We would like to sincerely express our gratitude to the Faculty of Veterinary Medicine Research Council of Islamic Azad University, Tabriz branch for approval and financial support for this extensive evaluation of compressive pressure and histomorphologic changes tri-calcium phosphate and bioglass of magnesium paste irradiated with low level laser in repair of experimentally created a critical size defect, middle of bilateral mandibular bones in rabbit. Problems statement: The purpose of this study was to determine the effect of calcium phosphate mixed with bioglass and magnesium and being irradiated with low level laser in rabbit mandibles. Approach: 48 adult New Zealand white rabbits were used. The mandible bone was bilaterally exposed and with help of dental trephine 3 mm in width and 10 mm in depth was made on each side in all rabbits .These rabbits were divided randomly into 4 groups of 12 rabbits in each. In group (I) The defect was left empty as control, group( II ) exposed to low level laser irradiation ,whereas In groups (III) the defects were packed with tri-calcium phosphate(40%) and bioglass of magnesium paste ( 60%), and group IV the defects were filled with same paste and next day was subjected to therapeutic regimen of low level laser with wavelength of 780 nm, with power density of 10 mW intensity and energy density of 6 J/cm2, duration of application 10 minutes for 15 days. The animals were subdivided into two subgroups of 6 rabbits each for 30 and 60 days. At the end of observation period bisected mandibles into two left and right samples from 6 rabbits. A series of samples were used for mechanical properties and other ones used for histomorphological evaluation in all four groups. For mechanical properties using Zwick/Roell MDTL Machine with speed of 0.01 mm/s having Proportional Integral Deferential (PID) controller. In assessing the variation obtained data was analyzed using paired-t-test. Results: Data of the compressive pressure was revealed an average for normal bone 275.0±4 N whereas it was 71.2±12.7N for group I in 1 month duration and that was recorded 108.4±18.2 N for group II and 122.0±10.8 N for group III and 142.0± 18.8 for group IV at the end of 1 month. These values were 102.9.±10.2 N for group I and 168.4±6.8 N for group II and 182.6±14.2N for group III and 220.0 ±8.6 for group IV at the end of two months after implantation. Low level laser therapy beside calcium phosphate paste significantly accelerated healing and increased mechanical properties in mandible defect.
