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At least 469 records · Page 26Linked to original sources
PubMed1998

Dentine hypersensitivity: the effects of brushing desensitizing toothpastes, their solid and liquid phases, and detergents on dentine and acrylic: studies in vitro.

Dentine exhibiting symptoms of dentine hypersensitivity has tubules open at the dentine surface and patent to the pulp. The mechanisms whereby dentinal tubules are exposed is ill understood but probably involves a variety of abrasive and/or erosive agents. This study in vitro examined the quantitative and qualitative effects of toothpastes, their solid and liquid phases and detergents on dentine and acrylic. Abrasion of dentine and acrylic were measured by surfometry. Morphological changes to dentine were assessed by scanning electron microscopy. Abrasion of dentine and acrylic by toothpastes increased with increasing brushstrokes with marked differences in the extent of abrasion between different pastes. Brushing dentine with water or detergents produced progressive abrasion but which appeared to plateau around 2 microm loss. Water and detergents produced minimal effects on acrylic. At 5000 strokes dentine abrasion by solid phases was less than the parent toothpastes but the ranking order of abrasivity was the same as the parent toothpastes. Loss of dentine produced by liquid phases was minimal and in the order of 1-2 microm. Observationally, all toothpastes removed at least the dentine smear layer to expose many tubules; with one desensitizing product leaving a particulate deposit occluding most tubules. The solid phases of the toothpaste produced identical morphological changes to the parent paste. The liquid phases and detergents all exposed dentinal tubules by 5000 strokes. Water had little or no effect on the dentine smear layer. It is concluded that toothpastes, solid phase, liquid phase and detergents have the potential to abrade or erode dentine to a variable degree and result in tubule exposure. The effects of the liquid phases and detergents appear limited to the removal of the smear layer. Such detrimental effects seen in vitro could have relevance to the aetiology and management of dentine hypersensitivity. Toothpaste formulations which despite exposing tubules have ingredients capable of occluding tubules may be an area of development for such products.

Acrylic Resins↗
PubMed1996

Permeability, morphologic and temperature changes of canal dentine walls induced by Nd: YAG, CO2 and argon lasers.

The permeability, temperature and morphologic changes of the wall of the root canal induced by Nd:YAG, CO2 and argon lasers were studied. The changes were evaluated according to the presence or absence of a smear layer. Root canals of 140 human single-rooted teeth were enlarged using a step-back technique. Permeability was evaluated by the extent of methylene blue dye penetration into the tubules. Temperature changes were measured using a thermovision system, and morphological changes were evaluated by scanning electron microscopy. Laser energy was delivered into the canal by means of a flexible optical fibre or metal tip. There were statistically significant differences in permeability between lased groups with and without a smear layer in the cervical third of the root canal following lasing. In the middle third of the root canal, all three laser types induced permeability increases in groups with a smear layer. In the apical third, statistically significantly decreases in permeability were observed among CO2 laser and Nd:YAG compared with control group (P < 0.01). Rises in temperature ranged from a minimum of +10.1 degrees C (CO2 laser) to a maximum of +54.8 degrees C (argon laser). All three laser devices appeared capable of producing a glazed-like surface and craters.

Analysis of Variance↗
PubMed2007

Evaluation of dentin permeability after light activated internal dental bleaching.

The aim of this in vitro study was to assess quantitatively the dentin permeability of human teeth after intracoronal bleaching therapy with 35% hydrogen peroxide activated by LEDs, halogen lamp or using the walking bleach technique. Forty human maxillary central incisors had standard access cavities performed and the cervical thirds of the canals were prepared with Gates-Glidden drills up to a size 130. Roots were resected between the coronal and middle thirds and the apical portions were discarded. A glass ionomer, 2 mm thick cervical plug was placed inside the canal, at the cement-enamel junction level. Group I received 35% hydrogen peroxide gel activated by LEDs. Group II was submitted to 35% hydrogen peroxide gel activated by halogen lamp. Group III received 35% hydrogen peroxide gel and the walking bleach technique was followed. Group IV (control) received a dry cotton pellet inside the pulp chamber with temporary restoration. Dentinal permeability was quantified by copper ion penetration. Linear measurements were obtained by analysis of digital images under x 5 magnification. Mean values and SD for the experimental groups were: I, 7.1% (+/-3.2%); II, 8.4% (+/-3.0%); III, 9.1% (+/-3.0%); IV, 1.3% (+/-2.8%). One-way ANOVA was used to analyze the results. Results showed an increase of permeability values for groups I, II and III when compared to group IV (control); however, no statistical differences were found between the three tested bleaching techniques. It can be concluded that 35% hydrogen peroxide activated by LED, halogen lamp or used following the walking bleach technique produced similar increase in dentinal permeability.

Dental Pulp Cavity↗
PubMedDate not supplied

In vitro remineralization of in vivo and in vitro formed enamel lesions.

Thin sections of natural white spot enamel lesions (WS) and of artificial in vitro lesions (VL) were remineralized simultaneously in vitro. The sections, clamped in a PMMA holder, were microradiographed at baseline and after remineralization in a calcium- and phosphate-containing solution (pH = 7.0; 1 ppm F) after 2 and 4 weeks. All data were analyzed with respect to baseline. The results show that the lesion depth values did not change significantly during 2 and 4 weeks of remineralization. The mineral accumulation (change in DeltaZ), however, was substantial and significant in WS and VL. In WS the change in mineral accumulation was roughly proportional to the amount of mineral at baseline. The WS accumulated more than two times the amount of mineral than VL in the same periods of remineralization. After 4 weeks of remineralization the maximum mineral value Vmax in the surface layer of the WS was nearly up to the sound enamel level thick approximate87 vol%. This study shows that the technique and calculation procedure described make this single section method attractive for longitudinal demineralization-remineralization studies in vitro or in situ. Both WS and VL samples obviously remineralized in vitro similarly with respect to the baseline. Furthermore, this in vitro work indicates that remineralization inhibitors present in saliva, and previously penetrated into the enamel tissue, do not influence remineralization later on.

Absorptiometry, Photon↗
PubMedDate not supplied

Posteruptive changes of electrical resistance values in fissure enamel of premolars.

In studies about 15-25% of the caries-free teeth proved to have as low electrical resistance values as carious teeth, due probably to incomplete enamel maturation. It was the aim of the present prospective clinical study to investigate, if an increase in electrical resistance values could be observed after the eruption of premolars. The electrical resistance measurements were performed in children who were patients of the Dental School of the University of Marburg, Germany. The first measurement was made when a premolar was erupting or when it had erupted within 12 months before. The electrical resistance measurements were repeated every 3-6 months until the 24th posteruptive month. The measuring device consisted of an AC ohmmeter modified by Gente indicating the real component of the impedance and employing a frequency of 500 Hz and an amplitude of about 1 microA. For erupting teeth a mean resistance value of 17+/-15 kohm was computed when the contact fluid had been NaCl (A). The corresponding values were 72+/-51 kohm when distilled water (B) had been applied and 392+/-374 kohm when the initially saliva-coated teeth had briefly been dried (C). The mean resistance values of the premolars increased continuously from the eruption up to the 15th posteruptive month. This observation was independent of the three modes of measuring that had been used. It is concluded that enamel maturation leads to an increase in electrical resistance. To improve accuracy of caries diagnosis with electrical resistance measurements, the posteruptive age of teeth should be taken into account. In addition, electrical resistance measurements offer the opportunity to observe enamel maturation in vivo noninvasively.

Adolescent↗
PubMed1988

An in vivo study of microhardness and fluoride uptake in partially demineralized human enamel covered by plaque.

In this investigation, microhardness changes in partially demineralized human enamel were studied after in vivo use of fluoridated toothpaste systems. Flattened enamel specimens were demineralized in vitro and subsequently positioned in approximal positions in the prostheses of 27 participants for three weeks; the samples were plaque-covered in vivo. After brushing for one week with a non-fluoridated paste to achieve an in vivo equilibrium, participants brushed with an assigned product for a two-week period. This test was a six-way cross-over design which used randomization of subjects. Five fluoridated and one non-fluoridated paste were tested. Knoop hardness measurements were carried out on sound and on in vitro demineralized enamel, and after in vivo exposure of the enamel to the dentifrice treatments. The results showed that during the two weeks of in vivo exposure to the fluoride products, net rehardening of the demineralized enamel did not occur, and no correlation was observed between fluoride uptake into the demineralized enamel and changes in microhardness. That we failed to observe rehardening may be due to the fact that the duration of this study was too short for any net remineralization to have occurred, especially because the samples were constantly covered with plaque. Other possibilities, such as the type and/or severity of the lesions used in this study, may account for the lack of rehardening.

Analysis of Variance↗
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↗
PubMed1993

The ultrastructure of copper amalgam-covered dentin from human deciduous teeth.

The structure of dentin subjacent to Cu-amalgam restorations was studied. The restorations had been inserted 7-8 years before extraction of the teeth. No lining had been applied. The dentin subjacent to the restorations had a greenish-grayish discoloration, and in the pulpal end irregular secondary dentin had formed. Energy-dispersive X-ray microanalysis of areas showing discoloration confirmed the presence of Cu. Semithin and ultrathin undemineralized sections were studied. Vital pulp tissue and irregular secondary dentin were observed. Close to the predentin and halfway into the dentin most of the dentinal tubules were occluded. In the control material only an occasional occluded tubule was seen. Close to the Cu-amalgam restoration some tubules were occluded or partly occluded, and some were open. The odontoblasts had responded to the irritating agent by obturation of the tubules, thus reducing the permeability of the dentin. Furthermore, irregular secondary dentin had formed in another attempt to wall off the irritating agent.

Child↗
PubMedDate not supplied

Effect of anti-sensitive toothpastes on opened dentinal tubules and on two dentin-bonded resins.

Treatment of dentin hypersensitivity will become of increasing importance in the daily practice of dentistry. The goal of any therapy should be the closure of opened dentinal tubules. The present study made an SEM evaluation of the effect of anti-sensitive toothpastes on root dentin with regard to the superficial changes and possible penetration by toothpaste particles. Further, the study performed an evaluation of the wear-resistance of two dentin-bonded resins during brushing, using the same anti-sensitive toothpastes. Having induced coverage of the dentinal tubules with the toothpastes (Sensodyne, Emoform and Macleans Sensitive), no particles were found within the tubules. The application of dentin-bonded resins seems an alternative solution for treating dentin hypersensitivity.

Acrylic Resins↗
PubMed1981

Keratinization of the sulcular epithelium--a pointless pursuit?

A considerable amount of effort has been directed at finding methods for modifying the nonkeratinized sulcular epithelium on the assumption that a keratinized surface may offer a better barrier to antigens and bacterial products present in the gingival sulcus. It is argued here that keratinization in itself may not confer greater impermeability, for nonkeratinized epithelia also have been shown to resist the penetration of certain substances. Moreover, few workers have considered the role of junctional epithelium in the initiation of periodontal disease although experimental evidence suggests that this may be a permeable tissue. As formation of a surface with barrier properties seems to be a concomitant of epithelial differentiation while attachment is a property of relatively undifferentiated epithelial cells, attempts to induce junctional epithelium to differentiate could result in a loss of epithelial attachment to the tooth. It is suggested that attempts to keratinize the sulcular region, on theoretical grounds, may be unjustified.

Epithelial Attachment↗
PubMedDate not supplied

Permeability of enamel following light-activated power bleaching.

This study sought to ascertain whether in-office photocured bleaching techniques would increase permeability to enamel. A 7.1 mm2 circular area located in the middle third of the coronal portion of 90 human canines was isolated by applying an acid-resistant varnish to the remaining surfaces of the tooth. According to a randomized complete block design (n = 15), specimens were treated using a 35% hydrogen peroxide bleaching product activated by an integrated LED/diode laser (LED/laser) source or a quartz tungsten halogen (QTH) light. Bleaching was accomplished by applying the 35% hydrogen peroxide agent to the enamel surface in three 10-minute sessions, conducted at one-week intervals over a period of three weeks. For the photocured bleached groups, a bleaching agent was applied to the specimen and irradiated with the LED/laser device or the QTH light for 30 seconds. Negative control groups were exposed to artificial saliva or irradiated by the LED/laser device or the QTH light. Specimens were subjected to a histochemical coloring method that employed copper sulfate and dithio-oxamide solutions. Three 300-microm thick sections taken from the exposed area were imaged in an optical microscope. Permeability was measured in the digitized images as the percentage of copper ions penetration over the total enamel thickness. Friedman's test (alpha = 0.05) showed significant difference among groups. Least significant difference test revealed that in comparison with the group treated with 35% hydrogen peroxide only, there was no significant increase in enamel permeability when bleaching was activated by either the LED/laser or QTH light devices but all bleached groups showed higher permeability than the unbleached/nonirradiated group.

Analysis of Variance↗
PubMed2004

Osmotic blistering in enamel bonded with one-step self-etch adhesives.

One-step self-etch adhesives behave as permeable membranes after polymerization, permitting water to move through the cured adhesives. We hypothesize that osmotic blistering occurs in bonded enamel when these adhesives are used without composite coupling. Tooth surfaces from extracted human premolars were bonded with 5 one-step self-etch adhesives. They were immersed in distilled water or 4.8 M CaCl(2), and examined by stereomicroscopy, field-emission/environmental SEM, and TEM. Water blisters were observed in bonded enamel but not in bonded dentin when specimens were immersed in water. They collapsed when water was subsequently replaced with CaCl(2). Blisters were absent from enamel in specimens that were immersed in CaCl(2) only. Water trees were identified from adhesive-enamel interfaces. Osmotic blistering in enamel is probably caused by the low water permeability of enamel. This creates an osmotic gradient between the bonded enamel and the external environment, causing water sorption into the interface.

Acid Etching, Dental↗
PubMed1998

Composition of plaque and saliva following a sucrose challenge and use of an alpha-tricalcium-phosphate-containing chewing gum.

Calcium phosphate concentrations in plaque, plaque fluid, and saliva play an important role in caries prevention. In this study, we used a microanalytical technique to examine the anticaries potential of a 2.5% (mass fraction) alpha-tricalcium-phosphate-fortified experimental gum by measuring the pH, free and total calcium, and total phosphate in plaque fluid, whole plaque, and saliva, and centrifuged saliva from 14 subjects who (1) accumulated plaque for 48 hours, (2) fasted overnight, (3) rinsed for 1 min with sucrose, and (4) chewed a control or experimental gum for 15 min. From these data, the hydroxyapatite (HAp) ion activity products (IAP[HAp]) of saliva and plaque fluid were calculated as a measure of tooth mineral saturation. Results, compared with those of the control gum, show significant increases in pH and in free calcium and phosphate concentrations in plaque fluid and saliva when the experimental gum was chewed following sucrose ingestion. These increases result in a rise in fluid saturation with respect to tooth mineral that, for plaque fluid, nearly cancels the decrease seen with the control gum after the sucrose rinse. This suggests that the experimental gum may be more effective than a conventional gum in ameliorating the cariogenic effects of sucrose. Similar statistically significant increases were also seen in the total calcium content of the plaque fluid, centrifuged saliva, whole saliva, and whole plaque, and in the total phosphate of whole plaque and whole saliva. These results suggest that the deposition of a mineral reservoir in plaque and saliva by the experimental gum may help resist future cariogenic challenges.

Adult↗
PubMed1998

Effects of CO2 laser in treatment of cervical dentinal hypersensitivity.

The effectiveness of CO2 laser therapy in the reduction and elimination of dentinal hypersensitivity in vivo and its thermal effects on tooth surfaces in vitro were investigated. Twenty-three patients with 91 sensitive teeth participated in this study and were followed for 3 months. The parameters used with CO2 laser were 1 W in a continuous wave mode and irradiation time ranging from 5 to 10 s. Hypersensitivity was assessed by thermal stimulus (a blast of air from a dental syringe). Thermal effects were measured by thermography using 10 extracted human teeth. After laser treatment, all patients were immediately free from sensitive pain. Over 3 months, the CO2 laser treatment reduced dentinal hypersensitivity to air stimulus by 50%. All teeth remained vital with no adverse effects. Thermography revealed no temperature increase on irradiated tooth surfaces subjected to water coolant. These results show that the CO2 laser is useful in the treatment of cervical dentinal hypersensitivity without thermal damage to pulp.

Adult↗