In vivo assessment of DNA damage induced in oral mucosa cells by fixed and removable metal prosthodontic appliances.

Given long-term effect on oral tissues due to contact with dental appliances, the biocompatibility studies of casting alloys are of great importance. It has been previously documented that metal dental appliances, due to corrosion, might induce genotoxic and mutagenic effects in cells. Therefore, the aim of presented study was to examine the genotoxicity of two dental casting alloys (Co-Cr-Mo and Ni-Cr) commonly used in fixed and removable prosthodontic appliances that are in contact with the oral epithelium for 5 years or more. For that purpose, 55 age-matched subjects were included in the study; 30 wearers of prosthodontic appliances and 25 controls. Buccal cells of oral mucosa were collected and processed for further analysis. The cell viability has been assessed by trypan blue exclusion test, while genotoxic effect of metal ions on DNA in oral mucosa cells was studied by use of alkaline comet assay. Results have shown significantly higher comet assay parameters (tail length and percentage DNA in the tail) in the group wearing metal appliances. Both subjects with Co-Cr-Mo alloy and Ni-Cr alloy showed significantly higher comet assay parameters when compared with controls. It has been confirmed that metal ions released by the two base metal dental casting alloys examined in this study, might be responsible for DNA damage of oral mucosa cells. Therefore, the results of this study emphasize the importance of the in vivo evaluation of dental materials with respect to their genotoxicity, which is of major importance to ensure long-term biocompatibility.

The effect of low-level laser therapy on salivary glands in patients with xerostomia.

OBJECTIVE: The aim of this study was to investigate the effect of low-level laser irradiation on the secretory function of salivary glands in 34 patients with xerostomia (dry mouth). BACKGROUND DATA: Xerostomia, a common complaint of oral dryness within the elderly population, is caused by a reduction in normal salivary secretion due to different causes. Treatment is aimed at increasing salivary flow, although in most cases it remains palliative. MATERIALS AND METHODS: In this study, laser light from a pulsed Ga-As laser operating at 904 nm was applied bilaterally on each salivary gland area: extraorally on the parotid and submandibular gland areas and intraorally on the sublingual gland area. The operational probe distance from the irradiated area was 0.5 cm resulting in an irradiance of 246 mW/cm(2). The exposure time was 120 sec per daily treatment during 10 consecutive days. The average energy density per exposure was 29.5 J/cm(2). The control group consisted of 16 patients who were treated with 15 mL of a 2% citric acid solution applied as a mouth rinse for 30 sec. RESULTS: The average difference in the amount of salivation (dQ-sal, mL/min) before and after laser therapy increased linearly from dQ-sal = 0.05 mL/min on the first day, up to dQ-sal = 0.13 mL/min on the last (10th) day of therapy. In the control group, the average dQ-sal initially demonstrated a gradual increase, with a reversal of the trend toward the end of the therapy period and eventually yielding no correlation between the duration of therapy and dQ-sal. CONCLUSION: The results of our study indicate that the effects of low-level laser therapy on salivary glands are not only stimulating, but also regenerative to a degree since the glandular response to the same amount of applied laser energy increased linearly over time.