Three consecutive days of application of LED therapy is necessary to inhibit experimentally induced root resorption in rats: a microtomographic study

Abstract

Previous studies have suggested that phototherapy may modulate orthodontic tooth movement and the incidence of root resorption. We aimed to identify a minimal dose-response relationship to LED therapy with regard to orthodontic tooth movement (OTM) and root resorption in rats. Forty-eight male Wistar rats were divided into six groups with equal and random distribution: control (C) no intervention; three daily LED irradiation (CLED); submitted only to OTM (RR); OTM and LED irradiation on the first day (LED1); OTM and two LED irradiation on the first and second days (LED2); and OTM and three LED irradiation on the first, second, and third days (LED3). Orthodontic appliance was installed in groups RR, LED1, LED2, and LED3 to promote OTM. Animals from groups CLED, LED1, LED2, and LED3 received LED therapy (940 nm, 4 J, 4 J/cm2) according to each group of treatment. After 7 days, all the animals were sacrificed. The jaws were fixed and scanned with microtomography (micro-CT). The micro-CT images were reconstructed on 2D and 3D models. These models were used to identify and measure root resorption number and dimensions (diameter, depth, and volume). The distance between the first and second molars was used to verify tooth displacement. The results showed that LED3 group had significantly lower number of root resorption. The root resorption dimensions (diameter and depth) had no significant differences among the experimental groups. LED3 group had significant tooth displacement in relation to C and CLED groups. In conclusion, three daily LED therapy doses are required to inhibit root resorption after appliance of orthodontic forces.

Infrared Light-Emitting Diode (LED) Effects on Orthodontic Tooth Movement

“…Similar force has been used previously in laser studies and induced tooth movement (16)(17)(18). Due to the small intraoral space in rats, we performed the irradiation on the facial skin area (adjacent to the upper molars) to accommodate the probe of the LED instrument (12)(13)(14)(15)(16)(17)(18)(19).…”

Phototherapy is unable to exert beneficial effects on orthodontic tooth movement in rat molars

“…In this regard, irradiation should be applied during the initial phase of the acute inflammatory response and during the recruitment and differentiation of osteoclasts. 19 Considering the amount of tooth movement in all groups, less OTM was detected under LED and laser irradiation in relation to the control. When both irradiated groups were compared, no significant differences were detected between them.…”

“…25 Therefore, some studies have confirmed the acceleration of tooth movement stimulated by laser therapy, 18,20,23,26 and other studies have showed reduced resorption in relation to root resorption. 19,24,27 The root resorption areas on the mesial surface of the distal palatal root in both the laser and LED groups presented similar effects, although the specimens from the LG exhibited slightly more resorption area than that of the DG. However, while the extent of resorption area varied in each group, extensive lacunae were observed mostly in the LG.…”

Light transmittance of the periodontium

“…This process results in beneficial therapeutic outcomes including but not limited to the alleviation of pain or inflammation, immunomodulation, and promotion of wound healing and tissue regeneration.^ [1]. PBM therapy was found to have multiple clinical benefits, which includes reducing pain [2][3][4][5][6][7], improving wound healing [8][9][10][11], accelerating bone healing [12][13][14][15][16][17], promoting osteointegration [18], facilitating orthodontic tooth movement [19][20][21][22][23][24][25][26], stimulating bone formation [27][28][29][30][31], and improving periodontal tissue repair and decreasing inflammation and root resorption [23,26,32]. The light sources were laser or a light-emitting diode (LED).…”