Mouthwash as a non-invasive method of indocyanine green delivery for near-infrared fluorescence dental imaging

Abstract

Significance: X-ray imaging serves as the mainstream imaging in dentistry, but it involves risk of ionizing radiation.

Aim: This study presents the feasibility of indocyanine green-assisted near-infrared fluorescence (ICG-NIRF) dental imaging with 785-nm NIR laser in the first (ICG-NIRF-I: 700 to 1000 nm) and second (ICG-NIRF-II: 1000 to 1700 nm) NIR wavelengths.

Approach: Sprague Dawley rats with different postnatal days were used as animal models. ICG, as a fluorescence agent, was delivered to dental structures by subcutaneous injection (SC) and oral administration (OA).

Results: For SC method, erupted and unerupted molars could be observed from ICG-NIRF images at a short imaging time (<1 min). ICG-NIRF-II could achieve a better image contrast in unerupted molars at 24 h after ICG injection. The OA could serve as a non-invasive method for ICG delivery; it could also cause the glow-in-dark effect in unerupted molars. For erupted molars, OA can be considered as mouthwash and exhibits outstanding performance for delivery of ICG dye; erupted molar structures could be observed at a short imaging time (<1 min) and low ICG dose (0.05 mg / kg).

Conclusions: Overall, ICG-NIRF with mouthwash could perform in-vivo dental imaging in two NIR wavelengths at a short time and low ICG dose.

Keywords: indocyanine green; indocyanine green delivery; mouthwash; near-infrared fluorescence dental imaging; oral administration.

Fig. 1

Schematic diagram of ICG-NIRF dental imaging with SC and OA ICG delivery. (a) Schematic diagram and (b) typical ICG-NIRF images of P21 erupted molars with SC (4 h) and OA (10 min) methods. M1: first molar; M2: second molar.

Fig. 2

The SC-based ICG-NIRF imaging for unerupted molars under the first (ICG-NIRF-I) and second (ICG-NIRF-II) NIR windows. (a) ICG-NIRF-I; (b) ICG-NIRF-II; and (c) image contrast of ICG-NIRF-I and ICG-NIRF-II under different imaging times. M1: the first molar; M2: the second molar. ICG dose: $5\mathrm{mg}/\mathrm{kg}$. * is significant at $<0.05$; ** is significant at $<0.01$; and *** is significant at $<0.001$.

Fig. 3

The SI-based ICG-NIRF dental imaging of the erupted molars (P21) under NIRF-I and NIRF-II. (a) ICG-NIRF-I; (b) ICG-NIRF-II; and (c) image contrast of ICG-NIRF-I and ICG-NIRF-II under different imaging times. ICG dose: $5\mathrm{mg}/\mathrm{kg}$. * is significant at $<0.05$; ** is significant at $<0.01$; and *** is significant at $<0.001$.

Fig. 4

Comparison of OA and SC ICG delivery, erupted and unerupted molars were imaged at short imaging time ($<1\min$) with ICG-NIRF-I imaging. (a) Erupted and unerupted molars by using OA ICG delivery. (b) Erupted and unerupted molars by using SC ICG delivery; (c) Image contrast of OA and SC method. M1: the first molar; M2: the second molar. ICG dose: $5\mathrm{mg}/\mathrm{kg}$. * is significant at $<0.05$; ** is significant at $<0.01$; and *** is significant at $<0.001$.

Fig. 5

Comparison of OA-based and SC-based ICG-NIRF dental imaging in the unerupted molars at long imaging time (24 h). (a) The ICG-NIRF dental imaging with OA ICG delivery; (b) ICG-NIRF dental imaging with SC ICG delivery; and (c) image contrast of OA and SC methods. M1: the first molar; M2: the second molar. ICG dose: $5\mathrm{mg}/\mathrm{kg}$. * is significant at $<0.05$; ** is significant at $<0.01$; and *** is significant at $<0.001$.

Fig. 6

The OA-based ICG-NIRF imaging for unerupted molars under the first (ICG-NIRF-I) and second (ICG-NIRF-II) NIR windows. (a) ICG-NIRF-I; (b) ICG-NIRF-II; and (c) image contrast of ICG-NIRF-I and ICG-NIRF-II under different imaging times. * is significant at $<0.05$; ** is significant at $<0.01$; and *** is significant at $<0.001$.

Fig. 7

The OA-based ICG-NIRF dental imaging for the erupted molars (P21) under NIRF-I and NIRF-II. (a) ICG-NIRF-I; (b) ICG-NIRF-II; and (c) image contrast of ICG-NIRF-I and ICG-NIRF-II under different imaging times. * is significant at $<0.05$; ** is significant at $<0.01$; and *** is significant at $<0.001$.

Fig. 8

The OA-based ICG-NIRF dental imaging of the unerupted molars (P14) with low ($1\mathrm{mg}/\mathrm{kg}$) and high ($5\mathrm{mg}/\mathrm{kg}$) ICG doses, and imaging after 48 h of the OA ICG delivery. (a) ICG-NIRF-I dental imaging with low and high ICG and (b) ICG-NIRF-II dental imaging with low and high ICG.

Fig. 9

The OA-based ICG-NIRF dental imaging of the erupted molars (P60 young adult rats) with ICG dose ranging from 0.05 to $1\mathrm{mg}/\mathrm{kg}$, and imaging under NIRF-I and NIRF-II. (a) ICG-NIRF-I dental imaging and (b) ICG-NIRF-II dental imaging.

Fig. 10

The OA-based ICG-NIRF imaging for the laser-treated abnormal erupted molars in P21 rats. (a) Wide-field pictures of abnormal erupted molar. (b) The endoscopic ICG-NIRF images of abnormal erupted molar and normal molar. C1: the first cusps; C2: the second cusps; and C2: the third cusps.

Fig. 11

The OA-based ICG-NIRF imaging for the laser-treated abnormal erupted molars in young adult (P60) rats. (a) Wide-field pictures of abnormal erupted molar. (b) The endoscopic ICG-NIRF images of abnormal erupted molar and normal molar. C1: the first cusp; C2: the second cusp; and C2: the third cusp.