygiene.
• Periodontal disease.
• Active caries lesions on the teeth included in the research.
• Parafunctional habits.
• Active staples of removable partial dentures on the teeth included in the research and that these are not pillars of prostheses.

Two blinded, experienced, and calibrated dentists (who specialized in esthetic dentistry with more than 15 years of clinical practice), will perform the clinical evaluation. Patients will be also blinded to group assignment. An inter-examiner and inter-examiner agreement of at least 85% will be necessary before beginning the evaluation