OCT/OCTA 用于在体人牙、牙龈以及血液微循环的早期病变诊断研究（特邀）

Objective Oral diseases, such as dental caries and periodontal diseases, are prevalent global health issues with high morbidity and economic burdens. Early detection is crucial for non-invasive intervention and reversal of lesions, but traditional methods such as dental X-rays and periodontal probing suffer from limitations including ionizing radiation, subjectivity, and insensitivity to early pathological changes. Optical coherence tomography (OCT) combined with OCT angiography (OCTA) provides a non-invasive, high-resolution alternative for the diagnosis of early lesions in dental hard tissues, gingiva, and microcirculation. However, existing studies focus predominantly on single-type tissue assessment, and a systematic evaluation of the effects of different central wavelengths on OCT performance for integrated imaging of multi-tissue oral structures remains lacking. Most dental OCT studies use 1310 nm systems, with limited comparative analysis of 850 nm OCT under identical conditions. Moreover, previous comparisons using time-domain OCT (TD-OCT) systems are limited by inferior image quality and do not include gingival or microcirculatory assessment. This study aims to systematically compare the imaging characteristics and complementarity of 850 nm spectral-domain OCT (SD-OCT) and 1310 nm swept-source OCT (SS-OCT) systems for the in vivo diagnosis of early lesions in human teeth, gingiva, and blood microcirculation. This work highlights the necessity of wavelength optimization to meet clinical demands for multi-target, high-precision, and integrated detection in oral disease screening, thus promoting early diagnosis and personalized treatment. Methods Two custom-built OCT systems are employed: an 850 nm SD-OCT system and a 1310 nm SS-OCT system. The 850 nm SD-OCT system uses a superluminescent diode source with a -3 dB bandwidth of approximately 100 nm, achieving an axial resolution of approximately 4 μm in air, a lateral resolution of approximately 14 μm, an imaging depth of approximately 2.4 mm, and a signal-to-noise ratio (SNR) of approximately 103 dB. The 1310 nm SS-OCT system features a swept-wavelength laser source with a scan frequency of 100 kHz and a -10 dB bandwidth of approximately 136 nm, providing an axial resolution of approximately 11 μm, a lateral resolution of approximately 22 μm, an imaging depth of approximately 4.8 mm, and an SNR of approximately 100 dB. In vivo imaging is performed on the teeth of volunteers, including sound teeth and teeth with early lesions. Imaging results include en face images, B-scans, and OCTA images of the microvasculature. Quantitative analyses include the demineralization thickness of dental hard tissues (calculated based on pixel counts and refractive indices), gingival margin thickness, and microcirculation parameters (e.g., vessel area percentage and total vessel length) using tools such as AngioTool. Results and Discussions The experimental results show distinct complementary performance between the two wavelength systems. In dental hard tissues, 850 nm SD-OCT provides high-resolution surface morphology details, enabling visualization of subtle enamel changes. For instance, en face images reveal surface topography, but the limited penetration depth obscures deeper structures such as the enamel-dentine junction (EDJ). In contrast, 1310 nm SS-OCT excels in penetration and clearly displays deep demineralization zones and the EDJ in B-scans. Using the 1310 nm system, early lesion areas exhibit a high-scattering band, allowing clear demineralization thickness measurements averaging approximately 115.4 μm. In contrast, limited by its shallower penetration depth and wavelength-specific response in dental tissue, the 850 nm system does not reveal such a bright, high-contrast band, with an average demineralized thickness of approximately 93.7 μm. Notably, 1310 nm SS-OCT distinguishes demineralization from dental calculus based on morphological features, such as elevated“hill-like”structures in calculus regions, enhancing diagnostic accuracy. In gingival imaging, both systems capture gingival profiles, but 1310 nm SS-OCT offers superior depth for visualizing gingival sulci and margins because of its stronger penetration depth in oral tissues. Gingival thickness measurements for regions adjacent to early lesions are approximately 582.3 μm (@850 nm) and approximately 605.2 μm (@1310 nm), reflecting inflammation-induced edema. B-scans clearly delineate gingival-tooth interfaces, supporting the objective assessment of periodontal health. Overall, the experimental results underline the significant potential of OCT for the early detection and evaluation of periodontal conditions. For microcirculation, OCTA reveals significant differences between sound teeth and teeth with early lesions. In the gingival area adjacent to the lesion, 850 nm SD-OCT achieves high-resolution imaging of superficial capillaries and displays detailed vascular morphology such as tortuosity and dilation. In comparison, 1310 nm SS-OCT penetrates deeper and captures broader vascular networks but with slightly blurred details due to lower resolution. Quantitative analysis confirms higher vessel area percentage in lesion areas (850 nm: 20.83% versus 12.32%; 1310 nm: 25.84% versus 18.03%), indicating inflammation-driven angiogenesis. The 850 nm system shows greater sensitivity to superficial changes, while the 1310 nm system provides more comprehensive deep perfusion data, highlighting their complementarity. Discussion shows that 850 nm SD-OCT is ideal for high-resolution applications such as superficial enamel changes and capillary morphology, whereas 1310 nm SS-OCT is suitable for deep tissue evaluation. The functional complementarity of OCT systems with different central wavelengths enables comprehensive, multi-dimensional assessment of oral diseases. Conclusions This study systematically evaluates 850 nm SD-OCT and 1310 nm SS-OCT for the in vivo diagnosis of early oral lesions. The results confirm their complementary performance: 850 nm SD-OCT provides high-resolution imaging for superficial enamel changes and capillary morphology, while 1310 nm SS-OCT enables deep penetration for lesion localization, demineralization thickness measurement, gingival thickness quantification, and deep microcirculation assessment. This study promotes comprehensive oral health monitoring by establishing a complementary clinical strategy of“high-resolution superficial imaging combined with deep-tissue penetration”, thus laying a foundation for precise and non-invasive clinical applications. This research provides critical experimental evidence for optimizing OCT-based strategies in the screening and treatment of early oral diseases.