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PubMed1995

The composition and ultrastructure of resin tags in etched dentin.

PURPOSE: To examine in vitro the composition of resin tags in etched dentin by SEM and vital staining using Alcian Blue dye. MATERIALS AND METHODS: Bovine and human teeth were used. The dentin surface was exposed using water-irrigated #600 grit SiC paper and etched with varying dilutions of aquaeous solutions of phosphoric and maleic acid. Groups of 10 teeth per acid concentration were embedded in PMMA and Scotchbond Multi-Purpose (SMP) and cylinders of Z100 resin composite were bonded to their surfaces. These teeth were shear tested to failure and the failed surfaces subjected to SEM. Groups of three teeth per acid concentration had SMP and cylinders of Z100 bonded to their surfaces. These teeth were decalcified in concentrated HCL acid. The resultant cylinders and their attached resin tags were either subjected to SEM or stained with Alcian Blue dye. The latter specimens were embedded and prepared for light-microscopic examination. A further three human and three bovine teeth per acid concentration were etched and then prepared for SEM examination. All teeth for SEM were critical point dried. RESULTS: Resin tags were shown to consist of both resin and the glycosaminoglycans (GAG) sheath lining of the dentin tubule. As a result of the SEM observations, three mechanisms are suggested for the formation of resin tags, two of which will probably be found in vivo.

Acid Etching, Dental↗
PubMed1995

Bonding mechanism of VariGlass to dentin.

PURPOSE: This study investigated the hypothesis that the new resin-reinforced, light-cured ionomer cement (GIC) can develop mechanical retention by forming a hybrid layer in acid-etched dentin. MATERIALS AND METHODS: Dentin discs were obtained from extracted human third molars and sanded with 320 SiC abrasive paper. One third of the surface was acid etched with 10% maleic acid for 15 seconds, washed and gently air-dried for 5 seconds. ProBond primer from the VariGlass (VG) GIC kit was applied onto the acid-etched surface (A) and another third of the unetched surface (B) for 30 seconds. One third of the surface was not treated (C). VG GIC was then applied onto the ++entire surface of the disc. After 24 hours the discs were fractured along their diameters. One half of the fractured disc was highly polished at the interface and treated with 6N HCl for 30 seconds while the other half of the fractured specimen was left untreated. Both halves were viewed by SEM. In another part of the study, a micro-tensile bond strength (MTBS) test was carried out to compare the acid-etched group vs. the nonetched group. RESULTS: SEM pictures revealed a well defined demineralized, resin-infiltrated zone approximately 3 micrometers in thickness for group (A) for both fractured and polished surface. Dentin surfaces that only received primer (B) showed an irregular zone 0.5 micrometers thick. Such a resin-infiltrated layer was resistant to HCl treatment. A gap was observed between the GIC and dentin in group (C). Polished interfaces appeared to be highly infiltrated. However, fractured interfaces revealed considerable porosity within the demineralized-infiltrated zone. MTBS results were (X +/- SD, MPa): 28.9 +/- 5.8 for the etched group and 24.5 +/- 4.9 for the nonetched group. This difference was statistically significant.

Acid Etching, Dental↗
PubMed1995

Interfacial morphology and strength of bonds made to superficial versus deep dentin.

PURPOSE: To evaluate the interfacial morphology (SEM) of two bonding systems to superficial and deep dentin using a reverse-sandwich technique, coupled with measurement of micro-tensile bond strengths (MTBS). MATERIALS AND METHODDS: Superficial and deep dentin disks were prepared from the same tooth in freshly-extracted human third molars. All-Bond 2 (total etch versus no etch) or Imperva Bond (total etch versus no etch) were applied to superficial versus deep dentin surfaces and the two disks were bonded together into a reverse-sandwich configuration. RESULTS: SEM revealed that All-Bond 2 and Imperva Bond applied under total etch conditions formed thicker resin-infiltrated layers (4-8 micrometers) on deep dentin than on superficial dentin (2-4 micrometers), and that All-Bond 2 and Imperva Bond applied to unetched dentin formed very thin resin-infiltrated layers (less than 0.5 micrometers) on both dentin substrates. MTBS of All-Bond 2 and Imperva Bond were more than 20 MPa irrespective of dentin depth and were not significantly different. Without acid etching, the MTBS of both systems to deep dentin was significantly lower than to superficial dentin. These results suggested that for the total-etch systems, dentin depth affected the thickness of the resin-infiltrated layer, but the thickness of the resin-infiltrated layer had no significant relationship with MBTS. The present data also indicated that the acid-etch technique could prevent the decrease of bond strength seen in deep dentin in the absence of etching.

Acid Etching, Dental↗
PubMedDate not supplied

Nanoleakage: leakage within the hybrid layer.

Most microleakage studies involve quantitating the magnitude of movement of a tracer molecule through a gap between restorative materials and the wall of cavity preparations. The present microscopic study examined the migration of silver nitrate into the interface between dentin and five different dentin bonding agents used to restore class 5 cavities, in the absence of gap formation. Several different leakage patterns were seen, but they all indicated leakage within the hybrid layer when viewed by SEM. The ranking of microleakage from most to least was: All-Bond 2 > Suberbond C&B > Scotchbond Multi-Purpose > Clearfil Liner Bond System > Kuraray Experimental System, KB-200. To distinguish this special type of microleakage within the basal, porous region of the hybrid layer in the absence of gap formation, we propose the term nanoleakage.

Analysis of Variance↗
PubMedDate not supplied

Comparative SEM and TEM observations of nanoleakage within the hybrid layer.

Most adhesive interface studies have involved SEM demonstration of the penetration of adhesive resins into demineralized dentin surfaces with subsequent creation of hybrid layers. Nanoleakage is a term that describes the diffusion of small ions or molecules within the hybrid layer in the absence of gap formation. The present microscopic study examined the nanoleakage of the hybrid layer using a silver nitrate staining technique. Adhesive dentin sandwiches, which were immersed in a silver nitrate solution, were prepared for both SEM and TEM examination using both the Clearfil Liner Bond and All-Bond 2 adhesive systems. Both systems demonstrated silver accumulation within the hybrid layers. Clearfil Liner Bond System showed scattered silver particles at the bottom two-thirds of the hybrid layer by both SEM and TEM observation, whereas All-Bond 2 revealed stained fiber-like structures within the full thickness of the hybrid layer. To evaluate the quality of the hybrid layer, the utilization of tracer molecules such as silver nitrate that are detectable by both SEM and TEM is proposed. It is important to determine the location and morphology of these nanometer-sized porosities that may permit the hydrolysis of collagen fibers and degradation of adhesive monomers.

Collagen↗
PubMed1996

The overwet phenomenon: a transmission electron microscopic study of surface moisture in the acid-conditioned, resin-dentin interface.

PURPOSE: To identify ultrastructural features resulting from possible primer-water interaction when a two-bottle, acetone- and alcohol-based dentin adhesive (All-Bond 2) was applied to acid-conditioned dentin in the presence of excess water. MATERIALS AND METHODS: Three groups (3-second dry, visibly moist, overwet), each comprising eight dentin discs prepared from human third molars, were established and bonded with All-Bond 2 under different degrees of surface moisture. Variations in the ultrastructural appearance of the resin-dentin interface from laboratory demineralized and epoxy resin embedded disc pairs were examined either with en bloc ruthenium red pre-staining alone or further stained with uranyl acetate and lead citrate. RESULTS: Displacement of water by the volatile primer solvents resulted in the formation of a layer of resin-impregnated dentin in the three groups. Interaction of the primer with water following the evaporation of the volatile primer solvents resulted in phase separation of the primer components. Ultrastructural features observed within the previously water-filled blister-like spaces on the dentin surface in the visibly moist and overwet groups recapitulated what was observed within partially water-filled dentin tubules in the 3-second dry group. The overwet phenomenon appeared to be a result of emulsion polymerization, involving irreversible interaction of water-soluble bifunctional primer components with those that are water-immiscible, through the formation of micelles, resulting in the absence of total interfacial integrity.

Acid Etching, Dental↗
PubMed1996

The interaction of adhesive systems with human dentin.

PURPOSE: To investigate the interaction of six experimental and commercial bonding systems with dentin in vivo. MATERIALS AND METHODS: One-Step, Clearfil Liner Bond 2, OptiBond, Permagen with 10% phosphoric acid, Permagen with 35% phosphoric acid, and Prime & Bond were applied in standard Class I occlusal cavities in premolars scheduled for extraction for orthodontic reasons, combined either with a self-cured or with a light-cured resin composite. The teeth were carefully extracted 5 minutes after resin polymerization and fixed in 2.5% glutaraldehyde. After fixation, the specimens were dehydrated, sectioned, and processed for field-emission SEM. RESULTS: Although some systems produced gap-free intact interfaces in specific specimens, all of them showed detachment at the transition between the resin-dentin interdiffusion zone and the fluid resin placed over it. It was apparent that the presence of air-bubbles and/or thick layers of polymerized-filled fluid resin resulted in less frequent separation areas at the resin-dentin interface, providing support for the concept of the elastic cavity wall. It was also confirmed that some dentin adhesive systems do not form a thick layer over the dentin, otherwise the resin composite would not have penetrated the dentin tubules.

Adolescent↗
PubMed1996

The overwet phenomenon: a scanning electron microscopic study of surface moisture in the acid-conditioned, resin-dentin interface.

PURPOSE: To study with the scanning electron microscope the interfacial phenomenon that occurred in the presence of excessive surface moisture following the application of an acetone-based adhesive to acid-conditioned dentin. MATERIALS AND METHODS: Specimens consisted of flat dentin discs that were divided into three groups based upon the status of remaining surface moisture: (1) 3-second dry group, (2) blot-dry group, with the conditioned dentin surface remaining shiny as opposed to matte, and (3) overwet group: an additional 40 mL of distilled water spread thin on the dentin surface after blot-drying. Polished resin-dentin interfaces were brought into relief using plasma-etching and examined without further embedding. RESULTS: Although a hybrid layer was observed in all three groups, there was (1) a sequential deterioration of the bonded assembly along the hybrid layer-resin interface, and (2) loss of complete tubular seal as the quantity of surface moisture increased. Intratubular resin globules were observed beneath short resin plugs in the 3-second dry group. Small, isolated blister-like spaces, trapped within the resin layer, were observed along the surface of the hybrid layer in the blot-dry group, while similar, but larger spaces were found in the overwet group. The blister-like spaces, which were often continuous with incompletely sealed tubular orifices, were partially filled with extraneous resin globules dispersed within an amorphous matrix.

Acid Etching, Dental↗
PubMed1994

The morphology of the demineralized layer in primed dentin.

This study critically examined the surface and subsurface effects of selected dentin priming agents. Various dentin priming agents were used and specimens were prepared for SEM examination by conventional air drying or by a freeze fracture and critical point drying technique. The results showed that in specimens prepared by freeze fracture and critical point drying technique the demineralization of the dentin surface and subsurface by priming agents leaves a visible network of collagen fibrils. This technique allows better evaluation of the adaptation of bonding resins to the collagen network of the demineralized layer.

Acid Etching, Dental↗
PubMed1994

Effect of wettability of adhesive resins on bonding to dentin.

The purpose of this study was to investigate on human dentin the relationships between, on the one hand, the wettability of five adhesive compounds, characterized by different solubility parameters delta, and on the other, the thickness of the resin impregnated dentin layer (RIL) and the shear bond strength (SBS). Cut dentin surfaces were treated with conditioners of pH 1.25, 3.6 or 7.4. Shear bond strength was measured on 20 specimens each. RIL was determined by scanning electron microscope on specimens fractured perpendicularly to the bonding interface. When resins with delta 32, 30 or 39 (MJ1/2/m3/2) were used RILs were consistently 4 microns and 1 micron on dentin pretreated with the two acidic conditioners. No clearly measurable RIL was shown after application of the conditioner with pH 7.4, and when resins with delta-values of 20 and 25 were applied. For the same adhesive no difference in SBS was found, when applied on the differently conditioned dentin sites. Resins with delta > 30 produced significantly higher SBS than the two adhesives with smaller delta.

Analysis of Variance↗
PubMed1994

Bonding to etched, physiologically hydrated dentin.

This study evaluated the shear bond strengths of resin composite to dentin using Kanca's "total-etch" technique (etching with 37% phosphoric acid, application of Tenure Solutions A and B, and application of Scotchbond 2 Adhesive). Bonding was done under different conditions, to specimens with or without hydrostatic pressure. Shear bond strengths were 20.1 MPa to dentin under simulated physiologic pressure, and 15.2 MPa to dentin without pressure.

Acid Etching, Dental↗
PubMed1996

Dentin infiltration by three adhesive systems in clinical and laboratory conditions.

PURPOSE: To evaluate in vivo and in vitro the formation of hybrid layer, resin tags and adhesive lateral branches, by use of three different enamel dentin bonding systems. MATERIALS AND METHODS: The dentin adhesives were tested on flat dentin preparations made on buccal surfaces of vital, periodontally compromised teeth. The samples were randomly divided in four groups: Group 1: Prime & Bond 2.0; Group 2: Scotchbond Multi-Purpose Plus; Group 3: Clearfil Liner Bond 2 (the self-etching primer was applied for 30 seconds on the enamel and dentin); Group 4: Clearfil Liner Bond 2 (the self-etching primer was applied for 60 seconds on the enamel and dentin). The sample teeth were extracted immediately after the bonding was cured. The same procedure described for the in vivo samples was performed in vitro on extracted molars. All the samples were split-fractured along their long axis. Half of the samples were used to visualize the hybrid layer and the other half to observe the morphology of resin tags by use of scanning electron microscopy. RESULTS: All the tested products formed a hybrid layer, both in vivo and in vitro. In many areas of the samples of Groups 1, 2 and 4, characteristic reverse cone-shaped tags with their corresponding adhesive lateral branches were evident. In contrast to this, resin tags found in samples of Group 3 were narrower at the tubule orifices, and adhesive lateral branches were scarce. The length of the resin tags observed in the samples of Groups 1 and 2 were longer than those found in Groups 3 and 4. The morphology of the hybrid layer of the in vivo samples was similar to that of the in vitro samples.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1997

Ultrastructure of the resin-dentin interface following reversible and irreversible rewetting.

PURPOSE: This study investigated the effect of reversible and irreversible rewetting on the application of One-Step, single-bottle, water-free, acetone-based primer/adhesive. MATERIALS AND METHODS: Thirty 1 mm dentin discs prepared from third molars were each conditioned with 10% H3PO4 for 20 seconds and rinsed for 20 seconds. They were randomly divided into five groups: Group 1 (positive control): conditioned dentin bonded visibly moist; Group 2: bonded after drying for 3 seconds; Group 3: drying for 3 seconds and rewetting with distilled water; Group 4 (negative control): drying for 3 seconds, stored in 8% glutaraldehyde for 15 minutes, rinsed with distilled water and dried for 3 seconds; and Group 5: drying for 3 seconds, stored in glutaraldehyde for 15 minutes, rinsed with distilled water and bonded visibly moist. One-Step was applied in two coats according to the manufacturer's recommendation and discs in each group were further bonded together to form a disc-pair using a chemical cure resin, demineralized in EDTA and prepared for TEM examination. RESULTS: Complete resin infiltration into the zone of demineralized dentin was observed in Group 1 and 3. In Group 2, resin infiltration was limited to the surface and base of the demineralized network apparently along the lateral branches of the dentin tubules. A middle zone of suboptimal infiltration was observed. In Group 4 and 5, minimal resin infiltration was only observed along the base of the demineralized network upon their fixation in a collapsed state with glutaraldehyde.

Collagen↗
PubMed1996

Variation in phosphoric acid concentration and treatment time and HEMA diffusion through dentin.

PURPOSE: The effects of phosphoric acid concentration and time of dentin treatment on the movement of 2-hydroxyethylmethacrylate (HEMA) from a bonding resin-resin composite combination through dentin were investigated in vitro. MATERIALS AND METHODS: Freshly extracted human third molar teeth were divided into seven groups each of 10 teeth. A closed chamber was attached to the CEJ of each tooth to contain 1 ml distilled water. An occlusal cavity of 6 mm diameter and remaining dentin thickness of 1.0-1.5 mm was prepared in each tooth. Dentin was treated with either 10% phosphoric acid for 15, 30 or 60 seconds or with 37% phosphoric acid for 15, 30 or 60 seconds. A control group not treated with acid was also prepared. The cavities were rinsed, dried and then treated with the HEMA-containing Scotchbond Multi-Purpose bonding resin which was light-cured for 10 seconds. The cavities were then restored with Z100 and light-cured for 30 seconds. Water samples were retrieved from the chambers over a time course (4.32, 14.4, 43.2, 144 & 432 minutes; 1, 3 and 10 days) and analyzed by high performance liquid chromatography. RESULTS: HEMA was detected in the pulp chambers of all teeth from 4.32 minutes after resin placement. Mean total (cumulative) release at 10 days for all groups was in the 2-4 mumol range. The highest HEMA diffusion rate was 4.32 minutes after placement and were in the range 6-13 times greater than control in the 10%-15 seconds, 10%-30 seconds, 10%-60 seconds, 37%-15 seconds, and 37%-30 seconds groups. Unexpectedly, by far the lowest early rate at 4.32 minutes was in the 37%-60 seconds group (0.6 times of no-acid control).

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↗
PubMed1998

Early and intermediate time response of the dental pulp to an acid etch technique in vivo.

PURPOSE: To present the ultrastructural features of the pulpal responses, following the application of All-Bond 2 to acid-conditioned, deep, unexposed coronal dentin and exposed pulps in human teeth. MATERIALS AND METHODS: Cylindrical Class V cavities were prepared in human premolars. In the non-exposure group an attempt was made to prepare the floor of the cavity to +/- 0.5 mm from the pulp. In the exposure group, the pulps were intentionally exposed. After hemostasis, the preparation was etched with 10% phosphoric acid. The teeth were restored with All-Bond 2. Histological evaluation was done at 0-7, 28-35, and > 90 days. RESULTS: A typical connective tissue response to injury was observed in the majority of the specimens. Irreversible injury to the odontoblasts closest to the site of cavity preparations resulted in the death of these cells. This was followed by an early neutrophilic response, a subsequent macrophage response and a fibroblastic response that led to the deposition of either reparative dentin or calcific bridge formation by odontoblast-like cells. However, another notable feature was the consistent observation of resin particulates within the dentin-pulp complex. These resin particulates could have been indirectly introduced into the pulp through the pertubation of the junctional complexes or the death of the odontoblasts. They may also enter the pulp directly through a pulpal exposure. In some specimens, the presence of these resin particulates appeared to have triggered a foreign body response, characterized by the presence of a mononuclear inflammatory infiltrate as well as the appearance of multinuclear giant cells. The persistence of unresolved chronic inflammation was associated with the lack of calcific bridge formation in these specimens.

Acid Etching, Dental↗
PubMedDate not supplied

Resin-infiltrated dentin layer formation of new bonding systems.

The purpose of this study was to evaluate the resin-dentin interfacial morphology and shear bond strength of several new and experimental dentin bonding systems classified as single-bottle/total etch, multi-step/total etch, and self-etching. Class 1 and 5 cavities were prepared from freshly extracted permanent molars and restored with composite resin. Each bonded sample was cross sectioned and one-half was completely demineralized and deproteinized, while the other half was polished along the cut surface to permit measurement of the thickness of resin-infiltrated dentin layer (RIDL) within intertubular dentin (iRIDL) and around the peritubular walls (pRIDL) of resin tags by SEM. Shear bond strength was measured for all the systems 2 minutes after photocuring. SEM showed iRIDL and resin tags of different morphology depending on material and dentin location. The iRIDL was thinner in superficial dentin and thicker in deep dentin. Peritubular RIDL (pRIDL) was thinner than intertubular RIDL. Bond strength measurements varied from 12 to 21 MPa, depending on the materials used. Self-etching primer systems exhibited the highest bond strength, although one of the one-step/total etch systems also yielded very high values. The contribution of pRIDL to adhesion onto superficial dentin is limited by the small number of tubules. Single-component bonding agents produced SEM morphology and bond strengths similar to those of multi-step systems. Self-etching systems, despite their limited RIDL thickness, produced the highest immediate bond strengths. Bond strength did not correlate well with the thickness and morphology of RIDL.

Adult↗