Purpose: Physiological dentin sclerosis is a distinctive phenomenon observed in transverse sections of the tooth root as a tooth ages. Since this effect has only been visualized 2-dimensionally, this pilot proof-of-concept study aimed to propose a novel method to visualize and quantify physiological sclerotic dentin 3-dimensionally using density-based micro-computed tomography (CT)-generated gray values. Materials and Methods: Forty single-rooted premolars of known chronological age from the Malay male population were scanned with a micro-CT scanner. The X-ray source was operated at 160 kV, 100 μA, and a voxel size of 48.8 μm.Three-dimensional volume datasets for each tooth were reconstructed, and volumetric analysis was performed on the root dentin region using the open-source software FIJI (ImageJ) (ver. 1.54k, National Institutes of Health, Bethesda, USA). Results: Micro-CT imaging enabled the selection, isolation, and quantification of high-density areas in the tooth rootthat correspond to physiological sclerotic dentin. The generated gray value profile also reflected the characteristicbutterfly-shaped pattern seen in transverse root sections. A comparison of premolars from different age groups revealedthat individuals aged 31-60 years exhibited a larger butterfly-shaped area, reflecting the increase in high-density sclerotic dentin, compared with younger premolars. Conclusion In this pilot proof-of-concept study, visualization and measurement of physiological sclerotic dentin were shown to be feasible using micro-CT. However, the method is highly dependent on the capability of the micro-CT scanner and the performance of the image-processing software. Further research is needed to improve image quality using advanced micro-CT scanning techniques.

This study aimed to investigate the irrigation dynamics of the positive pressure side-vented (SV) needle, EndoVac (micropores) needle and modified apical negative pressure (mANP) open-ended needle using computational fluid dynamics (CFD). A simulation of a prepared root canal (conical frustum) of 15 mm length with an apical diameter of 0.40 mm following Protaper F4 apical preparation was created using three-dimensional (3D) CAD software. The 3D simulated needle of SV 30G needle, EndoVac with micropores needle and mANP, 30G flat open-ended needle were also created. The irrigation dynamics were evaluated through transient CFD simulations. In addition, the irrigation dynamics of mANP at 0.2 mm, 0.5 mm, and 1.0 mm short from the working length were also assessed. The EndoVac and mANP showed negative apical static pressure and streamline patterns able to reach the apical region, thus indicating negligible extrusion. Meanwhile, SV showed positive apical static pressure and almost nonexistent streamlines beyond the needle tip. The SV showed the highest wall shear stress (WSS) magnitude of 1030Pa whereas Endovac (161 Pa) and mANP1 (258 Pa). However, SV revealed lower average WSS (10 Pa) compared to mANP1 (13 Pa) and mANP2 (11 Pa). This is due to SV developed a localised maximum WSS opposite the open vent area only therefore, uneven distribution of WSS. The EndoVac system developed a localised maximum WSS in the pair of micropores furthest away from the apical. CFD analysis of the EndoVac, mANP and SV showed different technique approach, needle design and needle depths insertion affect the irrigation dynamics pattern and magnitude.