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PubMed2002

How can nanoleakage occur in self-etching adhesive systems that demineralize and infiltrate simultaneously?

PURPOSE: Single-step adhesives which etch and prime simultaneously and are not rinsed should not exhibit areas of incomplete infiltration within hybrid layers produced in sound dentin. This study examined the extent of silver uptake using ammoniacal silver nitrate in three two-step, self-etching primers (Imperva Fluoro Bond, Shofu; UniFil Bond, GC, ABF system, Kuraray) and one single-step, self-etching adhesive (AQ Bond, Sun Medical) bonded to dentin and four poly(HEMA) resins used as controls. MATERIALS AND METHODS: Flat dentin surfaces were bonded with these adhesives and sectioned into 0.8-mm-thick slabs that were then coated with nail varnish except for the bonded interfaces and immersed in AgNO3 for 24 h. Four types of poly(HEMA) resins were made: 100% HEMA; 90% HEMA-10% water; 75% HEMA-10% water, all polymerized with TBBO at 50 degrees C for 6 h; 100% HEMA polymerized at 25 degrees C for 30 min. After developing, undemineralized, unstained, epoxy resin-embedded sections were prepared for TEM. RESULTS: Nanoleakage patterns were observed in all bonded specimens. Fine segregated silver particles and reticular silver-staining patterns were found within the thin hybrid layers created by the three self-etching primers. For the single-step, self-etching adhesive, heavy silver deposits were identified within the hybridized complex formed by this adhesive within the smear layer, the underlying intact dentin, and in the adhesive layer. Increasing amounts of silver uptake were observed in poly(HEMA) specimens containing more water or that were polymerized at 25 degrees C for a short time instead of 50 degrees C for 6 h. CONCLUSIONS: Silver uptake in hybrid layers formed by self-etching adhesives in sound dentin is not necessarily caused by disparities between the depths of demineralization and resin infiltration. They represent areas of increased permeability within a polymerized resin matrix in which water is incompletely removed resulting in regions of incomplete polymerization and/or hydrogel formation.

Acid Etching, Dental↗

PubMed2005

Effect of iron on bovine enamel and on the composition of the dental biofilm formed "in situ".

OBJECTIVES: This study investigated in situ the effect of iron (Fe) on the reduction of demineralization of bovine enamel, as well as on the composition of dental biofilm. DESIGN AND METHODS: Twelve volunteers were included in this blind crossover study, which was conducted in two stages of 14 days each. For each stage, the volunteers received palatal appliances containing four blocks of bovine enamel (4 mm x4 mm x 2.5 mm). Six volunteers dripped a solution of 15 mmol L(-1) ferrous sulphate onto the fragments and the remaining six dripped deionized water (eight times per day). After five minutes, a fresh 20% (w/v) sucrose solution was dripped onto all enamel blocks. During the experimental period the volunteers brushed their teeth with non-fluoridated dentifrice. After each stage, the percentage of surface microhardness change (%SMHC) and area of mineral loss (DeltaZ) were determined on enamel and the dental biofilm formed on the blocks was collected and analysed for F, P, Ca, Fe and alkali-soluble carbohydrates. The concentrations of F, Ca and Fe in enamel were also analysed after acid biopsies. RESULTS: There was a statistically significant increase in the P and Fe concentrations in the biofilms treated with ferrous sulphate (p<0.05), which was not observed for F, Ca and alkali-soluble carbohydrates. The group treated with ferrous sulphate had significantly lower %SMHC and DeltaZ when compared to control (p<0.05). CONCLUSIONS: These results showed that ferrous sulphate reduced the demineralization of enamel blocks and altered the ionic composition of the dental biofilm formed in situ.

Adult↗

PubMed2001

A comparative evaluation of three fluoride varnishes: an in-vitro study.

This study was conducted to compare the caries preventive efficacy of Fluoritop - SR; the first fluoride varnish manufactured in India with Fluor Protector and Bifluorid 12, the two commercially available fluoride varnishes which have to be imported from other countries and are cost prohibitive. The demineralization inhibitory effects and the antibacterial effects on Streptococcus mutans were studied (in vitro). Calcium and Phosphorus dissolutions were estimated as a measure of the demineralization inhibitory effect. Antibiotic sensitivity tests using the serial tube dilution method and disk diffusion method were used to evaluate the antibacterial effects of the fluoride varnishes. Of the three varnishes, Fluor Protector was seen to exhibit the highest demineralization inhibitory effect, while Fluoritop-SR was found to be comparable to Bifluorid 12 in its caries protective effects.

Analysis of Variance↗

PubMed1992

Identification of a resin-dentin hybrid layer in vital human dentin created in vivo: durable bonding to vital dentin.

The present study investigated the bond of 5% 4-methacryloxyethyl trimellitate anhydride in methyl methacrylate, initiated by partially oxidized tri-n-butyl borane in the presence of poly(methyl methacrylate) powder, to vital human dentin. In vivo dentinal substrates were pretreated for 10 or 30 seconds with an aqueous solution of 10% citric acid and 3% ferric chloride. Transmission electron microscopic examination of the bonded cross sections revealed the formation of a transitional, or "hybrid," layer of resin-reinforced dentin created by the impregnation, co-mingling and envelopment of collagen bundles, and encapsulation of hydroxylapatite crystals. The in vivo adhesion was assumed to be durable, because results of microscopic examinations were comparable to those of durable bonding of the same resin to extracted bovine dentin. Vital dentin exhibited greater resistance to demineralization by the acid solution than do extracted teeth. Carious extracted teeth were more easily dissolved in acid than were noncarious extracted teeth.

Acrylic Resins↗

PubMed2004

In vivo effect of a resin-modified glass ionomer cement on enamel demineralization around orthodontic brackets.

Because the risk of dental caries increases with the use of orthodontic appliances and its control cannot depend only on the patient's self-care, this study evaluated the effect of a glass ionomer cement on reducing enamel demineralization around orthodontic brackets. Fourteen orthodontic patients were randomly divided into 2 groups of 7; they received 23 brackets fitted to their premolars, bonded with either Concise (3M Dental Products, St Paul, Minn), a composite resin (control group), or Fuji Ortho LC (GC America, Chicago, Ill), a resin-modified glass ionomer cement (experimental group). The volunteers lived in a city that has fluoridated water, but they did not use fluoridated dentifrices during the study. After 30 days, the teeth were extracted and longitudinally sectioned; in the enamel around the brackets, demineralization was assessed by cross-sectional microhardness. The determinations were made at the bracket edge cementing limits, and at occlusal and cervical points 100 and 200 microm away from them. In all of these positions, indentations were made at depths from 10 to 90 microm from enamel surface. Analysis of variance showed statistically significant effects for position, material, depth, and their interactions (P<.05). The Tukey test showed that the glass ionomer cement was statistically more efficient than the control, reducing enamel demineralization in all analyses (P<.05). The use of glass ionomer cement for bonding can be encouraged because it decreases the development of caries around orthodontic brackets.

Acrylic Resins↗

PubMed2005

[Comparison of primary caries detection on smooth surface in the maxillary anterior teeth using QLF, digital photo and visual diagnosis].

PURPOSE: This study is to investigate the differences of primary caries detection on smooth surface in the maxillary anterior teeth using quantitative light-induced fluorescence(QLF),digital photo and visual examination. METHODS: Three hundreds of middle school students in Deyang city and Ziyang city were examined. Seventeen hundreds and thirty-two maxillary incisors and canines were included. After being cleaned and dried, the white spots (primary caries on smooth surface) were examined by QLF, digital camera, and visual examination. The difference among three methods was analyzed by Chi-square test using SPSS 11.5. RESULTS: In QLF examination, 24.08 percent of the examined teeth were found out having white spots. Results of the Chi-square test showed that QLF had a significantly higher capability(24.08%) on finding out the primary demineralized spots than digital camera(22.17%) and visual examination(20.61%). There was significant difference among the three diagnostic methods(P<0.05). CONCLUSION: The study suggested that QLF is a trustworthy, speedy, safe and noninvasive diagnosed method and was worthy extending and applying in the clinic.

Dental Caries↗

PubMed1991

Column-like structures of human dentin in carious and artificial lesions.

Serial sections of 36 human teeth with minor to medium-sized carious lesions, adequate sections from previous studies of artificial lesions adjacent to fillings of amalgam (AM), silicate cement (SI) and glass ionomer cement (GI) were studied by ordinary light microscopy and microradiography. Six artificial primary root lesions were included. In carious lesions, dentin columns were visible in the demineralization zone and partly also in the translucent/radiopaque zone. A typical feature of the artificial lesions adjacent to SI fillings was highly radiopaque columns alternating with radiolucent ones. In the GI group such columns were seen at the cavity wall and the advancing front of the outer lesion. In the AM group dark columns were unveiled as pegs in the latter localization. The findings led to the assumption that the dark columns of intact dentin are preferred pathways of acid diffusion in artificial and, possibly, carious lesions. Increased radiopacity of columns in the SI and GI groups is explained by continued exposure of the tooth surface to fluoride dissolved from these fluoride-rich filling materials.

Dental Amalgam↗

PubMedDate not supplied

Efficacy of fluoride toothpaste in preventing demineralization of smooth dentin surfaces and narrow grooves in situ under frequent exposures to sucrose or bananas.

The use of models simulating fissures allows studying demineralization at sites that are most prone to caries in vivo. In practice, most in situ models use flat surfaces. Our objectives were: (1) to compare the demineralizing potential of sucrose solution with that of bananas and (2) to study the effect of fluoride toothpaste on demineralization in situ in an easily accessible site and a plaque stagnation site. Four volunteers wore bovine dentin specimens with narrow grooves and a smooth surface for two 1-week in situ periods, with eight 1-min sugar exposures daily: either by a rinse with 10% sucrose, or by consumption of a piece of banana. Twice daily, the appliance was dipped in toothpaste slurry of a control (fluoride-free) toothpaste at one side and a fluoride toothpaste at the contralateral side. Demineralization was assessed by transversal microradiography. We found no difference in dentin demineralization after frequent exposure to either sucrose solution or bananas. Fluoride toothpaste effectively protected dentin only at the smooth surface. In the grooves, fluoride affected the demineralization pattern; it drove lesions towards the bottom of the groove. We conclude that assessing only smooth surfaces in intraoral tests might lead to underestimated food cariogenicity and to overestimated efficacy of fluoride-containing toothpaste.

Adult↗

PubMed1994

Tensile properties of mineralized and demineralized human and bovine dentin.

The relative contribution of the matrix of dentin to the physical properties of dentin is unknown but thought to be small. The objective of this study was to test the hypothesis that the demineralized matrix of dentin contributes little to the strength of dentin by measuring and comparing the ultimate tensile strength and modulus of elasticity of mineralized and demineralized dentin. Small slabs (4 x 0.5 x 0.5 mm) of bovine and human dentin were tested in a microtensile testing device in vitro. Human coronal mineralized dentin gave a mean ultimate tensile strength (UTS) of 104 MPa. Bovine incisor coronal dentin exhibited a UTS of 91 MPa, and bovine root dentin failed at 129 MPa. The modulus of elasticity of mineralized bovine and human dentin varied from 13 to 15 MPa. When dentin specimens were demineralized in EDTA, the UTS and modulus of elasticity fell to 26-32 MPa and 0.25 GPa, respectively, depending on dentin species. The results indicate that collagen contributes about 30% of the UTS of mineralized dentin, which is higher than was expected.

Animals↗

PubMed1995

Effects on demineralization of enamel by fluoridated sucrose: a pilot study in an in situ caries model.

Blocks of human enamel, placed in removable partial dentures, were allowed to acquire natural plaque for seven days and were exposed extra-orally to a cariogenic challenge by repeated periods in a fluoride-sucrose solution. As a control, enamel blocks were exposed extra-orally to a sucrose solution. After two weeks of cariogenic challenge, the blocks were examined for mineral loss by quantitative microradiography on thin sections of the enamel. The results from six subjects showed that no significant effect on demineralization could be detected by the addition of fluoride corresponding to fluoride/sugar content of 1 mg/kg, 5 mg/kg, or 10 mg/kg (dry weight). One subject did not develop lesions at all, either with fluoride-sucrose or with sucrose exposure alone.

Analysis of Variance↗

PubMed2004

Effect of plaque accumulation and salivary factors on enamel demineralization and plaque composition in situ.

This study evaluated the effect of some plaque and salivary factors on caries progression in situ. The salivary secretion rate, buffering capacity and mutans streptococci counts from 13 volunteers were determined. For three distinct periods of time, 4, 7 and 10 days, each of them wore a palatal appliance containing 4 bovine enamel blocks. They used a non-fluoridated dentifrice during the experiment and a 20% sucrose solution was dripped onto the blocks 10 times a day. Mutans streptococci (MS), calcium (Ca), and insoluble polysaccharide (IP) were quantified in the dental plaque formed on the enamel blocks, after each period. Enamel demineralization was assessed by surface microhardness, and the percentage of surface microhardness change (%SMC) in relation to the baseline values was calculated. Enamel demineralization occurred after each period of plaque accumulation (p < 0.05), and the %SMC increased with time (from 13.8 to 48.3%). The concentrations of Ca and IP in plaque were not statistically different among the experimental times, but significant correlations were found between these concentrations and %SMC. Neither the salivary factors assessed initially nor mutans streptococci in plaque presented statistically significant correlations to %SMC. The results suggest that enamel demineralization is time-dependent and is more related to the composition of the biofilm formed than to the salivary factors studied.

Adult↗

PubMed1992

The influence of various amphiphilic phosphates on in vitro caries lesion formation in human dental enamel.

Some newly designed surface-active phosphates were investigated with respect to their capacity to inhibit caries lesion formation in vitro. On the labial or buccal surfaces of sound human third molars, windows were prepared for investigation. One half of each window was treated with the test compound at pH values of 7.5, 5.5, or 3.5. The other half served as a control. Both halves were demineralized and the generated caries lesions in both parts were compared by means of quantitative microradiography. Mono-, bis- and trisphosphates differed only marginally in their effect on the demineralization. The compounds diminished the demineralization down to 30% of that of untreated enamel. Per molecule at least one long alkyl chain (more than 12 C atoms) was required for achieving decreased demineralization, indicating the importance of a low surface tension. The results suggest that some of the tested compounds have promising properties for their use as anticaries agents, especially when applied in combination with fluoride.

Dental Caries↗

PubMedDate not supplied

In vitro studies of the effect of a dental explorer on the formation of an artificial carious lesion.

This project deals with in vitro mechanical damage of early carious lesion (enamel lesion) in artificial U-shaped grooves caused by a sharp dental explorer. The lesions were formed in enamel grooves in 3 percent by weight cellulose solution in 0.1 M lactic acid containing 1.08 M KH2PO4 and 1.8 mM CaCl2 buffer to pH 4.28 after two weeks of demineralization. A relatively intact surface layer was observed in all the grooves. Three demineralized grooves were probed with different forces 100 g, 300 g and 500 g. The traumatic damage was assessed by using microradiography. There was no damaging effect in the sound enamel grooves probed with a sharp explorer up to a force of 500 g. Breakdown of the surface layer was assessed in all probed demineralized enamel grooves, converting the white spot lesion with apparently a sound surface layer into a cavity. Explorer penetration into the lesion was found to be strongly related to the force applied. The use of a sharp dental explorer should be reconsidered in examination and diagnosis of early carious lesions in pits and fissures and an alternative technique should be sought.

Dental Caries↗

PubMed2001

Effect of saliva substitutes on mineral content of demineralized and sound dental enamel.

The aim of this in vitro study was to evaluate the effects of commercially available saliva substitutes on the mineral content of pre-demineralized and sound enamel. From 56 bovine incisors 224 enamel specimens were prepared and hand-polished. The specimens were partially covered with nail varnish (control of sound enamel). In group 1, 112 samples were demineralized (18 days; 37 degrees C; pH 5.0) and a portion of the demineralized area was likewise covered with nail varnish. Subsequently, 16 specimens were exposed (14 days; 37 degrees C) to 10 ml of each of several different saliva substitutes (Artisial; Glandosane; Oralube; Saliva medac), or mouthwash solutions (Biotène; Meridol), respectively. Non-carbonated, fluoride-containing mineral water (Eptinger) was used as control. In group 2, the 112 sound enamel specimens were immersed directly in the solutions (without a demineralization period). After immersion, the specimens were cut perpendicular to the surface, and slabs (110 microns) were ground. Contact microradiographs were obtained and studied with a digital image-analyzing system. A dedicated software (TMR 1.24) was used to calculate the mineral content. Sound enamel (group 2) was significantly demineralized after immersion in Biotène and Glandosane (P < 0.001; Kruskal-Wallis). In group 1, mineral loss after storage in Biotène and Glandosane was significantly increased (P < 0.001), compared with the mineral content after demineralization. All other solutions revealed a significant mineral gain (P < 0.01; Wilcoxon), with the most pronounced effects after use of Oralube and mineral water (both containing calcium, phosphates, and fluorides). Therefore, administration of products similar to the last named can be recommended for dentate patients with salivary gland hypofunction.

Animals↗

PubMed2002

A comparison between zinc polycarboxylate and glass ionomer cement in the orthodontic band cementation.

Fixed orthodontic appliances have been held responsible for demineralization and caries since the time they were first introduced. Zinc polycarboxylate and glass ionomer cements are the primary materials used in band cementing. In this study, we evaluated the re-cementing frequencies, enamel demineralization and the degree of cement remains of the bands cemented with glass ionomer and zinc polycarboxylate cements. We have concluded that given the retentive properties and enamel decalcification degree, the glass ionomer cements are to be preferred by the orthodontist.

Cementation↗

PubMed2005

Influences of bracket bonding on mutans streptococcus in plaque detected by real time fluorescence-quantitative polymerase chain reaction.

BACKGROUND: Enamel demineralization occurs frequently during orthodontic treatment. In this study, we evaluated the changes of the density of mutans streptococcus (MS) in plaque after bracket bonding and using fluoride adhesive on maxillary incisors by real time fluorescence-quantitative polymerase chain reaction (RT-FQ PCR). METHODS: The study was designed as a self-paired test. Brackets were bonded with fluoride adhesive on the left side, while non-fluoride adhesive on the right side for each patient. Plaque samples were taken from the surfaces around the brackets of four maxillary incisors before brackets bonding and after the bonding 4 weeks later. The amount of MS was measured by RT-FQ PCR. The data obtained were analyzed statistically using the SPSS 11.5 version and the alpha level was set at 0.05 (2-tailed). RESULTS: The amount of MS in plaque increased significantly after bracket bonding (P < 0.01), whereas no significant differences were observed among four maxillary incisors both before and after brackets bonding (P > 0.05), and among the incisors using and not using fluoride adhesive (P > 0.05). CONCLUSIONS: The increase of the density of MS in plaque after bracket bonding is one of the etiological factors for enamel demineralization in orthodontic patients. The result of this study did not support what we observed clinically that the incidence of enamel demineralization for lateral incisors was higher than that for central incisors. Using fluoride adhesive for bonding did not affect the amount of MS in plaque in our study. Further study is needed.

Adhesives↗

PubMed2000

Effects of fluoride- and chlorhexidine-containing varnishes on plaque composition and on demineralization of dentinal grooves in situ.

The aim of the study was to compare the effects of Cervitec, containing 1% chlorhexidine (CHX) and 1% thymol, Fluor Protector, containing 0.1% fluoride, their 1:1 mixture, and a placebo varnish on the percentage of mutans streptococci and lactobacilli in plaque and on the underlying dentin demineralization, as assessed by microradiography. Bovine dentine discs, fitted with three parallel grooves, received one of the varnish treatments into the first groove and on the adjacent part of the dentin surface. Volunteers (n = 23) wore the discs fixed to their partial dentures for four consecutive 3 wk periods. Microbiological analysis of plaque accumulated in the grooves showed no difference between groups. Fluoride varnishes (Fluor Protector and mixed varnish) had a significantly larger inhibitory effect on mineral loss in the treated groove than Cervitec or placebo. All treatment varnishes had more pronounced effect in panelists (n = 14) with higher degree of demineralization (mineral loss in placebo group > or = 1,200 vol% x microm). In these panelists, CHX-containing varnishes showed an inhibitory effect on demineralization in all grooves, also in the two non-varnished grooves. As fluoride varnishes had the largest localized effect on demineralization, and CHX varnishes were showing a peripheral effect, a combined treatment could be the preferred method to obtain an optimal caries preventive effect in caries-prone individuals.

Aged↗

PubMed2000

Enamel demineralization under driving forces found in dental plaque fluid.

The present study was carried out to examine the kinetics of enamel demineralization in vitro under driving forces for demineralization (i.e., the degree of saturation with respect to enamel, DS(En)) similar to those found in dental plaque fluid. Thin sections of human enamel were exposed at 25 degrees C to lactic acid solutions with DS(En) values (DS(En) = [(Ca2+)5(OH-)(PO4(3-))3/K(En)]1/9; K(En) = 5.5 x 10(-55)) ranging from 0.28 to 0.79. Lesion development was monitored by quantitative microradiography. Enamel mineral loss in solutions with DS(En) values of 0.28, 0.32 and 0.36 was first detected after 3, 3, and 7 wk of continuous exposure, respectively. Consistent with previous findings, subsurface demineralization was observed and rates of mineral loss increased significantly with decreasing DS(En) values. However, no mineral loss was observed in sections of enamel exposed to solutions with DS(En) values of 0.41 and 0.79, even after 11 months. These results suggest that (outer) enamel mineral behaves as a mineral phase that is less soluble than that dictated by the solubility product constant (K(En)) used in this study. Furthermore, these results indicate that the kinetics and general features of the demineralization process are maintained over a wide range of DS(En) values, including conditions that better reflect those found in the oral cavity. These findings are particularly relevant to the assessment of the cariogenic potential of dental plaque fluids.

Cariogenic Agents↗