Histomorphometric Analysis: Effect of Laser and LED on Mandibular Growth

Objectives: To compare the possible effect of laser and light emitting diodes of the same wavelength (850 nm) and energy output (6J/cm²) on mandibular condylar growth as evaluated by histomorphometric analysis in rats.

Methods: Twenty-four Sprague-Dawley rates were divided equally into six groups of four animals each.  Groups were: 1 (Laser), 2 (Laser + Functional appliance); 3 (LED); 4 (LED + Functional Appliance), 5 (Functional appliance [positive control]) and 6 (negative control). Animals were treated for ten minutes every day on the right side of the mandibular condyle with either treatment or using a sham control in both groups 5 and 6. After four weeks, all animals were euthanized and mandibles were processed for histology and histomorphometric analysis. Surface areas of the cartilaginous layers of the condyles were measured in each group. These layers are fibro-cartilaginous (FL) layer, proliferative layer (PL), chondrocyte layer (CL) and hypertrophic layer (HL). Comparison between groups was analyzed by ANOVA test with alpha set at 0.05 using SPSS version 19 statistical package. 

Results: There was statistically significant increase (60%) in the FL in the treated condyles by the laser group compared to the counter control condyles. However, LED increased both the FL and CL significantly (twice) and PL (140% more) than the untreated condyles. Although LED and FA significantly increased all condylar layers twice compared to the untreated condyles, LED alone was more effective in increasing condylar layers than a combination treatment (LED and FA) did. However, LED and FA increased the CL more than the Laser and FA group.  

Conclusions: Both LED and Laser of similar wavelength and power output increased mandibular condylar surface areas as compared to the control groups. It seems that each treatment has a selective stimulating effect on different mandibular condylar layers. LED is more effective on condylar growth than laser or FA.