The Effect of Various Placement Techniques on the Microhardness of Class II (Slot) Resin Composite Restorations

Abstract

Aim:To analyze the influence of various placement techniques on Vickers microhardness of Class II cavities restored using resin composite in different depths and layers. Methods and Materials:Sixty-four standardized Class II cavities (5.0 × 3.0 × 1.5 mm 3 ) were prepared in sound human, maxillary premolars. The cavities were divided into four experimental groups (n=16) according to the composite placement technique used: incremental technique using a Palodent matrix (IP), incremental technique using a transparent matrix (IT), centripetal technique using a Palodent matrix (CP), and the centripetal technique using a transparent matrix (CT). The cavities were restored with Single Bond, Z100 composite resin system. After 24 hours of storage in envelopes in an amber-colored box, the restorations were finished, polished, and kept for one week before conducting a hardness test. The microhardness test was carried out using a 0.5 kg load for 20 seconds at different depths and layers of proximal surfaces. Statistical analysis was done using a t-test, ANOVA, and a Tukey's test (α=0.05). Results:In contrast, the matrix bands, the methods of composite insertion, had a significant effect on hardness. The greatest surface hardness of resin composite was related to the use of the centripetal technique and a transparent matrix (p<0.05). With regard to cavity depths, the hardness at the top surface was significantly greater, followed by the middle and bottom cavity depths. A greater hardness was obtained in the mesial-distal direction within the external layer compared with the middle and internal layers using the centripetal method (p<0.05). Conclusion:The kind of matrix and filling technique could have a significant effect on surface microhardness. The top surface had the greatest hardness in comparison to different depths. In the centripetal technique, the external layer of the proximal wall had greater hardness than the other layers.Clinical Significance: While the microhardness of all of the experimental placement techniques in the different depths and layers was within a

Fracture Resistance of Premolars Restored by Various Types and Placement Techniques of Resin Composites

“…Therefore, the study concluded that the direction of layering should be adjusted in relation to the occlusion, and the way the force would be applied to the restoration [ 25 ]. Although the centripetal technique did not have a significant difference with the bulk technique in fracture resistance, there are still some advantages for this method, such as facilitation of a Class II buildup, establishment of a proper proximal contact, and provision of adequate light exposure for polymerization [ 26 ]. In this study, no significant difference was observed between the fracture resistances of specimens restored with Filtek P60 or Nulite F. According to the higher percent of volumetric filler content in Nulite F (71%) than Filtek P60 (61%), a superior fracture resistance was expected for Nulite F. The fracture toughness of BIS-GMA resin short-glass fiber composites with filler contents of 40, 50, 60, and 70% was measured in a study, and the results showed that the compressive strength was dependent on the percent of filler content, and the highest fracture resistance was obtained at the 50% filler content [ 27 ].…”

Study on the Restoration of Class II Carious Cavities by Virtual Methods: Simulation of Mechanical Behavior

“…The ability of low-viscosity materials to adapt to dentinal irregularities allows them to create an intimate bond with microstructural cavity defects prior to the placement of the paste-like restorative composite [84]. In our study, the centripetal method as the cavity-filling method was chosen, because studies have shown that fillings obtained in this way have the highest degree of microhardness [85].…”