Effect of adhesion to cavity walls on the mechanical properties of resin composites

Placing Dental Composites—A Stressful Experience

“…54,68,[73][74][75][76] The physical properties, such as elastic modulus and strength, also have been shown to be reduced for composites cured in cavities with greater external constraint, 74,77 though another study did not show this difference. 75 While these results may be directly attributable to the generation of contraction stresses in dental composite restorations, and they provide a rationale for closely following a structured placement technique to minimize their effects, no direct clinical evidence currently exists to support a cause and effect relationship between contraction stress and clinical failure or longevity for these materials.…”

Bond strength and ultimate tensile strength of resin composite filled into dentine cavity; effect of bulk and incremental filling technique

“…11-13 Nayif et al 12 speculated that not all the polymer network was rearranged and its formation was partly interrupted during polymerization due to the presence of internal stresses caused by a restriction of polymerization shrinkage, resulting in lower UTS. In this study, the UTS value of resin composite (Clearfil AP-X) at the upper region within bonded dentine cavities was approximately 90 MPa even when using the incremental technique.…”

“…Recent studies have demonstrated that the mechanical properties of resin composites were significantly reduced under constrained conditions. [11][12][13] However, there is limited information on the relationship between bonding to cavity walls and the mechanical properties of resin composites. Many questions still remain on how stresses compromise the interface and/or the internal cohesion of the resin restoration.…”

“…The development of the micro-tensile test has permitted the evaluation of regional bond strength (mTBS) to small areas in complex cavities within tooth substrates 3,5,14 and also measurement of the regional ultimate tensile strength (UTS) of resin composite. 12,15 The purpose of this study was to evaluate the relationship between mTBS and UTS of resin composite restorations filled with a bulk or incremental technique using the micro-tensile test. We hypothesized that there is no relationship between bond strength (mTBS) to cavity walls and ultimate micro-tensile strength (UTS) of resin composites within cavities prepared into dentine.…”

Polymerization stress – Is it clinically meaningful?

“…Flexure strength and modulus has been shown to be reduced under these conditions in specimens that were cut from a construct that provided strong adhesion to the walls to ensure high contraction stress conditions [63,73,74]. It is not known whether the reduced strength and stiffness of the material resulting from the residual stresses remaining in the composite after curing produces clinically relevant outcomes.…”