Effects of high-frequency near infrared laser irradiation on experimental tooth movement–induced pain in rats

• Published in: Lasers in medical science 2022-08, Vol.37 (6), p.2697-2706
• Main Authors: Nakatani, Ayaka, Kunimatsu, Ryo, Tsuka, Yuji, Sakata, Shuzo, Horie, Kayo, Gunji, Hidemi, Ito, Shota, Kado, Isamu, Putranti, Nurul Aisyah Rizky, Terayama, Ryuji, Tanimoto, Kotaro
• Format: Article
• Language: English
• Subjects: Analgesics; Astrocytes; c-Fos protein; Dentistry; Fos protein; Glial fibrillary acidic protein; Grooming; Histochemistry; I.R. radiation; Immunoreactivity; Infrared lasers; Irradiation; Laser applications; Lasers; Maxillofacial; Medicine; Medicine & Public Health; Microglia; Near infrared radiation; Nickel; Optical Devices; Optics; Original Article; Orthodontics; Pain; Photonics; Proteins; Pulse duration; Quantum Optics; Semiconductor lasers; Short pulses; Side effects; Teeth; Titanium
• ISSN: 1435-604X; 0268-8921; 1435-604X
• DOI: 10.1007/s10103-022-03543-x

Discomfort and dull pain are known side effects of orthodontic treatment. Pain is expected to be reduced by near-infrared (NIR) lasers; however, the mechanism underlying effects of short-pulse NIR lasers in the oral and maxillofacial area remains unclear. This study aimed to examine the effects of high-frequency NIR diode laser irradiation on pain during experimental tooth movement (ETM) on 120 J. NIR laser with 910 nm wavelength, 45 W maximum output power, 300 mW average output power, and 200 ns pulse width (Lumix 2; (Lumix 2; Fisioline, Verduno CN, Italy) was used for the experiment. A nickel–titanium-closed coil was used to apply a 50-gf force between the maxillary left-side first molar and incisor in 7-week-old Sprague–Dawley rats (280–300 g) to induce ETM. We measured facial-grooming frequency and vacuous chewing movement (VCM) period between laser-irradiation and ETM groups. We performed immunofluorescent histochemistry analysis to quantify levels of Iba-1, astrocytes, and c-fos protein-like immunoreactivity (Fos-IR) in the trigeminal spinal nucleus caudalis (Vc). Compared with the ETM group, the laser irradiation group had significantly decreased facial-grooming frequency ( P  = 0.0036), VCM period ( P  = 0.043), Fos-IR ( P  = 0.0028), Iba-1 levels ( P  = 0.0069), and glial fibrillary acidic protein (GFAP) levels ( P  = 0.0071). High-frequency NIR diode laser irradiation appears to have significant analgesic effects on ETM-induced pain, which involve inhibiting neuronal activity, microglia, and astrocytes, and it inhibits c-fos, Iba-1, and GFAP expression, reducing ETM-induced pain in rats. High-frequency NIR diode laser application could be applied to reduce pain during orthodontic tooth movement.