Libang He

The effects of light on bleaching and tooth sensitivity during in-office vital bleaching: a systematic review and meta-analysis.

OBJECTIVE To evaluate the influence of light on bleaching efficacy and tooth sensitivity during in-office vital bleaching. DATA SOURCES We performed a literature search using Medline, EMBASE and Cochrane Central up to September 2011. STUDY SELECTION All randomised controlled trials (RCTs) or quasi-RCTs comparing the light-activated bleaching system with non-activation bleaching system were included. Reports without clinical data concerning bleaching efficacy or tooth sensitivity were excluded. RESULTS Eleven studies were included in the meta-analysis. A light-activated system produced better immediate bleaching effects than a non-light system when lower concentrations of hydrogen peroxide (15-20% HP) were used (mean difference [MD], -1.78; 95% confidence interval [CI]: [-2.30, -1.26]; P<0.00001). When high concentrations of HP (25-35%) were employed, there was no difference in the immediate bleaching effect (MD, -0.39; 95% CI: [-1.15, 0.37]; P=0.32) or short-term bleaching effect (MD, 0.25; 95% CI: [-0.47, 0.96]; P=0.50) between the light-activated system and the non-light system. However, the light-activated system produced a higher percentage of tooth sensitivity (odds ratio [OR], 3.53; 95% CI: [1.37, 9.10]; P=0.009) than the non-light system during in-office bleaching. CONCLUSIONS Light increases the risk of tooth sensitivity during in-office bleaching, and light may not improve the bleaching effect when high concentrations of HP (25-35%) are employed. Therefore, dentists should use the light-activated system with great caution or avoid its use altogether. Further rigorous studies are, however, needed to explore the advantages of this light-activated system when lower concentrations of HP (15-20%) are used.

Effective dentin restorative material based on phosphate-terminated dendrimer as artificial protein

In clinic, it calls for effective and simple materials to repair etched dentin. Bioinspired by the natural mineralization process guided by noncollagenous proteins (NCPs), in this work, we synthesized the fourth generation phosphate-terminated polyamidoamine dendrimer (G4-PO3H2) by one-step modification. We used FT-IR and 1H NMR to characterize the structure of G4-PO3H2, and MTT assay to prove its biocompatibility. It was applied as the analog of dentin phosphophoryn (DPP: a type of NCPs) to repair dentin, due to its similar dimensional scale, topological architecture and peripheral functionalities to that of DPP. By the characterization of SEM and XRD, the effective regeneration of human dentin induced by G4-PO3H2 is characterized and illustrated both in vitro (artificial saliva) and in vivo (oral cavity of rats). It is noted that the thickness of the regenerated mineral layers are more than 10 μm both in vitro and in vivo. The design strategy of G4-PO3H2 may be valuable for researchers in the fields of material science, stomatology and medicine to prepare various promising restorative nano-materials for biomineralized hard tissues such as bone and teeth.

Modulated regeneration of acid-etched human tooth enamel by a functionalized dendrimer that is an analog of amelogenin

In the bioinspired repair process of tooth enamel, it is important to simultaneously mimic the organic-matrix-induced biomineralization and increase the binding strength at the remineralization interface. In this work, a fourth-generation polyamidoamine dendrimer (PAMAM) is modified by dimethyl phosphate to obtain phosphate-terminated dendrimer (PAMAM-PO3H2) since it has a similar dimensional scale and peripheral functionalities to that of amelogenin, which plays important role in the natural development process of enamel. Its phosphate group has stronger affinity for calcium ion than carboxyl group and can simultaneously provide strong hydroxyapatite (HA)-binding capability. The MTT assay demonstrates the low cytotoxicity of PAMAM-PO3H2. Adsorption tests indicate that PAMAM-PO3H2 can be tightly adsorbed on the human tooth enamel. Scanning electron microscopy and X-ray diffraction are used to analyze the remineralization process. After being incubated in artificial saliva for 3weeks, there is a newly generated HA layer of 11.23μm thickness on the acid-etched tooth enamel treated by PAMAM-PO3H2, while the thickness for the carboxyl-terminated one (PAMAM-COOH) is only 6.02μm. PAMAM-PO3H2 can regulate the remineralization process to form ordered new crystals oriented along the Z-axis and produce an enamel prism-like structure that is similar to that of natural tooth enamel. The animal experiment also demonstrates that PAMAM-PO3H2 can induce significant HA regeneration in the oral cavity of rats. Thus PAMAM-PO3H2 shows great potential as a biomimetic restorative material for human tooth enamel.

Effective dentinal tubule occlusion induced by polyhydroxy-terminated PAMAM dendrimer in vitro

In recent years, poly (amido amine) (PAMAM) dendrimers have become a research focus in biomineralization fields. In this study, polyhydroxy-terminated PAMAM dendrimers (PAMAM-OH) were used to induce dentinal tubule occlusion. Demineralized dentin samples were coated with the second generation or the fourth generation PAMAM-OH solutions (G2-PAMAM-OH or G4-PAMAM-OH, 1 mg mL−1). The binding capacity of PAMAM-OH to demineralize dentin was tested by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Then the G4-PAMAM-OH-treated samples were immersed in artificial saliva for different periods. The remineralized samples were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). 6 wt% citric acid (pH 1.5) solutions were used to evaluate the effect of dentinal tubule occlusion. Cytotoxicity assay on dental pulp cells was carried out to examine the biocompatibility of G4-PAMAM-OH. The results of ATR-FTIR showed that G4-PAMAM-OH had a stronger binding capacity towards demineralized dentin than G2-PAMAM-OH did. After the remineralization, the G4-PAMAM-OH-treated samples showed obvious remineralization compared to the control group and the dentinal tubule occlusion was effective even after acid attack. The results of EDS and XRD confirmed that the regenerated minerals induced by G4-PAMAM-OH were hydroxyapatite (HA). Cytotoxicity assay showed that G4-PAMAM-OH had hardly any cytotoxicity towards dental pulp cells. In conclusion, G4-PAMAM-OH has great potential to be used in the treatment of dentin hypersensitivity in the future.

8DSS-promoted remineralization of demineralized dentin in vitro

Dentin phosphoprotein (DPP) plays an extremely important role in the biomineralization of human tooth. The repetitive nucleotide sequence of aspartate-serine-serine (DSS) is the fundamental unit within DPP, and peptides containing 8 repeats of DSS (8DSS) have been shown to possess the ability to induce remineralization of the demineralized enamel. In this work, we coated the 8DSS peptide on the completely demineralized dentin to evaluate the effect of 8DSS peptide coating on dentin remineralization. Human dentin samples were demineralized with 37% phosphoric acid for 2 min, and then the 8DSS peptide (1 mg mL-1) was coated and the binding strength of the 8DSS peptide to demineralized dentin was examined using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Then the coated dentin samples were immersed in artificial saliva for 3 weeks. After that, the remineralized dentin samples were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) analysis and ATR-FTIR. The mechanical properties of the remineralized surfaces were determined by nano-indentation and atomic force microscopy (AFM). The results showed that the 8DSS peptide had good binding strength to demineralized dentin and could induce nano-crystals precipitation both on the surfaces and within the dentinal tubules. The mechanical properties of the 8DSS-coated samples were significantly improved. In contrast, there were hardly any newly generated minerals deposited on the samples without 8DSS peptide coating. In conclusion, the 8DSS peptide may be a promising biomaterial for restoring the demineralized human dentin.

Natural Products and Caries Prevention

Dental caries is considered as the most common polymicrobial oral disease in the world. With the aim of developing alternative approaches to reduce or prevent the decay, numerous papers showed the potential anticaries activity of a number of natural products. The natural products with anticaries effects are selected from e.g. food, beverages, flowers or traditional herbs. Most of the effective components are proven to be polyphenol compounds. Many of the natural products are studied as antibacterial agents, while some of them are found to be effective in shifting the de-/remineralization balance. However, the mechanisms of the anticaries effects are still unclear for most of the natural products. In the future, more efforts need to be made to seek novel effective natural products via in vitro experiment, animal study and in situ investigations, as well as to enhance their anticaries effects with the help of novel technology like nanotechnology.

Biofilm Layers Affect the Treatment Outcomes of NaF and Nano-hydroxyapatite

During caries formation, dental biofilms function not only as acid producers but also as reservoirs and diffusion barriers for active caries-preventive components. The aim of this study was to investigate the influence of biofilms as a stagnant layer on the efficacy of NaF and nano-hydroxyapatite (nHA). Biofilms of Streptococcus mutans C180-2 were formed on the surfaces of artificially demineralized enamel in an active attachment biofilm model. After 2 days of biofilm formation, the model was subjected to a pH-cycling schedule, together with a control group without biofilms. Specimens were treated for 5 min twice daily with water, a 10% nHA slurry, or 18.4 mM NaF. At the end of the pH-cycling period, the biofilms were removed for the determination of the viable counts, the lactic acid production, and the calcium content. The mineral changes in the demineralized enamel blocks were analyzed by transversal microradiography. No differences in the biofilm viable counts and lactic acid production were found in the different treatment groups. The mean calcium content of the biofilms in the nHA group was 60.7 ± 15.3 mmol/g wet weight, which was approximately 8-fold higher than in the other 2 groups. The application of NaF resulted in net remineralization, but in the presence of a biofilm, net demineralization was observed. In contrast, nHA treatment reduced further demineralization compared with the water treatment, but the presence of a biofilm enhanced this effect. In conclusion, the presence of biofilms clearly influenced the treatment outcomes of anticaries products. Biofilms could either enhance or impede their efficacy. This result implies that biofilms should be included in the in vitro tests for the preclinical screening of caries-protective agents.

Novel tea polyphenol‐modified calcium phosphate nanoparticle and its remineralization potential

Tea polyphenols (TP) are not only potent antimicrobial and antioxidant agents but also effective modifiers in the formation of nanosized crystals. Since nano-hydroxyapatite (n-HA) is known to enhance remineralization of dental hard tissue, our aims were to synthesize nanosized calcium phosphate particles incorporating TP and to test their potential as caries preventive agent. An ammonia water diffusion method was used to synthesize nanosized calcium phosphate particles (TP-CaP) in the presence of various amounts of TP. The resultant products were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The remineralization potential of the nano TP-CaP was then investigated in a 12-day pH-cycling model. Nano TP-CaP slurries, at pH 7.0 and pH 5.5, were applied onto preformed enamel lesions 4 × 3 min per day. n-HA slurries at pH 7.0 and pH 5.5 were used as positive controls, and deionized water was served as a negative control. SEM showed nanosized particles were only formed at 27 mg/mL of TP. Further characterization of the nanosized particles revealed the components were amorphous calcium phosphate, HA, and TP. Both surface microhardness and transverse microradiography analyses showed that nano TP-CaP at pH 5.5, but not at pH 7.0, significantly enhanced remineralization, to the same extent as the n-HA controls. Furthermore, significantly higher amount of TP was found in the supernatant of TP-CaP at pH 5.5 than those at pH 7.0. Since TP can inhibit bacterial growth and enzyme activities, the novel nanosized TP-CaP particle, at low pH, is a potential dual-functional-remineralization and antibacteria-product.

Advances in polymeric materials for dental applications

Over the past decade, polymeric materials for clinical dental applications have been developed with excellent properties and various functionalities. This review outlines the present understanding and design of polymeric dental materials based on structure–property–function relationships. First, the chemistry/microstructure of polymeric materials will be reviewed. Then, the resultant properties such as mechanical, thermal, visco-elastic, and water solution properties, as well as additional bio-functionalities such as antibacterial capabilities, remineralization, and bioactive-delivery properties, will be reviewed for specific dental applications. Finally, perspectives and challenges regarding the rational design and application of polymeric dental materials will be discussed.

Effective in situ repair and bacteriostatic material of tooth enamel based on salivary acquired pellicle inspired oligomeric procyanidins

Remineralization and reduction of cariogenic bacteria at the tooth surface are effective ways to treat dental caries. In this work, a type of in situ repair and bacteriostatic material, i.e., salivary acquired pellicle inspired oligomeric procyanidins (SAP-OPC), was prepared for tooth enamel. Oligomeric procyanidins (OPC), as the active ingredient of grape seed extract, has good remineralization ability and bacteriostatic effects. The peptide sequence DDDEEKC, which has strong adsorption ability on hydroxyapatite (HA), is inspired by the sequence of statherin in the salivary acquired pellicle (SAP). Thus, SAP-OPC has the capability to tightly adsorb on the enamel surface, then repair the tooth decay and inhibit the growth of biofilm of cariogenic bacteria. We mainly explored the relationship between the remineralization property and aggregation morphology of SAP-OPC, and evaluate the anti-bacterial adhesion ability of the SAP-OPC coating. The acid-etched enamel was treated by SAP-OPC and SAP-OPC/Fe(III) and then incubated in artificial saliva. After 2 weeks, the HA mineralized layer was regenerated significantly on the surface of acid-etched enamel samples, and the hardness of the samples recovered to 61.6% and 76.8%, respectively. Also, SAP-OPC exhibited good antibacterial adhesive effects in the bacteriological test. In summary, SAP-OPC has good performance as restorative biomaterials to resist bacteria and also induce the remineralization of tooth enamel.