Hydroxypropylmethylcellulose as a film and hydrogel carrier for ACP nanoprecursors to deliver biomimetic mineralization.

Demineralization of hard tooth tissues leads to dental caries, which cause health problems and economic burdens throughout the world. A biomimetic mineralization strategy is expected to reverse early dental caries. Commercially available anti-carious mineralizing products lead to inconclusive clinical results because they cannot continuously replenish the required calcium and phosphate resources. Herein, we prepared a mineralizing film consisting of hydroxypropylmethylcellulose (HPMC) and polyaspartic acid-stabilized amorphous calcium phosphate (PAsp-ACP) nanoparticles. HPMC which contains multiple hydroxyl groups is a film-forming material that can be desiccated to form a dry film. In a moist environment, this film gradually changes into a gel. HPMC was used as the carrier of PAsp-ACP nanoparticles to deliver biomimetic mineralization. Our results indicated that the hydroxyl and methoxyl groups of HPMC could assist the stability of PAsp-ACP nanoparticles and maintain their biomimetic mineralization activity. The results further demonstrated that the bioinspired mineralizing film induced the early mineralization of demineralized dentin after 24 h with increasing mineralization of the whole demineralized dentin (3-4 µm) after 72-96 h. Furthermore, these results were achieved without any cytotoxicity or mucosa irritation. Therefore, this mineralizing film shows promise for use in preventive dentistry due to its efficient mineralization capability.

Effects of regional enamel and prism orientations on bovine enamel bond strength and cohesive strength.

This study investigated the regional microtensile bond strength (MTBS) and cohesive strength of bovine enamel. The crowns of bovine incisors were sectioned, either horizontally along incisal and cervical thirds to produce horizontal and tangential segments, or longitudinally along the midline to produce longitudinal segments. Half of the horizontal and longitudinal segments were prepared using a 45° bevel. Then, the differently sectioned enamel surfaces were treated with one- or two-step self-etch adhesives (Clearfil SE Bond or Clearfil S3 Bond) and a composite resin (Clearfil Majesty) was placed. Resin-bonded enamel samples were cut into beams for use in the MTBS tests. Labial horizontal and longitudinal segments of pure enamel beams were prepared for cohesive strength tests. Enamel microstructures were analyzed by scanning electron microscopy. Three-way anova followed by Tukey's post-hoc HSD multiple comparisons procedure showed that a 45° bevel cut did not statistically significantly improve enamel MTBS, which varied with the different regions. The longitudinally sectioned resin-bonded enamel samples had the lowest MTBS, and the horizontal enamel cohesive strength was weaker than that of the longitudinal enamel. The scanning electron microscopy fractographs indicated that rows of parallel prisms were detached from the fractured surfaces. In conclusion, the regional enamel MTBS and the cohesive strength are strongly related to the enamel microstructures and prism orientations.

Onlays/partial crowns versus full crowns in restoring posterior teeth: a systematic review and meta-analysis.

BACKGROUND: Tooth-colored onlays and partial crowns for posterior teeth have been used increasingly in clinics. However, whether onlays/partial crowns could perform as well as full crowns in the posterior region was still not evaluated thoroughly. METHODS: A literature search was conducted without language restrictions in Pubmed, Embase, Cochrane Central Register of Controlled Trial and Web of science until September 2021. RCTs, prospective and retrospective observational studies with a mean follow-up of 1 year were selected. Cochrane Collaboration's tool was adopted for quality assessment of the RCT. The quality of observational studies was evaluated following Newcastle-Ottawa scale. The random-effects and fixed-effects model were employed for meta-analysis. RESULTS: Four thousand two hundred fifty-seven articles were initially searched. Finally, one RCT was identified for quality assessment and five observational studies for qualitative synthesis and meta-analysis. The RCT was of unclear risk of bias while five observational studies were evaluated as low risk. The meta-analysis indicated no statistically significant difference in the survival between onlays/partial crowns and full crowns after 1 year (OR = 0.55, 95% CI: 0.02-18.08; I2 = 57.0%; P = 0.127) and 3 years (OR = 0.65, 95% CI: 0.20-2.17; I2 = 0.0%; P = 0.747). For the success, onlays/partial crowns performed as well as crowns (OR = 0.58, 95% CI: 0.20-1.72; I2 = 0.0%; P = 0.881) at 3 years. No significant difference of crown fracture existed between the two methods (RD = 0.00, 95% CI: - 0.03-0.03; I2 = 0.0%; P = 0.972). CONCLUSIONS: Tooth-colored onlays/partial crowns performed as excellently as full crowns in posterior region in a short-term period. The conclusions should be further consolidated by RCTs with long-term follow-up.

Structural characteristics of humic-like acid from microbial utilization of lignin involving different mineral types.

This paper determines the impact of two clay minerals (kaolinite and montmorillonite) and three oxides (goethite, δ-MnO2, and bayerite) on the elemental composition and FTIR spectra of humic-like acid (HLA) extracted from microbial-mineral residue formed from the microbial utilization of lignin in liquid shake flask cultivation. Goethite, bayerite, and δ-MnO2 showed higher enrichment capabilities of C and O + S in the HLA than kaolinite and montmorillonite. Goethite showed the highest retention of organic C, followed by bayerite, but kaolinite exhibited the least exchangeability. Kaolinite and montmorillonite enhanced microbial consumption of N, resulting in the absence of N in HLA. A few aliphatic fractions were preferentially gathered on the surfaces of kaolinite and montmorillonite, making the H/C ratios of HLA from the clay mineral treatments higher than those of HLA from the oxide treatments. δ-MnO2 was considered the most effective catalyst for abiotic humification, and goethite and bayerite ranked second and third in this regard. This trend was proportional to their specific surface areas (SSAs). However, comparing the effects of different treatments on the promotion of HLA condensation by relying solely on the SSA of minerals was not sufficient, and other influencing mechanisms had to be considered as well. Additionally, Si-O-Al and Si-O of kaolinite participated in HLA formation, and Si-OH, Si-O, and Si-O-Al of montmorillonite also contributed to this biological process. Fe-O and phenolic -OH of goethite, Mn-O of δ-MnO2, and Al-O of bayerite were all involved in HLA formation through ligand exchange and cation bridges. Lignin was better protected from microbial decomposition by the kaolinite, bayerite, and δ-MnO2 treatments, which caused lignin-like humus (HS) formation. Under the treatments of δ-MnO2, goethite, and bayerite, HLA showed a greater degree of condensation compared to HLA precipitated by kaolinite and montmorillonite. Contributions from Si-O, and Si-O-Al of clay minerals, and Fe-O, Mn-O, and Al-O of oxides were the mechanisms by which minerals catalyzed the formation of HS from lignin.

A novel fluorescent adhesive-assisted biomimetic mineralization.

We propose a novel fluorescent adhesive-assisted biomimetic mineralization strategy, based on which 1 wt% of sodium fluorescein and 25 wt% of polyacrylic acid stabilized amorphous calcium phosphate (PAA-ACP) nanoparticles were incorporated into a mild self-etch adhesive (Clearfil S3 Bond) as a fluorescent mineralizing adhesive. The characterization of the PAA-ACP nanoparticles indicates that they were spherical particles clustered together, each particle with a diameter of approximately 20-50 nm, in a metastable phase with two characteristic absorption peaks (1050 cm-1 and 580 cm-1). Our results suggest that the fluorescent mineralizing adhesive was non-cytotoxic with minimal esthetic interference and its fluorescence intensity did not significantly decrease within 6 months. Our data reveal that the fluorescent mineralizing adhesive could induce the extra- and intra-fibrillar remineralization of the reconstituted type I collagen, the demineralized enamel and dentin substrate. Our data demonstrate that a novel fluorescent adhesive-assisted biomimetic mineralization strategy will pave the way to design and produce anti-carious materials for the prevention of dental caries.