Effect of various Ca2+/PO4(3-) concentrations of linseed-based saliva substitutes on enamel in vitro

Phosphoryl oligosaccharides of calcium enhance mineral availability and fluorapatite formation

OBJECTIVES

Phosphoryl oligosaccharides of calcium (POs-Ca) are a highly soluble calcium source and can keep the solubility of calcium and fluoride ions. The aim of this study was to investigate the effect of calcium (from POs-Ca) and fluoride ions penetrate into subsurface enamel lesions in vitro.

DESIGN

Demineralized bovine enamel slabs were remineralizedin vitro for 24 h at 37 °C with artificial saliva (AS) containing POs-Ca and various fluoride concentrations (0-100 ppm), or AS containing different levels of POs-Ca adjusted to a Ca/P ratio of 0.4-3.0 and fluoride, then were analyzed using Transversal microradiography. From those results, remineralization effects with optimal conditions were compared between POs-Ca and calcium chloride (CaCl₂). To determine the form of incorporated fluoride, we analyzed the chemical state and local structure of fluorine atoms integrated into enamel subsurface lesions using micro X-ray absorption near-edge structure (μ-XANES) spectroscopy.

RESULTS

A significant mineral recovery rate was observed with POs-Ca and fluoride at 0.5 or 1.0 ppm (n = 6, p < 0.05), as well as a Ca/P molar ratio of 1.67 (n = 5, p < 0.05). Under those conditions, the mineral recovery rate of AS containing POs-Ca (37.9 ± 7.3%) was significantly greater than that of CaCl₂ (15.0 ± 9.6%) (n = 5, mean ± SD, p < 0.05). μ-XANES spectra analysis of the samples indicated that the dominant form of fluorine atoms in enamel subsurface lesions was fluorapatite.

CONCLUSIONS

POs-Ca with fluoride-derived diffusion into subsurface enamel lesions facilitated formation of fluorapatite phases.

Prevention of erosive tooth wear: targeting nutritional and patient-related risks factors

This article provides an overview of the nutritional and patient-related risk factors involved in the aetiology of erosive tooth wear (ETW) and the preventive strategies to counteract them. The first step is to diagnose clinical signs of ETW and to recognise causal factors. Low pH and high buffer capacity of foods/drinks are the major risk factors, while the calcium concentration is the main protective factor. Reduction of frequency of consumption and contact time of erosive foods/drinks with the teeth, use of straws appropriately positioned and consumption of dairy products are advisable. Oral hygiene has a role in the development of ETW, however, postponing toothbrushing is not clinically advisable. In cases of drug abuse, chronic alcoholism, GERD or bulimia, the patient must be referred to a doctor. Immediately after vomiting, patients might be advised to rinse the mouth. Saliva has an important protective role and patients with reduced salivary flow can benefit from the use of chewing gum. Recent studies have focused on improving the protective capacity of the acquired pellicle as well as on the role of protease inhibitors on dentine erosion. However, the degree of evidence for these preventive measures is low. Clinical trials are necessary before these measures can be recommended.

Optimization of calcium concentration of saliva with phosphoryl oligosaccharides of calcium (POs-Ca) for enamel remineralization in vitro

OBJECTIVE

Phosphoryl oligosaccharides of calcium (POs-Ca) are highly soluble calcium source made from potato starch. The aim of this study was to investigate the optimal concentrations of POs-Ca for the remineralization of subsurface enamel lesions in vitro.

DESIGN

Demineralized bovine enamel slabs (n=5) were remineralized in vitro for 24h at 37°C with artificial saliva (AS) containing 0-0.74% POs-Ca to adjust the Ca/P ratio to 0.4-3.0, then sectioned and analysed by transversal microradiography (TMR). The data were analysed by Scheffe's post hoc test. The Ca/P ratio with most remineralization was used to investigate the effect of calcium on enamel remineralization (n=11). The demineralized slabs were treated with AS with calcium-chloride- (CaCl2-) or POs-Ca with an identical calcium content, and sectioned for TMR and wide-angle X-ray diffraction (WAXRD) analyses to evaluate the local changes in hydroxyapatite (HAp) crystal content. The data were analysed using the Mann-Whitney U-test.

RESULTS

The highest mineral recovery rate resulted from addition of POs-Ca to adjust the Ca/P to 1.67. At this ratio, the mineral recovery rate for AS containing POs-Ca (24.2±7.4%) was significantly higher than that for AS containing CaCl2 (12.5±11.3%) (mean±SD, p<0.05). The recovery rate of HAp crystallites for AS containing POs-Ca (35.7±10.9%) was also significantly higher than that for AS containing CaCl2 (23.1±13.5%) (p<0.05). The restored crystallites were oriented in the same directions as in sound enamel.

CONCLUSIONS

POs-Ca effectively enhances enamel remineralization with ordered HAp at a Ca/P ratio of 1.67.

Insights into preventive measures for dental erosion

Dental erosion is defined as the loss of tooth substance by acid exposure not involving bacteria. The etiology of erosion is related to different behavioral, biological and chemical factors. Based on an overview of the current literature, this paper presents a summary of the preventive strategies relevant for patients suffering from dental erosion. Behavioral factors, such as special drinking habits, unhealthy lifestyle factors or occupational acid exposure, might modify the extent of dental erosion. Thus, preventive strategies have to include measures to reduce the frequency and duration of acid exposure as well as adequate oral hygiene measures, as it is known that eroded surfaces are more susceptible to abrasion. Biological factors, such as saliva or acquired pellicle, act protectively against erosive demineralization. Therefore, the production of saliva should be enhanced, especially in patients with hyposalivation or xerostomia. With regard to chemical factors, the modification of acidic solutions with ions, especially calcium, was shown to reduce the demineralization, but the efficacy depends on the other chemical factors, such as the type of acid. To enhance the remineralization of eroded surfaces and to prevent further progression of dental wear, high-concentrated fluoride applications are recommended. Currently, little information is available about the efficacy of other preventive strategies, such as calcium and laser application, as well as the use of matrix metalloproteinase inhibitors. Further studies considering these factors are required. In conclusion, preventive strategies for patients suffering from erosion are mainly obtained from in vitro and in situ studies and include dietary counseling, stimulation of salivary flow, optimization of fluoride regimens, modification of erosive beverages and adequate oral hygiene measures.

Saliva substitutes for the treatment of radiation-induced xerostomia--a review

GOAL

The aim of this review is to summarize the in vitro and in vivo evidence on the performance of contemporary saliva substitutes in the treatment of xerostomia and hyposalivation caused by radiation therapy for head and neck malignancies.

METHODS

A literature search was conducted during July to September 2008 in PubMed, using the query terms "saliva substitute", "saliva substitute and xerostomia", "artificial saliva", and "artificial saliva and xerostomia"; for clinical studies, only studies in patients suffering from radiation-induced xerostomia have been included in the review.

RESULTS AND CONCLUSION

Fifty-two studies met the inclusion criteria and were allotted either to the in vitro topics "viscosity", "lubrication", "wetting properties", "antimicrobial effects", and "enamel and dentin de- and remineralization", or to the in vivo topics "clinical acceptance" or "influence on plaque formation and oral mucosa and microflora". The findings suggest that there are significant differences in the performance of various saliva substitutes concerning the review parameters, yet indicate that further in vitro and in vivo studies on the properties of saliva substitutes are necessary.

The efficacy of Xialine in patients with Sjögren's syndrome: a single-blind, cross-over study

Sjögren syndrome (SS) is a chronic inflammatory autoimmune disease of unknown cause whose main characteristic is severe dryness of the eyes and the mouth. The decreased functional capacity of the lacrimal and salivary glands which is the result of the inflammatory process and lymphocytic infiltration observed in SS is accountable for this complication. Twenty-nine patients with SS whose ages were ranging between 24-77, who were under treatment in Ege University Faculty of Medicine Department of Rheumatology, participated in the study, and their informed consents were obtained upon enrollment. Each patient recorded their subjective complaints on a separate questionnaire. The baseline and subsequent evaluation of the subjective findings on predetermined times (1 h after application of the material, at the end of the 1st, 7th, and 14th days) were also recorded on separate questionnaire sheets. Throughout the 14-day treatment period, no statistically significant differences were noted between the Xialine and placebo groups with regard to burning tongue, diminished taste, and waking up at night to sip water (p = 0.925, 0.527, and 0.066, respectively). However, patients' satisfaction with placebo decreased by 25.63% at the end of the test period, whereas it increased by 16.37% after Xialine administration. Overall, the patients preferred Xialine at the end of the study (p = 0.011). The main motive to administer saliva substitute is to improve lubrication and hydration of oral tissues. The results of this study indicated that Xialine is helpful in the management of xerostomia-related symptoms of SS patients. However, further investigations in larger scale group of patients are recommended to provide the effects of these agents on various complaints of xerostomia.

Effect of various calcium/phosphates ratios of carboxymethylcellulose-based saliva substitutes on mineral loss of bovine enamel in vitro

OBJECTIVES

The present study evaluated the effects of various calcium and phosphate concentrations and ratios of carboxymethylcellulose (CMC)-based solutions on the mineral loss of predemineralised bovine enamel in vitro.

METHODS

Bovine enamel specimens were prepared, polished and partly covered with nail varnish, thus serving as control of sound enamel. After demineralisation (37 degrees C; pH 5.0; 14 days) the specimens were exposed to CMC-based solutions (20g/l) with various saturations with respect to apatites containing 0.1mM NaF, CaCl2 (0-32 mM) and KH2PO4 (0-52 mM) at two different pH values (5.5 or 6.5). A fluoride-free solution served as control, and four commercially available products were tested as well. The differences in mineral loss (DeltaDeltaZ) between the values prior to (DeltaZ Demin) and after storage (DeltaZ Effect) in the various solutions were evaluated from microradiographs of thin sections (100microm).

RESULTS

The general linear model revealed a significant dependency for DeltaDeltaZ on 'calcium' (p<0.001), 'phosphate' (p=0.023), 'fluoride' (p=0.002) and 'pH' (p<0.001). With increasing calcium and phosphate concentrations an increase in DeltaDeltaZ could be observed up to the solution containing the third highest saturation with respect to octacalciumphosphate (3.2), showing a significant remineralisation (p<0.05; t-test). The commercially available products as well as the control groups revealed significantly reduced DeltaDeltaZ values compared to this group (p<0.01; Bonferroni).

CONCLUSIONS

A saturation with respect to octacalciumphosphate of 3.2 and a pH of 6.5 enables CMC-based solutions to remineralise bovine enamel in vitro.

The Effect of Bleaching on the Elastic Modulus of Bovine Enamel

The purpose of this study was to determine the elastic modulus of enamel during bleaching procedure with the use of an ultrasonic device. Enamel sections were obtained from freshly extracted bovine incisors. Specimens were exposed to 10% carbamide peroxide for two hours, followed by an application of a fluoride-containing toothpaste for five minutes and stored in artificial saliva (pH 7.0). An ultrasonic device was used to measure the sound velocities of longitudinal and shear waves as well as elastic modulus. The mean elastic modulus of bleached enamel decreased with time, from 15.5 GPa to 10.1 GPa. Conversely, the elastic modulus of bleached enamel followed by application of a fluoride-containing toothpaste increased with time, from 15.2 GPa to 20.2 GPa. Results of this study indicated that a decrease in elastic modulus associated with bleaching occurred, and that fluoride-containing toothpaste reversed this effect.