Background: The purpose of this study was to investigate the effect of low-level laser irradiation on the secretory function and histology of the salivary glands of a murine animal model.

Material and methods: Sixteen 8 week-old, female BALB/c mice were divided randomly into two groups: control group (n=8) was irradiated with sham light, and laser group (n=8) was irradiated with low-level laser. The salivary flow rate (ml/min) and delay on salivation (min) parameters were measured at baseline and after 10 days of irradiation. Glandular weight (gm.) of parotid, submandibular and sublingual glands and cellular volume of salivary glands (sq. µm) were measured after 10 days of irradiation.

Result: There was no statistically significant effect of low-level laser irradiation on salivary flow rate, intra-group comparison for the experimental (p = 0.44) and for the control one (p = 0.96), and inter-group comparison of the mean difference between the two groups (p = 0.747). The delay in salivation was significantly higher in the experimental group compared to baseline (p= 0.011). The weight of the parotid glands of the experimental group was statistically significantly higher than the control group (p = 0.003). The results showed a non-statistically significant effect of the low-level laser irradiation on the cellular volume of the glandular duct area (p = 0.094). However, the study showed that both serous and mucous acini areas of the experimental group were significantly smaller than the area of the control group [(p-value = 0.006), (p = 0.005) respectively].

Conclusions: The used low- level laser irradiation protocol in the present study was able to neither significantly increase salivary flow rate nor decrease the delay on salivation. However, it was able to increase the parotid glands weight and decrease the cellular volume of serous and mucous acini areas.

Future studies using different low-level laser irradiation protocols are needed to establish the ultimate protocol to effectively stimulate salivary secretion.