Abstract
Gap formation of composite resin restorations is a serious shortcoming in clinical practice. Polymerization shrinkage stress exceeds the tooth-restoration bond strength, and it causes bacterial infiltration within gaps between cavity walls and the restorative material. Thus, an intermediate liner application with a low elastic modulus has been advised to minimize polymerization shrinkage as well as gap formation.Objective:The purpose of this in vitro study was to assess gap formation volume in premolars restored with different bulk-fill composites, with and without a resin-modified glass-ionomer cement (RMGIC) liner, using x-ray micro-computed tomography (micro-CT).Methodology:Sixty extracted human maxillary premolars were divided into six groups according to bucco-palatal dimensions (n=10). Standardized Class II mesio-occluso-distal cavities were prepared. G-Premio Bond (GC Corp., Japan) was applied in the selective-etch mode. Teeth were restored with high-viscosity (Filtek Bulk Fill, 3M ESPE, USA)-FB, sonic-activated (SonicFill 2, Kerr, USA)-SF and low viscosity (Estelite Bulk Fill Flow, Tokuyama, Japan)-EB bulk-fill composites, with and without a liner (Ionoseal, Voco GmbH, Germany)-L. The specimens were subjected to 10,000 thermocycles (5-55°C) and 50,000 simulated chewing cycles (100 N). Gap formation based on the volume of black spaces at the tooth-restoration interface was quantified in mm3 using micro-computed tomography (SkyScan, Belgium), and analyses were performed. Data were analyzed using repeated-measures ANOVA and the Bonferroni correction test (p < 0.05).Results:The gap volume of all tested bulk-fill composites demonstrated that Group SF (1.581±0.773) had significantly higher values than Group EB (0.717±0.679). Regarding the use of a liner, a significant reduction in gap formation volume was observed only in Group SFL (0.927±0.630) compared with Group SF (1.581±0.773).Conclusion:It can be concluded that different types of bulk-fill composite resins affected gap formation volume. Low-viscosity bulk-fill composites exhibited better adaptation to cavity walls and less gap formation than did sonic-activated bulk-fill composites. The use of an RMGIC liner produced a significant reduction in gap formation volume for sonic-activated bulk-fill composites.
Highlights
Increasing demand for esthetics and improvements in adhesive system technology has made resin composite restorations a popular choice for clinicians.1 shrinkage associated with the polymerization of materials is a serious shortcoming in clinical practice.2 Polymerization shrinkage stress exceeds the tooth-restoration bond strength, and it causes fluid passage and bacterial infiltration within gaps between cavity walls and the restorative material.3 Microleakage, which is described as clinically undetectable penetration, could lead to post-operative hypersensitivity, marginal staining, secondary caries, pulpal inflammation and necrosis.4Several procedures have been developed to decrease polymerization shrinkage stress, such as modifying the chemical composition in the resin formulation, control of light irradiance, incremental layering techniques and intermediate liner application.5 no definitive method to eliminate polymerization shrinkage has been described in the literature
An intermediate liner application with a low elastic modulus has been advised to minimize polymerization shrinkage as well as gap formation. The purpose of this in vitro study was to assess gap formation volume in premolars restored with different bulk-fill composites, with and without a resin-modified glass-ionomer cement (RMGIC) liner, using x-ray micro-computed tomography
An analysis of the gap formation between bulk-fill composites and/or the RMGIC liner and cavity walls was performed for all tested groups (n=10)
Summary
Increasing demand for esthetics and improvements in adhesive system technology has made resin composite restorations a popular choice for clinicians. shrinkage associated with the polymerization of materials is a serious shortcoming in clinical practice. Polymerization shrinkage stress exceeds the tooth-restoration bond strength, and it causes fluid passage and bacterial infiltration within gaps between cavity walls and the restorative material. Microleakage, which is described as clinically undetectable penetration, could lead to post-operative hypersensitivity, marginal staining, secondary caries, pulpal inflammation and necrosis.4Several procedures have been developed to decrease polymerization shrinkage stress, such as modifying the chemical composition in the resin formulation, control of light irradiance, incremental layering techniques and intermediate liner application. no definitive method to eliminate polymerization shrinkage has been described in the literature.. Increasing demand for esthetics and improvements in adhesive system technology has made resin composite restorations a popular choice for clinicians.. Shrinkage associated with the polymerization of materials is a serious shortcoming in clinical practice.. Polymerization shrinkage stress exceeds the tooth-restoration bond strength, and it causes fluid passage and bacterial infiltration within gaps between cavity walls and the restorative material.. Microleakage, which is described as clinically undetectable penetration, could lead to post-operative hypersensitivity, marginal staining, secondary caries, pulpal inflammation and necrosis.. Several procedures have been developed to decrease polymerization shrinkage stress, such as modifying the chemical composition in the resin formulation, control of light irradiance, incremental layering techniques and intermediate liner application.. No definitive method to eliminate polymerization shrinkage has been described in the literature.
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