Scientists in Germany have charted the differences in erosive behaviour in teeth from humans, horses and cattle.
Susann Hertel and her fellow researchers set out to systematically investigate the demineralisation behaviour of the enamel and dentin in human, bovine and equine teeth.
They also sought to determine for the first time the protective effect of pellicles on enamel and dentin under erosive conditions. The pellicle is a protein film that forms on the surface of teeth by selective binding of glycoproteins from saliva.
It normally forms seconds after a tooth is cleaned, or after chewing. It protects teeth from acids produced by oral microorganisms after consuming carbohydrates.
In the study, enamel and dentin, both with and without pellicle formation, were exposed to hydrochloric acid for 120 seconds to gauge the erosive effects.
The researchers, reporting in the journal Scientific Reports, also employed scanning electron microscopy and transmission electron microscopy to compare tooth structure and erosion characteristics, and to learn more about the formation and structure of the pellicle.
The teeth from cattle were obtained from a slaughterhouse, those from horses from the Institute of Veterinary Anatomy, Histology and Embryology at Justus Liebig University, and the human teeth, both primary and permanent, from extractions undertaken at the dental clinic of the University Hospital of Dresden, Germany.
In general, bovine enamel and dentin showed the highest degree of erosion after acid exposure compared to human and equine samples.
Erosion of human primary enamel tended to be higher than that of permanent teeth, whereas dentin showed the opposite behaviour.
Scanning electron microscopy showed that eroded equine dentin appeared more irregular than human or bovine dentin. Transmission electronic microscopy showed that primary enamel appeared most susceptible to erosion.
The researchers, discussing their findings, said the demineralisation behaviour of the enamel and dentin of bovine, human and equine teeth with and without protective pellicles was compared for the first time using highly sensitive methods.
This provided reference data for future studies of demineralisation behaviour, and allowed the study team to determine whether bovine and/or equine teeth are suitable alternatives to human dental hard tissues in the study of tooth erosion.
They said several factors must be taken into account.
“Firstly, it is important that the general elemental composition is similar. A previous study has shown that the composition of bovine and human teeth is similar, particularly in terms of calcium and phosphate content. Another study also suggested similar elemental levels of calcium and phosphate in the dentin of human and equine teeth.”
Another issue is the availability and consistency of tooth material.
“Bovine teeth are readily available as a by-product of abattoirs. Cattle are fed a uniform diet, are exposed to the same environmental conditions and the teeth obtained from the animals are of a similar age.
“Horse teeth, on the other hand, are less readily available because the animals are not slaughtered at a specific age by default. Therefore, the availability of equine teeth is less predictable and the age of the animals varies widely.
“Last but not least, the anatomical peculiarities of equine teeth should also be taken into account, as there is a complex arrangement of enamel-dentine cement structures and post-eruptive maturation of the outer enamel.”
It is not uncommon, they said, for incisor crowns in horses to be curved and for the enamel to be covered with a layer of cementum, unlike human and bovine enamel.
“According to our data, the erosive properties of equine teeth are closer to those of human teeth than those of bovine teeth, although the relative differences are comparable.”
The findings therefore suggest that both bovine and equine teeth are good substitutes for human teeth, especially since the differences in calcium and phosphate release in the enamel of human and bovine teeth are no longer statistically significant after the formation of the 30-minute pellicle.
“As mentioned above, a major advantage of bovine teeth is their relative uniformity with respect to age and diet. It is important to note, however, that we had a small sample size, which is common in basic dental research and yet provides important insights into biological conditions.”
The authors said the availability of human teeth is limited as they are mostly obtained from routine tooth extractions as part of dental treatment. As a result, donor age, diet and fluoride intake are highly variable, and tooth extraction is often due to decay. In addition, only small samples can be obtained from human teeth.
“In conclusion, bovine enamel appears to be somewhat more susceptible to erosive processes, which should be taken into account in future studies. Nevertheless, due to its availability and uniformity compared to equine teeth, it is a good alternative to human tooth specimens for in situ studies.”
Hertel, S., Basche, S., Schmidt, V. et al. Erosion behaviour of human, bovine and equine dental hard tissues. Sci Rep 13, 19617 (2023). https://doi.org/10.1038/s41598-023-46759-9
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