Fluoride-treated rare earth-free magnesium alloy ZK30: An inert and bioresorbable material for bone fracture treatment devices.

Bone fractures represent a common health problem, particularly in an increasingly aging population. Bioresorbable magnesium (Mg) alloy-based implants offer promising alternatives to traditional metallic implants for the treatment of bone fractures because they eliminate the need for implant removal after healing. The Mg-Y-rare-earth (RE)-Zr alloy WE43, designed for orthopedic implants, has received European Conformity mark approval. However, currently, WE43 is not clinically used in certain countries possibly because of concerns related to RE metals. In this study, we investigated the use of a RE-free alloy, namely, Mg-Zn-Zr alloy (ZK30), as an implant for bone fractures. Hydrofluoric acid (HF) treatment was performed to improve the corrosion resistance of ZK30. HF-treated ZK30 (HF-ZK30) exhibited lower corrosion rate and higher biocompatibility than those of WE43 in in vitro experiments. After implanting a rod of HF-ZK30 into the fractured femoral bones of mice, HF-ZK30 held the bones and healed the fracture without deformation. Treatment results of HF-ZK30 were comparable to those of WE43, indicating the potential of HF-ZK30 as a bioresorbable and safe implant for bone repair.

A national sample of developmentally disabled adolescents with obesity and their utilization of preventive dental care services.

Background: Previous literature indicates that adolescents with developmental disabilities and obesity may have more oral health complications than healthy adolescents. However, dental care utilization among adolescents with developmental disabilities (DDs) and obesity is unclear. We investigated the differences in the utilization of preventive dental services between this high-risk group of adolescents and those with no DDs or obesity. Methods: Parent-reported data of adolescents 10-17 years (n = 68,942) from the 2016 to 2019 National Survey of Children's Health was used. In addition to descriptive and bivariate statistics, we ran three multiple logistic regression models guided by Andersen's Behavioral Model of Health Services Use, predicting the use of dental cleanings, fluoride treatments, and dental sealants. Results: Among adolescents with DDs and obesity, dental cleanings, fluoride treatments, and dental sealant utilization prevalence were 76%, 48%, and 21%, respectively. In comparison, adolescents with no DDs or obesity had a prevalence of 83%, 50%, and 19%, respectively. Multiple logistic regression analysis showed that adolescents with DDs and obesity did not significantly differ in their receipt of dental cleanings (p = .07), fluoride treatments (p = .55), and dental sealants (p = .23) compared to those with neither DDs nor obesity. Adolescents with DDs but no obesity were 22% and 30% more likely to receive fluoride treatments (p < .0001) and dental sealants (p < .0001), respectively. Conclusions: Fewer than half of adolescents with DDs and obesity utilized fluoride treatments, and less than one quarter utilized dental sealants but used all three preventive services at the same rate as those with no DDs or obesity. Implications: This study identified no differences in preventive dental care services utilization in adolescents with developmental disabilities (DDs) and obesity compared to those without DDs and obesity. However, the utilization of preventive dental services in this population is influenced by the federal poverty level and family background.

Antibacterial Efficacy of Silver Diamine Fluoride Compared to Casein Phosphopeptide-Amorphous Calcium Phosphate Against Streptococcus mutans in a Biofilm Caries Model

ABSTRACT Objective: To compare the antibacterial efficacy of silver diamine fluoride (SDF) with a product containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) against Streptococcus mutans using a biofilm caries model. Material and Methods: Twenty-seven saliva-coated dentine blocks obtained from extracted human teeth were inoculated with Streptococcus mutans monospecies biofilm in this in vitro study. The biofilms were then exposed to 10% sucrose in brain heart infusion broth eight times daily for seven days. After the biofilm growth period, the dentine blocks (n=9 per group) were treated with one of the following substances: 1) sterile saline (control), 2) 38% SDF, and 3) a product containing CPP-ACP. Then, the samples were incubated at 37ºC for 48 hours, and the numbers of viable microorganisms in the biofilms were counted and compared. ANOVA and Tukey's HSD tests were used to analyze the data (p<0.05). Results: The number of viable bacteria, as determined by the number of colony-forming units (CFU mL-1) of Streptococcus mutans, was significantly reduced following treatment with SDF and the CPP-ACP product (p<0.05). However, SDF showed superior antibacterial activity compared to the CPP-ACP product (mean CFU mL-1 =zero compared to 96 x106) (p<0.05). Conclusion: SDF has higher antibacterial activity against cariogenic Streptococcus mutans biofilm than the CPP-ACP product. The CPP-ACP product showed antibacterial activity, but it was limited.

Fluoride Treatment and In Vitro Corrosion Behavior of Mg-Nd-Y-Zn-Zr Alloys Type.

Fluoride conversion coatings on Mg present many advantages, among which one can find the reduction of the corrosion rate under "in vivo" or "in vitro" conditions and the promotion of the calcium phosphate deposition. Moreover, the fluoride ions released from MgF2 do not present cytotoxic effects and inhibit the biofilm formation, and thus these treated alloys are very suitable for cardiovascular stents and biodegradable orthopedic implants. In this paper, the biodegradation behavior of four new magnesium biodegradable alloys that have been developed in the laboratory conditions, before and after surface modifications by fluoride conversion (and sandblasting) coatings, are analyzed. We performed structural and surface analysis (XRD, SEM, contact angle) before and after applying different surface treatments. Furthermore, we studied the electrochemical behavior and biodegradation of all experimental samples after immersion test performed in NaCl solution. For a better evaluation, we also used LM and SEM for evaluation of the corroded samples after immersion test. The results showed an improved corrosion resistance for HF treated alloy in the NaCl solution. The chemical composition, uniformity, thickness and stability of the layers generated on the surface of the alloys significantly influence their corrosion behavior. Our study reveals that HF treatment is a beneficial way to improve the biofunctional properties required for the studied magnesium alloys to be used as biomaterials for manufacturing the orthopedic implants.

In Vitro and in Vivo Studies on Two-Step Alkali-Fluoride-Treated Mg-Zn-Y-Nd Alloy for Vascular Stent Application: Enhancement in Corrosion Resistance and Biocompatibility.

Bioabsorbable magnesium alloys are becoming prominent materials for cardiovascular stents, as their desirable mechanical properties and favorable biosafety. However, the rapid corrosion of magnesium alloys under physiological conditions hinders their wider application as medical implant materials. Fluoride chemical conversion treatment is an effective and simple technique to improve the corrosion resistance for magnesium alloys. Despite previous literature reporting on fluoride chemical conversion treatment with hydrofluoric acid (HF) in different conditions, some defects are still present on the surface of the coating. In this study, we report on a two-step alkali-fluoride treatment of magnesium alloy by effectively removing the second phase in the substrate surface and form a dense and flawless magnesium fluoride (MgF2) coating to endow the magnesium alloy greater corrosion resistance. The results showed that the serious pitting corrosion caused by galvanic corrosion could be effectively prevented after removing of the second phase of the surface. In vivo tests in a rat subcutaneous implantation model showed that two-step alkali-fluoride-treated MgZnYNd alloy (MgZnYNd-A-F) uniformly corroded with a low corrosion rate. No subcutaneous gas cavities or significant inflammatory cell infiltration were observed for MgZnYNd-A-F in in vivo tests. The two-step alkali-fluoride treatment can significantly improve the corrosion resistance and biocompatibility of magnesium alloy, which has great potential in the application of vascular stents because of its simplicity and effectiveness.

Oral Hygiene Index in Early Childhood Caries, Before and After Topical Fluoride Treatment.

BACKGROUND: Circular caries occurs in the earliest age of the children (1 - 1.5 year), immediately after the eruption of the deciduous teeth. During this period, children are too young to be able to properly implement oral hygiene. Consequently, it is at a negligible level, with plenty of soft plaque on the deciduous tooth surfaces. OBJECTIVE: The main objective of this clinical trial was to determine the correlation between oral hygiene shown with Oral Hygiene index, and the initial stages of circular caries (initial lesion and superficial form), before and after topical fluoride treatment. MATERIAL AND METHODS: For determination of the OHI - index we used the method of Green - Vermillion. It was determined two times in 117 patients, during the first visit and immediately before physiological replacement of deciduous teeth. Patients were two to three years old and diagnosed with initial stages of circular caries. Amino fluoride solution was applied once a week, during six months. RESULTS: We obtained statistically significant improvement of OHI - index at the end of the test, among treated subjects from both major groups. CONCLUSION: It can be concluded that the level of oral hygiene is correlated with the progression of changes in enamel. Topical fluoride treatment has a positive impact on reducing ECC.