Abstract
The aim of the study was to determine the marginal and internal adaptation after curing of different composite resin restorations, using a nondestructive X-ray micro-computed tomography (micro-CT). Forty previously extracted human molars, kept in 10% formalin to preserve the bonding capabilities of the tooth structures, were divided into four groups based on the composite system used and different light-curing times. Class II (vertical slot) cavities were prepared on one proximal side and restored with dental composite using a Tofflemire matrix, with a bulk-fill composite resin (Venus Bulk Fill, Heraeus Kulzer) and a universal posterior composite (G-ænial Posterior, GC). A curing lamp (Kerr Demi Ultra) was used with different curing times. Micro-CT scanning was performed by using Nikon XTH 225ST to reveal any defects in adaptation or gaps at the tooth restoration interface. The 3D images of the adaptation around the restorations were reconstructed using VG Studio Max 2.2 and myVGL 2.2.6 64-bit software. All samples from the G-ænial group showed marginal and internal gaps, with G-ænial Posterior having higher polymerization shrinkage and marginal gap values. In the Venus Bulk Fill group, there were fewer restorations with internal and external gap formation. Micro-CT is a three-dimensional imaging technique that can nondestructively detect adaptation around the resin composite restorations at every level of the sample.
Highlights
IntroductionEy pose very good mechanical properties, but polymerization shrinkage and the stress developed and accumulated during shrinkage often lead to a lack of internal adaptation and gap formation at the tooth-restoration margin
Present dental composites bearing inorganic components and an organic matrix are polymerized by quick reactions activated by, nowadays, a visible light. ese dental restorative biomaterials are in constant and fast development, and preferred over amalgam or other alloys/metals for dental restorations [1].ey pose very good mechanical properties, but polymerization shrinkage and the stress developed and accumulated during shrinkage often lead to a lack of internal adaptation and gap formation at the tooth-restoration margin. ese features possess considerable limitations of composite resin materials [2,3,4].Controlling of the polymerization shrinkage stress developed by the composite resin material is critical to establish proper marginal integrity and, the predictability and success of the restoration in the long-term
Ey pose very good mechanical properties, but polymerization shrinkage and the stress developed and accumulated during shrinkage often lead to a lack of internal adaptation and gap formation at the tooth-restoration margin. ese features possess considerable limitations of composite resin materials [2,3,4]
Summary
Ey pose very good mechanical properties, but polymerization shrinkage and the stress developed and accumulated during shrinkage often lead to a lack of internal adaptation and gap formation at the tooth-restoration margin. Controlling of the polymerization shrinkage stress developed by the composite resin material is critical to establish proper marginal integrity and, the predictability and success of the restoration in the long-term. E system reaction of dental composite light-curing develops in 3 main stages: pregel, gel point, and postgel. In the pre-gel phase, the resin can flow and go through molecular rearrangement in order to overcome shrinkage forces. During this stage, linear polymer chains are abundant and afterward, the resin goes from the flowable phase (pregel) to the viscous phase (postgel), which enacts its gel point. The resin displays a great modulus of elasticity, loses the flow capacity, and passes on the stress generated by polymerization contraction to the interface between tooth and restoration [10,11,12]
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