Following proper administration of local anesthesia , cavity preparation is completed according to the study's standardized dimensions. Isolation is achieved using a rubber dam to ensure a moisture-free operating field. Selective-etch is performed using 37% phosphoric acid, followed by thorough rinsing and gentle air-drying to leave the dentin moist. The bonding agent is applied according to the manufacturer's instructions, gently air-thinned to form a uniform layer, and light-cured for the specified duration. A low-viscosity flowable composite liner is applied to the pulpal floor generally not exceeding 1-2 mm in thickness. he remaining cavity depth is restored using a packable resin composite using an incremental layering technique to minimize polymerization shrinkage stress. Each increment is meticulously adapted to the cavity walls using a hand plugger, anatomically contoured, and light-cured individually from the occlusal surface.

The SonicFill bulk-fill resin composite is delivered directly into the cavity preparation using its specialized, ultrasonically activated handpiece.

The material is placed in a single bulk increment of up to 5 mm, completely filling the cavity to the occlusal margin. Once the sonic activation stops, the material reverts to a sculptable, non-slumping consistency, allowing immediate anatomical contouring. The entire bulk increment is then light-cured from the occlusal surface according to the manufacturer's recommended exposure time and intensity.

SDR bulk-fill flowable composite is dispensed directly into the cavity using the manufacturer's syringe tip, starting from the deepest part of the preparation to avoid air entrapment. Due to its self-leveling properties and low polymerization stress, it is placed in a single bulk increment of up to 4 mm, leaving approximately 1.5-2 mm of occlusal space for the capping layer. The material is then light-cured.

The remaining occlusal volume is restored using a conventional packable resin composite to act as the wear-resistant enamel replacement. Then the capping layer is adapted to the cavosurface margins, anatomically contoured to replicate correct tooth morphology, and light-cured.

The SonicFill bulk-fill resin composite is delivered directly into the cavity preparation using its specialized, ultrasonically activated handpiece. The material is placed in a single bulk increment of up to 5 mm, completely filling the cavity to the occlusal margin. Once the sonic activation stops, the material reverts to a sculptable, non-slumping consistency, allowing immediate anatomical contouring. The entire bulk increment is then light-cured from the occlusal surface according to the manufacturer's recommended exposure time and intensity

Immuno-histological analysis of the crevicular fluid to evalute pulpal inflammatory response by quantifying the volume of the pro-inflammatory cytokine TNF-α in GCF that reflect pulpal inflmmation in response to different resin composite packing techniques.

This evaluation is conducted using the Visual Analog Scale (VAS), a validated 10-cm horizontal line where "0" represents "no pain" and "10" represents "the worst imaginable pain." Participants are instructed to record their subjective perception of discomfort at specific post-operative intervals (before treatment and one week following restorative procedures ). To ensure a comprehensive assessment, pain is categorized into spontaneous pain and provoked pain (sensitivity to thermal stimuli or masticatory pressure). This subjective data is then correlated with the biochemical findings from the Gingival Crevicular Fluid (GCF) samples.