Abstract
Malocclusions, such as an open bite and high canines, are often encountered in orthodontic practice. Teeth without occlusal stimuli are known as hypofunctional teeth, and numerous atrophic changes have been reported in the periodontal tissue, including reductions in blood vessels in the periodontal ligament (PDL), heavy root resorption, and reduced bone mineral density (BMD) in the alveolar bone. Low Level Laser (LLL) has been shown to have a positive effect on bone formation and the vasculature. Although the recovery of hypofunctional teeth remains unclear, LLL is expected to have a positive influence on periodontal tissue in occlusal hypofunction. The aim of the present study was to elucidate the relationship between LLL and periodontal tissue in occlusal hypofunction. Twenty-four male rats aged 5 weeks were randomly divided into control and hypofunctional groups. An anterior metal cap and bite plate were attached to the maxillary and mandibular incisors in the hypofunctional group to simulate occlusal hypofunction in the molars. LLL irradiation was applied to the maxillary first molar through the gingival sulcus in half of the rats. Rats were divided into four groups; control, control+LLL, hypofunctional, and hypofunctional+LLL. Exposure to LLL irradiation was performed for 3 minutes every other day for 2 weeks. Animals were examined by Micro-CT at 5 and 7 weeks and were subsequently sacrificed. Heads were resected and examined histologically and immunohistologically. The hypofunctional group had obvious stricture of the PDL. However, no significant differences were observed in the PDL and alveolar bone between the hypofunctional+LLL and the control groups. In addition, the expression of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF)-positive cells were higher in the hypofunctional + LLL group than in the hypofunctional group. These results indicated that LLL enhanced the production of bFGF and VEGF in the periodontal tissue of hypofunctional teeth.
Highlights
Malocclusions, such as an open bite, high canines, or underoccluded teeth, are often encountered in orthodontic practice
These findings suggest that low level laser therapy (LLLT) may have a positive effect on newly formed bone
Occlusal hypofunction using a bite-raising appliance resulted in changes in the periodontal tissue; periodontal ligament (PDL) thickness and bone mineral density (BMD) in the maxillary alveolar bone were thinner and lower, respectively, than these in the controls
Summary
Malocclusions, such as an open bite, high canines, or underoccluded teeth, are often encountered in orthodontic practice. LLL may accelerate the process of fracture repair or increase bone mineral density (BMD) [11] These findings suggest that low level laser therapy (LLLT) may have a positive effect on newly formed bone. The use of low-level diode lasers in periodontal therapy has recently been considered to improve wound healing in gingival tissue and accelerates gingival healing after LLLT in sites undergoing gingivectomy [12,13]. Due to their wavelength characteristics, low-level diode lasers are able to reach epithelial tissues, and subepithelial tissues, and laser irradiation is expected to induce the proliferation of osteoblasts [14] and periodontal ligament fibroblasts [15]
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