The effect of low level laser on condylar growth during mandibular advancement in rabbits

Continuous forward mandibular advancement was performed in fourteen male Albino rabbits with the mean age of 8 weeks and the mean weight of 1.5 ± 0.5 kg, with acrylic inclined planes. The rabbits were randomly assigned into two groups after 4 weeks. LLL (KLO3: wave length 630 nm) was irradiated at 3 points around the TMJ, through the skin in the first group. The exposure was performed for 3 minutes at each point (a total of 9 minutes) once a day for 3 weeks. The control group was not exposed to any irradiation. The rabbits in both groups were sacrificed after two months and the histological evaluation of TMJ was performed to compare fibrous tissue, cartilage, and new bone formation in condylar region in both groups. Disc displacement was also detected in both groups. Student's t-test, Exact Fisher and Chi square tests were used for the statistical analysis.The formation of fibrous tissue was significantly lower, while bone formation was significantly greater in lased group as compared with control group. The thickness of cartilage did not differ significantly between two groups.Irradiation of LLL (KLO3) during mandibular advancement in rabbits, increases bone formation in condylar region, while neither increase in the cartilage thickness nor fibrous tissues was observed.The Class II malocclusion has been called the most frequent skeletal problem in the orthodontic practice [1,2]. The solution can involve the use of functional or fixed orthodontic appliances, or both [3]. It has been claimed that the most frequent skeletal problem in Class II patients is mandibular retrognathia [4,5]. In the treatment of Class II malocclusion, capability to alter patients' facial growth is of particular interest, namely by means of functional appliances [6,7]. The findings from animal and human studies have been accepted as evidence that functional appliances can stimulate condylar [8-10] or mandibular growth,[11,12] and are able to make changes in the underlying skeletal pattern of