Comparison of GSV of CBCT with HU of MDCT in different restorative materials

Densitometry plays an important role in diagnosis and treatment planning in today’s world. This study aimed to compare the grayscale value (GSV) of cone beam computed tomography(CBCT) with Hounsfield unit (HU) of computed tomography (CT) for five commonly used restorative materials including amalgam, composite resin, flowable composite, glass ionomer (GI), and calcium hydroxide. This study aims to solve problems related to the misdiagnosis of restorative materials and take a step forward for the simulation of these two parameters(HU, GSV) for the reconstruction of CT images from CBCT imaging data.

Seven specimens from seven different brands of amalgam, composite resin, and flowable composite (n=1 from each brand) and five specimens from five brands of GI and calcium hydroxide(n=1 from each brand) were fabricated with a 5 mm³ dimension. Cubic wooden molds measuring 5 x 5 x 5 mm were used for this purpose. The specimens underwent CBCT and MDCT under standard exposure conditions, and the GSV and HU were calculated and compared. The maximum GSV, maximum, minimum, and mean HU of amalgam were significantly higher than other materials (P<0.05). Linear regression analysis showed a significant linear correlation between the GSV and HU of restorative materials when assessing their maximum and mean values (P=0.001). CBCT and CT can help in the differentiation of amalgam from other restorative materials. Also, the HU can be calculated according to the mean or maximum GSV of a material.