Adhesive bonding of various materials to hard tooth tissues. 3. Bonding to dentin improved by pre-treatment and the use of surface-active comonomer

Effect of Modified Triple-Layer Application on the Bond Strength of Different Dental Adhesive Systems to Dentin

The goal of this article was to assess the effect of modified triple-layer application (MTLA) in conjunction with the active bonding technique on the bond strength of four adhesive systems to dentinal substrate. The adhesives tested were Prime&Bond Universal (PBU), OptiBond Universal (OBU), OptiBond FL (OBFL), and Clearfil SE (CSE). The adhesives were applied according to the following strategies: single active application (A) and triple adhesive layer application including Active-Passive-Passive (APP); AAP; and AAA. The micro-tensile bond strength test was evaluated following 24 h or 6 months of storage. The composite-dentin interface morphology was investigated using scanning electron microscopy. The data were statistically analyzed with a significance level of α = 0.05. At 24 h of aging, all of the factors tested were not significant (p > 0.05) for CSE. For OBFL, OBU, and PBU, statistically higher values were observed for the A technique (p < 0.05). Plus, there were no significant variances between the APP, AAP, and AAA techniques (p > 0.05) for OBFL and PBU. However, for OBU, there were no significant differences between the A and AAA techniques (p > 0.05). After 6 months of aging, the A technique showed statistically higher values when compared to the other techniques (p < 0.01), except for OBFL, where the A and AAA techniques showed promising outcomes. When comparing the bond strength values of 24 h and 6 months, only for PBU, all of the techniques used resulted in bond strength stability over time (p > 0.05). Thicker adhesive layers were observed when MTLA was applied. Only the OBFL adhesive showed the formation of resin tags in all of the modalities tested. The bonding performances of the different application techniques used were material-dependent.

Ormocer: An aesthetic direct restorative material; An in vitro study comparing the marginal sealing ability of organically modified ceramics and a hybrid composite using an ormocer-based bonding agent and a conventional fifth-generation bonding agent

AIMS AND OBJECTIVES

To compare the marginal sealing ability of ormocer with a hybrid composite using an ormocer based bonding agent and a conventional fifth generation bonding agent.

MATERIALS AND METHODS

Fifty four human premolars were randomly distributed into four test groups of 12 teeth each and two control groups of 3 teeth each. Class I occlusal preparation of 1.5 mm depth were made in each tooth. These were restored using the adhesive and restorative material according to the group. The restorations were finished using a standard composite finishing and polishing kit. Thermocycling between 5° C and 55°C was carried out. Having blocked the root apex and the entire tooth surface except 1 mm around the restoration margin, the teeth were immersed in 2% methylene blue for 48 hours, after which the dye penetration through the margins of each sample was studied under a stereomicroscope.

RESULTS AND DISCUSSION

Group IV (Admira with Admira Bond) showed the minimum marginal leakage with a mean of 0.200 mm. Four samples in this group showed no microleakage at all and a maximum of 0.400 mm was seen in one sample. Group II (Spectrum TPH with Admira Bond) showed the maximum leakage with a mean of 0.433 mm. One sample showed as much as 1.00 mm of microleakage. Admira when used with Admira Bond showed lesser microleakage than Spectrum TPH used with Prime & Bond NT, the difference being statistically insignificant.

Application of hydrophobic resin adhesives to acid-etched dentin with an alternative wet bonding technique

Hydrophilic dentin adhesives are prone to water sorption that adversely affects the durability of resin-dentin bonds. This study examined the feasibility of bonding to dentin with hydrophobic resins via the adaptation of electron microscopy tissue processing techniques. Hydrophobic primers were prepared by diluting 2,2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl] pro- pane/triethyleneglycol dimethacrylate resins with known ethanol concentrations. They were applied to acid-etched moist dentin using an ethanol wet bonding technique that involved: (1) stepwise replacement of water with a series of increasing ethanol concentrations to prevent the demineralized collagen matrix from collapsing; (2) stepwise replacement of the ethanol with different concentrations of hydrophobic primers and subsequently with neat hydrophobic resin. Using the ethanol wet bonding technique, the experimental primer versions with 40, 50, and 75% resin exhibited tensile strengths which were not significantly different from commercially available hydrophilic three-step adhesives that were bonded with water wet bonding technique. The concept of ethanol wet bonding may be explained in terms of solubility parameter theory. This technique is sensitive to water contamination, as depicted by the lower tensile strength results from partial dehydration protocols. The technique has to be further improved by incorporating elements of dentin permeability reduction to avoid water from dentinal tubules contaminating water-free resin blends during bonding.

Shear bond strength of experimental methacrylated beta-cyclodextrin-based formulations

Previous studies have shown that methacrylated beta-cyclodextrins (MCDs) can be used as comonomers in resin-based dental composites. These MCDs by virtue of having several polymerizable methacrylate groups and hydrophilic hydroxyl groups, may also promote bonding of dental composites to dentin. This study evaluated MCDs as adhesive comonomers, and optimized comonomer and polymerization initiator concentrations for maximum shear bond strength (SBS). Experimental MCD-based bonding formulations in acetone were prepared by mixing 33 mass fraction % MCDs with (10, 20, 30, 40, or 50) mass fraction % of 2-hydroxyethyl methacrylate (HEMA). The MCD/HEMA-based solutions were activated with varied amounts of camphorquinone (CQ) and ethyl 4-dimethylamino benzoate (4E). Samples for SBS were prepared by bonding a composite resin to acid-etched dentin surfaces of extracted human molars with the experimental bonding solutions. The specimens were immersed in 37 degrees C water for 24 h and bond strengths were determined in shear mode. With increasing HEMA concentration, the SBS values of MCD-bonding solutions increased to 16 MPa at a composition of 33% MCD, 30% HEMA, and 37% acetone by mass. Also, SBS values of MCD-bonding solutions varied as a function of the CQ and 4E concentrations and passed through a maximum SBS at 21 MPa, which was comparable to that of a commercial control. This preliminary study indicated that nonacidic MCD monomers could be used as an adhesion-promoting comonomer. Additional modification of MCDs having both polymerizable groups and anionic ligand groups, e.g., polymerizable acidic cyclodextrin derivatives should increase the SBS even further.

A modified direct technique versus conventional direct placement of brackets: in vitro bond strength comparison

Bond strength and failure location were evaluated in vitro for two methods of direct bracket bonding. Sixty human premolars were divided into two groups of 30 each. In group I the brackets were bonded with a two-paste adhesive by using the conventional direct method. In group II brackets were bonded with a newly developed modified direct technique. During the modified direct technique, unfilled resin catalyst liquid was applied to a bracket, which had a coating of hardened composite cured against a dental anatomic matrix (tooth). After the acid-etched tooth was coated with unfilled resin base liquid, the bracket was placed. Mixed unfilled resin liquid (sealant) was then placed at the periphery of the bracket/tooth interface. Thus the major modification of the direct technique would entail fabrication by the manufacturer of a bracket with prehardened bis-GMA composite resin on its backing. Bond strengths were 155.2 (SD = 35.7) and 140.6 (SD = 30.1) kg/cm2 for conventional and modified techniques, respectively. With the conventional method, failure occurred mainly at the tooth/composite interface. Failure seen with the modified technique was mixed, but the major mode was composite/bracket. Therefore this modified bonding method promises similar bond strengths and some advantages over the conventional method including, elimination of composite flash from around the brackets, ample working time, consistent adhesive thickness, and reduction of porosity.

Microleakage of composite resin cores treated with various dentin bonding systems

Composite resin post and cores have gained widespread acceptance as an alternative for cast-gold post and core systems. A prefabricated metal post is generally used. Substantial microleakage at the interface between the composite resin core and the dentin substrate may occur. A tight and impervious bond between the dentin and the restorative material is critical for the longevity of core restorations. This study compared the microleakage of composite resin cores treated with various dentin bonding agents, including the recently developed Gluma, Tenure, and Scotchbond 2. The results indicated that Tenure and Scotchbond 2 bonding agents were most effective in reducing microleakage, followed by Gluma and conventional Scotchbond (Dual Cure) bonding agents. Although all proprietary dentin bonding systems used in this study significantly reduced microleakage, no system was capable of preventing microleakage completely.

Development of an adhesive system for bonding to hard tooth tissues

The development of an adhesion system for bonding dental composites to dentin and enamel is reviewed. Building on findings concerning adhesion to enamel, a field pioneered by Dr. Michael Buonocore and others, Dr. R.L. Bowen and his colleagues at the Paffenbarger Research Center, National Institute of Standards and Technology, began addressing and solving problems associated with (1) silicate cements and unfilled resins, (2) bonding in an aqueous environment, and (3) the development of an adhesion system for both dentin and enamel that could withstand various stresses. Although commercial products based on this adhesion system are currently available in the dental materials marketplace, experimentation continues, focusing on the synthesis of potentially better component analogs, the optimization of the individual components, and on improved storage stability and ease of synthesis.

An investigation of shear bond strengths of various resin-bonded inner surface rest seat designs for removable partial dentures

Results and conclusions that can be drawn from this study are: All smooth, mesh, and seating preparation groups produced mean bond strengths significantly greater than that of the control group (p less than 0.01). The cast mesh rest seats exhibited significantly greater bond strengths at 24 hours (p = .0072). However, at 30 days, statistically significant differences between the three groups were not evident. Mean bond strengths for the electrolytically etched rest seat groups increased significantly at 30 days compared with the 24-hour means (p less than .05). These results suggest that an electrolytically etched resin-bonded rest seat can easily withstand the functional stresses exerted by a removable partial denture. The incorporation of seating preparation on an abutment tooth for an etched resin-bonded lingual rest seat seems to offer no advantage in terms of retentive strength.

Effect of ethanol and NPG-GMA on replica patterns on composite restorations performed in vivo in acid-etched cavities

29 experimental Class V restorations using a chemically cured composite resin were inserted in human third molars in cavities which after acid-etching had been treated with absolute ethanol. After extraction and demineralization of the teeth, the fillings were examined in SEM concerning their enamel and dentin replica patterns on the inner cavity-faced surface. The SEM findings were compared with previous findings concerning the replica patterns on fillings from acid-etched cavities and from cavities which after acid-etching had been treated with an ethanol solution of the surface active comonomer N-phenylglycine-glycidyl methacrylate (NPG-GMA). It was found that cavity treatment with absolute ethanol further improved the increased enamel replica patterns obtained with the NPG-GMA/ethanol comonomer solution while only the NPG-GMA/ethanol treatment improved the dentin replica patterns. Based on these results the effect of each of the two main components in the comonomer solution on replica patterns on resin restorations could be disclosed.

Adhesive bonding of various materials to hard tooth tissues: improvement in bond strength to dentin

Used in sequence, solutions of an acidic mordant, a surface-active comonomer, and a coupling agent having methacrylate and aromatic carboxyl groups were used to prepare dentin surfaces in vitro for strong bonding with a composite resin.

Dentin permeability: effects of smear layer removal

The results of this study permit the following conclusions: 1. The use of dilute (6%) citric acid for very short time intervals permits sequential removal of the smear layer on human dentin. 2. Acid-etching for as little as 5 seconds removes much of the smear layer and exposes the orifices of dentinal tubules. 3. Dentin permeability increased rapidly during acid-etching with 6% citric acid, reaching a maximum value after only 15 seconds of etching. 4. The production of a smear layer on dentin during restorative procedures establishes a protective diffusion barrier. Removal of the smear layer by acid-etching increases the permeability of dentin which, under some conditions, must be regarded as a liability.

The accelerative and adhesive bonding capabilities of surface-active accelerators

PolySAM-1, a multifunctional surface-active amine polymerization accelerator, and several simpler surface-active amine promoters were evaluated for their accelerative and adhesion-promoting potentials. Diametral tensile strength measurements, performed on composites prepared from a bis-GMA resin formulation with tribasic calcium phosphate as the filler, were used to assess the adhesive bonding capabilities of these amines.

Adsorption of N-(2-hydroxy-3-methacryloxypropyl)-N-phenylglycine (NPG-GMA) on cupric ion-enriched hydroxyapatite surface to improve chemical bonding between dental resins and teeth

In continued studies of chemical bonding between a polymer and teeth through the mediation of coupling agents, the absorption of N-(2-hydroxy-3-methacryloxypropyl)-N-phenylglycine (NPG-GMA) from ethanol solution was studied on cupric ion-treated synthetic hydroxyapatite in order to discriminate the adsorptive behaviour of the 'mordanted' as against the unmordanted (or pure) apatite. All features of the adsorption isotherm, however, agree with those of the isotherm obtained on pure hydroxyapatite. Also, polymer filled with cupric ion-treated hydroxyapatite coated with the irreversibly adsorbed NPG-GMA has a tensile strength comparable to that of the polymer filled with NPG-GMA coated pure hydroxyapatite.

Influence of a ferric chloride mordant solution on resin-dentin retention

The effects of ferric chloride mordant solution, two cleansing solutions, and three chemical adhesion promoters were examined on resin-dentin adhesion. Adhesion was increased with the use of ferric chloride solution. An NPG-GMA or butyl acrylate-acrylic acid copolymer type of adhesion promoter also increased resistance to shear separation.

Effects of surface treatments on the retention of restorative materials to dentin

The effect of various pretreatments on shear bond strengths between dentin and three restorative materials was investigated. Pretreatments included use of cleansing agents and adhesion promoters in combination. Results indicated that: (1) phosphoric acid (50%) and EDTA (10%) were not effective in improving bonding between restorative materials and dentin; (2) NPG-GMA significantly increased resin-dentin adhesion with Cervident and Simulate resin. Silane adhesion promoter in combination with Fuji provided the greatest resistance to shear forces; and (3) Fuji Type II restorative material demonstrated more resistance to shear forces than Cervident and Simulate resins.

Adhesive bonding of various materials to hard tooth tissues. XXII. The effects of a cleanser, mordant, and polySAC on adhesion between a composite resin and dentin

Preliminary evaluations on the effects of a cleanser, mordant, and polyfunctional surface-active comonomer on adhesion between a composite resin and dentin evinced that the ferric chloride mordant significantly improved bonding. The effects of the cleaner and coupling agent were also favorable, as were all of their interactions.

Effect of cyanoacrylate treatment of cavity walls

Cyanoacrylate treatment of the cavity wall for composite resin restoration failed to keep adhesion when set, but the marginal closure improved markedly both in vivo and vitro, even when thermal-cycled. It irritated the pulp slightly only at the beginning. Ethylcyanoacrylate was superior to methylcyanoacrylate in regard to adhesion, leakage and pulp response.

Isocyanato urethane methacrylates derived from hydroxyethyl methacrylate

Isocyanato urethane methacrylates were synthesized from five diisocyanates and hydroxyethyl methacrylate. They may be homopolymerized or copolymerized with other methacrylates by the usual free radical methods of initiation and have potential as adhesion-promoting agents for dentin.

Character of the hard tooth tissue-polymer bond. II. Study of the interaction of human tooth enamel and dentin with N-phenylglycine-glycidyl methacrylate adduct

The interaction of powdered human tooth enamel and dentin with NPG-GMA was studied in alcoholic and alcoholic-aqueous solutions. The reaction produces ionized carboxylic groups capable of forming ionic bonds between the calcium ions in the tooth enamel or dentin and NPG-GMA.

Character of the hard tooth tissue-polymer bond. I. Study of the interaction of calcium phosphate with N-phenylglycine and with N-phenylglycine-glycidyl methacrylate adduct

A model investigation was carried out to establish the chemical character of the bond between hard tooth tissues and polymeric materials. The interaction of NPG and NPG-GMA with Ca3(PO4)2 and 45Ca3(PO4)2 was studied in aqueous, alcoholic and aqueous-alcoholic solutions. It was shown that NPG and NPG-GMA react in solution with Ca ions which are in equilibrium with calcium phosphate. The reaction proceeds more intensively in aqueous-alcoholic medium due to its ionic character. The IR spectra of the reaction products show the presence of NPG-GMA calcium salt.

Compatibility of various materials with oral tissues. I: The components in composite restorations

The basic ingredients in composite restorative materials include: monomers, polymerization stabilizers, color stabilizers, polymerization initiators, polymerization accelerators, inorganic reinforcing fillers, and coupling agents. Typical members of each category are discussed.

Aldehyde methacrylates derived from hydroxybenzaldehydes

Three crystalline aldehyde methacrylates with low melting points were synthesized from the readily available, isomeric hydroxybenzaldehydes and 2-bromoethyl methacrylate. These monomers can be purified by recrystallization and liquified by admixture in various proportions to obtain polymerizable liquids having workable viscosities at room temperature. These monomers may be used alone or as blends with other methacrylates since they are miscible and copolymerizable with the usual dental monomers. Also, they should be studied with other functional methacrylates designed to promote adhesion via the mineral phase to determine if this synergistic approach can improve the adhesion of dental resins to dentin. These aldehyde methacrylates, their mixtures, polymers and copolymers merit evaluation as adhesion-promoting agents for proteinaceous substrates such as bone and dentin.

Metal-filled resin composites. II

Various particulate materials were combined with a BIS-GMA resin, and the resulting composites were evaluated. The fillers prevented, altered, had no apparent effect, or accelerated polymerization. Coupling agents also influenced polymerization. Physical properties varied widely with different fillers.

Fracture studies of adhesion

Controlled fracture techniques were successfully applied to the study of adhesion. A new parameter, interfacial work of fracture (Wi), was defined and measured for porcelain-gold specimens and for enamel-composite specimens. Wi measurements coupled with factographs indicated that a "highly etched" enamel surface may not give the strongest bond.

Adhesive bonding of various materials to hard tooth tissues: XIII Synthesis of a polyfunctional surface-active amine accelerator

Surface-active amine polymerization accelerators can be prepared by the reaction of polyepoxy resins with the sodium salt of N-phenylglycine and N-methyl-p-toluidine. These materials are expected to promote adhesion through complexation with surface calcium (or other metal ions), utilizing several chelating groups per molecule, and by functioning as polymerization accelerators for dental resins; they can also function as catalysts for the anionic polymerization of cyanoarylate monomers.

Investigation of adhesive properties of dental composite materials using an improved tensile test procedure and scanning electron microscopy

A standardized tension test was used to evaluate the adhesive properties of several composite materials when used on both dentin and enamel specimens. The nature of the test surfaces was examined by roughness tests using a Talysurf machine and also in more detail by means of a scanning electron microscope. Poor results were obtained for the adhesion of composite materials to dentin whereas good retention to enamel was obtained.

Human pulp response to acid pretreatment of dentin and to composite restoration

The newer composites, although free of methacrylic acid and of a neutral pH, were still found to be toxic to the pulp. The intensity of response was increased after acid pretreatment procedures; this indicates an increase in dentin permeability. When the remaining dentin thickness was 1.0 mm or less, regardless of whether the dentin was primary dentin or primary and reparative dentin, the percentage of teeth with abscess formations increased. Use of calcium hydroxide bases or liners to coat the dentin before acid pretreatment of enamel is therefore highly recommended.

Tensile bond strength between fissure sealants and enamel

Acrylic buttons were attached to tooth enamel by in situ curing of three types of polymeric fissure sealants, a dental cement, and a glass ionomer cement and then were immersed in water. The polymeric materials exhibited the greatest bond strengths to enamel, but in two instances the bond strength decreased with time although the cements showed increased strength. One polymeric material exhibited an unchanged bond strength.

Bonding of alkyl 2-cyanoacrylates to human dentin and enamel

The influence of water immersion and acid etching on the bonding of methyl, ethyl, a thickened ethyl, and isobutyl 2-cyanoacrylates to human enamel and dentin was studied. In general, the ethyl and isobutyl homologues gave the strongest, most durable bonds. Adhesion to dentin is probably the result of chemical combination.

Surface topography: its influence on wetting and adhesion in a dental adhesive system

The fracture surface between bovine dentin and enamel and a dental cement was observed at magnifications up to 10,000× by use of the scanning electron microscope. The topography of the tooth structure played an important role in the formation of an adhesive bond and in the fracture pattern of an adhesive joint, even when cohesive failure was involved.