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PubMed1992

Interfacial morphology of resin composite and shiny erosion lesions.

Ten shiny erosion lesions were divided horizontally, in vivo such that the gingival half was prepared and the incisal half remained unprepared. Both were etched simultaneously with 32% H3PO4 for 20 seconds, rinsed and restored using the All Bond wet technique and P50 composite. The teeth, which were extracted as part of a treatment plan, were sectioned vertically midway through the restorations. Polyvinyl siloxane impressions of the tooth/resin interface were taken and examined by SEM for the presence of gaps. The teeth were then demineralized and the fitting surfaces of the restorations were examined for resin penetration into the dentin. Results showed that there were no gaps present in any of the interfaces. The most proliferative and deep resin penetration occurred in the prepared/etched halves.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1992

Changes in the microvasculature after mechanical pressure on the hamster cheek pouch.

The reaction of the microvasculature in the periodontal ligament to mechanical pressure is considered a very important phenomenon with respect to the biological background to orthodontic tooth movement. For clarification of the microvascular reaction to mechanical pressure, an experimental model that incorporated a hamster cheek pouch was established. This in vivo model solves some of the problems of other experimental models of the microvasculature of the periodontal ligament. Blood plasma permeation in this model was examined by means of a blue dye (pontamine sky blue), and histological observation was performed by light and transmission electron microscopy. Increased vascular permeability was observed within 30 min after removal of the mechanical stimulation. The threshold weight resulting in dye leakage was between 1 and 5 g applied for 60 min. From the histological observations, some large gaps between the endothelial cells in venules were found, while most basement membranes remained undisturbed. These observations suggest that the plasma leakage was due to mild traumatic injury to the endothelial cells. Both leukocytes and platelets were observed in the gaps between the endothelial cells in the venule. These types of microvascular reactions to mechanical pressure could initiate tissue changes in the periodontal ligament during orthodontic tooth movement.

Animals↗
PubMed2006

Effects of etching time of primary dentin on interface morphology and microtensile bond strength.

OBJECTIVES: To determine the influence of different etching times (5, 15 or 30 s) on the morphology and micro-tensile bond strength (muTBS) of primary dentin. METHODS: For muTBS study, nine primary molars were randomly distributed in three experimental groups. Three Class I cavities per tooth were drilled and etched (37% orthophosphoric acid gel for 5, 15 or 30 s). Excite adhesive was applied and cavities restored with a resin composite (Tetric Ceram). Composite/dentin bars (ca. 1 mm2 section) were obtained from teeth and tested in tension until debonding. Means of muTBS results were compared with ANOVA and Student-Neuman-Keuls post hoc tests. Morphology: Three occlusal cavities were prepared in five primary molars. Each cavity was etched and restored as described for previous groups and teeth were sectioned mesio-distally. One half of each tooth was prepared for using under optical microscopy using Masson's trichromic dye technique and the other half was examined by SEM. RESULTS: muTBS mean (S.D.) results (in MPa) were 5 s etch: 6.20 (2.81), 15 s: 13.43 (5.91), 30 s: 13.04 (5.67). muTBS groups were Excite 5 s < Excite 15 s = Excite 30 s. Masson's trichromic technique stained the demineralized dentin layer red in all specimens. The mean (S.D.) thickness of the demineralized layers (in mu) were 5 s: 3.28 (1.23), 15 s: 3.83 (1.26), 30 s: 4.44 (1.70). There is a statistically significant linear relationship between time of application of etching and mean depth of demineralized layer. This relationship was established as depth (in mu) = 3.08 + 0.05 time (in s). SIGNIFICANCE: The minimum adequate etching time for primary dentin is 15s.

Acid Etching, Dental↗
PubMed1990

A review of current approaches to in-office management of tooth hypersensitivity.

In-office treatment of dentinal hypersensitivity should be capable of providing the patient with immediate and lasting relief of pain. Regardless of the type of treatment employed, 20 to 40 per cent of hypersensitive teeth usually improve over a period of 4 to 8 weeks. Partial obturation of open tubules is the most widely practiced treatment, with other forms of therapy being recommended as a backup for patients in whom this approach fails. Obturation can be achieved with topical application of agents that form insoluble precipitates within the orifices of the tubules. Burnishing the exposed root surface produces a smear layer, which in itself can significantly reduce dentin permeability. At times, the use of a restorative resin or dentin bonding agent can be successful in reducing sensitivity when other forms of therapy have failed. Proper patient management should stress dietary counseling when dietary acids are an important etiologic factor. The importance of proper tooth brushing and plaque control must be stressed. At the present time, the use of oxalates for the obturation of tubules shows promise as a future in-office clinical agent; however, further clinical studies are required to evaluate and compare their efficacy with other currently effective methods and agents.

Calcium↗
PubMed2004

Scanning electron microscopy (SEM) and optical microscopy: effects of Er:YAG and Nd:YAG lasers on apical seals after apicoectomy and retrofill.

OBJECTIVE: This study evaluated the dentinal and marginal permeability of the cut surface after apicoectomy, treatment and retrocavity preparation with Er:YAG and Nd:YAG lasers. Furthermore, scanning electron microscopy (SEM) analysed the morphological alteration of dentin caused by laser irradiation through an optical fiber. BACKGROUND DATA: Numerous studies have shown the beneficial effects of laser treatment upon sealing dental apex, avoiding the changes of organic fluids, microorganisms and their by-products between the root canal system and periapex. MATERIALS AND METHODS: Twenty-four extracted and endodontically treated teeth were divided into three groups: GI, apices were resected with Er:YAG laser (350 mJ; 4 Hz) treatment of cut dentinal surface and retrocavity were lased with this same laser (120 mJ; 4 Hz; bur 2051) using the optical fiber 50/10; GII, apicoectomy was performed similar to GI, however the cut dentinal surface was treated with Nd:YAG laser through optical fiber, as well as the retrocavity preparation (100 mJ; 15 Hz; 1.5 W); and GIII (control group), high speed burs were used. RESULTS: Analysis of methylene blue dye penetration into dentin demonstrated that the specimens of the groups irradiated with laser showed to have lower infiltration indices than the control group. These results were compatible with structural and morphological injuries, evidenced by SEM. CONCLUSION: Under the conditions of the present study, apicoectomy using Er:YAG laser, followed by dentinal surface irradiation and retrocavity preparation with Nd:YAG laser, showed to be an alternative clinical tool able to reduce the dentinal permeability.

Humans↗
PubMed1996

Dentin bonding: SEM comparison of the resin-dentin interface in primary and permanent teeth.

Previous studies have suggested minor differences between primary and permanent teeth in terms of dentin composition and morphology. Other reports indicated lower bond strengths of resin composites to dentin of primary teeth compared with dentin of permanent teeth; however, no information is available regarding differences in the micromorphology of the resin-dentin interface that may explain these lower bond strengths. Therefore, the purpose of the present study was to compare primary and permanent teeth in terms of the thickness of the hybrid layer developed with two bonding systems. Our hypothesis was that bonding differences previously reported between primary and permanent dentin would be reflected in hybrid layer differences observable in SEM analyses. Twenty human extracted and non-carious teeth were divided into 4 groups: 5 primary and 5 permanent teeth restored with All-Bond 2/Bisfil P system; and 5 primary and 5 permanent teeth restored with Scotchbond Multi-Purpose/Z100. The sample area available on each tooth was divided for the two dentin conditioning times (7 and 15 sec). Measurements of hybrid layer thickness were performed by means of SEM at x13,000. The results of this study indicated that the hybrid layer produced is significantly thicker in primary than in permanent teeth (p = 0.0001), suggesting that primary tooth dentin is more reactive to acid conditioning. No difference was observed in the hybrid layers produced by the two adhesive systems (p = 0.7920). The increased thickness of the hybrid layer in primary teeth (25 to 30%) and the subsequent lack of complete penetration of adhesive resin into previously demineralized dentin may contribute to the lower bond strengths to primary dentin reported in the literature. If a narrower hybrid layer more uniformly infused with resin is the goal of dentin bonding, it is concluded that a differentiated protocol for bonding to primary dentin (with shorter time for dentin conditioning) can be used as a means to reproduce the hybrid layer thickness seen in permanent teeth.

Acid Etching, Dental↗
PubMed2004

Shortening of primary dentin etching time and its implication on bond strength.

OBJECTIVE: The aim of this study was to investigate the influence of shortening the etching time on the bond strength of a conventional and a self-etching primer adhesive system used in primary tooth dentin. METHODS: Flat dentin surfaces were obtained from 24 primary molars, randomly assigned to 4 experimental groups. The adhesive systems Single Bond and Clearfil SE Bond were applied in two groups according to the manufacturers' recommendations. In the other two groups, the adhesives were applied after half-time of acid etching, 7 s for Single Bond and 10 s for Clearfil SE Primer. Resin crowns were built up and after 24 h storage in water at 37 degrees C, the teeth were sectioned to produce beams with cross-sectional area of approximately 0.49 mm2. Specimens were tested in tension at 0.5 mm/min until failure. Fractured specimens were analyzed to determine the failure mode. RESULTS: Tensile bond strengths for Single Bond in primary dentin were higher than for Clearfil SE Bond. Shortening of acid etching time improved bond strength only for Single Bond, while no statistically significant difference was observed for Clearfil SE Bond when both etching times were compared. SIGNIFICANCE: No detrimental effect on bond strength was observed when the time of acid etching was shortened in 50%. Shortening the time for a procedure in a small child without compromising the quality of the work is a very important finding for the practicing pediatric dentist.

Acid Etching, Dental↗
PubMedDate not supplied

Microtensile bond strength of different adhesive systems to primary and permanent dentin.

PURPOSE: The aims of this in vitro study were to: (1) compare bond strength of different adhesive systems to primary and permanent dentin using microtensile test; and (2) evaluate the interaction of these materials to primary and permanent dentin by means of scanning electron microscopy (SEM). METHODS: Middle-coronal dentin surfaces of 18 exfoliated primary and 18 extracted permanent molars were exposed and teeth were randomly divided, according to their adhesive system, into 3 groups (N=6 per group): (1) Clearfil SE Bond (SE); (2) One Up Bond F (OU); and (3) Single Bond (SB). Then, 5-mm high composite blocks were constructed. After bonding procedures, the teeth were stored in distilled water at 37 degrees C for 24 hours prior to the specimens' preparation. For the microtensile test, teeth (N=5 per group) were longitudinally sectioned into 2 axes rendering beam-specimens that were glued to special devices, which were mounted in a Universal Testing Machine to be loaded under a crosshead speed of 1 mm/min until fracture. One tooth of each group was prepared for SEM. RESULTS: Microtensile bond strength mean values (MPa) to primary/permanent dentin were: (1) SE=60.0/61.4; (2) OU=54.5/53.3; and (3) SB=70.1/64.9. Two-way analysis of variance (ANOVA) showed no significant differences (P>.05) for the bond strength values among primary and permanent dentin groups, neither among groups SExSB and SExOU. SEM images of SE and SB showed a well-defined, uniform, and continuous hybrid layer. A continuous hybrid layer, however, was not found for OU. CONCLUSIONS: Bond strength and micromorphologic characteristics of the adhesive systems evaluated were not influenced by the substrate. OU achieved worse results.

Adhesives↗
PubMed1993

pH changes in root dentin over a 4-week period following root canal dressing with calcium hydroxide.

Root canals in extracted human teeth were cleaned and shaped and subsequently dressed with a calcium hydroxide root canal dressing. pH Changes in the root dentin were measured over a 4-wk period with microelectrodes in small cavities at apical and cervical levels in inner and outer dentin. The pH increased within hours in the inner dentin, peaking at pH 10.8 cervically and 9.7 apically. However, 1 to 7 days elapsed before the pH began to rise in the outer root dentin, reaching peak levels of pH 9.3 cervically and 9.0 apically after 2 to 3 wk. The results show that hydroxyl ions derived from a calcium hydroxide dressing do diffuse through root dentin. They diffuse faster and reach higher levels cervically than apically. Surface pH measurements showed that hydroxyl ions do not diffuse in more than a minor way through the intact root surface.

Adult↗
PubMed1991

Effect of endodontic procedures on root dentin permeability.

The purpose of this study was to quantitate the sequential effects of endodontic procedures on the permeability of human root dentin in vitro. Forty single-rooted teeth were used. Both the crown and the apical 2 mm of the root were removed. The hydraulic conductance of the root before and after various endodontic procedures was measured using a fluid filtration method. Measurements were also made of dentin thickness, intracanal diameter changes, and changes in intracanal surface area. The results showed that instrumentation by K files alone or in combination with Gates Glidden drills did not alter radicular dentin permeability when the cementum remained intact. After removing the cementum, the creation of a smear layer and smear plugs on the canal surface tended to offset the expected increase in dentin permeability created by increasing the intracanal surface area and decreasing root dentin thickness. EDTA treatment inside the instrumented canal to remove the smear layer did not increase permeability significantly. The use of K files followed by Gates Glidden drills tended to remove more cervical dentin, increased the intracanal surface area, and increased the hydraulic conductance of root dentin more than the use of K files alone.

Dental Cementum↗
PubMed1996

Effect of dentin treatment on in vitro root tubule bacterial invasion.

In light of the in vitro S. sanguis bacterial migration observed deep into root dentin, an in vitro system was developed to determine the viability of these bacteria at the end of migration. Also of interest is whether the smear layer formed during root canal instrumentation modifies migration into root dentinal tubules. Forty-eight bovine root dentin samples were randomly split into two groups. Group 1 dentin blocks were not instrumented and were treated with 17% ethylenediamine tetraacetic acid and 2.5% sodium hypochlorite for 4 minutes in an ultrasonic bath Group 2 root canals were conventionally instrumented. The smear layer formed was not removed. Dentin blocks were inoculated with a S. sanguis National Collection of Type Culture 7863 suspension. Each sample was immersed in a receiver broth, incubated at 37 degrees C, and checked daily for 14 days. After a 14-day incubation period, group 1 S. sanguis cells remained viable and capable of inoculating the receiver medium after migration through the tubules. Group 2 cells, where the smear layer was intact, revealed an absence of S. sanguis migration in 88% of the cases. It is therefore plausible that smear layer on canal walls limits S. sanguis penetration of dentinal tubules in vitro.

Animals↗
PubMed2004

In vitro penetration of bleaching agents into the pulp chamber.

AIM: To investigate pulp chamber penetration of bleaching agents in teeth following restorative procedures. METHODOLOGY: Bovine lateral incisors were sectioned 3 mm apical to the cemento-enamel junction and the coronal pulpal tissue was removed. Teeth were divided into six groups (n = 10): G1, G2 and G3 were not submitted to any restorative procedure, while G4, G5 and G6 were submitted to Class V preparations and restored with composite resin. Acetate buffer was placed in the pulp chamber and treatment agents were applied for 60 min at 37 degrees C as follows: G1 and G4, immersion into distilled water; G2 and G5, 10% carbamide peroxide (CP) exposure; G3 and G6, 35% CP bleaching. The buffer solution was removed and transferred to a glass tube where leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined spectrophotometrically at 596 nm. A standard curve made with known amounts of hydrogen peroxide was used to convert the optical density values of the coloured samples into microgram equivalents of hydrogen peroxide. Data were submitted to anova and Tukey's test (5%). RESULTS: Amounts of hydrogen peroxide found in the pulp chamber of G2 and G5 specimens (0.1833 +/- 0.2003 micro g) were significantly lower (P = 0.001) when compared to G3 and G6 specimens (0.4604 +/- 0.3981 micro g). Restored teeth held significantly higher (P = 0.001) hydrogen peroxide concentrations in the pulp chamber than intact teeth. CONCLUSION: Higher concentrations of the bleaching agent produced higher levels of hydrogen peroxide in the pulp chamber, especially in restored teeth.

Analysis of Variance↗
PubMed1996

Calcium ion diffusion from calcium hydroxide-containing materials in endodontically-treated teeth: an in vitro study.

The aim of this in vitro study was to determine the amount and duration of diffusion of calcium ions from both a calcium hydroxide-containing root canal sealer and an intracanal medicament, through the apical foramen and the dentinal tubules of endodontically-treated teeth. The root canals of 88 freshly extracted single-rooted teeth were prepared using the modified double flared, balanced force technique with patency filing. The teeth were divided into four test groups of 20 teeth each and a control group of eight teeth. One group was dressed with a non-setting calcium hydroxide while the other was obturated using cold lateral condensation of gutta-percha with a calcium hydroxide-containing sealer. An artificial root defect was created in the apical third of the root of the teeth in the other two groups and the root canals were either dressed or obturated in the same way as the first two groups. All groups were incubated at 37 degrees C and were sampled for calcium diffusion after 1, 2 and 3 days and 1, 2, 3, 4 and 8 weeks. There was statistically significantly more calcium diffusion with the non-setting groups compared with the sealer groups (P < 0.05). There was more calcium ion diffusion from teeth with a patent apical foramen than those with an artificial resorptive root defect (P < 0.05).

Analysis of Variance↗
PubMed1980

Fluoride concentrations in fissure and cervical enamel of unerupted human teeth.

Fluoride concentration of fissure enamel from unerupted third molars was higher than that of the cervical-lingual but not cervical-buccal surfaces at a similar depth of the removed enamel. The highest fluoride concentration was found in the fissure enamel due probably to its earlier formation, higher permeability and embedding tissue before eruption.

Dental Enamel↗
PubMed1996

Restorative therapy for erosive lesions.

More needs to be learned about the etiology of erosion lesions before they can be accurately diagnosed, confidently treated and, more importantly, prevented. The treatment is dependent on the location and the degree of erosion. The decision to treat an erosion lesion should be based on careful consideration of the etiology and progression of the condition. Reasons for restoring noncarious enamel/dentin lesions are discussed and various therapeutic measures are provided. Preventive and restorative therapeutic measures for noncarious abrasive/ erosive lesions are proposed such as: a change of dietary or behavior patterns; application of desensitization products; intensive fluoride therapy with or without iontophoresis; brushing with desensitizing dentifrices; adhesive penetration with dentin bonding agents; glass ionomers and compomers; resin composites; composite or porcelain veneers; crown and bridge work; occlusal adjustments and nightguard fabrication if the abfraction factor coincides. The clinical durability of restorative therapy and important clinical factors related to the restoration of multifactorial defects are discussed.

Composite Resins↗
PubMed1998

Inhibition of dentin demineralization by fluoride in vitro.

Compared with the knowledge accumulated on enamel-fluoride interactions, relatively little data is available regarding fluoride effects on dentin. This applies to both laboratory and clinical studies into the efficacy of fluoride schemes for the prevention of root surface caries. This study aimed to determine the effects of fluoride and pH on the demineralization of dentin, such as to provide information necessary to develop preventive programmes. Bovine dentin blocks were subjected to undersaturated calcium- and phosphate-containing solutions in the pH range 4.0-6.0 with fluoride added at concentrations between 0.5 and 10 ppm. Non-fluoride solutions served as controls. Mineral loss was assessed chemically and by transversal microradiography. Comparisons were made with similar studies on enamel demineralization. The results showed that demineralization of dentin depends on both pH and fluoride concentration in the demineralizing solution. Inhibition of demineralization that could be relevant from a clinical point of view was found at fluoride values 5-10 times the corresponding values for enamel. Also rapid depletion of fluoride from the solutions was observed, indicating the high uptake capacity of dentin for fluoride. Lesion depth depended on pH of the solution while the fluoride levels were associated with the surface layer, both in mineral content and depth. For dentin we propose a demineralization mechanism where acid penetrates rapidly into the tissue, presumably through the tubules, after which the released calcium and phosphate is partly trapped by the inward diffusing fluoride. This leads to the formation of a surface layer, which may even be hypermineralized compared to sound dentin.

Animals↗
PubMed1996

The threshold effects of Nd and Ho: YAG laser-induced surface modification on demineralization of dentin surfaces.

Laser irradiation alters the structure of dentin and produces surface layers that give the appearance of being more enamel-like. The laser-modified surface may be more resistant to demineralization; hence, many investigators are proposing continued development of the laser as a possible preventive treatment for caries. The purpose of this study was to explore the morphological changes that occur in dentin when treated at threshold illuminance with two clinically interesting laser wavelengths, and to evaluate the effectiveness of the laser-treated surface at resisting demineralization in an acid-gel solution. The Nd: YAG laser (wavelength 1060 nm) produced significant recrystallization and grain growth of the apatite, without the formation of second phases such as beta-tricalcium phosphate. This recrystallized surface layer showed resistance to demineralization; however, the layer did not provide protection of the underlying dentin from demineralization because of cracks and macroscopic voids that allowed for penetration of the demineralizing gel. The Ho: YAG laser-treated surface (wavelength 2100 nm) did not show significant evidence of recrystallization and grain growth, and only a trace amount of an acid-resistant layer was observed with demineralization. It is speculated that the Ho:YAG laser is coupling with absorbed water, and that the heat transfer from the water to the mineral phase is inefficient. For the purposes of creating a demineralization-resistant layer, threshold illuminance with both Nd: YAG and Ho: YAG was ineffective.

Absorption↗