Acid-etch Technique Research Articles

Direct bonding of orthodontic brackets to porcelain veneer laminates

The forces required to debond orthodontic attachments from porcelain veneer laminates were studied in vitro. Brackets were bonded to 160 veneered bovine incisor teeth before the determination of the debond force. The independent variables studied were resin type, priming agent, porcelain surface preparation, and debonding time. The average debond forces were compared with those obtained by debonding brackets bonded to natural teeth by means of the acid-etch technique. The bond between the resin and the porcelain surface was found to be satisfactory for direct bonding of orthodontic attachments. Roughening the porcelain surface and using a silane primer required an average debond force comparable to that of the acid-etched enamel bond at 24 hours. However, it increased the risk for porcelain fracture during debonding. Roughened surfaces and surfaces with micro-fractures could be satisfactorily finished and polished with either a series of graded Ceramiste points or a diamond-impregnated polishing wheel followed by a diamond polishing paste.

Continuous brushing acid-etch technique and microleakage of class V composite restorations

Continuous brushing acid-etch technique and microleakage of class V composite restorations

Composite resin restoration in esthetic dentistry

The revolution in esthetic dentistry is attributable to improvement in materials, such as composite resins. The varied types of resins can be used in many restorative situations, using an acid-etch technique for these restorations, whether Class V, labial veneer, or posterior composite restoration. Dentists who take advantage of continuing education (especially hands-on courses), learn from experience, stay informed about current materials, and exercise imagination and commitment will meet the needs of the 20th century.

Bond strength of adhesive composite resins. Part 3. Effect of acid etching techniques on dentine adhesion

Bond strength of adhesive composite resins. Part 3. Effect of acid etching techniques on dentine adhesion

The effect of an air polishing device on sealant bond strength

n L/ental sealants are considered an important component for the prevention of occlusal caries. Although the occlusal surface accounts for only 12% of the tooth surface, occlusal caries now accounts for 50% to 54% of dental caries.’ Considerable progress has been made in sealant technique and materials since the inception of the acid-etch technique.* Retention of the adhesive material is the major factor in assessing the success of bonding procedures and sealants.2 Retention of bonded material is enhanced if a highenergy enamel surface is created by removing oral contaminants. Current technique for removal of these contaminants uses a pumice-water slurry, rubber cup or brush in a slow-speed rotary handpiece followed by acid etching. Occlusal anatomy is such that cleaning of the deeper pits and fissures is difficult and the effect is primarily limited to the inclined planes.3-6 Even though acid etching removes additional contaminants on the surface enamel, the effect is again primarily on the inclined planes. Successful retention of the sealant and protection of the pit or fissure seems to be dependent on bonding of the resin to the inclined planes, forming a bridge of resin over the pit or fissure.’ The air polishing device has shown encouraging results in stain and debris removal from occlusal surfaces.’ A surface free of stain and debris may allow a greater degree of surface contact with an acid-etching solution in and near the fissure and possibly also between the fissure and the resin material. This may enhance sealant retention and/or decrease dependence of bonding to inclined planes. Sealant retention potential in laboratory studies is assessed by using tensile bond strength tests and evaluation of tag formation. Studies by Brockmann and Scott* substituting air polishing for traditional pumice-water slurry cleaning showed higher bond strengths and greater numbers of tag formation although there was not a statistically significant difference between the means of the two groups. The studies did not include testing tensile bond strength after periods of water immersion. Additional testing after such immersion is a logical step

The influence of enamel prism orientation on leakage of resin-bonded restorations.

A new method is described for the quantification of leakage between etched enamel and restorative resin. A significant correlation was demonstrated between the plane of enamel section prior to etching and subsequent leakage. It is suggested that these findings will be of value in the design of cavities for use with the acid-etch technique; when possible, enamel should be prepared to expose prisms transversely prior to etching and bonding.

The continuous brushing acid-etch technique

The continuous brushing of an acid-etching agent onto the enamel surface of an extracted tooth resulted in a more debris-free surface. SEM photomicrographs showed dissolution of some of the apatite crystals and a reduction in size of the remaining crystals, thus increasing the potential space between them for retention of unfilled composite.

Chemical changes and surface morphology of acid-etching of human enamel treated with topical fluoride agents in vitro.

The fluoride (F) uptake by, and the appearance of polished human enamel which was exposed to topical F agents directly or via an artificial membrane was studied in vitro. The topical F agents used included Duraphat® varnish, Gelution® APF gel and an experimental alginate-based formula (EF), which were applied for 5 min. In addition, Duraphat was applied for 24 h and the uptake of F by sound enamel treated for 5 min with EF was tested. The uptake of F was assessed by three successive layers sampled from experimental and control enamel using the acid-etch technique. All topical F agents increased the F concentrations in almost all depths of the membrane-uncovered enamel and to a level significantly higher than in the control group. The F uptake by membrane-covered enamel was mostly confined to the first depth of 2.5 μm. Application of Duraphat for 24 h significantly increased the F concentration compared with 5 min of treatment (p brief washing and the acid-etch procedures.

In vivo adaptation of restorative materials to dentin

lhe enamel acid-etch technique is an integral restorative procedure for composites. It improves marginal adaptation and retention and reduces marginal leakage.’ However, bacterial invasion from the oral environment can still occur at the cavity margins.‘,’ In clinical practice the gingival margin is a weak link. Occurrence of prismless enamel or an exceedingly thin layer of enamel makes the use of the acid-etching technique impossible. Increased marginal leakage can occur. Intensive research on adhesion to dentin started 20 years ago.’ Adhesive bonding to dentin requires removal of the smear layer. The use of cavity cleansers and etching agents has been suggested, although these can enhance the pulpal response.‘,” However, other studies show that acid pretreatment per se did not cause pulpal injury.‘, R Etching the dentin with 37% phosphoric acid for 15 to 60 seconds removes the amorphous smear layer and dissolves the dentin.’ Resin tags penetrating the dentinal tubules have been reported.’ ‘)-‘I These tags can possibly serve as mechanical retention for the restoration. However, dentinal tags do not assure a permanent, serviceable adaptation of the restorative material to the cavity walls in vivo. The tags initially penetrate the dentinal tubules but tend to withdraw because of contraction and stresses. Recently developed commercial dentin bonding agents show reduced leakage and increased bond strength to acid-etched dentin in vitro.‘z”5

Etching and the morphology of branched and cross-linked polyethylene

A permanganic acid etching technique was used to characterize the genuine morphologies of bulk crystallized samples of linear, branched, and crosslinked polyethylene. Four different kinds of artifacts as large as 15–20 μm were detected. It was also noted that artifact density could be drastically reduced by proper selection of etching conditions. The morphologies of artifacts were independent of specimen crystallinity and the orientation of lamellar crystals; however, their rate of production was susceptible to the crystallinity of samples. The formation of a fresh surface involved the preferential etching of edge-on and secondary lamellae. As the growth features of cross-linked polyethylene were less than 6 μm and were mainly sheaf-like structures, growth features could be readily distinguished from the artifacts by transmission electron microscopy. Another type of artifact (globules morphology) produced at angstrom scale was found to depend on the crystallinity and the surface structure of lamellar crystals. It is demonstrated that the fine lamellar details of branched and cross-linked polyethylene can be observed using transmission electron microscopy. Increasing the number of cross-links in polyethylene, modifies the size and nature of supermolecular structures, the periodic twisting of lamellar crystals, and the nature of the nucleation process. The study of a blend of branched and cross-linked polyethylene showed that the structurally dissimilar molecules co-crystallized at low crystallization temperatures, while there is a tendency for molecular fractionation at higher crystallization temperatures.

Direct bonding comparing a polyacrylic acid and a phosphoric acid technique

The purpose of this study was to compare in vitro a polyacrylic acid technique (crystal bonding) with a conventional phosphoric acid-etch technique for the preparation of teeth for bonding. The potential value of the polyacrylic acid technique was evaluated for bond strength, enamel loss, cleanup, and fracture location—with and without the use of a sealant. Ninety-six premolars were evenly divided into two groups. Group A was preconditioned with polyacrylic acid and group B with phosphoric acid. Half of each group was treated with a sealant before direct bonding of orthodontic brackets. Sealant was not used on the other half of each group and brackets were bonded directly to the conditioned labial surfaces with a composite cement. Bonding and rebonding shear strength tests were carried out for both groups. Results indicated that shear bond strength values for the polyacrylic acid group were approximately one third those of the phosphoric acid group using a composite cement as the adhesive. Enamel loss was measured on the lingual surfaces of 30 of the 96 premolars. The lingual surfaces were conditioned with polyacrylic acid. Following debonding and cleanup procedures, the polyacrylic acid treated surface was left slightly pitted with no resin tags remaining. Cleanup procedures required only a rubber-cup silicate prophylaxis. The total enamel loss was minimal (4.5 μm), thus preserving most of the outermost fluoride-rich layer of enamel.

Flexure strength of repaired dental composites

A study was conducted to determine differences in flexure strength between unrepaired and repaired dental composite bars. Four groups, each consisting of 10 samples, were investigated. Group A consisted of unrepaired samples, while groups B-D consisted of samples which had been cut to lengths of 17.5 mm and repaired to a total length of 35.0 mm. The cut surfaces of these samples were washed with water (group B), treated with phosphoric acid, water and bonding agent (group C), or treated with a silane-toluene solution (group D) before new material was added. The samples were stored in distilled water at 37 degrees C, and after 3 and 6 months the flexure strength of samples from each group was determined by "four-point" bending. The results showed that repaired composites were weaker than unrepaired samples. The mean strength of the silane-toluene treated group was superior in strength to that of the other two groups. This group was also least affected by exposure to water. Of the other two groups, specimens treated with the acid etch technique were superior in strength to the other group.

Crystal growth on the outer enamel surface—An alternative to acid etching

Over the past 2 years an increasing concern has developed about the possible iatrogenic effects of phosphoric acid-etch bonding techniques on the enamel surface. There is an evident heed to develop a mechanical or chemical retention system that would not alter (or would minimally alter) the outer enamel surface. An alternative to the conventional phosphoric acid etch technique has been developed. A preliminary clinical trial showed promising performance under normal clinical conditions. These results were achieved with a minimal loss of surface enamel as evidenced by scanning electron microscopy. Debonding and cleanup were greatly facilitated. Creating a micromechanical retentive surface by the formation of a crystalline interface is a potential alternative to phosphoric acid etching.

A colour atlas of acid etch technique

A colour atlas of acid etch technique

Microleakage at the gingival wall with four Class V anterior restorative materials

R estoring Class V erosion and abrasion lesions is a problem that has plagued dentists for years. A cavity preparation with the incisal or occlusal margin on enamel and with the gingival margin on cementum or dentin presents a special challenge. Composite resins have been advocated to restore the lesions when they are visible. Even when the acid-etch technique is used, leakage at the gingival margin can be expected.’ Such leakage may result in postoperative sensitivity.2 Several studies have shown how microleakage around a composite resin restoration can be reduced or eliminated.7-” All these studies dealt with restorations in which the margins were entirely in enamel rather than with restorations that contained margins in enamel and cementum or dentin. In this study, the marginal leakage of four commercially available anterior restorative materials placed in regions of simulated cervical abrasion/erosion was evaluated. The manufacturers of two of the composite resin materials claim that they will bond to cementum and dentin.

Cusp reinforcement by the acid-etch technique.

Strain gauges were mounted on 12 maxillary pre-molars which were subjected to a sequence of restorative procedures for MOD preparations. An occlusal stress was applied using servohydraulics, and the cuspal flexure was assessed using a strain gauge. Two bonded and three non-bonded restorative procedures were tested for each tooth. The two bonded conditions showed significantly higher cuspal reinforcement when compared with the MOD preparation and the non-bonded restorative procedures. The non-bonded restorations showed some intragroup differences, with one non-bonded composite showing useful cuspal reinforcement. However, this was much less than that afforded by the bonded technique. The deformation of the cusp under occlusal force in restorations bonded by the acid-etch technique showed much less hysteresis when compared with non-bonded restorations.

Composite and intermediate resin tag formation in acid-etched enamel: A scanning electron microscopy evaluation

A divergence of opinion exists regarding the efficacy of the use of an intermediate or unfilled resin in the acid-etch technique of restorative dentistry. For example, the manufacturers of Concise (3M Co., Dental Products Div., St. Paul, Minn.), Adaptic (Johnson and Johnson Dental Products Co., East Windsor, N.J.), and Silar (3M Co., Dental Products Div.) endorse the use of an intermediate resin, while Isopast (Vivadent [USA] Inc., Buffalo, N.Y.) is recommended by the manufacturer for use directly on the etched enamel surface. The main concerns are retention and sealing, which are directly related to the capacity of the resin to wet and thus adapt to the acid-etched enamel. In turn, a good indication of proper wettability is provided by the formation of resin tags in the etched enamel. The purpose of this study was to examine tag formation of selected composite and intermediate resins through the medium of scanning electron microscopy (SEM).

An effective method for relining metal-based prostheses with acid-etch techniques

An effective method for relining metal-based prostheses with acid-etch techniques

Microleakage of direct gold restorations: An in vitro study

lhe adaptation of restorative materials to the walls of cavity preparations has been considered clinically important for many years.’ A chemical bond between a restorative material and tooth structure with no marginal leakage would be ideal. However, at the present time no available material possesses this criterion. Early studies of the microleakage of conventional amalgam alloys, using autoradiographs, showed that the initial sealing properties of amalgam were greatly improved by the use of copal resin cavity liner.‘> ’ More recently, it has been reported that corrosion-resistant amalgam restorations placed after coating the cavity walls with cavity varnish showed no leakage at 48 hours and after 3 months.4 These same authors reported similar results in a study using dogs as experimental animals5 The most recent study of leakage of direct gold restorations used a crystal violet dye technique.” In this study amalgam and compacted gold were found to have less leakage than composite resins using an acid-etch technique. Cohesive gold restorations have long been considered the epitome of clinical restorations in a general practice. Textbooks list adaptation to cavity walls and cavosurface margins as one of the attributes of cohesive direct gold restorations. Pure gold foil, electrolytically deposited mat gold, powdered gold encased in gold foil, and alloyed filling gold are in current use for conservative restorations. The purpose of this study was to evaluate the adaptation to cavity walls of four types of direct filling golds by studying the microleakage around restorations placed with and without a copal resin liner.

Acid-Etching of Caries-Like Lesions of Enamel: A Polarized Light Microscopic Study

The histopathologic effects of acid-etching on caries-like lesions of enamel were studied using polarized light techniques. The results indicated that surface losses and qualitative changes in the superficial portions of the etched surface zones were similar to those reported previously for sound enamel. The etched, intact surface zones appeared to be more porous, while still maintaining their integrities. The ability of the acid-etch technique to affect the lesion to its entire depth was evidenced by the increased incidence of dark zones following the etching procedure. The acid-etch procedure may facilitate remineralization of the etched lesion by providing pathways to the subsurface body of the lesion for remineralizing fluids.