Patrícia Fonseca

Correlation between enzyme production, germ tube formation and susceptibility to fluconazole in Candida species isolated from patients with denture-related stomatitis and control individuals.

INTRODUCTION Phospholipase and proteinase secretion in yeasts of the genus Candida has been described as a relevant virulence factor. Also, germ tube formation by Candida albicans is associated with its invasive capacity and is considered an important pathogenic mechanism. METHODS To link the production of hydrolytic enzymes with the capacity to produce infection, 232 clinical isolates of yeasts from the oral cavity of 140 individuals wearing removable maxillary protheses were studied. The sample was composed of 70 patients with denture-related stomatitis (DRS) and 70 individuals with normal palatal mucosa. For strains identified as C. albicans, the correlation between germ tube formation and their capacity to cause infection was studied and the presence of Candida dubliniensis was investigated. Susceptibility to fluconazole was evaluated. RESULTS Candida albicans was the only species producing phospholipase and germ tube. We observed a higher level of production of phospholipase in cases of infection compared with commensals. Significant differences between the two groups of C. albicans isolates were observed as to germ tube production. Only, Candida glabrata showed lower susceptibility to fluconazole. CONCLUSION The results reinforced the idea that C. albicans is the most frequent and can be the most pathogenic yeast in oral candidosis. However, the strains isolated from DRS patients and healthy individuals showed the same virulence factors. It seems that several virulence attributes are involved in the infective process but no single factor contributes to Candida virulence. Candida dubliniensis was absent in the oral cavity of individuals with and without DRS.

Effect of Denture-Related Stomatitis Fluconazole Treatment on Oral Candida albicans Susceptibility Profile and Genotypic Variability

Denture-related stomatitis (DRS) is the most common condition affecting removable-denture wearers, and Candida albicans the most frequent pathogenic agent. Systemic antifungal treatment is indicated but recurrences are frequent. The aim of this study was to characterize the oral load, fluconazole susceptibility profile and genotypic variability of oral C. albicans isolates from patients with DRS before (T0), immediately after fluconazole treatment (Tat) and after 6-months follow-up (T6m). Eighteen patients presenting DRS and treated with fluconazole were followed at the Faculty of Dentistry of Oporto University. Seventy C. albicans isolates were obtained and identified using standard cultural and biochemical multi-testing. Fluconazole susceptibility was tested by E-test®. Microsatellite-primed PCR was performed to assess the genotypic variability of C. albicans isolates. The patients’ mean age was 58.0±3.2 years, and 55.6%/44.4% had total/partial dentures. Before treatment, 22.2%, 44.4% and 33.3% of the patients presented DRS type I, II or III, respectively. Fluconazole treatment healed or improved DRS in 77.8% of the patients, accompanied by an 83.5% reduction in oral C. albicans load. However, after 6-months, oral C. albicans load increased significantly and DRS severity was similar to the one observed before treatment. Moreover, the prevalence of patients presenting fluconazole resistant isolates of C. albicans increased significantly throughout the study: T0-5.6%, Tat-10.0% and T6m-42.9%. A change in the genotypic variability of C. albicans isolates was also verified, being mostly associated to fluconazole susceptibility profile change. In conclusion, fluconazole presents a good short-term DRS treatment efficiency, but may be associated to a long-term emergence of C. albicans fluconazole resistance.

Higiene de Próteses Removíveis

Resumo A protese removivel e, com alguma frequencia (por condicionantes economicas, esteticas ou funcionais), a unica solucao para a reabilitacao de arcadas desdentadas. A colocacao de uma protese provoca uma alteracao qualitativa e quantitativa da placa microbiana aumentando a predisposicao dos seus portadores ao desenvolvimento de determinadas patologias (carie dentaria, periodontopatias e processos inflamatorios da mucosa). Consequentemente, a higiene oral e a higiene protetica sao essenciais para a manutencao da saude dos tecidos. Dos diversos metodos de higiene protetica descritos a escovagem e o mais utilizado. No entanto, alguns autores consideram essencial a introducao de uma solucao quimica de imersao como adjuvante do processo mecânico. Atendendo ao descrito, foram objectivos deste estudo: - quantificar a placa microbiana presente na superficie de proteses removiveis higienizadas por um processo mecânico (escovagem com agua) e por um processo mecânico/quimico (escovagem com agua associada a uma solucao quimica de imersao); - comparar a eficacia, na remocao da placa microbiana dos dois metodos referidos. Constituiram a nossa amostra 44 individuos (adultos de ambos os sexos) que se encontravam a confeccionar nova(s) protese(s) na consulta de Protese Removivel da Faculdade de Medicina Dentaria da Universidade do Porto. Para a populacao estudada, a analise dos resultados permite concluir que: 1- Aproximadamente metade das proteses removiveis avaliadas apresenta um deficiente grau de higiene apos escovagem (50,9%) assim como apos associacao de uma solucao quimica de imersao a escovagem (42,1%); 2- A diferenca de eficacia dos metodos analisados na remocao da placa microbiana da superficie protetica nao e estatisticamente significativa.

In vitro study of the insertion and disinsertion effect on retention of two attachment systems of an overdenture on two implants

Objective: Implant-supported overdentures are a valid treatment option for edentulous patients. The use of two mandibular implants is considered the minimum standard of care. This study evaluated the retentive force of two attachments and their respective connection systems in a mandibular implant-supported overdenture. Methods: Two acrylic blocks were prepared: two parallel implants set 22 mm apart were embedded in one of the blocks, while in the other were positioned the female systems for each attachment system tested (Dalbo Ball BTI® and Locator® with female components in both clear and pink nylon). A specific machine was designed to measure the retentive force of the attachments over the cycles applied. The speed of insertion/disinsertion was 0.5 Hz, applied constantly. Results: The clear nylon Locator® attachments registered the highest initial retention value (85.7 N), followed by the Dalbo-Ball® system (62.1 N) and pink nylon Locator® (49.6 N). After 5400 cycles, the mean force exerted was highest in the clear nylon Locator® attachments (42.3 N) followed by Dalbo-Ball® (34.3 N) and pink nylon Locator® (24.6 N). Conclusion: The initial retention force decreases over time for the attachment systems tested.