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PubMed1995

Mineral element analysis of carious and sound rat dentin by electron probe microanalyzer combined with back-scattered electron image.

We recently demonstrated the advantages of back-scattered electron images (COMPO) in the visualization of dentinal caries, and the relationship of the change in the dentin fluorescence pattern in caries lesions. However, the exact nature of these changes is not known. In this paper, the nature of the changes in the areas with reduced mineral content in COMPO images was investigated. We examined the relation of changes in mineral elements and the appearance of soft carious and sound dentin in COMPO images using a scanning electron microscope (SEM) equipped with an electron probe microanalyzer (EPMA). Rat molars with small dentinal caries lesions just under the DEJ were chosen for the study. The Ca, P, Na, Mg, Zn, F, and total contents were determined by EPMA from five different dentin sites, and the Ca/P and Mg/Ca ratios were calculated. Generally, the lowest contents were found in caries lesions and highest in mantle dentin, with the exceptions of Mg and Zn. The Ca/P ratio was lowest in mantle dentin and highest in carious dentin. The results confirm that the change in fluorescence in the dentinal caries lesion is correlated with the very initial changes in mineral content, and that EPMA used in combination with COMPO images is a useful tool for determining small changes in mineral elements in the carious and adjacent areas of dentin.

Animals↗

PubMed2005

How does fluoride affect dentin microhardness and mineralization?

Fluoride (F) has been a useful instrument in caries prevention. However, only limited data exist on the effect of its long-term use on dentin mineralization patterns and microhardness. The objective of this study was to evaluate the influence of tooth F concentration ([F]) and dental fluorosis (DF) severity on dentin microhardness and mineralization. We collected 137 teeth in Montreal and Toronto, Canada, and Fortaleza, Brazil, where optimum or suboptimum levels of water F were 0.2 ppm, 1 ppm, and 0.7 ppm, respectively. Teeth were analyzed for DF severity, dentin [F], enamel [F], dentin microhardness, and dentin mineralization. Dentin [F] correlated with DF severity; enamel [F] correlated with dentin microhardness and dentin mineralization; DF severity correlated with dentin microhardness. Genetic factors (e.g., DF severity) and environmental factors (e.g., tooth [F]) influenced the mechanical properties (microhardness) of the teeth, while only the environmental factors influenced their material properties (e.g., mineralization). Fortaleza teeth were harder and less mineralized and presented higher dentin [F] values. Montreal teeth presented lower levels of DF when compared with both Toronto and Fortaleza teeth.

Adolescent↗

PubMed1999

Assessing dentin color changes from nightguard vital bleaching.

BACKGROUND: At-home bleaching with 10 percent carbamide peroxide in a custom-fitted tray has been reported to change the color of dentin. The purpose of this study was to validate the color change of dentin and to determine whether the color change was uniform or occurred from the outside (the dentinoenamel junction) to the inside (the pulpal wall). METHODS: The authors sectioned 10 extracted human teeth incisogingivally through the midfacial long axis, and sealed their cut surface against glass microscope slides. Identifying marks were placed on the glass over the tooth sections to serve as a color control and in the dentinal areas closest to the dentinoenamel junction and the pulpal wall. Teeth were bleached for 10 days with 10 percent carbamide peroxide. Photographs were taken from the glass-covered side of the teeth, digitized and converted to gray-scale levels (consisting of 256 shades of gray ranging from black to white). Marked areas were measured with a National Institutes of Health Image software program and analyzed statistically for changes in lightness between the control marks and the inner and outer dentinal marks over time. RESULTS: Paired t-tests and analysis of variance indicated a significant increase in lightness (P = .01) for the inner and outer dentinal areas during bleaching compared with the control areas. No significant differences were found in the rate of change for the inner and outer dentinal areas (P = .89). CONCLUSIONS: The increase in lightness confirms that a significant color change occurred in the dentin during bleaching with 10 percent carbamide peroxide. This change occurred throughout the dentin at a uniform rate, rather than from the outside inward. CLINICAL IMPLICATIONS: The results of this study show that at-home bleaching with 10 percent carbamide peroxide can change the color of dentin, which is important to treat intrinsic stains from tetracycline treatment, trauma and aging or inherited discolorations. The bleaching material easily penetrates the tooth to change the dentin color at the same rate throughout, indicating that the type of stain may be the important factor in determining bleaching success.

Absorptiometry, Photon↗

PubMed1988

Initial wound healing attachments to demineralized dentin.

This report describes the initial in vivo wound healing response of connective tissue components and cells to demineralized and nondemineralized dentin surfaces. Rectangular dentin specimens were prepared from beneath root surfaces covered by periodontal ligament. One group of six specimens were treated with citric acid, while another six specimens served as untreated controls. Specimens were implanted vertically into the skin of rats such that one end of the implant protruded above the skin. After one day, the implants were removed, and the dentin surface-connective tissue interface was examined using scanning electron microscopic methods. The surface of the nondemineralized dentin implants had the morphological characteristics of a surface smear layer. Cells that were present on these nondemineralized surfaces were rounded in shape with few processes or extensions to the dentin surface or to other cells. The surfaces of the demineralized dentin implants were fibrillar in appearance and were usually covered by a layer that had many globular and fibrillar structures attached. Cells that were present on these demineralized surfaces exhibited marked bipolarity with distinct attachments to the dentin surface. Cell processes often extended into the openings of demineralized dentin tubules. It was concluded that an established cellular and connective tissue response to demineralized dentin occurred within the first 24 hours of wound healing, and that this response differed markedly from that associated with nondermineralized dentin surfaces.

Animals↗

PubMed1989

[In vitro study of bacterial invasion in radicular dentin].

The purpose of this study was to investigate whether plaque bacteria invade exposed radicular dentin after root planing or chemical root treatment in vitro. Pieces of dentin were cut out from impacted third molars. The surface of all dentin pieces was treated with sandpaper (#240) so as to make the surface roughness of dentin pieces equal to that of the root surface after root planing (RP surface). Half of the dentin pieces were treated with citric acid (pH 1.0) for 3 minutes (CA surface). After sterilization, each dentin piece was incubated at 37 degrees C in a culture medium inoculated with either S. mutans or S. sanguis. After 1, 3, 7 and 28 days of incubation, the invasion of microorganisms into the dentinal tubules was histologically examined using a light microscope. The following results were obtained. 1. The invasion of S. mutans and S. sanguis into the dentinal tubules was observed at 1, 3, 7 and 28 days. The depth and number of bacterial invasion into the dentinal tubules were positively correlated with incubation time on CA surfaces but not with RP surfaces. 2. The depth and the number of bacterial invasion into the dentinal tubules were higher on the CA surfaces than the RP surfaces. 3. Since the citric acid treatment of scaled and root planed root surfaces may accelerate bacterial invasion from treated root surfaces, the use of citric acid might be harmful in patients with inadequate plaque control.

Dental Plaque↗

PubMedDate not supplied

Porcelain veneers: dentin bonding optimization and biomimetic recovery of the crown.

PURPOSE: The purpose of this study was to investigate the biomimetic principle in porcelain veneer reconstruction, or in other words, to assess the extent to which the restoration can mimic the biomechanics and structural integrity of the original tooth. Using an optimized luting procedure, porcelain veneers are expected to present such features even when bonded to an extensive dentin surface. METHODS AND MATERIALS: Dentin-bonded porcelain veneers were assessed using functional and cyclic thermal loads with respect to two parameters: coronal stiffness (investigated using experimental strain gauges and finite element analysis) and morphology of the tooth-restoration interface (scanning electron microscope evaluation). Two different application modes of the same dentin-bonding agent, Optibond FL, were evaluated: a traditional method (dentin adhesive applied when proceeding to luting the veneer) and an alternative method (dentin adhesive applied to dentin and cured before taking the impression for the veneer). RESULTS: In the finite element model, the crown compliance increased by a factor of 2.16 after facial enamel removal and returned to 96% of its original value after the placement of the veneer. The finite element values showed a good correlation with strain gauge experimental results (one-sample t test, P > 0.35 after facial enamel removal and P > 0.19 after veneer placement). The dentin adhesive application mode was not critical to the recovery of tooth stiffness (analysis of variance, P = 0.10). However, qualitative scanning electron microscope observations demonstrated that the traditional dentin adhesive application was associated with bonding failures between the hybrid layer and the overlying resin, whereas unbroken and continuous interfaces were obtained with the new method using the same dentin adhesive. CONCLUSION: The results of this study definitely favor the biomimetic behavior of porcelain veneers bonded to teeth using an optimized application mode of dentin adhesives, because this treatment modality proved to restore both the mechanical behavior and microstructure of the intact tooth.

Analysis of Variance↗

PubMed2001

Effect of solvent and rewetting time on dentin adhesion.

OBJECTIVE: The purpose of this in vitro study was to determine the influence of solvent and rewetting time on microtensile dentin bond strengths of four dentin adhesives. METHOD AND MATERIALS: Sixty human molar specimens were divided into four dentin adhesive treatment groups: (1) a water-based total-etch dentin adhesive, EBS Multi; (2) an ethanol-based total-etch adhesive, Excite; (3) an acetone-based total-etch adhesive, Prime & Bond NT; and (4) an ethanol- and water-based total-etch adhesive, Single Bond. For each dentin adhesive, three specimens were assigned to five dentin moisture conditions. Specimens were tested in the tensile mode. RESULTS: When adhesives were applied to moist dentin, bond strengths varied from 26.2 MPa for Prime & Bond NT to 29.5 MPa for Single Bond without any statistical differences. When applied to dentin that had been dried for 15 seconds, Prime & Bond NT and Excite resulted in the lowest mean bond strengths, but they were statistically similar to each other (7.9 and 8.3 MPa, respectively). Single Bond resulted in a mean bond strength of 12.7 MPa, which was significantly lower than that of EBS Multi (24.1 MPa). For the latter, all mean bond strengths were statistically similar when some amount of moisture was present on the surface. For the other three adhesives, mean bond strengths returned to the range obtained on moist dentin only when dentin was rewet for 30 seconds. CONCLUSION: Bond strengths upon rewetting depend on the type of solvent in the bonding system, and rewetting time.

Acid Etching, Dental↗

PubMedDate not supplied

Temperature transmission of high-output light-curing units through dentin.

Light-curing units used for polymerizing restorative resins produce heat during operation. Newer curing units with concentrating light guides or different light sources may require shorter curing times, however, the effect of such modifications on temperature transfer to the pulp is unknown. This study examined the effect of high output light-curing units on temperature transfer through resin composite and dentin. Temperature rise was measured for 40 seconds for one curing light (Optilux 401 Curing Light) with either a standard 8 mm light guide tip or a light-concentrating tip (Turbo Light Guide), and for three seconds with a plasma arc lamp (Apollo 95E Curing Light). Temperatures were directly recorded at the tip of the light guide and through a sandwich composed of a 1 mm thick pre-cured cylinder of resin composite and dentin (dentin thickness either 0.58 mm or 1.45 mm). The mean temperature rise ranged from 1.8degrees C, measured through the sandwich of 1 mm of composite and 1.45 mm of dentin with the plasma are unit, to 26.4degrees C measured directly on the Turbo light guide. For each light guide, the temperature increase was greatest when measured directly on the curing tip and least when measured through the composite and 1.45 mm dentin specimens. When measured through the composite/dentin sandwich, the plasma arc unit produced the lowest temperature increase (0.58 mm thick dentin specimen = 5.1 degrees C; 1.45 mm thick dentin specimen = 1.8 degrees C). For a given thickness of resin, the differences in temperature change for all comparisons among the three curing unit/light guides were significant at the 95% level of confidence. Also, for a given light, the differences in temperature for all comparisons among the dentin thicknesses were significant at the 95% level of confidence. However, there were three comparisons of light unit and dentin thickness interaction that were not significant at the 95% leyel of confidence. For all other comparisons of interaction, significant differences were found at the 95% level of confidence. The temperature increased by 42% to 56% when the Turbo Light Guide was used compared to the standard light guide for thick and thin dentin specimens, respectively.

Analysis of Variance↗

PubMed2003

[Inhibition of remineralization by EDTA-soluble phosphate protein in dentin].

OBJECTIVE: To investigate the effect of removing EDTA-soluble phosphate protein in dentin on the later remineralization for the purpose of better understanding of mechanism of dentin phosphate proteins on dentin mineralization. METHODS: To remove soluble phosphate protein by EDTA dissolution, then the remineralization rate was monitored by a constant composition crystal growth technique. The results were compared with those from the normal dentin and the dentin partially demineralized by acetic acid. RESULTS: Faster remineralization rates were found with dentin demineralized by EDTA (0.5 and 2 h) compared with normal dentin powder, while a slower rate was found with dentin demineralized by acetic acid. The increase of remineralization rate by removing phosphate protein from dentin was 100% more at 200 min after the start of the reaction. CONCLUSION: EDTA-soluble phosphate protein in dentin has a great potential to inhibit remineralization.

Dental Cementum↗

PubMedDate not supplied

The antimicrobial activity of a dentin conditioner combined with antibacterial agents.

Dental hand instruments are not efficient in removing all infected dentin when performing carious removal for minimal intervention techniques. The use of an antibacterial dentin conditioner may therefore be useful when restoring cavities that have residual carious dentin. Antibacterial agents--chlorhexidine hydrochloride, cetylpyridinium chloride, cetrimide, benzaIkonium chloride and sodium hypochlorite, were added either to a dentin conditioner used for glass ionomer cements or distilled water at 1% concentration. Dentin conditioning solutions at pH 2.5, 4.9 and 7.7 were also prepared, along with 1% aqueous thymol. Using an agar diffusion test, 25 microl aliquots were examined for their inhibitory effects on three cariogenic bacteria. After 24 hours, an agar pellet was extracted adjacent to the agar well and placed on a second inoculated agar plate to observe sustained inhibitory effects, after which this procedure was repeated one more time. Antibacterial dentin conditioners showed significant inhibitory effect compared to the control over the three test periods (p<0.016). The combination of dentin conditioners with antibacterial agents significantly reduced the inhibitory effect compared to the antibacterial aqueous solutions (p<0.016). One-percent aqueous thymol showed no inhibitory effect against the test bacteria. The cetrimide-dentin conditioner showed the greatest inhibitory effect against all three test bacteria over the three experimental periods (p<0.016). The inhibitory effect of antibacterial agents was significantly reduced when combined with a dentin conditioner. Only the cetrimide-dentin conditioner combination produced significant inhibitory effects against all three test organisms.

Acid Etching, Dental↗

PubMed2006

[Effect of host derived matrix metalloproteinase on the degradation of root dentin collagen].

OBJECTIVE: To evaluate the effect of dentin matrix metalloproteinase (MMP) on the degradation of root dentin collagen. METHODS: Root dentin powder was demineralized with acetic acid (pH 4.0) at 4 degrees C for 14 d, then dialysed and centrifuged. Precipitation was divided into 7 groups, with 6 samples in each group, and each sample was 50.0 mg. One milliliter artificial saliva with a different reagent was added in each sample respectively. The reagents were 2 mmol/L APMA (MMP activator), 2 mmol/L EDTA, 100 mmol/L EDTA, 200 mmol/L EDTA, 0.2% and 0.02% chlorhexidine (MMP inhibitor), and the blank artificial saliva was taken as control. The amount of degraded collagen of each sample was determined with hydroxyproline assay kit. Scanning electron microscope was employed to observe the morphological and structural changes of root dentin which was demineralized or put into artificial saliva after being demineralized. RESULTS: The mean amount of degraded collagen in APMA group was significantly higher than that in the blank group (P < 0.05). The mean amount of degraded collagen in 2 mmol/L, 100 mmol/L, 200 mmol/L EDTA, 0.02% and 0.2% chlorhexidine groups was dramatically lower than that of the APMA group and the blank (P < 0.01). SEM observation indicated that the structural integrity of the collagen network on root surface dentin still existed in root dentin surface after being demineralized alone, while collagenous fibril was destructed and the structural integrity on root dentin surface disappeared after being demineralized and treated by artificial saliva. CONCLUSIONS: MMP in root dentin can degrade root dentin collagen after being activated at low pH followed by neutralization. The results suggest that host MMP may play an important role in the process of dentin caries formation.

Collagen↗

PubMed1990

[Comparisons of effects of vitamin D3 metabolites on mineralization: utilization of incisor dentin in parathyroidectomized rats].

The rat incisor is continuously growing throughout the animal's life recording the state of mineralization within its dentin at all times. Therefore, it was assumed that the incisor dentin was suitable material for studying the effects of various drugs on such mineralization. The present study set out to examine the effects of vitamin D3 metabolites on the remineralization of dentin and the serum calcium level in parathyroidectomized (PTX) rats. Male Wistar rats weighing about 200-250 g were parathyroidectomized. Each rat was given daily 12 g of a synthetic diet containing 0.1% Ca and 0.4% P (normal P) or 0.06% P (P deficient) without vitamin D. Exp. I: Three groups of rats given a normal P diet were orally administered vehicle, 25 (OH) D3 (50 IU/rat) or 1,25 (OH)2D3 (5 IU/rat) for 5 days from the 28th day after PTX, respectively. Exp. II: Two groups of rats given a normal P diet or a P deficient diet were further divided into 4 sub-groups and intramuscularly administered 0, 5,000, 10,000 or 20,000 IU of vitamin D3 on the 9th day after PTX, respectively. The active vitamin D3, 1,25 (OH)2D3 restored the mineralization of the dentin which had been suppressed following PTX, and elevated the serum calcium level to about 9 mg/dl. However, the 25 (OH) D3 neither restored the mineralization of the dentin nor elevated the serum calcium level in the PTX rats. At doses below 1,000 IU, vitamin D3 could not restore the mineralization of the dentin. However, at massive doses above 5,000 IU, the mineralization was restored in proportion to the dose. The serum calcium levels also increased in proportion to the dose. It is assumed that the increase of the serum calcium level was mainly due to the enhancement of calcium absorption from the intestine by vitamin D3. Both remineralization of the incisor dentin and increase of the serum calcium level were more marked in groups of rats given a P deficient diet than in those given a normal P diet. In all cases in the present experiments, the degree of mineralization of the dentin seemed to correspond with the degree of elevation of the serum calcium levels. These results suggest that the remineralization of the dentin in the PTX rats was attributable to the effect of the vitamin D3 metabolites on serum calcium regulation. Relative biological activities of 1,25 (OH)2D3, 25 (OH) D3 and vitamin D3 on the remineralization of dentin were estimated to be 1, less than 0.02 and less than 0.001, respectively.

Animals↗

PubMed1990

[Appositional rate of incisor dentin and hematic calcium level in rats. Application of time marking method using lead acetate].

Matsumoto et al. have reported that the remineralization of rat incisor dentin following administration of various drugs depends upon the hematic calcium (hCa) level in parathyroidectomized (PTX) rats. It is known that injected lead according to a time marking method deposits at the mineralizing front in hard tissues. In the present study, we observed the alteration of the mineralizing front of the incisor dentin and examined the dependency of the dentin remineralization on the hCa level in PTX rats given 1,25 (OH)2D3. Male Wistar rats (7-8 weeks old) were used. They were fed a synthetic diet containing 0.3% Ca or 0.02% Ca (Ca-deficient) from 3 days before PTX. In order to mark the time in the incisor dentin, lead acetate was injected at 3 day intervals. Exp. I: A group of rats fed a diet containing 0.3% Ca was given a single injection (400 ng/kg) of 1,25 (OH)2D3 on the 9th day after PTX. Exp. II: four groups of rats were given daily injections of various doses (vehicle, 25, 50 and 100 ng/kg) of 1,25 (OH)2D3 from the 11th day after PTX for 13 days. The distance between the two lead-lines observed in the histological sections of the incisor was measured as an indicator of the appositional rate of dentin. In rats given a diet containing Ca below 0.3%, the hCa level was about 5 mg/dl after PTX. Mineralization of the incisor dentin was suppressed markedly, and a hematoxylin unstained zone was observed in the histological sections, indicating that the mineralizing front had been stagnant. In Exp I, a high dosage of 1,25 (OH)2D3 raised the hCa level to over 8 mg/dl within 12 hours; formation of a new mineralizing front and remineralization of the dentin were observed. In Exp. II, daily injections of 1.25 (OH)2D3 raised the hCa levels gradually and dose dependently. The hCa levels in groups of rats given 50 and 100 ng/kg of 1,25 (OH)2D3 were over 8 and 10 mg/dl respectively after the 6th day from the beginning of the drug administrations. The distance between the two lead-lines deposited in dentin also increased gradually. Therefore, the appositional rate of the incisor dentin seemed to increase in accordance with the rise in the hCa level. The correlation coefficient between the appositional rate of lingual dentin and the hCa level was estimated to be 0.922 (p less than 0.001, y = 4.4x + 19.2).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1989

[Changes of dentin matrices during carious process].

Studies were made on the effects of demineralization with lactic acid or acetic acid on the organic matrices of human sound dentin, and on the changes of the matrices during carious process. When sound dentin was demineralized with 0.5 M lactic acid or 0.5M acetic acid, non-collagenous proteins and a small amount of collagen were extracted. A larger amount of protein containing phosphophoryn was extracted with lactic acid than with acetic acid, whereas when acetic acid was used for demineralization and then followed by an EDTA solution most of the phosphophoryn was removed. Since EDTA will remove phosphophoryn from sound dentin, low level of phosphophoryn in the extract obtained by treating carious dentin with EDTA, suggests that during the carious process a loss of phosphophoryn occurs. The analyses of carious dentin fractionated by the difference of its density showed that the lower density fraction of carious dentin contained a larger proportion of non-collagenous components to collagen. By the dansylation of sound and carious dentin nine dansyl amino acids, such as aspartic acid, glutamic acid, serine, glycine, alanine, proline, valine, leucine and tyrosine, were detected in the sound dentin, and in addition to these nine amino acids isoleucine was found in carious dentin. The amount of the respective dansyl amino acids in the fractionated carious dentin increased with the decrease of density.

Dental Caries↗

PubMed1989

[On the peculiar dentin existing in the gutter-shaped root].

The purpose of this study is to investigate the histological structure of the gutter-shaped root. Materials investigated in this study deal with 15 japanese lower molars of adults having gutter-shaped roots and 2 of them of children. Buccolingual, mesiodistal, and horizontal ground sections of them were prepared and observed with binocular microscopy, polarizing microscopy, phase microscopy, fluorescent microscopy, microradiograph, and scanning electron microscopy. It is thought that the lingual dentin of the gutter-shaped root is transparent and roentgenopaque because it has primarily slender and sparse dentinal tubules. It is considered that the lingual dentin differs from the transparent dentin of which dentinal tubules were secondarily filled with calcified substance. It is considered that the lingual dentin of the gutter-shaped root is thinner than the buccal dentin because the forming time of the lingual dentin isn't brief but the forming speed of it is late. It is thought that the peculiar dentin is formed at the lingual part because one odontoblast shares more broad forming space of the dentin there than the other part.

Adult↗

PubMed1994

Identification of new rat dentin proteoglycans utilizing C18 chromatography.

Although only one small PG has been identified in dentin until now, a preliminary investigation has shown indications of the presence of several new proteoglycans (PGs) in rat incisor dentin. The aim of the present investigation was to isolate and characterize these PGs, which were labeled with 35S to facilitate the analysis. C18 chromatography resolved five dentin PGs. Based on SDS-polyacrylamide gel electrophoresis, their size varied from 100 to 400 kDa. The core proteins of the first four PGs appeared as 25, 40, 70, and 115 kDa bands. They stained turquoise with Stains All but did not stain with Coomassie Brilliant Blue. The core protein of the fifth PG appeared at about 45 kDa. This core protein stained with Coomassie Brilliant Blue but not with Stains All. In all PGs, the glycosaminoglycans consisted mainly of chondroitin 4-sulfate. To investigate their incorporation into predentin (young dentin that is not yet mineralized) and dentin, rat dentin PGs were pulse-labeled by injecting rats with [35S]sulfate at 5, 28, 55, or 177 h before killing the animals. Radiolabeling of predentin PGs was highest after 5 h and decreased rapidly (76%) over the next 50 h. In dentin PGs, a large percentage (34%) of the final quantity of incorporated 35S (at 177 h) was already present at 5 h. C18 chromatography of dentin PGs for each of the four time intervals showed similar 35S distribution patterns representing all five PGs, whereas the predentin appeared to contain mainly the fifth PG. This study demonstrates the existence of several apparently novel PGs in dentin that can be resolved by the use of a new method. These PGs were found in mineralized dentin and are thought to be rapidly transported toward the mineralization front. Part of the predentin PGs, on the other hand, seems to be lost as mineralization proceeds.

Animals↗

PubMed1996

Dentin formation after corticosteroid treatment. A clinical study and an experimental study on rats.

The overall aim of this series of studies was to determine whether the extensive narrowing of the dental pulp chamber seen in dental radiographs of patients with end stage renal disease was related to the method of treatment of the renal disease. The treatments studied were immunosuppression, renal transplantation and hemodialysis. A strong correlation was found between narrowing of the dental pulp chamber and renal transplantation. In the immunosuppression group and in the renal transplantation group, the patients received immunosuppressive drugs, mainly corticosteroids and azathioprine. Significantly higher doses of corticosteroids had been given to patients showing narrowing of the dental pulp chamber than to patients without such narrowing. The total plasma clearance of the corticosteroids received was measured among transplanted patients. The total plasma clearance was lower in patients with narrowing of the dental pulp chamber than in patients without narrowing. The morphology of the corticosteroid induced dentin in premolars from five deceased patients who had received one or more renal transplants each was compared with that in extracted teeth from five healthy individuals. The results of this study showed that dentin formation after high dose corticosteroid treatment in humans seems to start with a widening of the predentin zone, followed by extensive mineralisation causing substantial reduction of the dental pulp chamber within a few years after the start of treatment. In an experimental study on rats, it was shown that intravenous administration of high doses of corticosteroids induced dentin formation along the pulp chamber walls in the molars. Energy dispersive X-ray microanalysis was used for estimation of the calcium and phosphorus content of the dentin in rat teeth. The calcium and phosphorus composition of the corticosteroid induced dentin was found to be equal to that of normal dentin in control rat molars, which might imply that the mineralisation process was not affected by the corticosteroid treatment and thus the quality of the corticosteroid induced dentin might be equal to normal dentin regarding the calcium and phosphorus composition. In a scanning microscopy study of the morphology of the corticosteroid induced dentin in rat incisors, it was found to be equal to that of normally formed dentin.

Adolescent↗

PubMed1995

Influence of concentration and application time of maleic acid on dentin permeability.

OBJECTIVES: Since dentin permeability ultimately affects bond strength, the purpose of this study was to compare the effects of different concentrations of maleic acid, and different exposure times on dentin permeability. METHODS: One hundred and thirty freshly extracted human non-carious third molars were used. Hydraulic conductance was determined after various treatments. The teeth were divided into five groups. In the first group, the smear layer was untreated. In three other groups, 0.10, 0.25, or 0.5 M aqueous solution of maleic acid was applied on dentin slices for 15, 30, or 60 s. In the last group, the Scotchbond Multi-Purpose dental adhesive system (3M Dental Products) conditioner was applied for 15, 30, or 60 s. RESULTS: After a 60 s exposure time, the Scotchbond Multi-Purpose dentin conditioner or the 0.1 M solution of maleic acid was as effective at increasing dentin permeability as the 0.25 M and 0.5 M maleic acid solutions. The maximum dentin permeability was reached after 15 s with 0.25 M and 0.5 M solutions of maleic acid, after 30 s with Scotchbond Multi-Purpose and after 60 s with the 0.1 M solution of maleic acid. During the first 30 s, the 0.1 M solution of malic acid did not increase dentin permeability and did not completely remove the smear layer; a SEM examination of the dentin slices corroborated the functional results. SIGNIFICANCE: The manufacturer's recommendation of 15 s of etching using Scotchbond Multi-Purpose conditioning gel produced a moderate amount of etching which increases dentin permeability to about one-half its maximum value.

Acid Etching, Dental↗