Novel Dye Characterization for Dental Fracture Analysis

This preliminary study included 26 single-rooted, freshly extracted, virgin premolars obtained from the orthodontic clinic at College of Dentistry, Prince Sattam bin Abdulaziz University (PSAU). Two teeth were used as negative controls, and the remaining 24 teeth were used as the experimental group. Prior to initiating the study, ethical approval was attained (PSAU2020027) from the Institutional Review Board (IRB) at Prince Sattam bin Abdulaziz University. The selected teeth were inspected under an operating microscope (Zumax, Suzhou, China) for signs of fractures, cracks, or severe curvatures, and such teeth were excluded. To disinfect the teeth, they were immersed in 2.5% sodium hypochlorite (Sun Chemical, Riyadh, Saudi Arabia) overnight. The roots were covered with pink wax (Dentsply Sirona, Charlotte, NC, USA) and mounted in a mixture of gypsum and wood powder to closely mimic the density of the jaw bone seen in radiographs.
To induce the fracture lines, the teeth were decoronated; a brass pin was placed in the canal, and using an Instron machine (Zwick/Roell, GmbH & Co, KG, Dettingen unter Teck, Germany), force was slowly applied until a visible/audible crack was achieved. The blocks were then placed on previously customed alginate seats and mounted on a radiograph ring to ensure reproducibility of the radiograph angle.
Methylene blue dye (Rupal Colorchem Industries, Ahmedabad, India) was used for control teeth. Fillers were added to methylene blue dye to prepare a novel dye, which was used for teeth in the experimental group. The powdered fillers within it were unified and ground using a planetary ball mill (Fritsch Pulverisette 7; Fritsch GmbH, Idar-Oberstein, Germany) for one hour at 400 rpm using zirconia balls. The average particle sizes before and after milling were measured using Zetasizer (Malvern Panalytical Ltd., Malvern, UK).
The dyes were then placed around the circumference of the roots using a micro brush. Gentle air was blown using a three-way air syringe with the intention to force it in the crack/fracture lines. The blocks were placed on alginate seats and radiographed in straight view and tube-shift view using a Carestream CS5200 (Carestream Dent LLC, Atlanta, GA, USA) digital sensor. The CBCT images of samples were attained using a Carestream CS9300 (Carestream Dent LLC, Atlanta, GA, USA) machine with voxel sizes of 180–300 mm. The digital radiographs and CBCT images of all the 26 teeth (Figure 1) were analyzed and evaluated on a five-point Likert scale, as seen in Table 1, by three blinded dentists: two experienced endodontists and a maxillo-facial radiologist. The constructive validation of the questionnaire was performed by independent members of the IRB after going through the results of an initial pilot study performed by the authors. Based on the recommendations of the expert committee, the questionnaire was modified to evaluate the dye penetration apically along the length of the root as well as laterally towards the pulp in thirds.