# Quantitative Assessment Methods of Early Enamel Caries with Optical Coherence Tomography: A Review
## 4 Quantitative Assessment Methods of Early Enamel Caries with OCT
### Quantitative Assessment Based on Reflectivity
However, \(R_{\%}\) is rarely applied. A summary of the above research results is shown in Table 2. \begin{table}
\begin{tabular}{c c c c} \hline
**Reference** & **OCT System** & **Sample Preparation** & **Reflectivity Result (dB\(\times\)\(\upmu\)m)** \\ \hline \multirow{8}{*}{[PERSON] et al. [49]} & \multirow{8}{*}{1310-nm PS-OCT, axial/lateral.} & Sample number: 10 bovine enamel blocks for in vitro detection & \\  & & Solution: pH 4.8 & \(\Delta R\) for the fixed depth \\  & & demineralization solution & \(\Delta R\) for the edge detection \\  & & Method: 5 windows for each block, demineralization for 0–4 days, respectively. & \(\Delta R\) for 4.8 & \(\Delta R\) for 4.8 \\ \hline \multirow{8}{*}{[PERSON] et al. [50]} & \multirow{8}{*}{1310-nm PS-OCT, axial/lateral resolution 20/30 \(\upmu\)m.} & Sample number: 15 human posterior teeth for in vitro detection & \\  & & Solution: pH 4.3 & \\  & & demineralization solution and & \\  & & PS-OCT, axial/lateral & pH 7.0 & \\  & & resolution 20/30 \(\upmu\)m. & remineralization solution & \\ \cline{2-4}  & & Method: occlusal areas were exposed to 14-day PH cycling, which consisted of 6 h & \\  & & demineralization and 17 h & \\  & & remineralization a day. & \\ \hline \multirow{8}{*}{[PERSON] et al. [59]} & \multirow{8}{*}{1321-nm CP-} & Sample number: Two teeth in 20 patients for 20 visits detection & \\  & & & Solution: two types of adhesives & \\ \cline{1-1} \cline{3-4}  & & Method: The adhesives were used to bond the brackets. & \\ \cline{1-1} \cline{3-4}  & & Demineralization around & \\ \cline{1-1} \cline{3-4}  & & orthodontic brackets was & \\ \cline{1-1} \cline{3-4}  & & detected every 3 months for & \\ \hline \multirow{8}{*}{[PERSON] et al. [60]} & \multirow{8}{*}{1317-nm PS-OCT, axial/lateral resolution 20/20 \(\upmu\)m.} & Sample number: 10 bovine enamel blocks for 20 visits into detection & \\ \cline{1-1} \cline{3-4}  & & Solution: pH 4.6 & \\ \cline{1-1} \cline{3-4}  & & demineralization solution and & \\ \cline{1-1} \cline{3-4}  & & pH 4.8 & \\ \cline{1-1} \cline{3-4}  & & remineralization solution & \\ \cline{1-1} \cline{3-4}  & & Method: 6 windows for each block, demineralization for 8 days and remineralization for 4-day periods & \\ \hline \end{tabular}
\end{table} 
Table 2: Results of quantifyin0p-lg enamel caries with reflectivity. In addition, other researchers have used the mean relative reflectivity (mRR) proposed in retinal OCT imaging to assess fissure caries by using 1325-nm SS-OCT [64]. The mRR is calculated from the difference between the fissure area signal and sound enamel signal. Although the mRR of demineralized fissures were at least 6 times higher than those of sound fissures at 250, 500 and 1000 \(\upmu\)m depths beneath the surface, the mRR was unable to accurately describe lesion mineral density (\(r_{s}=-0.31\)). In summary, the integrated reflectivity of enamel lesion calculated by OCT is linearly correlated with mineral loss. Most results confirm that the integrated reflectivity of enamel increases after demineralization, but individual studies show the opposite. Researchers often use the integrated reflectivity in combination with lesion depth to evaluate the lesion severity. However, the calculation of the integrated reflectivity suffers from similar problems to the lesion depth calculation.