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At least 667 records · Page 37Linked to original sources

PubMed2007

Infiltration/evaporation-induced shrinkage of demineralized dentin by solvated model adhesives.

During dentin bonding, solvated adhesive comonomers are applied to water-saturated decalcified dentin matrices. When alcohol-solvated hydrophilic or hydrophobic methacrylate monomers are applied, they chemically remove water and cause matrix shrinkage during comonomer infiltration. Evaporation of solvent induces further shrinkage. The purpose of this work was to compare the shrinkage of water-saturated dentin matrices infiltrated with ethanol- or methanol-solvated 2-hydroxyethyl methacrylate (HEMA), 2,2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl] propane (BisGMA), or triethyleneglycol dimethacrylate (TEGDMA) at 90/10, 70/30, 50/50, and 30/70 mass fraction % alcohol/monomer before and after evaporation of alcohol. Thin (ca 0.2 mm) disks of human mid-coronal dentin were demineralized and placed in a well beneath the contact probe of a linear variable differential transformer (LVDT). The height of the matrix was measured before and after random application of one of the twelve alcohol/monomer mixtures. Matrix height was measured during infiltration and during solvent evaporation. Between trials, residual monomer was extracted using ethanol. These studies were repeated on specimens in which 100% alcohol was used to substitute for water in the matrix. Both studies revealed that matrices shrink 30-50% but that pretreatment of matrices with alcohol prevents BisGMA phase separations from occurring. Wet bonding with ethanol instead of water permits infiltration of relatively hydrophobic alcohol/monomers.

Adhesives↗

PubMed1997

In vivo detection of calcium from dicalcium phosphate dihydrate dentifrices in demineralized human enamel and plaque.

A series of studies was conducted to clarify the role of DCPD in improving the effects of fluoride in the mouth. We performed plaque fluid studies to see if the use of DCPD dentifrices increases the levels of free Ca2+ ions and the DSenamel in plaque fluid. The results of these studies showed that plaque fluid was undersaturated with respect to DCPD; therefore, DCPD would dissolve in the mouth. The Ca2+ activity in plaque fluid measured 12 hours post-treatment was significantly elevated with the use of DCPD dentifrices in comparison with silica dentifrices. The use of DCPD dentifrices also increased the DSenamel of plaque fluid in comparison with a NaF/silica dentifrice. To determine whether Ca from DCPD could be detected in demineralized enamel and whole plaque after in vivo usage of a DCPD/ fluoride dentifrice, we conducted a 44Ca labeling study. Secondary Ion Mass Spectrometry (SIMS) was used to detect and measure changes in 44Ca levels in enamel before and after 6 days of in vivo treatment with a 44DCPD/fluoride dentifrice. The results showed that 44Ca from DCPD was incorporated into enamel and detected in plaque 18 hours post-treatment. The findings from these studies show that brushing with a DCPD dentifrice introduces additional, exogenous Ca into the oral environment, which fosters improved remineralization of teeth in combination with fluoride.

Calcium↗

PubMed1988

Intra-oral retention of fluoride by bovine enamel from amine fluoride toothpaste and 0.4% amine fluoride liquid application.

The purpose of this study was to compare in vivo fluoride accumulation in enamel and in enamel lesions from a single topical fluoride application and daily toothbrushing with a fluoride dentifrice. Amine fluoride preparations were used for both products. Intra-oral appliances with bovine enamel specimens were worn by volunteers during a period of seven weeks. After this period, the specimens were analyzed for fluoride uptake and change in demineralization susceptibility. The results demonstrated that lesions had a high fluoride uptake capacity. Fluoride content values increased by 25-30 micrograms/cm2 during a single topical application, as compared with 10-15 micrograms/cm2 during seven weeks of toothbrushing. About half the fluoride acquired as a result of topical treatment was lost during subsequent exposure to the oral fluids when no further fluoride supplementation was given. The uptake of fluoride by sound enamel was comparatively small, regardless of the use of fluoride dentifrice or application. The presence of mature plaque at the time of fluoride application did not affect the amounts of fluoride delivered. Acid susceptibility tests showed that the enamel solubility exhibited a negative correlation with fluoride content of the specimens.

Amines↗

PubMed1997

A clinical and microbiological study of deep carious lesions during stepwise excavation using long treatment intervals.

Concern about the survival of microorganisms in deep carious lesions may often lead to unnecessary exposure of the pulp during final excavation. There are reasons, therefore, to initiate systematic studies on the alternative procedure known as stepwise excavation. Clinical evaluation of stepwise excavation was performed on 31 deep carious lesions considered to result in pulp perforation by traditional excavation. This study examines the clinical and microbiological alterations during the final excavation performed during long intervals (6-12 months) after the initial treatment that included peripheral dentine excavation and removal of the central cariogenic biomass and the superficial necrotic dentine. The dentine colour and consistency were assessed by means of standardized scales before application of a Ca(OH)2 compound and a temporary sealing for 6-12 months. Reassessments were performed before the after final excavation. Microbiological dentine samples were obtained in 19 randomly selected lesions by a sterile bur, transferred to and diluted in reduced transport fluid, and plated on tryptic soy agar. After anaerobic incubation at 37 degrees C for 7 days, total colony-forming units per millilitre were counted from (1) peripheral excavated and hard dentine (control), (2) central demineralized dentine before and final excavation, and (3) central dentine after the final excavation. Six samples of central demineralized dentine were without any cultivable flora increasing to 9 samples after the final excavation. The clinical dentine changes occurring during stepwise excavation were characterized by enhanced hardness of the dentine which was associated with a marked reduction in bacterial growth after the final excavation. Despite the presence of bacteria in the excavated dentine none of the carious lesions resulted in pulp perforation, suggesting that the initial removal of the cariogenic biomass appears to be essential for control of caries progression. Stepwise excavation is not only an appropriate treatment of deep carious lesions but is also considered a suitable model for microbiological studies to determine the bacteria persisting in clinically excavated lesions.

Anaerobiosis↗

PubMed1997

Effectiveness of calcium lactate added to food in reducing intraoral demineralization of enamel.

Following the demonstration that rinses with solutions of soluble calcium salts reduced sucrose-induced demineralization, a study was undertaken to determine whether a similar effect could be obtained by the supplementation of a solid food with calcium lactate (CL). Subjects wore palatal appliances containing blocks of bovine enamel that were coated with Streptococcus mutans IB 1600 and ate 5-gram portions of cookies made with defined levels of CL. Determinations were made of changes in iodide penetrability (delta Ip) of the enamel, as well as the pH, calcium and inorganic phosphate of the streptococcal plaque. CL at 3.2% (w/w) reduced delta Ip from 12.9 +/- 1.7 to 6.1 +/- 0.9 units, i.e. by 52.7%. Plaque pH was not affected. Demineralization was reduced progressively with increasing concentrations of added CL, and CL was most effective with increasingly sweet cookies. Plaque contained 32.4 +/- 6.0 and 17.1 +/- 4.2 mM calcium after 1 and 5 min, respectively. Calculations showed that the plaque was saturated with respect to enamel during the first 5-10 minutes after food ingestion, in spite of the progressive drop in plaque pH. In conclusion, the present study demonstrated the reduction of the cariogenic potential of solid food by relatively low concentrations of CL. The effect appeared to be related to the ability of the food to maintain high levels of calcium in the streptococcal plaque during the period of active acidogenesis.

Acids↗

PubMed1987

Comparison of the effects of fluoride and the ionophore nigericin on acid production by Streptococcus mutans and the resultant in vitro enamel demineralization.

In an in vitro demineralization experiment with a plaque of S. mutans C180-2 over enamel, the effect of 0.5 mmol fluoride/L was compared with that of 10 nmol nigericin/L. Since the effects of both substances on the acid production in a dense cell suspension were of the same magnitude, and since nigericin did not affect the enamel solubility, the present demineralization experiment may differentiate between the effect of fluoride on bacterial metabolism alone and the combined effect of fluoride on both the bacterial metabolism and enamel solubility. In our experiments, the effect on bacterial metabolism accounted for 75% of the caries-inhibiting effect of fluoride. Microradiographic data showed subsurface lesions in the control and nigericin group and a slight surface-softening in the fluoride group. In addition, the effects of fluoride and nigericin on the cellular internal pH during glycolysis were studied. Analysis of these data suggested that glycolysis was inhibited when the intracellular pH reached about pH 5.2, which supports the view that acidification of the cell cytoplasm is a mechanism by which fluoride inhibits glycolysis.

Acids↗

PubMed1996

A 3-year clinical study of tunnel restorations.

Tunnel restorations (n = 161) performed by 4 dentists were evaluated after a mean of 35 months in situ. Demineralized enamel was to be spared during preparation. The preparations were filled with a cermet glass ionomer (polyalkenoate) cement. Evaluation was carried out using clinical and radiographical criteria. During the observation period, approximately 16% of the restorations were replaced due to caries in dentin and 14% due to marginal ridge fracture. Cavitation in the approximal surface and/or increased radiolucency of the approximal enamel were observed in 34% of the remaining tunnel-restored teeth. A significantly higher frequency of failures were registered when treating patients with a high caries activity, where the initial lesion was large, and where the restoration did not reach the approximal surface.

Adolescent↗

PubMedDate not supplied

Caries experience and cariogenic markers in HIV-positive children and their siblings.

The purpose of this cross-sectional, masked study was to compare the oral status of perinatally HIV-infected children with their uninfected siblings living in the same environment. A secondary purpose was to compare HIV-positive children for differences in oral health with respect to disease advancement. One hundred forty-seven children were examined in their homes and meeting places, using NIH criteria for caries diagnosis. Significant differences were found in the number of caries-free children (P < 0.05), past caries experience (P < 0.003), subsurface demineralizations (P < 0.0001), and caries-related bacteria (P < 0.05). However, differences in caries prevalence were not found in the 3- to 6-year-old subgroup. Caries prevalence (P < 0.001) and levels of caries-related flora in saliva were correlated to years since diagnosis (mutans streptococci P < 0.008, lactobacilli P < 0.02). Children with a more advanced disease stage had significantly more caries (P < 0.02). Among the HIV-infected children, the frequency of carbohydrate intake was clearly correlated to caries (P < 0.003) and to lactobacilli levels (P < 0.0001). It is concluded that children with perinatally acquired HIV are at greater risk for caries than their siblings, more so with advancing disease.

Adolescent↗

PubMed1995

Effect of an antibacterial varnish on mutans streptococci in plaque from enamel adjacent to orthodontic appliances.

The effect of an antibacterial varnish (Cervitec) on the levels of mutans streptococci in plaque adjacent to bonded orthodontic brackets was evaluated in 18 children using a split-mouth technique with a placebo varnish control. The test varnish contained 1% chlorhexidine and 1% thymol as active ingredients. Both varnishes were applied on four occasions during a 3-month period, and plaque was subsequently collected between 1 week and 6 months after the onset of treatment. All teeth involved in the study were carefully examined and clinically assessed for enamel demineralization prior to onset of the fixed appliances and immediately after debonding. The results showed a more frequent growth of mutans streptococci in the dental plaque collected from placebo-treated quadrants as compared with the test quadrants on all sampling occasions. The proportion of mutans streptococci within the plaque microflora was significantly (p < 0.05-0.01) lower on the test sides than on the opposite sides at the 1-week and 1-month examinations. The incidence of incipient enamel lesions around the brackets and along the gingival margin was generally low, and no differences were found between the test and placebo varnish treated quandrants at the time of debonding. The results suggest that mutans streptococci in plaque from orthodontic patients can be suppressed effectively by topical applications of an antibacterial varnish.

Adolescent↗

PubMed2001

Current concept on the anticaries fluoride mechanism of the action.

The paper discusses a possible new concept of the role of fluoride and its mechanism of action in caries prevention. In the past fluoride inhibition of caries was ascribed to reduced solubility due to incorporation of fluoride (F) into the enamel minerals (firmly bound fluoride or fluorapatite). Based on the new findings, it appears that fluoride, either released into or present in the fluid phase bathing the hard tissue, is more important for the reduction of caries development and progression. There is convincing evidence that fluoride has a major effect on demineralization and remineralization of dental hard tissue and that it interferes with acid production from cariogenic bacteria. The provision of dissolved fluoride is the key to successful therapy. The source of this fluoride could either be fluorapatite or calcium fluoride (CaF2) (like) precipitates, which are formed on the enamel and in the plaque after application of topical fluoride. The precipitates of calcium fluoride do not dissolve quickly as was initially believed. Calcium fluoride coating at neutral pH by pellicle proteins and phosphate is the main reason for this. The dissolution of the fluoride from calcium fluoride is pH dependent. At lower pH, the coating is lost and an increased dissolution rate of calcium fluoride occurs. The CaF2, therefore, act as an efficient source of free fluoride ions during the cariogenic challenge. These are subsequently incorporated into the enamel as hydroxyfluorapatite or fluorapatite.

Calcium Fluoride↗

PubMed2000

In vitro inhibition of enamel demineralization by a polymerizable amphiphilic film.

An amphiphilic coating is configured as a substantive film that has a tendency for an in-plane two-dimensional polymerization. This coating is hypothesized to protect enamel from in vitro acid decalcification, assessed through the following artificial caries model. Three regions on labial enamel of eight bovine incisors were treated with an acid resistant varnish (A), the amphiphilic coating (B), or left undisturbed (C), and the teeth were immersed for 3 wk in lactic acid gel. Mineral loss (deltaZ-value) was determined by a cross-sectional microhardness technique. deltaZ-values (mean +/- SD; volume percent mineral-microm) were: -4 +/- 24 (A), 29 +/- 69 (B), and 7,372 +/- 1,766 (C). deltaZ-value of the uncoated enamel (C) was significantly different from the other groups. Scanning electron microscopy showed enamel etched pattern from citric acid, and the coating firmly attached on enamel surface. This amphiphilic coating can inhibit enamel decalcification under the present experimental condition.

Acrylates↗

PubMed1994

Bacterial colonization and degradation of demineralized dentin matrix in situ.

Lesion formation in dentin involves demineralization followed by degradation of the exposed organic matrix. Proteinases from microorganisms present in the dentin are believed to play an important role in the breakdown of the dentinal collagen. In this study, the microflora colonizing decalcified dentin matrix, placed in situ, was identified. The gelatinolytic activity of the isolated strains was assessed and related to the degradation of the dentin matrix. The predominant species found were Streptococcus mitis. Peptostreptococcus productus, Lactobacillus casei, Propionibacterium species and Veillonella parvula. Marked interindividual variation in the composition of the microflora was observed. The microflora possessed gelatinolytic activity, although no correlation was found with the severity of dentin matrix degradation. The chemically determined loss of collagen varied between 0 and 67 wt% per participant and corresponded with the extent of collagen degradation observed by transmission electron microscopy.

Animals↗

PubMed1997

Fluoride level in saliva after bonding orthodontic brackets with a fluoride containing adhesive.

The fluoride level in saliva is considered an important parameter in caries prevention. Elevation of the salivary fluoride level by a fluoride-releasing orthodontic bonding adhesive would most likely be beneficial in the prevention of enamel caries. In this study, the fluoride level in saliva was measured after bonding brackets with a visible light-curing adhesive containing fluoride (12.4 wt% total F). The fluoride released from the adhesive has been shown in a previous study to inhibit demineralization adjacent to orthodontic brackets in vivo. Twenty-four patients each had 20 brackets bonded and saliva samples taken before bonding (t = 0) and after 1, 3, and 6 months. The participants were requested to brush daily with a fluoride toothpaste during the study period. The saliva fluoride analysis was done with the microdiffusion method. The analysis of the saliva showed fluoride levels (+/- SD) of 0.011 +/- 0.007, 0.011 +/- 0.009, 0.0011 +/- 0.007, and 0.012 +/- 0.008 ppm at t = 0, 1, 3, and 6 months, respectively. There was no significant difference at the 5% level. The study indicated indirectly that the caries inhibiting effect of the orthodontic adhesive shown previously was most likely due to a localized fluoridation of the cariogenic environment rather than to an elevation of the fluoride level in saliva.

Adhesives↗

PubMed1992

Effects of fluoride and methanehydroxydiphosphate on enamel and on dentine demineralization.

The aim of this article was to investigate the effects of methanehydroxydiphosphonate (MHDP) and fluoride (F) separately and combined, on the demineralization process in enamel and in dentine under constant composition conditions. The demineralization was carried out in solutions containing 3 mM calcium, 3 mM phosphate, pH = 5.0, and either 6 microM MHDP, 12 microM F or 6 microM MHDP and 12 microM F. After demineralization periods (t) between 24 and 140 h, the lesion depth l and the mineral loss delta Z were measured by transverse microradiography of the enamel and dentine specimens. The amount of mineral lost during demineralization averaged over the lesion depth, R = delta Z/l, was calculated. R approximately 17 vol% for both enamel and dentine, both delta Z and l being greater for dentine than for enamel by approximately the same factor. The results show that under the same conditions dentine is attacked much more strongly than enamel. The lesion progress with time is quite different for the two tissues: in enamel the lesion depth progresses als l3 = alpha t + beta, in dentine as l2 = alpha't + beta'. The slopes alpha and alpha' decrease in the order MHDP > F > MHDP+F. In enamel the combined inhibitor effect is only slightly larger than the effect of F alone; in dentine the inhibiting effects of F and MHDP are approximately additive. The inhibitor interactions can be described by the Langmuir adsorption theory.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗

PubMed2003

Incorporation of casein phosphopeptide-amorphous calcium phosphate into a glass-ionomer cement.

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) nanocomplexes have been shown to prevent demineralization and promote remineralization of enamel subsurface lesions in animal and in situ caries models. The aim of this study was to determine the effect of incorporating CPP-ACP into a self-cured glass-ionomer cement (GIC). Incorporation of 1.56% w/w CPP-ACP into the GIC significantly increased microtensile bond strength (33%) and compressive strength (23%) and significantly enhanced the release of calcium, phosphate, and fluoride ions at neutral and acidic pH. MALDI mass spectrometry also showed casein phosphopeptides from the CPP-ACP nanocomplexes to be released. The release of CPP-ACP and fluoride from the CPP-ACP-containing GIC was associated with enhanced protection of the adjacent dentin during acid challenge in vitro.

Analysis of Variance↗

PubMed2004

In situ effect of frequent sucrose exposure on enamel demineralization and on plaque composition after APF application and F dentifrice use.

Since the effect of the combination of methods of fluoride use on enamel demineralization and on plaque composition is not clearly established, this study examined the effect of the combination of acidulated phosphate fluoride (APF) application and F dentifrice on enamel demineralization and on plaque composition. In this crossover study, 16 volunteers, wearing a palatal appliance containing bovine enamel blocks, were subjected to 4 treatment groups: non-fluoridated dentifrice (PD), FD, APF+PD, and APF+FD. The APF was applied to the enamel before the 14-day experimental period. During the experimental period, test dentifrices were applied 3x/day, and a 20% sucrose solution was applied 4x and 8x/day by being dripped on the blocks. Although APF application was able either to increase F concentration in plaque or to reduce the % of mutans streptococci, its combination with F dentifrice use neither reduced enamel mineral loss nor changed any other measured plaque variable with respect to the FD group alone.

Acidulated Phosphate Fluoride↗

PubMed1996

A clinical evaluation of the effectiveness of a fluoride-releasing visible light-activated bonding system to reduce demineralization around orthodontic brackets.

The presence of decalcification (white spots) after the removal of orthodontic appliances still remains a problem. A method to deliver fluoride to the area beneath and around the bonded attachments, independent of patient compliance, could be very helpful. Therefore special attention is being currently directed to the so-called "fluoride releasing bonding adhesives." A clinical trial was carried out to compare the effect of a visible light-cured fluoride-releasing (F-releasing) material with a chemically cured nonfluoride resin on white spot formation during fixed orthodontic therapy. Fifty patients entered the trial, and 762 brackets were bonded in a crossover design. Intraoral slides were taken before and after treatment and were evaluated for white spot formation. Statistical data analysis was carried out by means of a chi-square test. The results of this clinical study indicate that there was no significant difference between the decalcification rates for both types of adhesives. When the appearance of white spots was evaluated in an overall manner, there was significantly more upper than lower decalcification.

Acid Etching, Dental↗

PubMed2000

The matrix metalloproteinase gelatinase A in human dentine.

A dentine protein extraction protocol was modified in order to identify matrix metalloproteinase gelatinolytic activities in the non-mineralized and mineralized phases of human dentine. Dentine proteins from 24 individual permanent molars from patients aged 15-73 years were sequentially extracted, first with guanidinium chloride (G1 extract), then EDTA (E extract), and after this demineralization step, again by guanidinium chloride (G2 extract) to dissociate collagen-associated proteins. Extracts were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and the gels were processed by Western blotting and zymography to detect gelatinolytic activities. Active and latent forms of gelatinase A were identified in the non-mineralized dentine fraction (G1 extract) of 58% of the teeth. Other gelatinolytic species were also detected by zymography with apparent M(r) of 92, 54 and 30 kDa. Although gelatinase A was detected in the G1 extracts of teeth from all ages, indicating more recent synthesis and remodelling of the predentine, gelatinase A was never detected in any E extract or in the G2 extracts of patients older than 41 years. The presence of the active form of gelatinase A in mineralized human dentine implicates this enzyme in dentine mineralization.

Adolescent↗