Viability of photodynamic therapy on the treatment of denture stomatitis. In vivo studies

These in vivo studies evaluated 1 – the effectiveness of photodynamic therapy (PDT) on the inactivation of Candida albicans in a murine model of oral candidosis; 2 – compared the clinical and mycological efficacy of PDT with that of topical antifungal therapy (nystatin oral suspension) for the treatment of denture stomatitis (DS) as well as to identify and determine the prevalence of Candida species in DS. In the first investigation, mice were immunosupressed with subcutaneous injections of prednisolone. Tetracycline hydrochloride on drinking water was managed to change the oral microflora. They were kept in a sedative state after injection of chlorpromazine chloride and a suspension of C. albicans (10⁷ CFU/mL) was swabbed in the oral cavity. Four days after oral infection, PDT was performed on the dorsum of the tongue using a topical administration of Photogem® at 400, 500 or 1000 mg/L and, after 30 minutes, illumination with 305 J/cm² of LED light at 455 or 630 nm. Then, the number of surviving yeast was determined (CFU/mL) and analyzed by ANOVA and Holm-Sidak tests (P < 0.05). Animals were sacrificed, the tongues surgically removed and processed for histological evaluation of yeast presence and inflammatory reaction. In the clinical trial, patients (n = 40) were randomly assigned to one of two groups of 20 subjects each; NYS group: patients received topical treatment with nystatin (100,000 IU) four times daily for 15 days; PDT group: maxillary denture and palate of patients were sprayed with 500 mg/L of Photogem® and, after 30 min of incubation, illuminated by LED light at 455 nm (37.5 and 122 J/cm², respectively) three times a week for 15 days. Mycological cultures taken from dentures and palates and standard photographs of the palates were performed at baseline (day 0), at the end of the treatment (day 15) and at the follow-up (days 30, 60 and 90 after the beginning of the treatments). Colonies were quantified (CFU/mL) and identified by biochemical tests. Fisher’s exact test was used to analyse the predisposing factors. The ln(CFU/mL) values were evaluated by ANOVA and Tukey tests. The severity of inflammation of the palate in the photographs was classified by two blind observers, and the agreement between them was assessed by the kappa test. Significant difference was assumed when P < 0.05. In the animal study, PDT resulted in a significant reduction of C. albicans recovered from tongue (P < 0.001). There was no difference between the concentrations of Photogem® and the wavelengths of LED light used. The histological evaluation of the tongue revealed that PDT causes no significant adverse effects to the local mucosa. The results of the clinical trial demonstrated that both treatments reduced significantly the CFU/mL values at the end of the treatments and on day 30 of the follow-up period compared to the baseline (P < 0.05). Only age of dentures was a significant (P = 0.045) predisposing factor associated with the degree of inflammation of the palate. NYS and PDT groups showed a rate of clinical success of 53 and 45%, respectively. C. albicans was the most prevalent species identified, followed by C. tropicalis and C. glabrata. The results of both in vivo investigations suggest that PDT may be an alternative treatment for oral candidosis.