The aim of the study is to reveal the performance of the resin composite restorations after finishing the cavity walls and margins using bioactive glass air abrasion particles in comparison to the routine finishing with the finishing diamond stone according to the FDI criteria for post operative sensitivity, marginal adaptation, marginal discoloration, secondary caries, and retention.

Intraoral air abrasion is the process of altering the surface of the tooth structure through the use of abrasive particles propelled by compressed air or other gasses. The use of intraoral air abrasion has become practical with devices that simultaneously output abrasive particles and water to control the spread of the particles. There are different types of abrasive particles maybe used depending on the clinical application for which the intraoral air abrasion is being performed. Intraoral air abrasion may also be used as a tool for dental prophylaxis, often called air polishing.

Different particles could be incorporated into air abrasion devices according to the intended use of them, such as aluminum oxide (alumina), Calcium Sodium Phosphosilicate (Biactive Glass) and Sodium bicarbonate. To obtain maximum cutting efficiency, the particle should be hard enough to indent the substrate it abrades, and irregular in shape with a sharp cutting edge. Round and smooth particles possess poor abrasive properties, so it may be used for polishing needs "air- polishing". Increased air pressure provided an increased number and velocity of the particles. Abrading power must be proportional to kinetic energy of the particles, which is the function of mass and velocity of the particle. The cutting efficiency of air abrasion depends on several criteria, such as: size, shape, hardness, density of the particles and air pressure.

Aluminum oxide (alumina) are the most abrasive type of particles used. They are irregular in shape with different particle sizes. Intraoral sandblasting with alumina particles (Al2O3) was first described in 1945 by Black. Initially, it was reported that the bond strength to the tooth surface improved, also confirmed by recent investigations, and some authors adopted its use in clinical procedures even after preparing the cavity with rotating instrument. A bioactive glass abrasive, is also commercially available but indicated for the purpose of tooth polishing. Some work has also showed potential for it to have selective cutting properties. However, its cutting time can take 2-3 times longer than alumina, making it clinically indicated for cavity finishing and not cutting.

Inclusion Criteria:

• Good oral hygiene (plaque index score 0 or 1).
• Absence of abnormal occlusion habits (e.g. bruxism, nail biting, tooth clenching and mouth breathing).
• Patients approving to participate in the study.

Exclusion Criteria:

• Patients with known allergic or adverse reaction to the tested materials.
• Systematic disease that may affect participation.
• Xerostomic patients.