Low-Level Laser Therapy on Bone Repair of Rat Tibiae Exposed to Ionizing Radiation

Objective: the purpose of this study was to evaluate the effects of low-level laser therapy (LLLT) on the repair of rat tibiae exposed to ionizing radiation (IR). Background data: IR causes structural changes that delay bone tissue repair. Properly dosed, LLLT improves the bone repair process. Methods: Seventy-two healthy Wistar rats were distributed into the following groups: Group I, sham control; Group II, LLLT; Group III, IR; and Group IV, IR and LLLT. Groups III and IV received a single dose (30 Gy) of gamma radiation and underwent surgery 28 days later. A noncritical sized bone defect (diameter 2.5 mm) was surgically created in all groups. Groups II and IV received three applications of postsurgical LLLT (GaAlAs, 808 nm, 100 mW, 0.028 cm(2), 3.57 W/cm(2), 20 sec, 2 J, approximately equal to 71.4 J/cm(2)) on alternate days. Histomorphometry was assessed following digital image analysis. Results: the samples were evaluated on days 7, 14, and 21 after surgery; the IR protocol resulted in a significant reduction (p<0.018) in bone formation in Group III compared with Group I. Significant increases (p