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PubMed2005

Age-related transparent root dentin: mineral concentration, crystallite size, and mechanical properties.

Many fractures occur in teeth that have been altered, for example restored or endodontically repaired. It is therefore essential to evaluate the structure and mechanical properties of these altered dentins. One such altered form of dentin is transparent (sometimes called sclerotic) dentin, which forms gradually with aging. The present study focuses on differences in the structure and mechanical properties of normal versus transparent dentin. The mineral concentration, as measured by X-ray computed microtomography, was significantly higher in transparent dentin, the elevated concentration being consistent with the closure of the tubule lumens. Crystallite size, as measured by small angle X-ray scattering, was slightly smaller in transparent dentin, although the importance of this finding requires further study. The elastic properties were unchanged by transparency; however, transparent dentin, unlike normal dentin, exhibited almost no yielding before failure. In addition, the fracture toughness was lowered by roughly 20% while the fatigue lifetime was deleteriously affected at high stress levels. These results are discussed in terms of the altered microstructure of transparent dentin.

Aged↗
PubMed2004

In vitro growth, acidogenicity and cariogenicity of predominant human root caries flora.

Streptococcus mutans (Sm), Lactobacillus acidophilus (La) and Actinomyces israelii (Ai) have been associated with root surface caries, which is an increasing problem in elderly Chinese. The aim of this study therefore, was to evaluate in vitro, the growth, acidogenicity and cariogenicity of these organisms, both in mono- and co-cultures using an in vitro model. Forty-eight root specimens were prepared using intact extracted human molars. Fresh, wild-type bacteria obtained from root caries lesions were assembled into seven experimental groups as either mono- or co-cultures and incubated with the root specimens. Appropriate controls were included. Growth curve of each experimental group was monitored for 24h, aerobically, at 37 degrees C using a microplate reader. The pH of the medium was recorded after 24-h incubation using a pH meter. Mean depths of artificial root lesions produced in each cultural group were measured using polarized light microscopy in specimens cut into thin sections (100+/-20 microm). Compared with mono-cultures, synergistic growth was observed in co-cultures of 'La+Sm', 'Ai+La' and 'Ai+La+Sm'. Mean lesion depth produced in La group was significantly shallower than other mono- or co-culture groups (p<0.01). The pH values of all culture media were similar after 24-h incubation. The current data elucidate the complex interactions of three predominant bacterial species considered prime agents of human root surface caries.

Acids↗
PubMed2004

The use of in situ models and QLF for the study of coronal caries.

OBJECTIVES: The purpose of the paper is to review aspects of the systems available to model the caries process in enamel. METHODS: The in situ model developed in Liverpool, and the new method of quantifying mineral loss, Quantitative Light-induced Fluorescence (QLF), are described. QLF is a powerful new diagnostic tool which can be used to measure demineralisation and remineralisation in tooth surfaces in vivo; studies to optimise, validate and use QLF in different clinical situations are described. RESULTS: Examples of the use of in situ models show that they are particularly valuable for monitoring de and remineralisation of artificial lesions in relation to product testing as alternatives to clinical trials, and present significant advances over in vitro methods. Quantification of mineral loss by Transverse Microradiography (TMR) as in the traditional Liverpool model has produced much valuable information, but the destructive nature of the method limits experimental design, and removes the system from the clinical situation. As a possible alternative, QLF has been validated and optimised. Longitudinal measures can be made on the same surface, and examples of its use are for monitoring recurrent caries and demineralisation around orthodontic brackets. CONCLUSIONS: While current in situ models provide a major advance over earlier caries models, measurement of de and remineralisation by destructive methods such as transverse microradiography limits the design of experimental investigations. QLF offers significant time saving, reduces the cost of clinical studies, and because the measurements can be carried out longitudinally in vivo, can remove the need for intra-oral appliances carrying experimental tissues.

Dental Caries↗
PubMed2005

Development of an in situ root caries model B. In situ investigations.

OBJECTIVES: The aims of this pilot study were to assess the suitability of an in situ model for root caries studies, and to investigate the effect of sub-surface lesion mineral content and ultrastructural organisation on remineralisation. METHODS: Subjects were selected by criteria generally used for coronal caries models. Plaque pH responses and salivary flow rates were determined by standard methods. The chosen substrate was human dentine with artificially induced caries-like demineralisation and sterilised by gamma-irradiation (4100 Gy). Two levels of baseline demineralisation were induced by exposure to an acid buffer for 2 or 5 days. Mineral content was measured by computer-controlled quantitative microradiography. RESULTS: Remineralisation in situ was greater in smaller lesions with lower surface mineral content than in larger lesions in which the surface mineral content was high. CONCLUSIONS: The model is suitable for further development for investigating dentinal caries. More work is needed to validate the model by means of a fluoride dose-response study.

Adult↗
PubMed2005

Development of an in situ root caries model. A. In vitro investigations.

OBJECTIVES: The paper describes preliminary in vitro investigations, the objectives of which were to examine the influence of certain experimental parameters on artificial carious lesion formation in root hard tissues, and their remineralisation. These experiments formed part of a wider study that aimed to develop an in situ model of root caries, based on the existing coronal caries model used in Liverpool. The present studies examined the effects (a) of the anatomical origin of the dentine, the presence or absence of cementum, the exposure time and the type of demineralising system, on lesion development, and (b) of baseline lesion size on the extent and location of mineral re-precipitation. METHODS: Mineral content parameters in plano-parallel sections taken from dentine lesions were determined by computer-controlled transverse microradiography. RESULTS: The importance of the anatomical origin of the dentine on lesion formation was investigated by comparing in vitro lesion formation in premolar and molar dentine, and in dentine from apical, middle and coronal thirds of the root: no difference was observed between these sites. Lesions formed more rapidly in acid buffer solutions than in acid gel systems, and were more reliably produced when cementum was removed. The effect of baseline lesion size on subsequent in vitro remineralisation demonstrated that a small baseline mineral content was associated with a larger percentage mineral gain. The location of mineral deposition throughout the lesion was also influenced by baseline mineral content parameters. CONCLUSIONS: The results form a basis for the further development of an in situ dentinal caries model, providing data to suggest that manipulation of parameters involved in the preparation of artificial carious lesions has a significant effect on the behaviour of the lesion, particularly the phenomenon of remineralisation. Further work is needed to investigate the behaviour of the model in situ.

Bicuspid↗
PubMed2006

Impact of the acid flow rate on dentin erosion.

OBJECTIVE: The study aimed to evaluate the erosive effects of acids flowing with different velocities and duration on dentin previously pre-treated with distilled water or human saliva. METHODS: Bovine dentin surfaces were submitted to a 10 min demineralisation with hydrochloric or citric acid (pH 2.3, 37 degrees C) in an artificial mouth at flow rates of 3, 2.25, 1.5, 0.75 or 0.15 ml/min or in 30 ml of the respective acid without movement (each subgroup n=16 specimens). Prior to the demineralisation, half of the specimens of each group were either pre-treated with distilled water or human saliva for 120 min. After 2, 5 and 10 min demineralisation, profilometric traces of dentin loss were performed perpendicular to the direction of acid flow at three sites (A-C) with intervals of 500 microm. The first profile (A) was taken in a distance of 1.5 mm from the acid starting to flow over the sample. Thus, median dentin loss at each site was calculated and statistically analysed by five-way ANOVA. RESULTS: Dentin loss increased with increasing acid flow rate and demineralisation time and was higher for demineralisation with citric acid compared to hydrochloric acid. For given flow rates of 0.15 to 3 ml/min, measurement of dentin loss yielded highest values for site A and decreasing values for sites B and C. For all groups, no significant differences of dentin loss were observed between specimens pre-treated with distilled water or human saliva. CONCLUSION: Under the conditions of this study, both duration of demineralisation and acid flow rate but not pre-treatment with distilled water or saliva influence the extent of dentin erosion.

Adult↗
PubMed2003

A study investigating the formation of artificial sub-surface enamel caries-like lesions in deciduous and permanent teeth in the presence and absence of fluoride.

OBJECTIVES: Clinical and in situ studies have shown that caries formation and progression is faster in primary than in permanent teeth. Ambient levels of fluoride are also known to influence the processes of carious lesion formation. The aims were, firstly to investigate the incidence of artificial sub-surface caries lesion formation in the enamel of deciduous and permanent teeth in vitro. Secondly, to compare quantitatively the mineral content and distribution of these lesions and assess the possible influence of fluoride upon the lesion parameters. METHODS: Twenty primary molars and 20 permanent premolars were randomly assigned to one of four experimental groups. Samples in each experimental group were immersed in a 0.05M lactic acid gel (6% w/v hydroxyethyl cellulose, pH 4.5) either in the absence or presence of fluoride for 7 days. Subsequently, lesion parameters of mineral loss (vol x % microm) and lesion depth (microm) were assessed by transverse microradiography and image analysis. RESULTS: No significant differences existed between the lesion parameters of permanent and primary teeth (P=0.20). Irrespective of tooth type, lesion parameters were significantly reduced in samples demineralised in the presence of fluoride (P< or =0.002). CONCLUSIONS: Fluoride significantly reduces the severity of sub-surface caries lesions formed in vitro and in contrary to previous studies, there were no significant differences in lesions parameters between permanent and primary teeth.

Cariogenic Agents↗
PubMed1998

In situ de- and remineralisation of enamel in response to sucrose chewing gum with fluoride or non-fluoride dentifrices.

OBJECTIVES: Enhancement of the remineralisation of artificial enamel lesions has been observed in an intraoral model whether subjects chewed gum sweetened with a non-cariogenic sweetener such as sorbitol [1-3] or sucrose [4] after meals or snacks, and with use of a conventional (1500 ppm F) fluoride dentifrice. Since most of the clinical surveys which have shown the potential cariogenicity of sucrose chewing gum [5] were conducted before use of fluoridated dentifrices became widespread, the effect of fluoride dentifrice on de- and remineralisation of artificial lesions in enamel in response to chewing sucrose-sweetened gum has been examined with the aim of attempting to resolve this apparent discrepancy. METHODS: Subjects wore an intraoral device bearing an enamel lesion and chewed one piece of sucrose gum for 20 min after each of three meals and two snacks daily for two 3-week periods, during which they used a dentifrice containing either 0 or 1500 ppm F in a double-blind, cross-over design. Measurement of the mineral content of the lesions was determined by microradiography or polarised light microscopy. RESULTS: It was found that remineralisation tended to occur with 1500 ppm F dentifrice, but demineralisation with non-F dentifrice; the difference in enamel mineral content between the two periods was significant (P < 0.05). CONCLUSIONS: The results indicate that the potential cariogenicity of sucrose-containing chewing gum may indeed be negated by the use of a conventional fluoride dentifrice.

Adolescent↗
PubMedDate not supplied

Performance of some diagnostic systems in the prediction of occlusal caries in permanent molars in 6- and 11-year-old children.

OBJECTIVES: Attempts have been made to develop diagnostic methods which enable an early diagnosis of occlusal lesions which are not detectable by visual inspection. The aim of this study was to compare the performance of visual inspection focused on finding signs of fissure decalcification and discoloration, visual inspection upon fibre-optic transillumination (FOTI), and electrical conductance measurements (ECMs) in predicting the onset of occlusal caries in 6- and 11-year-old children. METHODS: Fifty children aged 5-7 and 11-15 years, having first or second permanent molar teeth that were not exposed to the oral environment for more than half a year, participated in the study. Following baseline data recording, the diagnostic measurements were repeated six times at 6-month intervals over a period of 2.5 years. RESULTS: Data were collected at predefined sites in the fissures. During the study, 220 of the 652 sites, i.e. 75 of 197 molars in 31 of the 50 children were judged to require a sealant or a sealant restoration. Two examiners jointly decided on the decay status at the sites. Survival plots showed that ECMs were superior to FOTI and fissure discoloration in predicting the onset of occlusal caries, although the differences were small. CONCLUSION: ECM is a better predictor of occlusal caries than fissure discoloration and FOTI, although the differences among the performance of the three methods in this study were very small. A cost-effective analysis is envisaged to obtain insight into the practical value of ECMs in the prediction of occlusal caries and, thus, into the effectiveness of sealant application.

Adolescent↗
PubMedDate not supplied

The effect of a resin-modified glass ionomer restorative material on artificially demineralised dentine caries in vitro.

OBJECTIVES: Recurrent caries is one of the most common reasons for the replacement of restorations. One method of reducing the frequency of this problem may be by using fluoride-releasing restorative materials. The aim of this in vitro study was to evaluate the progression of artificial lesions around resin-modified glass ionomer (Vitremer) restorations placed in root surfaces. Class V cavities were prepared on the mesial and distal surfaces of 28 human premolar teeth. Artificial carious wall lesions were created in all cavities. The root of each tooth was then hemisected through the middle of the two cavities, before being restored with either the glass ionomer or amalgam, while the opposing cavities on the same root portion were varnished as negative controls. Forty-eight specimens were pH-cycled in remineralising and demineralising solutions for 20 h and 4 h, respectively, each day for 4 weeks, whilst in a smaller control group of eight specimens, the demineralising solution was replaced with deionised water. Mineral changes in the carious lesions were evaluated using contact microradiography. RESULTS: Results showed that varying degrees of subsurface demineralisation and remineralisation were evident, with a laminated appearance in lesions adjacent to the glass ionomer. There was higher remineralisation in the glass ionomer-filled cavities compared with the amalgam-filled cavities. In the water-cycled group, glass ionomer showed an increase in mineral content (p < 0.05), while no changes were observed in the amalgam-filled cavities. CONCLUSIONS: This model has shown that glass ionomer has a greater potential than amalgam for remineralisation of artificially created wall lesions within an acidic environment.

Bicuspid↗
PubMed1995

A new light-cured glass ionomer cement that bonds brackets to teeth without etching in the presence of saliva.

Previous studies stress certain advantages of glass ionomer cements, for use in bonding orthodontic brackets to teeth. Failure rate, however, had been higher than with conventional procedures. A new light-cured glass ionomer cement exhibited all the necessary qualities needed to bond brackets, without any etching and in the presence of saliva. The tensile strength of this cement exhibited enough resistance to forces needed to move teeth. The debonding procedures were also completely undamaging to the underlying enamel surfaces. On removal of the appliances, no decalcification was observed on any teeth, because the cement releases fluoride. Both the time saved during a routine strap-up, plus the ease to both the operator and the patient, could make light-cured glass ionomer cement the ultimate choice for bonding techniques after many trials, this cement is now being routinely and successfully used on all patients.

Acid Etching, Dental↗
PubMed1998

A longitudinal laser fluorescence study of white spot lesions in orthodontic patients.

Orthodontic treatment with fixed appliances increases the caries risk in young persons. The aim of this study was to apply a new caries diagnostic method, quantitative laser fluorescence, for longitudinal in vivo quantification of changes in incipient enamel lesions related to fixed orthodontic appliances. Seven young patients with active caries lesions disclosed at removal of the orthodontic brackets and bands were enrolled in the study. Caries preventive measures were intensified, including dietary advice, oral hygiene instructions, and the regular use of a fluoride dentifrice. The caries lesions were monitored with the quantitative laser fluorescence method after removal of the brackets and once a month thereafter. For each lesion, three quantities were measured: lesion area (mm2), mean fluorescence loss (%) over the lesion, and maximum loss of fluorescence (%) in the lesion. During a 1-year follow-up period, the areas of the lesions decreased and the enamel fluorescence lost was partly regained indicating that a remineralization process had occurred. It was concluded that quantitative laser fluorescence seems suitable for in vivo monitoring of mineral changes in incipient enamel lesions, and useful for the evaluation of preventive measures in caries prone persons, such as orthodontic patients.

Adolescent↗
PubMedDate not supplied

Modified oligosaccharides as potential dental plaque control materials.

Metabolic acids produced by oral pathogens demineralize tooth surfaces, leading to dental caries. Glucosyltransferases are the key factor in this process. We synthesized various modified oligosaccharides and tested them for their inhibitory effects on glucosyltransferase activity. Oligosaccharides were produced using a mixed-culture fermentation of Lipomyces starkeyi and Leuconostoc mesenteroides and then further modified as iron- and sulfate-oligosaccharides. Iron- and sulfate-oligosaccharides reduced glucosyltransferase activity of Streptococci from 17% to 43% and prevented the formation of insoluble biomass on the surface of glass vials or stainless steel wires in the presence of sucrose. They also reduced the growth and acid productions of oral pathogens including S. mutans, S. sobrinus, Eikenella corrodens, Prevotella intermedia, and Actinobacillus actinomycetemcmitans.

Animals↗
PubMed2002

Cervical tooth wear and sensitivity: erosion, softening and rehardening of dentine; effects of pH, time and ultrasonication.

BACKGROUND: Cervical dentine wear is commonly observed and may be associated with dentine hypersensitivity. Erosion is thought to play a part in both conditions but compared to enamel has been little studied in dentine. AIM: The aims of these studies in vitro were to: (i) determine the effects of citric acid on dentine at different pH values and over time; (ii) measure the depth of dentine demineralisation or softening using ultrasonication; (iii) determine whether softened dentine can be remineralised or rehardened using artificial saliva. METHODS: Groups of flat dentine specimens prepared from unerupted human third molar teeth were: (a) exposed to citric acid at pH 3.2 for periods up to 4 h with mineral water as control; (b) exposed to citric acid at pH 2.54, 3.2, 4.5, 5.5 and 6.0 for 2 h and then subjected to ultrasonication stepwise up to 480 s; (c) exposed to citric acid at pH 2.54, 3.2, and 4.5, placed into artificial saliva for 24 h and then subjected to ultrasonication as in (b). Loss of dentine was measured by profilometry, after, each phase of erosion, ultrasonication and immersion in artificial saliva. RESULTS: Depth of erosion significantly increased non-linearly with time and significantly decreased with increasing pH. Ultrasonication had minimal albeit significant effects on control specimens. Removal of softened dentine increased with ultrasonication time. Depth of softening significantly increased with increasing erosion time to 2 h, plateauing at 2 microm. Depth of softening increased to 2 microm from pH 2.54 to pH 3.2 and decreased at higher pH values thereafter. 24 h in artificial saliva provided no protection to the soften zone against ultrasonicaion. Citric acid at all pH values and exposure times removed the dentine smear layer to expose tubules. Ultrasonication did not remove the smear layer on control specimens but removed all deposits formed after exposure to artificial saliva. CONCLUSION: It is concluded that dentine is susceptible to erosion even at relatively high pH, the tubule system is readily exposed and dentine, unlike enamel, shows little propensity to remineralise.

Analysis of Variance↗
PubMed2003

Erosion-inhibiting effect of sodium fluoride and titanium tetrafluoride treatment in vitro.

The prevention of dental erosion with fluoride is still largely unknown territory. It was the aim of this study to determine the erosion-inhibiting effect of topical neutral 1% sodium fluoride (NaF) application and an application of a 4% titanium tetrafluoride (TiF4) solution compared with no treatment. Ten bovine incisors were selected and three enamel samples prepared from each tooth. One sample from each tooth was assigned to one of three experimental groups. The experimental treatments were: no fluoride application (control); 4 min application of neutral 1% NaF gel; and 4 min application of 4% TiF4 solution. All of the specimens were repeatedly exposed to 50 mm citric acid solution containing 0.4 mm CaCl2, and 2.2 mm KH2PO4 at pH 3.0 over four consecutive days. The acid exposure was performed in intervals and the intensity was increased over the days of the experiment. Enamel dissolution was determined by calcium content measurement of the acid solution after exposure, using atomic absorption spectroscopy. A statistically significant erosion-inhibiting effect was found for both NaF and TiF4 treatments compared with the control group from an erosion exposure time of 3 min. The reduction of calcium loss, however, was higher for the TiF4-treated specimens than the NaF-treated. From 16 min of erosion exposure, the erosion-inhibiting effect was significantly stronger in the TiF4 than the NaF group. The relative reduction of calcium loss compared with the control group remained stable for the TiF4 group, whereas for the NaF group the relative reduction decreased with cumulative erosion time. It is concluded that topical TiF4 application provides a potential treatment option in erosion prevention.

Analysis of Variance↗
PubMed2002

The effect of commercially available saliva substitutes on predemineralized bovine dentin in vitro.

OBJECTIVE: The objective of this study was to evaluate the effects of various saliva substitutes (Artisial; Glandosane; Oralube; Saliva medac; Oralbalance) on the lesion depth and the mineral content of predemineralized bovine dentin in vitro. MATERIALS AND METHODS: Ninety-six dentin samples were prepared from 24 freshly extracted bovine incisors. The samples were predemineralized (pH 5.5; 10 days), and subsequently exposed to the various artificial salivas. A carbonate-reduced mineral water (Hirschquelle) as well as the mouthwash solutions Meridol and biotène served as controls. Lesion depth and mineral loss were evaluated from microradiographs of thin sections (110 microm) by a dedicated software package (TMR 1.24). RESULTS: After storage in Glandosane and biotène, the results indicated a significant mineral loss and an increase in lesion depth (P < 0.01; Wilcoxon). In contrast, specimens stored in Oralube showed a decrease in lesion depth and an increase in mineral content (P < 0.05; Wilcoxon). CONCLUSIONS: Thus, the use of neither Glandosane nor biotène can be recommended in dentate patients with severe xerostomia.

Amines↗