Objective: Gram-positive cariogenic bacteria are etiological agents in dental caries; therefore, strategies to inhibit these bacteria to reduce the incident of this disease have intensified. In this study, we investigated antibacterial activities of titanates and gold-titanates against Lactobacillus casei (Lc) and Streptococcus mutans (Sm). Materials and methods: Monosodium titanate (MST), nanomonosodium titanate (nMST) and amorphous peroxo-titanate (APT), which are inorganic compounds with high-binding affinity for specific metal ions, were used. Total bacterial proteins were measured to represent bacterial cell mass after 24 h incubation with gold-titanates. We further examined the effect of nMST-Au(III) concentrations (10,200,400 mg/L) on Lc and Sm cell viability over time via Live/Dead fluorescent staining and colony forming units (CFUs). Transmission electron microscopy (TEM) was used to determine specific locations on the bacterial cells affected by the nMST-Au(III). Results: We found all gold-titanates and APT alone reduced bacterial protein for Lc (p value <0.001) while only MST-Au(III) and nMST-Au(III) affected Sm growth (p value <0.001). Overall, nMST-Au(III) showed the most effectiveness against both Lc and Sm at 400 mg/L. The Live/Dead staining showed all concentrations of nMST-Au(III) affected Lc growth but only 200 and 400 mg/L nMST-Au(III) interrupted Sm growth. The growth curves based on CFUs/mL showed all nMST-Au(III) concentrations affected growth of both Lc and Sm. TEM images showed nMST-Au(III) attached to Lc and Sm cell wall and were internalized into both cells. Conclusions: nMST-Au(III) demonstrated potential antimicrobial activity against Gram-positive cariogenic bacteria. These results support further development of nMST-Au(III) as a potential novel material to prevent dental caries.

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This study aimed to examine the retentive characteristics of each retentive element material and the effects from thermocycling using the two implant-retained mandibular overdenture model. Two stud abutments and three retentive element materials; nylon, polyetheretherketone (PEEK) and polyvinylsiloxane (PVS) were used in this study. Four tested groups, with a total of 40 overdentures, were fabricated, including a Locator® abutment with nylon retention insert (NY), Novaloc® abutment with PEEK retention insert (PK), Locator® abutment with PVS retention insert (RL), and Novaloc® abutment with PVS retention insert (RN). The retentive force (N) was measured before thermocycling, and at 2500, 5000, and 10,000 cycles after thermocycling. Significant changes in the percentage of retention loss were found in the NY and PK groups (p < 0.05) at 6 and 12 months for the RL group (p < 0.05) after artificial aging. The RN group exhibited a constant retentive force (p > 0.05). The tendency of the percentage of retention loss significantly increased for PEEK, nylon, and PVS silicone over time. The results of the present study implied that retentive element materials tend to lose their retentive capability as a result of thermal undulation and water dispersion. Nylon and PEEK, comprising strong polar groups in polymer chains, showed a higher rate of retention loss than polyvinylsiloxane.

PURPOSE This study evaluated the relationship among translucency, crystalline phase, grain size, and fracture toughness of zirconia. MATERIALS AND METHODS Four commercial zirconia - Prettau ® Anterior ® (PA), Prettau ® (P), InCorisZI (ZI), and InCorisTZI (TZI)- were selected for this study. The bar specimens were prepared to determine fracture toughness by using chevron notched beam method with four-point bending test. The grain size was evaluated by a mean linear intercept method using a scanning electron microscope. X-ray diffraction and Rietveld refinement were performed to evaluate the amount of tetragonal and cubic phases of zirconia. Contrast ratio (CR) was measured to investigate the level of translucency. RESULTS PA had the lowest fracture toughness among other groups ( P < .05). In addition, the mean fracture toughness of P was significantly less than that of ZI, but there was no difference compared with TZI. Regarding grain size measurement, PA had the largest average grain size among the groups. P obtained larger grain size than ZI and TZI ( P < .05). However, there was no significant difference between ZI and TZI. Moreover, PA had the lowest CR value compared with the other groups ( P < .05). This means PA was the most translucent material in this study. Rietveld refinement found that PA presented the greatest percentage of cubic phase, followed by TZI, ZI, and P, respectively. CONCLUSION The different approaches are used by manufacturers to fabricate various types of translucent zirconia with different levels of translucency and mechanical properties, which should be concerned for material selection for successful clinical outcome.

The purpose of this study was to evaluate anti-candidal activity, gelation time, and surface hardness of a short-term soft lining material incorporated with varying concentrations of Piper betle extract (0.25 to 20% w/w). Agar-diffusion assay was conducted to evaluate an inhibitory effect against Candida albicans. The gelation time was assessed and surface hardness was measured at 2 h and 7 days by Shore AO durometer. A soft liner containing at least 5% w/w of P. betle extract was observed the inhibitory effect against C. albicans. An increasing of P. betle concentrations provided larger inhibition zone. Incorporating 5% w/w of P. betle extract into the soft liner did not significantly alter its gelation time and surface hardness (ANOVA; p>0.05). The optimum composition at 5% w/w of P. betle extract can be used as an additive in the soft liner to provide the anti-candidal activity without significantly affect these two main properties.