Effects of low-dose irradiation on human osteoblasts and periodontal ligament cells.

OBJECTIVE: To investigate the effects of dental x-ray on proliferation and mineralization in human primary osteoblasts as well as on proliferation and apoptotic potential in human periodontal ligament (PDL) cells. DESIGN: Primary osteoblasts and PDL cells were irradiated with various doses of periapical radiography by repeated exposures and further incubated for 1, 3 or 7 days. Cell proliferation was assayed by BrdU incorporation. The effect of dental x-ray on mineralization in osteoblasts either before or after x-ray exposures was determined by Alizarin red staining. Both mRNA and protein expressions of BCL-2, an anti-apoptotic gene, and BAX, a pro-apoptotic gene, in PDL cells were analyzed by RT-qPCR and immunoblotting analysis, respectively. RESULTS: Neither the proliferative nor the mineralization ability of irradiated osteoblasts was different from that of non-irradiated osteoblasts at any doses or time points. By contrast, there was a significant decrease in the proliferation of PDL cells on day 3 after repeated exposures to dental x-ray for 20 times (P < 0.05), whereas the ratio of BCL-2 to BAX mRNA and protein expressions in these irradiated PDL cells was significantly increased (P < 0.05). CONCLUSIONS: Upon multiple exposures to dental x-ray used in intraoral radiography up to 20 times, there is no effect on the proliferation or the mineralization of osteoblasts, whereas the proliferative and apoptotic potentials of PDL cells are transiently decreased.

In vitro comparison of self versus professionally applied remineralizing materials.

OBJECTIVE: To compare the effect of 4 remineralizing materials on the incipient artificial carious lesion and its proximal sound enamel when used with fluoride dentifrice. STUDY DESIGN: Models mimicking proximal contact were made, each of which was placed with an artificial carious specimen in contact with a sound enamel specimen. Each carious specimen was treated with one of four materials: glass ionomer cement (GIC), resin modified glass ionomer cement (RMGIC), 5000 ppm sodium fluoride (F-gel), and casein phosphopeptide amorphous calcium phosphate (CPP-ACP). The GIC and RMGIC specimens were thermocycled. Then all specimens were pH-cycled for 5 days with twice a day soaking in 1,000 ppm NaF dentifrice solution. Specimens were examined by polarized light microscopy and lesion area quantified by image analysis. RESULTS: RMGIC significantly yielded smaller areas of lesion than CPP-ACP and GIC (p < 0.05). F-gel reduced more area of lesion than CPP-ACP significantly (p < 0.05). In the associated contact, RMGIC significantly reduced the area of lesion better than CPP-ACP (p < 0.05). CONCLUSIONS: The most effective remineralizing material in reducing the carious lesion areas was RMGIC followed by F-gel, GIC and CPP-ACR The demineralization inhibitory effects on the associated sound contact enamel followed the same trend.