Marginal Adaptation of Flowable vs Sonically Activated or Preheated Resin Composites in Cervical Lesions

Abstract

Purpose: To investigate marginal integrity of restorations applied with preheated and non-preheated composite, flowable composite, sonically activated composite, and a new thermo-viscous bulk-fill composite using near-infrared technology for preheating, in class V cavities of human molars.

Materials and methods: Standardized cavities were prepared on the buccal surfaces of 60 human mandibular molars and restored with one of the following resin composite materials after application of an etch-and-rinse adhesive (OptiBond FL, Kerr): non-preheated or preheated conventional composite (Filtek Supreme XTE, 3M Oral Care), preheated thermo-viscous composite (VisCalor bulk, Voco), soncially activated composite (SonicFill 3, Kerr), or flowable composite (Filtek Supreme XTE Flowable, 3M Oral Care) applied in bulk or as a lining material using the snow-plow technique. After light curing and polishing, the percentage of continuous margins (PCM) of the restorations in enamel and dentin was assessed using SEM both before and after thermomechanical loading (TML). TML was carried out with 3000 thermal cycles (5°C-50°C) and a simultaneous mechanical stress application with 1.2 million load-cycles (1.7 Hz, 49 N) in a computer-controlled masticator. Non-parametric statistical analysis was performed using Wilcoxon, Kruskal-Wallis, and Mann-Whitney U-tests (α = 0.05).

Results: All groups revealed a significant decline in marginal integrity after TML in both enamel and dentin. Although the flowable group in enamel and the snow-plow group in dentin showed the highest PCM before TML, the differences between the groups were compensated after TML.

Conclusion: All of the tested composites and application methods showed similar marginal integrities after thermomechanical loading and can be recommended for clinical implementation.

Keywords: flowable composite; marginal adaptation; preheating; resin composite; sonic activation.

Fig 1

Experimental design.

Fig 2

Representative scanning electron micrograph of a class V restoration before and after thermomechanical loading, showing continuous margins (green), discontinuous margins (red), and non-assessable margins (yellow). A magnified detail (black rectangle) shows a perfectly continuous margin before thermomechanical loading, upon which a local discontinuity was observed after thermomechanical loading.

Fig 3

Scanning electron micrographs of restoration margins in enamel before and after thermomechanical loading (TML).

Fig 4

Scanning electron micrographs of restoration margins in dentin before and after thermomechanical loading (TML).

Fig 5

Percentages of continuous enamel margins before and after thermomechanical loading (TML). Same lowercase letters indicate statistically homogeneous groups before TML. Same uppercase letters indicate statistically homogeneous groups after TML. All pairwise comparisons of values obtained before and after TML were statistically significant. The boxplots show the medians (bold black lines), the boxes represent the 25% and 75% data quartiles, whereas the whiskers represent 1.5 x interquartile range (IQR), or minima and maxima of the distribution if below 1.5 x IQR; outliers are represented by circles and extreme outliers by asterisks.

Fig 6

Percentages of continuous dentin margins before and after thermomechanical loading (TML). Same lowercase letters indicate statistically homogeneous groups before TML. Same uppercase letters indicate statistically homogeneous groups after TML. All pairwise comparisons of values obtained before and after TML were statistically significant. Circles (°) above the letters indicate statistically significant differences between enamel and dentin. The boxplots show the medians (bold black lines) and the boxes represent the 25% and 75% data quartiles, whereas the whiskers represent 1.5 x interquartile range (IQR), or minima and maxima of the distribution if below 1.5 x IQR; extreme outliers are presented by asterisks.