Restoring posterior teeth with extensive proximal lesions requires a precise combination of adhesive protocols, anatomical reproduction, and mechanical reinforcement. This case report describes a Class II direct composite restoration using fiber-reinforced dentin replacement, sandblasting for enhanced adhesion, a dual-flowable approach for adaptation, and the Functional Matrix Technique (FMT) for anatomical accuracy.
Case Presentation
A patient presented with secondary caries under a defective restoration in the maxillary second premolar. The decay extended subgingivally, requiring deep margin management. Rubber dam isolation was applied to ensure a moisture-free environment and protect adjacent tissues during preparation.
Clinical Procedure
Step 1 – Isolation and Cavity Preparation
- Rubber dam isolation was achieved using a clamp and heavy dam sheet.
- All caries and defective restoration material were removed conservatively.
- Sandblasting was performed with 30 μm aluminum oxide particles to increase micromechanical retention at the dentin and enamel surfaces (Fig. 1).
Step 2 – Matrix System Placement
- A sectional matrix band (Ultradent) was adapted using a Rinn ring and wooden wedges to ensure tight proximal seal and contour (Fig. 2).
Step 3 – Adhesive Protocol
- Selective enamel etching for 15 seconds.
- Application of a universal bonding system (Dentsply), air-thinned to avoid pooling, followed by light-curing.
Step 4 – Fiber-Reinforced Base Layer
- A fiber-reinforced composite (EverX) was placed as a dentin replacement, covering pulpal and axial walls to enhance fracture resistance.
Step 5 – Flowable Composite Adaptation
- A Nano Flowable Composite (3M) was applied as a thin liner over the fiber-reinforced layer for intimate adaptation to irregularities.
- In deep areas, a Bulk Flow Composite (Shofu) was used to fill the base, reducing polymerization stress.
Step 6 – Functional Matrix Technique (FMT)
- The occlusal anatomy was pre-modeled on the matrix side before final curing, ensuring precise cusp-fossa reproduction and minimal occlusal adjustment.
Step 7 – Incremental Layering with Nanofilled Composite
- A nanofilled universal composite (3M) was placed incrementally, each cusp sculpted separately and light-cured for 20 seconds.
Step 8 – Finishing and Polishing
- Occlusion was checked in static and dynamic movements.
- Final polishing was achieved with a multi-step polishing kit, restoring enamel gloss and smooth margins.
Outcome
The restoration achieved excellent proximal contact, anatomical accuracy, and high surface gloss. The combination of sandblasting, dual-flowable adaptation, fiber reinforcement, and FMT provided optimal biomechanics and esthetics.
Discussion
- Sandblasting (30 μm) effectively increases surface energy and creates micro-retentive patterns, improving adhesive bonding.
- Dual-flowable technique (Nano Flowable + Bulk Flow) enhances adaptation, reduces voids, and helps stress distribution.
- Fiber-reinforced composites like EverX act as an internal splint, increasing fracture toughness.
- FMT minimizes occlusal adjustments and preserves original occlusal morphology.
Conclusion
A protocol combining sandblasting, modern adhesive systems, fiber-reinforced dentin replacement, dual-flowable composites, and FMT can produce predictable, durable, and esthetic Class II restorations.
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