Stem-cell-based tissue engineering of murine teeth

Teeth develop from reciprocal interactions between mesenchyme cells and epithelium, where the epithelium provides the instructive information for initiation. Based on these initial tissue interactions, we have replaced the mesenchyme cells with mesenchyme created by aggregation of cultured non-dental stem cells in mice. Recombinations between non-dental cell-derived mesenchyme and embryonic oral epithelium stimulate an odontogenic response in the stem cells. Embryonic stem cells, neural stem cells, and adult bone-marrow-derived cells all responded by expressing odontogenic genes. Transfer of recombinations into adult renal capsules resulted in the development of tooth structures and associated bone. Moreover, transfer of embryonic tooth primordia into the adult jaw resulted in development of tooth structures, showing that an embryonic primordium can develop in its adult environment. These results thus provide a significant advance toward the creation of artificial embryonic tooth primordia from cultured cells that can be used to replace missing teeth following transplantation into the adult mouth.     

Effects of filler size, water, and alcohol on hardness and laboratory wear of dental composites

Three UEDMA/TEGDMA (50:50 by weight) based dental composites were made, each with filler loadings of 53 vol.%. The three composites contained silane-treated filler particles with average particle diameters of 1.5, 3.0, or 10.0 microm. Twelve specimens per composite were mounted on wear wheels and run through 200,000 cycles in an ACTA wear machine. Six of these specimens per material were worn in slurries consisting of 30 g ground Millet seed shells and 120 g ground rice mixed with 275 mL water. The remaining six specimens were worn in similar 25% ethanol-water slurries. The composite wear profiles were recorded with a profilometer and used to calculate the wear. Hardness values of the composites were also measured both before and after storage for 2 weeks in either water or in a 25% ethanol water solution. The wear and hardness values from the measurements were analyzed using ANOVA. The wear analysis showed that the finer composites (1.5 microm filler diameter) wore the least and the coarsest composites (10 microm filler diameter) the most. The wear was significantly higher in the ethanol water slurry than in the water slurry. The hardness value of the coarsest composite decreased more than the finest composite during storage in water or 25% ethanol water. The hardness decrease was most pronounced in the alcohol solution.     

The clinical comparison of a triclosan/copolymer/fluoride dentifrice vs a breath-freshening dentifrice in reducing breath odor overnight: a crossover study

Objective: The objective of this randomized, crossover study was to compare the effectiveness of the triclosan/copolymer/sodium fluoride (TCF‐AF) dentifrice and a commercially available breath‐freshening dentifrice containing fluoride for their ability to reduce volatile sulfur compounds (VSC) associated with oral malodor overnight. Methods: Following a 1‐week washout period of brushing with a regular fluoride dentifrice, subjects reported to the clinical site without performing oral hygiene, eating or drinking in preparation for baseline breath sampling. Subjects were randomly assigned a test dentifrice and instructed to brush their teeth for 1 min, twice a day for 1 week. On the morning of day 8, subjects returned to the test site, having refrained from oral hygiene, eating and drinking, for overnight sampling. Following a second 1‐week washout period, subjects repeated the same regimen, but now using the other test product. At each measurement, the level of breath VSC was evaluated using a gas chromatograph equipped with a flame photometric detector. Measurements were taken in duplicate, and then averaged. The levels of VSC were expressed as parts per billion (ppb) in mouth air. Results: At baseline, the mean breath VSC levels for the TCF‐AF and breath‐freshening dentifrice were 618 and 581 ppb respectively. There was no statistically significant difference between the baseline levels. Overnight, the TCF‐AF and the breath‐freshening dentifrice reduced breath mean VSC levels to 267 and 521 ppb respectively. This gave a 56.7 and 10.2% reduction in VSC levels for these two products, respectively, compared with baseline. The reduction for the TCF‐AF dentifrice was significantly different (P < 0.05%) from that of the breath‐freshening dentifrice. Conclusion: The results of this randomized, double‐blind, crossover study indicate that the TCF‐AF dentifrice was significantly more effective than a commercially available breath‐freshening dentifrice containing fluoride in reducing breath VSC associated with bad breath overnight.     

Hybrid nickel hexacyanoferrate/polypyrrole composite as mediator for hydrogen peroxide detection and its application in oxidase-based biosensors

The synthesis and electrochemical characterization of a new organic/inorganic hybrid material was performed by combining polypyrrole and a hexacyano metalate (nickel hexacyanoferrate (NiHCNFe)) aiming to obtain an electrocatalyst for H₂O₂ reduction in the presence of either Na⁺ or K⁺ ions. The use of this material as a redox mediator in an oxalate biosensor based on the immobilization of oxalate oxidase enzyme was also discussed. The electrochemical properties of the hybrid material were investigated by using impedance measurements and compared with those of the nickel hexacyanoferrate film alone. The electrocatalytic properties of the hybrid for reducing H₂O₂, in the presence of both Na⁺ and K⁺ ions, are higher than those of the NiHCNFe film due to the presence of polypyrrole chains that enhances the electronic conductivity of the material.     

Amelogenesis imperfecta in a new animal model--a mutation in chromosome 5 (human 4q21)

Candidate genes for amelogenesis imperfecta (AI) and dentinogenesis imperfecta (DI) are located on 4q21 in humans. We tested our hypothesis that mutations in the portion of mouse chromosome 5 corresponding to human chromosome 4q21 would cause enamel and dentin abnormalities. Male C3H mice were injected with ethylnitrosourea (ENU). Within a dominant ENU mutagenesis screen, a mouse mutant was isolated with an abnormal tooth enamel (ATE) phenotype. The structure and ultrastructure of teeth were studied. The mutation was located on mouse chromosome 5 in an interval of 9 cM between markers D5Mit18 and D5Mit10. Homozygotic mutants showed total enamel aplasia with exposed dentinal tubules, while heterozygotic mutants showed a significant reduction in enamel width. Dentin of mutant mice showed a reduced content of mature collagen cross-links. We were able to demonstrate that a mutation on chromosome 5 corresponding to human chromosome 4q21 can cause amelogenesis imperfecta and changes in dentin composition.     

Efficacy of A-dec's ICX dental unit waterline treatment solution in the prevention and treatment of microbial contamination in dental units

OBJECTIVE: Even though some chemical agents can disinfect biofilms in dental unit waterlines, there remains concern that all remnants of the biofilm matrix are not eliminated. Even with periodic treatments, the bacterial populations in dental unit waterlines recur rapidly. In addition, with some previously tested products, patient safety, as well as toxic, caustic and corrosive residual chemicals are also a concern. This study evaluated ICX, A-dec's new water treatment solution, in a series of experiments for prevention, microbial spectrum of activity, minimum inhibitory time determination, and treatment of established biofilms. METHODOLOGY: New dental unit waterline tubing was treated continuously during simulated patient care over 28 days with municipal water. It was then treated with ICX. Effluents from lines with established biofilms (averaging > 10(4) CFU/ml at day 0) were treated to assess levels of CFU counts within 21 days of exposure to ICX. RESULTS: Tubing treated with ICX did not develop a detectable biofilm using ruthenium red staining, and microbes in effluents remained undetectable. CONCLUSION: ICX is effective in maintaining the effluent within the American Dental Association's and the Centers for Disease Control's recommendation for < 500 CFU/ml. In addition, considering the preliminary finding that ICX reduces microbial contamination of effluents from established biofilm lines, it may be useful in long-term treatment alone or when coupled with a shock treatment to assist in biofilm destruction.     

Periodontal disease in patients with familial Mediterranean fever: from inflammation to amyloidosis

Background and Objective:  Familial Mediterranean fever stimulates a very intense acute-phase reactants response and if left untreated eventually leads to amyloidosis. The aim of this study was to determine the prevalence of periodontal disease among patients with familial Mediterranean fever in the Black Sea region in Turkey and to evaluate whether periodontitis is related to amyloidosis in patients with familial Mediterranean fever.
Material and Methods:  One-hundred and thirty three patients with familial Mediterranean fever and 50 healthy subjects were included in this study. Periodontal health and disease were evaluated using the gingival index, papillary bleeding index, plaque index and periodontal disease index. The concentrations of serum acute-phase reactants were measured at baseline and at 4–6 wk after completion of the nonsurgical periodontal therapy. Genetic testing for familial Mediterranean fever was performed using the familial Mediterranean fever StripAssay. Kidney biopsy was carried out on all proteinuric patients.
Results:  The prevalence of moderate to severe periodontitis in familial Mediterranean fever patients with amyloidosis (80.6%) was significantly greater ( p  < 0.01) than in familial Mediterranean fever patients without amyloidosis (38%) and in controls (20%). Serum levels of acute-phase reactants in familial Mediterranean fever patients were reduced significantly following nonsurgical periodontal therapy ( p  < 0.01).
Conclusion:  Periodontal therapy seems to reduce the serum levels of acute-phase reactants in patients with familial Mediterranean fever. Therefore, treating periodontitis might help to alleviate the disease burden in patients with familial Mediterranean fever.