Assessing the quality of restoration using Smart Dentin Replacement+ and Tetric N Ceram done in Class I pits and fissure caries using Bulk fill and Incremental Technique-An In vivo Study

Resin-based composite (RBC) stands as the predominant choice for contemporary dental restorations, prized for its superior esthetic qualities and simple application. Nevertheless, it harbors potential complications stemming from inadequate polymerization and the accompanying issue of polymerization shrinkage5. This issue has been addressed through various methods, such as utilizing larger monomers to reduce the quantity of double bonds available for reaction, incorporating inorganic fillers that remain inert during polymerization, minimizing volume shrinkage by adjusting the chemistry or composition of the resin system, and implementing clinical techniques aimed at mitigating the impacts of polymerization shrinkage5.   Achieving sufficient polymerization in composite resin placement requires three crucial characteristics in the light-curing unit: Sufficient light output, the appropriate wavelength range, and the correct exposure time. Other factors influencing the depth of cure include the resin composite (RC) type, its shade and translucency, the thickness of each increment, the distance from the light-curing unit tip, the post-irradiation period, and the size and distribution of filler particles2.     Various methods exist for placing composite resins in cavities. Some researchers advocate for an incremental technique, where the material is applied gradually in layers of 2 mm or less. This method offers several advantages, such as improved light penetration and resin polymerization, reduced cavity configuration factor, diminished cuspal deflection, lower polymerization shrinkage stresses, and enhanced resin adhesion to cavity walls. However, alongside these benefits, there are drawbacks to the incremental approach, including the potential for voids between increments, bonding failures, difficulty in placing material after conservative cavity preparation, and increased procedure time due to the need to place and polymerize each increment. In an attempt to address many of these limitations, several new restorative materials marketed as "bulk-fill" composites have emerged 2.   Recent studies indicate that polymerization stress is significantly reduced (3-4 times lower) when using a 4-mm layer of SDR during polymerization. SDR technology relies on a unique chemical composition in its organic phase, incorporating a polymerization modulator. One of its components, urethane Di methacrylate resin, acts as a monomer controlling the polymerization process, initiating a chemical "soft start." This leads to the formation of a polymerization network in a more linear and gradual manner, effectively limiting shrinkage stress. Additionally, SDR exhibits comparable physical properties to traditional composites, including susceptibility, surface texture, gloss, and color. This similarity makes it particularly advantageous for restoring defects on hard tissue contact surfaces. The foundational material represents a significant advancement in conservative dentistry.   The objective of this study was to evaluate, through randomized double blinded comparison, the clinical effectiveness of using flowable resin composite applied in bulk increments of up to 4mm in large and deep pits and fissure cavities. The cavities were filled using SDR, extending 2mm short of the occlusal Cavo surface, and then covered with a nano-hybrid resin composite. The SDR restoration was compared within the same individual to a restoration using only nano-hybrid resin composite, applied and cured using a 2mm layering technique and after that evaluation using dye impregnation method with DOM (Dental Operating Microscope) under 6X magnification for sensitivity and secondary caries with bite wing radiographs within baseline,6month and 12 month follow up. Both the experimental bulk-fill technique and the resin composite-only control were bonded using a one-step self-etching bonding system. The hypothesis under examination was whether bulk-fill restorations would exhibit comparable durability with Incremental fill one of the similar restorations.