Photobiomodulation (PBM) therapy is an application of light for the therapeutic purpose of improving tissue regeneration, reducing inflammation, or inducing analgesia. While several questions regarding the PBM effects are well documented, questions on penetration and distribution of light through the hard and soft tissues of the maxillofacial region, in vivo, have not been well investigated. The aim of this in vivo study was to assess pulsed 635 nm extraoral PBM light distribution through the cheek and upper and lower jaws, with and without teeth.
Material and methods
In 23 patients, an extraoral LED device emitting pulsing light (wavelength: 635 nm, maximum output power: 140 mW/cm , frequency: 2,5 Hz, duty cycle: 50%) was used to illuminate the cheek, upper and lower jaws. A power meter and sensor registering the optical power was placed intraorally to assess light penetration through tissues.
Light penetration was present in all patients, in both soft and hard tissues. Light distribution through the cheek was 148,6 μW while in the upper jaw it was 6,1 μW and in the lower jaw 5,4 μW. There was a significant difference in light distribution between soft tissues (cheek) and hard tissues (upper and lower jaw). There was no significant difference between patients with teeth and without teeth.
This study demonstrated an existent penetration of extraoral PBM 635 nm light through the soft and hard tissues in the MF region. The significant difference in light attenuation between the soft and hard tissues indicates a need for reassessment of dosage in treating different tissues in patients, in order to obtain an adequate amount of energy delivered and thus an optimal therapeutic outcome.
It is possible to better photobiomodulation therapy in the fields of oral and maxillofacial surgery by optimizing dosage.
Photobiomodulation therapy enhances regeneration in the maxillofacial region.
Photobiomodulation improves implant osseointegration in the maxillofacial region.
Photobiomodulation (PBM) therapy (also known as Low-level light therapy, LLLT) is an application of light, usually with lasers or LEDs, for the therapeutic purpose of improving tissue regeneration, reducing inflammation, or inducing analgesia. LED (light-emitting diodes) light is an effective alternative to laser light in the field of photobiomodulation, which enables treatment of larger areas and also does not emit any heat, which is important for eliminating the danger of tissue damage. PBM is a subject of over 300 clinical studies, as well as systematic reviews, for a broad range of musculoskeletal pathologies that have noted positive clinical outcomes. These studies have resulted in several expert consensuses documents that endorse the use of PBM therapy in standard clinical practice especially for pathologies in the maxillofacial region. The effects of different wavelengths on the metabolism of bone, skin and mucosa, both in vivo and in vitro , is well documented. Most of the studies utilize visible red and infrared light. Several studies have documented the rationale for use of PBM treatments for bone augmentation as well as in osteointegration of implants. , ,
Unlike many other forms of light therapies, PBM is a non-ablative, non-surgical, low dose light treatment. It differs from another form on low dose light treatment, photodynamic therapy (PDT) that utilizes an exogenous photosensitive dye to destroy tumor cells or microbes. PBM treatments can either stimulate healing or regeneration and reduce inflammation or pain. While it is capable of inhibiting certain deleterious pathophysiological processes, it does not aim to destroy biological tissues. There is now a better understanding of several molecular mechanisms of PBM involving biological targets in the mitochondria, on the cell membrane, and extracellular milieu. ,
PBM devices typically utilize a light spectrum between 600 to 1000 nm (red to infrared light), with output irradiance (power density) from 1 to 200mW/cm 2 in pulsed or continuous mode. Treatment duration and repetitions vary depending on the device characteristics and disease being treated. While several questions regarding the PBM effects are well documented, questions on penetration and propagation of light through tissues in vivo have not been well investigated. This critical question can not only influence the design of a PBM device but also treatment planning and delivery as it will determine the amount of light energy delivered to specific target tissue. ,
The aim of this study was to evaluate whether 635 nm extraoral pulsating PBM therapy light is able to penetrate fully the upper and lower jaw, with and without teeth, and to obtain quantitative values of light distribution. The secondary aim is to evaluate the difference of light distribution through the cheek alone compared to the upper and lower jaw, with and without teeth.
Material and methods
Clinical study design: Following approval by the Ethical Committee of the Faculty of Dentistry, University of Belgrade (no. 36/3, 36/4, and 36/5) a clinical study was conducted at the Clinic for Maxillofacial Surgery, Faculty of Dentistry, University of Belgrade from 1 st June to 1 st September 2019. Patients were treated according to the principles established in the Helsinki Declaration. Signed informed consent was obtained from each patient before treatment. The study included 23 patients who came to the clinic for treatments in the maxillofacial region. Following informed consent, subjects were included in this study if the areas to be treated at the Department were not within the area of planned illumination, so illumination was performed on healthy tissues, if they are over 18 years of age, with no systemic diseases and with either full dentition or complete edentulism. Exclusion criteria were the presence of skin or mucosal scar tissue in the areas examined, presence of dental implants, or presence of porcelain-fused to metal crowns on teeth.
In all patients, a LED lamp (Repuls7, Repuls Lichtmedizintechnik GmbH, Austria) emitting red pulsing light (wavelength: 635 nm, maximum output power: 140 mW/cm , frequency: 2,5 Hz, duty cycle: 50%) was used to illuminate the cheek, upper and lower jaw. Patients were positioned in an upright position in a dental chair and the lamp had an extraoral position, perpendicular to the area to be illuminated at a distance of 30 cm from the skin. One researcher performed the illumination (V. K.) while the other researcher (M. P.) read and registered the values from the power meter display. The researcher performing the illumination was blinded to values of penetration. The treatment surface irradiance was measured and at the given distance and was 27,2 mW/cm 2 . The most important beam parameters are summarized in Table 1 .
|Manufacturer||REPULS Lichtmedizintechnik GmbH|
|Model Identifier||REPULS 7|
|Number & Type of Emitters (laser or LED)||LED, 7|
|Wavelength and bandwidth [nm]||635|
|Pulse mode [CW or Hz, duty cycle]||2.5 Hz, 50%|
|Beam spot size at target [cm2]||200,96|
|Irradiance at target [mW/cm2]||27.2|
|If pulsed peak irradiance [mW/cm2]||27.2|
|Exposure duration [sec]||10|
|Radiant exposure [J/cm2]||0.2|
|Radiant energy [J]||NA|
|Number of points irradiated||NA|
|Area irradiated [cm2]||NA|
|Number and frequency of treatment sessions||NA|
|Total radiant energy over the entire treatment course [J]||NA|
Optical power assessment : A power meter (PM100D, Thorlabs Inc. USA) and sensor (S120C, Thorlabs Inc. USA) registering the optical power was manually placed intraorally to assess light penetration through tissues. To measure light penetration through the cheek, the operator held the power meter sensor directly along the buccal (cheek) mucosa in all 23 subjects ( Figure 1 ). To measure penetration through the upper jaw, the sensor was held palatally along the upper alveolar process in the molar-premolar regions. Finally, to measure the lower jaw penetration, the sensor was held lingually along the lower alveolar process in the molar-premolar region. For these jaw penetration measurements, we divided subjects into two groups, 12 subjects with full dentition and 11 with complete edentulism. An ambient intraoral value of light was registered before illumination and deducted from all measurements. As the light device is pulsed, we measured optical power for 10 seconds at each site and registered the highest value.