The use of a liner under different bulk-fill resin composites: 3D GAP formation analysis by x-ray microcomputed tomography

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.

Effect of Ultrasonic Scaling on Microleakage of Class V Composite Restorations Bonded With Different Adhesives

“…In addition, the unique flexible nature of the material allows for expansion and contraction of the resin restorative without opening the cavo-surface margins. 10,24,25 Current study results came in agreement with El Sayed et al 16 who compared "self-etch" to "etch and rinse" systems, as they concluded that "etch and rinse"adhesive deserved its position as the gold standard bonding agent, as it showed less microleakage. On the contrary, Gupta et al 26 , evaluated microleakage with different systems, and they came to the conclusion that one step self-etch adhesives revealed less microleakage than total etch ones.…”

Microleakage of Direct Restorations-Comparisonbetween Bulk-Fill and Traditional Composite Resins:Systematic Review and Meta-Analysis

“…1 This could result from polymerization shrinkage stress of the composite resins; the stress overcomes the bond strength of restoration causing the passage of fluids and bacterial infiltration between walls of the cavity and filling material. 2 The presence or absence of microleakage is one of the outcomes accountable for the success of fillings overtime 3 ; oral microorganisms invade the tooth-restoration gap in a short time and they can reach dental tissues causing a biological damage. 4 The microleakage could result in discoloration 5 of the margins of restoration, dentin hypersensitivity, secondary caries, and also pulp affections.…”

“…11 Although bulk-fill composite resins are claimed to exhibit low polymerization shrinkage, there are not enough evidences concerning the effects of gap formation of these composites using an intermediate liner. 2 This systematic review with meta-analysis aimed: • To evaluate the difference of microleakage between dental restorations performed with bulk-fill and conventional composites resins. • To assess the entity of marginal discoloration, marginal adaptation, and secondary caries of restorations made by the two different composites resins.…”

The cuspal deflection caused by dental composite polymerization shrinkage analyzed by digital holography

“…However, the marginal adaption of RDMs in class I and class II cavities reflects complex interactions between adhesive bonding on one hand 25 , and PSS at the tooth-restoration interface on the other 32 . The level of PSS and debonding are more probably dependent upon the shape and hence constraints of the cavity 8,9,33,34 , as well as viscoelastic properties of RDMs 35,36 , than other factors. It is well-known that cavity configuration (C-factor) is one of the main factors affecting the development of PSS 8,9,33,37 , since greater confinement imposed on the RDM leaves a smaller number of free surfaces for resin composite shrinkage and PSS relaxation.…”