The effect of remineralizing solutions on tooth wear in vitro.
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The aim of the study was to assess the effect of a toothpaste and mouthwashes containing amine fluoride (AmF) and stannous fluoride (SnF2) on dental plaque, gingivitis and root-surface caries. Forty-four adults participated in a five-month double-blind study. The following combinations of toothpastes and mouthwashes were used: (1) AmF/SnF2 toothpaste and AmF/SnF2 (Meridol) mouthwash (20 patients, mean age 45.7 years), (2) sodium fluoride (NaF) toothpaste and NaF mouthwash (24 patients, mean age 48.8 years). The mean values for dental plaque (Silness-Löe index) were clinically and statistically significantly reduced in both groups, the difference being greater in the AmF/SnF2 group. Sulcus-bleeding index values were clinically and statistically significantly decreased in both groups. There was no marked difference between the groups. The root caries index (RCl, Katz) had decreased by the end of the experiment by 10% in the NaF group and by 47.4% in the AmF/SnF2 group.
In order to achieve the greatest clinical benefit from the use of fluoride, we must understand its mechanism of action, so that fluoride can be given at the right time, by the best route, at the optimum dosage and in the most suitable form. The first article in this two-part series reviewed the scientific rationale behind the use of fluoride. Part 2 now illustrates fluoride therapy in practical terms, by examining nine clinical cases.
In situ models to assess the ability of oral care products or food components to enhance remineralization and/or inhibit demineralization of tooth enamel or roots must be very carefully designed to minimize the confounding effects of the many variables involved. Controlling these variables as closely as possible is essential if meaningful answers are to be obtained from the models. We have developed an in situ model which combines the experience of several groups. Detailed screening of subjects is essential. Selection criteria should include good general health, good dental health, mandibular partial denture, at least eight natural teeth, no active caries lesions, known fluoride history, normal salivary function, and no medications that affect salivary function. Each subject carries a sound enamel slab and an enamel slab with a pre-formed caries-like lesion (demineralized in vitro) in his/her denture on each side of the mouth for test periods of two or four weeks. The demineralization challenge is controlled by extra-oral immersion of the appliances in sucrose daily. Daily product exposure or daily food component exposure is used as desired. Compliance indicators and a diet diary are included. Whole saliva flow rate (unstimulated), plaque acidogenicity, and salivary fluoride are monitored during the test periods. At the end of the test period, the test slabs are assessed for mineral change, after being sectioned, by means of cross-sectional microhardness or microradiography. The mineral loss or gain (delta M, microns x vol%), compared with adjacent control sections retained in the lab, is calculated as change in delta Z (microns x vol%), namely, delta M = delta ZTEST - delta ZCONTROL.(ABSTRACT TRUNCATED AT 250 WORDS)
The milk incisors of 80 infant-school children were demineralized. For the following 3 weeks the children then rinsed their mouths with mineral solutions. By manifold replica yields (analysis by light- and scanning electron microscope) and colouring tests a positive influence of calcium and phosphorus holding solutions, among others with magnesium, too, on the remineralization was discovered.
The purpose of this study was to study the efficacy of a fluoride-containing chewing gum (0.1 mg F/stick chewed 5 x/day) in the remineralization of artificial caries lesions in abraded root surfaces compared to sorbitol-containing chewing gum and a no gum control group in vivo. Root specimens were cut from human root surfaces and polished. The specimens were demineralized in a buffered lactate solution with low concentration of fluoride in order to preserve an intact surface layer. Six healthy subjects wore mandibular Hawley-type appliances containing up to fourteen slabs for each of one control and two experimental periods. The experimental protocol included chewing five pieces of gums per day and brushing with fluoride-free dentifrice for each 21 days period. All three regimens were analyzed for fluoride uptake and microradiography. The results indicate that fluoride-containing chewing gum has a highly significant fluoride uptake and remineralization compared to sorbitol gum and control regimens, suggesting that fluoride chewing gum may provide another vehicle for fluoride delivery.
The histopathology of active and arrested human root caries was examined in extracted teeth by different optical methods. Significant differences were observed between the mechanisms operating on the various dental structures. Three different patterns of initial cementum and dentin lesions could be distinguished, depending on the severity of the cariogenic attack, the degree of sclerosis of the peripheral dentin, and the presence of calculus. Advanced lesions were characterized by various patterns of demineralization. In particular, a massive lateral spread of bacteria into intertubular dentin was observed. Consequently, unaffected dentinal areas became continuously undermined. In arrested lesions, either a partial or complete mineralization of the intertubular dentin was apparent. Dentinal tubules were sclerosed passively by re- or precipitation of Ca and PO4 ions. In contrast, tubules filled with ghosts of bacteria appeared mineralized by fine-granular crystals. Our observations indicate that both the arrestment and the remineralization of active lesions depend on (1) the degree of active sclerosis of dentinal tubules in areas underlying the lesion, (2) the degree of the bacterial infection of the dentin, (3) the degree of progression of the lesions, and (4) the location of the lesions at the various root surfaces. It is suggested that remineralization of active lesions can occur. This supports the concept of non-invasive treatment of root caries lesions without cavitation.
The aim of this study was to assess the remineralizing effect of an amine fluoride (AmF)- and stannous fluoride (SnF2)-containing toothpaste and mouthrinse on exposed root surfaces. A total of 44 adults participated in the 20-week, double-blind study and were grouped as follows: (1) 20 participants (mean age 45.7 years) used an AmF/SnF2 experimental toothpaste plus AmF/SnF2 (Meridol) mouthwash, and (2) 24 participants (mean age 48.8 years) used an NaF-containing toothpaste and mouthrinse. Root caries index (RCI) and root surface scores were determined by a modified method of Katz (J Dent Res, 1984). RCI mean values showed decreases of approximately 47% in the AmF/SnF2 group, and 10% in the NaF group. With respect to root caries scores, the number of persons with decreased softened (non-carious) surfaces between the baseline and control examinations was statistically significant (p less than 0.05) in the AmF/SnF2 group but not significant in the NaF group. A statistically significant difference (p less than 0.05) in the results of the groups favored the AmF/SnF2 subgroup. Thus, the data point to a possible remineralizing effect of topically applied AmF/SnF2 on softened root caries surfaces.
This study deals with the role of collagen in the remineralization of bovine incisor root lesions. The degradability of the collagenous matrix after in vitro remineralization was also investigated. The root surfaces were exposed to 0.1 M acetic acid, pH 4.0, to produce erosive lesions or to 0.1 M lactic acid, 0.2 mM methane hydroxy diphosphonate, pH 5.0, to produce subsurface lesions. After demineralization, the roots were subjected to remineralization, with or without prior treatment with a bacterial collagenase to remove accessible collagen. Remineralization was carried out in solutions with a Ca/Pi molar ratio of 1.67, and [Ca]. [Pi] concentration products of 0.6, 1.35 or 2.4 mM2, with all solutions having an ionic strength of 0.15 M, and a pH of 7.0. After remineralization, the roots that were not treated with collagenase were incubated with the enzyme. The results indicate that remineralization of erosive lesions is surface-controlled and that of subsurface lesions diffusion-controlled. For both lesion types it was shown that the removal of collagen before remineralization did not affect the rate of mineral deposition in the root lesions. Nevertheless, remineralization in those lesions where accessible collagen had not been removed resulted in a significant reduction in the amount of degradable collagen. The observations of this study suggest that remineralization did not occur by nucleation of mineral on the organic matrix but rather by growth of residual crystals in the partially demineralized root tissue.
The purpose of this study was to present a modified photometer based digital analysis system for image enhanced microradiographic semi-quantitation of reactions of demineralization and remineralization of root surface lesions. The system was used to determine effects of fluoride on abraded root surface dentin in vitro. Lesions of 30-40 micron depth were produced during 18 h exposure of 180 micron thick single sections in solution of 3 mM Ca (Ca/P 1.67) and 30 mM lactic acid at pH 5.1. Mean mineral content of the lesions was 32% relative to adjacent sound dentin. Exposure of 20 h in the same acid with 5 mM Ca (Ca/P 1.67) and 0.12 mM NaF at pH 6.1 restored the mean mineral content to 76% of normal and increased the resistance of the lesions to demineralization. Remineralization and subsequent demineralization characteristics indicated the growth of fluorapatites on residual minerals in the dentin lesions. The microradiographic analysis system proved to be sensitive and critical in these studies.
This paper reviews the use of our intra-oral crown single-section model for the evaluation of in situ demineralization and remineralization. The model uses normal, healthy adults who are in need of a gold crown. A slot is placed in the working crown which can hold 3-4 single sections. A typical experiment would use an enamel lesion, root lesion, and sound root section which are characterized with polarized light microscopy and/or microradiography prior to insertion in the crown. After the experimental regimen, the sections are removed and re-characterized for any changes. The model has been used to evaluate mineral changes from the use of fluoride dentifrices and rinses, chewing gum, and food sequencing. The advantages of the model system are the before-and-after measurements on the same section, a natural plaque formation, interaction with saliva, episodic demineralization and remineralization, no bulky appliances, and the use of reasonable time frames. This model, therefore, reduces the artificiality of the in situ study to a great extent and appears to be a useful predictor of demineralization/remineralization interactions.
The histopathology of arrested root caries lesions was examined in extracted human teeth. The main structural characteristics of arrested lesions were the completely mineralized surface area and the formation of a distinct sclerosis of the dentinal tubules. Intertubular dentin was, with the exception of the dentinal tubules, fully mineralized up to the surface. Dentinal tubules near the surface were either filled with ghosts of microorganisms or with crystals of different shapes. Sclerosis of the dentinal tubules was characterized by the presence of three different patterns of intratubular mineralization that occur in distinct regions of the zone of tubular sclerosis. The patterns were distinguishable by the type of crystals and their association with organic structures such as collagenous fibrils or odontoblast processes. It is suggested that arrested lesions are based on (1) the formation of an inner barrier that interrupts the diffusion of substrata from the pulp to invaded bacteria, (2) the formation of an outer barrier by a compact, highly mineralized surface region which blocks the diffusion of products of bacterial metabolism into dentin, and (3) an area of mineralization which extends from the outer barrier toward the root canal within demineralized dentin. The present study demonstrates the considerable potential of caries lesions in dentin to become arrested, and subsequently partially remineralized. These phenomena seem to depend on the severity of an active lesion and its location on the root surface. This should be taken into account when diagnosing root caries lesions. The potential of root caries lesions to become arrested indicates that the treatment concept of active root caries lesions should be reconsidered.
The development of a caries lesion is a dynamic process that includes frequently alternating periods of de- and remineralization, a process for which no in vitro models currently exists. The aim of this study was to develop a model which could repeatedly generate identical pH versus time curves over extended periods of time. To test the model demineralization studies on cementum/dentin were performed. Cementum/dentin blocks were repeatedly subjected to de- and remineralizing solutions delivered by a computerized pump system connected to a pH-meter and a recorder. pH versus time curves similar to those produced in plaque after carbohydrate intake were generated 18 times during 15 h followed by a remineralizing period of 9 h every day for 16 days. The intra-day and inter-day variation of the pH-cycling model were found to be low. The mineral change of the blocks was followed by 125I absorptiometry and the transmission through the blocks during the experimental period increased in average by 1.4 +/- (SE) 0.18%. Microradiographic analysis of the transversal sections of the blocks confirmed the development of lesions resembling root caries.
This study evaluated the preventive effect of four concentrations of fluoride. Twenty-five extracted caries-free anterior teeth from patients aged 50-70 were prepared as overdenture abutments. The teeth were sectioned mesiodistally into two halves. The teeth were covered with a protective varnish, leaving a window on the root surface and one on the cut dentin of the occlusal. The root halves were randomly divided into 5 groups of 10 specimens and each group received a different 5-minute topical treatment prior to being placed in the demineralizing solution. The treatments were: Group 1: distilled H2O only; Group 2: 100 ppm F-, Group 3: 250 ppm F-, Group 4: 500 ppm F-; and Group 5: 1000 ppm F-. The teeth were cycled for 6 hours in a demineralizing solution and for 17 hours in a fluoride-free remineralizing solution. The cycling was maintained for 10 days. The root halves were sectioned and prepared for histologic examination. The depth of the lesions were measured from standardized photo-micrographs by means of a sonic digitizer. The conclusions were: (1) the lesions on the root surface were too small to be measurable, (2) the lesions on dentin were all of similar depth, and (3) the lesions had bands within them and the width of these bands showed a dose response to the fluoride concentration of the topical application.
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