Human Pellicle Research Articles

The erosive effect of various drinks, foods, stimulants, medications and mouthwashes on human tooth enamel

Two forms of non-carious dental disorder - erosive tooth hard tissue loss and dental erosion - have been increasingly observed in recent years. Dental erosion is the chemical loss of dental hard substances caused by exposure to acids not derived from oral bacteria. Mechanical forces from, for example, the tongue, the cheeks or toothbrushing, increase loss of partly-demineralized tooth surfaces and the cumulative loss of dental hard tissue is defined as erosive tooth wear (ETW). Dental hard tissue losses which occur because of very frequent acid exposure, such as through increased vomiting, but without mechanical stress, are also assigned to tooth erosion. Without prior softening, practically no loss of enamel takes place due to abrasion with the modern Western diet. The present work is a continuation of earlier work. A total of 226 beverages, food, stimulants as well as medicines and mouthwashes were tested for their erosive potential on premolars and deciduous molars covered with a human pellicle. The influence of temperature, phosphate and calcium was also investigated in additional experiments. The change in hardness before and after immersion in the respective test substance was measured and the erosive potential was classified. For each test product, we determined pH and other properties which were possibly related to erosive potential. There were considerable and sometimes surprising differences between the tested products. The addition of phosphate did not influence the erosive potential of the liquids, but calcium did. A modified erosion scheme is presented, which incorporates these and other new findings.
 Accepted for publication: February 6, 2023
 Published online: February 21, 2023

The erosive effect of various drinks, foods, stimulants, medications and mouthwashes on human tooth enamel.

Two forms of non-carious dental disorder - erosive tooth hard tissue loss and dental erosion - have been increasingly observed in recent years. Dental erosion is the chemical loss of dental hard substances caused by exposure to acids not derived from oral bacteria. Mechanical forces from, for example, the tongue, the cheeks or toothbrushing, increase loss of partly-demineralized tooth surfaces and the cumulative loss of dental hard tissue is defined as erosive tooth wear (ETW). Dental hard tissue losses which occur because of very frequent acid exposure, such as through increased vomiting, but without mechanical stress, are also assigned to tooth erosion. Without prior softening, practically no loss of enamel takes place due to abrasion with the modern Western diet. The present work is a continuation of earlier work. A total of 226 beverages, food, stimulants as well as medicines and mouthwashes were tested for their erosive potential on premolars and deciduous molars covered with a human pellicle. The influence of temperature, phosphate and calcium was also investigated in additional experiments. The change in hardness before and after immersion in the respective test substance was measured and the erosive potential was classified. For each test product, we determined pH and other properties which were possibly related to erosive potential. There were considerable and sometimes surprising differences between the tested products. The addition of phosphate did not influence the erosive potential of the liquids, but calcium did. A modified erosion scheme is presented, which incorporates these and other new findings.

Impact of Acquired Pellicle Modification on Adhesion of Early Colonizers

New preventive approaches against dental erosion caused by acidic drinks and beverages include fortification of beverages with natural polymers. We have shown that the mixture of casein and mucin significantly improved the erosion-inhibiting properties of the human pellicle layer. This study aimed to investigate the effect of pellicle modification by casein, mucin and a casein-mucin mixture on the adhesion of early bacterial colonizers. Test specimens of human tooth enamel were prepared, covered with saliva and coated with 0.5% aqueous (aq.) casein, 0.27% aq. mucin or with 0.5% aq. casein-0.27% aq. mucin, after which the adhesion of Streptococcus gordonii, Streptococcus oralis, and Actinomyces odontolyticus was measured after incubation for 30 min and 2 h. log₁₀ colony-forming units were compared by nonparametric tests. All three bacterial strains adhered in higher number to pellicle-coated enamel than to native enamel. The protein modifications of pellicle all decreased the counts of adhering bacteria up to 0.34 log₁₀/mm², the most efficient being the casein-mucin mixture. In addition to the recently shown erosion-reducing effect by casein-mucin, modification of the pellicle may inhibit bacterial adherence compared to untreated human pellicle.

Formation and Photocatalytic Decomposition of a Pellicle on Anatase Surfaces

The acquired dental pellicle plays a critical role in the adhesion and detachment of dental plaque bacteria. It has been reported that titanium dioxide biomaterials decompose single-protein films by photocatalysis. However, it is not known whether this can also be achieved with complex structured pellicle films. This in vitro study investigated in real-time the formation and photocatalytic decomposition of human pellicle at anatase-saliva interfaces. Nanostructured polycrystalline anatase layers were deposited on titanium-coated quartz crystals by magnetron-sputtering, serving as a model for titanium implant surfaces. The quartz crystals were used as acoustic sensors in a quartz-crystal microbalance (QCM) system with dissipation. In situ UV irradiation of pellicle-covered anatase caused a statistically significant decrease of the adsorbed salivary mass. In contrast, photocatalytic decomposition of pellicle could not be observed on reference titanium surfaces. Wettability characterization revealed superhydrophilicity of anatase upon UV irradiation, whereas titanium was unaffected. XPS measurements provide further information concerning the decomposition of the salivary films. The results suggest that the photocatalytic activity of polycrystalline anatase-modified biomaterial surfaces is able to decompose complex structured macromolecular pellicle films. Therefore, this study opens the way to surface modifications supporting therapeutic approaches of biofilm removal.

Impact of Acquired Enamel Pellicle Modification on Initial Dental Erosion

The acquired enamel pellicle that forms on the tooth surface serves as a natural protective barrier against dental erosion. Numerous proteins composing the pellicle serve different functions within this thin layer. Our study examined the effect of incorporated mucin and casein on the erosion-inhibiting potential of the acquired enamel pellicle. Cyclic acidic conditions were applied to mimic the erosive environment present at the human enamel interface during the consumption of soft drinks. One hundred enamel specimens were prepared for microhardness tests and distributed randomly into 5 groups (n = 20) that received the following treatment: deionized water, humidity chamber, mucin, casein, or a combination of mucin and casein. Each group was exposed to 3 cycles of a 2-hour incubation in human saliva, followed by a 2-hour treatment in the testing solution and a 1-min exposure to citric acid. The microhardness analysis demonstrated that the mixture of casein and mucin significantly improved the erosion-inhibiting properties of the human pellicle layer. The addition of individual proteins did not statistically impact the function of the pellicle. These data suggest that protein-protein interactions may play an important role in the effectiveness of the pellicle to prevent erosion.

Characterization of the immunologic responses to human in vivo acquired enamel pellicle as a novel means to investigate its composition.

Human acquired enamel pellicle is formed by molecules selectively adsorbed onto tooth surfaces. The present work describes the use of monoclonal antibody (mAb) technology as a novel approach to identify micro amounts of components present in pellicle. MAbs were obtained with reactivities against statherin, histatin, mucous glycoprotein 1(MGI), albumin, amylase and human immunoglobulins (Igs), indicating that these are pellicle components, which was further confirmed by immunoblotting. No mAbs against proline-rich proteins (PRPs), lysozyme, mucous glycoprotein 2 (MG2), carbonic anhydrase, lactoferrin or peroxidase were obtained, suggesting that these components are absent, present in low amounts, or exhibit low antigenicity. Further characterization of the binding epitopes of some of th e obtained anti-MGO, anti-statherin and anti-histatin mAbs were carried out and the biological relevance is discussed. The results open up the possibility that immunization with human pellicle and mAbs production can be employed to identify hitherto unknown constituents of pellicle.