Assessment of the effect of low-energy diode laser irradiation on gamma irradiated rats’ mandibles Eman M.F. El-Maghraby a , Dalia H. El-Rouby b, *, Ali M. Saafan c a Health Radiation Research Department, National Centre for Radiation Research and Technology (NCRRT), Cairo, Egypt b Oral Pathology Department, Faculty of Oral and Dental Medicine, Cairo University, Egypt c National Institute of Laser Enhanced Sciences (N.I.L.E.S.), Cairo University, Egypt 1. Introduction Therapeutic lasers are identified and differentiated from surgical lasers by different names include soft, cold and low intensity laser therapy or irradiation (LILT or LILI). These types are used for the treatment of injuries of soft and hard tissue and are classified as class III medical devices. 1,2 Laser systems used for biostimulation include argon, HeNe, galium–aluminum, Nd:YAG, and the galium–aluminum–arsenide (GaAlAs) diode lasers. 3 Previous studies suggested LILT to have bio-stimulative, regenerative, analgesic, anti-inflammatory and immune effects, 4 dependent of radiation parameters such as wave- length, dose, and intensity of laser light. 5 LILT exerts photobiostimulation or photobioinhibition effects on cells, increasing or decreasing the cellular functions. The incident light energy is absorbed by cellular photoreceptors, such as a r c h i v e s o f o r a l b i o l o g y 5 8 ( 2 0 1 3 ) 7 9 6 – 8 0 5 a r t i c l e i n f o Article history: Accepted 1 October 2012 Keywords: Laser therapy Low-level Bone and bones Radiotherapy Osteoradionecrosis a b s t r a c t Objective: The purpose of the present study was to evaluate the biostimulative and regen- erative effects of low intensity laser irradiation (LILT) (applied before or after initiation of radiotherapy) on gamma irradiated rats’ jaw bones. Methods: Forty eight male Albino rats were equally divided into two groups: group 1, in which the left side of the mandible was subjected to three successive sessions of laser (LILT) prior to whole body gamma radiation (2 Gy/3 fractions/week) and group 2, received whole body gamma radiation (2 Gy/3 fractions/week) prior to three successive sessions of laser applied to left side. The right side of both groups was used as gamma irradiated non-lased control group. Each group was then subdivided into four equal subgroups (a, b, c, d) according to the time of scarification (3, 7, 14, 21 days respectively). Specimens were subjected to histological, histomorphometric and scanning electron microscopic examina- tions. Results: Thin irregular bone trabeculae and widened marrow spaces were identified in the control group. The lased sides of groups 1 and 2 demonstrated regular, thick and continuous bone trabeculae. Ultrastructurally, collagen fibres of the control group appeared irregularly arranged and more spaced compared to groups 1 and 2. Normal-sized osteocytic lacunae were seen in the lased groups, as compared to the wide lacunar spaces noted in the control group. Histomorphometric analysis showed a significant increase in the area of bone trabeculae, as well as the width of compact bone, for the lased groups. Conclusions: LILT seemed to attenuate the radiation-related damage in alveolar bones. # 2012 Elsevier Ltd. All rights reserved. * Corresponding author at: 19 Street # 270, New Maadi, Cairo, Egypt. Tel.: +2 01005032353. E-mail address: daliaelrouby@hotmail.com (D.H. El-Rouby). Available online at www.sciencedirect.com journal homepage: http://www.elsevier.com/locate/aob 0003–9969/$ – see front matter # 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.archoralbio.2012.10.003