From pulp to cementum: 3D visualization of soft and hard dental tissues using different ex vivo nano-CT...

To determine the effect of two contrast-enhancement strategies in nano-computed tomography (nano-CT) imaging on the contrast-to-noise ratio (CNR) of various dental tissues, including pulp, dentine and cementum, with the goal of enhancing the visibility of dental soft tissues to a level not yet reported in laboratory nano-CT imaging.

Ten sound human third molars underwent decalcification and subsequent treatment with Lugol's iodine (n = 5, Group 1) or phosphotungstic acid (PTA) treatment without prior decalcification (n = 5, Group 2) for contrast enhancement. Imaging was performed using the laboratory nano-CT system Skyscan 2211 and the synchrotron radiation for medical physics (SYRMEP) beamline. CNRs were measured for pulpal tissue, dentine and cementum and nano-CT images were compared with classical histology, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDXS).

Group 1 significantly enhanced the contrast of pulp tissue, resulting in a 168.2% increase due to decalcification and an additional 148.7% increase after Lugol's iodine treatment. Dentine exhibited higher contrast in Group 2, whereas cementum showed similar contrast across both groups. Laboratory nano-CT enabled the visualization of detailed soft tissue structures, including nerves, blood vessels and odontoblasts within the pulp, but cementocytes remained invisible.

Decalcification followed by Lugol's iodine treatment was superior for enhancing soft tissue contrast, especially for pulp visualization. PTA without decalcification yielded better contrast for dentine and facilitated the visualization of attached soft tissues, such as periodontal ligament and predentine. These findings provide insights into selecting the most appropriate protocol to optimize nano-CT imaging for specific dental tissue analyses, including the pulp.