This study is conducted in order to evaluate the clinical effectiveness of 1% DMSO dentin pre-treatment on the clinical performance of etch and rinse adhesive.

Despite substantial advances in resin-dentin bonding over the past decades, reduction in bonding effectiveness of currently available dental adhesives remains a major limitation in modern adhesive dentistry. Hydrolysis of both organic and resin constituents of hybrid layer persists as impediments in dentin bonding longevity. Since bonding is directly related to the quality of the formed polymer the resin components play an important role in proper resin-dentin interaction and in the mechanical properties of the material.

In face of the limitations of most current clinically-feasible bonding protocols and inherent drawbacks of the etch-and-rinse approach an ideal resin-enveloped collagen scaffold is unlikely to be produced in a consistent manner. In dentin hybridization, adhesive infiltration is far from perfect resulting in poorly formed hybrid layers. Replacement of all 70 vol% residual water in etched-dentin with monomers is hardly achieved. For this reason, the hybrid layer may be considered as the weak link in resin-dentin bonds.

DMSO [(CH3)2SO] is a polar aprotic solvent that dissolves both polar and non-polar compounds. It is a polyfunctional molecule, with a highly polar S O group and two hydrophobic methyl groups, fully miscible in most solvents and monomers used in adhesive dentistry. DMSO is perhaps the best currently known penetration enhancer for medical purposes with the ability to dissociate the highly crosslinked collagen into a sparser network of apparent fibrils.

The rationale for testing a bonding resin with relatively low DMSO-content is that incorporation of high DMSO concentrations may hamper the mechanical properties of dimethacrylate bonding polymers, which in turn could compromise the bonded interface. DMSO's ability to "biomodify" collagen structure, increasing spaces between collagen microfibrils and improving dentin wettability support the improved bonding effectiveness even under dry-conditions. It is evident that this simplified use of DMSO or, to a better extent, its use as a dentin pretreatment reduced technique sensitivity of the etch-and-rinse approach concomitantly allowing water removal from the bonded interface by the proposed dry-bonding technique. Optimized bonding efficiency combined with reduced water-content during dentin hybridization could greatly contribute to clinical long-term durability.

Nevertheless, further studies are necessary to test such hypothesis. Specially that there is no clinical study support this theory yet even DMSO had taken the FDA approval many years ago as a pharmaceutical solvent and has been used in several medications. DMSO caused no or minor cytotoxic effects on the pulp tissue repair-related activity of odontoblast-like cells.

Inclusion Criteria:

• Patients with cervical lesions.
• Co-operative patients approving to participate in the study.
• Pulp is asymptomatic vital teeth.
• Presence of favorable occlusion and teeth are in normal contact with the adjacent teeth.

Exclusion Criteria:

• Xerostomia.
• Bruxism and visible wear facets in the posterior dentition.
• Known inability to return for recall appointments.
• Fractured or visibly cracked candidate tooth.
• Current desensitizing therapy, including desensitizing dentifrices or other over-the-counter (OTC) products.
• Long-term use of anti-inflammatory, analgesic, or psychotropic drugs.
• Pregnancy or breastfeeding (potential conflicts with recall dates.
• Allergies to ingredients of resin-based restorative materials.
• Orthodontic appliance treatment within the previous three months.
• Abutment teeth for fixed or removable prostheses.
• Teeth or supporting structures with any symptomatic pathology.
• Existing periodontal disease or periodontal surgery within the previous three months.

In our clinical trial double blinding will be performed, the participants and both assessors (H.M.& N.H.) will be blinded to the type of the material used to reduce performance and ascertainment bias and also reduce biased estimates of treatment effects. The operator cannot be blinded in this trial because of the difference in the application procedures of each restorative material. Therefore, the operator (O.I.) will take care to treat the two allocation groups as equally as possible by standardizing the care of participants, frequency of follow-ups and management of complications.