Acid Resistance Of Enamel Research Articles

Acid resistance of human enamel in vitro after bicarbonate application during remineralization

Objectives: The aim of this study was to investigate the acid resistance of subsurface enamel lesions remineralized with bicarbonate solutions during remineralization. Methods: Two experiments were carried out. In experiment 1, mineral uptake and acid resistance of remineralized enamel lesions were analyzed quantitatively by microradiography for mineral changes. Bicarbonate solutions of 0.5, 5.0 and 50.0 mM were used. In experiment 2, to clarify acid resistance mechanisms, the pH changes in demineralizing solutions on the remineralized enamel surfaces were measured continuously. Only a bicarbonate solution of 5.0 mM was used. Results: In experiment 1, the bicarbonate-treated groups were more acid resistant than the non-treated groups ( p<0.05). However, no statistically significant difference was observed among the different concentrations of bicarbonate. In experiment 2, the pH rise of the bicarbonate group was greater than the other groups. Conclusion: It was found that bicarbonate-treated enamel lesions were resistant to acid. It would suggest that bicarbonate ions applied during remineralization may have penetrated into the subsurface lesions. These ions may have worked as buffer agents against the acid challenge and inhibited the decrease in pH.

Study on acid resistance of human dental enamel and dentin irradiated by semiconductor laser with Ag(NH3)2F solution.

The purpose of this study was to investigate the acquired acid resistance of human dental enamel and dentin treated by 38% diamine silver fluoride [Ag(NH3)2F] solution and semiconductor (diode) laser irradiation in vitro. There have been no reports on the acid-resistant effect by combined use of fluoride and semiconductor laser. Sixty crowns of extracted human molars were divided into two groups for enamel and dentin samples, and each group was subdivided into three subgroups of 10 each. Each subgroup of enamel and dentin samples served as a control; one was treated with Ag(NH3)2F and the other was treated with Ag(NH3)2F and semiconductor laser irradiation at 2 W for 30 sec. Then all samples were immersed in 5 ml of 0.1 M lactic acid (pH 4.8) at 37 degrees C for 24 h. The concentration of calcium ion (Ca2+) dissolved in the solution was measured by atomic absorption spectrophotometry, and the samples were observed by stereoscopy and scanning electron microscopy (SEM). In both enamel and dentin samples, dissolved Ca2+ concentration in Ag(NH3)2F- or Ag(NH3)2F- and laser-treated group was significantly decreased compared with that in the control (p < 0.01). SEM findings showed that numerous cubic particles ranging from 0.1 to 0.5 mcirom were observed only in the combined treated groups of both enamel and dentin samples. A significantly decreased solubility of human enamel and dentin was acquired after treatment by Ag(NH3)2F and semiconductor laser irradiation, which suggested that this combined use has the capability of a more efficient acid-resistant effect on human dental hard tissues.

A study on acquired acid resistance of enamel and dentin irradiated by Er,Cr:YSGG laser.

This investigation was performed to evaluate the acid resistance of lased enamel and dentin by Er,Cr:YSGG laser to artificial caries-like lesions by spectrophotometry, and the ultrastructure of lased areas was investigated by scanning electron microscopy (SEM) in vitro. In recent years, many studies have been performed to evaluate the effects of Er,Cr:YSGG laser on dental hard tissues. However, there have been only a few studies to determine if this laser is suitable for caries preventive treatments. An Er,Cr:YSGG laser was used to irradiate the enamel or dentin samples from 30 extracted human molars at 6 W (67.9 J/cm2) or 5 W (56.6 J/cm2) pulse energy, respectively, with or without water mist. Samples were subjected to 2 microl of 0.1 M lactic acid solution (pH 4.8) for 24 h at 36 degrees C. The parts per million (ppm) of calcium ion (Ca2+) dissolved in each solution was determined by atomic absorption spectrophotometery, and the morphological changes were investigated by SEM. The lowest mean Ca2+ ppm was recorded in the lased samples. SEM observation showed that the lased areas were melted and seemed to be thermally degenerated. After acid demineralization, the thermally degenerated enamel or dentin surfaces were almost unchanged. The results of this study suggested that Er,Cr:YSGG laser irradiation with and without water mist appears to be effective for increasing acid resistance.

Na_2PO_3F/竹塩配合歯磨剤のbovine enamelへのフッ化物の取り込みと酸抵抗性のin vitroでの評価

Na_2PO_3F/竹塩配合歯磨剤のbovine enamelへのフッ化物の取り込みと酸抵抗性のin vitroでの評価

Transformation of hydroxyapatite to fluorapatite by irradiation with high-energy CO2 laser.

High-energy laser irradiation has been shown to cause crystalline transformations in apatites, which may lead to the formation of tricalcium phosphates with a resulting decrease in acid resistance. Depending on the nature and energy density of laser irradiation used, however, an increase of acid resistance of dental enamel has also been reported after laser irradiation. The aim of the present study was to investigate the phase transformation of hydroxyapatite (HA) to fluorapatite (FA) in a model system that incorporates sodium fluoride (NaF) into apatite structure by using laser irradiation. A CO2 laser was used at energy densities ranging from 21 to 500 J/cm2. Synthetic HA mixed with NaF (10:1) was the target of laser irradiation. The crystalline structures were then investigated using X-ray diffraction analysis. The results showed that a phase transformation of HA to FA could be realized, and that the threshold energy density needed was 38 J/cm2. Not only is the finding crystallographically important, but it also opens new perspectives for future research regarding the development of laser technology for clinical purposes.

Effects of several tea components on acid resistance of human tooth enamel

Objectives: The effects of tea components on the acid resistance of human tooth enamel were investigated by an in vitro experiment. A further study focused on the action of tannin, the main component of tea, in combination with fluoride. Results: Some components such as tannin, catechin, caffeine and tocopherol were demonstrated to be effective for increasing acid resistance, and their effects increased dramatically when they were used in combination with fluoride. A mixed solution of tannic acid and fluoride showed the highest inhibitory effect (98%) on calcium release to an acid solution. Tannin in combination with fluoride showed obvious inhibition of the formation of artificial enamel lesions in comparison with APF as determined by electron probe microanalysis, polarized-light microscopy and Vickers microhardness measurement. Conclusions: These results demonstrate that besides the fluoride, the organic components of tea also possess the property of increasing the acid resistance of tooth enamel. They also suggest that the organic components appear to play a primary role in their actions rather than fluoride.

The Effect of Normal Pulsed Nd-YAG Laser Irradiation on Pits and Fissures in Human Teeth

The effects of normal pulsed Nd-YAG laser irradiation on the acid resistance of human dental enamel of pits and fissures, the cleaning of the pit and fissure contents and fluoride uptake into deep pits and fissures were examined. The acid resistance of the pit and fissure enamel was evaluated by the amount of dissolved calcium per square millimeter of the surface area. The pit and fissure enamel treated with laser irradiation obtained an acid resistance 30% higher than that of the unlased controls. The cleaning effect of laser irradiation on the pit and fissure contents was compared with chemicomechanical and mechanical methods. The laser irradiation was found to clean the pits and fissures to a greater depth without alterating the shape of pits and fissures, compared with the other two methods. The distribution of calcium, phosphorus and fluoride in the enamel of the pits and fissures was then measured by electron probe microanalyzer. At the entrance and in the deep part of the pits and fissures, the fluoride content of the enamel treated with acidulated phosphate fluoride after laser irradiation was higher than that of the enamel treated with acidulated phosphate fluoride alone. These results thus suggest that Nd-YAG laser irradiation might be effective in increasing the acid resistance of the pit and fissure enamel, while removing the pit and fissure debris contents and increasing the fluoride uptake into the pit and fissure enamel.

レーザー照射‐再石灰化エナメル質における耐酸性能の変化

The aim of this study was to examine the change in acid resistance of lased-remineralized enamel. Sixty-six enamel slabs were prepared from thirty-three human premolars. These enamel slabs were demineralized artificially. They were irradiated with a Q-switch Nd-YAG laser and remineralized with two remineralizing solutions, one with and the other without fluoride. To evaluate acid resistance, the enamel slabs were subsequently immersed in 0.1M lactic acid solution (pH 4.5) while stirring (139r.p.m. ±12; Mean±S.D.), and dissolved Ca2+ was measured as a function of time from 15min to 180min.The results were as follows:1) Laser irradiation increased acid resistance of demineralized enamel during short periods (up to 60min).2) Remineralization without fluoride increased acid resistance of demintralized enamel during short periods (up to 60min) regardless of laser irradiation.3) Remineralization with fluoride increased acid resistance of demineralized enamel during long periods (up to 180min) regardless of laser irradiation.

Acid Resistance of Lased Human Enamel with Erbium:YAG Laser

Abstract Tooth enamel was exposed to Er:YAG laser. The laser beam was absorbed onto the enamel without black paint and caused acid resistance of the enamel. Alteration of the enamel surface was similar to that of Nd:YAG laser irradiation. Extent of acid resistance of enamel surface or subsurface enamel was higher in Er:YAG laser than that of Nd:YAG laser.

An Incremental Effect of Acid Resistance and Remineralization on Incipient Caries of Enamel with Laser Irradiation

The authors have demonstrated that a normal pulsed Nd: YAG laser was the most suitable among the lasers to produce resistance against acid decalcification of human tooth enamel, and a combined treatment of laser irradiation and fluoride application onto the enamel obtained most remarkale acid resistance.It is interest to determine whether the use of laser and fluoride in combination is a more effective procedure for incipient caries prevention.Artificial caries-like lesions were made on human enamel, and the enamel was then treated with laser irradiation and APF (acidulated phosphate fluoride). The laser used in this study was a normal pulsed Nd YAG laser which has 0.3 msec pulses with a pulse energy of 0.2 J/pulse. The tooth enamel was lased at a repitition rate of 20pps and total enegy density of 40J/cm2.The acid resistance of the enamel was determined by the amount of dissolved calcium from the enamel surface in the acidic solution. Fluoride uptake in the enamel was examined by mean of EPM (electron probe microanalyzer). Remineralization of the enamel was measured by microradiographic technique and microhardness test. The following results were obtained.1) An increment in acid resistance of enamel was caused by laser irradiation alone and also fluoride treatment after laser irradiation.2) In the case of fluoride treatment after laser irradiation, the fluoride uptake into the surface and subsurface enamel was higher than in the cases of fluoride treatment alone.3) The remineralization was remarkable in the cases of laser irradiation and fluoride treatment after laser irradiation groups. The extent of remineralization was seen from the surface to the bottom of the lesion area.

歯科領域における新しいレーザー治療

Recently, lasers are extensively applied in many clinical fields of medicine. In the field or dentistry, laser has not been prompted for clinical application until 1975. However, lasers are gradually utilized for clinical fields or dentistry.The authors have demonstrated that a normal pulse Nd:YAG laser was the most suitable among the lasers to produce a resistance against acid decalcification of human teeth enamel. A combined treatment of laser irradiation and fluoride application onto the enamel obtained most remarkable acid resistance. Fluoride application after laser irradiation produced a greater fluoride uptake in the enamel than fluoride application alone. Similar results acre obtained from the in vitro and in vivo experiments on incipient dental caries with the subsurface demineralization or human enamel. The inhibitory, effect on enamel demineralization and enhancing effect on enamel remineralization of incipient caries lesion were obtained laser irradiation alone and in combination with fluoride.The mechanism of acquired acid resistance of lased enamel was investigated. The contents of water, carbonate and organic substances were reduced in lased enamel and lased enamel showed a highly positive birefringence, suggesting the formation of 'microspaces' in enamel. It was suggested that laser irradiation might create the microspaces which could act as sites for trap of ions released by an acid attack.These results suggest that the application normal pulse Nd:VAG laser is a practical and useful procedure for the prevention or dental caries.Furthermore, a new method of caries removal and cavity preparation without thermal damage using a laser is under development.

A Possible Mechanism of Acquired Acid Resistance of Human Dental Enamel by Laser Irradiation

A possible mechanism of acquired acid resistance of lased enamel was proposed on the basis of the investigations of optical properties, compositional and structural changes and permeability of lased and unlased human dental enamel. Lased enamel showed a high positive birefringence, suggesting the formation of 'microspaces' in enamel. No new products were found, though a decrease of lattice strain and a slight a-axis contraction were recognized in lased enamel compared with unlased enamel. The contents of water, carbonate and organic substances were reduced in lased enamel. Gradual changes of birefringence were observed in lased enamel during treatment with acid solutions, and this change was attributed to mineralization of the microspaces. The ions released by an acid decalcification would be trapped in the microspaces in lased enamel, whereas such ions diffuse to the surrounding solution in unlased enamel.

Effects of Nd: YAG Laser Irradiation on Acid Resistance of Defective Rat Enamel

Effects of Nd: YAG Laser Irradiation on Acid Resistance of Defective Rat Enamel

Combined effects of laser and fluoride on acid resistance of human dental enamel.

Specimens of human dental enamel were topically applied with solutions of sodium fluoride (NaF) or acidulated phosphate fluoride (APF) before and after laser irradiation. APF application after laser irradiation caused a remarkable increase in acid resistance of the enamel, while APF application before laser irradiation showed a lesser effect, similar to either APF treatment alone or laser irradiation alone. These results were consistent with observations made using a scanning electron microscope. APF application after laser irradiation produced a greater fluoride uptake in the enamel than APF application before laser irradiation, as shown by electron probe microanalyzer. NaF application caused lesser acid resistance and lesser fluoride uptake than APF application, even when the enamel was treated with laser irradiation.

エナメル質形成不全歯へのレーザー照射による耐酸性付与に関する実験的研究

エナメル質形成不全歯へのレーザー照射による耐酸性付与に関する実験的研究

ＹＡＧレーザー照射による，ラットのう蝕予防効果に関する研究

This study was carried out to investigate whether c. w. (continuous wave) Nd: YAG laser irradiation might increase acid resistance of enamel in extracted rat molars and prevent dental caries in rats in vivo.The laser was directed on to the normally erupted or prematurely exposed upper left first molars of rats. The upper right first molars of the same animals served as controls.The acid resistance of enamel was increased by laser irradiation in the normally erupted and prematurely exposed teeth. The normally erupted teeth gained more acid resistance than the prematurely exposed teeth.Laser irradiation twice (once a day for two days) effective by reduced dental caries in the normally erupted teeth as compared to the control side. The same dose of irradiation on the prematurely exposed teeth, however, failed to reduce dental caries significantly. Irradiation four times (once a day for four days) reduced dental caries on the prematurely exposed teeth significantly. Laser irradiation after the treatment with 2% NaF on the prematurely exposed teeth inhibited dental caries incidence significantly, compared with NaF treatment or laser irradiation only. These results suggest that c. w. Nd: YAG laser irradiation is effective in preventing dental caries.

Fluoroprophylaxis of dental caries by phonophoresis

Our preliminary studies have shown that using ultrasound it is possible to introduce fluoride into the teeth 3 times more than by application, resulting in a significant increase in the acid resistance of enamel. The aim of the present work was to develop a technique and evaluate the anti-cariousness effectiveness of sodium fluoride ultraphonophoresis.

Caries-preventive effect of a stannous fluoride dentifrice containing sodium phytate in hamsters

The effect of a new preparation of the stannous fluoride dentifrice on dental caries development was examined in an animal caries model.Golden hamsters aged 27 days were intraorally infected with cariogenic Streptococcus mutans K1-R and reared on the caries-inducing diet #2000 for 32 days. During the experimental period, the molars of the animals were brushed for 1 min. once a day, 5 days a week, with a 0.41% stannous fluoride dentifrice containing 0.88% sodium phytate, a 0.41% stannous fluoride dentifrice alone, or a placebo dentifrice. At the end of the experiment, the animals were killed, and plaque accumulation and lesions on the molars were evaluated.Daily application of the SnF2-phytate dentifrice significantly inhibited caries development and plaque formation; when compared to the placebo dentifrice-treated group, the SnF2-phytate dentifrice-treated group showed 49.2% reduction of caries development, which was much greater than the 32.2% reduction in the SnF2 dentifrice group. Similarly, reduction of plaque formation was 24.5% for the SnF2-phytate dentifrice group and 8.5% for the SnF2 dentifrice group.The high caries-inhibitory and plaque-inhibitory capacities of the SnF2-phytate dentifrice may be due to the synergistic enhancement of both the acid resistance of enamel and the anti-plaque action exerted by combination of the curative ingredients, fluoride, stannous and phytate ions.

エナメル質耐酸性付与に及ぼすYAGレーザー照射とフッ化物塗布の併用効果

Synersistic effect of laser irradiation and fluoride application on acid resistance of dental enamel was investigated. Sound human enamel specimens were soaked into an acidurated phosphate fluoride solution (APF) for 24 hours after irradiation of normal pulse Nd-YAG laser with an energy density 50J/cm2. The enamel was obtained a remarkable resistance against acid decalcification compared with specimens of fluoride application alone and laser irradiation alone. The acquired zone of acid resistant of enamel reached from the enamel surface to 100μm in depth.

Enamel Fluoride Uptake and Acid Resistance in Subjects with High and Low Experimental Cariogenicity

The response of bovine enamel to intra-oral cariogenic environments was studied in human volunteers. Enamel slabs were mounted in dentures and treated with either 10% sucrose or 10% sucrose plus 20 ppm fluoride mouthrinses for one minute five times daily. After one week, these enamel slabs were studied for change in surface hardness and for the degree of fluoride incorporation, or for their resistance to acid acquired by the intra-oral exposure. Among the eight subjects, those with the highest experimental cariogenicity exhibited the highest benefit of enamel from the fluoride in terms of fluoride incorporation and in their resistance to the subsequent acid test. The results suggest that cariogenic activity and fluoride will synergistically improve the tooth resistance to subsequent attack, apparently through mineral exchange that favors the formation of acid-resistant minerals with high fluoride content within enamel lesions.