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PubMed1992

Prerestorative bleaching: effect on microleakage of Class V cavities.

The effect of bleaching extracted teeth on the microleakage of subsequently placed Class V composite resin restorations was evaluated. Ten extracted premolars were stored in water at 37 degrees C to serve as controls. Ten premolars were exposed to a carbamide peroxide gel for three 2-hour periods per day for 9 days. These specimens were stored in water at 37 degrees C except during treatment periods. Class V cavity preparations were then placed at the cementoenamel junction of the facial and lingual surfaces of all teeth. Half of the teeth of each group were restored with Scotchbond 2/Silux Plus and half were restored with Prisma Universal Bond 3/AP.H. After 24 hours of storage in 37 degrees C water, the teeth were thermally stressed for 100 cycles. Microleakage was assessed by dye penetration. The results demonstrated that prerestorative bleaching did not affect the marginal seal of subsequently placed restorations.

Analysis of Variance↗
PubMedDate not supplied

Evaluation of the bonding mechanism of an adhesive material to primary teeth.

PURPOSE: The aim of this study was to evaluate with scanning electron microscopy (SEM) the bonding mechanism of the one-bottle adhesive Prime&Bond NT (Dentsply, PBNT) to enamel and dentin of deciduous teeth, following different methods of substrate treatment. METHODS: Eighteen extracted posterior deciduous teeth were randomly divided into 6 groups (N=3). The experimental groups differed for substrate and method of substrate conditioning prior to bonding with PBNT. Group 1: 36% phosphoric acid (PA)/PBNT on dentin; group 2: PA/PBNT on enamel; group 3: non-rinsing conditioner (NRC) (Dentsply)/PBNT on dentin; group 4: NRC/PBNT on enamel; group 5: PBNT on dentin without any previous conditioning; group 6: PBNT on enamel without any previous conditioning. On all the specimens, following the application of the adhesive solution, Dyract AP was layered on top and light-cured. The bonded specimens were processed for SEM observations. RESULTS: When used in combination with 36% phosphoric acid, PBNT was able to form a hybrid layer with resin tags on both enamel and dentin. Following conditioning with NRC, a thinner hybrid layer with shorter resin tags was developed on dentin; on enamel an etching pattern was still detectable. When only PBNT was applied without any previous conditioning, on dentin neither hybrid layer nor resin tags were visible; no sign of micromechanical bonding could be seen on the untreated enamel. CONCLUSIONS: The bonding mechanism of the one-bottle adhesive Prime&Bond NT on enamel and dentin of deciduous teeth is effective only following substrate conditioning with 36% phosphoric acid or NRC.

Acid Etching, Dental↗
PubMed1995

An SEM examination of etched dentin and the structure of the hybrid layer.

The clinical requirements of dentin bonds are that they should be non-permeable to oral fluids, seal dentinal tubules, protect the pulp, and be long lasting and durable. Dentin bonding systems that use acidic agents to remove the smear layer are currently being used. Acid conditioning not only removes the smear layer, but also demineralizes the surface of the intertubular dentin and produces intratubular demineralization and funnelling. A dentin bond is produced when hydrophillic resin monomers infiltrate the dentinal tubules and collagen of the demineralized intertubular zone, producing a hybrid layer. The use of a critical point drying technique and SEM allows a clear visualization of the structure of the hybrid layer. This study showed that currently used hydrophillic resin monomers are unable to completely infiltrate the demineralized zone, and it is speculated that this failure could contribute to microleakage and influence the long-term durability of the bond. It is also apparent that these bonds depend on the mechanical investment of collagen by the infiltrating monomer. Since none of the unfilled resins tested seem capable of completely infiltrating the demineralized collagenous zone, the degree of demineralization produced by the commercial acid concentrations in current use is questioned. More dilute acids than those available commercially are shown to reduce both the degree and depth of demineralization, and we suggest that the resultant thinner layer may lend itself to more complete resin infiltration of the collagen.

Acid Etching, Dental↗
PubMed1998

Bonding mechanism of Compoglass to dentin in primary teeth.

This study evaluated the bonding mechanism of Compoglass compomer to dentin in primary teeth. Buccal or labial dentinal surfaces of 20 human extracted, non carious primary teeth stored in 4 degrees C physiological saline solution were obtained by grinding on silicon carbide paper (final grit 600). The specimens were divided into two groups of 10 teeth each: (1) unetched dentin, Compoglass SCA, Compoglass; and (2) dentin etched with 10% phosphoric acid (Etch-AII), Compoglass SCA, Compoglass. The Compoglass SCA and Compoglass compomer were placed according to the instructions of the manufacturer, except Group 2 were the dentin was first etched with 10% phosphoric acid for 30 seconds. Twenty-four hours after placing the compomer over the treated dentinal surface, the specimens were dehydrated with a series of alcohol and freon. Then critically point dried. The specimens were split with a chisel and the compomer/dentin interface evaluation was performed with the SEM. The results showed that when the instructions of the manufacturer were followed (Group 1) the compomer showed a very close relation to the dentin with some tag structures penetrating the dentin. When phosphoric acid etching preceded the compomer placement a hybrid layer with tags penetrating the dentin was noted in most specimens.

Acid Etching, Dental↗
PubMed1995

Endodontic pathogens: propagation of infection through patent dentinal tubules in traumatized monkey teeth.

Periapical pathology indicating endodontic infection, when present in marginal periodontitis-affected teeth, has recently been shown to be an aggravating factor in progression of marginal destruction. This has been associated with patency of dentinal tubules in the tooth cervix, an area normally devoid of cementum following periodontal therapy. These studies are, however hampered by that only circumstantial evidence such as presence of periapical destruction have been applied as criteria of endodontic infection. The purpose of the present investigation was to study to what extent a predefined selection of endodontic pathogens inoculated in the root canal can influence periodontal pathology and healing in areas of the root covered by or devoid of cementum, using root resorption as a histomorphometric marker. Exposed dentine surfaces, in the present study showed significantly larger areas of resorption in infected roots compared to non-infected roots, while cementum surfaces showed an almost identical distribution of tissue reactions regardless of root canal infection or not. It was concluded that endodontic pathogens or their products were not able to penetrate the cementum barrier. The significantly larger areas of resorption on exposed dentine surfaces in infected roots compared to non-infected roots indicated that endodontic pathogens or their products could spread through dentinal tubules to a root surface void of cementum. Extrapolated to the marginal situation this indicated that endodontic pathogens in the root canal might be able to aggravate marginal infection in areas of root devoid of cementum.

Animals↗
PubMed1999

Strengthening of tooth enamel by a remineralizing toothpaste after exposure to an acidic soft drink.

The effect of remineralizing and conventional toothpaste treatments on the hardness of intact and acid soft drink-etched enamel were assessed in a laboratory study. The remineralizing toothpaste (Enamelon Toothpaste) used in the study contains NaF, and simultaneously provides dissolved calcium, phosphate and fluoride ions. The conventional toothpaste contains NaF in a silica base. Sound extracted maxillary human incisors, mounted in epoxy resin with the facial incisal two-thirds exposed, were polished with 0.3 mu alumina. Groups of ten teeth were exposed to either twenty 5-minute treatments with an acid soft drink (pH 2.4), remineralizing or conventional fluoride toothpaste, or to twenty alternating cycles of a 5-minute protective treatment with either the remineralizing or conventional toothpastes, followed by 5-minute exposures to the acid soft drink, or to 20 five-minute exposures to the acid soft drink followed by 20 five-minute restorative treatments with the remineralizing or conventional toothpastes. Knoop Hardness measurements were made before and after treatment using a 500 g load and 15-second dwell time. Acid soft drink exposure produced a 15.4% drop in hardness compared with 4.9% and 1.6% hardness increases due to treatments of intact enamel with the remineralizing and conventional toothpastes, respectively. Protective treatments using the remineralizing and conventional toothpastes significantly reduced the drop in hardness due to acid soft drink exposure to 3.3% and 6.2%, respectively. Restorative treatments by the remineralizing and conventional toothpastes significantly increased the hardness of the acid soft drink-weakened enamel by 12.1% and 7.3%, respectively. Both toothpastes were effective in inhibiting damage due to acid soft drink exposure, but the remineralizing toothpaste was more effective in hardening intact and decalcified enamel than the conventional toothpaste (p < 0.05).

Analysis of Variance↗
PubMed1995

Tooth color and reflectance as related to light scattering and enamel hardness.

Tooth color is determined by the paths of light inside the tooth and absorption along these paths. This paper tests the hypothesis that, since the paths are determined by scattering, a relation between color and scattering coefficients exists. One hundred and two extracted incisors were fixed in formalin, mounted in a standardized position in brass holders, and pumiced. A facet was prepared near the incisal edge on the labial plane to allow for Knoop hardness measurements with a 500-gram load. Light scattering by the enamel was measured in a 45 degrees/0 degrees geometry; light scattering by both enamel and dentin was measured in a 0 degrees/0 degrees geometry. The reflection spectrum of the tooth was measured from the labial plane with a spectroradiometer in a 45 degrees/0 degrees geometry, with standard illuminant A and standard illuminant D65. To include all volume-reflected light, we used entire-tooth illumination and small-area measurement. CIELAB color coordinates were calculated from the spectra. Neither spectra nor coordinates showed evidence of a contribution of fluorescence to tooth color. Averaged values and standard deviations for L*,a*,b* were 69.9 (4.1), 1.22 (1.4), and 17.9 (2.9), respectively. Both scattering coefficients averaged to 0.6 (0.4) mm-1; Knoop hardness number was, on average, 271 (39) kg/mm2. L* correlated with a* (r = -0.51), with the enamel scattering coefficient (r = 0.60), and slightly with hardness (r = 0.17, p = 0.03). The colors of 28 teeth from which the enamel was removed correlated strongly with the colors of the complete tooth.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemical Phenomena↗
PubMed2001

PDL neuron-associated neurotransmitters in orthodontic tooth movement: identification and proposed mechanism of action.

The remodeling of the PDL and alveolar bone that occurs during orthodontic tooth movement (OTM) has long been associated with an inflammatory process. The vascular and cellular changes that occur have been well documented, and several inflammatory mediators, growth factors and neuropeptides have been found in increased levels in the periodontal supporting tissues during orthodontic tooth movement. It recently was found that peripheral nerve fibers participate in the inflammatory process (neurogenic inflammation) by releasing various neuropeptides. Calcitonin gene-related peptide (CGRP) and substance P (SP), two PDL neuropeptides, play a role in inflammation by serving as vasodilators and inducing increased vascular permeability. They also stimulate plasma extravasation and proliferation of endothelial cells and fibroblasts; upregulate the expression of endothelial cell adhesion molecules; and act as neurotransmitters. The increase in concentration of these PDL neuropeptides during OTM indicates their importance to the process. This paper will review the current research and summarize the roles and proposed mechanism of these two main PDL neurotransmitters in OTM.

Calcitonin Gene-Related Peptide↗
PubMed1993

Effect of sucrose concentration on the cariogenic potential of pooled plaque fluid from caries-free and caries-positive individuals.

Pooled plaque samples were obtained from (1) coronal surfaces of two groups of caries-free (CF) subjects, (2) coronal 'white-spot' surface areas of a group of caries-positive (CP) subjects, and (3) exposed, sound root surfaces of root caries-free (RCF) and root caries-positive (RCP) subjects. The plaque samples were obtained before and 3 min after a 1 min rinse with a 0.5, 1, 2, 5 and 10% sucrose solution. Plaque fluid was then isolated from each plaque sample by centrifugation and analyzed for inorganic ions, organic acids, and pH values. With increasing sucrose concentration: (1) plaque fluid pH and the degree of saturation (DS) with respect to tooth mineral decreased; (2) the pH and DS values of CP and RCP samples were consistently lower than those of CF and RCF samples, respectively; (3) plaque fluid lactic acid concentrations increased and were consistently higher in the CP and RCP samples than in the CF and RCF samples, respectively, and (4) plaque fluid lactic acid concentrations leveled off between 1 and 5% sucrose; this occurred at lower sucrose concentrations with CP and RCP samples than with CF and RCF samples, respectively. RCP samples contained consistently higher levels of mutants streptococci than RCF samples. The chemical composition of plaque fluids, following sucrose exposure, were found to correlate well with caries history. The observed differences in lactic acid concentrations in samples from CF and CP subjects are discussed with regard to differences in microbiological composition and possible differences in plaque permeability to sucrose.

Adolescent↗
PubMed2006

Interfacial characteristics of adhesive luting resins and composites with dentine.

PURPOSE: To evaluate the interfacial characteristics of five adhesive resin luting agents with dentine including tensile bond strength, failure mode, extent of demineralisation, morphological changes and hybrid layer formation. MATERIALS AND METHODS: The products tested were Bistite II DC (BDC), C&B Super-Bond (CBM), M-Bond (MBD), Panavia-F (PAF) and Rely-X Unicem (RXU). For tensile bond strength measurements (TBS), metallic rods were bonded to standardised dentine surface areas (n=10), thermal-cycled (3000x 5-55 degrees C, 4 cycles/min) and debonded at 1mm/min crosshead speed. The failure mode was examined on dentine surfaces by LV-SEM (n=10), whereas the thickness of the hybrid layer by HV-SEM (n=4). FT-IR microscopy (n=4) and ESEM (n=4) were used to assess the extent of demineralisation and the morphological changes induced on dentine by the conditioning and priming treatments. RESULTS: TBS (MPa) values were BDC (13.01), MBD (9.19) and PAF (7.07) significantly different from CBM (4.79) and RXU (4.47). The percentage of debonded dentine area covered with resin showed the highest values in BDC (47.80) and MBD (38.12) significantly different from CBM (17.20), PAF (16.47), and RXU (16.50). The extent of demineralisation for CBM was 100%. No statistical differences were found among BDC (60.86%), MBD (60.22%) and PAF (51.99%). RUX (45.03%) showed the lowest value. CBM induced the most pronounced tubule funneling and intertubular dissolution, followed by PAF, BDC and MDB. RXU partially removed the smear layer without opening tubule orifices. The thickest hybrid layer was found in CBM (4.17microm) followed by MBD (2.39microm). No statistically significant differences were found between PAF (0.95microm) and BDC (1.12microm), whereas RXU showed no detectable hybrid layer. SIGNIFICANCE: Significant differences were found in the interfacial properties among the materials tested, that may lead to differences in their clinical performance.

Analysis of Variance↗
PubMed2004

In vitro dentine permeability: the relative effect of a dentine bonding agent on crown preparations.

OBJECTIVE: The aim of this study was to determine whether a dentine bonding agent (DBA) had an effect in reducing fluid filtration under cemented provisional crowns. METHODS: Crown preparations on 34 premolars, randomly allocated to two equal-sized test and control groups, were assessed for dentine permeability by a fluid filtration technique. In the test group, prepared crowns were acid-etched and then treated with a DBA (Prime & Bond NT). In the control group, no such DBA was applied. Provisional crowns were cemented on both groups of teeth using non-eugenol zinc oxide cement. Fluid filtration rates were measured repeatedly after crown preparation, at cementation, 1 h, 1 day, 1 week and 3 weeks following crown cementation for both groups. Filtration rates were also measured after acid-etching and dentine bonding for the test group. RESULTS: There was insufficient evidence to suggest any statistically significant differences either between the two groups or, on average, across the five time points in each group in terms of the relative percentage of fluid filtration. CONCLUSION: The DBA used did not seal dentinal tubules any more than did the smear layer and provisional crowns luted with a non-eugenol ZnO cement.

Acid Etching, Dental↗
PubMedDate not supplied

Scanning electron microscopy of softened enamel.

After exposing enamel specimens to 0.3% citric acid at pH 3.2 for various times, the acid was titrated to pH 7 before rinsing the specimens in water. After freeze-drying the specimens were examined by scanning electron microscopy. This procedure eliminates artefacts due to drying and mineral precipitation. The results showed that the outer region of softened enamel is much more delicate than previously thought, even after short (5- to 20-min) etching times. Mineral was lost from both prism boundaries and the prism bodies, resulting in a surface presenting thin, separate crystal bundles. In further studies, replicas of subsurface pores, created by resin impregnation, showed the softening depth to be several times greater than is suggested by techniques based on removing the softened enamel by physical forces. The results point to a need for improved methods of measuring softening depth. More importantly, it appears that the outer region of the softened layer remaining after an erosive challenge might be too fragile to resist frictional forces in vivo.

Acid Etching, Dental↗
PubMed1998

Intradermal irritation of dental bleaching agents in rats.

AIM: To evaluate the irritative potential of three dental bleaching agents (hydrogen oxide, carbopol, and carbamide peroxide). METHODS: In rats, Evans blue (2.5%, 1 mL.L-1) was injected i.v. and later each test solution was injected intradermally on the back. After the concentration of the dye in the stained skin area was determined by spectrophotometric analysis. RESULTS: All the dental bleaching agents caused increase of vascular permeability and the intensity varied with the time. CONCLUSION: Dental bleach agents had a great potential for irritating soft tissues.

Acrylic Resins↗
PubMed2002

Shear bond strengths to coronal and pulp chamber floor dentin.

PURPOSE: To evaluate the bond strengths of two different types of resin bonding systems to coronal dentin and dentin of the pulp chamber floor. MATERIALS AND METHODS: 20 extracted human molars were sectioned into three regions; superficial coronal dentin, deep coronal dentin and floor of pulp chamber dentin. The dentin surface of each region was bonded with Single Bond or Clearfil Liner Bond 2V. A core build-up light-cured resin composite, Clearfil Photocore, was placed and light-cured for 40 seconds. After storage in 37 degrees C water for 24 hours, shear bond strengths were measured using a single plane shear test assembly at a crosshead speed of 2.0 mm/minute. Morphological changes of the conditioned dentin and hybrid layer formation were observed by SEM. RESULTS: For Single Bond, the bond strengths to superficial dentin were within anticipated bounds (23 MPa), whereas the bond strengths to deep dentin (15 MPa) and floor of pulp chamber dentin (13 MPa) were significantly lower (P < 0.05). For Clearfil Liner Bond 2V, higher bond strengths (approximately 30 MPa) were obtained for each region. The data were analyzed by one- and two-way ANOVA, and Fisher's PLSD (P < 0.05). The appearance of the conditioned dentin varied according to dentin region and conditioner. For Single Bond, thick hybrid layers (3-4 microm) were observed, while thin hybrid layers (less than 0.5 microm) were observed in Clearfil Liner Bond 2V for all regions.

Analysis of Variance↗
PubMedDate not supplied

Effective bond strength of current adhesive systems on deciduous and permanent dentin.

PURPOSE: To evaluate the bond strength of a total-etching, self-priming system (Single Bond) and a self-etching system (Clearfil SE Bond) to deciduous and permanent human dentin. METHODS AND MATERIALS: Buccal dentin discs were prepared with a diamond disc from permanent first premolars, permanent third molars and deciduous second molars. The flat dentin surfaces were obtained by polishing with wet 600 grit silicon carbide papers. The specimens of each group were further divided into two groups for bonding to either Single Bond or Clearfil SE Bond. After 24 hours, the microshear bond strength testing was executed on a universal testing machine. Statistical analysis was performed at alpha = 0.05. RESULTS: No significant differences in bond strength were found between materials. However, deciduous dentin demonstrated significantly lower bond strengths than permanent premolar dentin when Single Bond was applied (p < 0.05). CONCLUSION: The difference in bonding substrate (permanent or deciduous dentin) had a significant effect on bond strength when the total-etching, self-priming system was applied.

Acid Etching, Dental↗
PubMedDate not supplied

Treatment of fluorosed and white-spot human enamel with calcium sucrose phosphate in vitro.

A number of treatments have been devised to improve the appearance of fluorosed enamel. However, many of these have been empirically based, and the success of the various treatment regimens have not been quantitated. In this study, the relative whiteness of normal, mildly fluorosed, moderately fluorosed, and carious white-spot lesions on extracted teeth was quantitated by light reflectance using a Minolta Chroma Meter. The color was again determined following a number of treatment regimens to assess the potential use of various agents in treating the enamel lesions. Treatment of the enamel with a 35% hydrogen peroxide gel resulted in a significantly increased whitening, which was not reduced by subsequent treatment (P < 0.05). Removal of the enamel surface with a dental bur, followed by treatment with 5.25% sodium hypochlorite and placement in an artificial saliva was successful for returning white-spot lesions to a normal enamel color. Treatment of enamel with 5.25% sodium hypochlorite followed by calcium sucrose phosphate paste and placement in artificial saliva was most successful in returning both white-spot and fluorosed lesions to a normal color. SEM imaging of the calcium sucrose phosphate treated enamel suggests that this treatment filled the porous enamel, resulting in a normal light reflectance from the enamel.

Calcium Phosphates↗