Cuspal Deflection and Temperature Rise of MOD Cavities Restored through the Bulk-Fill and Incremental Layering Techniques Using Flowable and Packable Bulk-Fill Composites

Abstract

Background: The aim of this study was to investigate cuspal deflection caused by material shrinkage and temperature rise occurring in the pulp chamber during photopolymerization. The aim of this study was also to investigate the effect of flowable and packable bulk-fill composites on cuspal deflection occurring in mesio-occlusal–distal (MOD) cavities restored through the bulk-fill or through the incremental layering technique. Additionally, mechanical and thermal properties of bulk-fill composites were considered. Methods: Two bulk-fill composites (high-viscosity and low-viscosity), largely differing in material composition, were used. These composites were characterized through linear shrinkage and compressive test. Cuspal deformation during restoration of mesio-occlusal–distal cavities of human premolars was evaluated using both the bulk-fill and the incremental layering techniques. Temperature rise was measured through thermocouples placed 1 mm below the cavity floor. Results: Shrinkage of the flowable composite was significantly higher (p < 0.05) than that of packable composite, while mechanical properties were significantly lower (p < 0.05). For cusp distance variation, no significant difference was observed in cavities restored through both restorative techniques, while temperature rise values spanned from 8.2 °C to 11.9 °C. Conclusions: No significant difference in cusp deflection between the two composites was observed according to both the restorative techniques. This result can be ascribed to the Young’s modulus suggesting that the packable composite is stiffer, while the flowable composite is more compliant, thus balancing the cusp distance variation. The light curing modality of 1000 mW/cm2 for 20 s can be considered thermally safe for the pulp chamber.

Fracture Strength and Failure Modes of Endodontically Treated Premolars Restored with Compact and Hollow Composite Posts Subjected to Cyclic Fatigue

“…The thickness of the bucco-lingual cavity was 3 mm measured with a digital caliper (Mitutoyo, Takatsuku, Kawasaki, Japan). Teeth were then subjected to an adhesive procedure by acid etching of enamel and dentin for 30 s and 15 s, respectively, using 37% phosphoric acid (Gerhò, Bolzano, Italy) and subsequentially 5 s of rinsing and drying; finally, the application of the Optibond SE (Kerr Corporation) adhesive system and photo-curing with the Swiss Master Light (EMS) curing unit at an intensity of 1000 mW/cm 2 [ 22 ] SonicFill was directly dispensed into dental cavities using the Sonicfill (Kerr Corporation) handpiece.…”

Cuspal Deflection and Marginal Gap of Class II MOD Using Preheating Bulk-Fill Composite with Different Application Techniques

“…After cavity preparation, teeth were subjected to an adhesive procedure: acid etching (enamel and dentine etching for 30 s and 15 s, respectively) using 37% phosphoric acid (Super etch, SDI, Australia), rinsing and drying for 5 s with an absorbent. After that, a drop of adper 3M adhesive system (Adper adhesive system, 3M ESPE Filtek, St. Paul, MN USA) was applied, and gentle air thinned the bond layer, then photopolymerized for 10 seconds by light cure (radii plus, SDI, Australia) with an intensity of 2100 mW/cm2that was checked by a radiometer (SDI, Australia) for each restoration (6,16).…”

“…The cuspal deflection of restored teeth is one of the clinical implications of polymerization shrinkage stresses produced by the composite resin restorations (6,23). Numerous factors can affect the cuspal deflection of a tooth, such as the type of tooth, cavity design and amount of remaining tooth structure (6,24), curing mode (25), and the type of resin composite material (6,10). The current study showed an inward cuspal deflection for all subgroups.…”

“…However, Abdul Majeed et al (2020) (5) stated that the effects of preheating on composite properties and clinical performance are not fully confirmed and still need to be investigated. From a clinical point of view, the accurate method to evaluate the polymerization shrinkage stresses effect is by measuring the cuspal deflection of the tooth after restoration (6). The cuspal deflection is defined as the deformation of cavity walls of teeth.…”

Mechanical and Biomimetic Characteristics of Bulk-Fill Resin Dental Composites Following Exposure in a Simulated Acidic Oral Environment

“…Moreover, manufacturers have also highlighted that this class of materials exhibits lower polymerization shrinkage compared to flowable and conventional RBC counterparts [ 6 ]. Consequently, complications associated with polymerization shrinkages [ 7 ] such as secondary caries [ 8 , 9 ], postoperative sensitivity, pulpal irritation [ 10 ], or cusp deflections [ 11 , 12 ] are likely to be reduced.…”