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PubMed1999

Effect of moist vs. dry bonding to normal vs. caries-affected dentin with Scotchbond Multi-Purpose Plus.

Recent research in dentin bonding demonstrated the superiority of moist bonding over dry bonding on normal dentin, but it is unclear if this technique is also superior in bonding to caries-affected dentin. The purpose of this study was to evaluate the SEM appearance and bond strength of Scotchbond Multi-Purpose Plus (SMPP) to normal vs. caries-affected dentin bonded under moist vs. dry conditions, with and without polyalkenoic acid in the primer. Extracted carious human third molars were ground down by means of 600-grit SiC paper until the carious dentin no longer stained with caries detector solution. The flat surfaces were then primed, bonded, and built up with resin composite. After soaking in water for 1 day, the teeth were serially sectioned vertically into 5 or 6 slabs 0.7 mm thick. The bonded caries-affected areas were isolated by means of an ultrafine diamond bur to create an hourglass configuration with a cross-sectional area of 0.9 mm2. Bonded normal dentin was isolated the same way. Each specimen was attached to a Bencor device and tested in tension to failure. SMPP bonds to dry, normal dentin were only half as strong (21+/-10 MPa, x +/- SD) as those made to moist, normal dentin (42+/-9 MPa, p<0.01). There was no significant difference between bonds made to normal vs. caries-affected dentin by means of the moist technique (42+/-9 vs. 48+/-4 MPa, respectively). Removal of the polyalkenoic acid from the primer lowered (p<0.05) the bond strength of SMPP to caries-affected dentin (38+/-8 MPa). The benefits of moist bonding extend to caries-affected dentin. The polyalkenoic acid in the SMPP primer contributes to the high bond strength that can be achieved to caries-affected dentin.

Analysis of Variance↗

PubMed1999

Ultrastructural properties of laser-irradiated and heat-treated dentin.

Previous studies using scanning electron microscopy and infrared absorption spectroscopy reported that laser irradiation causes compositional changes in enamel. The purpose of this study was to evaluate the ultrastructural and compositional changes in dentin caused by irradiation with a short-pulse laser (Q-switched Nd:YAG). The irradiated and non-irradiated areas of the lased dentin samples were investigated by scanning (SEM) and transmission electron microscopy (TEM), micro-micro electron diffraction, and electron microprobe analysis of dispersive energy (EDX). Heat-treated dentin was similarly investigated. This study demonstrated that laser irradiation resulted in the recrystallization of dentin apatite and in the formation of additional calcium phosphate phases consisting of magnesium-substituted beta-tricalcium phosphate, beta-TCMP, beta-(Ca,Mg)3(PO4)2, and tetracalcium phosphate, TetCP, Ca4(PO4)O. TEM analyses of the modified and unmodified zones of the irradiated areas showed two types of crystal populations: much larger crystals from the modified zone and crystals with size and morphology similar to those of dentin apatite in the unmodified zone. The morphology of crystals in the modified zones in the irradiated dentin resembled those of dentin sintered at 800 or 950 degrees C. In the irradiated areas (modified and unmodified zones), the Ca/P ratio was lower compared with that in the non-irradiated dentin. The Mg/Ca ratio in the modified zones was higher than that in the unmodified zones and in the non-irradiated dentin. In sintered dentin, the Mg/Ca ratio increased as a function of sintering temperature. The ultrastructural and compositional changes observed in laser-irradiated dentin may be attributed to high temperature and high pressure induced by microplasma during laser irradiation. These changes may alter the solubility of the irradiated dentin, making it less susceptible to acid dissolution or to the caries process.

Calcium↗

PubMed2002

Bonding of self-etch and total-etch adhesives to carious dentin.

Carious dentin is partially demineralized and contains mineral crystals in the tubules. This may permit the deeper etching of intertubular dentin but prevent resin tag formation during bonding. We hypothesize that resin adhesives will produce lower bond strengths to caries-infected and caries-affected dentin compared with normal dentin. We tested this by measuring the microtensile bond strength of a total-etch adhesive and an experimental self-etching adhesive (ABF) to caries-infected, caries-affected, and sound dentin and by correlating those results with ultrastructural observations. The bond strengths of both adhesives to sound dentin were significantly (p < 0.05) higher than those to caries-affected dentin, which, in turn were significantly (p < 0.05) higher than those to caries-infected dentin. For both adhesives, hybrid layers in caries-affected dentin were thicker but more porous than those in sound dentin. The lower bond strengths may be due to the lower tensile strength of caries-affected dentin. Clinically, this may not be a problem, since such lesions are normally surrounded by normal dentin or enamel.

Acid Etching, Dental↗

PubMed1998

Effect of a re-wetting agent on the performance of acetone-based dentin adhesives.

PURPOSE: To compare the in vitro bond strengths of two acetone-based one-bottle dentin adhesives applied to four surface moisture conditions. The tested hypothesis was that wetting a dried dentin surface with an aqueous HEMA solution would result in bond strengths similar or higher than those obtained by leaving the surface moist as per manufacturers' instructions. MATERIALS AND METHODS: Eighty flat dentin bonding sites were polished to 600-grit on middle dentin of the labial surface of bovine incisors mounted in acrylic resin. The specimens were equally and randomly divided between two acetone-based dentin adhesives (One-Step and Prime & Bond 2.1) and four different levels of surface moisture (moist dentin, dentin dried for 1 s, dentin dried for 5 s, and dentin dried for 5 s followed by re-wetting with Aqua-Prep, an aqueous HEMA solution). A composite post was then adapted to the treated area and light-cured. After thermocycling, the bond strengths were determined by testing the specimens in shear. Field Emission SEM examinations were carried out to evaluate the effects of different treatments on the dentin-resin interface. RESULTS: Statistical analysis revealed that the application of One-Step resulted in similar mean shear bond strengths for the groups in which moisture was present on the dentin surface (12.0-14.2 MPa). The mean shear bond strengths for the group in which One-Step was applied to a dried dentin surface was significantly lower (6.0 MPa). For Prime & Bond 2.1, the application of a re-wetting solution significantly increased mean shear bond strengths (13.9 MPa). The remaining three Prime & Bond 2.1 groups yielded statistically similar mean bond strengths, regardless of the surface condition (6.6-8.1 MPa).

Acetone↗

PubMed1992

Morphological characterization of hypersensitive human radicular dentin and the effect of a light-curing resin liner on tubular occlusion.

A dentin biopsy technique was employed to compare the morphological features of hypersensitive and non-sensitive human radicular dentin. Specimens sampled from different areas in the same root surface displaying hypersensitivity or non-sensitivity were prepared for examination in the scanning electron microscope (SEM). Before analysis some specimens were exposed to surface demineralization and digestion of collagen to allow observation of subsurface portions of the dentinal tubules. In another set of observations the potential of a light-curing resin liner to penetrate root dentin in vitro and to maintain tubular occlusion over time following treatment of hypersensitive radicular dentin were examined. Orifices of many dentinal tubules were open in hypersensitive regions while non-sensitive areas generally displayed tubules occluded with mineralized material. SEM-images of HCl-collagenase treated specimens demonstrated the frequent presence of membrane-like structures in tubules of hypersensitive dentin. In non-sensitive dentin these structures were sparse. Topical application of a light-curing resin liner to wedge shaped defects prepared in radicular dentin of extracted human teeth resulted in a surface coating with a resin thickness of 20-50 microns. Resin penetrated dentinal tubules to a depth of more than 5 microns. Dentin biopsies examined 6 months after treatment with the liner showed presence of resin-like material in a majority of the tubules in dentin where hypersensitivity was no longer perceived. In none of the specimens did the liner remain as a surface coating. In areas of recurrent hypersensitivity more than half of the tubules presented with open orifices.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Etching, Dental↗

PubMedDate not supplied

Surface pH and bond strength of a self-etching primer/adhesive system to intracoronal dentin after application of hydrogen peroxide bleach with sodium perborate.

This study compared the dentin bond strength of a self-etching primer/adhesive system with dentin surface pH with or without bleaching and observed the morphological changes in bleached dentin treated with a self-etching primer. Dentin disks were prepared from the coronal-labial region of 32 human anterior teeth. The pulpal surfaces of the dentin disks were polished with 600-grit SiC paper under running water. The dentin surfaces on all specimens were bleached with a mixture of 30% hydrogen peroxide and sodium perborate in 100% humidity at 37 degrees C for one week. The bleaching agent was then rinsed off with water for 5, 15 or 30 seconds. All specimens were stored in water at 37 degrees C. Half of the five-second rinsing specimens were stored in water for an additional week. Dentin surface pH with or without bleaching was examined using a pH-imaging microscope (SCHEM-100). A self-etching primer/adhesive system (Clearfil SE Bond) was applied to bleached or unbleached dentin according to the manufacturer's instructions. After 24-hour water storage, the bonded specimens were prepared for microtensile testing. Microtensile bond strength (microTBS) to dentin was measured using a universal-testing machine (EZ test, Shimadzu, Japan) at a crosshead speed of 1.0 mm/minute. Data were analyzed by one-way ANOVA and Scheffe's test (alpha=0.05). The pH values of the dentin surfaces of the 5 and 15 second rinsing groups were significantly higher than the control group (p<0.05), while the 30-second rinsing and one-week water storage groups had similar surface pH values to the control group (p<0.05). The microTBS of 5, 15 and 30 second rinsing specimens after bleaching were significantly lower than the control specimens (p<0.05). However, after one-week of water storage, the microTBS returned to the control group. The application of a bleaching agent increased the pH value of the dentin surface and decreased the bond strength of the self-etching primer/adhesive system. One-week water storage after bleaching recovered the surface pH and the microTBS to dentin.

Analysis of Variance↗

PubMed1995

Dentin surface treatments and glass ionomer microleakage.

PURPOSE: To investigate the effect of various dentin treatments on the microleakage of Class V restorations restored with a resin-modified glass ionomer restorative cement. MATERIALS AND METHODS: Forty extracted noncarious molar teeth received Class V preparations with the occlusal margin in enamel and the gingival margin in dentin. Preparations were restored with Fuji II LC glass ionomer restorative material. Five dentin treatments were tested prior to restoration (n = 16): Group 1: without dentin pretreatment; Group 2: with GC Dentin Conditioner (10% polyacrylic acid solution); Group 3: with ProBond Dentin Primer; Group 4: with GC Dentin Conditioner and ProBond Dentin Primer; Group 5: with ProBond Dentin Primer followed by application of ProBond adhesive. Samples were thermocycled, stained with 0.5% basic fuchsin, and sectioned to evaluate microleakage. Data was analyzed using Kruskal-Wallis and Wilcoxon Signed-Rank Tests at a significance level of P < 0.05. SEM analysis was performed on selected samples to examine the dentin/glass ionomer interface. RESULTS: There was no statistically significant difference between any of the dentin pretreatments with regard to enamel or dentin microleakage. SEM analysis indicated excellent adaptation between glass ionomer and dentin for all treatment groups.

Acid Etching, Dental↗

PubMed1996

Bond strengths to enamel and dentin with indirect and direct resin composites.

PURPOSE: To investigate the differences in shear bond strengths between indirect and direct resin composites attached to enamel and dentin. MATERIALS AND METHODS: Sixty human molar teeth stored in distilled water since extraction were used in this study. Thirty of the teeth were prepared to form a flat enamel surface ground to 600 grit and 30 of the teeth were prepared to form a flat dentin surface ground to 600 grit. Cylinders constructed from Triad indirect resin composite were bonded to 15 enamel and 15 dentin surfaces and additional cylinders constructed from TPH direct resin were bonded to the remaining 15 enamel and 15 dentin substrates. Bond strengths were determined by shearing the specimens with an Instron testing machine. RESULTS: Mean shear bond strengths observed in this study were: Triad to enamel, 27.64 +/- 7.35 MPa; TPH to enamel, 27.43 +/- 3.37 MPa; Triad to dentin, 21.83 +/- 3.10 MPa; and TPH to dentin, 21.27 +/- 4.85 MPa. Two-way ANOVA demonstrated that significant differences existed between the four test groups and that this difference was primarily related to the surface to which the cylinders were attached (P = 0.000). No significant differences were discovered in shear bond strengths between restorative materials (P = 0.767) or between restorative materials bonded to a specific, common surface (P = 0.891). Turkey's post hoc test demonstrated that the shear bond strength of Triad to enamel was significantly greater than the shear bond strength of either Triad to dentin (P = 0.012) or TPH to dentin (P = 0.005). This test also pointed out that the shear bond strength of TPH to enamel was significantly greater than the shear bond strength of either TPH to dentin (P = 0.007) or Triad to dentin (P = 0.016). Finally, it was noted that the shear bond strength of Triad to enamel was essentially the same as TPH to enamel (P = 1.000) and that the bond strength of Triad to dentin was essentially the same as TPH to dentin (P = 0.990).

Acrylic Resins↗

PubMed1996

Bond strength of composite to sound and artificial carious dentin.

PURPOSE: To determine the in vitro bond strength of a composite (Herculite XRV) to sound dentin and artificial carious lesions in dentin. MATERIALS AND METHODS: Buccal and lingual surfaces from extracted human molar teeth were ground to expose sound dentin surfaces. The buccal surface was maintained as sound dentin, while an artificial carious lesion was created in the lingual surface using an acidified gelatin gel. A bonding agent (Optibond) was applied to both buccal and lingual surfaces with and without prior etching with 37.5% phosphoric acid. The composite was applied and debonded under tension after 24 hours in water at 37 degrees C. RESULTS: Both sound dentin (23.1 MPa) and etched sound dentin (22.2 MPa) had similar bond strengths, whereas artificial carious lesions in dentin that had been etched (11.8 MPa) and non-etched dentin lesions (8.8 MPa) had significantly lower bond strengths. Adhesive failures were greatest for dentin lesions (60-95%) and least for sound dentin(40-50%). Etching with phosphoric acid did not improve the bond strength of composite to sound dentin or artificial carious lesions in dentin.

Acid Etching, Dental↗

PubMed2000

A surgical technique for administering laser irradiation to rat incisor dentin.

With the advent of lasers in the field of dentistry, various methods have been used to expose dentin to laser irradiation. This was done indirectly through the alveolar bone, as well as directly on dentin wafers and on extracted human teeth. However, dentin is a vital tissue and the only way to show the ramifications of laser irradiation is by directly exposing the dentin to this energy source under in vivo conditions. In the present study we describe a highly reproducible method for accomplishing this. Male Sprague Dawley rats were anesthetized and an incision was made at the junction of the attached palatal mucosa and the unattached buccal mucosa parallel to the maxillary bones on both sides. This procedure exposed the underlying bone where a 2 mm square window, at a point 3 mm caudal and parallel to the gingival attachment, was cut out to the depth of the periodontal ligament. The site was flushed with a 0.9% sterile sodium chloride solution and gently dried with gauze. The beam of the laser was focused in the middle of the 2 mm square window and a pre-determined energy level and pulse duration (2 W 50 ms or 10 W 50 ms) were selected. The focal length guide was held at right angles to the dentin surface and in contact with the maxilla at all times. The energy densities of either 52.6 or 263.2 J/cm(2) were delivered to the 'root' dentin by a single pulse. The survival rate was 92%. The animals that died did so while under anesthesia and not after exposure to laser irradiation. The animals that survived tolerated the surgery and the laser irradition very well, regaining (and eventually surpassing) their initial weight 3 days after the procedures were performed. The thickness of the dentin that was exposed to laser irradiation was not completely penetrated by the energy levels used. At both energy levels some dentinal tubules appeared blocked and evidence of melted dentin was apparent. However, at the higher energy level two distinct zones were observed in the funnel-shaped lesion. In the inner zone distinct dentinal tubules were not readily visible, while in the outer zone the tubules were opened and completely free of debris. This technique is highly reproducible and yields consistent results with little or no stress to the animals. Although the energy levels used did not penetrate the entire thickness of the dentin, the depth of penetration of the laser beam appears to be related to the energy level used and the thickness of the dentin layer present.

Animals↗

PubMed2005

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).

Dental Caries↗

PubMed2005

Anisotropic fracture in bovine root and coronal dentin.

OBJECTIVES: This purpose of this study was to address the fundamental question of how the fracture properties of dentin are related to its composite structure. METHODS: Strain concentration tests and impression-induced damage tests were designed to compare bovine root dentin with coronal dentin, and to understand the role of individual structural elements in the fracture of dentin. RESULTS: Absent in peritubular dentin, root dentin is insensitive to cracks and exhibits higher fracture resistance than coronal dentin that has a typical brittle fracture behavior along the peritubular dentin. Fracture analysis and impression damage experiments found that root dentin is highly anisotropic in fracture behavior. Cracking is predominantly controlled by the organization of collagen fibrils, with the incremental lines being the weakest planes. In coronal dentin, highly mineralized peritubular dentin that intersects with the incremental lines creates additional weak orientations that compete with the incremental lines and thus greatly decrease the degree of fracture anisotropy. SIGNIFICANCE: This study demonstrated that dentin is by no means homogeneous in terms of fracture properties. Location and orientation (especially in terms of incremental lines) should be taken into account when examining tooth failure both in laboratory and in clinical studies.

Animals↗

PubMed1998

Comparative observations on the spacing of short-period (von Ebner's) lines in dentine.

The spacing of short-period incremental markings in dentine was measured in longitudinal ground sections and in longitudinal demineralized silver-stained sections of permanent human canines and premolars. Measurements were made (i) within 50 microm from the granular layer of Tomes (GLT), (ii) between 100 and 200 microm from the GLT, and (iii) in the axial plane of the tallest cusps. Median values for the spacing of calcospheritic lines closest to the GLT in the ground sections increased from 1.8 to 2.8 microm as the lines gradually coalesced into a laminar pattern beyond the GLT pulpally. Median values for the spacing of short-period lines in the cuspal dentine, where dentine formation is known to be fastest, were 4.1 microm. Markings in the demineralized sections were between 25 and 39% closer together, presumably due to contraction and shrinkage during specimen preparation. The spacings of short-period incremental lines measured on ground sections of non-human primate dentine (gibbon, siamang, orang) and on pig dentine, all between 100 and 200 microm from the GLT, clustered between 2.5 and 3.5 microm. Apart from gibbon dentine (in which spacings were closer together in this position than in the others), the distribution of measurements was not significantly different in pig, orang or human dentine. However, none of the data for the comparative samples presented here revealed spacings of short-period lines anywhere close to the 16 microm previously reported for circumpulpal dentine in animals. These data suggest that there may be many other animals where the mode and, to some extent, rate of dentine mineralization close to the root surface follows a common pattern. While data for the spacing of incremental markings in dentine provide no evidence for their periodicity, it is clear that the measurements made in the ground sections match the reported daily rates of mineralization at these locations, whereas those in demineralized silver-stained sections do not. Tissue shrinkage is probably a better explanation for this than the generally accepted view that they represent 12 h increments of dentine mineralization. This study provides a better basis for identifying and describing these lines, and for distinguishing them from other kinds of incremental markings in dentine.

Animals↗

PubMed1999

A computerized analysis of the relation between the occlusal enamel caries lesion and the demineralized dentin.

It has previously been shown that the demineralized dentin does not spread laterally along the enamel-dentin junction in non-cavitated approximal lesions. This study examined the spread of the dentinal part of occlusal lesions along the enamel-dentin junction. The material consisted of 48 well-defined occlusal lesions with histological evidence of dentin demineralization. The teeth were embedded in methylmethacrylate, serially-sectioned, ground, and contrast-stained. The sections with the deepest lesion penetration from each lesion were photographed and scanned by a high-quality scanner in order to produce images for computerized histomorphometric analysis. Two variables were measured on the images: i) the length of the contact area of the enamel lesion along the enamel-dentin junction; and ii) the length of the contact area of the demineralized part of the dentin lesion along the enamel-dentin junction. The results showed a gradual increase in the lengths of the enamel and dentin contact areas between the sections, each representing well-defined progressive stages of lesion formation. In two-thirds of the non-cavitated lesions, the enamel lesion was larger than the demineralized part of the dentin lesion, and in 50% of the cavitated cases the extension of the demineralized dentin was less than the affected enamel. Our conclusion is that the dentin demineralization did not spread significantly in a lateral direction in non-cavitated occlusal lesions.

Coloring Agents↗

PubMed1996

Adherence of Streptococcus gordonii to smeared and nonsmeared dentine.

The purpose of this study was to investigate the adherence of Streptococcus gordonii to smeared and nonsmeared dentine and to assess the influence of patent dentinal tubules on bacterial retention. In order to examine bacterial adherence, 10 non-smeared (group 1) and 10 smeared samples (group 2) of outer root dentine were prepared from teeth exhibiting dentine sclerosis. Ten non-smeared samples from inner coronal root dentine that did not exhibit sclerosis were prepared in order to study the influence of patent tubules on bacterial retention (group 3). Cells of the bacterium were radioactively labelled and an adhesion assay was performed. The number of bacteria adhering to the dentine surface was determined by scintillation counting. The results show that the number of bacteria adhering to both smeared and non-smeared outer sclerotic dentine was low (0.3% of inoculum), and there was no significant difference between the groups (P > 0.3). A significantly higher number of bacteria was retained on the inner non-smeared coronal root dentine (P < 0.0001) compared to groups 1 or 2. The results suggest that dentinal smear layers do not enhance or impede bacterial adherence to the dentine matrix. Dentinal surfaces with patent dentinal tubules retain more bacteria than a smeared surface.

Bacterial Adhesion↗

PubMed1996

A scanning electron and confocal laser microscope investigation of tetracycline-affected human dentine.

Because of the well reported dental side-effects of tetracycline administration, the drug should not be administered to children. However, it and its derivatives are often administered over a prolonged period for treatment of acne in young adults. Dental side effects are also noticed in these patients. The aim of this study was to examine with scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) the root dentine of a tooth from a young adult affected by tetracycline therapy. The palatal root of an upper third molar, demonstrating distinct areas of tetracycline staining, was removed from the crown and sectioned longitudinally to produce two samples. The pulp tissue was peeled off the dentine and any remaining non-mineralized tissues were removed with sodium hypochlorite. One sample was prepared for SEM and the other as a ground section which was examined with a CLSM. It was demonstrated by SEM that the mineralizing front of unaffected dentine was of a normal calcospherite appearance; in contrast, the mineralizing front of the tetracycline-affected dentine was devoid of calcospherite formation and many surface defects were apparent. In addition, the number of dentinal tubules associated with the defects was reduced. It was shown by CLSM that tetracycline bands were made up of numerous smaller bands and that peritubular dentine not associated with fluorescent bands had incorporated tetracycline. The CLSM examination of the mineralization front of the affected dentine revealed that fluorescence of dentine was restricted to the peritubular dentine. The results confirm that dentine mineralization is affected by systemic tetracycline therapy and that tetracycline can be incorporated into peritubular dentine after mineralization of the primary dentine matrix.

Adult↗

PubMed2006

Fluoride's effect on human dentin ultrasound velocity (elastic modulus) and tubule size.

Despite fluoride (F) use in caries prevention, not much is known about its effects on tooth quality. This study evaluated the effect of tooth F concentration ([F]) on selected dentin structural and mechanical properties. Third molars (n = 136) from Toronto, which has 1 part per million (p.p.m.) water [F], Montreal (0.2 p.p.m. water [F]), and Fortaleza (Brazil) (0.7 p.p.m. water [F]), were analyzed for [F], dental fluorosis (DF) severity, ultrasound velocity, and dentin tubule size and density. The enamel [F] was found to vary between 32 and 940 p.p.m., the dentin [F] was found to vary between 110 and 860 p.p.m., while the DF severity varied between TF0 and TF4. The enamel [F] showed no correlation with dentin [F], DF severity, ultrasound velocity, dentin tubule size or density. The dentin [F] correlated with DF severity, dentin tubule size, and ultrasound velocity. DF severity showed a correlation with dentin [F] and ultrasound velocity. It was concluded that dentin [F] is an indicator of dentin structural properties (dentin tubule size and ultrasound velocity), while DF severity is an indicator of dentin mechanical properties (ultrasound velocity).

Analysis of Variance↗

PubMed2005

Flexural strength and modulus properties of carbamide peroxide-treated bovine dentin.

BACKGROUND: The effects of carbamide peroxide bleach on tooth structure are uncertain. PURPOSE: The purpose of this study was to investigate the effects of direct or indirect carbamide peroxide application on dentin flexural strength and modulus in vitro. MATERIALS AND METHODS: Dentin bars were machined from bovine incisors and treated with 10% carbamide peroxide for 6 h/d for 14 days. Four groups were created, with eight bars in each group: group 1-direct bleach application only; group 2-indirect bleach application only; group 3-direct bleach application followed by a 2-week storage in artificial saliva; group 4-direct bleach application followed by a 2-week storage in artificial saliva and daily topical fluoride treatments. The specimens' flexural strength and modulus were tested after 24 hours, and the results were compared with water controls using independent t-tests (p < .05). RESULTS: Flexural strength results (in megapascals) for bleached versus control dentin (1=205+/-26 vs 215+/-14, 2=257+/-25 vs 261+/-14, 3=180+/-22 vs 193+/-36, 4=157+/-18 vs 184+/-11) were significantly lower in group 4 (p=.005). Modulus results (in gigapascals) for bleached versus control dentin (1=10.7+/-1.4 vs 12.2+/-0.6, 2=14.2+/-1.7 vs 14.4+/-1.6, 3=10.0+/-2.0 vs 10.9+/-1.3, 4=9.0+/-1.2 vs 11.1+/-1.0) were significantly lower in groups 1 and 4 (p=.013 and p=.003, respectively). There were no significant differences in strength and modulus results between the bleached and control dentin in groups 2 and 3. A direct application of carbamide peroxide to bovine dentin significantly decreased some dentin mechanical properties in vitro. An indirect application of carbamide peroxide to dentin did not significantly decrease dentin strength and stiffness. CLINICAL SIGNIFICANCE: This in vitro study suggests that a bleaching treatment, when applied to the enamel of intact teeth, does not significantly affect the mechanical properties of the underlying dentin. However, when applied directly to dentin in clinical situations such as root exposure or occlusal attrition, the bleaching treatment may result in altered mechanical properties of dentin. The clinical consequences of this observation are, however, unknown.

Animals↗