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PubMed2003

Dentin sialophosphoprotein knockout mouse teeth display widened predentin zone and develop defective dentin mineralization similar to human dentinogenesis imperfecta type III.

Dentin sialophosphoprotein (Dspp) is mainly expressed in teeth by the odontoblasts and preameloblasts. The Dspp mRNA is translated into a single protein, Dspp, and cleaved into two peptides, dentin sialoprotein and dentin phosphoprotein, that are localized within the dentin matrix. Recently, mutations in this gene were identified in human dentinogenesis imperfecta II (Online Mendelian Inheritance in Man (OMIM) accession number 125490) and in dentin dysplasia II (OMIM accession number 125420) syndromes. Herein, we report the generation of Dspp-null mice that develop tooth defects similar to human dentinogenesis imperfecta III with enlarged pulp chambers, increased width of predentin zone, hypomineralization, and pulp exposure. Electron microscopy revealed an irregular mineralization front and a lack of calcospherites coalescence in the dentin. Interestingly, the levels of biglycan and decorin, small leucine-rich proteoglycans, were increased in the widened predentin zone and in void spaces among the calcospherites in the dentin of null teeth. These enhanced levels correlate well with the defective regions in mineralization and further indicate that these molecules may adversely affect the dentin mineralization process by interfering with coalescence of calcospherites. Overall, our results identify a crucial role for Dspp in orchestrating the events essential during dentin mineralization, including potential regulation of proteoglycan levels.

Animals↗

PubMed2001

Bacterial penetration and proliferation in root canal dentinal tubules after applying dentin adhesives in vitro.

Endodontic treatment is aimed at eliminating infection and preventing bacterial regrowth in the root canal and dentinal tubules. In the present study the ability of two dentin adhesives to prevent bacterial penetration and subsequent proliferation in dentinal tubules was evaluated. Cylindrical root specimens prepared from freshly extracted bovine teeth were used in an in vitro model of dentinal tubule infection. After removal of the smear layer the intracanal dentinal tubules of the specimens were acid-etched and treated with either Gluma or EBS. Untreated specimens served as controls. Specimens were infected with Enterococcus faecalis and incubated in Brain Heart Infusion for 21 days. Powder dentin samples obtained from within the canal lumina, using ISO 025 to 033 burs, were examined for the presence of vital bacteria by inoculating on agar plates and counting colony-forming units. A significant difference was found between the experimental groups and the untreated group. After application with Gluma specimens showed the least viable bacteria in dentinal tubules. Data suggested that dentin adhesives reduced bacterial invasion into dentin and therefore have a potential role in endodontic treatment.

Acid Etching, Dental↗

PubMed2004

An in vitro investigation of penetration depth of dentine bonding agents into carious dentine.

The aim of the present in vitro study was to determine the penetration depth of dentine bonding agents into carious dentine as a possible strategy in caries treatment of deep lesions. Forty-eight extracted carious teeth were used for the experiments and divided in four groups. In a split-tooth design, one half of each tooth was treated without caries excavation, and the second half after caries excavation. In group 1 the teeth were treated with Prime & Bond 2.0 without phosphoric acid etching, and in group 2 with phosphoric acid etching. In group 3, the teeth were treated with All-Bond 2 without phosphoric acid etching, and in group 4 with phosphoric acid etching. Bonding agents were marked with an orange dye prior to application. The composition of the bonding agents had no significant influence on penetration depths. The mean thickness of the outer, necrotic caries zone in unexcavated specimens was 117 microm (+/-126). Bonding agents penetrated significantly deeper into unexcavated carious dentine (mean 124 +/- 76 microm) compared with excavated dentine (11 +/- 14 microm) and sound dentine (3 +/- 4 microm). Acid etching significantly reduced the thickness of the outer caries zone, and the penetration depth of the bonding agents into unexcavated carious specimens by approximately 50%, and increased it into sound dentine. The results indicate that dentine bonding agents could completely penetrate the unexcavated outer carious dentine in 90% of specimens. Further studies are required to determine whether further caries activity is arrested after treatment with dentine bonding procedures.

Dental Caries↗

PubMed1989

Dentine hypersensitivity. The development and evaluation of a replica technique to study sensitive and non-sensitive cervical dentine.

Studies of extracted teeth have shown that teeth exhibiting dentine hypersensitivity have larger numbers of widened dentinal tubules at the dentine surface compared to non-sensitive teeth. Many compounds used in the treatment of dentine hypersensitivity are thought to achieve therapeutic benefit by tubule occlusion, but there has been almost no attempt to prove such action in vivo. These studies systematically determined whether the dentine surface could be evaluated non-invasively, by a scanning electron microscopic replica technique. Employing a silicone rubber impression method in vitro, the surface detail of dentine could be accurately replicated, with surface scratches, tubules and intratubular structures on the original reproduced on the replica. With attention to method, similar accuracy was achieved in vivo, particularly when tubules were open on the dentine surfaces of the original. The method would appear useful for the study of the dentine surface in cases of dentine hypersensitivity and could prove the first objective method of studying the effects of treatment agents used in the treatment of this painful condition.

Acid Etching, Dental↗

PubMed1994

Effects of dentin surface treatments on the fracture toughness and tensile bond strength of a dentin-composite adhesive interface.

It has been proposed that the fracture toughness test provides an appropriate method for assessing the fracture resistance of the dentin-composite interface. The plane-strain fracture toughness test was therefore applied to a dentin-composite interface, with use of a specific dentinal adhesive, so that the effects of various dentin surface treatments on dentin-bond integrity could be studied. Interfacial fracture toughness (KIC) values were determined following 24h and 180 days of specimen aging in distilled water at 37 degrees C. Tensile bond strength (TBS) results following 24-hour aging were also obtained for comparison with the 24-hour KIC results. In general, the fracture resistance of the dentin-composite interface was highest when the dentin surface was conditioned with acid but not air-dried, intermediate when the dentin surface was conditioned with acid and subsequently air-dried, and lowest when the dentin was not conditioned with acid. The tensile bond strength results differed from the fracture toughness results in indicating differences in surface preparation effects and the type of interfacial failure observed.

Acid Etching, Dental↗

PubMed1996

Contact angle of dentin bonding agents on the dentin surface.

Physical changes in the surface characteristics of dentin during bonding procedures were evaluated by measuring the contact angles of three standard liquids, to determine the surface free energy, and that of a commercially available dual cured dentin bonding agent dropped on the primed dentin surface. The commercial dentin bonding agent did not form a hemispherical shape on the ground dentin surface, probably because it penetrated into the smear layer due to the microcapillary effect. Not could the contact angle be measured on the dentin surfaces treated with any of four experimental primers, because the bonding agent rapidly spread over the primed dentin surface. It was concluded that the priming of the dentin surface after removing the smear layer served to increase the surface free energy and to improve the wettability of the bonding agent on the dentin.

Chemical Phenomena↗

PubMed2001

Shear strength of dentin and dentin bonded composites.

PURPOSE: The objective of this study was to compare the shear strength of dentin with the shear strength of dentin bonded composites, and to determine how variables such as composite strength and blade width used during shear testing influence shear strength values. MATERIALS AND METHODS: Dentin test samples (n = 36) were made by milling the anatomical molar crowns to a shape similar to a composite rod bonded to a flat dentin surface. Dentin bonding was accomplished by bonding composites to flat dentin surfaces (n = 72) using Scotchbond MP and Z100 (n = 36) or Silux Plus (n = 36) composites. Shear testing was conducted using a guillotine-like device with a flat blade embracing half the dentin or composite cylinders. The blade thickness was either 0.25, 0.5, 0.75, 1.0, 1.25, or 1.50 mm. Six samples per material and blade thickness were tested. In addition to the above study, the bond strength of Z100 (n = 6) and Silux (n = 6) bonded with Scotchbond MP and tested with an orthodontic edgewire loop were also tested and compared with the bond strength of the Z100 and Silux samples tested with the 0.5 thick blade. All shear testing was done at a load rate of 0.5 mm/min. The results were analyzed using ANOVA and Duncan's multiple range test. RESULTS: The shear strength values when tested with the blades were: dentin = 39.7 +/- 13.0 MPa, Z100 = 29.3 +/- 7.2 MPa, and Silux = 21.1 +/- 4.9 MPa; each group had significantly different values (p < 0.05). The blade thickness had no significant effect on strength (p = 0.471). Comparing the 0.5-mm-wide blade with the edge wire (width = 0.45 mm) revealed a significant difference (p = 0.0014) favoring the blade. Z100 performed better than Silux (p = 0.0014). CONCLUSION: The shear strength of the tested bonding agent is significantly lower than the shear strength of dentin. The shear strength depends on testing method (blade vs loop) and composite material.

Analysis of Variance↗

PubMedDate not supplied

Dentin permeability: sealing the dentin in crown preparations.

Provisional restorations of full crown preparations may permit more microleakage of bacteria and their products than the final castings do. However, most investigations of the sealing qualities of cemented castings have reported that they too permit dye leakage. One approach to the problem is to seal the dentin with dentin bonding agents at the completion of the crown preparation. This study evaluated the ability of six different dentin bonding agents to seal the dentin of crown preparations of human teeth in vitro using two independent techniques. The first technique quantitated fluid filtration across dentin before and after treatment with dentin bonding agents at one hour, one day, one week, and one month and after thermocycling. The second method measured silver nitrate penetration of the thin veneers of dentin bonding agents into the dentin. Both methods correlated well with each other. The best seals were obtained with Prisma Universal Bond 2 or Superbond powder plus liquid. The worst seals were found using Gluma and Superbond liquid only. Clearfil PhotoBond, Amalgambond, and Scotchbond 2 gave intermediate results. Although the dentin bonding agents tend to accumulate on chamfers, thereby increasing their thickness to 200-300 microns, the method looks promising as a simple way to protect the pulp from the consequences of microleakage.

Analysis of Variance↗

PubMed1992

Relation of dentin sensitivity to histological changes in dog teeth with exposed and stimulated dentin.

The effect of chronic exposure of dentin to the sensitivity of intradental nerves was studied in dogs. The dentin of canine and incisor teeth was exposed one week prior to the experiments in which 34 single fiber units dissected from the inferior alveolar nerve were recorded. In the teeth with acutely bared dentin 36 nerve fibers were tested. SEM of the chronically exposed dentin showed that practically no tubule apertures could be found since the surface was covered with bacteria and oral debris. This coating had to be removed by drilling and acid etching before any responses could be evoked. When compared to the teeth with acutely exposed dentin, the sensitivity of the fibers responding to drilling, probing, osmotic stimulation, and air blasts applied to the dentin was weakened in the chronic cases, in the sense that fewer units of those tested responded. However, cold evoked nerve activity only in some chronically exposed teeth, suggesting sensitization of the nerves. TEM revealed electron-dense substance in the dentinal tubules of the chronic teeth. Some of the material was evidently cellular remnants aspirated from the pulp and some of it, staining more faintly, could be extravasated plasma proteins. In the acute cases the tubules were emptier. Light microscopy showed histological injuries in the pulp-dentin border. It is concluded that the decrease in the responsiveness of the pulp nerve fibers in the chronic cases was due to the changes in the dentin.

Animals↗

PubMed1990

[Effect of various pretreatments for dentin bonding on dentin permeability].

Pretreatment of the dentinal surface with acidic solution is now considered to be necessary to obtain strong bonding between dentin and resin materials. Effects of various surface treatments for dentin bonding on dentinal smear removal have been reported by SEM observation. In this study, changes of dentin permeability after the surface treatments were measured using Pashley's technique. Forty-second treatments with either phosphoric acid gel, aqueous phosphoric acid, 10-3 solution or aqueous 10-20 Ca solution (10% citric acid containing 20% CaCl2) produced greater increases in dentin permeability compared with the treatments using either 10-20 Ca gel, Tenure Conditioner, Scotchprep or Gluma 2 for 40 seconds. Treatments with primers including adhesive monomers such as Scotchprep and Mirage Conditioner also increased the dentin permeability by removal of the smear layers and smear plugs. Application of a bonding agent (Clearfil Photobond) for 1 minute did not remove the smear plugs and the dentin permeability remained the same as before the treatment. The changes in dentin permeability were not predictable by SEM observation in some cases.

Acid Etching, Dental↗

PubMed1989

[Dentin after dentinal exposure in dog teeth].

The teeth of dogs in which the root dentin was incompletely formed were prepared so that dentin was exposed. Tetracycline was then injected and the teeth were studied for dentin formation after the periods of 18, 20, 48 and 76 weeks. After the dentin was exposed slightly, reparative secondary dentin was not formed in the pulp horn area; However, a considerable amount of dentin was formed at the walls of the pulp chambers and the root canals. No changes were noted in the pulp horn area in the prepared teeth in comparison with unprepared teeth. The results imply that dentinal changes in the pulp horn area caused by dentinal cutting are more closely related to the depth of dentinal preparation than to the age of the tooth and to the elapsed time after preparation.

Animals↗

PubMedDate not supplied

Dentin bonding: SEM comparison of the dentin surface in primary and permanent teeth.

The literature suggest differences between primary and permanent teeth regarding the composition and morphology of the dentin. The purpose of this study was to compare the effect of two dentin conditioners on the micromorphology of the dentin surface of primary and permanent teeth. Human extracted and noncarious molars were divided into four groups and conditioned with either 10% phosphoric acid (All-Bond 2) or 10% maleic acid (Scotchbond Multi-Purpose) for different time periods. SEM photomicrographs (1500x) were taken from the conditioned dentin and evaluated blindly by three calibrated examiners. The results indicate that the smear layer was removed more easily from primary teeth than from permanent teeth (P = 0.0001), which suggests greater reactivity to acidic dentin conditioners. We also found that the longer the time of application of dentin conditioner the more smear layer is removed (P = 0.0094). In comparing primary and permanent dentin, the results of this study indicate that less time is required for appropriate acid conditioning of primary dentin surfaces. Such a differentiated protocol for bonding to primary tooth dentin results in surface morphological characteristics similar to those found in conditioned permanent teeth.

Acid Etching, Dental↗

PubMed1997

Comparison of two dentin adhesives to primary vs. permanent bovine dentin.

The purpose of this study was to compare the shear bond strengths of two adhesive systems to the primary and permanent dentin. Labial surfaces of extracted and frozen bovine mandibular primary incisors and permanent incisors were ground with #600 grit SiC paper to expose dentin. Bisco Dental Products All Bond 2 (Group AB2) or Sunmedical Co. Superbond D Liner (Group SDL) tooth surface conditioner and adhesive were applied and bonded with resin composite. A shear bond strength (SBS) test was performed and the data were analyzed by an ANOVA (P < 0.05). After the SBS test, the test surfaces of the dentin and the resin were observed using SEM. SBS on the primary dentin were significantly higher than those on the permanent dentin, both in the nonthermal cycled groups and the thermal cycled groups with the exception of the thermal cycled group of Group SDL. In the thermal cycled group of Group SDL, there was no significant difference between SBS on the primary dentin and SBS on the permanent dentin. Bond strengths on the primary dentin were found to be significantly higher than those on the permanent dentin, when using All Bond 2 or Superbond D Liner adhesive systems.

Analysis of Variance↗

PubMed2005

The nano-hardness and elastic modulus of sound deciduous canine dentin and young premolar dentin--preliminary study.

The purpose of this study was to compare the nano-hardness and elastic modulus among deciduous and permanent dentin, buccal and lingual sides, incisal, center and cervical areas, and outer, middle and inner layers. Three premolars and three deciduous canines were bucco lingually (BL) sectioned, and three deciduous canines were mesio-distally (MD) sectioned parallel to the long axis at the center of the tooth. Hardness (H), plastic hardness (PH) and Young's modulus (Y) were measured using a nano-indentation tester. The H, PH and Y values from the deciduous canine dentin were significantly lower than those from the premolar dentin at most sites. For deciduous canine dentin, the H and PH values of the MD sectioned dentin were significantly higher than those of the BL sectioned dentin in many layers of many areas. Generally deciduous canine dentin had H, PH and Y values that decreased from outer toward the inner layers and significant differences were obtained among the layers in many areas. For MD sectioned deciduous canine and BD sectioned premolar dentin, the H, PH and Y values of the cervical area were significantly lower than those of the incisal and center areas in many layers. It is possible that optimum bonding may require different treatments for deciduous and permanent dentin and perhaps also for different intratooth locations.

Anisotropy↗

PubMed2007

Hydromechanics in dentine: role of dentinal tubules and hydrostatic pressure on mechanical stress-strain distribution.

OBJECTIVES: This investigation is to understand the role of free water in the dentinal tubules on the mechanical integrity of bulk dentine. METHODS: Three different experiments were conducted in this study. In experiment 1, three-dimensional models of dentine with gradient elastic modulus, homogenous elastic modulus, and with and without hydrostatic pressure were simulated using the finite element method. Static compressive loads of 15, 50 and 100 N were applied and the distribution of the principal stresses, von Mises stresses, and strains in loading direction were determined. In experiment 2, experimental compression testing of fully hydrated and partially dehydrated dentine (21 degrees C for 72 h) was conducted using a Universal testing machine. In experiment 3, Fourier transform infrared spectroscopic analysis of hydrated and partially dehydrated dentine was carried out. RESULTS: The finite element analysis revealed that the dentine model with simulated hydrostatic pressure displayed residual tensile stresses and strains in the inner region adjacent to the root canal. When external compressive loads were applied to the model, the residual stresses and strains counteracted the applied loads. Similarly the hydrated specimens subjected to experimental compression loads showed greater toughness when compared to the partially dehydrated specimens. The stress at fracture was significantly higher in partially dehydrated specimens (p=0.014), while the strain at fracture was significantly higher in hydrated dentine specimens (p=0.037). SIGNIFICANCE: These experiments highlighted the distinct role of free water in the dentinal tubules and hydrostatic pressure on the stress-strain distribution within the bulk dentine.

Biomechanical Phenomena↗

PubMed1997

Greater concentration of dietary sucrose decreases dentin formation and increases the area of dentinal caries in growing rats.

The effect of increasing dietary sucrose concentration on dentin formation and dentinal caries progression was studied. Weanling Wistar rats received 15, 30 or 43 g/100 g sucrose in a diet; for reference, another group was fed a nonpurified diet. At the onset, tetracycline was injected to mark the dentin formed during the experiment. After 6 wk, lower molars were sectioned sagittally; the areas and thicknesses of the dentin formation during the experiment and dentinal caries lesions were quantified separately in the first and second molars. Feeding the 43% sucrose diet resulted in a significantly lower dentin formation than in other diet groups (P < 0.05). The differences obtained from the area measurements were supported by thickness measurements. In the first molar, the 43% sucrose diet resulted in a significantly greater area of dentinal caries than in the other sucrose groups. The number and severity of caries lesions clearly increased as the concentration of sucrose in the diet increased (r = 0.5, P < 0.05 and r = 0.6, P < 0.05, respectively). This study suggests that the increase in the concentration of sucrose in the diet reduces dentin formation and increases the area of dentinal caries as well as the number and severity of caries lesions; the critical sucrose concentration appears to be between 30 and 43 g/100 g.

Analysis of Variance↗

PubMed1994

A morphometric analysis of the cross-sectional area of dentine occupied by dentinal tubules in human third molar teeth.

The number and the mean percentage tubular cross-sectional area of dentinal tubules per square millimetre were calculated in specimens of coronal dentine of 13 intact human third molar teeth from patients 18 to 28 years of age. The dentine was fractured at various known distances from the dentino-enamel junction. Near the dentino-enamel junction the number of tubules per square millimetre was 22,000 and the mean tubular cross-sectional area was 3.6%. Midway between the pulpal wall and the dentino-enamel junction the number of tubules was 37,000 mm-2 and the mean tubular cross-sectional area was 6.2%. Close to the pulp the number of dentinal tubules was 48,000 mm-2 and the mean cross sectional area of tubules was 10.2 percent. The number of tubules per square millimetre more than doubled and the area occupied by tubules increased threefold from the dentine close to the dentine-enamel junction, to that close to the pulp. These differences in tubular patterns at different depths in dentine are clinically significant in dentine permeability, the treatment of traumatized teeth, and pain transmission in dentine.

Dentin↗

PubMed2002

Anisotropy of tensile strengths of bovine dentin regarding dentinal tubule orientation and location.

The purpose of this study was to investigate the effects of the location and orientation of dentinal tubules in the tooth on tensile strengths of the dentin. Dumbbell-shaped specimens of 12 groups from various locations and dentinal tubule orientations were prepared. The tensile test was performed in distilled water at a temperature of 37 degrees C. The tensile strengths of the parallel to the orientation were significantly greater than those of the perpendicular to the orientation; the tensile strengths of the radicular dentin were significantly greater than those of the coronal dentin. Nevertheless, in the radicular dentin, the tensile strengths of the perpendicular to dentinal tubules differ with respect to tensile forces. These results suggest that tensile strength of the dentin varies according to the location and orientation of dentinal tubules in the tooth.

Analysis of Variance↗