Effects of He-Ne laser irradiation on the periodontal blood vessel remodeling during orthodontic movement in rabbits

Xinhua SUN; Min WANG; Xu WANG

ABSTRACT

BACKGROUND:

Blood vessel remodeling is the basis of the remodeling of orthodontic periodontal tissues. Can He-Ne laser irradiation promote blood vessel remodeling and then accelerate the process of the remodeling of orthodontic periodontal tissues or not?

OBJECTIVE:

To investigate the effects and action mechanisms of He-Ne laser irradiation on the blood vessel remodeling of orthodontic periodontal tissues of rabbits.

DESIGN:

Randomized controlled study.

SETTING:

Animal experimental center of Jilin University.MATERIALS Thirty-five flap-eared rabbits weighting 2.0 kg were provided by Animal Experimental Center of Jilin University, license No. SYXK(Ji)2002-0002, production license No. SCXK2003-0003. Animal intervention met animal ethical standard. HNGSQ-1 type of He-Ne laser therapeutic instrument was produced in Shanghai. HPIAS-1000 image analytical system was produced by Tongji Medical University. CD34 monoclonal antibody with the product number of MAB-0034 and vascular endothelial growth factor monoclonal antibody with the product number of MS-350 were offered by Fuzhou Maixin Company.

METHODS:

Experiments were performed at the Provincial Laboratory of Animal Experimental Center of Jilin University from May to December 2003. ①Thirty-five flap-eared rabbits were randomly divided into seven groups, an unforced group and forced 1-, 3-, 5-, 7-, 14- and 21-day groups with 5 rabbits in each group. A stainless steel closing coil spring was deposited between the maxillary first molar and the corresponding maxillary incisor bilaterally, delivering 0.08 N force. The right maxillary of rabbits of each forced group was irradiated by He-Ne laser, and the left side was as control.The cheek corresponding to the right maxillary first molar was selected as irradiation spot and then received He-Ne laser local irradiation. He-Ne laser's wavelength is 632.8 nm, power output of 20.0 mW and energy density of 2.50 J/cm2.Animals of the unforced group did not proceed with anything, sacrificed after raising for a week. Animals of the forced groups were respectively sacrificed on days 1, 3, 5, 7, 14 and 21. ②The premaxillary bones, including the upper first molar, were cut into sagittal sections. Sections were preceded with CD34 and vascular endothelial growth factor immunohistochemical straining. Microvessel density and microvessel area were measured in the tension zone and the pressure zone of orthodontic periodontal tissues. The staining intensity for vascular endothelial growth factor was evaluated by the measurement of gray value using the Computer Image Analyzing System.MAIN OUTCOME

MEASURES:

①Gray integral of vascular endothelial growth factor after immunohistochemical staining. ②Microvessel density and microvessel area.

RESULTS:

Thirty-five rabbits were involved in the result analysis. ①Microvessel density and microvessel area in He-Ne laser irradiated sides were all obviously larger than in the control sides in every forced group in the tension zone and the pressure zone (P ＜ 0.05-0.01), except for the 1-day group. ②In the 1-day group, the vascular endothelial growth factor expressions in periodontal tissues in pressure zone of He-Ne laser irradiated sides were significantly lower than that of control sides (P ＜ 0.05). In the 3- and 5-day groups, vascular endothelial growth factor expressions in pressure zone of irradiated sides were significantly higher than that of control sides (P ＜ 0.05). The vascular endothelial growth factor expressions in pressure zone of both irradiated sides and control sides reached a peak at 5-day group. The vascular endothelial growth factor expressions of irradiated sides were significantly higher than the corresponding control sides in tension zone at 3-, 5- and 7-day group (P ＜ 0.05). The vascular endothelial growth factor expressions in tension zone of both irradiated sides and control sides reached a peak at 14-day group.

CONCLUSION:

He-Ne laser irradiation promotes blood vessel remodeling of periodontal tissues, increases the vascular endothelial growth factor concentrations in periodontal tissues and makes the angiogenesis of periodontal tissues more active, followed by the remodeling of orthodontic periodontal tissues.