## 1 Introduction  
Dental restorations are a fundamental aspect of modern dentistry, playing a crucial role in restoring the functionality and esthetics of patients' teeth. The success of these restorations depends on various factors, one of the most important being the surface characteristics of the materials used [1]. Surface roughness, in particular, is a critical parameter that can significantly influence the longevity and performance of dental restorations. A rough surface not only increases the potential for plaque accumulation and bacterial colonization but also affects the wear resistance of the material and the adjacent dentition [2]. Therefore, understanding and controlling the surface roughness of restorative materials is essential for achieving optimal clinical outcomes. Two commonly used restorative materials in pediatric dentistry are composite resins and glass ionomer cements, such as Fuji. Composite resins are favored for their excellent esthetic properties and strong bonding capabilities, making them suitable for a wide range of dental applications [3]. On the other hand, glass ionomer cements are valued for their ability to release fluoride and their biocompatibility, making them particularly useful in cases where fluoride release is beneficial, such as in pediatric dentistry and in patients with a high risk of caries [4]. Despite their widespread use, these materials can exhibit varying degrees of surface roughness depending on the clinical procedures and materials used during their placement and finishing [5]. The polishing and finishing of dental restorations are crucial steps that can significantly influence the final surface roughness of the material [6]. Traditionally, polishing has been performed using rotary instruments and polishing pastes, but the advent of air-polishing systems has introduced new possibilities. Air polishing involves the use of abrasive powders propelled by compressed air, which can efficiently remove plaque and stains from the surface of teeth and restorations. Commonly used powders in air polishing include sodium bicarbonate, erythroid, and glycine, each of which has distinct physical and chemical properties that influence their abrasiveness and effect on dental surfaces [7; 8]. Sodium bicarbonate, one of the earliest powders used in air polishing, is known for its effectiveness in plaque removal. However, its relatively high abrasiveness can lead to increased surface roughness, which may compromise the integrity of the restoration [9]. Erythriitol, a sugar alcohol, has gained popularity due to its lower abrasiveness compared with bicarbonate, making it gentler on the tooth surface while still effectively removing biofilm [7]. Glycine, an amino acid, is the least abrasive of the three and is often recommended for use on sensitive surfaces and subgingival applications [8]. The impact of these abrasive powders on different dental materials has been the subject of several studies. For instance, research has shown that the use of bicarbonate can lead to a significant increase in surface roughness, particularly in composite resins, which could potentially affect the material's wear resistance and susceptibility to bacterial adhesion [9]. In contrast, glycine has been reported to produce a smoother surface, which may be advantageous in minimizing bacterial colonization and prolonging the restoration's lifespan [10]. However, the extent of these effects can vary depending on factors such as exposure time and the specific type of restorative material being treated [11]. Despite these insights, there remains a lack of comprehensive studies that systematically compare the effects of different air-polishing powders on both composite resins and glass ionomer cements under controlled conditions [12]. Most existing studies focus on a single material or powder, leaving clinicians with limited information when it comes to selecting the most appropriate polishing agent for different clinical scenarios [13].