Enamel Area Research Articles

Orthodontic positioner used for home fluoride treatments

It has been well documented that the more time the enamel surface is exposed to fluoride, the higher will be the caries protection. An extremely good method of greatly increasing caries resistance is by daily or weekly home fluoride treatments. This procedure is usually limited to special cases of rampant caries, patients with hemophilia, and handicapped patients in whom caries control is vital. It is not used more widely because of the added costs of impressions, tray fabrication, and professional time. If the patient already has a vehicle for applying fluoride, such as a positioner or mouth guard, it is a simple matter to prescribe or dispense fluoride gel to be used when these appliances are being worn. This is especially true for orthodontic positioners. When bands are removed, a slight space usually exists interproximally. This space greatly facilitates fluoride contact with the proximal surfaces. Fluoride will tend to recalcify decalcified areas of enamel in addition to providing added caries protection for the patient. If positioners are not used after band removal, home fluoride trays or rinses can also be effective. Since many orthodontic patients wear a positioner when bands are removed, the orthodontist can provide his patients with the benefits of topical fluoride by prescribing fluoride gel and explaining how to use it along with his positioner.

Fluoride Concentrations of Surface Enamel before and after Topical Application of Stannous Fluoride in Naval Recruits

AbstractThe inhibitory effect of fluoride on dental caries is well established, but the exact mechanism of caries prevention is unknown. It has been hypothesised that the effectiveness of topically applied fluoride depends upon its ability to incorporate fluoride into tooth enamel. The purpose of this study was to determine the extent of fluoride uptake in enamel achieved by the topical application of stannous fluoride on Naval Recruits.The 112 Naval Recruits were randomly divided into two equal groups for the study. The experimental group underwent supervised toothbrushing with an 8.9 per cent stannous fluoride prophylaxis paste followed by a 15 second application of a 10 per cent stannous fluoride solution. The control group received no fluoride. Enamel samples were taken from one maxillary central inc;sor of each group initially and again 18 hours after fluoride treatment from the opposite central incisor.The in vivo enamel biopsy technique devised by Brudevold and modified by IVIellberg for measuring fluoride concentrations in enamel was used. The samples were obtained by abrading a limited area of enamel, on the labial surface of the maxillary central incisor teeth, with a rotary felt cone and silicone carbide. The slurry was then collected and analysed for calcium and fluoride content, using an atomic absorption spectrophotometer and a fluoride specific electrode, respectively.An increase in fluoride content of 5 per cent for the group with fluoride witheld, and 13 per cent for the group with fluoride applied were not s:gnificant.The average mean depth for enamel samples was 4.7µm ± 0.7. The differences between depths of the various groups was not significant.Although no significant fluoride uptake was found, it was concluded, because of consistent results obtained with the biopsy technique, that it is a useful tool for further studies of his nature.

A microscopical study on destructive process in human enamel

As part of the experiments on enamel destruction planned by our study group, microscopical observation was made on the changes of the destructive process in enamel by EDTA in the acidic range, employing the sandwich method devised by Ishii and Yoshida, as outlined below. Sections approximately 30μ thick of undecalcified teeth were cemented between the slide and cover glass using polyvinylmethylether as the adhesive, with exposure of the surface area of enamel alone. The decalcifying solution was then allowed to act on the enamel surface to study the main changes continuously under the microscope. As the decalcifying solution, 0.01 M EDTA 2 Na solution (pH 4.8) was used with a flow rate of about 1 mm/5 min. The process of change occurred was studied under the phase contrast microscope and recorded by 16 m/m automatic microspeed photographic apparatus. In order to compare the pattern of destruction in the inner enamel layer with that in decalcification with organic acid, 0.1 N acetic acid buffer solution, pH 5.0 was used for decalcification by the same method described above.In both experiments, microradiograms of decalcified specimens were obtained by the contact method.The following results were obtained.1) As to the attack entry on the enamel surface, micro-channels of 1-2 pm in diameter, ends of striae of Retzius and some small defects can be cited. These are identical with those already reported in the study on acid decalcification.2) The spread of destruction was considerably more rapid than that in acid decalcification.3) The degree of destruction was also much more pronounced than in acid decalcification. Due to this reaction, the prismless layer and striae of Retzius have almost no influence the pattern of destruction. Considerable injury appears to be inflicted on the mechanism of recalcification of enamel.

Effect of fluoride on etched human and bovine tooth enamel surfaces as demonstrated by scanning electron microscopy

An experimental area of labial enamel of both human and bovine incisor teeth was treated for 1 min with a solution containing 50 per cent phosphoric acid and 7 per cent (by weight) of dissolved zinc oxide. Several fluoride salts were applied topically for 5 min to the treated area. These included 1 per cent titanium tetrafluoride, 2 per cent zirconium tetrafluoride, 2 per cent sodium fluoride, 2 per cent phosphorulated sodium fluoride and 8 per cent stannous fluoride. The treated surfaces were then coated with gold/palladium and examined in a scanning electron microscope. With the exception of stannous fluoride, a reaction product was demonstrated on the enamel surfaces. Since fluoride salts are known to reduce resin bond strength, it was concluded that the physical presence of a reaction product is a very likely contributing factor.

Caries incidence and orthodontic treatment with fixed appliances

abstract – One hundred and seventy‐three individuals receiving orthodontic treatment according to an edgewise‐light wire technique, wearing full band orthodontic appliances in one or both dental arches, were investigated to determine the incidence of dental caries at the end of the therapy. Topical application of sodium fluoride was used prior to, during, and after the period of active treatment. Thorough instruction in manual toothbrushing with a horizontal scrub technique was given. The carious state of the gingival enamel areas was assessed according to a proposed Caries Index system. The average period of treatment was 19.0 months. A reference group received no form of orthodontic treatment, no tooth‐brushing instruction, nor regular application of fluoride. The results indicate that, on an over‐all basis, the number of new enamel alterations was small, and the total caries frequency was not markedly influenced by the appliances. The vast majority of the carious lesions were observed in comparatively few patients. On the other hand, the distribution of the lesions was significantly different in the reference and in the experimental groups, both with regard to the individual tooth and the individual tooth surface. The bands had a protecting effect on all proximal surfaces and on the completely covered vestibular and lingual surfaces of the molars, while the partly covered vestibular and lingual surfaces of the anterior teeth were subject to an increased caries susceptibility in comparison with the reference subjects. However, most vestibular and lingual lesions were reversed by regular applications of fluoride, or eliminated by slight grinding.

The effect on sound human enamel of exposure to calcifying fluids in vitro.

Previous work showed that after exposure of areas of human enamel to calcifying fluids <i>in vitro</i> for periods of up to 24 weeks, experimental areas were more resistant to artificial caries than were untreated control areas. In the present experiments, teeth were exposed to calcifying fluids for shorter periods. 30 erupted and 30 unerupted caries-free human permanent teeth were slit in half longitudinally and the cut face on each varnished. One half was randomly selected as experimental and exposed to a calcifying fluid for periods from 1 to 10 days. The controls were exposed to de-ionised water, both fluids being renewed every 24 h. Calcifying fluids were prepared from synthetic hydroxyapatite (Ca/P 1.63) having calcium concentrations of either 1.0, 1.5 or 3.0 mM/l with phosphate at 1.8 or 2.9 mM/l. All calcifying fluids contained 200 mM sodium chloride/l and were used at pH 7.4. In some experiments, fluoride at a level of either 0.05 or 0.50 mM/l was added. After experiment, sections through experimental and control areas were examined with polarised light using an Ehringhaus compensator after imbibition with Thoulet’s medium (n=1.62). It was possible to increase the negative intrinsic birefringence of erupted enamel, to a depth of 20 μm from the enamel surface, by an average of 13.2% relative to control areas. With unerupted enamel, the corresponding average increase in the surface tissue was 18.3%. In addition, an average of 9.8% increase was found at a depth of 100 μm into the enamel on unerupted teeth. The presence of fluoride greatly enhanced the mineralising ability of the calcifying fluid. Ultra-thin sections cut perpendicular to the tooth surface revealed a firmly adherent precipitate on the enamel surface and within small wedge-shaped defects. Apart from changes within the enamel, this surface precipitate may be sufficient to retard caries formation by providing a reserve of calcium phosphate and by acting as a diffusion barrier.

Experimental caries in man.

The purpose of the present study was to develop a method for short-term caries trials in man, using an experimental model already employed in periodontal research. Twelve students were given prophylaxis and instruction to practice meticulous oral hygiene until Plaque Index and Gingival Index approached zero. The carious state of the bucco-gingival enamel areas, excluding molars, was evaluated using a dissection microscope. The cleaned and dried tooth surfaces were scored according to the Caries Index system. During a period of 23 days without oral hygiene 6 participants performed 9 daily mouthrinses with 10 ml of a 50% sucrose solution. At the termination of this period the sucrose group demonstrated a higher mean Caries Index and a greater number of new early lesions than the six control subjects. The mean Plaque Index scores were higher in the sucrose group, whereas the Gingival Index scores were similar for both groups. Smears of plaque showed no significant differences in the percentage distribution of various types of microorganisms. After 30 days of oral hygiene and daily mouthrinses with 0.2 % NaF, fair agreement was found between the Caries Index scores of the two groups. Similar observations were made after a second hygiene and fluoride period. The results demonstrate that it is possible to produce detectable carious alterations within 23 days by abolishment of oral hygiene and frequent sucrose additions and that these alterations are reversible.

The 32p uptake and the hardness of unabraded, abraded and exposed human enamel surfaces

Abraded facets were made in enamel surfaces of teeth in situ and exposed to the oral environment for periods of 1–82 days. After extraction, the in vitro uptake of 32P was measured in selected enamel areas representing unabraded, abraded, and exposed surfaces. This part of the material comprised fifty-two premolars from children, and in eighteen of them the micro indentation hardness was also determined. Furthermore, the hardness was measured in unabraded and abraded surfaces of eight teeth from old individuals. The results showed that in the young teeth, the unabraded surfaces took up less 32P and were softer than the abraded facets. Oral exposure of such facets resulted in impeded 32P uptake and increased hardness. The old teeth were generally harder than the young teeth, but the unabraded surfaces of the old teeth were not significantly harder than the abraded facets.

Chemical composition of different areas of the enamel of deciduous and permanent teeth. (The content of Ca, P, CO2, Na and N2).

Chemical composition of different areas of the enamel of deciduous and permanent teeth. (The content of Ca, P, CO2, Na and N2).

The development and regression of hypomineralized areas of rat molars

Hypomineralized areas in enamel which stain with silver nitrate in a manner indistinguishable from incipient carious lesions are present in rats 20–22 days old. The number and severity of these areas is decreased by maintaining the animals on a commercial laboratory chow diet for a period of 70 days, indicating that mineralization of the hypomineralized areas occurs under these conditions. Animals placed on a cariogenic diet showed an increase in number and severity of incipient lesions elaborated by the silver nitrate. The experiment was not designed, however, to distinguish whether some mineralization had occurred in the presence of the active caries formation. Phosphate supplementation of the cariogenic diet resulted in a decrease in number and severity of hypomineralized areas compared with an unsupplemented diet, demonstrating that phosphate either decreases the rate of formation and progress of lesions or favours mineralization. The possibility that topically applied agents such as fluoride may have a mineralizing, as distinguished from a cariostatic, action is discussed.

Electron microscopic study on the hypomineralized enamel areas descending from the floors of occlusal fissures toward the amelo-dentinal junctions.

In 1963 the present author had investigated in detail through electron microscopy the enamel regions around the pits [1]. As a consequence, a conclusion was drawn that most of the enamel areas around the pits, in particular those close to the frequent floors of the pits, are made up of rodless portions of enamel. He stated that distinction here is quite difficult to make in most cases between enamel rods and interrod substance due to a considerable hypomineralization.The pits and fissures have been generally held to be portions which will be most easily affected by a carious lesion. However, most of their histological examination has been done by means of ordinary light microscopy and except for AWAZAWA'S description on the pits, there is no availab'e research result touching on the occlusal fissures made by electron microscopy. Therefore, an electron microscopical investigation on the enamel around the fissures is full of interest, as it helps our understanding of histologic peculiarities of the enamel portions adjoining the floors of fissures.The present study is designed to make clear the enamel areas adjacent to the occlusal fissures, especially those hypomineralized enamel portions descending to various extents from their floors toward the amelo-dentinal junctions, examined in detail by the electron microscope. Through this research, he could secure some interesting images from these portions.

Correlation between tetracycline binding and mineralization in dentin and enamel.

AbstractExperiments were conducted on the incisor of young rats to show (1) the precise areas and manner in which the tetracycline fluorophore combines with dentin and enamel and (2) the relation between the tetracycline localization and mineralization. For the objectives mentioned above rats were injected with tetracycline and a combination of tetracycline and Ca45. Detailed examination of the teeth of specimens injected with tetracycline show a rapid uptake and localization of fluorophore in areas undergoing mineralization. Areas adjacent to the increments undergoing mineralization also reveal the presence of the fluorophore, but to a lesser extent. Comparison of the same area of the tooth injected with tetracycline and Ca45 show that the fluorophore is localized exclusively in areas undergoing mineralization, and to a lesser extent in adjacent, incompletely mineralized regions.Despite the fact that our observations have demonstrated the avidity tetracycline exhibits for mineralizing and recently mineralized areas of dentin and enamel, we have not been able to exclude the possibility that the fluorophore may combine with the organic matrix of these tissues as well as the mineral component.

Microradiographic and microhardness studies of developing enamel

This study was undertaken on human and Rhesus monkey enamel using three methods of analysis to gain information concerning the pattern of enamel calcification: (1) microhardness pattern of enamel mineralization; (2) microradiography; and (3) plastic substitution studies. Halves of teeth were selected and tested on a Tukon Microhardness Tester with a Knoop Diamond Indentor. The other half of each tooth was further sectioned. Several sections from each tooth were ground to less than 150 μ in thickness and microradiographs were taken; the remainder were used for the substitution studies. All organic tissue and water were removed from the sections and replaced with plastic. Decalcification of these sections revealed areas of low and high organic and water content. It was found that mineralization of the enamel matrix begins at the dentino-enamel junction and proceeds peripherally, thus following the incremental pattern of formation of the enamel matrix. Final calcification is completed after the matrix is completely deposited and follows this same pattern from the dentino-enamel junction peripherally. The enamel rod matrix becomes calcified before the interrod substance, the latter thus presenting pathways for diffusion of tissue fluid containing calcium and phosphate ions, during the mineralization process. The interrod substance is the first area of enamel to be altered in dental caries. Thus the steps in enamel destruction are in reverse order to those in enamel formation.

Identification of hypocalcified and demineralized areas in sections of human enamel.

HITHERTO, poorly calcified areas in the enamel of ground sections of teeth have been detected either by their permeability to stains, insolubility in dilute acid or by their low absorption of soft X-rays (so-called Grenz-rays). Gottlieb, Diamond and Applebaum1 came to the conclusion that “it is impossible by means of microscopic ground section study, to differentiate between enamel in the matrix stage and fully calcined enamel”. During the preparation of ground sections of teeth with obviously poorly calcified areas of enamel, we were struck by the appearance of these areas when sections were examined in water by transmitted and reflected light. By transmitted light they appear opaque, while the normal enamel is translucent or transparent; by reflected light they appear white. When cleared and mounted in the routine histological manner, they become translucent, and it is often difficult to distinguish them from normal transparent or translucent enamel, but they can be distinguished from pig-mented enamel by the lack of brown pigmentation. Using these criteria, we were able to show, in proved cases of immature acid-insoluble enamel, almost complete agreement between the dark areas in the water-mounted sections and those observed on an X-ray negative after exposure to soft X-rays (Figs. 1 and 2). The soft X-rays used were produced by a commercial type ‘Raymax’ tube with a tungsten target and operated at 20 kV. peak and about 3 m.amp. emission current.

The width, the enamel surface area, and the volume of the crown of the deciduous and the permanent teeth

1. 1. Comparable teeth on the right and left sides of the median line on the same individual are approximately the same size. 2. 2. The maxillary and mandibular teeth of an individual are almost the same size. 3. 3. A full set of permanent teeth have about three times as much volume and exposed enamel area as a full set of deciduous teeth. 4. 4. The permanent teeth which replace the deciduous teeth have about twice as much volume and exposed enamel area as do the deciduous teeth. 5. 5. The width of the anterior deciduous teeth is less than the width of the succeeding permanent teeth, but the posterior deciduous teeth are wider than the succeeding permanent teeth.

Changes in the Teeth of White Rats Given Water from a Mottled Enamel Area Compared with Those Produced by Water Containing Sodium Fluoride

Changes in the Teeth of White Rats Given Water from a Mottled Enamel Area Compared with Those Produced by Water Containing Sodium Fluoride