Hardness, elasticity, and ultrastructure of bonded sound and caries-affected primary tooth dentin

Biomechanical properties of bonded dentin are important factors for resin restoration. We evaluated the hardness and elastic modulus of bonded sound and caries-affected primary tooth dentin using a one-step adhesive system, and observed the microstructure of the bonded interface. Six sound and six carious primary teeth were used. For sound teeth, flat occlusal dentin surfaces were prepared with a water-cooled high-speed diamond bur. For carious teeth, infected dentin was stained with a caries detector and removed with a water-cooled low-speed round steel bur and hand instruments. The prepared dentin was bonded with One-Up Bond F Plus (Tokuyama Dental Co., Tokyo, Japan). The resin-dentin interface and dentin beneath the interface were measured with a nano-indentation tester and observed with SEM and TEM. For both the carious and sound teeth, there was no significant difference between the hardness of the interfacial dentin and dentin 10-80 microm beneath the interface. However, the Young's modulus of the interfacial dentin was significantly lower than the dentin 40-80 microm (carious teeth) or 50-80 microm (sound teeth) beneath the interface. Both the hardness and Young's modulus of the interfacial dentin were not significantly different between the carious and sound teeth. Compared to the sound dentin, the hybrid layer on the caries-affected dentin was thicker and exhibited more complicated morphologic features. The thickness of the hybrid layers was generally less than 1 microm.     

Chemical profile of adhesive/caries-affected dentin interfaces using Raman microspectroscopy

In clinical practice, dentists must frequently bond adhesives to caries-affected dentin substrates, but the bond that characteristically forms with these substrates does not provide the durability necessary for long-term clinical function. The purpose of this study was to characterize and compare the interfacial chemistry of adhesive with caries-affected and noncarious dentin using micro-Raman spectroscopy. The results indicated that the differences in the Raman spectra between noncarious and caries-affected dentin could not be accounted for by simple decreased mineralization. Both the structure of collagen and mineral in the caries-affected dentin has been altered by the caries process. The differences in structure and composition not only interfered with acid-etching process but also subsequent resin monomer penetration. It was shown that the interface between the adhesive and caries-affected dentin was wider and more complicated than that of the adhesive and noncarious dentin. As a result of adhesive phase separation, a structurally integrated hybrid layer did not form at the interface with either caries-affected or noncarious dentin. Using chemical imaging techniques, this study provides the direct evidence of adhesive phase separation at the interface with caries-affected dentin. Although our group previously reported adhesive phase separation at the interface with noncarious dentin, the chemistry of caries-affected dentin leads to greater variability and a more highly irregular composition along the length and breadth of the interface.     

Interfacial chemistry of class II composite restoration: structure analysis

The gingival margins of class II composite restorations are particularly vulnerable to marginal leakage and secondary caries. In identifying the factors contributing to caries development, the molecular structure and differences in the structure at the proximal and gingival margins have been largely overlooked. The purpose of this study was to compare the molecular structure at the adhesive/dentin interface of the proximal and gingival walls of class II composite restorations. Class II preparations were cut in 12 unerupted third molars with a water-cooled high-speed dental handpiece. The prepared teeth were randomly selected for treatment with Single Bond (SB) + Z100 (3M). Teeth were restored, per manufacturer's directions, under humidity and temperature characteristic of the oral cavity. Restored teeth were kept in sterile Delbecco's phosphate saline for 48 h. The samples were sectioned occluso-gingivally and micro-Raman spectra were acquired at approximately 1.5-microm spatial resolution across the composite/adhesive/dentin interfaces. Samples were wet throughout spectral acquisition. Raman spectral characteristics at the proximal and gingival margins were distinctly different; the depth of demineralized dentin was 6-7 microm at proximal margin, 12-13 microm at gingival margin. SB adhesive penetrated the depth of demineralized dentin in a gradient at the proximal margin. The "single bottle" adhesive used in this study, gradually penetrated the depth of the demineralized dentin at the proximal margin but failed to infiltrate the depth at the gingival margin, leaving a thick exposed collagen layer.     

In vitro microTBS of one-bottle adhesive systems: sound versus artificially-created caries-affected dentin

This in vitro study aimed to evaluate a pH-cycling model for simulation of caries-affected dentin (CAD) surfaces, by comparing the bond strength of etch-and-rinse adhesive systems on sound and artificially-created CAD. Dentin substrates with different mineral contents and morphological patterns were created by submitting buccal bovine dentin to the following treatments: (1) immersion in artificial saliva during the experimental period (sound dentin, SD), or (2) induction to a CAD condition by means of a dynamic pH-cycling model (8 cycles, demineralization for 3 h followed by mineralization for 45 h). The bond strength of Excite or Prime and Bond NT adhesive systems was assessed using the microtensile bond strength (microTBS) test. Dentin microhardness was determined by cross-sectional Knoop evaluations. Resin-dentin morphology after the treatments was examined by scanning electron microscopy. SD produced significantly higher microTBS than CAD for both adhesives evaluated, without differences between materials. CAD exhibited lower microhardness than SD. Morphological analysis showed marked distinctions between SD and CAD bonded interfaces. Under the conditions of this study, differences in morphological pattern and dentin mineral content may help to explain resin-dentin bond strengths. The proposed pH-cycling model may be a suitable method to simulate CAD surfaces for bonding evaluations.     

Physicochemical interactions at the dentin/adhesive interface using FTIR chemical imaging

To date, much of our understanding of dentin bonding has been based on investigations performed on sound, healthy dentin. This is not the substrate generally encountered in clinical practice, rather dentists must frequently bond to caries-affected dentin. Because of the extreme complexity and variability of the caries-affected dentin substrate, conventional characterization techniques do not provide adequate information for defining those factors that impact bond formation. Using Fourier-transform infrared imaging, we characterized the inhomogeneities and compositional differences across the length and breadth of the caries-affected dentin/adhesive interface. Differences in mineral/matrix ratio, crystallinity, and collagen organization were noted in the comparison of caries-affected and healthy dentin. As compared to healthy dentin, there were striking differences in depth of demineralization, adhesive infiltration, and degree of conversion at the interface with caries-affected dentin.     

Interfacial morphology and bond strength of self-etching adhesives to primary dentin with or without acid etching

The aim of the study was to determine the interfacial morphology and bond strength of three current self-etching adhesives (SEAs) to primary dentin and to evaluate the effect of introducing an additional step of phosphoric acid etching. Three human primary molars were assigned to each adhesive group for testing microtensile bond strength (microTBS) and three for studying interface morphology. Groups were: group 1, Excite, a total-etch adhesive (control); group 2, Adhese (ASE); group 3, Adper-Prompt-L-Pop (APLP), and group 4: Xeno III (XE) SEAs; groups 5-7 received application of 37% phosphoric acid for 15 s before applying ASE, APLP, and XE, respectively. A class I cavity was performed in each molar to study the interface morphology. Two halves of each tooth were used for examination either by optical microscopy, using Masson's trichromic dye technique, or by scanning electron microscopy. For microTBS determination, composite/dentin bars (1 mm(2) section) were obtained from each tooth, and tested in tension until debonding. The microTBS was significantly lower in the APLP than in the rest of the groups. The performance of SEAs on primary dentin depends on the product. Inclusion of dentin pre-etching step did not significantly modify microTBS results. All SAEs achieved greater decalcification depth on etched versus nonetched dentin.     

Micromechanics of the dentin/adhesive interface.

Scanning acoustic microscopy (SAM) was used in the burst mode at 400 MHz, nominal lateral resolution 2.5 microm, to study the micromechanical properties of the dentin/adhesive interface. Corresponding specimens from the same tooth were investigated using mu Raman spectroscopy, light microscopy, and scanning electron microscopy.12 The elastic moduli of the components of the dentin/adhesive interface were determined by comparing the recorded acoustic impedance values to a calibration curve generated on standard materials. The standard materials, which include polypropylene, Teflon, PMMA, pyrex glass, aluminum, titanium, and stainless steel, provide the appropriate range of acoustic impedance values. The elastic moduli of the components of the dentin/adhesive interface are: partially demineralized dentin, 13 Gpa; mineralized dentin, 28 GPa; adhesive, 5.0 GPa; and unprotected protein at the interface < 2.0 GPa.     

Micro-Raman imaging analysis of monomer/mineral distribution in intertubular region of adhesive/dentin interfaces

It is generally proposed that bonding of resins to dentin results from infiltration of the adhesive monomers into the superficially demineralized dentin. However, it is still not clear how well the mineral phase of dentin is removed and how far each monomer penetrates into the thin zone of "wet" demineralized dentin. The quality and molecular structure of adhesive/dentin interfaces formed under "wet" bonding conditions are studied using 2-D Raman microspectroscopic mapping/imaging techniques. Micro-Raman imaging analysis of the adhesive/dentin interface provides a reliable and powerful means of identifying the degree and depth of dentin demineralization, adhesive monomer distribution, and flaws or defects in the pattern of adhesive penetration. The image of mineral reveals a partially demineralized layer on the top of dentin substrate. Adhesive monomers readily penetrate into dentin tubules and spread into intertubular region through open tubules. The extent of adhesive monomer penetration is higher in the intertubular regions close to tubules as compared to the middle regions between the tubules. The diffusion of resin monomers differs substantially. In a comparison with a hydrophilic monomer, the hydrophobic monomer resists diffusion into the demineralized intertubular dentin area.     

Bonding performance of different adhesive systems to deproteinized dentin: microtensile bond strength and scanning electron microscopy

Deproteinization has been shown to optimize dentin bonding, but differences in adhesive composition should be considered. The objective of this study was to evaluate the effect of dentin deproteinization on microtensile bond strength (microTBS) of four total-etch adhesive systems (Single Bond/SB, Prime & Bond NT/PB, One Coat Bond/OC, and PQ1/PQ). The ultrastructure of the resin-dentin interfaces was also examined using scanning electron microscopy. Tukey's multiple-comparison tests indicated that PB and PQ produced significantly higher microTBS (p<0.05) after dentin deproteinization (PB=61.53 MPa, PQ=58.18 MPa). This treatment provided statistically lower results for SB (39.08 MPa), but the microTBS of OC to dentin was unaffected by dentin deproteinization. The bonding performance on deproteinized dentin surfaces depended on the characteristics of each adhesive system, as well as the adhesive dentin specificity to the oxidant effect of sodium hypochlorite. Incorporation of fillers in the adhesive, a possible self-etching action, and the presence of a volatile solvent (acetone) were the main factors for a better union between the adhesive system and deproteinized substrate.     

Effect of structural change of collagen fibrils on the durability of dentin bonding

This study investigates the effect of structural changes of collagen fibrils on the bonding durability of a total etch luting resin (Super-Bond C&B) and a self-etching luting resin (Panavia F 2.0) to dentin. An atomic force microscope (AFM) was used to observe structural changes of intact dentin collagen fibrils after acidic conditionings of two bonding systems. After 90 d water storage and 15,000 thermal cycles (TC) as artificial aging, micro-tensile bond strength (microTBS) was utilized to evaluate the bonding durability of the two bonding systems to dentin. microTBS after 1 d or 90 d water storage without TC were separately measured in control groups. A cross-banding periodicity of about 67 nm along collagen fibrils was seen on demineralized intertubular dentin surfaces in AFM images. For both luting resins, thermal cycling decreased (p < 0.05) microTBS of 1 d and 90 d, compared to controls. Scanning electron microscope and transmission electron microscopic examinations revealed that the top and bottom of hybrid layer (HL) were weak links in the bonding interface over time. The results suggest that the top of HL contains disorganized collagen fibrils from the smear layer which degrade over time. AFM results indicate that the demineralized intact collagen fibrils beneath the smear layer were not denatured during acidic conditioning. However, these collagen fibrils may be structurally unstable due to poor infiltration by resin or loss of resin protection within the HL over time, reducing the long-term microTBS. This process was accelerated by thermal fatigue cycling.     

Interfacial chemistry of moisture-aged class II composite restorations

Under in vivo conditions, the adhesive/dentin bond at the gingival margin of class II composite restorations can be the first defense against substances that may penetrate and ultimately undermine the composite restoration. Deterioration of this bond during aqueous aging is an area of intense investigation, but to date, the majority of our techniques have provided only an indirect assessment of the degrading components. The purpose of this study was to analyze the in situ molecular structure of adhesive/dentin interfaces in class II composite restorations, following aging in aqueous solutions. Class II preparations were cut from 12 unerupted human third molars, with a water-cooled, high-speed, dental handpiece. The prepared teeth were randomly selected for restoration with single bond (SB) and Z100 (3M). Teeth were restored, as per the manufacturer's directions, under environmental conditions that simulated humidity and temperature characteristics of the oral cavity. Restored teeth were kept in sterile Delbecco's phosphate saline for 48 h or 90 days. The samples were sectioned occlusogingivally and micro-Raman spectra were acquired at approximately 1.5 microm spatial resolution across the composite/adhesive/dentin interfaces at the gingival margins. Samples were wet throughout spectral acquisition. The relative intensity of bands associated with the adhesive in the interfacial region decreased dramatically after aqueous storage. This decrease in concert with the similar depth of dentin demineralization provides direct spectroscopic evidence of leaching of adhesive monomer from the interface during the 90 days of storage. SB adhesive infiltrated 4-5 microm of 12-microm demineralized dentin at the gingival margin. After 90 days of aqueous storage, SB adhesive infiltration was reduced to approximately 2 microm, leaving approximately 10 microm of demineralized dentin collagen exposed at the gingival margin. The unprotected collagen at the gingival margin of the aged class II composite restorations was disorganized, suggesting hydrolysis of the collagen, with 90 days of aqueous storage.     

Ca/P mol ratio of cries-affected dentin structures

BACKGROUND: A new approach called "minimum intervention" has been introduced for restoration of carious lesions to preserve tooth structure. This approach suggests that perhaps caries need not always be removed completely from deeper portions of the cavity. It is, therefore, important to characterize caries-affected dentin structures, because of the potential changes in bonding quality when using different dentinal substrates. MATERIALS AND METHOD: Ninety teeth (30 teeth each group) were studied. The first group (CF) consisted of 30 caries-free teeth. The second group (CC) consisted of 30 teeth, for which caries-free dentin teeth was chemically demineralized. The third group (ND) consisted of 30 extracted human molars with coronal carious lesions. After all tooth samples were water-polished with grit #600 SiC paper, they were tested by surface contact angle measurements and the electron-probe microanalyzer to measure Ca/P mol ratio. RESULTS: Contact angles were CF = 60.07 degrees ; CC = 30.8 degrees; ND = 26.11 degrees , p<0.05. Ca/P mol ratios were as follows; CF = 1.549 (+/-0.0435); CC = 1.324 (+/-0.2305); ND = 1.568 (+/-0.0523), p<0.05. Weibull analyses for Ca/P mol ratio indicated shape parameter (m) of CF was 13.3; it was 12.8 for ND and 11.8 for CC. Above the delta point (=1.65 in Ca/P ratio), for both groups m = 3.4. CONCLUSION: Caries-affected dentin surfaces (naturally-developed and chemically created) were statistically more chemically active than caries-free dentin surface. Ca/P mol ratio of chemically created caries was less than other two groups.     

Micromechanical properties of demineralized dentin collagen with and without adhesive infiltration

In a previous study, we reported the upper limit of Young's modulus of the unprotected protein at the dentin/adhesive interface to be 2 GPa. In this study, to obtain a more exact value of the moduli of the components at the d/a interface, we used demineralized dentin collagen with and without adhesive infiltration. The prepared samples were analyzed using micro-Raman spectroscopy (micro RS) and scanning acoustic microscopy (SAM). Using an Olympus UH3 SAM (Olympus Co., Tokyo), measurements were recorded with a 400 MHz burst mode lens (120 degrees aperture angle; nominal lateral resolution, 2.5 microm). A series of calibration curves were prepared using the relationship between the ultrasonically measured elastic moduli of a set of known materials and their SAM response. Finally, both the bulk and bar wave elastic moduli were computed for a set of 13 materials, including polymers, ceramics, and metals. These provided the rationale for using extensional wave measurements of the elastic moduli as the basis for extrapolation of the 400 MHz SAM data to obtain Young's moduli for the samples: E = 1.76 +/- 0.00 GPa for the collagen alone; E = 1.84 +/- 0.65 GPa for the collagen infiltrated with adhesive; E = 3.4 +/- 1.00 GPa for the adhesive infiltrate.     

Water content and apparent stiffness of non-caries versus caries-affected human dentin

Caries-affected dentin contains less mineral and more water than surrounding normal dentin. Such dentin should be less stiff and should shrink more than normal dentin when dried. The purpose of this study was to test the relationships between the stiffness, shrinkage, and water content of caries-affected versus normal dentin. Extracted human carious third molars were stained with caries-detector dye and the occlusal surfaces ground down until only caries-affected dentin remained, surrounded by normal dentin. Dentin disks were prepared from these crowns placed in a aluminum well positioned under a modified thermal mechanical analyzer. Changes in specimen height and stiffness were measured following drying or static loading in both caries-affected and surrounding normal dentin. Core samples of these two types of dentin were used to gravimetrically measure water content. Two-way ANOVA and regression analysis was used to test the relationship between shrinkage versus water content, stiffness versus water content, and stiffness versus shrinkage. Caries-affected dentin was found to be less stiff and contained more water than normal dentin (p < 0.05). Regression analysis revealed highly significant inverse relationships between stiffness and water content, and stiffness and shrinkage (p < 0.0005).     

Deproteinizing effects on resin-tooth bond structures

This study investigated the effects of NaOCl on resin-tooth bonds to simulate the situations of long-term durability and caries invasion. Resin-tooth bonded specimens were produced with the use of two resin adhesives (Excite and One-Bond). Resin-tooth bonded beams (adhesive area; 0.9 mm2) were serially sectioned and the specimens were immersed in 10% NaOCl medium for 0 (control), 2, 4, and 6 h after being stored in water for 24 h. After immersion, microtensile bond tests were performed. SEM fractography was conducted to calculate each failure mode by image analysis. In addition, the adhesive interface was examined with the use of TEM. In the control specimens, enamel bond strengths had no difference between Excite (45.6 +/- 15.0) and One-Bond (56.9 +/- 12.9). On the other hand, dentin bond strengths had significant difference between Excite (80.6 +/- 21.2) and One-Bond (50.7 +/- 11.2). The bond strengths decreased with increased storage time for both systems with enamel and dentin bonds. The deteriorated mineralized dentin of beams resulted in bond-strength reduction for resin-enamel bonds. For dentin bonding, the adhesive interface was gradually dissolved from the outer to the center portion of the beam. The depletion of collagen fibrils within the demineralized dentin or hybrid layer deformation was found under SEM and TEM examinations. These morphological changes are responsible for bond strength reduction of resin-dentin bonds.     

Improved wet bonding of methyl methacrylate-tri-n-butylborane resin to dentin etched with ten percent phosphoric acid in the presence of ferric ions

The objective of this study was to determine the influence of dissolved dentinal substances in demineralized dentin on the hybridization of resin for bonding to dentin. It was hypothesized that these substances, including polyelectrolytes, significantly change the substrates, which could then be assessed by the addition of Na(+), Ca(2+), or Fe(3+) in 10% phosphoric acid. Bovine dentin specimens were etched for 10 s with a solution of 10% phosphoric acid (control) or of 22.0 mM dissolved sodium chloride (10P-Na), calcium chloride (10P-Ca), or ferric chloride (10P-Fe). The specimens were then rinsed, blot-dried, and primed three times with 5% 4-methacryloyloxyethyl trimellitate anhydride in acetone for 60 s. Methyl methacrylate-tri-n-butylborane resin was then applied. The tensile bond strength of each of the dumbbell-shaped specimens was then measured. The fractured surfaces and modified cross-sections were examined by scanning electron microscopy. The cross-sections were soaked in 6N HCl for 10 s and then in 1% sodium hypochlorite for 30 min to determine the resin content in the hybridized specimens. Shrinkage of the demineralized dentins upon drying was assessed by atomic force microscopy. The tensile bond strengths were 10.8 +/- 4.5 (control), 15.0 +/- 7.0 (10P-Na), 19.3 +/- 5.5 (10P-Ca), and 27.8 +/- 8.1 (10P-Fe) MPa. The atomic force microscopy studies showed that Fe(3+) minimized the shrinkage by drying for 10 s but Ca(2+) and Na(+) did not decrease the shrinkage the same as the control. The results support the hypothesis that the monomer permeability of wet demineralized dentin is effectively improved by dissolving ferric ions in the phosphoric acid, resulting in a greater bond strength and higher resin content in the hybridized dentin. The dissolved dentinal substances, including the polyelectrolytes, had a significant influence on the characteristics of the demineralized dentin, changing the degree of hybridization and bonding.     

第7代黏接剂与正常和龋损牙本质黏接强度的比较

背景：对于第1~6代牙本质黏接剂的黏接强度,国内外学者做了大量的研究并取得了满意的成果,但尚未见对第7代黏接剂Adper EasyTM one黏接性能的相关报道。 目的：比较3M第7代自酸蚀黏接剂对正常和龋损牙本质黏接强度的差异,并与传统全酸蚀黏接剂进行对比。 方法：取健康磨牙和牙合 面慢性龋磨牙各12颗,分为A、B(健康磨牙),C、D(牙合 面慢性龋磨牙)4组,其中A、C组用Adper EasyTM one黏接剂,B、D组用Single bond 2黏接剂。测试4组试件的微拉伸强度,观察断裂界面形态。 结果与结论：A、B组的黏接强度分别为(21.84±3.98) ,(27.10±4.85) MPa,C、D组的黏接强度分别为(16.44±3.46),(21.48±4.85) MPa,A组与B组、C组与D组、A组与C组、B组与D组之间的微拉伸强度差异均具有显著性意义(P < 0.05)。断裂多发生在树脂-牙本质黏接界面。提示无论在正常牙本质还是龋损影响牙本质,全酸蚀黏接剂的黏接强度强于第7代自酸蚀黏接剂;对于同一种黏接剂正常牙本质能获得比龋损牙本质更大的黏接强度。     

Characterization of interfacial chemistry of adhesive/dentin bond using FTIR chemical imaging with univariate and multivariate data processing

Fourier transform infrared (FTIR) chemical imaging can be used to investigate molecular chemical features of the adhesive/dentin interfaces. However, the information is not straightforward and is not easily extracted. The objective of this study was to use multivariate analysis methods, principal component analysis, and fuzzy c-means clustering and to analyze spectral data in comparison with univariate analysis. The spectral imaging data collected from both the adhesive/healthy dentin and adhesive/caries-affected dentin specimens were used and compared. The univariate statistical methods such as mapping of intensities of specific functional group do not always accurately identify functional group locations and concentrations because of more or less band overlapping in adhesive and dentin. Apart from the ease with which information can be extracted, multivariate methods highlight subtle and often important changes in the spectra that are difficult to observe using univariate methods. The results showed that the multivariate methods gave more satisfactory, interpretable results than univariate methods and were conclusive in showing that they can discriminate and classify differences between healthy dentin and caries-affected dentin within the interfacial regions. It is demonstrated that the multivariate FTIR imaging approaches can be used in the rapid characterization of heterogeneous, complex structure.     

Anodic oxide films containing Ca and P of titanium biomaterial.

Anodic oxidation and oxide films of titanium in the new electrolyte of calcium glycerophosphate (Ca-GP) and calcium acetate (CA) were investigated by galvanostatic mode, SEM, XRD and EPMA. The anodic oxide film displayed porosity, intermediate roughness, and high crystallinity. Also, the oxide film is enriched with Ca and P and high in thickness without microcracks. According to the surface properties of the oxide film, the optimum condition was that the concentration of the electrolyte was 0.02 M Ca-GP and 0.15 M CA, and current density and final voltage were 70 A/m2 and ca. 350 V. The oxide film formed in the condition is 0.98 microm (Ra) rough, 5-7 microm thick, adhesive to the underlying substrate, and near 1.67 Ca/P ratio in the oxide film.     

Morphological analysis and chemical content of natural dentin carious lesion zones

Dentin is one of the earliest bio-mineralization products to appear in the evolution of vertebrates. Dentin reactions to infection mimic earlier phylogenetic patterns, and carious lesions are divided into different zones which reflect the natural patho-morphological reaction of dentin to the carious attack. It was the aim of this study to investigate deep dentin carious lesions of human molars with combined polarization light microscopy, scanning electron microscopy and energy dispersive X-ray element analysis (EDX) for the determination of different zones of the carious lesions, their extent and the chemical content. Sixteen extracted teeth with deep dentin carious lesions were embedded in Technovit 9100 (Kulzer) and serial sections of 80 microm thickness were made. These sections were then examined with polarized light microscopy to identify the different zones of the lesions. The outlines of the zones were traced consecutively and 3D-reconstructions were made for the determination of the extent and calculation of the volumes of the different zones. From the volumes of the demineralizing dentin and the translucent zone a Dentin Demineralization Index (DDI) was calculated. Three sections of each lesion were then coated with carbon and studied with a scanning electron microscope. 3D-reconstruction of the teeth showed the rather stable translucent zone, interrupted by remnants of dead tracts, and very different volumes of demineralizing dentin. Therefore, with increasing size of the demineralizing dentin, the DDI increased. The chemical content was measured using energy dispersive X-ray analysis (EDX) in areas of intertubular dentin. The content of Ca, P, and C was significantly different in all zones. The Ca/P ratio was significantly different between sound dentin and demineralizing dentin. From the results we conclude that the mineral content of intertubular dentin of the translucent zone and demineralizing dentin is different from that of sound dentin, and the unique mineralization pattern of the translucent zone is a biological reaction to the carious attack. Because active dentin lesions exhibit many non-occluded open dentin tubules, further bacterial invasion or, in case of dentin treatment, the penetration of bonding agents towards the pulp is morphologically not prevented and therefore of clinical importance.