Thickness of acquired salivary pellicle as a determinant of the sites of dental erosion

Comparison of factors potentially related to the occurrence of dental erosion in high- and low-erosion groups

Soft drink intake, method of drinking, pH variations, plaque topography, and various salivary, microbial and clinical factors were compared in Saudi men with high (n = 10, mean = 20.5 yr) and low (n = 9, mean = 20.3 yr) dental erosion. pH-measurements were carried out with a microtouch electrode at six different intraoral locations after the subjects had consumed 330 ml of regular cola-type drink in their customary manner. The results showed that higher intake of cola-type drinks was more common in the high- (253 l yr(-1)) than in the low-erosion group (140 l yr(-1)). High erosion was associated with a method of drinking whereby the drink was kept in the mouth for a longer period (71 s vs. 40 s). pH after drinking did not differ between the groups for any of the six measuring sites. Plaque accumulation on the palatal surfaces of maxillary anterior teeth and urea concentration in unstimulated saliva were lower in high-erosion subjects. Aside from these, there were no differences in salivary and microbial factors between the groups. First molar cuppings, buccal cervical defects, and mouth breathing were more common in the high- than in the low-erosion group. In summary, consumption of cola-type drink, method of drinking, amount of palatal plaque on anterior teeth, and salivary urea concentration are factors associated with dental erosion.

Dental erosion patterns from intrinsic acid regurgitation and vomiting

BACKGROUND

The distribution of lesions from dental erosion due to intrinsic acid regurgitation and vomiting may be different from patterns of dental erosion due to extrinsic acids. To date studies have failed to validate this assumption. This study described the sites and nature of lesions from dental erosion in cases of intrinsic acid regurgitation, and compared them with the distribution of lesions occurring in age and sex matched controls, whose lesions are due to extrinsic acids.

METHODS

The University of Queensland tooth wear clinic patients were screened to select 30 cases, 21 self-identified bulimics and nine medically diagnosed chronic gastric acid regurgitators, and 30 controls. Epoxy resin models of the subjects' dentition were examined under stereoscopic light microscope at magnification 16 to 40. The patterns and sites of tooth wear were recorded for teeth representative of 20 tooth sites in every subject.

RESULTS

While the incisal edges of maxillary and mandibular anterior teeth of acid regurgitators were more frequently affected by erosion, incisal attrition was more common on controls' teeth. Cervical lesions were more commonly found in association with incisal attrition in the controls, and in association with incisal erosion in the cases. In 10 per cent of sites in case subjects, cervical lesions associated with incisal erosion were found on the lingual aspects of their mandibular incisors, canines and premolars. These lesions were almost exclusive to the case subjects.

CONCLUSIONS

These results validate that lingual cervical lesions associated with incisal erosion on the mandibular anterior teeth are strong discriminators between tooth wear in patients with bulimia nervosa or chronic gastro-oesophageal reflux and those whose dental erosion is due to extrinsic acids.

Eroded enamel lesion remineralization by saliva as a possible factor in the site-specificity of human dental erosion

The composition and flow of saliva, which determine its functions, vary within intraoral sites and among individuals. Also, the susceptibility to tooth erosion reportedly varies among individuals and within the dental arches. A possible effect of saliva on early-eroded lesions may be a contributory factor. The aims here were firstly to determine the remineralization of eroded enamel lesions by saliva, and secondly to investigate any variation of this remineralization within the dental arches and among individuals. Early enamel erosion was produced on human premolars using orange juice. Control sections and two test slabs were cut from each tooth. The two slabs from the same lesion were bonded with composite resins to the palatal surface of upper right lateral incisor teeth and the lingual surface of the lower right lateral incisor teeth of volunteers, who then chewed a sugar-free gum four times daily. After 28-day intraoral exposure, mineral loss (DeltaZ) and lesion depth (ld) were quantified using microradiography and the data analysed by paired t-test (n=10, alpha=0.05). Mean DeltaZ was significantly lower in the group of slabs positioned palatally (P<0.001) and lingually (P<0.001) when compared with the control group, and in the lingually placed group when compared with the palatally positioned (P<0.01). A significantly lower ld was observed in the group of slabs positioned palatally (P<0.05) and lingually (P<0.001) when compared with the control group, and in the lingually positioned group when compared with the palatally placed (P<0.05). It was concluded that saliva can remineralize early enamel erosion, and that the degree of remineralization varies within intraoral sites and may be responsible for the differing susceptibility to erosion within the dental arches.

Electron-microscopic demonstration of proline-rich proteins, statherin, and histatins in acquired enamel pellicles in vitro

Proline-rich proteins (PRPs), histatins, and statherin are salivary proteins that exhibit high affinities for hydroxyapatite surfaces. In vitro experiments with parotid submandibular/sublingual or whole saliva have shown these proteins to adsorb selectively to tooth surfaces. This investigation focuses on the histo-morphological identification of PRPs, histatins, and statherin in acquired enamel pellicles. Synthetic hydroxyapatite or bovine enamel were exposed to glandular secretions, and whole saliva and pellicle precursor proteins were identified immunohistologically by electron microscopy. Results obtained by back-scattered scanning electron microscopy showed these proteins to be present in pellicles. Pellicles displayed a distinct structure consisting of a sponge-like meshwork of microglobules. Interconnections between structural elements were identified in submandibular/sublingual and whole saliva pellicles only. Transmission electron microscopy of pellicles formed on bovine enamel surfaces revealed a tendency for preferential localization of precursor proteins within the protein film. Since the data showed the presence of pellicle precursors in pellicles derived both from glandular secretions and from whole saliva, it is likely that PRPs, histatins, and statherin are integral components of acquired enamel pellicles in vivo.

Saliva and dental pellicle--a review

The acquired enamel pellicle is an organic film covering the surfaces of teeth. When this film was first discovered, it was thought to be of embryologic origin. Only in the middle of this century did it become clear that it was acquired after tooth eruption. Initially, the small amounts of material that could be obtained have virtually limited the investigation of pellicle proteins to amino acid analysis. Nevertheless, this technique revealed that the pellicle is mainly proteinaceous and is formed by selective adsorption of salivary proteins on tooth enamel. Later, immunologic techniques allowed for the identification of many salivary and fewer non-salivary proteins as constituents of pellicle. However, to this date, isolation and direct biochemical characterization of in vivo pellicle protein have not been possible, because only a few micrograms can be obtained from a single donor. Therefore, the composition and structure of the acquired enamel pellicle are still essentially unknown. Information on the functions of pellicle has been obtained mainly from in vitro experiments carried out with saliva-coated hydroxyapatite and enamel discs. It was found that pellicle protects enamel by reducing demineralization upon acid challenge. Improved pellicle harvesting procedures and analysis by state-of-the-art proteomics with mass spectroscopy approaches promise to make major inroads into the characterization of enamel pellicle.