Diagnostic accuracy of Transmitted-light plethysmography for the assessment of pulpal circulation in traumatized young permanent incisors

Transmitted light plethysmography (TLP) is a noninvasive, objective optical method used to assess dental pulp circulation and evaluate pulp vitality. This study aimed to develop a quantitative diagnostic approach for TLP and assess its accuracy through cross-correlation analysis of plethysmographic signals obtained from both the tooth and the finger. A total of 131 maxillary incisors from 97 pediatric patients (aged 6-17 years) were categorized into three groups: nontraumatized teeth, traumatized vital teeth, and traumatized nonvital teeth. Standard diagnostic procedures, including assessments for discoloration, percussion sensitivity, periapical translucency, and electric pulp testing (EPT), were performed alongside TLP evaluation, 3 to 18 months following dental trauma. Tooth plethysmograms were acquired using a 525 nm light-emitting diode directed through the examined teeth, while simultaneous finger plethysmograms were recorded as reference signals. Cross-correlation coefficients (R-values; 0 < R < 1) were calculated between the tooth and finger signals for each tooth, and diagnostic cutoff thresholds were determined using receiver operating characteristic (ROC) curve analysis based on the maximum Youden index. Statistically significant differences in R-values were observed among the three groups. The optimal diagnostic cutoff was identified as 0.40 (95% confidence interval: 0.38-0.45), at which TLP demonstrated a sensitivity of 0.94 and a specificity of 0.88, outperforming EPT. Logistic regression analysis incorporating all pulp testing methods revealed a significant association with pulp vitality status. Furthermore, the area under the ROC curve (AUC) for TLP combined with standard tests was significantly greater than that of any individual model. These results indicate that TLP offers improved diagnostic precision for identifying nonvital pulp and may serve as a valuable adjunct to conventional pulp vitality assessments.