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PubMedDate not supplied

Effect of active pretreatment of self-etching primers on the ultramorphology of intact primary and permanent tooth enamel.

PURPOSE: The objective of this study was to evaluate the ultramorphological changes after agitated and nonagitated application of self-etching primer systems on unground primary and permanent enamel. METHODS: Five self-etching primer systems were used: (1) Clearfil SE Bond; (2) Clearfil Protect Bond; (3) Adper Prompt; (4) Xeno III; and (5) nonrinse conditioner (NRC). Noncarious human primary and permanent incisors were collected and stored frozen until used. Intact labial surfaces were divided into 2 halves, applying the self-etching primers with (active application) and without (inactive agitation) using a microbrush within the times recommended by the manufacturers. Treated surfaces were further processed for ultramorphological evaluation under scanning electron microscope (SEM). RESULTS: All tested self-etching systems produced weaker etch patterns and less dissolution of enamel surface compared with acid-etched samples in both primary and permanent teeth. Except for NRC and Adper Prompt, agitation of the surface did not increase the etching efficacy. Clearfil SE Bond and Clearfil Protect Bond resulted in similar morphological features following application in either mode. CONCLUSION: While agitation of self-etching primers may improve etching efficacy, this effect appears to be dependent on the material used. Phosphoric acid produces well-defined etching patterns on intact primary and permanent enamel.

Acid Etching, Dental↗
PubMed1999

Effectiveness of the addition of water-soluble photoinitiator into the self-etching primers on the adhesion of a resin composite to polished dentin and enamel.

The effectiveness of the addition of a photoinitiator into self-etching primer was investigated by measuring the tensile bond strength between a resin composite and dentin or enamel. The addition of camphorquinone to 5 M (5 wt% MDP -35 wt% HEMA aqueous solution) or 30 M (30 wt% MDP -35 wt% HEMA aqueous solution) did not increase the bond strengths of resin composite to dentin or enamel. On the other hand, the bond strength to dentin was increased by the addition of a water-soluble photoinitiator, 2-hydroxy-3-(3,4-dimethyl-9-oxo-9H-thioxanthen-2-yloxy)-N,N, N-trimethyl-1- propanaminium chloride (QTX) to 5 M or 30 M. The bond strengths to enamel were not influenced by the addition of QTX to 5 M or 30 M.

Acid Etching, Dental↗
PubMed1989

Properties of a glass-ionomer/resin-composite hybrid material.

A small percentage of the liquid resin used in commercial dental composites was added to the liquid used in a commercial glass-ionomer restorative in order to produce a fluoride-containing hybrid restorative-type material that would adhere to dentin while being stronger, less brittle, and less sensitive to desiccation in the oral cavity than glass ionomer. Compressive strength, yield strength, elastic modulus, fracture toughness, and tensile strength were analyzed for this hybrid, light-cured material. In addition, the solubility in water, adhesion to dentin, and surface roughness were also examined in vitro. The results suggest that the early (one-hour) mechanical properties of the hybrid material exceed those of glass ionomer. In addition, the brittleness and solubility of the material are less than those of commercial glass ionomer, while adhesion to dentin is unaffected. Most importantly, surface crazing, a documented problem with some glass ionomers when they become desiccated, is alleviated with this hybrid formulation.

Composite Resins↗
PubMed1991

Metalloproteinases in the mineralized compartments of porcine dentine as detected by substrate-gel electrophoresis.

Several gelatinolytic activities were detected in the 4M guanidine HCl-soluble fraction extracted from demineralized porcine dentine matrix. These matrix proteinases were active in the range of pH 6-9, and the activities were enhanced by calcium ions. The enzymes also degraded some of the non-collagenous proteins coexisting in the extract. The results indicate that the changes in the composition of non-collagenous proteins during the development of dentine are related to proteolytic enzyme activity.

Albumins↗
PubMed1992

Hard-tissue substrates for evaluation of cariogenic and anti-cariogenic activity in situ.

Hard-tissue substrates include primarily human and bovine enamel and human dentin. They have been used for in situ studies in a natural or sound condition, as well as flattened or containing an in vitro-formed caries-like lesion. Human enamel and dentin are generally the substrates of choice for studies of coronal and root-surface caries, respectively, but bovine enamel appears to offer a suitable alternative for many studies of enamel caries. Substrates with caries-like lesions will respond more rapidly to changes in the intra-oral mineral equilibrium and will allow both demineralization and remineralization to be determined. Findings from some studies suggest that caries-like lesions may respond somewhat differently, depending upon the degree of mineralization of the surface layer. Because in vitro findings with dentin show it to be significantly more soluble in acid than enamel, results from a study that used dentin may not be directly applicable to enamel. Both enamel and dentin substrates can be used in thin-section models. Hard-tissue substrates can also differ, depending upon their intra-oral location. Locations that result in the accumulation of plaque will behave differently from those that are plaque-free. So that plaque would accumulate, substrates have been placed approximally, beneath a fabric or steel mesh, in a protected trough, beneath a metal band or within a depression on the buccal surface. For studies requiring a determination of both demineralization and remineralization, human enamel or dentin containing a surface-softened caries-like lesion and covered with a uniform natural plaque are the substrates of choice.

Animals↗
PubMed1999

In situ fluoride retention in enamel and dentine after the use of an amine fluoride dentifrice and amine fluoride/sodium fluoride mouthrinse.

The aim of this in situ investigation was to study the effect of an amine fluoride/sodium fluoride mouthrinse (total F = 250 ppm) in addition to an amine fluoride dentifrice (F = 1,250 ppm) on the amount of acquired fluoride in enamel and dentine. In the partial prosthesis of 12 participants a combined specimen of slightly demineralized enamel and dentine was placed. During two consecutive experiments, each lasting 3 weeks, the participants used an amine fluoride dentifrice alone or in combination with a fluoride mouthrinse. After the in situ period the specimens were retrieved and both the enamel and the dentine specimens were analysed for the amount of KOH-soluble fluoride and structurally bound fluoride. The results showed a significant increase in both KOH-soluble and structurally bound fluoride in enamel and dentine when a fluoride mouthrinse was used. Whether the rinsing procedure was performed immediately after toothbrushing or with a delay of 2 h did not influence the results. Furthermore it was shown that dentine acquired substantially more fluoride than enamel during the experimental period. The results indicate that a fluoride mouthrinse used in addition to a fluoride dentifrice may have a beneficial effect on the protection of enamel and dentine against caries.

Adsorption↗
PubMed2001

Scanning electron microscopic description of cellular activity and mineral changes in feline odontoclastic resorptive lesions.

The cellular activity and changes in mineral composition of dental tissues involved in feline odontoclastic resorptive lesions were investigated. Teeth with at least 1 lesion (n = 10) were extracted from 10 different cats that were presented primarily for chronic gingivostomatitis and/or severe periodontal disease. Scanning electron microscopic methods were used to determine the presence of resorptive cells in 8 teeth while 2 teeth were evaluated for pathologic changes in dental mineral composition. Observations were complicated by the presence of organic wear on the dental surfaces, however resorptive cells could be clearly identified in feline odontoclastic resorptive lesions. Resorptive cells had morphologic features indicative of "osteoclast-like" cells or odontoclasts. Resorptive cell activity created a resorption area of darker dentin continuous with physiologic dentin. The darker dentin area seemed poorly mineralized and showed a significantly lower calcium/phosphorous ratio compared with adjacent physiologic denting in 1 tooth. A significantly higher level of magnesium combined with available carbonate ions may have increased the solubility in areas of darker dentin.

Animals↗
PubMed1990

Chondrocyte-like colony formation of mesenchymal cells by dentin extracts in agarose gel culture.

In this study, the effects of guanidine extracts from demineralized bovine dentin matrix on rat mesenchymal cells were investigated by use of an agarose gel culture. The dentin extracts were divided into water-soluble and -insoluble fractions. Rat mesenchymal cells obtained from the cultivation of skeletal muscle tissue and embedded in agarose gel were treated with these two fractions. After three weeks of cultivation, the treated cells formed colonies that were stained metachromatically with toluidine blue in a dose-dependent manner. The activity necessary to form chondrocyte-like colonies by the water-insoluble fraction was significantly higher than that by the water-soluble fraction. Each chromatographic fraction of the water-insoluble part of dentin extracts on tandem Sephacryl S-200 High-resolution columns was also investigated. Chondrocyte-like colony-forming activity was concentrated in a single fraction. However, the electrophoretic pattern of this fraction revealed that there were still some bands of molecular weight between 18 and 30 kDa. According to the Western blot analysis of this fraction, there was a band corresponding to purified transforming growth factor beta (TGF-beta) under the non-reducing condition. After reduction, this band disappeared and we found a band corresponding to a component of 13 kDa as well as TGF-beta. These findings suggest that TGF-beta is present not only in bone but also in the dentin matrix.

Animals↗
PubMed1976

The cyanogen bromide peptides of bovine soluble and insoluble collagens. II. Tissue specific cross-linked peptides of insoluble skin and dentin collagen.

Cyanogen bromide peptides were prepared from insoluble bovine skin and dentin collagens and compared by electrophoresis in polyacrylamide gels containing sodium dodecylsulphate, with those of the alpha1 and alpha2 chains of soluble type I and type III collagen. Both insoluble collagens yielded predominantly the peptides of type I collagen. Insoluble skin collagen was approximately 13% type III. Type III collagen if present in dentin, is present in smaller quanitity not detected by the technique used here. Several new fragments, different in each tissue, were obtained which could not be accounted for as uncleaved peptides. Three of those from dentin were isolated by gel chromatography and characterized by amino acid analysis. Two were found to contain 3-hydroxyproline, suggesting the presence of alpha1CB6. The recovery of only 25-30% of alpha1CB6 in the expected position on SDS gel electrophoresis indicated that it was involved in interactions with other peptides in these two tissues to the extent of one and a half cross-links per tropocollagen molecule. The nature and distributin of cross-link peptides of bovine skin and dentin collagens was distinctly different.

Amino Acids↗
PubMed1991

A rat incisor dentin matrix protein can induce neonatal rat muscle fibroblasts, in culture, to express phenotypic products of chondroblastic cells.

Demineralized dentin matrix induces the ectopic formation of bone, in vivo, when implanted subcutaneously or in muscle pouches. In these situations the bone induction follows a chondrogenic pathway. As part of the strategy for the assay and isolation of the factors responsible for initiating induction, we have developed a cell culture system in which the addition of soluble factors extracted from the dentin matrix appears to initiate chondrogenesis. Indicators of chondrogenesis, relative to control cultures, were taken as an increase of 35S-sulfate incorporation into proteoglycan (PG), an altered size of the PG, production of type II collagen, and changes in cell morphology and matrix histochemistry. Our studies have taken two directions: the use of the cell culture system under standard conditions to select fractions inducing one or more of the above indica-tors; and, the purification and characterization of the in vitro chondrogenesis inducing factor(s). Here we report the identification of a peptide fraction which acts in culture to satisfy each of the above indicators of chondrogenesis. An EDTA extract of rat incisor dentin was fractionated by CaCl2 precipitation, Sephacryl S-100 chromatography, and reverse phase HPLC. A single peptide fraction from the HPLC, evidenced by the existence of a single spot on 2-D Gel Electrophoresis, was found to be a potent enhancer of 35S-sulfate incorporation during the standard assay, with maximal activity in the 1-10 ng/ml range. Further detailed studies showed that the heightened incorporation occurred without any increase in cell number. The neonatal rat muscle explant fibroblasts exposed to this fraction for 7 days in monolayer culture formed dense cell nodules which stained intensely with Alcian blue relative to controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Quantitative evaluation of the influence of dequalinium acetate and sodium hypochlorite on human dentition.

The effect of 5 percent DA, 2.5 percent and 5.5 percent sodium hypochlorite, and saline on the solubility of organic matrix of the dentin was studied on extracted human teeth. The results showed that sodium hypochlorite dissolved collagen from the canal walls, while DA did not dissolve any collagen into the media. It is concluded that the root-canal-cleansing effect of DA is achieved by another mechanism, most likely by surface activity.

Chemical Phenomena↗
PubMed1994

Permeability of biological and synthetic molecules through dentine.

The diffusion through dentine by a number of biological and synthetic molecules, including resins and dyes, is reported. In vitro measurements were derived by experiments with a modified 'split-chamber device'. Diffusion was found to be indirectly proportional to dentine thickness for all molecules. Permeability of water-soluble molecules and ethanol-soluble molecules was proportional to the molecular weights, except for fluorescein, hydrogen peroxide (H2O2) and urethane dimethacrylate. The resin components tested are not soluble enough in an aqueous medium to diffuse through 0.5 mm dentine at sufficient concentrations to cause cytotoxicity to pulpal cells.

Blood Proteins↗
PubMed2006

Net expansion of dried demineralized dentin matrix produced by monomer/alcohol saturation and solvent evaporation.

The purpose of this work was to determine if nonaqueous methacrylate monomer/alcohol mixtures could expand dried collapsed demineralized dentin matrix. Thin disks (ca. 200 microm) of human dentin were demineralized and placed in wells beneath contact probes of linear variable differential transformers. The probes were placed on water-saturated expanded matrices to record the shrinkage associated with drying. Monomer mixtures containing hydroxyethyl methacrylate, 2,2-bis[4-(2-hydroxy-3 methacryloyloxy)propoxyphenyl] propane, or triethyleneglycol dimethacrylate were mixed with methanol or ethanol at alcohol/monomer mass fraction % of 90/10, 70/30, 50/50, or 30/70. They were randomly applied to the dried matrices to determine the rate and magnitude of expansion; then shrinkage was recorded during evaporation of the alcohols. The results indicated that matrix expansion was positively correlated with the Hoy's solubility parameters for hydrogen bonding forces (delta(h)) of the monomer/solvent mixtures (p < 0.001). Expansions were more rapid with methanol-containing than with ethanol-containing monomer mixtures. For the test solutions, triethyleneglycol dimethacrylate-containing mixtures produced the slowest rate of matrix expansion and hydroxyethyl methacrylate-containing mixtures the most rapid expansion. When the solvents were evaporated, the matrix shrank in proportion to the solvent content and the delta(h) of the monomer-solvent mixtures. The results indicate that expansion of dried, collapsed dentin matrices requires that the delta(h) of the mixtures be larger than 17 (J/cm(3))(1/2). The greater the delta(h) of the monomer solutions, the greater the rate and extent of expansion.

Alcohols↗
PubMed1975

Low-temperature ashing of bovine dentine.

The present studies were performed to obtain data on the low-temperature ashing (lta of dentine. Observations of colour and acid solubility, measurement of weight loss, and chemical analyses of carbon, hydrogen, and nitrogen assessed the ashing efficiency. The LTA method was sufficient to deproteinize dentine powder below 300 mesh. The determinations of calcium, magnesium, and phosphorus in dentine showed no significant differences between LTA, muffle furnace ashing (MFA), and wet ashing. The carbonate content was not significantly different after drying and LTA, but apporximately 48% carbonate was lost using MFA. X-ray diffraction patterns of dentine powder showed no detectable changes before and after LTA treatment compared to the patterns after treatment by MFA and/or ethylenediamine extraction.

Animals↗
PubMed1994

Clinical diagnosis of occlusal dentin caries.

An occlusal restoration is usually considered necessary when a lesion extends into the dentin. This study aimed to assess the relationship between the clinical appearance of occlusal caries and the lesion depth. Special attention was paid to differentiate the inner, partly demineralitzed layer of carious dentin that should be preserved from the outer carious layer that should be removed before placing a restoration. Fissures in extracted premolars and molars were classified clinically by the authors. The mean pairwise interobserver agreement, weighted Cohen's kappa (kappa), was 0.73, which indicated 'substantial agreement'. The depth of zones revealing softness by probing and/or discoloration was assessed on ground surfaces. Of the carious fissures that were scored sound by clinical examination (n = 17), 76% revealed enamel lesions on the ground surfaces. Of those occlusal surfaces with a discoloration only but no cavitation (n = 57), 13 showed dentin lesions, but only 5 of these revealed softness by probing. Of those lesions with very small cavitations (n = 60), 19 were confined to enamel, 41 showed dentin lesions and of these 32 revealed softness by probing. All but 1 of the lesions with small cavitations (n = 28) showed dentin involvement and all but 2 of these revealed softness. If cavitation in the occlusal lesion was used as a criterion for identifying dentin lesions with softness, the sensitivity and specificity values were 0.92 and 0.69, which means a relatively high frequency of overregistration.

Bicuspid↗
PubMed1986

Intraoral bacterial growth on tetracycline-impregnated dentin.

Previous studies have shown that tetracyclines react with enamel and dentin in vitro to form slightly soluble compounds with a pronounced and long-lasting antimicrobial capacity. The purpose of the present project was to study the effect of doxycycline-impregnation of dentin on the growth of oral microorganisms in vivo. Slabs of native human dentin were immersed in aqueous solutions of doxycycline HCl, 10 mg/ml, for 10 min, and were subsequently ligated to orthodontic brackets placed bucally on maxillary molars in seven individuals. Untreated native dentin specimens were similarly placed on contralateral teeth. Test and control specimens were removed from the oral cavity after 2 h, 24 or 120 h, respectively. The individual specimens were then placed in 0.5-ml saline and agitated mechanically for 30 s. The resulting bacterial suspensions were plated onto blood agar and various selective growth media. Based on CFU-counts obtained after incubation of the plates, doxycycline-treated dentin specimens showed a significantly lower number of viable microorganisms after 2 h and 24 h in the oral cavity than did the control specimens. The bacterial growth was also less pronounced in the test specimens after 120 h. The effect of doxycycline was similar for all the cultivable bacteria. No significant difference in yeast growth was seen between test and control specimens.

Bacteria↗
PubMed2002

The effects of the solubility of artificial fissures on plaque pH.

Dissolution of the fissure walls may buffer acids formed in plaque and thus prevent the penetration of acids into the fissure. To test this, five volunteers wore dentin, enamel, and polyacrylate specimens with narrow grooves for 7 days to accumulate plaque. Temporal (pre- and post-glucose) and spatial (0-0.7 mm) pH profiles were recorded in the grooves in a flow-through reactor with pH microsensors. Mineral loss was assessed by transverse microradiography. We observed that resting pH did not differ among substrata. The median pH 1 hr post-glucose at the bottoms of dentin, enamel, and polyacrylate grooves was 6.7, 6.2, and 5.7, respectively (p < 0.01). On subject level, lesions formed in dentin correlated with pH changes in polyacrylate, where no buffering of acids due to mineral dissolution occurred. We conclude that fluoride-deficient tissue at the bottom of a fissure is at increased risk for caries, if acids are not buffered near the entrance to the fissure.

Acids↗
PubMed1977

Microscopy of the junctional region between human coronal primary and secondary dentine.

The juction between human primary dentine and regular and irregular secondary dentine was examined with a number of different light and electron microscopic techniques. In decalcified material, a narrow band along the innermost surface of the primary dentine stained intensely. The walls of the tubules within the band stained intensely, whereas the tubular walls within the bulk of the primary dentine were not stained. Generally, the walls of the tubules in both types of secondary dentine were also preferentially stained. Although not readily apparent in ground sections, observations of thin sections revealed a dramatic reduction in the number of tubules in regular secondary dentine. Generally, the radiodensity of the intertubular matrix was the same in primary and secondary dentine and the intensely stained band was not seen radiographically. The pulpal ends of the tubules in primary dentine were often occluded with a material having the same radiodensity as peritubular matrix. Both patent and occluded tubules were seen in irregular secondary dentine. Scanning electron microscopy of acid-etched specimens of secondary dentine revealed that some tubules had irregular walls of highly mineralized matrix which was less acid-soluble then the peritubular matrix of primary dentine.

Cuspid↗