A scanning electron microscopic study of tooth surface changes induced by tannic acid

2D and 3D Erosion Landscape Analysis of Endodontic-Treated Teeth Using EDTA and HEDP as Chelating Agents: A High-Resolution Micro-Computed Tomographic Study

This study aimed to assess the amount of erosion during activated endodontic irrigation with either HEDP or EDTA via high-resolution micro-computed tomography. Two root canals of twenty premolars were prepared with ProTaper Next and irrigated with sodium hypochlorite. Palatal canals, which served as control groups, were sealed, while buccal canals were further irrigated with either EDTA (n = 10) or HEDP (n = 10), which served as test groups. Micro-CT was performed to measure erosion depth. For 2D and 3D measurements, non-parametric repeated ANOVA measurements and post hoc tests were performed. 2D analysis showed highly significant differences between the case groups at each position of the root (p ≤ 0.01). The cervical and apical positions showed significant differences in the EDTA group (p = 0.03). The 3D analysis also showed significant differences between both chelating agents (p < 0.01) and the case and control groups (p = 0.01). The mean erosion depths in the cervical, middle, and apical thirds of the EDTA group were 45.75, 41.79, and 32.25 µm, and for the HEDP group were 20.25, 16.40, and 15.96 µm, respectively. HEDP seems to have a significantly less erosive effect. Different irrigation protocols with harsher conditions, as might be the case during endodontic retreatment, could be assessed with micro-CT.

The effect of polyphenol-containing solutions on in situ biofilm formation on enamel and dentin

OBJECTIVES

To investigate the effects of Chinese gallnut extracts and pure tannic acid on in situ biofilm formation on enamel and dentin samples over 24 h.

METHODS

Bovine enamel and dentin samples were buccally fixed on maxillary splints. Six volunteers wore the splints for 24 h, and rinsed their mouths with tap water (control), 1% tannic acid- and 1% Chinese gallnut extracts-containing solution twice a day, 3 min after the splints were placed in the mouth and before night sleep. Live/dead staining was used for fluorescence microscopic (FM) visualization and quantification of bacteria viability of biofilms formed on enamel and dentin samples. Biofilm coverage was evaluated and recorded by FM and scanning electron microscopy (SEM). In addition, biofilms were analyzed by transmission electron microscopy (TEM). The Kruskal-Wallis test was used to analyze biofilm data.

RESULTS

Rinsing with tannic acid- and Chinese gallnut extracts-containing solutions significantly reduced in situ biofilm coverage on enamel and dentin samples (P < 0.05). The bacterial viability of biofilms formed on enamel samples was significantly reduced compared to the control (P < 0.05). TEM analysis revealed an increase in pellicle's electron density and thickness and only few or no bacteria adherent to the pellicle in the experimental samples.

CONCLUSIONS

Rinsing with tannic acid- and Chinese gallnut extracts-containing solutions can effectively inhibit in situ biofilm formation, modify the ultrastructure of biofilms on enamel and dentin surfaces and significantly reduce the bacterial viability of biofilm on enamel surfaces.

CLINICAL SIGNIFICANCE

Tannic acid- and Chinese gallnut extracts-containing solutions might be used for dental biofilm management.

Polyphenols in Dental Applications

(1) Background: polyphenols are a broad class of molecules extracted from plants and have a large repertoire of biological activities. Biomimetic inspiration from the effects of tea or red wine on the surface of cups or glass lead to the emergence of versatile surface chemistry with polyphenols. Owing to their hydrogen bonding abilities, coordination chemistry with metallic cations and redox properties, polyphenols are able to interact, covalently or not, with a large repertoire of chemical moieties, and can hence be used to modify the surface chemistry of almost all classes of materials. (2) Methods: the use of polyphenols to modify the surface properties of dental materials, mostly enamel and dentin, to afford them with better adhesion to resins and improved biological properties, such as antimicrobial activity, started more than 20 years ago, but no general overview has been written to our knowledge. (3) Results: the present review is aimed to show that molecules from all the major classes of polyphenolics allow for low coast improvements of dental materials and engineering of dental tissues.

Effect of Tannic Acid on Bond Strength of Etch and Rinse and Self-etch Adhesive Systems in Dentin of Primary Teeth

INTRODUCTION

One of the possible mechanisms for the gradual destruction of bond strength in dentin-resin interface, could be due to the demineralized unstable collagen matrix. Use of protease inhibitors, such as tannic acid (TA) could prevent destruction of collagen fibers. The aim of this study was to compare the TA effect on bond strength of etch and rinse and self-etch adhesive systems in the dentin of primary teeth.

MATERIALS AND METHODS

This in vitro study was done on 40 extracted primary molar teeth. The teeth were sectioned in the mesiodistal direction, and enamel of buccal and lingual surfaces was removed. Samples were randomly divided into four groups: Single bond (SB) + TA, SB, Clearfil SE Bond (CSB) + TA, and CSB. Then, Z250 and Clearfil AP-X composites were cured on the surfaces of SB and CSB groups respectively. After that, all samples were divided into aging and non-aging groups. For 3 months, samples were placed under 1,000 thermal cycles in aging group. Subsequently, the shear bond strengths of all groups were measured by the International testing machine, and failure mode was evaluated by an optical stereomicroscope. Data were analyzed with paired t-test and independent t-test.

RESULTS

Tannic acid induced a significant reduction in the immediate bond strength of adhesive SB. Meanwhile, TA had no significant effect on shear bond strength of the CSB system.

CONCLUSION

Based on our findings, use of TA is not recommended with SB and CSB adhesives on primary teeth.

CLINICAL SIGNIFICANCE

Tannic acid may not be considered in resin restorations of primary teeth.

The effect of dentin pretreatment on the microtensile bond strength of self-adhesive resin cements

STATEMENT OF PROBLEM

Self-adhesive cements have lower bond strength than conventional resin cements that rely on the application of etch-and-rinse adhesive systems.

PURPOSE

The purpose of this study was to evaluate the effect of tannic and polyacrylic acid on the microtensile bond strength of self-adhesive resin cements to dentin.

MATERIAL AND METHODS

Eighteen molar crowns were flattened to expose dentin and divided into 3 groups according to the dentin pretreatment: (1) control, without surface treatment; (2) 25% polyacrylic acid solution (Ketac Conditioner); (3) 20% tannic acid. Composite resin (Tescera) blocks were luted to dentin surfaces using 2 self-adhesive resin cements (RelyX Unicem or Maxcem Elite) (n=3). All specimens were stored in distilled water for 24 hours, sectioned into beams (1 mm(2)), and tested to failure using a microtensile method at a crosshead speed of 1 mm/min. The data were statistically analyzed using 2-way ANOVA and Fisher's PLSD tests (α=.05).

RESULTS

The polyacrylic acid significantly improved the microtensile bond strength of RelyX Unicem (14.92 ±4.94 MPa) when compared to the control group (8.35 ±1.99 MPa) and tannic acid treatment (8.38 ±2.67 MPa) (P<.001). Dentin surface treatment did not affect the microtensile bond strength of Maxcem Elite cemented groups (control, 8.45 ±3.21 MPa; polyacrylic acid, 9.53 ±9.95 MPa; tannic acid, 6.89 ±4.45 MPa).

CONCLUSIONS

Dentin pretreatment with polyacrylic acid improved the microtensile bond strength of RelyX Unicem.

The smear layer in endodontics - a review

Root canal instrumentation produces a layer of organic and inorganic material called the smear layer that may also contain bacteria and their by-products. It can prevent the penetration of intracanal medicaments into dentinal tubules and influence the adaptation of filling materials to canal walls. This article provides an overview of the smear layer, focusing on its relevance to endodontics. The PubMed database was used initially; the reference list for smear layer featured 1277 articles, and for both smear layer dentine and smear layer root canal revealed 1455 publications. Smear layer endodontics disclosed 408 papers. A forward search was undertaken on selected articles and using some author names. Potentially relevant material was also sought in contemporary endodontic texts, whilst older books revealed historic information and primary research not found electronically, such that this paper does not represent a 'classical' review. Data obtained suggests that smear layer removal should enhance canal disinfection. Current methods of smear removal include chemical, ultrasonic and laser techniques - none of which are totally effective throughout the length of all canals or are universally accepted. If smear is to be removed, the method of choice seems to be the alternate use of ethylenediaminetetraacetic acid and sodium hypochlorite solutions. Conflict remains regarding the removal of the smear layer before filling root canals, with investigations required to determine the role of the smear layer in the outcomes of root canal treatment.

Mechanical properties of tannic-acid-treated dentin matrix

Dentin collagen is a major component of the hybrid layer, and its stability may have a great impact on the properties of adhesive interfaces. We tested the hypothesis that the use of tannic acid (TA), a collagen cross-linking agent, may affect the mechanical properties and stability of the dentin matrix. The present study evaluated the effects of different concentrations of TA on the modulus of elasticity and enzymatic degradation of dentin matrix. Hence, the effect of TA pre-treatment on resin-dentin bond strength was assessed with the use of two bonding systems. Sound human molars were used and prepared according to each experimental design. The use of TA affected the properties of demineralized dentin by increasing its stiffness. TA treatment inhibited the effect of collagenase digestion on dentin matrix, particularly for 10%TA and 20%TA. The TA-dentin matrix complex resulted in improved bond strength for both adhesive systems.

Internalized discoloration of dentin under porcelain crowns: a clinical report

This clinical report describes the situation of a patient who was concerned about the appearance of porcelain crowns that were placed on the maxillary incisors 4 years prior. The mechanicochemical gingival retraction technique combining the use of ferric sulfate and knitted retraction cord is described as a possible etiology of internalized discoloration of the dentin in this situation. The hypothesis is explained by the high acidity of gingival retraction fluids (GRFs) and the high affinity of iron for hard tooth tissues, resulting in an interaction with bacterial byproducts and precipitation of insoluble ferric sulfide in the porous demineralized dentin. A prospective clinical trial is warranted to track the effects of GRFs on tooth structure. This article describes the treatment of internalized discoloration of dentin under porcelain crowns.

Clinical implications of the smear layer in endodontics: a review

It has been recognized for many years that root canal instrumentation produces a smear layer that covers the surfaces of prepared canal walls. This layer contains inorganic and organic substances such as fragments of odontoblastic processes and necrotic debris. There is a lack of agreement regarding the effect of the smear layer on the quality of instrumentation and obturation, but the smear layer itself may be infected and may protect the bacteria within the dentinal tubules. Various methods have been used to remove the smear layer. Conflicting results have been obtained from numerous in vitro studies regarding the significance of the presence or the removal of the smear layer.