Aim: This study aimed to evaluate changes in the optical density of dentin in primary molars with deep caries three to six months after they were subjected to partial carious dentin removal. Study design: This was a blind controlled, clinical therapy study. Standardized digitalized bitewing radiographs of 42 teeth were analyzed using Adobe Photoshop® to quantitatively determine the gray scale of the affected dentin beneath the restoration, in comparison with healthy dentin. A mixed-effects model was used for statistical analysis. The gray tone level was considered a dependent variable; the tooth region and the time, in addition to the interaction between them, were the independent variables. Values of p < 0.05 were significant. Results: During the interval between time zero and three months, the gray tone levels of affected dentin varied from 80.99 ± 3.17 to 98.57 ± 3.17; i.e., an estimated increase of 18 (p < 0.0001). The values for healthy dentin ranged from 118.22 ± 3.17 to 122.02 ± 3.17; i.e., a mean increase of four in the gray tone levels (p = 0.0003). During the interval between three and six months, both healthy and affected dentin showed similar behavior (98.57 ± 3.17 to 103.32 ± 3.20 and 122.02 ± 3.7 to 126.56 ± 3.20, respectively) (p = 0.0001). Conclusions: Significant increments were observed in the optical density of the affected dentin after three months compared to that of healthy dentin in primary molars treated using the partial carious dentin removal technique.