Effect of dentinal fluid composition on dentin demineralization in vitro

Dentin demineralization is reduced by perfusion with water. We hypothesized that a simulated dentinal fluid (SDF) that contains albumin, in addition to electrolytes, would be more effective in reducing dentin demineralization than water alone, and this effect would increase with increasing flow rate of SDF. Perfusion rate in tooth segments that carried buccal cervical dentin windows was measured in a fluid transport set-up. These windows were then demineralized under perfusion with water, or SDF at 1.47 kPa for 31 days. We analyzed integrated mineral loss and lesion depth with the use of transverse microradiography (TMR), which revealed that 38% more mineral dissolved from dentin lesions perfused with water than from those perfused with SDF. The former were also 18% deeper. Flow rate of dentinal fluid showed no correlation with demineralization. We concluded that composition of dentinal fluid is an important determinant of the rate of lesion formation and progression in dentin.     

马尾松松针提取物对根面牙本质脱矿影响的体外研究

目的评价马尾松松针提取物（PMNE）抑制根面牙本质脱矿的效果。方法将根面牙本质块根据pH循环中所用实验溶液随机分为去离子蒸馏水（DDW）组,氟化钠（NaF）组,4%、8%和12%PMNE组,试件进行为期8 d的pH循环。显微CT选区测定各组未脱矿牙本质和脱矿牙本质的牙本质矿物密度（DMD）及两者DMD差值（ΔDMD）,扫描电镜下观察pH循环后牙本质表面形貌。结果PMNE各组和NaF组ΔDMD均显著低于DDW组（P<0.05）,且8%PMNE组和12%PMNE组ΔDMD组间差异无统计学意义（P>0.05）,均显著低于4%PMNE组,高于NaF组（P<0.05）。扫描电镜见PMNE组牙本质小管不全暴露,小管开口程度明显小于DDW组,大于NaF组。结论PMNE可抑制根面牙本质脱矿,减缓酸对DMD的降低,具有一定的抗龋活性。8%PMNE即可达到较好抑制脱矿的效果。     

Effect of ethylene oxide sterilization on enamel and dentin demineralization in vitro

For in situ studies into caries prevention, sterilization of tooth samples is essential. However, sterilization may influence the caries process itself. The aim of this study was to assess the effect of sterilising sound human enamel and dentin with ethylene oxide on lesion depth and mineral loss before and after in vitro demineralization. Lesion depth and mineral loss were measured using transversal microradiography (TMR). The experiment was carried out with 32 enamel and 32 dentin samples. We found a significant reduction of lesion depth due to sterilization in demineralized enamel (-9.8microm; 95% CI: -15.1 to -4.4microm). The small effect of sterilization on demineralized enamel is considered to be irrelevant for in situ studies of de- and remineralization.     

Effect of high fluoride concentration on bovine dentin demineralization in narrow grooves in vitro

Previously, a dentin groove model was developed to investigate caries at plaque retention sites, such as marginal gaps, and pits and fissures. The aim of the present study was to investigate the in vitro effect of fluoride on the demineralization of dentin in the depth of the grooves at various distances from a freshly prepared resin-modified glass ionomer cement (RMGIC), which was used as the source of high fluoride release. Three parallel grooves (280 microm wide x 500 microm deep) were cut in the labial surface of 20 bovine coronal dentin discs. In 10 discs, the surface area (approximately 6 mm2) between the first groove and the edge of the disc was covered with RMGIC. The discs were exposed to an acidified methylcellulose gel system for 1 or 2 wk. Changes in mineral content were obtained by transverse microradiographic analysis. The results showed that integrated mineral loss (IML) was reduced up to 60% in the RMGIC groups, although the lesion depth was not significantly influenced by RMGIC. The pattern of demineralization differed between groups: the subsurface lesions in RMGIC groups did not decrease in IML towards the base of the groove to the same degree as in the control groups. It is concluded that high amount of fluoride inhibits loss of mineral, while not affecting the lesion depth. The homogeneity of the lesions with depth in the RMGIC group may be explained by a fluoride-induced inhibition of demineralization at the entrance of the grooves.     

Influence of olive oil emulsions on dentin demineralization in vitro

The effect of two different concentrations of olive oil emulsions on development of artificial caries-like dentin lesions under severe demineralizing conditions was investigated. Bovine dentin samples (n = 180) were ground flat, polished, divided into four groups, and subjected to three demineralization cycles per day. Samples were stored in one of the following solutions for 5 min prior to demineralization in a buffer solution (pH 5): Group 1: 50% oil emulsion (olive oil and distilled water); group 2: 5% oil emulsion; group 3: distilled water; and group 4: 1,500 ppm sodium fluoride. Daily up to 9 days, lesion depth (ld) and mineral loss (deltaZ) were determined by means of microradiography and analyzed by ANOVA and Tukey's studentized range test (p < or = 0.05). Lesion depth increased with time for all groups. Mineral loss increased in groups 1-3. A small but significant decrease in mineral loss was observed following treatment with lipid emulsions as compared to treatment with distilled water, but fluoride treatment was considerably more effective. Mean mineral loss (means +/- SD in vol% x microm) averaged over the study period was 4,368 +/- 1,599, 4,536 +/- 1,823, 4,849 +/- 1,798, and 789 +/- 177 for group 1, 2, 3, and 4, respectively. Ratio (deltaZ/ld) remained constant around 30 vol% for groups 1-3, but decreased for group 4. In conclusion, externally provided lipids have the potential to reduce dentin demineralization in vitro.     

Influence of glutardialdehyde on dentin demineralization in vitro and in vivo

In this paper the results are presented on the action of glutardialdehyde (GDA) on the in vitro demineralization of human dentin and on the in vivo demineralization of dentin using the Ogaard orthodontic banding system. The results show that a 2 min application of a 2% GDA solution at pH = 3.6 reduces dentin demineralization in vitro and in vivo substantially. Microradiography shows a percentage reduction of lesion depth and mineral loss in vitro of 20 and 36%, respectively. After 2 wk in vivo demineralization the same percentage reductions are 60 and 44%, respectively. The mechanism of action of GDA on dentin is not certain yet. Presumably the in vitro action is due to surface cross-linking of the dentin matrix causing reduced Ca and phosphate transport out of the dentin. In vivo an additional effect may be a rather short term influence of GDA on plaque or on plaque accumulation. The results of this paper indicate that glutardialdehyde is an interesting agent to consider in the reduction of root caries.     

Influence of glutardialdehyde on dentin demineralization in vitro and in vivo

Abstract – In this paper the results are presented on the action of glutardialdehyde (GDA) on the in vitro demineralization of human dentin and on the in vivo demineralization of dentin using the Ögaard orthodontic banding system. The results show that a 2 min application of a 2% GDA solution at pH = 3.6 reduces dentin demineralization in vitro and in vivo substantially. Microradiography shows a percentage reduction of lesion depth and mineral loss in vitro of 20 and 36%, respectively. After 2 wk in vivo demineralization the same percentage reductions are 60 and 44%, respectively. The mechanism of action of GDA on dentin is not certain yet. Presumably the in vitro action is due to surface cross-linking of the dentin matrix causing reduced Ca and phosphate transport out of the dentin. In vivo an additional effect may be a rather short term influence of GDA on plaque or on plaque accumulation. The results of this paper indicate that glutardialdehyde is an interesting agent to consider in the reduction of root caries.     

In vitro dentin demineralization inhibition effects of an experimental fluoridated HEMA and water wetting agent

The ability of fluoride-releasing resins to inhibit dentin demineralization remains controversial. The purpose of this study was to evaluate the caries inhibition of resin composite restorations with an experimental fluoridated hydroxyethyl methyl methacrylate (HEMA) and water wetting agent. Standardized Class V preparations were placed in 40 molars, the gingival margin placed below the cementoenamel junction. Two dentin primers (sodium fluoride, HEMA and water; HEMA and water) were placed in equal numbers of 20 preparations, then One-Step Dental Adhesive (Bisco) was applied as recommended by the manufacturer, followed by the placement of a resin composite restoration. Amalgam restorations with no primer/adhesive were placed in 10 preparations and 10 preparations were restored by placing One-Step Dental Adhesive, then resin composite. All teeth were subjected to an artificial caries challenge (pH 4.4) for 5 days. Results demonstrated the mean areas (microm2 +/- s.d.) of demineralization 100 microm from the restoration/dentin margin to be: amalgam 5,570 +/- 873; One-Step 7,038 +/- 2,099; HEMA and water 6,126 +/- 634; fluoridated HEMA and water 3,411 +/-593. ANOVA and Duncan's test (P < 0.05) demonstrated the fluoridated HEMA and water wetting agent to have significantly less adjacent dentin demineralization than the other three groups. Eighty percent of HEMA and water wetting agent, 80% of One-Step Dental Adhesive and 100% of amalgam restorations demonstrated wall lesions. One hundred percent of restorations with fluoridated HEMA and water wetting agent demonstrated inhibition zones in adjacent dentin.     

Effect of demineralization and remineralization on microhardness of irradiated dentin

The aim of this in vitro study was to evaluate the effects of irradiation and fluoridation on the demineralization and remineralization patterns of root dentin. From the cervical regions of 84 bovine incisors, each of four dentinal blocks were prepared and randomly assigned to four groups: 1) no irradiation; 2) irradiation of specimens up to 60 Gy (2 Gy/d, 5 d/w); 3) no irradiation, but fluoridation of specimens for 5 min/d with Elmex Gelée; and 4) irradiation and daily fluoridation of specimens for 5 min/d. Subsequently, the specimens were demineralized for 2, 4, 6 or 8 days with acidulated hydroxyethylcellulose (n = 21), and Knoop hardness numbers (KHN) were determined before, as well as after the demineralization period. Then seven specimens from each group were fluoridated with one of three fluoride gels (Elmex Gelée [1.25%], STOP [0.4%], Fluoridgel [1.25%]; 2 x 15 min/d, 10 d), and immersed in synthetic saliva at a temperature of 37 degrees C. Finally, KHN for all specimens were determined. Irradiation resulted in a significant decrease in microhardness. There was a reduction in microhardness with increasing demineralization time in all groups. The highest percentage decrease in microhardness could be observed with group 1. Due to the preceding decrease of KHN in the irradiated specimens (group 2), these samples showed less percentage reduction in microhardness during demineralization when compared to group 1 (ANOVA; p < 0.001). The decrease in microhardness was significantly hampered by fluoridation in the non-irradiated, as well as in the irradiated samples (groups 3 and 4; p < 0.001). The remineralization with Fluoridgel resulted in the greatest increase in microhardness. It is concluded that demineralization can be hampered by regular fluoride application in irradiated dentin. However, due to the considerable irradiation effect, this benefit might be negligible.     

局部运用氟制剂抑制牙本质脱矿的体外研究

目的本实验评估体外脱矿环境中几种氟制剂对牙本质的脱钙作用。方法20个标本随机分成5组:0.1%氟保护漆组,0.5%氟保护漆组,0.6%氟化泡沫组,1.23%氟化泡沫组,空白对照组。用钙体外临床诊断试剂盒检测龋蚀液中Ca2 浓度值,计算出每组在各时间点牙本质钙溶出的总量。并将标本制成磨片,在体视显微镜下观察龋损情况。结果氟制剂组抑制钙溶出效果明显优于空白对照组,氟保护漆组优于氟化泡沫组,氟保护漆组之间无显著性差异,氟化泡沫组之间无显著性差异。结论各种氟制剂均有防止牙本质脱钙作用,0.1%氟保护漆抑制牙本质脱钙作用最显著。     

The influence of dentin adhesives on the demineralization of irradiated and non-irradiated human root dentin

This study determined the caries-protective effects of two different dentin bonding systems (Syntac, Scotchbond) on sound and irradiated root surfaces in vitro. The root surfaces of 30 freshly extracted caries-free human molars were used. The teeth were bisected in the mesio-distal direction and all lingual halves of the teeth were irradiated. The irradiation dose of 60 Gy was fractionally applied over six weeks (2 Gy/day, 5d/wk). All halves were then coated with acid-resistant nail varnish, exposing two rectangular windows 6 mm2 each on the dentinal root surface. One window served as an untreated control, while the other was treated with one of the above mentioned dentin adhesive systems. The specimens were randomly distributed among the four experimental groups as follow: Group A: Syntac, non-irradiated; Group AR: Syntac, irradiated; Group B: Scotchbond, non-irradiated; Group BR: Scotchbond, irradiated. Subsequently, all specimens were demineralized for 14 days with acidified gel (HEC, pH 4.8, 37 degrees C). From each window, two dentinal slabs were cut. The slabs were ground to a thickness of 80 microm and submerged in water. The depth of the lesions was determined using a polarized light microscope. The non-irradiated control specimens showed lesions with an average depth of 63 microm (+/-10,2 microm). In the case of the irradiated control specimen, the lesion depth was not significantly different. In all experimental groups, the lesion depth was significantly reduced compared to the control groups. Statistical analysis revealed no significant differences between the irradiated and non-irradiated specimens. It can be concluded that demineralization of the root surface can be hampered by application of the dentin adhesive systems tested. In this study, no differences between irradiated and sound root surfaces could be detected.     

In situ induced demineralization in irradiated and non-irradiated human dentin

The objective of this study was to evaluate the onset of initial demineralization in irradiated and non-irradiated human dentin. Dentin specimens were prepared from the cervical regions of 48 third molars. Either the lingual or the buccal dentin specimen of each tooth was irradiated fractionally up to 60 Gy (2 Gy/d, 5 d/wk). The remaining dentin sample was not irradiated. Two irradiated and two non-irradiated dentin specimens were inserted into both buccal aspects of each 12 intraoral mandibular appliances. The appliances were worn by 12 persons for 5 wk day and night. One side was brushed daily with a fluoride-free toothpaste. On the other side, plaque was allowed to grow. Individual oral hygiene techniques were performed without any fluorides. During meals, the appliance was stored in 10% sucrose solution. After the in situ period, slabs (150 microm) were ground and studied by means of transversal microradiography and microscopic techniques. Concerning mineral loss and lesion depth, ANOVA revealed significant differences between brushed and non-brushed specimens, whereas no differences between irradiated and non-irradiated dentin lesions were found. It is concluded that (in vitro) irradiated dentine is not more susceptible to caries than non-irradiated, if adequate oral hygiene techniques are implemented.     

The influence of human plasma used for in vitro dentin perfusion on microtensile bond strength of 5 self-conditioning dentin adhesives.

OBJECTIVE: The aim of this in vitro study was to evaluate the effect of human plasma, compared to physiologic saline, on microtensile bond strengths of 5 self-conditioning dentin adhesives when used as a dentin perfusion medium. METHOD AND MATERIALS: One hundred and fifty extracted human third molars were prepared in a special manner allowing the simulation of intrapulpal pressure and dentin perfusion. The specimens were randomly divided into 10 experimental groups. Five groups were perfused with physiologic saline, while the others were perfused with diluted human plasma, each under constant hydrostatic pressure of 30 cm H2O. One saline group and 1 human plasma group was then assigned to each of the following dentin adhesives: Clearfil SE Bond (Kuraray), Clearfil Protect Bond (Kuraray), Xeno 3 (Dentsply), Futurabond NR (Voco), and iBond (Heraeus Kulzer). The microtensile bond strength for each group was evaluated using a Zwick universal testing machine 10 minutes after light curing. RESULTS: Pairwise comparison showed a significant increase of bond strength in all human plasma-perfused subgroups (P < .05, Tukey's test). The influence of the different dentin adhesives was significant (P < .001, analysis of variance). The highest significant values were observed for Futurabond NR and iBond with human plasma (P < .05, closed test procedure). CONCLUSION: The use of human plasma might be a suitable alternative to imitate perfused dentin conditions in testing devices and might eliminate the discrepancy between different in vitro investigations focusing on bond strength of dentin adhesives.     

Effect of low-fluoride toothpastes combined with hexametaphosphate on in vitro enamel demineralization

Objectives

The aim of this study was to evaluate the anticaries effect of low-fluoride toothpastes combined with hexametaphosphate (HMP) on enamel demineralization.

Methods

Bovine enamel blocks were subjected to pH cycling and treatment with toothpaste's slurries (15 groups; 2×/day). Toothpaste mixtures contained the following: no fluoride (F) plus HMP (from 0 to 3.0%); 250 ppm F plus HMP (from 0 to 3.0%); 500 ppm F; 1100 ppm F; and a commercial toothpaste (1100 ppm F). After pH cycling, surface and cross-sectional hardness, as well as F present in the enamel were determined. The demineralization depth was analyzed using polarized light microscopy. The variables were subjected to 1-way ANOVA, followed by Student–Newman–Keuls’ test (p < 0.05).

Results

In the absence of fluoride, 0.5% HMP promoted the lowest mineral loss and its effect was similar to that of a 250 ppm F toothpaste (p > 0.05). The combination of 0.5% HMP and 250 ppm F resulted in lower mineral loss (p < 0.05) and similar lesion depth when compared to the 1100 ppm F toothpaste (p > 0.05).

Conclusion

To conclude, the combination of 0.5% HMP and 250 ppm fluoride in a toothpaste has a similar inhibitory effect on enamel demineralization in vitro when compared to a toothpaste containing 1100 ppm F.

Clinical significance

The anticaries effect of toothpaste containing 250 ppm F combined with 0.5% HMP was similar to that of a 1100 ppm F toothpaste, despite the 4-fold difference in F concentration. Although such effects still need to be demonstrated in clinical studies, it may be a viable alternative for preschool children.     

The effect of different desensitizing agents on initial demineralization of human root dentin.

OBJECTIVES: The aim of this study was to determine the caries-protective effect of 3 different desensitizing agents (Seal & Protect 2.0, D/Sense 2, and Gluma Desensitizer) on root dentin in vitro. METHOD AND MATERIALS: The root surfaces of 60 freshly extracted, caries-free human molars were used. After removing the cementum, the teeth were coated with an acid-resistant nail varnish, exposing 2 rectangular windows of 2 X 3 mm each on the root surface. One window served as an untreated control, and the other window was treated with 1 of the desensitizing agents. The specimens were randomly distributed among the following experimental groups: group A, D/Sense 2; group B, Seal & Protect 2.0; and group C, Gluma Desensitizer. Subsequently, all specimens were demineralized for 14 days with acidified gel (HEC, pH 4.8, 37 degrees C). Two dentinal slabs were cut from each window. The slabs were ground to a thickness of 80 microm and immersed in water. The demineralization depth was determined using a polarized light microscope. RESULTS: The nontreated control specimens showed lesions with a mean depth of 84.9 microm (+/- 6.0). In the specimens treated with the desensitizing agents, lesion depth was generally significantly reduced. Statistical analysis revealed significantly lower values for the specimens in group B in comparison with the others. CONCLUSION: Within the limitations of an in vitro investigation, it can be concluded that the demineralization of the root surface can be hampered by applying the desensitizing agents tested.     

Effect of iron on enamel demineralization and remineralization in vitro

ObjectiveTo evaluate the effect of ferrous sulphate on enamel demineralization and remineralization, using pH-cycling models.DesignFifty blocks were selected by their initial surface hardness and subjected to a pH-cycling demineralization process. Artificially demineralized lesions were produced in 60 blocks; out of these blocks, the surface hardness of 50 blocks and the cross-sectional hardness of 10 blocks were determined. The 50 blocks were then subjected to a remineralization pH-cycling process. Treatments were carried out using ferrous sulphate solutions of different concentrations (0.333, 0.840, 18.0, and 70.0 μg Fe/mL) and a control group (deionized water). The final surface hardness (SH₂) was determined, and the integrated subsurface hardness (ΔKHN) was calculated. The enamel blocks were analysed for fluoride, calcium, phosphorus, and iron. The obtained data were distributed heterogeneously and were analysed using the Kruskal–Wallis test (p < 0.05).ResultsIn demineralization pH cycling, the group treated with the 18.0 μg Fe/mL solution had higher secondary surface hardness and lower integrated subsurface hardness (ΔKHN) than the other groups. In remineralization pH cycling, the control group showed the lowest value of ΔKHN. A decline in Ca and P concentration was observed when the Fe concentration increased (p < 0.05). There was no significant difference in the F concentration (p > 0.05) and an increase in Fe concentration (p < 0.05) in the enamel was observed when the Fe concentration increased in both the demineralization and remineralization experiments.ConclusionThe results suggest that iron reduces demineralization but does not allow remineralization to occur.     

Tissue interactions with dentin specimens after demineralization using tetracycline

Greater cell attachment to demineralized dentin has been associated with subsequent development of a fiber attachment system. The purpose of this study was to evaluate tissue interactions to dentin demineralized with different concentrations of tetracycline solution. Dentin specimens were obtained from beneath root surfaces covered by periodontal ligament. Each rectangular specimen had a face of root surface dentin and an opposite surface of pulpal dentin. Experimental specimens were treated with a tetracycline solution of either 200 mg/cc or 100 mg/cc for five minutes. The remaining group of specimens served as untreated controls. Specimens were implanted transcutaneously into incisional wounds on the dorsal surface of rats with one end protruding through the skin. Four specimens in each group were available for examination one and ten days after implantation. Histologic and histometric analysis of both root and pulpal surface of implants included counts of adhering cells, assessment of implant length within the connective tissue, and evaluation of connective tissue fiber relationships. In each group, specimens became severely extruded between days one and ten, the number of attached cells decreased, and a fiber attachment system did not develop. Tetracycline-treated surfaces had greater numbers of attached cells at both time points compared to untreated controls. No differences were discernible relating to different tetracycline concentrations. It was concluded that tetracycline-demineralized dentin provided a substrate that increased cell attachment; however, this enhanced response did not result in a connective tissue attachment.     

Inhibition of bovine dentin demineralization by a glutardialdehyde pretreatment: an in vitro caries study

Intact bovine dentin specimens were demineralized in 25 mmol acetic acid buffers (pH 5), with and without a 5-min pretreatment with an acidic 2% glutardialdehyde (GDA) solution. The results demonstrate that GDA inhibits dentin demineralization and that the inhibition depends strongly on the initial calcium and phosphate concentration in the demineralization solution. The observed inhibition increases from about 5% without calcium and phosphate to 38% with a calcium and phosphate concentration initially of 6.4 mmol and 4.1 mmol, respectively. The inhibition can be explained either by a reduction of calcium and phosphate diffusion out of the lesion or by the retention of mineral inhibitors in the dentin.