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Results obtained in the caries pathogenesis in recent years as well as the successes in the field of remineralization opened the way to heal the initial stage of the caries by means of preventive methods. Increased attention should be paid to early diagnostics of the caries, and evolution of the new diagnostics methods should be followed by attention. Combined employment of the various diagnostics methods should be aimed at.
Incipient dental caries--according to up-to-date concepts in dental research--means a demineralization without cavity formation. At this stage the carious process is reversible, and remineralization can be achieved in the presence of locally applied fluorides. In chrystalchemical experiments, however, by treating natural apatites with lanthanides, [Ce, La, Pr, Nd, Sm, Eu, Tb ... Y, Sc] a more resistant complex could be developed. In this study extracted human molar teeth were kept for 60 days in Cerium (III)-nitrate solution, in order to investigate the incorporation of Ce3+ into human sound and carious enamel by light-microscopic-, and electron microprobe methods. Ce3+ was incorporated in sound enamel as well as into the incipient carious lesion, showing the histological characteristics of a remineralizing lesion. The mean values of the microprobe analysis data showed an increase in Ce3+ changing place with the Ca2+ the developing cerium-apatite being more hard and resistant from a mineralophysical point of view.
The actual mechanism of fluoride action is still a subject of debate. A dogma has existed for many decades, that fluoride has to be ingested and acts mainly pre-eruptively. However, recent studies concerning the systemic effect of fluoride supplementation concluded that the caries-preventive effect of fluoride is almost exclusively posteruptive. Moreover, epidemiologists have cast doubt on the validity of the 'old' studies dealing with fluoride use. The concept of the posteruptive fluoride effect is supported by in vitro and in situ investigations demonstrating that the mode of action of fluoride can be attributed mainly to its influence on de- and remineralization kinetics of dental hard tissues. Therefore, topical fluoride application (e.g. in the form of fluoridated dentifrices) should be encouraged. There are still important questions open that need to be answered despite existing knowledge about the caries-preventive effect of fluoride.
A case of bilateral maxillary canine impaction with incomplete lateral incisor transposition in an adult is reported. The case was treated by relocating the canines in their correct position in the arch. The impacted teeth were driven through the sockets of the extracted deciduous teeth. The periodontal status during and after relocation of the transposed impacted canines was evaluated. Remineralization of bone between the lateral incisor and the canine was observed during treatment on the left side, while it was delayed on the right. Two years after the end of treatment, no loss of periodontal attachment could be detected and probing depth was less than 2 mm on the treated teeth.
We tested the anti-caries properties of a prototype remineralizing toothpaste containing sodium fluoride, soluble phosphate and soluble calcium, similar but not identical to Enamelon Toothpaste in specific pathogen-free Osborne-Mendel rats. A fluoride-free placebo and sodium fluoride-containing Crest Regular were used as negative and positive control toothpastes, respectively. Sixty weanling rats were randomly distributed into groups of 20, all were inoculated with S. mutans 10449S, ate diet 2000, and drank demineralized water. Each toothpaste, contained in coded tubes, was applied to the rats' teeth, once for one minute/day, five days/week. There was no difference in bacterial recoveries from tooth swabs among the groups at either the 22- or 37-day post-inoculation recovery date. After rat sacrifice and defleshing, heads were randomly coded and scored blindly for carious lesions according to Keyes/Larson methods. Only after scoring was completed were the random codes broken and the treatment groups identified. Both the Enamelon-like product and Crest Regular treatments resulted in lower total enamel caries scores than the placebo (p < 0.001). The sum of smooth surface scores was also lower for the fluoride-containing toothpastes than for the placebo (p < 0.001). However, the Enamelon-like product had greater caries inhibitory properties than Crest Regular on sulcal and approximal tooth surface categories (p = 0.004 and p = 0.045, respectively). Therefore, the Enamelon-like product had superior caries inhibiting properties compared to Crest Regular at these tooth areas.
A saliva substitute, VA-OraLube, was evaluated for ability to reharden dental enamel and to relieve intraoral soft tissue symptoms in patients receiving radiotherapy for malignancies of the head and neck. Treatments of 15, 30 and 60 minutes rehardened enamel by 3.1%, 4.0%, and 5.5%, respectively. In the second experiment, treatment for 60 minutes with the complete solution rehardened enamel by 5.2%. Omitting calcium, phosphorus and/or fluoride from the formulation greatly decreased this rehardening potential. Treatment of enamel with fresh whole saliva induced rehardening at a 7.3% level in comparison to the 5.5% and 5.2% derived by using the saliva substitute. Since the xerostomic patient usually uses the product very frequently, there is a remineralization potential of significant consequence. A total of 125 xerostomic patients used the saliva substitute on an ad lib basis over a period of 4 months. Patient responses indicated a very high level of acceptance and the virtual elimination of troublesome problems previously associated with the dry mouth state.
Dental caries is a biofilm-dependent oral disease, and fermentable dietary carbohydrates are the key environmental factors involved in its initiation and development. However, among the carbohydrates, sucrose is considered the most cariogenic, because, in addition to being fermented by oral bacteria, it is a substrate for the synthesis of extracellular (EPS) and intracellular (IPS) polysaccharides. Therefore, while the low pH environment triggers the shift of the resident plaque microflora to a more cariogenic one, EPS promote changes in the composition of the biofilms' matrix. Furthermore, it has recently been shown that the biofilm formed in the presence of sucrose presents low concentrations of Ca, P(i), and F, which are critical ions involved in de- and remineralization of enamel and dentin in the oral environment. Thus, the aim of this review is to explore the broad role of sucrose in the cariogenicity of biofilms, and to present a new insight into its influence on the pathogenesis of dental caries.
While our knowledge of the dental caries process and its prevention has greatly advanced over the past fifty years, it is fair to state that the management of this disease at the level of the individual patient remains largely empirical. Recommendations for fluoride use by patients at different levels of caries risk are mainly based on the adage that more is better. There is a general understanding that the fluoride compound, concentration, frequency of use, duration of exposure, and method of delivery can influence fluoride efficacy. Two important factors are (1) the initial interaction of relatively high concentrations of fluoride with the tooth surface and plaque during application and (2) the retention of fluoride in oral fluids after application. Fluoride dentifrices remain the most widely used method of delivering topical fluoride. The efficacy of this approach in preventing dental caries is beyond dispute. However, the vast majority of currently marketed dentifrice products have not been clinically tested and have met only the minimal requirements of the FDA monograph using mainly laboratory testing and animal caries testing. Daily use of fluoride dental rinses as an adjunct to fluoride dentifrice has been shown to be clinically effective as has biweekly use of higher concentration fluoride rinses. The use of remineralizing agents (other than fluoride), directed at reversing or arresting non-cavitated lesions, remains a promising yet largely unproven strategy. High fluoride concentration compounds, e.g., AgF, Ag(NH3)2F, to arrest more advanced carious lesions with and without prior removal of carious tissue are being used in several countries as part of the Atraumatic Restorative Treatment (ART) approach. Most of the recent innovations in oral care products have been directed toward making cosmetic marketing claims. There continues to be a need for innovation and collaboration with other scientific disciplines to fully understand and prevent dental caries.
The purpose of this article is to compare various model systems for the production of in vitro root caries and to assess their ability to simulate the naturally occurring root caries process. Partially saturated buffer models and gel models were evaluated using polarized light microscopy and both qualitative and quantitative microradiography. All model systems showed very similar lesion formation when examined under polarized light. When microradiographs were compared, the systems which contained fluoride, showed clear radiopaque bands within the lesion. The bands, which occurred only in the presence of fluoride, appeared to be due to remineralization. When using an in vitro system that simulates the natural root caries process, it is imperative to understand the components of the particular model, as well as its limitations, and to be aware of the need for more than one evaluative technique.
In human premolars with posteruptive ages varying from 6 months to 4 years demineralized enamel was remineralized for 3 days at 37 degrees C in a recalcifying medium containing 2 mM Ca2+, 1.2 mM phosphate, 0.05 mMF- and 150 mM NaCl (pH = 7). The Ca, P and Ca/P molar ratio of the mineral gained were determined at various distances from the enamel surface. Whereas, particularly at 30 micrometers from the surface remineralization was higher and more extensive in young demineralized enamel, no difference could be found in Ca/P molar ratio, suggesting precipitation of an apatitic mineral in both young and old demineralized human enamel. The probable nature of the precipitate is that of a fluoridated hydroxyapatite.
Zinc levels in dentin, enamel, tooth deposit, and mixed saliva in caries were under study. The enamel and dentin Zn levels were measured by means of neutron activation analysis in 244 permanent intact teeth and in 92 permanent carious teeth from subjects died after acute injury. Tooth deposit and mixed saliva Zn levels were measured by the atomic absorption technique in 10 patients with caries and in 10 normal subjects; the groups were matched for dietary habits. The menu of these subjects over a month was examined and the content of daily dietary zinc was determined, and the level of salivary Zn excretion as against Zn content in the food was calculated. The dentin and enamel Zn levels were found increased in caries. A tendency to an increase of Zn level in the saliva was detected; a large proportion of this dietary element was excreted with the saliva in caries patients. The authors suggest that remineralization effect can be achieved in the initial stages of caries by oral and local application of Zn preparations.
Artificial white spot lesions have been prepared on bovine enamel surfaces by the controlled addition of lactate buffer containing methylhydroxydiphosphonate ions. The rates of remineralization have been measured using a constant composition method in solutions of calcium phosphate of low supersaturation. Deposition of new hydroxyapatite solid phase takes place exclusively within the white spot lesion at a rate appreciably slower than that of an acid-etched enamel surface, probably due to the presence of methylhydroxydiphosphonate located within the intact surface region of the lesion.
Dissolution and remineralization behaviors of self-setting apatite cement is organic acids and synthetic saliva and the effect of barium apatite (BaAp)on physicochemical and mechanical properties of the apatite cement were investigated. One-week solubility of several types of apatite cement was considerably smaller than that of commercially available dental cements in 1 mM of acetic, lactic and citric acids (pH4.0 at 37 degrees C). For example, the one-week solubility in citric acids was less than 4.5%. To investigate the dissolution behavior of the apatite cement in detail, two types of 45Ca labeled apatite cement were prepared. In one, the seed apatite was labeled with 45Ca(45Ca-HAp cement) and in the other the matrix apatite was labeled with 45Ca through use of 45Ca-DCPD (45Ca-DCPD cement). Solubility, estimated from the concentration of 45Ca released in 1mM of the organic acid was approximately zero for 45Ca-HAp cement, whereas the solubility of 45Ca-DCPD cement was similar to that of unlabeled cements. This suggests cat dissolution of the matrix apatite governs dissolution of the set cement. In synthetic saliva, the solution phosphate decreased with time once the set cement was introduced to the solution, whereas the solution calcium increased. The former finding suggests that some phosphate compounds precipitated in the synthetic saliva and the latter finding indicates that some portion of the set cement dissolved. The thermodynamic analysis of the solution compositions strongly suggests that remineralization is a major process and dissolution a minor one. In fact, in systhetic saliva labeled with 45Ca having a degree of supersaturation with respect to apatite comparable to rest saliva, 45Ca concentration in solution decreased once the cement pellet was introduced. This finding clearly suggests that the set apatite cement has the ability to remineralize but not to dissolve in synthetic saliva even if the degree of supersaturation with respect to apatite is relatively low. Addition of barium hydroxyapatite (BaAp) successfully bestowed clinically acceptable radio-opacity to the apatite cement. To accelerate the setting reaction which was retarded by Ba2+ released from BaAp at a lower pH during the first stage of spatulation, calcium hydroxyapatite (CaAp) was added to the cement mixture. At 20wt% of BaAp and 20wt% CaAp, the setting reaction proceeded at a neutral or weak alkaline pH, which is one of the most promising aspects of the apatite cement. The cement spaturated at L/P = 0.4 set within 10 minutes and its radio-opacity was comparable to or more than that of tooth enamel.(ABSTRACT TRUNCATED AT 400 WORDS)
One method of quantitating mineral content in thin sections of dental hard tissue is microdensitometry of contact radiographs. This method is often applied to analysis of artificial caries lesions. Because there is great inter- and intra-tooth variability, a single microdensitometric scan will not accurately reflect the content or distribution of mineral within an individual lesion, or within a group of lesions. To increase the number of replicates than can be handled routinely, a computer-driven microdensitometer has been used with a step series of aluminum and enamel to quantitate mineral content values at approximately 1-micron intervals. Accurate assessment of an individual lesion was made possible by averaging multiple scans of the lesion on each of several thin sections prepared from the lesion. Mean mineral profiles of treatment groups were then made from the profiles of the individual lesion. These data reduction techniques allowed for a large number of replicates to be used in the measurement of remineralization. The computerized microdensitometric system described here was developed to allow for an objective, quantitative analysis of the mineral content of dental hard tissue.
PURPOSE: The objectives of this study were 1) to examine the ultrastructural features of the resin-sclerotic dentin interface following the application of Clearfil Liner Bond II sigma to natural cervical wedge-shaped lesions, and 2) to evaluate the regional tensile bond strength of this self-etching primer at different locations on natural and artificially-created cervical lesions. MATERIALS AND METHODS: Deep cervical natural lesions were bonded using the self-etching primer. Micromorphology of the bonded interface at different locations within the lesions were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning transmission electron microscopy/energy dispersive x-ray analysis (STEM/EDX). Ultrastructural features were further compared with the use of the same self-etching primer on artificial lesions created in sound cervical dentin. A nontrimming technique was used to evaluate the regional tensile bond strength from the occlusal, gingival, and the deepest central part of both natural and artificial cervical lesions. Beams with a mean area of 0.46 +/- 0.03 mm2 were prepared and were pulled to failure using a Bencor Multi-T testing device attached to an Instron universal tester. Bond strength results were evaluated using a two-way ANOVA design. RESULTS: A hypermineralized layer devoid of intact, banded collagen was invariably present on the surface of the natural lesions. Depending upon its thickness at different locations of the lesion, the action of a self-etching primer may be limited to this surface layer alone, producing a hybridized hypermineralized surface layer. Penetration of the self-etching primer into the underlying sclerotic dentin produced a hybridized complex containing a hybridized hypermineralized surface layer as well as a subsurface layer of hybridized intertubular dentin. Bacterial colonization of the lesion surface resulted in the formation of an additional zone of hybridized intermicrobial matrix over the surface of the lesions. Dentinal tubules remained blocked with sclerotic casts, and resin tags were rarely observed. Regional tensile bond strength results showed that the overall bond strength to natural sclerotic dentin was about 20% lower than sound cervical dentin, but was independent of the different locations within the lesions from which bond strength was evaluated. CONCLUSION: There were four factors that may have influenced the overall decrease in bond strength in natural cervical sclerotic lesions: a) the presence of a hybridized intermicrobial matrix together with entrapped bacteria may have weakened the bonds, b) inability of a self-etching primer to etch through a thick, hypermineralized surface layer, c) presence of a layer of possibly remineralized, denatured collagen at the base of the hypermineralized surface layer, and d) retention of acid-resistant sclerotic casts that obliterate the tubular lumina and prevent effective resin tag formation.
Longitudinal microradiography has been used to determine inhibiting effects of aluminum (III), Al, and fluoride on mineral loss from slices of bovine enamel exposed to a demineralizing solution 4 h daily for 35 days. Inhibitor treatment was 5 min four times daily. For the remaining time, the samples were immersed in a neutral calcium phosphate solution which allowed neither remineralization nor demineralization. This study indicates that a 1-mM (27 ppm) solution of Al in a 0.1-M lactate solution, pH 5, has an inhibitory effect on the in vitro demineralization of bovine enamel. Application of this solution alternating with 20 mM (380 ppm) fluoride gave the same total inhibition as treatment with 20 mM fluoride alone.
Caries is one of the most prevalent of all human diseases. In recent years there has been a growing recognition that healing or remineralization protocols for the treatment of carious lesions in dentine are possible, rather than just relying on surgical removal of the diseased tissue and placement of restorative materials. This project proposes to investigate a strategy for deliberately stimulating cellular reparative processes for the treatment of this disease. In order to do this, it is necessary to develop a cell culture system to develop and characterize the mineralizing cells (odontoblast like) from human dental explants.
These studies demonstrate that a significant degree of remineralization of both natural and artificial lesions can be achieved in vitro. Changing the calcium concentration of the synthetic calcifying fluid had a significant effect on both the degree of remineralization achieved and the site of the lesion affected. When the calcifying fluid contained 3 mM calcium, remineralization occurred mainly in the superficial part of the lesion. When a 1 mM calcium calcifying fluid was used on adjacent halves of the same lesion, remineralization occurred throughout the entire depth of the lesion. Under these conditions there was a highly significant reduction in lesion size accompanied by an increase in orientated mineral crystals. The crystals were found to have diameters several times larger than those found in the sound enamel, most probably produced as a result of crystal growth. These results have significance in terms of both mechanisms of hard tissue repair and the possible eventual development of an agent for caries prevention.