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

Bo Wold Nilsen,Mathieu Mouhat,Asbjørn Jokstad

doi:10.1080/26415275.2020.1784013

Bo Wold Nilsen, Mathieu Mouhat + Show 1 more

Open Access

https://doi.org/10.1080/26415275.2020.1784013

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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).

Highlights

Composite polymer resin (CPR) is today the most commonly used material for direct restorations in dentistry, with more than 260 million dental restorations placed annually [1]
The least amount of porosity was seen in the restoration made from the flowable bulk-fill composite (SDR), while the dental restorations made with Herculite XRV Ultra had the largest variance of the amount of porosity in the compules (Figure 2)
We investigated if the composite resin in CPr compules included pores and if these influenced the amount of porosity in restorations

Summary

Introduction

Composite polymer resin (CPR) is today the most commonly used material for direct restorations in dentistry, with more than 260 million dental restorations placed annually [1]. The extensive use of CPR for dental restorations implies that small improvements to these materials can have vast implications concerning time and money saved for patients and clinicians. One of several strategies to improve the clinical performance of CPRs is to minimise the amount of porosity within the dental restoration [2]. Ample data from in vitro studies indicate that restoration with embedded pores may be a clinical concern. An increase in the amount of porosity in the range of 1.5–3 vol% in a CPR reduces the compressive strength and compressive fatigue limit, estimated to be in the range of 30–50% [4], and the pores may be considered as critical defects associated with fracturing of specimens [5]

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