The aim of the study is to compare the performance of universal adhesives containing different-solvent-based in the restoration of non-carious cervical lesions (NCCLs).

The study was approved by the Ethics Committee of the Istanbul University Faculty of Dentistry in accordance with protocol no. 2019/37-Rev/2. All participants will be informed about the study and will sign the written informed consent prior to the first treatment.

The tested materials are the universal adhesive systems: Single Bond Universal (3M ESPE, St. Paul, MN, USA) and G-Premio Bond (GC Corporation, Tokyo, Japan). Both adhesive systems will be used in selective-etch approach. All restorations will replaced by a single experienced dentist. In this study PASS 11 Software was used to calculate the sample size. At least 230 restorations (n=115) will be included for this study.

The patients will be given local anesthesia if required to prevent discomfort during the intervention. Prior to the restorative procedure the teeth will be cleaned with a pumice water slurry, using a rubber cup. The walls of the lesions are gently and superficially roughened using a round coarse diamond bur before adhesive procedures. Isolation of the tooth will be achieved by the use of cotton rolls and a saliva aspirator, a retraction cord (Ultrapak, Ultradent Products, Inc., South Jordan, USA). Both adhesives will be applied in manufacturer' s instructions with random order, by which the first randomly selected adhesive will be used to restore the tooth with the lowest tooth number (according to the FDI system), and the alternative adhesive will be used for the tooth with the second lowest tooth number. This method will be used for every other tooth requiring a cervical restoration. After adhesive procedures, resin composite will be placed and each increment light cured for 20 seconds (Elipar S10, 3M ESPE, St.Paul, MN, USA). The restorations are then finished and polished.

Restorations will be assessed 7 days after placement (baseline) and after 6, 12, 18, and 24months. Clinical examination will be performed by two blinded examiners, who were not involved in the treatments. Each restoration will be evaluated clinically using a dental loupe according to FDI World Dental Federation criteria. Three main groups- esthetic, functional, biological properties- and their sub-categorizes of FDI World Dental Federation criteria will be scored on a scale of 1 to 5.

Esthetic properties: Surface lustre, surface staining, marginal staining, color match and translucency, esthetical anatomical form

Functional properties: Fracture of material and retention, marginal adaptation, wear, approximal anatomical form, patient's view.

Biological properties: Post-operative sensitivity, recurrence of caries, erosion, abfraction, tooth integrity, periodontal response, adjacent mucosa, oral and general health.

Statistical analysis will be performed using IBM SPSS V23 Software. The data is analyzed with Chi- Square, Friedman Test, Bonferroni Test adjustment, Wilcoxon Tests (p < 0.05).

Inclusion Criteria:

• Participant age should be 18-65 years.
• Good general health condition
• Good oral hygiene
• Should have at least 4 noncarious cervical lesion
• Must not have rampant caries
• At least 20 teeth in occlusion

Exclusion Criteria:

• Serious medical problems, allergies to product ingredients
• Poor oral hygiene
• Severe periodontal problems
• Caries or restorative treatment on teeth included in the study
• Parafunctional behavior
• Abutment of tested teeth to a removable prosthesis.