Reduction in unstimulated salivary flow rate in burning mouth syndrome

Burning mouth syndrome (BMS) is a chronic condition of burning of the tongue and oral mucosa. It is often accompanied with complaints of xerostomia, although it is unknown whether the dryness is a sensory change similar to the burning sensation or due to hyposalivation. To determine whether there is change in salivary flow rate, whole salivary flows were measured in BMS patients.

A clinical ambispective study was conducted. Patients' clinical files were reviewed for stimulated and unstimulated whole salivary flow. Patients were divided into four groups based on diagnosis into Sjögren's syndrome (SS), BMS, BMS taking oral drying medications (BMS-med), and control (C). Whole stimulated (SF) and unstimulated flow (USF) measurements were collected and compared among groups. Data were analysed with ANOVA, Levene's test, Tukey's test and Games-Howell test.

Twenty SS, 22 BMS, 24 BMS-med and 15 C were included in the study. SF was significantly lower in SS (0.59 ml ± 0.36) compared with BMS (1.56 ml ± 0.65, p <0.001), BMS-med (1.44 ml ± 0.64, p <0.001) and C (2.32 ml ± 1.06, p = 0.001). USF was significantly lower in SS (0.12 ml ± 0.10) compared with BMS (0.30 ml ± 0.18, p = 0.002), BMS-med (0.27 ml ± 0.21, p = 0.022) and C (0.52 ml ± 0.26, p <0.001). SF was not significantly different between BMS and C (p = 0.172) and BMS-med and C (p = 0.096). Both BMS and BMS-med had significantly lower USF compared with C (p = 0.040 and p = 0.018 respectively). SF in BMS was not significantly affected by number of oral drying medications (p = 0.254); however, USF was significantly lower with two or more oral drying medications (0.13 ml ± 0.07) compared with one oral drying medication (0.32 ml ± 0.22) (p = 0.034).

BMS patients have statistically significant decreased unstimulated salivary flow rate with non-statistically significant decreased stimulated flow rate. Salivary flow rates in BMS patients are decreased further by medication usage whose side effects include dry mouth. This suggests that hyposalivation may play a role in causing dry mouth in BMS, which may respond to treatment with a sialogogue.