Alix Young

The protective effect of TiF4, SnF2 and NaF against erosion-like lesions in situ.

The aim of this in situ study was to compare the protective effect of TiF4, SnF2 and NaF on the development of erosion-like lesions in human enamel. Fourteen human molars were each divided into 4 specimens, mounted on acrylic mouth appliances and worn by 7 volunteers for 9 days. In order to mimic a feasible treatment procedure for patients with voluntary or involuntary gastric reflux, the specimens were etched for 2 min twice a day (0.01 M HCl) and fluoride applications were performed every third day (2 min). The controls were treated as the other specimens except for the fluoride applications. Etch depths and surface roughness changes (Rq) were measured by white light interferometry. Compared with the control, TiF4 and SnF2 reduced the etching depth by 100% (p < 0.001) and 91% (p < 0.001), respectively, and both treatments resulted in an observable surface layer. NaF had no significant protective effect (p = 0.46). It can be concluded that although SnF2 provided significant protection for the enamel surfaces, TiF4 showed the best protection against acid attack, while NaF had no significant protective effect in this study.

Initial Erosion Models

Initial dental erosion – the very first tooth surface changes caused by short-term acidic exposures before any tissue loss is observed – has been studied using in vitro and in situ/in vivo protocols. This paper describes the events that should be considered when modelling initial erosion, the available protocols and their strengths and limitations. In vitro initial erosion models can provide relevant information about the erosive outcome. However, the published studies vary considerably regarding the erosive parameters used, and few of these studies have been validated. On the other hand, relevant in situ/in vivo studies are available that have studied the effect of salivary pellicle and preventive treatments on initial erosion, as well as the changes in salivary pH following exposure to acid solutions. Guidelines for good methodology in modelling initial erosion are proposed.

The erosion-inhibiting effect of TiF4, SnF2, and NaF solutions on pellicle-covered enamel in vitro

Objective. The aim of this study was to compare the protective effect of TiF4, SnF2, and NaF treatment on the development of erosion-like lesions in pellicle-covered human enamel. Material and Methods. Twelve human molars were each divided into 5 specimens, 4 of which were immersed in saliva for 2 h. Three pellicle-covered specimens from each tooth were treated with a TiF4, SnF2, or NaF solution (all 0.5 M F) for 2 min. Control specimens, one with and one without pellicle, were included. Immersion in acid (0.01 M HCl) was carried out stepwise (2+2+2+2 min). The etching depths (in µm) were measured using white light interferometry. Results. Compared with the control with pellicle, TiF4 reduced enamel loss by 100% after 2 min and by 24% after 8 min of acid exposure. The corresponding values for SnF2 were 45% and 14%. NaF provided no significant protection of the surface. The pellicle-covered specimens showed reduced lesion depths after 6 and 8 min compared to the controls without pellicle. Conclusions. TiF4 gave the best protection against acid attack. SnF2 provided significant protection only after 2 min of acid exposure, while NaF had no significant protective effect.

An in vitro study on the effect of TiF(4) treatment against erosion by hydrochloric acid on pellicle-covered enamel.

The aim of this in vitro study was to examine the effect of fluoride treatment on pellicle-covered enamel exposed to an acidic challenge simulating gastric reflux. Sixteen bovine and 16 human teeth were sectioned into four pieces, divided into four groups: (1) control, (2) 2-hour pellicle, (3) TiF4, and (4) 2-hour pellicle + TiF4, and subsequently subjected to 3 ml 0.01 M HCl stepwise for 4 + 4 + 4 min. The acid was analysed for calcium by atomic absorption spectroscopy. TiF4 reduced Ca release from enamel by 76, 57 and 56% following the 4 + 4 + 4-min acid exposures, respectively, in bovine and 44, 54 and 54% in human enamel. These results suggest that treatment of enamel with a TiF4 solution, with or without pellicle removal, may provide protection for the enamel against acid attack.

The role of fluoride in erosion therapy

The role of fluoride in erosion therapy has long been questioned. However, recent research has yielded positive results. In this chapter, an overview of the literature is provided regarding the application of fluorides in the prevention and treatment of erosion and erosive wear. The results are presented and discussed for different fluoride sources such as monovalent and polyvalent fluorides, and for different vehicles such as toothpastes, solutions and rinses, as well as varnishes and gels. It is concluded that fluoride applications are very likely to be of use in the preventive treatment of erosive wear. Most promising are high-concentration, acidic formulations and the polyvalent fluoride sources, with the best evidence available for stannous fluoride. However, the evidence base for clinical effectiveness is still small.

Zeta Potentials of Human Enamel and Hydroxyapatite as Measured by the Coulter® DELSA 440

The zeta potential of human enamel is of physiological importance for interactions between enamel surfaces and the surrounding aqueous medium of saliva. The zeta potentials of both enamel and hydroxyapatite (HA) have been examined previously by various techniques. In this study, we examined the zeta potential of human enamel and HA using the Coulter® DELSA 440, which, by a laser, makes independent Doppler shift measurements of moving particles in an electric field at 4 different angles, providing advantages over previous techniques. The enamel and HA particles were suspended directly in different phosphate buffers, or first incubated for 2 hrs in parotid (PS) or whole saliva (HWS) and then suspended in the same buffers. The enamel and HA particles exhibited an overall net surface potential of -15 to -30 mV, depending on the buffer content. Incubation in PS and HWS gave less negative potentials of -8 to -14 mV. In our previous studies, the salivary micelle-like structures (SMSs), seen in TEM of parotid saliva, were observed to have a zeta potential of -9 mV (Rykke et al., 1996). The zeta potential determinations in this study support the concept of an adsorption of mostly SMSs to the enamel surfaces, with a change of the zeta potential of the enamel and HA toward that of the SMSs.

Fluoride release and uptake in vitro from a composite resin and two orthodontic adhesives

The aim of this study was to investigate the fluoride release and uptake characteristics of a composite resin (Tetric) and two orthodontic adhesives (VP 862 and Saga Bond), with a type-II glass ionomer cement (Ketac Fil) as a control. Test specimens in 2 ml deionized water released fluoride over a period of 33 days. Ketac Fil released 54 and 15 times more fluoride than Tetric after 24 h and 1 month, respectively, whereas the two adhesives released amounts between these values. Specimen exposure to 1000-ppm NaF solution increased the 24-h fluoride release from all materials, with near pre-exposure levels reached after 2-3 days. Ketac Fil had a tendency to recharge not seen with the other materials. The ytterbium trifluoride filler in Tetric has a very low water solubility, and it is therefore suggested that the increases in fluoride release from Tetric after exposure to fluoride were most probably due to release of surface-retained fluoride.

Current erosion indices--flawed or valid? Summary

The problem of erosive tooth wear appears increasingly to be encountered by clinicians and researchers. An adequate way of defining and recording erosive tooth wear is essential in order to assess the extent of this clinical phenomenon, both on an individual level and in the population, and for the adequate provision of preventive and therapeutic measures. Well-established erosion indices have been used in most of these studies, although in many cases modifications have been made to suit the different research aims. This use of different indices is one reason why it still cannot be claimed that there is enough current knowledge on this clinical phenomenon. This article summarises the proceedings of a workshop to discuss the topic of dental erosion indices. The result of the workshop is the proposal for a new scoring system (Basic Erosive Wear Examination, BEWE) designed for use both within the research field and for dental clinicians, with the aims of standardising assessment of erosion for international comparisons, raising awareness and providing guidelines for treatment of erosive tooth wear in dental practice.

The Effects of Acidic Fluoride Solutions on Early Enamel Erosion in vivo

Acidic fluoride solutions may reduce dental erosion. The aim of this study was to compare the effect of different acidic fluoride solutions on enamel dissolution using an established in vivo model. When possible 4 anterior teeth (255 teeth in a total of 67 subjects) were isolated and exposed to 0.01 M citric acid. The acid was collected in test tubes before (etch I) and 5 min after (etch II) application of test fluoride preparations. Acidic fluoride solutions (pH range 1.5–2.9), i.e. SnF2, TiF4 and hydrogen fluoride (HF) (all approx. 0.1 M F), HF (0.027, 0.055, 0.082 M F) and neutral NaF solution (0.1 M F) as control were applied to the labial surfaces of the teeth for 1 min (6 ml/min). Enamel dissolution was examined by chemical analysis of calcium content in the citric acid etch solutions using atom absorption spectrometry. The change in calcium concentration (ΔCa) and the percentage of mean calcium reduction were calculated from the difference in calcium loss between etch I and etch II. Statistical analysis was carried out using the Wilcoxon signed rank test and Kruskal-Wallis tests with Dunn’s multiple comparison. Results showed a mean ΔCa of 0.671 mg/l (SD 0.625) for SnF2, and ranged from 0.233 mg/l (SD 0.248) for the weakest HF solution to 0.373 mg/l (SD 0.310) for the strongest HF solution. This represented a 67% reduction in enamel dissolution for SnF2 and a 40–76% reduction for the HF solutions. No reduction was observed for TiF4 or NaF. The types of metal, pH and fluoride concentration are all important for the in vivo effect.

Quantitative and qualitative analyses of human salivary micelle-like globules

In the present study we examined the protein proportion and amino acid profile of the salivary micelle-like globules (SMGs) of human whole saliva and parotid saliva (HWS, HPS). Saliva and SMG samples from each subject (clarified HWS and HPS from 6 subjects, and unclarified HWS from 3 subjects) were analysed for amino acids using standard acid hydrolysis procedures. HPS, clarified HWS and the respective supernatant samples (remaining after removal of the SMGs) were also measured for protein using the micro-Kjeldahl method. SMGs from clarified and unclarified HWS made up 4.7% and 19.7%, respectively, of the total salivary protein based on amino acid analyses. With the micro-Kjeldahl method SMGs from clarified HWS made up 7.3% of the total saliva protein. SMGs isolated from HPS were found in only small amounts. The amino acid profile for the SMGs was strikingly similar to that known for the 2-h pellicle, and differed significantly from HWS or HPS. The results support previous morphological studies indicating that the SMGs represent a major component of the newly formed pellicle.