Resin-based dental materials containing 3-aminopropyltriethoxysilane modified halloysite-clay nanotubes for extended drug delivery.

OBJECTIVE: To synthesize and characterize a novel resin-based dental material containing 3-aminopropyltriethoxysilane (APTES) surface-modified halloysite-clay nanotubes (HNTs) for long-term delivery of guest molecules. METHODS: The optimal concentrations of HNT (10, 15, 20 wt.%) and silane (0, 2, 4 vol.%sil) to be incorporated into the resin-based materials were determined (15 wt.%HNT, 4 vol.%sil) after assessment of the mechanical properties (DC%, degree of conversion; FS, flexural strength; FM, flexural modulus; and UTS, ultimate tensile strength). The HNTsil-powder was loaded with chlorhexidine (CHX) to evaluate the effect of the silanization on drug release. Resin-discs were prepared for the following groups: RES (resin), HNT (resin+15 wt.%HNT), HNTsil (resin+15 wt.%HNT silanized), HNT-CHX (resin+15 wt.%HNT loaded with chlorhexidine), HNTsil-CHX (resin+15 wt.%HNTsil-CHX), and 0.2 vol.%CHX (resin+0.2 vol.%CHX solution). Specimens were stored in water for 1, 3, 5, 10, and 15 days at 37 °C. Aliquots from each time point and the final 15-day specimens were evaluated for the zone of inhibition (ZOI) against Streptococcus mutans. CHX release was analyzed using spectrophotometry at absorbance of 300 nm. Data were statistically analyzed (α = 0.05). RESULTS: All materials presented similar DC%. Reduced FS but increased FM was detected for 20 wt.%HNT-4%APTES. Groups with 15 wt.% and 20 wt.%HNT with/without APTES presented higher values of UTS. Agar diffusion data indicates that the HNTsil-CHX had a greater ZOI than all other groups over 15 days. HNTsil-CHX had the highest absorbance for day 1 but presented similar values to other groups every time point after. SIGNIFICANCE: Silanization of nanotubes followed by encapsulation of chlorhexidine is a promising technique for long-term delivery of guest molecules.

The Use of Bulk-Fill Flow in the Customization of Glass Fiber Post.

OBJECTIVES: The aim of this study is to evaluate the influence of different composite resin in the customization of glass fiber posts (GFPs) on bond strength and failure mode. MATERIALS AND METHODS: Thirty bovine roots were selected. The wall roots were reduced so that each wall had a minimum dentin thickness of 1 mm. Thirty GFPs were divided into three groups (n = 10), which received different types of customization. The first had the GFP relined by bulk-fill flowable composite resin (BF), the second group had the GFP customized by conventional regular composite resin (CR), and the third group was cemented with dual resin cements (DRC), without relining. The root were sectioned, resulting in two 1.0-mm thick slices from cervical root regions only and push-out bond strength test was performed (EMIC, Universal testing machine). To determine failure mode, a stereomicroscope was used at ×40 magnification, with a 2.5D analysis. STATISTICAL ANALYSIS: Data were analyzed using two-way ANOVA (α = 0.05) and Tukey's test. RESULTS: BF (9.08 ± 1.9) and CR (9.17 ± 3.00) did not show a statistically significant difference (p = 0.961), regarding the bond strength test values. However, there was a statistically significant difference between DRC (5.44 ± 1.89) and the others (p < 0.05). BF (66.66%) and the CR group (47.61%) presented a predominantly failure mode type 6: mixed between resin cement and composite. While the highest failure index of the DRC group was type 2: adhesive between resin cement and dentin (47.61%). CONCLUSION: BF can be an alternative for the customization of fiber posts, since it presented a similar behavior to the established technique with conventional composites.