Accuracy of laser fluorescence in assessment of various caries removal techniques: an in vitro validation

This study aimed to evaluate the accuracy of laser fluorescence (LF) readings in detection of caries removal by various techniques (CRTs).

A hundred and eighty extracted human molar teeth included in the study which were scored 3, 4, and 5 according to ICDAS. Each score group was randomly assigned to 4 subgroups according to CRT including ceramic bur (Group A), carbide bur (Group B), carbide bur with alumina abrasion (Group C), and carbide bur with bioactive glass (BAG) abrasion (Group D) (n = 15 for each group). A LF device (DIAGNOdent Pen, Kavo) was used to determine remaining caries. Histological sections of the teeth were examined under a dental operating microscope for validation. The data were analyzed using Fisher Freeman Halton, Fisher's Exact, Pearson Chi-Square, Bonferroni Adjusted Z tests, ROC analysis, Kappa statistic and Binary Logistic Regression(p < 0.05).

Histological examination revealed no significant differences among the CRTs and ICDAS scores (p > 0.05 for each). However, a significant difference was found between histological assessment and LF in ICDAS 5 score, specifically between Group B and Group D (p = 0.022), regarding caries presence. LF readings demonstrated over 0.9 area under curve (AUC) value regardless of CRT, except for ICDAS-4 score, and Group D in ICDAS-5 score. Overall, the AUC of LF was found to be 0.880 for the 38 cut-off point (p < 0.001), indicating a high level of accuracy. The univariate and multiple models showed the tested CRTs had no effect on the caries presence (p > 0.050).

The CRTs examined in this study demonstrated similar efficacy in terms of caries removal. However, the application of bioactive glass on caries-affected dentin may lead to overestimations in the LF readings. Additionally, LF on the cavity floor may not be clinically suitable for teeth with ICDAS 4 scores.

The clinical determination of caries removal endpoint is based on a multifactorial decision. However, when selective removal of soft dentin is performed, especially with bioactive glass abrasion in deep caries lesions, higher cut-off points might be determined in laser fluorescence readings to decide further operative intervention.