Micro-computed tomography assesment of structural microporosity and marginal gaps in different flowable composites placed with different instruments

Abstract

Objectives: The aim of this study was to evaluate the structural microporosity (MP) and marginal gap (MG) of different flowable composite resins placed with different instruments using micro-computed tomography (μCT). 
 Materials and Methods: Standard Class II MOD cavities were prepared on 108 lower third molar teeth. Three different flowable composite resins; Filtek Bulk-fill, SDR Bulk-fill and I-Flow conventional flowable composite resin were applied to the cavities using a sharp explorer, a microbrush or an injector. After they were covered with a paste-like nanohybrid composite resin, μCT images were examined in terms of MP and MG. Statistical analysis of the data was performed using two-way ANOVA and Tukey’s post hoc tests. 
 Results: MP was observed less in explorer group than microbrush and injector groups (p < 0.05). There was no significant difference between microbrush and injector groups (p > 0.05). i-FLOW flowable composite resin showed the highest MP rate compared to the other two groups (p < 0.05). There was no significant difference between SDR and Filtek Bulk-fill in MP (p > 0.05). In terms of MG, i-FLOW presented higher MG values than other two materials (p < 0.05), while the instruments showed similar results (p > 0.05). 
 Conclusions: Additional occluso-gingivally vibration of flowable materials with an explorer may be useful in the placement. Bulk-fill composite resins are better than conventional flowable composite resin in terms of MP and MG.

Evaluation of surface microhardness and gingival marginal adaptation of three different bulk‐fill flowable resin composites: A comparative study

“…Another recent studies, 6,11 showed similar results to our study and revealed good marginal adaptation quality of PaBF as a new material when compared with other tested FB‐RBCs before and after TMC. The results of the current study corroborates with previous research, 10 that showed that MG values for I‐Flow were greater than those of the other two materials evaluated “SDR and Filtek Bulk‐fill.”…”

“…Additionally, the filler content is reduced and the size of the filler particles is increased. These modifications make the placement of 4–5‐mm‐thick increments feasible 6,10 …”

“…These modifications make the placement of 4-5-mm-thick increments feasible. 6,10 In addition, some chemical modifications have been made in BF composites to reduce polymerization shrinkage (PS) stress, 11 such as increasing the molecular weight of the monomers in their contents, adding new stress-relieving monomers, [12][13][14][15] using of more reactive photoinitiators, and the incorporation of different types of fillers, such as prepolymer particles and fiberglass rod segments. 16 All these options are to diminish PS and minimize the negative effects of PS stress, which results in a combination of deep curing and adequate marginal adaptation.…”