The production of subsurface artificial caries lesions on third molar teeth.
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Adult↗
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Results for “Tooth Demineralization”
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Identification of human serum albumin in human caries lesions of enamel: the role of putative inhibitors of remineralisation.
Carious attack on enamel is not a unidirectional process but involves both demineralisation and remineralisation. The chemistry of carious attack on enamel has, to a large extent, now been clarified as far as mineral components are concerned but little attention, however, has been paid to the identity of organic material in carious lesions and its possible role in the caries process. The only clear information available is that organic material accumulates with time within enamel lesions. The present study was aimed at identifying a specific protein component known to bind to hydroxyapatite (albumin) in carious lesions with a view to investigating its role in the disease process. The distribution of albumin within both white spot and fissure lesions and adjacent sound enamel of extracted human teeth was investigated using SEM immunohistochemistry on undermineralised sections of human enamel and employing a polyclonal antibody to human serum albumin. The nature of the protein, i.e. whether it was in the form of intact molecules or degraded fragments, was investigated by Western blotting, employing the same antibody. The immunohistochemistry revealed the presence of albumin within both interproximal white spot and fissure lesions with little if any present in sound enamel. The Western blotting indicated that the albumin was in the intact form with no evidence of degradation products. The ability of albumin to bind and to inhibit growth of calcium phosphate crystals raises the question as to the possible role of such a molecule in the development of carious lesions.
Antibodies↗
Efficacy of sterilisation methods and their effect on enamel demineralisation.
The aim of this project was to determine the effectiveness of sterilisation methods for dental enamel for use in intra-oral cariogenicity tests, and their possible effect on the degree of demineralisation of enamel. Bovine incisors were cut vertically into five portions and each assigned to one of five groups. Group 1 was used as a control while the other four groups were subjected, respectively, to gamma irradiation ( congruent with 25kGy), steam autoclaving (121 degrees C for 15 min), sodium hypochlorite (12% w/v for 24h) and povidone-iodine (7.5% w/v for 24h). Total viable counts of microorganisms remaining following sterilisation of the specimens were performed following incubation of the specimens for 24h at 37 degrees C. Caries-like lesions were produced in each specimen using an acidic buffer solution (pH4.5). Sections were cut from each specimen, ground to 80-microgram thickness, and microradiographed. Mineral loss and lesion depth were quantified using transverse microradiography. Statistical analysis was by ANOVA. Dunnett's and Tukey's tests. Microbial growth (Staphylococcus aureus and bacilli) was observed only in control specimens in both brain heart infusion broth and on blood agar plates. The sterilisation methods affected the enamel surface as follows: gamma irradiation (cream discolouration), NaOCl (bleaching), and povidone-iodine (white spot-like lesion). Compared with the control, there was no significant difference in mineral loss and lesion depth with any of the groups, but the numerical values of mineral loss and lesion depth in groups can be ranked as follows: gamma irradiation <povidone-iodine <control <autoclave <NaOCl. In conclusion, the four sterilisation methods were all effective to sterilise enamel, but gamma irradiation proved the most acceptable method for enamel to be used in cariogenicity tests having the least adverse effect.
Acids↗
The remineralization of EDTA-treated human dentine.
The remineralization of whole human dentine treated with a neutral EDTA solution was investigated: the treatment periods were 15, 30 and 120 min. From the literature it is known that EDTA removes noncollagenous proteins (NCPs) from dentine powders. In order to extract more phosphoproteins from dentine lesions, in part of this work samples were also treated with 1 M NaCl or 4 M guanidine chloride solutions. All the dentine samples after the treatments mentioned were immersed subsequently in a remineralizing solution without fluoride for 2 weeks and microradiographed. To investigate the effects of fluoride, samples treated with EDTA for 120 min were also remineralized with 2 ppm fluoride in solution. The results presented show that: (1) Measurable remineralization did not occur when fluoride was free in the remineralizing solution. Because remineralization occurred neither at the lesion front nor in the nonmineral part of the surface-softened tissue, presumably the NCPs (inhibitors) of underlying dentine diffused into the tissue during the remineralization period. (2) 2 ppm fluoride caused remineralization at the lesion front. In this case we assume fluoride either acted as nucleating agent or overcame the NCP effects at the lesion front.
Analysis of Variance↗
A Raman spectroscopic investigation of dentin and enamel structures modified by lactic acid.
Confocal Raman microspectrometry allows a thorough molecular analysis of mineralised dental tissues. The output information is provided in the form of curves representing the intensity of the signal according to the frequency, and its mathematical exploitation permits all sorts of comparative and quantitative analyses. By this process, we investigated the in vitro action of lactic acid on enamel and dentin from human permanent teeth. Modifications due to the acidic attack essentially concern phosphate grouping PO(4)(3-), which represents the mineral phase in enamel and dentin (hydroxyapatite): on Raman spectra, changes in intensity of the PO(4)(3-) band are linked to the type of dentin, to its anatomical location, and to the age of the subject. The variability of the dentinal chemical structure was confirmed by a quantitative statistical analysis, revealing a significant spectral difference between coronal and root dentin.
Adult↗
Ultrasonication as a method to study enamel demineralisation during acid erosion.
The aim of this study was to use ultrasonication as a method to measure subsurface demineralisation of enamel. Polished human enamel samples with surface profiles within +/-0.3 microm were divided into 6 groups of 10 specimens. The groups of specimens were exposed to 0. 3% citric acid (pH 3.2) for 30 min, 1, 2, 3 or 4 h. The depths of the resulting lesions were measured using a profilometer. A control group was stored in water for 4 h. Ultrasonication in water was performed on the specimen groups for 5, 30, 120, 240 and 480 s with profilometric measurements at each time point. The depth of the erosion increased linearly with the exposure time. Most of the additional loss of enamel occurred with the 5-second ultrasonication. The 30-min and 1-hour erosion lesions were further deepened by approximately 1 microm with 5 s of ultrasonication. The 2-, 3- and 4-hour lesions were deepened by 2-4 microm with 5 s of ultrasonication. There were no changes in the control group. It is concluded that ultrasonication removed softened enamel from the surface of the eroded enamel. Ultrasonication together with accurate measurement of lesion depth by profilometry offers a useful method for studying the depth of enamel softening associated with erosion.
Analysis of Variance↗
In situ acid resistance of in vivo formed white spot lesions.
Thin sections of natural enamel lesions, so-called white spots (WS), and areas of sound enamel (SEn) adjacent to the WS were exposed to an intraoral environment for 2 weeks. Thin sections of WS samples, clamped in a PMMA holder, were microradiographed before and after exposure to intraoral conditions. Acid resistance was evaluated by lesion depth and mineral changes during the cariogenic challenge. The results show that there were statistically significant differences in lesion depth, mineral loss and mineral volume percent at the surface before and after the intraoral cariogenic challenge at least at p<0.05, except for a change in mineral volume percent at the surface of WS samples. This exception indicates that no mineral change occurred in the surface layer of WS. The fact of 2.8 and 1.8 times higher ratios of SEn over WS of mean changes in lesion depth and mineral loss data, respectively, seems to indicate a quantitative difference in acid resistance level of WS lesions compared with the areas of SEn. Regarding the site of mineral changes, a distinctive feature of WS samples is that mineral loss occurs at the bottom of lesions. In contrast, areas of SEn produce a typical subsurface type of lesions. From this in situ study, it can be concluded that the surface of WS samples was apparently much more acid-resistant (at least approximately 2 times) than the areas of SEn that received a similar intraoral acid challenge.
Acids↗
The use of ultrasonication to study remineralisation of eroded enamel.
The aim of this study was to use ultrasonication and profilometry as methods to study de- and remineralisation of citric acid-eroded enamel at different pH values. Seventy-eight polished human enamel samples were divided into three test and three control groups of 13 specimens each. Three specimens of each group were chosen for SEM examination. The samples were exposed to 0.3% citric acid at pH 2.54, 3.2 or 4.5 for 2 h. The depths of the resulting lesions were measured by profilometry. The test groups were placed in artificial saliva and the control groups were stored in saline (0.9% NaCl) for 24 h and new profiles recorded. Finally all specimens were ultrasonicated in water for 5, 30, 120, 240 and 480 s with profilometric measurements at each time point. Ultrasonication of the test groups after remineralisation showed little effect on the lesion depth, whereas the control groups had an enamel loss of 2.1 microm at pH 2.54, 2.9 microm at pH 3.2 and 0.4 microm at pH 4.5 after 30-second ultrasonication. These differences from respective test groups were statistically significant at pH 2.54 and 3.2 but not at pH 4.5. Ultrasonication of control pH 2.54 and 3.2 specimens removed an amorphous covering layer to reveal a flattened surface with prisms outlined by prism boundaries. It can be concluded that remineralisation in artificial saliva stabilises the surface softened enamel against ultrasonication.
Analysis of Variance↗
Effectiveness of two fluoridation measures on erosion progression in human enamel and dentine in vitro.
The aim of the present study was to evaluate the effect of fluoride on the progression of erosive demineralisation in human enamel and dentine using a cyclic de- and remineralisation model in vitro. The mineral content expressed in micrometres was determined daily by longitudinal microradiography (LMR) and presented as cumulative mineral loss over 5 days. For erosive demineralisation, all samples were immersed in 0.05 M citric acid (pH 2.3) for 6x10 min/day and stored in a remineralisation solution. Fluoridation measures were performed as follows: group 1: control, no fluoridation; group 2: toothpaste fluoridation 3x5 min/daily (NaF, 0.15% F-); group 3: toothpaste fluoridation as group 2 and additionally application of a fluoride mouthrinse (Olaflur/SnF2, 0.025%F-) 3x5 min/daily and on days 1 and 3 gel fluoridation (Olaflur/NaF; 1.25% F-) for 1x5 min. After the first experimental day, no significant differences were found between the groups. However, after 5 days the erosive mineral loss values for enamel were 147.5+/-18.7 microm in the control group, 128.1+/-15.0 microm in group 2 (p< or =0.05) and 116.1+/-12.4 microm in group 3 (p< or =0.001). In dentine, the respective values were 136.7+/-16.4, 111.8+/-26.9 (p< or =0.001) and 60.3+/-17.8 (p< or =0.001). The intensive fluoridation significantly reduced erosion progression in enamel but had a more pronounced effect on dentine. The results suggest that subjects with erosive lesions should use an intensive fluoridation measure.
Analysis of Variance↗
How to measure the effects of fluoride treatments in clinical trials? Assessment: modern versus traditional methods.
In recent years there has been a pronounced change in the epidemiology and disease pattern of dental caries. In the current context, traditional methods of caries assessment, discriminating lesions at cavitation, are clinically inappropriate, and obsolete for research requiring detection of a very early phase of mineral loss. Modern prospective caries studies require sensitive methods permitting the measurement of small changes in tooth mineral content, and objective, quantitative measurements of such changes are now possible in a single caries lesion. For longitudinal studies there are noninvasive methods for assessment of new lesions as well as quantitative changes (progression or regression) in existing lesions. Among as yet unresolved issues are improved methods to assess the current activity of a lesion, methods for detection and quantification of secondary caries and root caries, calibration of methodologies between different research institutes, and methods capable of assessment of the whole continuum in the development of a caries lesion, from initial loss of mineral to cavitation.
Calibration↗
Light-induced fluorescence studies on dehydration of incipient enamel lesions.
Changes in the hydration state of enamel affect its optical qualities, such as light scattering and fluorescence. In this study, the rate of fluorescence loss was measured when incipient enamel lesions with different de-remineralization history were left to dehydrate. Four groups of lesions were studied. In groups A, B and C, the lesions were prepared in vitro in an acid-gel system. Group A was kept as control, and groups B and C were remineralized (4 weeks) without and with 1 ppm F in solution, respectively. Group D consisted of natural incipient lesions. Enamel fluorescence was measured for all lesions immediately after removal from water and subsequently at short intervals for 30 min. The change in fluorescence with dehydration varied between the groups. In lesions from groups A and B, it followed a double exponential decrease, while in lesions from groups C and D, it followed a mono-exponential decrease. In all groups, the fluorescence of sound surfaces declined mono-exponentially. The 'fractional fluorescence difference', defined as (L(sound) - L(carious) )/L(sound), became constant after periods of dehydration of about 5, 5, 20 and 5 min for groups A to D, respectively. The observation of the change of fluorescence with dehydration should be taken into consideration when planning studies that use fluorescence as an assessment method. However, it might also be used to gain insight into the properties for fluid transport inside the various lesions, relevant to de-remineralization or fluoride treatments.
Adolescent↗
Remineralisation of enamel lesions with daily applications of a high-concentration fluoride gel and a fluoridated toothpaste: an in situ study.
The inhibition of enamel demineralisation and the enhancement of remineralisation are positively but not linearly related to the concentration of fluoride, especially when high fluoride concentrations are used. The aim of this in situ experiment was to determine the maximum amount of enamel remineralisation that can be achieved with daily applications of very high concentrations of fluoride. For this purpose we compared the efficacy of a daily application of fluoridated topical gel (12500 ppm F, partly as NaF, Olafluor and Dectafluor, pH 4.5) in combination with a fluoridated toothpaste (1450 ppm F as NaF), with fluoridated toothpaste alone. Participants (n = 26, with partial dentures) were fitted with a demineralised enamel specimen (mean mineral loss of 1674 vol%.micro m) and were instructed to use one of the two fluoride treatments. After 4 weeks of treatment, the specimens were retrieved, a section was cut and analysed with microradiography. The remainder of each of the specimens was used for analysis of the 'loosely bound' and 'bound' fluoride. Fluoride was measured with gas-liquid chromatography. After 4 weeks in the mouth, the original lesion was reduced in size by 54% in the toothpaste + gel group (n = 14) and by 44% in the toothpaste-only group (n = 12), but the difference between the groups was not statistically significant. The mineral content profiles showed remineralisation of the lesions throughout the depth of the lesion. The enhancement of remineralisation by the high amounts of fluoride was most pronounced in the surface layer. For both the 'loosely bound' and 'bound' fluoride, a statistically significant increase in fluoride concentration could be found in the toothpaste + gel group. In the 4-week in situ period the use of high amounts of fluoride resulted in a maximum remineralisation rate. This is illustrated by an increase in remineralisation and higher fluoride concentrations in the toothpaste + gel group compared to the toothpaste-only group.
Dental Enamel↗
In vivo effectiveness of laser fluorescence compared to visual inspection and radiography for the detection of occlusal caries in primary teeth.
The purpose of this study was to evaluate the in vivo effectiveness of laser fluorescence compared to visual inspection and radiography for the detection of occlusal caries in primary teeth. Fifty sites from 30 molars in 29 patients were selected and evaluated under standardized conditions by 2 previously trained examiners according to the 3 diagnostic methods. Histological examination served as gold standard after exfoliation or extraction. Values obtained for sensitivity, specificity and accuracy were 0.60, 0.90 and 0.73 for laser fluorescence, 0.82, 0.85 and 0.84 for visual inspection and 0.62, 0.73 and 0.67 for radiography, respectively. Considering only dentinal caries, values were 0.73, 0.95 and 0.90 for laser fluorescence, 0.61, 1.00 and 0.90 for visual inspection and 0.96, 0.81 and 0.85 for radiography, respectively. We conclude that for the detection of occlusal caries in primary molars laser fluorescence presents a similar accuracy when compared to visual inspection and radiography, although visual inspection showed better values for sensitivities for both enamel and dentin lesions.
Child↗
Brushing abrasion of softened and remineralised dentin: an in situ study.
The aim of the present in situ study was to evaluate the effect of different periods of intra-oral remineralisation on the susceptibility of softened dentin to toothbrushing abrasion. Groups of 6 human dentin specimens (A-F) were recessed in the buccal aspects of intra-oral appliances which were worn for 21 days by 11 volunteers. The samples were demineralised twice a day extra-orally in the acidic beverage Sprite Light (pH 2.9) for 90 s. Subsequently, the dentin specimens were brushed at different times. Specimen A was brushed immediately after demineralisation. Specimens B-E were brushed after the intra-oral appliances had been worn for various periods in the mouth: specimen B for 10 min, C for 20 min, D for 30 min and E for 60 min. Specimen F was not brushed (control). After 21 days, dentin wear was measured with a profilometer. The following values (means +/- standard deviation) were recorded (microm): A, 23.6 +/- 16.7; B, 37.9 +/- 29.7; C, 31.8 +/- 26.5; D, 18.5 +/- 10.5; E, 15.3 +/- 11.6; F, 12.6 +/- 6.7. There was a statistically significantly increased dentin loss for groups A, B and C as compared to the controls (U test: p < 0.05). However, after intra-oral periods of 30 and 60 min, wear was not significantly higher than in unbrushed controls. It is concluded that for protection of dentin surfaces at least 30 min should elapse before toothbrushing after an erosive attack.
Carbonated Beverages↗
Application of the Zürich biofilm model to problems of cariology.
The term biofilm is increasingly replacing 'plaque' in the literature, but concepts and existing paradigms are changing much more slowly. There is little doubt that biofilm research will lead to more realistic perception and interpretation of the physiology and pathogenicity of microorganisms colonizing plaques in the oral cavity. There is clear evidence that the genotypic and phenotypic expression profiles of biofilm and planktonic bacteria are different. Several techniques are available today to study multispecies biofilms of oral bacteria, each having its particular advantages and weaknesses. We describe a biofilm model developed in Zürich and demonstrate a number of applications with direct or indirect impact on prophylactic dentistry: spatial arrangement and associative behavior of various species in biofilms; multiplex fluorescent in situ hybridization analysis of oral bacteria in biofilms; use of the biofilm model to predict in vivo efficacy of antimicrobials reliably; mass transport in biofilms; de- and remineralization of enamel exposed to biofilms in vitro. The potential of biofilm experimentation in oral biology has certainly not yet been fully exploited and dozens of possible interesting applications could be investigated. The overall physiological parameters of multispecies biofilms can be measured quite accurately, but it is still impossible to assess in toto the multitude of interactions taking place in such complex systems. What can and should be done is to test hypotheses stemming from experiments with planktonic cells in monospecies cultures. In particular, it will be interesting to investigate the relevance to biofilm composition and metabolism of specific gene products by using appropriate bacterial mutants.
Animals↗
Effects of two fluoridation measures on erosion progression in human enamel and dentine in situ.
The aim of the present study was to evaluate the effects of fluoride on erosive mineral loss in human enamel and dentine using a cyclic de- and remineralisation model in situ. The study was a three-treatment (5 days each) crossover design involving 4 (enamel) or 6 (dentine) healthy volunteers. Samples were recessed in palatal mouth appliances and worn day and night except during meals and were demineralised extraorally with 0.05 M citric acid (pH 2.3) for 6 x 5 min daily. Fluoridation was performed with toothpaste (SnF2/Olaflur; 0.14% F-) for 3 x 5 min daily (toothpaste fluoridation) or with toothpaste in combination with a mouthrinse (SnF2/Olaflur; 0.025% F-) for 3 x 5 min daily and with a gel (NaF/Olaflur, 1.25% F-) on days 1 and 3 instead of the toothpaste (intensive fluoridation). In the control group no fluoridation was performed. Mineral loss (microm) was determined with the use of longitudinal microradiography. In enamel, mineral loss was 40.7 +/- 15.1 microm in the control group, 18.3 +/- 12.4 microm after toothpaste fluoridation and 5.0 +/- 12.2 microm after intensive fluoridation. The respective values for dentine were 49.0 +/- 15.4, 35.0 +/- 15.5 and 19.8 +/- 12.0 microm. All differences were statistically significant (p < or = 0.001). The results indicate that intensive fluoridation is effective in preventing enamel and dentine from mineral loss even under severely erosive conditions.
Amines↗
Influence of the organic matrix on root dentine erosion by citric acid.
This investigation was conducted in an attempt to clarify the role of the organic matrix in bovine dentine demineralisation by 1% citric acid. Dentine slabs (n = 15) were treated for 2 min with 10% sodium hypochlorite (NaOCl, a strong protein solvent), 2% glutaraldehyde (GDA, a protein fixative) or deionised water (DIW, as negative control) prior to each of 5 demineralisation periods of 30 min. The mineral loss (DeltaZ), lesion depth (LD) and surface loss (SL) were determined after each period of demineralisation, by transverse microradiography. The NaOCl-treated group showed higher DeltaZ and LD than the GDA- and DIW-treated groups. No differences between GDA and DIW groups were found. The DeltaZ and LD profiles were explained by quadratic fits (r(2) >0.80; p = 0.001) in all groups. SL was detected only in the NaOCl-treated group. The data suggested that the maintenance of the organic matrix in the lesion might be important to reduce the erosion progression rate.
Animals↗
Comparison of calcium/phosphorus analysis, longitudinal microradiography and profilometry for the quantitative assessment of erosive demineralisation.
The study is a comparison of methods for the quantitative measurement of erosive mineral loss including longitudinal microradiography (LMR), profilometry (PM), and analysis of calcium (CA) and phosphorus (PA) in the erosion solution. Polished human enamel samples were taped, covered with nail varnish and the edges of the resulting enamel window marked with drilled holes as a reference. All samples were subjected to baseline LMR. Sixty samples each were eroded with citric acid (0.05 M; pH 2.3; 10 ml per sample) for 30, 60, 90, or 120 min. Erosive loss of each sample was estimated by the four methods. All methods revealed a linear erosive loss over time and showed good linear correlation. Values calculated from PM and LMR were both approximately 20% lower than those from CA and PA. After 30 min erosion, LMR showed no significant correlation with the other three methods. With LMR, erosive loss below 20 microm should be interpreted with care.
Calcium↗