Discoloration of dental pellicle by tannic acid

Impact of common social habits on optical properties of lithium disilicate glass ceramic crowns: An in vitro study

Statement of the problem

Patient stratifications considered the stability of color and treatment longevity are key success of restoration. Daily consumption of colored beverages, such as coffee, tea, and soft drinks, as well as the use of globally consumed materials, such as smokeless tobacco (ST), snuff, Khat, and Yerba mate, can change the color of restorative materials, such as lithium disilicate glass ceramics (LDGC). These changes can ultimately lead to treatment failure.

Purpose

This in vitro study aimed to evaluate color changes, translucency, and opalescence of full anatomical LDGC crowns exposed to commonly used and potentially colorant solutions.

Materials and methods

Ninety LDGC specimens/crowns were prepared and divided into nine groups according to immersion solution (control, Saudi Coffee, Cola, Khat, Yerba mate, Nescafe, ST Snuff, and Mixed Fruit Juice). The specimens were immersed in colorant solutions for 15 days with alternating twice daily at 37 °C. Color parameters were measured with a spectrophotometer and calculated using two backgrounds (black and white). Data were subjected to ANOVA followed by the Student t-test and Bonferroni test at a significant difference level (α = 0.05).

Results

The greatest color change (ΔE*) among groups after immersion was observed in Yerba mate (7.6 ± 1.6). The mean difference of before and after staining within Yerba mate group was 3.14 ± 1.6 (p = 0.001). Translucency mean values of groups after immersion into staining media were ranging between 7.6 ± 1.2 and 9.1 ± 2, showing a slight decrease compared with pre-staining values but was not significantly different. Immersion in Mixed Fruit Juice significantly reduced opalescence (7.4 ± 1.9) compared to (8.8 ± 1.7) before staining.

Conclusion

The findings confirm that appropriate user guidance helps to preserve both translucency and opalescence as well as prevent color changes. This can improve patient compliance and promote treatment longevity.

Nanoparticles as Next-Generation Tooth-Whitening Agents: Progress and Perspectives

Whitening agents, such as hydrogen peroxide and carbamide peroxide, are currently used in clinical applications for dental esthetic and dental care. However, the free radicals generated by whitening agents cause pathological damage; therefore, their safety issues remain controversial. Furthermore, whitening agents are known to be unstable and short-lived. Since 2001, nanoparticles (NPs) have been researched for use in tooth whitening. Importantly, nanoparticles not only function as abrasives but also release reactive oxygen species and help remineralization. This review outlines the historical development of several NPs based on their whitening effects and side effects. NPs can be categorized into metals or metal oxides, ceramic particles, graphene oxide, and piezoelectric particles. Moreover, the status quo and future prospects are discussed, and recent progress in the development of NPs and their applications in various fields requiring tooth whitening is examined. This review promotes the research and development of next-generation NPs for use in tooth whitening.

Oral care product formulations, properties and challenges

This review explores the physical, chemical and structural properties of key components of oral care products, whilst looking at the challenges which need to be overcome to continue to improve the efficacy of oral care, and improve dental health. Oral care has been an essential part of all populations and cultures around the world for thousands of years. To maintain good oral health, dental plaque causing bacteria and malodour must be controlled whilst also strengthening and protecting the teeth to prevent dental caries. Advanced modern formulations need to provide controlled and extended release of ingredients vital for dental health. With modern day products such as toothpastes and mouthwashes, it has never been easier to maintain good oral hygiene and health, yet the incidence of dental caries is still on the rise. The complex formulations of modern toothpastes and mouthwashes makes them one of the most sophisticated pharmaceutical products on the market today. The demands of the consumer coupled with the complexity of the oral cavity make it one of the most challenging development processes.

Effects of Experimental Agents Containing Tannic Acid or Chitosan on the Bacterial Biofilm Formation in Situ

Chitosan and tannic acid are known for their antibacterial properties. In the present in-situ study, their antibacterial and anti-adherent effects on biofilm formation on enamel were investigated. Six subjects carried upper jaw splints with bovine enamel specimens, allowing in-situ biofilm formation. During the two-day trial, subjects rinsed with experimental solutions that contained either chitosan, tannic acid (pH = 2.5), tannic acid (pH = 7) or hydrochloric acid. Water served as the negative and chlorhexidine as the positive control. Rinsing occurred four or five times following two different rinsing protocols to investigate both the immediate and long-lasting effects. After 48 h of intraoral exposure, the dental plaque was stained with LIVE/DEAD^® BacLight, and fluorescence micrographs were evaluated by using the software ImageJ. The results were verified by scanning electron microscopy. Rinsing with chitosan resulted in little immediate antibacterial and anti-adherent effects but failed to show any long-lasting effect, while rinsing with tannic acid resulted in strong immediate and long-lasting effects. Except for a slightly lower antibacterial effect, the neutral solution of tannic acid was as good as the acidic solution. Hydrochloric acid showed neither an antibacterial nor an anti-adherent effect on dental biofilm formation. Experimental solutions containing tannic acid are promising anti-biofilm agents, irrespective of the pH values of the solutions. Chitosan, on the other hand, was not able to prevent biofilm formation.

Can the chlorhexidine gluconate solution potentiate the staining of polycrystalline ceramic brackets?

Aim: The present study aimed to assess, in vitro, the effect of chlorhexidine on the potentiation of polycrystalline ceramic bracket staining. Methods: Seventy-two polycrystalline ceramic brackets of upper right central incisors were divided into six groups (n=12) according to immersion solution. The groups were G1 - distilled water (control); G2 - chlorhexidine; G3 - coffee; G4 - red wine; G5 - chlorhexidine associated with coffee; and G6 - chlorhexidine associated with red wine. The samples were analyzed by means of a spectrophotometer according to the CIEL*a*b* system, and color change (ΔE*) was calculated. The readings were performed at the following times: T0 - After package removal and T1 - After staining. The data were analyzed by Kruskal Wallis and t tests (p<0.05) at 5% significance level. Results: The total color variation (ΔE*) was greater in the group that received chlorhexidine associated with red wine (p<0.05) and lower in the groups that received distilled water. All other groups showed greater value variations when compared to G1 and G2. Group G6 showed a greater color change due to the potentiation of chlorhexidine with the dye substance. Conclusion: It is concluded that chlorhexidine potentiates the staining caused by red wine in polycrystalline ceramic brackets.

An in vitro analysis model for investigating the staining effect of various chlorhexidine-based mouthwashes

Background

There are different mouthwashes containing chlorhexidine in different concentrations, as well as various excipients. Chlorhexidine induce stains or discoloration in teeth and mucous membranes. The aim of this work was to design a model to reproduce in vitro staining associated with the use of different mouthwashes containing chlorhexidine.

Material and Methods

We used as substrates of natural teeth and elephant ivory slices. Different incubation baths were conducted over 21 days in culture dishes at 37°C. At the beginning of experiment before incubation (D0) and after 21 days (D21) of incubation with different mouthwashes, pictures of substrates were taken in a standardized manner and an image analysis software was used to analyse and quantify the staining under the various conditions by using the 3 main colours (Red, Green, Blue, RGB).

Results

The results of this work demonstrate a very good reproducibility of the protocol, and secondly, a different expression statistically significant of the primary blue colour. We suggest that for a given concentration of chlorhexidine, the staining effects may vary depending on the excipients used.

Conclusions

This replicable model, easy to implement over a relatively short duration, can be used for evaluation of existing mouthwashes, and to test the excipients anti discoloration proposed by manufacturers.

Key words:In vitro, chlorhexidine, mouthwashes, dental stain, tooth discoloration.

Investigation of Factors Influencing Stain Formation Utilizing an in Situ Model

In order to understand the factors of extrinsic stain formation more fully, we have developed an in situ stain model. This consists of polished bovine enamel blocks attached to partial or full dentures worn by adult volunteers for 24 h per day. The dentures were cleaned twice daily with a commercial dentifrice and toothbrush, with care taken to avoid brushing the inserts. A Minolta CR321 Chroma Meter in the L*a*b* mode was used for taking reflectance measurements of the stain formed on the enamel inserts. From these values, changes in the color of the inserts were calculated and the level of stain determined. In general, the stain formed on the enamel inserts was yellow and increased in intensity and darkness with time. The enamel inserts with the largest stain increases were from smokers rather than non-smokers. No correlation was observed between amount of stain and quantity of tea and coffee consumed. When the effects of surface roughness on in situ stain formation were considered, the major variable in this study was found to be the location of the enamel insert in the denture rather than the surface roughness.

Mechanisms of Stain Formation on Teeth, in Particular Associated with Metal Ions and Antiseptics

Much has been written on the subject of extrinsic tooth discoloration, but, except when the pigment is intentionally applied, the etiologies and mechanisms are poorly understood. Extrinsic stains have been classified as non-metallic or metallic. The pigment usually lies not on or in the dental tissues, but in surface deposits, particularly the acquired pellicle layer and at sites receiving limited cleaning. Whether pigments absorb, adsorb, or chemically interact with dental surfaces is unclear. Some stains merely seem to reflect the color of the apparent source, whereas others have been ascribed to a secondary chemical alteration of a substance at the tooth or pellicle surface. Theories of chromogenic bacteria and formation of metal sulfides are frequently propounded but without clear supportive evidence. Staining by cationic antiseptics and, to a lesser extent, metal salts has attracted research interest. Chlorhexidine and other cationic antiseptics, it is hypothesized, may catalyze browning reactions or facilitate metal sulfide formation in pellicle. Controlled clinical studies have repeatedly shown that dental and mucosal staining associated with the use of chlorhexidine and some metal salts is dependent upon volunteers' imbibing reasonable quantities of chromogenic beverages, such as tea. However, it must be appreciated that cationic antiseptics and polyvalent metals can precipitate chromogenic material from a large range of dietary compounds. The control of dental staining, at least that associated with chlorhexidine, can be achieved both in vitro and in vivo by the use of oxidizing agents which appear to remove the stain physically from the surfaces.

Whitening toothpastes: a review of the literature

OBJECTIVES

To review and summarise the whitening agents contained within tooth whitening toothpaste formulations, their mode of action in tooth whitening, and the in vitro and clinical methods used to evaluate and demonstrate their efficacy.

METHODS

Original scientific full papers or reviews listed in ISI Web of Science and Medline were included in this review using the search terms white*, toothpaste and dentifrice.

CONCLUSIONS

Due to the reported consumer and patient dissatisfaction with their perceived tooth color, toothpaste manufacturers have responded by developing a vast array of contemporary whitening toothpastes. One of the key functional ingredients in whitening toothpastes is the abrasive system. In general, these have been designed to give effective removal of extrinsic stains and help prevent tooth stains from reforming without undue abrasivity towards the dental hard tissues. Whitening toothpastes may contain additional agents that augment the abrasive cleaning by aiding the removal and/or prevention of extrinsic stains, for examples, peroxide, enzymes, citrate, pyrophosphate and hexametaphosphate, or optical agents such as blue covarine which can improve tooth whiteness following tooth brushing. In vitro methods used to evaluate tooth whitening efficacy typically determine the ability of a toothpaste formulation to remove/prevent model extrinsic stains on substrates such as enamel or hydroxyapatite or changes in the intrinsic color of tooth specimens. Clinical protocols for evaluating the efficacy of whitening toothpastes typically determine either stain removal or prevention, where changes in natural stain or chlorhexidine/tea induced stain are measured typically over 2-6 weeks. In some clinical studies the overall tooth color change was measured using techniques such as Vita shade guides, colorimeters and image analysis of digital photographs of teeth.

Influence of salivary organic substances on the discoloration of esthetic dental materials-a review

The objective of this article was to review the articles on the interaction of salivary organic substances with resin-based dental materials and on the interaction of these organic substances with exogenous chemical agents, which results in discoloration. Original scientific articles or reviews on the saliva, acquired pellicle, and the interaction with pellicle and chemical agents related to dental resin-based materials were reviewed. Salivary esterases can increase or decrease the internal and external discoloration. The formation of acquired pellicle on the surface of a material varies by the properties of material, and the pellicle interacts with denaturation agents, such as tannin and chlorhexidine, to form stains and also adsorbs staining substances. Therefore, for the quality and longevity of restorations, protocols for the evaluation of the influence of organic substances on the extrinsic staining of restorative materials should be included in the evaluation of aesthetic restorative materials.

The measurement of enamel and dentine abrasion by tooth whitening products using an in situ model

OBJECTIVES

To determine the enamel and dentine wear of two whitening toothpastes using an in situ model with ex vivo brushing.

METHODS

Human enamel/dentine (approximately 50:50) blocks (approximately 4 x 4mm) were placed in the upper buccal aspects of full or partial dentures of a group of 25 subjects. Subjects brushed the specimens ex vivo with either a calcium carbonate/perlite or silica containing whitening toothpaste under exaggerated conditions as compared to normal for 30 s, twice per day. Specimens were removed after 4, 8 and 12 weeks and the wear to the enamel and dentine was determined. Enamel wear was determined by change in Knoop indent length and dentine wear was determined from the enamel-dentine step height, measured using optical profilometry.

RESULTS

The mean wear after 12 weeks was for enamel 0.27 and 0.19 microns, and for dentine 34.3 and 61.1 microns, for the calcium carbonate/perlite and silica toothpastes respectively. There were no significant differences between products after 12 weeks. The rate of wear was found to decrease throughout the duration of the study.

CONCLUSION

There were no significant differences between the two whitening toothpastes in terms of enamel and dentine wear after 12 weeks brushing.

Ellipsometry analysis of the in vitro adsorption of tea polyphenols onto salivary pellicles

The adsorption of components from black tea and of purified tea polyphenols onto a whole unstimulated salivary pellicle-like protein layer, formed in vitro on hydroxyapatite discs, was studied by in situ ellipsometry. It was found that components from black tea and the purified polyphenols epicatechin-3-gallate (ECG), epigallocatechin-3-gallate (EGCG) and theaflavin readily adsorbed onto the pellicle. Further investigations showed that under the experimental conditions of this study, no black tea- or purified polyphenol-modified pellicles were eluted by either phosphate buffer or sodium dodecyl sulphate rinses. Therefore, black tea and its polyphenol components are indicated to have a profound effect on in vitro pellicle modification. Similar effects were observed for tannic acid.

Tooth discolouration and staining: a review of the literature

OBJECTIVE

To carry out an extensive review of the literature on tooth staining with particular regard to some of the more recent literature on the mechanisms of tooth staining involving mouthrinses.

DESIGN

Comprehensive review of the literature over four decades.

CONCLUSIONS

A knowledge of the aetiology of tooth staining is of importance to dental surgeons in order to enable a correct diagnosis to be made when examining a discoloured dentition and allows the dental practitioner to explain to the patient the exact nature of the condition. In some instances, the mechanism of staining may have an effect on the outcome of treatment and influence the treatment options the dentist will be able to offer to patients.

Tannic acid for smear layer removal: pilot study with scanning electron microscope

The effects of a 25% tannic acid solution applied to the surface of prepared dentin was compared with untreated prepared dentin surfaces. The following results were demonstrated by electron microscope observation: (1) cavity preparations created an amorphous dentinal smear layer, (2) placement of a 25% tannic acid solution for 15 seconds removed the smear layer, (3) the contents of the dentinal tubules were not removed and no enlargement of dentinal tubules was found, and (3) a clean dentinal surface was observed.

Chemical plaque control and extrinsic tooth discoloration. A review of possible mechanisms

The etiology of extrinsic tooth discolorations due to chemical, plaque-preventive agents is not fully understood. However, information from experimental investigations point to at least 3 possible mechanisms. (A) Non-enzymatic browning reactions (Maillard reactions). (B) Formation of pigmented metal (Fe, Sn)-sulfides. (C) Reaction products of food and beverage constituents and chemical, plaque-preventive compounds. Available evidence indicates that browning (A) and formation of pigmented metal sulfides (B) are the most likely causes of these discolorations while dietary factors (C) may play a modifying rôle.

Iron discoloration of acrylic resin exposed to chlorhexidine or tannic acid: a model study

A clinical model was introduced to study the ability of chlorhexidine, tannic acid, and iron to discolor dental plaque formed on acrylic resin surfaces. None of the agents caused discoloration when applied individually five times daily during a 5-day period. However, exposure of the dental plaque to either chlorhexidine or tannic acid before the iron applications produced marked staining. Possible mechanisms, among which denaturation appears to be significant, are discussed. The use of a strong oxidizing agent, peroxymonosulfate, completely bleached the established discolorations.

Iron staining of the acquired enamel pellicle after exposure to tannic acid or chlorhexidine: preliminary report

Extrinsic discoloration of teeth following a large consumption of tannin-containing beverages or a prolonged use of chlorhexidine mouthrinses is a well known observation. Tannins as well as chlorhexidine are denaturing agents. Based on preliminary studies revealing the presence of iron in chlorhexidine discolored pellicle material, the ability of iron to stain the integument after pretreatment with the two denaturants was studied in a human model. The denaturing effect of an acidic environment was also included. Enamel slabs fixed to acrylic appliances were carried in the oral cavity and alternately exposed to the test solutions in different sequences in vitro. Pretreatment with chlorhexidine or tannic acid led to marked discoloration upon iron application during 5-d tests, whereas the compounds individually had no such effect. A large content of the metal was found in the stained material. Stannous fluoride appeared to reduce the formation of the pigments, and strong oxidation completely bleached the established color. Possible mechanisms underlying the phenomena observed are discussed.

Comparison of the bisbiguanide antiseptics alexidine and chlorhexidine. II. Clinical and in vitro staining properties

A blind cross-over trial was carried out to compare the tooth and tongue staining associated with the use of a 0.035% alexidine and a 0.2% chlorhexidine mouthrinse. Twenty-two volunteers were divided into two groups termed "tea drinkers" and "non-tea drinkers". All volunteers were requested to refrain from oral hygiene measures throughout two 10-day periods when they rinsed twice a day with the preparation randomly allocated for the respective period. During both periods the members of the groups excluded coffee, red wine and port from their diet. The tea drinking group consumed seven cups of tea per day. Tooth and tongue staining was recorded for extent and severity at the end of each period. The amount of stain accumulating in the two groups was similar following the use of chlorhexidine and alexidine. However, for both chlorhexidine and alexidine the extent and severity of tooth and tongue staining were significantly increased in the tea drinking group. An in vitro study of tea staining of perspex blocks exposed twice a day to 0.035% solutions of alexidine or chlorhexidine throughout a 5-day period demonstrated significantly more staining with alexidine when measured spectrophotometrically. Visually however, the differences in the specimens were minimal. Saliva treatment of the perspex did not significantly alter the staining by alexidine or chlorhexidine. The results provide further evidence for a dietary aetiology to the staining associated with cationic antiseptics. However, alexidine at the concentration used offered no advantage in reducing the side effect of staining when compared with chlorhexidine.

Extrinsic discoloration of teeth

The majority of tooth discolorations are extrinsic in nature and appear as brown integuments. Various clinical indices and photometric techniques have been used for the evaluation of extrinsic discolorations. Smoking, tea or coffee consumption and increasing age are promoting factors and such discolorations are frequently seen in connection with oral use of antibacterial plaque-inhibiting mouthrinses. Chemical alteration of the acquired pellicle appears to be the major reason for these brown integuments.