Análise dos tons de cinza dos filmes autorreveláveis em diferentes momentos de processamento químico após exposição aos raios X

Abstract

Dental radiography is an essential tool for diagnosis, monitoring, and clinical treatment planning, and its diagnostic quality is directly influenced by the stability and fidelity of the grayscale tones that compose the final image. Self-developing films represent a practical alternative to conventional processing because they eliminate the need for a darkroom and separate chemical solutions; however, it remains unclear whether the interval between X-ray exposure and monobath activation can affect the grayscale values produced. Considering that subtle variations in intermediate tones may compromise the differentiation of anatomical structures and early incipient lesions, understanding this relationship becomes fundamental. This study aimed to analyze the influence of the processing interval on grayscale variation in self-developing films subjected to radiographic exposure. An in vitro experimental design was employed, in which 36 radiographs were obtained using Dental Film Ergonom-X® and a Gendex® intraoral X-ray unit (70 kVp, 7 mA, 0.63 s), following the paralleling technique and using an 11-step aluminum step wedge for optical density calibration. Films were processed at six different time intervals (0, 1, 2, 4, 12, and 24 hours after exposure) and subsequently digitized under standardized conditions. Grayscale mean values were extracted from 40 × 40-pixel regions of interest using ImageJ software, and data were analyzed using the Kruskal–Wallis test and DSCF post-hoc method at a 5% significance level. Intermediate grayscale steps—particularly steps 4 to 7—showed significant sensitivity to delayed processing (p < 0.05), revealing differences between immediate processing and 24-hour intervals. These findings indicate that chemical instability of the sensitized emulsion over time, associated with progressive oxidation of silver particles, may compromise contrast and diagnostic potential, especially for tasks requiring subtle tonal discrimination such as early caries detection. Staining artifacts were also observed, likely related to non-homogeneous monobath distribution during activation. It is concluded that the interval between exposure and processing directly influences tonal stability in self-developing films, and immediate processing is recommended to ensure image predictability, tonal fidelity, and diagnostic safety.