Influence of calcium hydroxide dressing and acid etching on the push-out bond strengths of three luting resins to root canal dentin.

OBJECTIVES: This study aims to investigate the effects of calcium hydroxide (Ca(OH)2) dressing in root canals and the effects of subsequent acid etching on the adhesion of luting resins to root canals. MATERIALS AND METHODS: Root specimens were prepared from extracted human permanent molars. Specimen canals were (1) filled with etch-and-rinse (Nexus® third generation (NX3)) and two self-adhesive (RelyX Unicem, Maxcem Elite) luting resins, respectively; (2) dressed with Ca(OH)2 before Ca(OH)2 removal and luting resin filling; (3) dressed with Ca(OH)2 before Ca(OH)2 removal and post-cementation; or (4) treated as described in item (2) except that the canals were further etched with phosphoric acid before luting resin filling. Push-out bond strengths were measured and analyzed using one-way analysis of variance, and Fisher's multiple comparison tests provided a follow-up comparison among these four canal treatments. Attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were used to analyze the specimen surfaces. RESULTS: Ca(OH)2 dressing adversely affected the bond strengths to canal dentin of the three luting resins tested. Acid etching did not increase the bond strengths. Infrared analysis revealed that Ca(OH)2 dressing caused no structural changes on the dentin surface. XPS and SEM analyses revealed Ca(OH)2 remnants as the ultimate chemical cause leading to the decrease in bond strength. CONCLUSIONS: The bond strength of luting resin to dentin was affected by Ca(OH)2 dressing. Acid etching treatment could not increase the bond strength. CLINICAL RELEVANCE: Adhesion of the fiber post to the root canal wall may be compromised after Ca(OH)2 dressing. An effective method for complete removal of Ca(OH)2 dressing or increase of bond strength for luting resin needs to be developed.

LC-NeRF: Local Controllable Face Generation in Neural Radiance Field.

3D face generation has achieved high visual quality and 3D consistency thanks to the development of neural radiance fields (NeRF). However, these methods model the whole face as a neural radiance field, which limits the controllability of the local regions. In other words, previous methods struggle to independently control local regions, such as the mouth, nose, and hair. To improve local controllability in NeRF-based face generation, we propose LC-NeRF, which is composed of a Local Region Generators Module (LRGM) and a Spatial-Aware Fusion Module (SAFM), allowing for geometry and texture control of local facial regions. The LRGM models different facial regions as independent neural radiance fields and the SAFM is responsible for merging multiple independent neural radiance fields into a complete representation. Finally, LC-NeRF enables the modification of the latent code associated with each individual generator, thereby allowing precise control over the corresponding local region. Qualitative and quantitative evaluations show that our method provides better local controllability than state-of-the-art 3D-aware face generation methods. A perception study reveals that our method outperforms existing state-of-the-art methods in terms of image quality, face consistency, and editing effects. Furthermore, our method exhibits favorable performance in downstream tasks, including real image editing and text-driven facial image editing.

Prevention of enamel demineralization with a novel fluoride strip: enamel surface composition and depth profile.

There is no topically applicable low concentration fluoride delivery device available for caries prevention. This study was aimed to assess the use of a low concentration (1450 ppm) fluoride strip as an effective fluoride delivery system against enamel demineralization. The enamel surface composition and calcium-deficient hydroxyapatite or toothpaste treatments were investigated using X-ray photoelectron spectroscopy. In vitro enamel demineralization was assayed using a pH cycling model and the dissolution of calcium ions from the treated specimens was quantified using ion chromatography. After 24-hr fluoride-strip treatment, the enamel was covered with a CaF2 layer which showed a granular morphology of 1 µm in size. Below the CaF2 layer was a region of mixed fluorapatite and CaF2. Fluoride infiltrated extensively in enamel to produce highly fluorinated fluorohydroxyapatite. In comparison, low-fluoride-level fluorinated fluorohydroxyapatite was formed on the enamel specimen exposed to toothpaste. The treatments with the fluoride strip as short as 1 hr significantly inhibited enamel demineralization. The fluoride strip was effective for topical fluoride delivery and inhibited in vitro demineralization of enamel by forming CaF2 and fluoride-containing apatites at the enamel surface. It exhibited the potential as an effective fluoride delivery device for general use in prevention of caries.