Efficacy of low-molecular weight chitosan against Candida albicans biofilm on polymethyl methacrylate resin.

BACKGROUND: Candida biofilm is a major cause of denture stomatitis. We aimed to compare the efficacy of low-molecular-weight chitosan solutions against Candida albicans biofilm on polymethyl methacrylate (PMMA) resin. METHODS: Various types of chitosan were tested for anti-Candida activity by broth dilution. Two types were selected for further testing on 24-hour C.albicans biofilm formed on PMMA specimens. Specimens were randomly distributed among experimental groups, including 0.1% and 0.2% acetic acid, 3 and 6 mg/mL of oligomer chitosan and 30 kDa chitosan solutions, effervescent tablet (Polident), and 0.2% chlorhexidine, and immersed for 5 min to 12 h. The viability of C. albicans after cleansing were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Remaining viability was calculated into percentage relative to respective controls and analyzed using ANOVA with Tukey post-hoc tests. Live/dead fluorescence microscopy was also performed. RESULTS: Chitosan solutions had high efficacy against C. albicans biofilm on PMMA. The mean relative viability compared to control after 12-h immersion was 6.60 ± 4.75% and 12.72 ± 6.96% for 3 and 6 mg/mL oligomer, respectively, and 11.68 ± 4.81% and 18.08 ± 6.20% for 3 and 6 mg/mL 30 kDa chitosan, respectively. CONCLUSIONS: Low-molecular-weight chitosan solution is an effective antifungal denture cleanser that can significantly reduce C. albicans viability in biofilm on PMMA.

Effect of different cleansing agents and adhesive resins on bond strength of contaminated zirconia.

PURPOSE: This study was observed the effect of cleansing agents and adhesive resins on shear bond strength (SBS), surface morphology and phase transformation of saliva and silicone disclosing medium contaminated zirconia. METHODS: The 110 zirconia specimens size 5×5×1mm were fabricated and randomly divided into 5 surface treated groups: Non-contaminated (PC) Saliva and silicone disclosing medium contaminated without cleansing (NC) Surface contaminated and cleansing with Phosphoric acid (PO) Ivoclean (IC) or Hydrofluoric acid (HF). The twenty of each surface treated specimens were selected and bonded with Panavia F2.0 (P) and Superbond C&B (S) for SBS test (n=10). The data was analyzed by Kruskal-Wallis H and Mann-Whitney U test. The remaining specimens of each surface treated groups were examined by SEM and XRD. RESULTS: The saliva and silicone disclosing medium contaminated zirconia without cleansing group (PNC) had the lowest SBS when Panavia F2.0 was used for cementation (p<0.05). The SBS of surface cleansing groups (PPO, PIC and PHF) were not different from the non-contaminated group (PPC) (p>0.05). However, there were no difference in SBS among groups when cementation with Superbond C&B (SPC, SNC, SPO, SIC and SHF) (p>0.05). There was no morphologic changing that could be observed by SEM. The XRD showed little phase transformation when surfaces were contaminated and cleaned. CONCLUSIONS: The saliva and silicone disclosing medium contaminated zirconia should be cleaned with Phosphoric acid, Ivoclean or Hydrofluoric acid for 20s prior to cementation with Panavia F2.0. However, the surface cleansing was not necessary when cementation with Superbond C&B.

Maxillary Sinus Floor Augmentation Using Xenograft: Gene Expression and Histologic Analysis.

PURPOSE: Many histologic and histomorphometric studies as well as systematic reviews have shown the clinical success of the use of anorganic bovine bone (ABB, Bio-Oss) in maxillary sinus floor augmentation (MSFA). The molecular processes involved in bone healing are, however, still unknown. The aims of this study were to explore gene expression associated with bone remodeling and inflammation in MSFA sites. MATERIALS AND METHODS: The mRNA expression levels of runt related transcription factor 2 (RUNX2), receptor activator of NF-kB ligand (RANKL), osteoprotegerin (OPG), matrix metallopeptidase 9 (MMP-9), tartrate-resistance acid phosphatase (TRAP), and interleukin-1beta (IL-1ß), as well as the ratio of RANKL/OPG were compared between alveolar bone of a group after MSFA with ABB and a maxillary posterior edentulous bone group. Twenty-one bone samples were collected at the time of implant placement after 6 months of MSFA or tooth extraction. Fourteen bone samples from the MSFA group and from the maxillary posterior edentulous bone without MSFA group were taken to analyze gene expression by real-time reverse transcription polymerase chain reaction (RT-PCR). Seven bone samples from the MSFA group were used for histologic analysis. RESULTS: Real time RT-PCR revealed no statistically significant difference in gene expression level of RUNX2, RANKL, OPG, MMP-9, TRAP, and IL-1ß, or in the ratio of RANKL/OPG. Histology showed bone-lining cells at the edge and osteocyte inside newly formed bone. Residual grafted particles were in close contact with new bone. CONCLUSION: After a healing period of 6 months, ABB particles did not have an effect on the expression of genes associated with bone remodeling and inflammation. In addition, histologic evidence supports that ABB particles are replaced by new bone formation and do not affect bone healing.

Improving shear bond strength between feldspathic porcelain and zirconia substructure with lithium disilicate glass-ceramic liner.

This study investigated the shear bond strength (SBS) between veneering porcelain and zirconia substructure using lithium disilicate glass-ceramic as a liner. The mineral phases and microstructures of lithium disilicate glass-ceramic at temperature range of 800-900°C were preliminarily investigated. SBSs of porcelain-veneered zirconia specimens with and without lithium disilicate glassceramic liner fired at the same temperature were determined. Results showed that SBSs of veneering porcelain and zirconia with lithium disilicate glass-ceramic liner was notably increased (p<0.05). Specimens from the group with the highest SBS (59.7 MPa) were subject to thermocycling up to 10,000 cycles and their post-thermocycling SBSs investigated. Though weakened by thermocycling, SBSs were above the clinically acceptable limit (25 MPa) of ISO 9693. Fractographic analysis revealed mixed cohesive and adhesive failures. It was concluded that lithium disilicate glass-ceramic is a potential liner which generated high SBS between veneering porcelain and zirconia.