Characterization of Dentin Matrix Biomodified by Galla Chinensis Extract

Theaflavin -3,3'-digallate/ethanol: a novel cross-linker for stabilizing dentin collagen

Objectives

To study the ability of theaflavin-3,3'-digallate (TF3)/ethanol solution to crosslink demineralized dentin collagen, resist collagenase digestion, and explore the potential mechanism.

Methods

Fully demineralized dentin blocks were prepared using human third molars that were caries-free. Then, these blocks were randomly allocated into 14 separate groups (n = 6), namely, control, ethanol, 5% glutaraldehyde (GA), 12.5, 25, 50, and 100 mg/ml TF3/ethanol solution groups. Each group was further divided into two subgroups based on crosslinking time: 30 and 60 s. The efficacy and mechanism of TF3's interaction with dentin type I collagen were predicted through molecular docking. The cross-linking, anti-enzymatic degradation, and biomechanical properties were studied by weight loss, hydroxyproline release, scanning/transmission electron microscopy (SEM/TEM), in situ zymography, surface hardness, thermogravimetric analysis, and swelling ratio. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy were utilized to explore its mechanisms. Statistical analysis was performed using one and two-way analysis of variance and Tukey's test.

Results

TF3/ethanol solution could effectively crosslink demineralized dentin collagen and improve its resistance to collagenase digestion and biomechanical properties (p < 0.05), showing concentration and time dependence. The effect of 25 and 50 mg/ml TF3/ethanol solution was similar to that of 5% GA, whereas the 100 mg/mL TF3/ethanol solution exhibited better performance (p < 0.05). TF3 and dentin type I collagen are mainly cross-linked by hydrogen bonds, and there may be covalent and hydrophobic interactions.

Conclusion

TF3 has the capability to efficiently cross-link demineralized dentin collagen, enhancing its resistance to collagenase enzymatic hydrolysis and biomechanical properties within clinically acceptable timeframes (30 s/60 s). Additionally, it exhibits promise in enhancing the longevity of dentin adhesion.

A Novel Chemical Binding Primer to Improve Dentin Bonding Durability

The dentin collagen matrix that is not completely enveloped by resin adhesive is vulnerable to degradation by intrinsic collagenases during the etch-and-rinse process, which contributes to the deterioration of the bonding interface. Current commercial adhesives have no functional components that can form covalent bonds to the dentin collagen matrix. In this study, a photocurable aldehyde, 4-formylphenyl acrylate (FA), was synthesized and for the first time applied as a primer in adhesive dentistry to covalently bind to collagen. Experimental groups with different concentrations of FA (1%, 3%, 5%, 7%, 9%) were prepared as primers. The cytotoxicity was evaluated by live/dead-cell staining and thiazolyl blue tetrazolium bromide assay. The interaction of FA with collagen was examined by attenuated total reflection Fourier transform infrared spectroscopy, hydroxyproline release under the degradation of type I collagenase, and thermogravimetric analysis. An optimal group was selected based on the degree of conversion of 2 universal adhesives and further divided depending on the treatment time (20 s, 30 s, 1 min, 2 min). The bonding performances were evaluated by microtensile strength before and after aging. Finally, the bonding interface was observed under confocal laser scanning microscopy and scanning electron microscope. The results indicated that FA demonstrated good biocompatibility, dentin modification capability, and infiltration. It not only effectively cross-linked dentin collagen to improve its stability against enzymatic hydrolysis and modify the adhesive interface but also potentially acted as a diluting monomer to induce deep penetration of adhesive resin monomers into the dentin. The bonding strength after aging was improved without jeopardizing the degree of conversion of 2 commercial adhesives. Such prominent advantages of using FA to improve the bonding performance promotes its further application in adhesive dentistry.

Effect of Galla Chinensis on Remineralization of Early Dentin Lesion

Objective  This study aimed to investigate the efficacy of the Galla chinensis extract (GCE) on early dentin lesion remineralization.

Materials and Methods  Seventy-two dentin specimens were divided into three groups according to the treatment solution. In group S1, specimens were treated with GCE; in group S2, the specimens were treated with sodium fluoride (NaF); meanwhile, specimens of group S3 were treated with distilled water (DW). Each group was further subdivided into two subgroups according to the treatment time (1 minute and 5 minutes). An in vitro pH-cycling model for 12 days was done. Subsequently, surface microhardness (SMH) of the specimens, elemental analysis, and their micromorphological appearance were evaluated.

Statistical Analysis  Data were statistically analyzed. One-way analysis of variance was used to compare numerical (parametric) data between more than two separate groups followed by post hoc Tukey.

Results  There was no significant difference between the mean SMH of dentin between NaF and GCE groups. Regarding the time, the 5-minute treatment with NaF and DW groups recorded higher mean SMH value of dentin than the 1-minute treatment group. Meanwhile, for GCE groups, the 1-minute immersion recorded higher mean SMH value than the 5-minute immersion without any significant difference between them. The microhardness results were confirmed by environmental scanning electron microscope and energy dispersive X-ray analysis results.

Conclusion  GCE could be used as an effective alternative for dentin remineralization.

The Effects of a Toothpaste Containing the Active Ingredients of Galla chinensis and Sodium Fluoride on Dentin Hypersensitivity and Sealing of Dentinal Tubules: An In Vitro Study and an Eight-Week Clinical Study in 98 Patients

BACKGROUND This study aimed to evaluate the desensitizing effect of toothpaste containing the active ingredients of an extract of Galla chinensis, both in vitro and in patients with dentin hypersensitivity. MATERIAL AND METHODS Ninety-eight patients with dentin hypersensitivity were divided into two study groups and given toothpaste containing either the active ingredients of Galla chinensis extract and sodium fluoride, or a control toothpaste containing only sodium fluoride. Assessments included the tactile stimulation test and the Schiff cold air sensitivity scale, which were conducted at the baseline examination and after 4 and 8 weeks of dental brushing. Twenty-five intact human premolars from 24 patients with dentin hypersensitivity were prepared and randomly divided into four groups, the untreated baseline group, the study group, the positive control group, and the control group. After brushing with different toothpaste for 7 days, the effects on dentinal tubule sealing in each group was determined by scanning electron microscopy (SEM), and the degree of dentinal tubule plugging and diameter of the open dentinal tubules were calculated. RESULTS Toothpaste containing the active ingredients of Galla chinensis and sodium fluoride significantly reduced the degree of dentin hypersensitivity when compared with toothpaste containing sodium fluoride alone after 4 weeks and 8 weeks of use. Toothpaste containing the active ingredients of Galla chinensis significantly reduced the number and diameter of the open dentinal tubules. CONCLUSIONS Toothpaste that contained the active ingredients of Galla chinensis and sodium fluoride reduced the symptoms of dentin hypersensitivity by sealing the dentinal tubules.

Preparation and Characterization of UV-Curable Acrylic Membranes Embedding Natural Antioxidants

We examine the behaviour of acrylic resin-based membranes containing natural anti-oxidants, such as Galla chinensis tea powder extract (TP) and Taiwanese green propolis (TGP), in different concentrations ranging between 5 and 20 wt %. Membrane morphology was investigated by means of Environmental Scanning Electron Microscopy (ESEM), while the UV-curing reaction was monitored by Fourier-Transform Infra-red (FTIR) spectroscopy. In most cases Thermogravimetric (TG), Differential Scanning Calorimetric (DSC) and Dynamo-mechanical Thermal (DMT) analyses showed that the desirable characteristics of the UV-cured acrylic resin are not substantially altered by the presence of the organic fillers. The release kinetics of polyphenols and flavonoids, determined in water for TP-containing membranes (ETx) and in ethanol/water mixture (7:3 v/v) for TGP-containing ones (EPx), was satisfactory, reaching a plateau after 24 h. Finally, preliminary antibacterial tests against S. epidermidis were performed on the membranes with higher additive amount and gave positive results for ET-type; on the contrary, no inhibitory effect was observed for the tested EP-type membranes.

Effects of lemon essential oil and limonene on the progress of early caries: An in vitro study

OBJECTIVE

The purpose of this study was to investigate the effects of Lemon essential oil (LEO) and Limonene (LIM) in the progress of early caries.

DESIGN

LEO and LIM were selected as experimental medicine, while sodium fluoride (NaF) and deionized water (DW) were positive and blank controls, respectively. Bovine incisors were used to establish enamel and dentin early caries models by demineralization method in vitro. Then specimens were subjected to pH cycling. Calcium and phosphate release of demineralizing solution were measured by an automatic biochemical analyzer; Surface microhardness tester and energy dispersive X-ray spectrometer were used to detect the surface microhardness recovery and calcium- phosphate ratio on tooth surface; Degraded collagen matrix by collagenase was investigated by assaying hydroxyproline.

RESULTS

Calcium release of dentin demineralizing solution of LEO group was lower than DW group's and higher than NaF group's. Both of LEO and LIM groups, the surface microhardness recovery were significantly lower than those of NaF group, which were similar to DW group. Dentin surface calcium- phosphate ratio of LEO and LIM groups were lower than those of NaF group and higher than those of DW group. Hydroxyproline concentration in the remineralizing solution of LEO and LIM groups were lower than DW groups' and higher than NaF groups'.

CONCLUSIONS

LEO and LIM have influence on the progress of dentin early caries, which can stabilize its structure by inhibiting collagen degradation. Meanwhile, these medicines may provide a new drug choice for the prevention and treatment of early root caries.

Effects of Collagen Crosslinkers on Dentine: A Literature Review

This aim of this review is to explore the current research related to crosslinking agents used on dentine. A systematic search of publications in PubMed and Web of Science databases was performed. Further retrieval was conducted using the search terms of specific names of crosslinkers. Reviews, conference abstracts, dissertation and theses, non-English articles, studies of intrinsic crosslinking of dentine, studies of adhesives without specific crosslinker components, studies of crosslinker applications in other collagenous tissues or tooth-like structures and irrelevant studies were excluded. Manual screening was conducted on the bibliographies of remaining papers to identify other relevant articles. One hundred and one articles were included in this systematic review and full texts were retrieved. Both synthetic and naturally derived crosslinkers have been found to exhibit significant effects in biomodification of dentine via their multiple interactions with the dentine matrix. A stable matrix network or a durable hybrid layer in dentine bonding could be achieved, where the dentine collagen fibrils show improved biochemical and biomechanical properties and enzymatic biodegradation is reduced. Although no crosslinkers have been tested in clinical trials, extensive research has been conducted in laboratory studies to investigate their potential applicability for inhibition of demineralisation and/or promotion of remineralisation, caries prevention as well as improvement of bonding performance of adhesive systems. Further studies are needed to develop the feasibility for clinical use, reduce side effects as well as explore mechanisms of action and long-term effectiveness.

Comparison of Composition and Anticaries Effect of Galla Chinensis Extracts with Different Isolation Methods

Objectives:

Galla chinensis water extract (GCE) has been demonstrated to inhibit dental caries by favorably shifting the demineralization/remineralization balance of enamel and inhibiting the biomass and acid formation of dental biofilm. The present study focused on the comparison of composition and anticaries effect of Galla chinensis extracts with different isolation methods, aiming to improve the efficacy of caries prevention.

Methods:

The composition of water extract (GCE), ethanol extract (eGCE) and commercial tannic acid was compared. High performance liquid chromatography coupled to electrospray ionization-time of flight-mass spectrometry (HPLC-ESI-TOF-MS) analysis was used to analyze the main ingredients. In vitro pH-cycling regime and polymicrobial biofilms model were used to assess the ability of different Galla chinensis extracts to inhibit enamel demineralization, acid formation and biofilm formation.

Results:

All the GCE, eGCE and tannic acid contained a high level of total phenolics. HPLC-ESI-TOF-MS analysis showed that the main ingredients of GCE were gallic acid (GA), while eGCE mainly contained 4-7 galloylglucopyranoses (GGs) and tannic acid mainly contained 5-10 GGs. Furthermore, eGCE and tannic acid showed a better effect on inhibiting enamel demineralization, acid formation and biofilm formation compared to GCE.

Conclusions:

Galla chinensis extracts with higher tannin content were suggested to have higher potential to prevent dental caries.

Control of hydroxyapatite crystal growth by gallic acid

The purpose of this study is to detect the effect of gallic acid (GA) on hydroxyapatie crystal growth and find the mechanism of the regulation. We evaluated the morphology of HAP crystals grown under various amounts of GA (0, 0.05, 1, and 4 gL(-1)). Subsequently, the chemical composition, crystal size and the morphology were investigated via the energy-dispersive X-ray spectrometer, attenuated total fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction analysis, transmission electron microscope and scanning electron microscopy. In all groups, the Ca/P ratio was closed to 1.67. In the absence of GA, crystals did not arrange, while in the presence of GA, crystals tended to form spherules. The size of the crystals decreased with the concentration of GA increased. These results indicated the role of GA on the growth and morphology of hydroxyapatite crystals, which might be the key mechanism for gallic acid regulating the mineralization.

Changes in composition and enamel demineralization inhibition activities of gallic acid at different pH values

BACKGROUND

Gallic acid (GA) has been shown to inhibit demineralization and enhance remineralization of enamel; however, GA solution is highly acidic. This study was to investigate the stability of GA solutions at various pH and to examine the resultant effects on enamel demineralization.

METHODS

The stability of GA in H2O or in phosphate buffer at pH 5.5, pH 7.0 and pH 10.0 was evaluated qualitatively by ultraviolet absorption spectra and quantified by high performance liquid chromatography with diode array detection (HPLC-DAD). Then, bovine enamel blocks were subjected to a pH-cycling regime of 12 cycles. Each cycle included 5 min applications with one of the following treatments: 1 g/L NaF (positive control), 4 g/L GA in H2O or buffered at pH 5.5, pH 7.0 and pH 10.0 and buffers without GA at the same pH (negative control), followed by a 60 min application with pH 5.0 acidic buffers and a 5 min application with neutral buffers. The acidic buffers were analysed for dissolved calcium.

RESULTS

GA was stable in pure water and acidic condition, but was unstable in neutral and alkaline conditions, in which ultraviolet spectra changed and HPLC-DAD analysis revealed that most of the GA was degraded. All the GA groups significantly inhibited demineralization (p < 0.05) and there was no significant difference of the inhibition efficacy among different GA groups (p > 0.05).

CONCLUSIONS

GA could inhibit enamel demineralization and the inhibition effect is not influenced by pH. GA could be a useful source as an anti-cariogenic agent for broad practical application.