Bond Failure Location Research Articles

Evaluation of a new light-cured orthodontic bonding adhesive

The purpose of this study was to compare a new light-cured bonding system that used a hybrid adhesive containing a resin reinforced glass ionomer (Fuji Ortho LC, GC America, Inc.) with a more traditional light-cured bonding system (Transbond, 3M Unitek) that contained resin material only. Seventy-five recently extracted human molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were randomly separated into five groups of 15 molars each: Group I—using Transbond adhesive system with the enamel etched and dried before bonding. Group II—using Fuji Ortho LC (FOLC) adhesive system with no etch and the enamel wet with water before bonding. Group III—using FOLC adhesive system with the enamel etched and wet with water before bonding. Group IV—using FOLC adhesive system with no etch and the enamel wet with saliva before bonding. Group V—using FOLC adhesive system with the enamel etched and wet with saliva before bonding. The shear bond strength was performed after thermal cycling between 5° ± 2° C and 50° ± 2° C for a total of 2000 cycles with the Zwick test machine (Zwick Gm bH & Co.). After debonding, the teeth and brackets were examined under ×10 magnification to evaluate the site of bond failure and the presence of residual adhesive. The analysis of variance was used to determine whether significant differences existed between the various groups. The findings indicated that there were no statistically significant differences among the three experimental groups I, III, and V that had the enamel surface etched before bonding, regardless of the adhesive used or the enamel surface contamination with water or saliva. On the other hand, the two experimental groups that did not have the enamel etched before bonding (II and IV) had significantly lower bond strengths. In conclusion, etching the enamel surface is a critical variable that affects shear bond strength as well as bond failure location when using the new adhesive system. (Am J Orthod Dentofacial Orthop 1998;114:80-7)

Comparison of shear bond strength and surface structure between conventional acid etching and air-abrasion of human enamel

Recently, air-abrasion technology has been examined for potential applications within dentistry, including the field of orthodontics. The purpose of this study was to compare the traditional acid-etch technique with an air-abrasion surface preparation technique, with two different sizes of abrading particles. The following parameters were evaluated: (a) shear bond strength, (b) bond failure location, and (c) enamel surface preparation, as viewed through a scanning electron microscope. Sixty extracted human third molars were pumiced and divided into three groups of 20. The first group was etched with a 37% phosphoric acid gel for 30 seconds, rinsed for 30 seconds, and dried for 20 seconds. The second and third groups were air-abraded with (a) a 50 μm particle and (b) a 90 μm particle of aluminum oxide, with the Micro-etcher microabrasion machine (Danville Engineering Inc.). All three groups had molar stainless steel orthodontic brackets bonded to the buccal surface of each tooth with Transbond XT bonding system (3M Unitek). A Zwick Universal Testing Machine (Calitek Corp.) was used to determine shear bond strengths. The analysis of variance was used to compare the three groups. The Adhesive Remnant Index (ARI) was used to evaluate the residual adhesive on the enamel after bracket removal. The chi square test was used to evaluate differences in the ARI scores among the groups. The significance for all tests was predetermined at p ≤ 0.05. The results indicated that there was a significant difference in shear bond strength among the three groups (p = 0.0001). The Duncan Multiple Range test showed a significant decrease in shear bond strength in the air-abraded groups. The chi square test revealed significant differences among the ARI scores of the acid-etched group and the air-abraded groups (χ2 = 0.0001), indicating no adhesive remained on the enamel surface after debonding when air-abrasion was used. In conclusion, the current findings indicate that enamel surface preparation using air-abrasion results in a significant lower bond strength and should not be advocated for routine clinical use as an enamel conditioner at this time. (Am J Orthod Dentofac Orthop 1997;112:502-6.)

Evaluation of debonding characteristics of a new collapsible ceramic bracket

A new collapsible ceramic bracket designed with a metal-lined arch wire slot has been recently introduced. The bracket also incorporates a vertical slot designed to help create a consistent bracket failure mode during debonding. The new bracket is thought to combine the esthetic advantages of ceramics and the functional advantages of debonding metal brackets. The purpose of this study was to compare (1) the shear bond strength of the new collapsible bracket with a traditional ceramic bracket, (2) the compressive force required to debond the new bracket from the enamel surface with that needed to debond a traditional metal bracket, and (3) the bond failure location when debonding the new bracket and a traditional ceramic bracket when pliers are used. Sixty-one Clarity collapsible ceramic brackets, 41 Transcend 6000 brackets, and 21 Victory Series metal brackets were bonded to the teeth with the same bonding system. The Zwick Universal Test Machine was used to determine the shear bond strength of 21 teeth bonded with the new bracket and 20 teeth bonded with the Transcend brackets. The same testing device was used to determine the compression force levels needed to debond 20 collapsible brackets and 21 metal brackets. Pliers were used to debond both the new ceramic brackets and Transcend brackets to determine the mode of bond failure. After debonding, all teeth and brackets were examined under 10× magnification. Any adhesive remaining after bracket removal was assessed according to the Adhesive Remnant Index (ARI). The findings indicated that the shear bond strength of the new Clarity ceramic bracket was comparable to that of a conventional ceramic bracket. Similarly, there were no significant differences in the results of the compression tests comparing the magnitude of forces needed to deform and debond both the new ceramic and metal brackets. The ARI scores for both the shear and compression tests indicated a similar bond failure pattern when the new collapsible brackets were compared with either the conventional ceramic or metal brackets. On the other hand, the χ2 test results indicated that, when debonding pliers were used, there was a significantly greater incidence of an ARI score of 1 with the collapsible brackets. This indicated that, when debonding the new brackets with the Weingart pliers, there was a greater tendency for most of the adhesive to remain on the enamel surface. In conclusion, the main advantage of the Clarity ceramic brackets is that they can be debonded in the same manner as metal brackets. When the new ceramic brackets are debonded with the Weingart pliers, most of the residual adhesive remained on the enamel surface, a pattern that is similar to the one observed with metal brackets. The failure at the bracket-adhesive interface decreases the probability of enamel damage but necessitates the removal of more residual adhesive after debonding. (Am J Orthod Dentofac Orthop 1997;112:552-9.)

Direct bonding to Adlloy-treated amalgam

The purpose of this study was to test the bond-enhancing effect by modifying amalgam surfaces with Adlloy (a gallium-tin liquid alloy) and bonding brackets by using two different resin systems. Bond strength and location of bond failure was assessed by using (1) Concise (3M Dental Products) and (2) C&B Metabond (Parkell) systems with and without the use of Adlloy alloy. Class V buccal amalgam restorations (n = 132) were subjected to one of two surface treatments: (1) sandblasting or (2) sandblasting plus Adlloy treatment. Mandibular premolar brackets were bonded with Concise composite resin or C&B Metabond (adhesive) to amalgam surfaces. All specimens were stored in 37° C water for 10 weeks and subjected to thermocycling before bond strength testing. The laboratory shear bond strength of Concise material to amalgam was not improved after Adlloy modification. However, Adlloy-treated amalgam significantly increased the laboratory shear bond strength of orthodontic brackets bonded with C&B Metabond material. The majority (58%) of the bond failures of C&B Metabond bonded to non-Adlloy treated-amalgam occurred at the amalgam-adhesive interface, whereas the majority (58%) of the bond failure of C&B Metabond bonded to Adlloy-treated amalgam failed within the adhesive. Fracture within the amalgam during debonding was observed with C&B Metabond bonded to sandblasted amalgam (21%) and Adlloy-treated amalgam (15%). Regardless of Adlloy treatment, C&B Metabond would appear to provide adequate orthodontic bonding to amalgam; however, there may exist a potential risk of amalgam restoration fracture upon debonding. (Am J Orthod Dentofac Orthop 1997;112:252-8.)

Evaluation of Scotchbond multipurpose and maleic acid as alternative methods of bonding orthodontic brackets

Damage to the enamel surface during bonding and debonding of orthodontic brackets is a clinical concern. Alternative bonding methods that minimize enamel surface damage while maintaining a clinically useful bond strength is an aim of current research. The purpose of this study was to compare the effects on bond strength and bracket failure location of two adhesives (System 1+ and Scotchbond Multipurpose, 3M Dental Products Division) and two enamel conditioners (37% phosphoric acid and 10% maleic acid). Forty-eight freshly extracted human premolars were pumiced and divided into four groups of 12 teeth, and metal orthodontic brackets were attached to the enamel surface by one of four protocols: (1) System 1+ and phosphoric acid, (2) Scotchbond and phosphoric acid, (3) System 1+ and maleic acid, and (4) Scotchbond and maleic acid. After bracket attachment, the teeth were mounted in phenolic rings and stored in deionized water at 37° C for 72 hours. A Zwick universal testing machine (Zwick GmbH & Co.) was used to determine shear bond strengths. The residual adhesive on the enamel surface was evaluated with the Adhesive Remnant Index. The analysis of variance was used to compare the four groups. Significance was predetermined at p ≤ 0.05. The results indicated that there were no significant differences in bond strength among the four groups ( p = 0.386). The results of the Chi square test, evaluating the residual adhesives on the enamel surfaces, revealed significant differences among the four groups (χ 2 = 0.005). A Duncan multiple range test revealed the difference occurred between the phosphoric acid and maleic acid groups, with maleic acid having bond failures at the enamel-adhesive interface. In conclusion, the use of Scotchbond Multipurpose and/or maleic acid does not significantly effect bond strength, however, the use of maleic acid resulted in an unfavorable bond failure location. (Am J Orthod Dentofac Orthop 1997;111:498-501.)

Bond strength following the application of chlorhexidine on etched enamel.

The purpose of this study was to determine whether the application of chlorhexidine to etched enamel affects the shear bond strength and bracket/adhesive failure modes of orthodontic brackets. Forty recently extracted third molars were cleaned divided into two groups of twenty. The first group was etched with a 37% phosphoric acid gel, and a sealant was applied containing a chlorhexidine varnish. Stainless steel orthodontic brackets were bonded using the Transbond XT bonding system (3M/Unitek). Teeth in the second group were etched and bonded using the same bonding system but without chlorhexidine. A Zwick Universal Testing Machine was used to determine shear bond strengths. There were no significant differences in bond strengths between the chlorhexidine treated teeth (= 11.8 +/- 2.1 MPa) and the controls (= 12.4 +/- 3.1 MPa) (p = 0.129). The Chi Square test evaluating the residual adhesive on the enamel surfaces showed no significant differences (P = 0.136) between the two groups evaluated. The use of a primer containing chlorhexidine does not significantly affect shear bond strength nor the fracture site (bond failure location).

Effects of fluoride application on shear bond strength of orthodontic brackets.

The purpose of this study was to determine the shear bond strength and debonding failure modes of orthodontic brackets bonded to teeth that have been treated with various fluoride concentrations. Thirty-six recently extracted human premolars were divided into three groups: prophylaxis with pumice only, prophylaxis using a 13,500 ppm fluoridated pumice, and prophylaxis with pumice followed by application of a 2500 ppm fluoridated paste. The teeth were etched with a 37% phosphoric acid gel, then bonded with a metal orthodontic bracket. The teeth were mounted in phenolic rings and stored in de-ionized water at 37 degrees C for 72 hours. A Zwick Universal Testing Machine was used to determine shear bond strengths. The residual adhesive on the enamel surface was estimated using the Adhesive Remnant Index. Analysis of variance was used to compare the various groups, and significance was predetermined at p < or = 0.5. The results indicate that there were no significant differences in bond strengths between the treated and untreated teeth (p = .233). The Chi Square test evaluating the residual adhesive on the enamel surfaces also showed no significant differences (p =.456). In conclusion, the use of fluoridated prophylactic pastes with varying fluoride concentrations does not significantly affect shear bond strength or bond failure location.

Retention capacity of the bracket bases of new esthetic orthodontic brackets

Tensile bond strength and bond failure locations were evaluated in vitro for three types of direct bonding cements (self-cured diacrylate, dual-cured diacrylate, and dual-cured glass ionomer) with four types of brackets (stainless steel, polycarbonate, ceramic, and ceramic-polycarbonate) by using a plastic cylinder as the substrate. A highly filled, self-cured diacrylate cement gave the highest bond strength values with the polycarbonate, stainless steel, and ceramic-polycarbonate brackets. A dual-cured diacrylate cement gave the highest bond strength with a mechanically retained ceramic bracket. The dual-cured glass ionomer cement gave the highest bond strength values with a silanated ceramic bracket. All bond failures occurred at the bracket/cement interface with the stainless steel bracket, whereas failure locations were at the bracket/cement interface and within the cement with the polycarbonate bracket. Bond failures occurred between bracket and cement, within the cement, and within the bracket with the ceramic brackets. (A M J O RTHOD D ENTOFAC O RTHOP 1995;107:596-603.)

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.

Indirect versus direct bonding: Bond strength and failure location

Bond strengths and failure locations in direct and indirect bonding of orthodontic brackets with foil-mesh bonding pads were compared in an in vitro study that used extracted human premolars. The direct technique comprised bonding the attachments directly to the premolars with composite resin. The indirect technique comprised bonding the attachments to die-stone models of the teeth with composite resin, making silicone positioners to transfer the attachments from the models to the teeth, and bonding to the teeth with the use of two-part unfilled resin. One part of the unfilled resin was applied to the teeth and the other part to the composite resin that was already bonded to the attachments. Placing the positioners on the teeth brought the two parts together to initiate setting. Inspection after bonding disclosed marginal voids in two thirds of the indirect bonds. Of these, two thirds were then sealed with unfilled resin and one third were left defective. There were no significant differences in strength among direct, void-free indirect, and sealed indirect bonds. Indirect bonds with voids were only half as strong. This seems to indicate that sealing around brackets immediately after positioner removal might be a worthwhile clinical routine. Forty-four percent of the direct bonds fractured predominantly at the bracket-adhesive interface, whereas 72% of the indirect bonds failed mainly at the enamel-resin interface. Grouping the data according to failure location showed no difference in bond strength between those that failed at the enamel and those that failed at the bonding pad. Thus the indirect bonding promised similar bond strength and easier debonding because less resin was left on the teeth.

An in-vitro investigation of bond strengths and failure locations using indirect and direct bonding techniques

An in-vitro investigation of bond strengths and failure locations using indirect and direct bonding techniques

Bond strength of orthodontic direct-bonding cement-plastic bracket systems in vitro

Tensile bond strength and failure location were used to evaluate in vitro the effectiveness of commercial bracket primers for bonding diacrylate cements to plastic brackets. Also, the bond strengths of three two-paste, diacrylate cements were compared with those of three one-step diacrylate cements and an acrylic cement for bonding to three commercial plastic brackets. Bond strength of three diacrylate cements to three plastic brackets ranged from 0.03 to 0.34 kg/mm 2 without bracket primer and from 0.51 to 0.85 kg/mm 2 with bracket primer. Most failures (83%) occurred within the bracket when the primers were used. For the seven cements tested, bond strengths were highly dependent on the bracket. Bracket T had the highest values of bond strength, followed by bracket L and then R. For brackets L and T, values of bond strength for the one-step cements were equal to or slightly greater than values for the two-paste cements and the acrylic cement.

Bond strength of orthodontic direct-bonding cement-bracket systems as studied in vitro

Tensile bond strength and failure location were evaluated in vitro for three types of direct bonding cements (unfilled, low filled, and highly filled) with three types of brackets (polycarbonate, stainless steel, and ceramic) using natural teeth and plastic as substrates. An unfilled acrylic cement gave the highest values of bond strength for both the plastic and ceramic brackets, whereas a highly-filled diacrylate cement gave the highest bond strength for the metal brackets. Bond failures occurred at the bracket-cement interface with the stainless steel brackets with each cement, whereas failure locations occurred at the bracket-cement interface, within the cement, and within the bracket for the plastic and ceramic brackets. There were no significant differences in bond strength nor failure location between tooth and plastic substrates.

Strength Behavior of Adhesive Bonds

Abstract Practically all adhesive systems show an increase in strength with decreasing thickness of the adhesive layer. At least five different explanations for this “thickness-strength” rule have been proposed, based upon the following concepts: (a) Molecular orientation of the adhesive. (b) Differences in physical structure. (c) Theory of flaws. (d) Reduction of plastic flow during test. (e) Distribution of internal stresses. An investigation of these alternatives was made by testing butt joints between metal cylinders using eutectic solder, wax, and polystyrene as adhesives. Evidence indicating the correct explanation of the thickness-strength rule was obtained from a study of the effect on bond strength of bond geometry, from the location of bond failure, and from the relations between bond strength and bulk strength.