Quantification of porosity in composite resins delivered by injectable syringes using X-ray microtomography

Abstract

Objective

To assess whether composite polymer resin delivered in compules include pores and the possible effect on the amount of porosity in dental restorations.

Method and materials

Original compules containing unpolymerised composite polymer resin (CPR) were scanned in a micro-CT. Four products were examined, which comprised universal composites (Herculite XRV Ultra, Ceram.X Universal, Tetric Evo Ceram) and a flowable bulk-fill composite (SDR) (n = 10 per group). The pore size distribution and amount of porosity (vol.%) were estimated for the unpolymerized and polymerized material used to restore a standardised cavity in a typodont tooth. Manufacturers’ instructions were followed regarding material handling, and polymerisation by use of a calibrated light-curing unit. The pore characteristics and their size distribution, and the amount of porosity in the dental restoration were contrasted with the values measured in the compule. Non-parametric tests were used to analyse differences between the four products.

Results

All the composite polymer resin compules contained unpolymerised material that included pores. The universal composite compules included pores predominantly in the sub-100 µm sizes. In contrast, the flowable bulk-fill compules included a few pores with a diameter >100 µm, which were assumed to be air-bubbles. The unpolymerised material within the compule included consistently more pores compared to the extruded portion from the compule tip, and in the final restoration (p < .001). The amount of porosity in the restorations differed amongst the tested materials, with the flowable bulk-fill composite showing the lowest amount of porosity (p < .01).

Keywords:

• Composite resins
• porosity
• X-ray microtomography

Acknowledgements

The authors acknowledge Dr Lidvard Hjørungnes for his assistance during this study.

The publication charges for this article have been funded by a grant from the publication fund of UiT The Arctic University of Norway.

Disclosure statement

The authors declare that they have no conflict of interest.