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PubMed2006

Reduced antigenicity of type I collagen and proteoglycans in sclerotic dentin.

Antigenic alterations to the dentin organic matrix may be detected by an immunohistochemical approach. We hypothesized that alterations in the antigenicity of type I collagen and proteoglycans occur in sclerotic dentin under caries lesions. Transverse sections were prepared from carious teeth in the sclerotic zone and normal hard dentin. A double-immunolabeling technique was performed on these sections, with anti-type I collagen and anti-chondroitin 4/6 sulfate monoclonal primary antibodies. We used gold-conjugated secondary antibodies to visualize the distribution of intact collagen fibrils and proteoglycans by high-resolution SEM. For sclerotic dentin, labeling densities were 19.57 +/- 3.01/microm2 for collagen and 9.84 +/- 2.62/microm2 for proteoglycans. For normal hard dentin, values were 35.20 +/- 2.73/microm2 and 17.03 +/- 1.98/microm2, respectively. Distribution of intact collagen fibrils and proteoglycans in sclerotic dentin was significantly lower than in normal hard dentin. Reductions in antigenicity from the organic matrix of sclerotic dentin under caries lesions raise concern about the potential of intrafibrillar remineralization.

Collagen Type I↗

PubMed1993

The ultrastructure of copper amalgam-covered dentin from human deciduous teeth.

The structure of dentin subjacent to Cu-amalgam restorations was studied. The restorations had been inserted 7-8 years before extraction of the teeth. No lining had been applied. The dentin subjacent to the restorations had a greenish-grayish discoloration, and in the pulpal end irregular secondary dentin had formed. Energy-dispersive X-ray microanalysis of areas showing discoloration confirmed the presence of Cu. Semithin and ultrathin undemineralized sections were studied. Vital pulp tissue and irregular secondary dentin were observed. Close to the predentin and halfway into the dentin most of the dentinal tubules were occluded. In the control material only an occasional occluded tubule was seen. Close to the Cu-amalgam restoration some tubules were occluded or partly occluded, and some were open. The odontoblasts had responded to the irritating agent by obturation of the tubules, thus reducing the permeability of the dentin. Furthermore, irregular secondary dentin had formed in another attempt to wall off the irritating agent.

Child↗

PubMed2004

Determination of elastic modulus of the components at dentin-resin interface using the ultrasonic device.

The purpose of this study was to determine the elastic moduli of the components at resin-dentin interface with the use of an ultrasonic device. Dentin plates were obtained from freshly extracted bovine incisors with a shape in rectangular form. Resin composites and bonding agents were polymerized and trimmed in the same shape as the dentin specimens. The ultrasonic equipment employed in this study was comprised of a Pulser-Receiver, transducers, and an oscilloscope. Each elastic modulus was determined by measuring the longitudinal and shear wave sound velocities. The mean elastic modulus of mineralized dentin was 17.4 GPa, while that of demineralized dentin was 1.4 GPa. When the demineralized dentin was immersed in bonding agents, the elastic modulus changed to 3.7-4.7 GPa, and these values were significantly higher than those of demineralized dentin. A gradient in elastic modulus was detected as the analysis shifted from the dentin side to the resin composite.

Analysis of Variance↗

PubMed2001

Pulp-dentin biology in restorative dentistry. Part 4: Dental caries--characteristics of lesions and pulpal reactions.

The infectious disease dental caries results in lesions that may affect enamel, dentin, pulp, and cementum. If a caries lesion has progressed to the stage at which it requires restorative intervention, it is important that the clinician understand the tissue changes in the dentin that are likely to have taken place during lesion development. Until the present, no major distinction between the restorative treatment of active (rapidly progressing) and arrested (slowly progressing) lesions has been made, despite the fact that the two conditions exhibit major differences in tissue changes in the pulp-dentin complex. Intratubular changes and tertiary dentin formation will affect the outcome of the restorative treatment. In unaffected dentin and in rapidly progressing lesions, permeable tubules persist, and when the preparation of carious teeth results in the opening of unaffected dentin, greater care must be taken in all phases of the restorative procedures than if the dentin is impermeable. An active, deep lesion can be changed to an arrested lesion by a two-step excavation approach. Optimal assessment of the prevailing clinical conditions can only be made on the basis of thorough knowledge of the biology of the pulp-dentin organ.

Dental Caries↗

PubMed2003

Sealing ability of dentin coating using adhesive resin systems.

PURPOSE: To assess the sealing ability of dentin coating using adhesive resin systems to verify its potential in protecting the dentin/pulp from the oral environmental stimuli. MATERIALS AND METHODS: 15 extracted human premolars were prepared for complete crowns and the electrical resistance of their coronal dentin was measured. The prepared teeth were then randomly divided into three groups, and the prepared dentin surface of five teeth in each group was coated using one of three adhesive resin systems (All-Bond 2, Clearfil Liner Bond II, Super-Bond D-Liner) with low viscosity resins. Measurements for electrical resistance of the prepared coronal dentin was repeated after the first and second coat of the low viscosity resins, and at 1 and 4 weeks of storage in a physiological saline solution. Additionally, three prepared teeth were exposed to either cold (37 degrees C --> 4 degrees C) or heat (37 degrees C --> 60 degrees C) stimulus and the temperature change was monitored inside the pulp chamber. Time-temperature curve was obtained before and after the first and the second dentin coating. RESULTS: Before dentin coating electrical resistance of the coronal dentin ranged from 1 to 11 k(omega), and increased significantly after the first coating by 3-15 times, and by 5-185 times after the second coating. Thermal diffusion was significantly smaller in the dentin after the coating. Before coating, the temperature change inside the pulp chamber ranged from 2-5 degrees C at 5 seconds after the thermal stimuli were applied. This decreased significantly to between 0.3-0.5 degrees C after the coating.

Analysis of Variance↗

PubMed1993

Permeability of dentin to adhesive agents.

The permeability of dentin to adhesive agents is of crucial importance in obtaining good dentinal bonding. In those systems that remove the smear layer, the opportunity exists for resin to infiltrate both tubules and intertubular dentin. Resin penetration into tubules can effectively seal the tubules and can contribute to bond strength if the resin bonds to the tubule wall. Resin infiltration into intertubular dentin can only occur if the mineral phase of dentin is removed by acidic conditioners or chelators. This is more easily accomplished in fractured dentin than in smear layer-covered dentin because of the residual collagen debris that remains on the surface following acid etching of smear layers. The channels for resin infiltration are the perifibrillar spaces created around the collagen fibers of dentin following removal of apatite mineral by acids. The diffusion of adhesive resins through these narrow, tortuous, long channels in 1 to 2 minutes offers a number of challenges that require further research.

Acid Etching, Dental↗

PubMed1993

Effects of dentin age and bonding on microgap formation.

This study compared the effectiveness of dentin adhesives in extracted molars from younger (16-26) and older (58-87) human subjects. Extracted molars were selected to be restored with one of two dentin bonding agents (n = 22 per group). Opposite sides of each molar were ground flat and a 3 mm x 3 mm cylindrical preparation was milled into each surface. The opposing surfaces of each molar were then randomly restored with either a dentin bonding system that adhered to the dentin smear layer or one which bonded to the dentin after the smear layer was removed. All samples were examined at x150 to determine both the maximum gap in micrometers and extent of the gap in degrees. There were significantly shorter (P < 0.05) microgaps in older dentin with a bonding system that removed smear layer. This bonding system also produced shorter gaps in older dentin than in younger dentin. However, there was no statistically significant difference in the percentage of gap-free margins between age groups.

Adolescent↗

PubMedDate not supplied

Dentinal adhesive with composite restorations: a clinical and microstructural evaluation.

It is generally accepted that the application of dentin-enamel adhesive should involve not only the etched enamel but also the dentinal surface. For this purpose, new bonding agents requiring dentin etching and the combined use of bifunctional groups (Primers) as well as hydrophilic resins have been introduced. This study used scanning electron microscopy to analyze the relationship between dentin and fluid resin of three bonding agents. The results demonstrated that the adhesive monomers easily penetrated the etched dentin, sealing the dentinal tubules and creating a resin dentin interdiffusion zone (hybrid layer). As a result, the microleakage between dentin and resin composite restorations, responsible for postoperative tooth sensitivity, pulpal inflammatory reaction, and secondary decay, is greatly reduced.

Acid Etching, Dental↗

PubMedDate not supplied

Resin-infiltrated dentin layer formation of new bonding systems.

The purpose of this study was to evaluate the resin-dentin interfacial morphology and shear bond strength of several new and experimental dentin bonding systems classified as single-bottle/total etch, multi-step/total etch, and self-etching. Class 1 and 5 cavities were prepared from freshly extracted permanent molars and restored with composite resin. Each bonded sample was cross sectioned and one-half was completely demineralized and deproteinized, while the other half was polished along the cut surface to permit measurement of the thickness of resin-infiltrated dentin layer (RIDL) within intertubular dentin (iRIDL) and around the peritubular walls (pRIDL) of resin tags by SEM. Shear bond strength was measured for all the systems 2 minutes after photocuring. SEM showed iRIDL and resin tags of different morphology depending on material and dentin location. The iRIDL was thinner in superficial dentin and thicker in deep dentin. Peritubular RIDL (pRIDL) was thinner than intertubular RIDL. Bond strength measurements varied from 12 to 21 MPa, depending on the materials used. Self-etching primer systems exhibited the highest bond strength, although one of the one-step/total etch systems also yielded very high values. The contribution of pRIDL to adhesion onto superficial dentin is limited by the small number of tubules. Single-component bonding agents produced SEM morphology and bond strengths similar to those of multi-step systems. Self-etching systems, despite their limited RIDL thickness, produced the highest immediate bond strengths. Bond strength did not correlate well with the thickness and morphology of RIDL.

Adult↗

PubMed2001

Local mechanical and optical properties of normal and transparent root dentin.

The mechanical and optical properties of healthy and transparent root dentin are compared using atomic force microscopy (AFM), micro-Raman and emission spectroscopies and fluorescence microscopy. The elastic modulus and hardness of intertubular and peritubular transparent and healthy dentin did not differ appreciably. The tubule filling material in the transparent zone, however, exhibited values between peritubular and intertubular dentin. Raman spectroscopy revealed a shift in the 1066 cm(-1) band to 1072 cm(-1) from normal to transparent intertubular dentin. The material filling the tubule lumen in transparent dentin showed an increase in frequency of the band near 1070 cm(-1) as well. The emission spectral characteristics under 351 nm photoexcitation indicate differences between normal and transparent intertubular dentin. A transition region of about 300 microm between normal and transparent dentin was identified. In this region the intertubular emission properties were the same as for normal dentin, but tubules were filled. The filling material had emission characteristics closer to the normal intertubular than to transparent intertubular dentin.

Journal Article↗

PubMed2003

Age-related changes in cyclic voltammetry and potentiodynamic studies of normal human dentine.

Impedance spectroscopy is one of the non-destructive techniques used by researchers to measure electrical resistance of biological tissues and ceramics. The purpose of this study is to investigate the voltage-current (V-I) characteristics of sound human dentine from young and old teeth, using cyclic voltammetry and potentiodynamic techniques. Dentine samples were prepared from freshly extracted sound third molars. After electrical measurements, dentine samples were characterized using scanning electron microscopy (SEM). Cyclic voltammetric measurements showed that variation of current through sample as a function of applied voltage is linear for dry samples of both age groups. However, for wet samples V-I characteristic were found to be different. The resistivity of dry young dentine is greater than that of old dentine in dry environment, whereas, it was found to be opposite for wet dentine samples. Using the same voltage sweep in potentiodynamic measurements dry samples display similar traces to controls suggesting that the dry dentine acts as an insulator. The number of dentinal tubules and their diameter has been found to decrease with increasing age. We propose that these changes determine the changes in electrical characteristics of sound human dentine. In spite of increasing use of electrical techniques to understand electrical properties of teeth, it is clear from this study that local structural variations and environment have a marked influence. Therefore, this baseline data needs to be considered in any future study or clinical application.

Journal Article↗

PubMed1985

Production and characterization of antibodies against murine dentine phosphoprotein.

Experiments were designed to produce and characterize a polyclonal antibody directed against mouse dentine phosphoprotein, the major non-collagenous protein of the dentine extracellular matrix. Dental extracellular matrix proteins from 2-day-postnatal Swiss-Webster-mouse tooth organs were extracted with 0.5 M-acetic acid, followed by 4 M-guanidinium chloride/0.5 M-EDTA. Mouse dentine phosphoprotein yields were further increased by precipitation with 1 M-CaCl2. Final purification was achieved by excising and eluting dentine phosphoprotein polypeptide bands from preparative sodium dodecyl sulphate/urea/polyacrylamide gels. Mouse dentine phosphoprotein is a single component of approx. 72 kDa and has a characteristic amino acid composition of 33% aspartic acid and 55% serine/phosphoserine. A polyclonal antibody was raised in rabbits against purified mouse dentine phosphoprotein and was shown to be monospecific by enzyme-linked immunoabsorbent, dot-immunobinding and 'Western transfer' assays. This antibody was used to detect the expression and localization of dentine phosphoprotein in 1-day-postnatal mouse tooth organs. This antigen was localized intracellularly within the monolayer of odontoblasts, which line the perimeter of the dental papilla mesenchyme, and within the odontoblastic cell processes, which traverse the predentine matrix. Newly forming mineralized dentine matrix was also cross-reactive with the dentine phosphoprotein specific antibody. The non-mineralized predentine matrix did not contain any detectable cross-reactive antigens.

Amino Acids↗

PubMed2006

Dentin sialophosphoprotein is processed by MMP-2 and MMP-20 in vitro and in vivo.

Dentin sialophosphoprotein (DSPP) is a major secretory product of odontoblasts and is critical for proper tooth dentin formation. During dentinogenesis, DSPP is proteolytically cleaved into smaller subunits. These cleavages are proposed activation steps, and failure to make these cleavages is a potential cause of developmental tooth defects. We tested the hypothesis that dentin-resident matrix metalloproteinases catalyze the cleavages that process DSPP. We defined the exact DSPP cleavages that are catalyzed by proteases during crown formation by isolating DSPP-derived proteins from developing porcine molars and characterizing their N-terminal sequences and apparent size on SDS-PAGE and Western blots. The in vivo DSPP cleavage sites were on the N-terminal sides of Thr(200), Ser(330), Val(353), Leu(360), Ile(362), Ser(377), Ser(408), and Asp(458). The initial DSPP cleavage is between dentin glycoprotein (DGP) and dentin phosphoprotein (DPP), generating dentin sialoprotein (DSP)/DGP and DPP. Gelatin and casein zymograms identified MMP-2, MMP-20, and KLK4 in the dentin extracts. MMP-2 and MMP-20 were purified from over 150 g of porcine dentin powder and incubated with DSP-DGP and DPP. These enzymes show no activity in further cleaving DPP. MMP-20 cleaves DSP-DGP to generate DSP and DGP. MMP-20 also cleaves DSP at multiple sites, releasing N-terminal DSP cleavage products ranging in size from 25 to 38 kDa. MMP-2 makes multiple cleavages near the DSP C terminus, releasing larger forms of DGP, or "extended DGPs." Exact correspondence between DSPP cleavage sites that occur in vivo and those generated in vitro demonstrates that MMP-2 and MMP-20 process DSPP into smaller subunits in the dentin matrix during odontogenesis.

Amino Acid Sequence↗

PubMedDate not supplied

Evaluation of the microtensile bond strength of composite resin restoration in dentin prepared with different sizes of aluminum oxide particles, using the air abrasion system.

AIM: The purpose of this in vitro study was to evaluate the influence of the abrasive technique on the microtensile bond strength of composite resin restorations. In addition, any differences in the microtensile bond strength were observed when different aluminum oxide particle sizes were used. METHODS: Flat coronal dentin surfaces were randomly distributed into 3 groups, according to surface treatment: Group A27 Air-abraded dentin with 27 microm aluminum oxide particles; Group A50-Air-abraded dentin with 50 microm aluminum oxide particles; Group HS cut dentin with a #1013 diamond bur in high-speed rotary instrument. After the bonding procedure (Single Bond/Z100), the teeth were stored in distilled water at 37 masculineC for 48 h prior to sectioning. Then, each bonded tooth was longitudinally sectioned producing sticks with a cross-sectional area of 0.81 mm2. The tensile load was applied at a crosshead speed of 0.5 mm/min, until the stick fractured. The data were analyzed by one-way ANOVA and post hoc multiple comparisons using Tukey's test. RESULTS: No difference was observed in composite bond strength when 27 and 50 microm aluminum oxide particles were used for dentin surface preparation using an air abrasion system. However, air-abraded dentin, using 27 microm aluminum oxide particles, demonstrated a higher bond strength when compared to dentin prepared by the conventional method (bur in high-speed). CONCLUSIONS: The air-abraded dentin, using 27 microm alumina powder, demonstrated higher composite bond strength when compared to bur-cut dentin, raising the possibility that this method may increase restoration longevity.

Acrylic Resins↗

PubMed1996

The effects of pH on N-methacryloyl glycine primer on bond strength to acid-etched dentin.

To develop a more effective adhesive primer, it is imperative to understand the adhesion mechanisms of the resin to the demineralized dentin through a dentin primer. When the bonding agent was directly applied to the dentin etched by 40 wt % phosphoric acid without a primer pretreatment, the bond strength of the resin to the dentin was 5 MPa. Conversely, when the demineralized dentin was pretreated with the N-methacryloyl glycine (NM alpha A) primer solution with a pH value of 1.5, the bond strength increased considerably to 15 MPa. However, the bond strength dropped dramatically from 15 to 3 MPa when the sodium salt of NM alpha A was added, thereby increasing the pH value of the NM alpha A primer solution from 3.2 to 5.0. When the pH value was increased above 3.5 (pKa value), the number of ionized NM alpha A species increased in the solution. As a result, the bond strength of the resin fell to approximately 3 MPa. This result was obtained despite the 5-micron-thick hybrid layer that was created in the subsurface of the intertubular dentin. The number of unionized NM alpha A species increased by lowering the pH value below 3.5. As a result, the NM alpha A primer provided a higher bond strength of the resin to the demineralized dentin. In contrast, when 10 wt % citric acid containing 3 wt % ferric chloride was applied to the dentin, maximum bond strength was obtained when the pH value of the NM alpha A primer solution was 3.5. The pH dependency of the bond strength obtained following 10 wt % citric acid containing 3 wt % ferric chloride etching is different from the results obtained from 40 wt % phosphoric acid etching. This can be attributed to the difference in the characteristics of the demineralized collageous layer.

Acid Etching, Dental↗

PubMed2005

Improvement of the bond strength of 4-META/MMA-TBB resin to collagen-depleted dentin.

It has been reported that the tensile bond strength between the 4-META/MMA-TBB resin and dentin pretreated with 10% citric/3% ferric chloride solution decreased after immersion in water for 2 years. The current study investigated the effect of an experimental dentin conditioner on the bonding of 4-META/MMA-TBB resin to dentin after thermocycling. The experimental conditioner was an aqueous solution of 10% ascorbic acid and 5% ferric chloride (Exp). Human teeth were prepared to expose flat dentin surfaces. These were treated sequentially with 40% phosphoric acid, 10% sodium hypochlorite, and the experimental conditioner. A commercially available dentin conditioner, an aqueous solution of 10% citric/3% ferric chloride (10-3) was used for a control group. Stainless steel rods were bonded to the pretreated dentin surfaces with the use of the 4-META/MMA-TBB resin. Tensile bond strengths were determined after 0, 5,000, 10,000, 20,000 themocycles. All data were analyzed by ANOVA, and differences among groups were analyzed by Duncan's new multiple range test (n = 10, p < 0.05). The experimental group showed no significant decrease in bond strength through 20,000 thermocycles, while the control group exhibited significant decrease after 10,000 thermocycles. Mean bond strength of the experimental groups were significantly higher than those of the control group at both 10,000 and 20,000 thermocycles. A hybrid layer could not be identified in SEM micrographs of the experimental groups. 10-3-conditioned specimen SEMs displayed crack formation between the adhesive resin and a hybrid layer. The experimental dentin pretreatment improved the bond strength of a 4-META/MMA-TBB resin to human dentin compared to 10-3 treatment after thermocycling.

Acid Etching, Dental↗

PubMed2007

Application of crosslinkers to dentin collagen enhances the ultimate tensile strength.

The stabilization of dentin collagen with biocompatible crosslinking agents may be of clinical importance to improve dentin bond strength. The present study aimed to evaluate the effect of three collagen crosslinking agents on the ultimate tensile strength (UTS) of undemineralized and demineralized dentin. Ten freshly extracted sound molars were sectioned into 0.5 x 0.5 mm2 thick beams. The beams were either demineralized or kept undemineralized. Then, specimens were subdivided into four groups according to treatments--PBS solution (control), 5% glutaraldehyde (GD), 0.5% proanthocyanidin PBS solution (PA), and 0.625% genipin PBS solution (GE). Specimens were kept in their respective solutions for either 4 or 40 h. To assess UTS, specimens were subjected to tensile forces at a crosshead speed of 1 mm/min. Statistical analysis was performed using two-way ANOVA and Fisher's PLSD test (p < 0.05). Statistically significant increases in UTS were observed for demineralized dentin after PA and GE dentin treatment, when compared with those of the control group. Dentin treated with GD showed no statistically significant differences in UTS when compared with that the control. Undemineralized dentin revealed no significant differences as compared to that of the control, regardless of the collagen crosslinkers. The application of two naturally occurring crosslinkers, i.e., PA and GE, to dentin collagen significantly improves UTS, indicating its potential value in restorative dentistry.

Collagen↗

PubMed2006

An in vitro comparison of short and long term bond strengths of polyacid modified composite resins to primary human and bovine enamel and dentine.

AIM: This in vitro study compared the shear bond strengths and fracture patterns over 7 and 180 day periods of two PMCRs bonded to both human and bovine primary tooth enamel and dentine to determine if the bovine tooth model is a suitable substitute for the human tooth model. METHODS: Flattened enamel and dentine surfaces were produced using water irrigated #600 grit SiC paper and the teeth randomly placed in groups of N=10. Cylinders of Dyrat AP (Dentsply/DeTrey) or F2000 (3M/ESPE) were bonded to the surfaces that were either etched with 37% H(3)PO(4) (etch, E groups) or treated with their respective conditioners, primers and adhesives (no etch, NE groups). The teeth were stored in distilled water at 37(o)C and shear bond strength (SBS) tested to failure at either 7 (human and bovine) or 180 days (bovine). The modes of failure were assessed under a dissecting microscope at x30. RESULTS: In general the results showed comparable mean SBS for both human and bovine enamel with Dyract AP, E and NE and also for F2000, E. Lower enamel SBS were recorded for F2000 NE but there was no significant differences in mean SBS for bovine enamel after long term storage. For dentine, significantly larger SBS were recorded for human versus bovine teeth for all of the four bonding protocols. There were also significant species differences, the mean SBS for Dyract AP, E and F2000, E for human dentine were higher than bovine but the mean SBS for the respective NE groups showed no significant differences between species. It was concluded that 37% H(3)PO(4) has a detrimental effect on SBS for bovine dentine. Over long term storage SBS of bovine dentine bonds decreased. The modes of failure were related to SBS with varying degrees of significance. CONCLUSION: Bovine primary incisor enamel and dentine, provided the latter is not conditioned with 37% H(3)PO(4), are suitable alternative test SBS substrates for human enamel and dentine.

Analysis of Variance↗