John F. Laffoon

Comparison of shear bond strength of two self-etch primer/adhesive systems.

Orthodontic brackets adhesive systems use three different agents, an enamel conditioner, a primer solution, and an adhesive resin. A unique characteristic of some new bonding systems is that they combine the conditioning, priming, and adhesive agents into a single application. The purpose of this study was to assess and compare the effects of using one-step and two-step self-etch primer/adhesive systems on the shear bond strength of orthodontic brackets. The brackets were bonded to extracted human molars according to one of two protocols. Group I (control): a two-step self-etch acidic primer/adhesive system was used, Transbond Plus was applied to the enamel surface as suggested by the manufacturer. The brackets were bonded with Transbond XT and light cured for 20 seconds. Group II: a one-step self-etch, self-adhesive resin cement system, Maxcem, was applied directly to the bracket. The self-etch primer/adhesive is made of two components that mix automatically during application. The brackets were then light cured for 20 seconds. The mean shear bond strength of the two-step acid-etch primer/adhesive was 5.9 +/- 2.7 Mpa and the mean for the one-step system was 3.1 +/- 1.7 MPa. The in vitro findings of this study indicated that the shear bond strengths (t = 3.79) of the two adhesive systems were significantly different (P = .001). One-step adhesive systems could potentially be advantageous for orthodontic purposes if their bond strength can be improved.

Effect of time on the shear bond strength of glass ionomer and composite orthodontic adhesives

The purpose of this study was to compare the effects of time on the shear bond strength of a resin-reinforced glass ionomer and a composite adhesive system specifically (1) within half an hour after bonding the bracket to the tooth and (2) at least 24 hours from the time of bonding when the adhesive has achieved most of its bond strength. Ninety-one freshly extracted human molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were cleaned and polished. The teeth were randomly separated into four groups: Group I, glass ionomer adhesive debonded within 30 minutes from initial bonding; Group II, glass ionomer adhesive debonded after 24 hours immersion in deionized water at 37 degrees C; Group III, composite adhesive debonded within 30 minutes from initial bonding; Group IV, composite adhesive debonded after 24 hours immersion in deionized water at 37 degrees C. The results of the analysis of variance comparing the 4 experimental groups (F = 59. 3) indicated the presence of significant differences between the 4 groups (P =.0001). In general, the shear bond strengths were significantly greater in the 2 groups debonded after 24 hours. This was true for both the resin-modified glass ionomer (x = 8.8 +/- 3.6 MPa) and the composite (x = 10.4 +/- 2.8 MPa) adhesives. On the other hand, the shear bond strengths were significantly lower in the 2 groups debonded within 30 minutes of their initial bonding. The bond strength of the resin-modified glass ionomer adhesive (x = 0.4 +/- 1.0 MPa) was significantly lower than that for the composite (x = 5.2 +/- 2.9 MPa) adhesive. The present findings indicated that the resin reinforced glass ionomer adhesive has a significantly lower initial bond strength but increased more than 20-fold within 24 hours. In comparison, the composite adhesive has a significantly larger initial bond strength that doubled within 24 hours. The clinician needs to take these properties into consideration when ligating the initial arch wires.

Effect of a Fluoride-Releasing Self-Etch Acidic Primer on the Shear Bond Strength of Orthodontic Brackets

Conventional adhesive systems use three different agents--an enamel conditioner, a primer solution, and an adhesive resin--during the bonding of orthodontic brackets to enamel. A unique characteristic of some new bonding systems in operative dentistry is that they combine the conditioning and priming agents into a single application. Combining conditioning and priming saves time and should be more cost-effective to the clinician and indirectly to the patient. The purpose of this study was to assess and compare the effects of self-etching primers, including a fluoride-releasing primer, on the shear bond strength of orthodontic brackets. The brackets were bonded to extracted human teeth according to one of four protocols. In group 1 (control), teeth were etched with 37% phosphoric acid; after the sealant was applied, the brackets were bonded with Transbond XT (3M Unitek, Monrovia, Calif) and light cured for 20 seconds. In group 2, a self-etch acidic primer (3M ESPE, St Paul, Minn) was applied as suggested by the manufacturer, and the brackets were then bonded with Transbond XT as in the first group. In group 3, an experimental self-etch primer EXL #547 (3M ESPE) was applied to the teeth as suggested by the manufacturer, and the brackets were then bonded as in groups 1 and 2. In group 4, a fluoride-releasing self-etch primer, One-Up Bond F (J. Mortia, USA Inc. Irvine, Calif) that also has a novel dye-sensitized photo polymerization initiator system was applied as suggested by the manufacturer, and the brackets were then bonded as in the other groups. The present in vitro findings indicated that the shear bond strengths of the four groups were significantly different (P = .001). Duncan multiple range tests indicated that One-Up Bond F (mean +/- SD strength, 5.1+/-2.5 MPa) and Prompt L-Pop (strength, 7.1+/-4.4 MPa) had significantly lower shear bond strengths than both the EXL #547 self-etch primer (strength, 9.7+/-3.7 MPa) or the phosphoric acid etch and the conventional adhesive system (strength, 10.4+/-2.8 MPa).

Shear bond strength comparison of two adhesive systems following thermocycling. A new self-etch primer and a resin-modified glass ionomer.

OBJECTIVE To compare the effects of a standardized thermocycling protocol on the shear bond strength (SBS) of two adhesive systems: a resin-modified glass ionomer and a composite resin used with a new self-etching primer. MATERIALS AND METHODS Forty human molars were cleaned, mounted, and randomly divided into two groups. In group 1, brackets were bonded to the teeth using Fuji Ortho LC adhesive, and in group 2, the Transbond Plus system was used. The teeth were stored in water at 37 degrees C for 24 hours, thermocycled between 5 and 55 degrees C, and debonded using a universal testing machine. The enamel surface was examined under 10x magnification to determine the amount of residual adhesive remaining on the tooth. Students t-test was used to compare the SBS and the chi-square test was used to compare the adhesive remnant index (ARI) scores. RESULTS The mean SBS for the brackets bonded using the Fuji Ortho LC was 6.4 +/- 4.5 MPa, and the mean SBS for the Transbond Plus system was 6.1 +/- 3.2 MPa. The result of the t-test comparisons (t = 0.207) indicated that there was no significant difference (P = .837) between the two groups. The comparisons of the ARI scores (chi(2) = 0.195) indicated that bracket failure mode was not significantly different (P = .907) between the two adhesives. CONCLUSION Although SBS and ARI scores were not significantly different for the two adhesives, clinicians need to take into consideration the other properties of the adhesives before using them.

The effect of repeated bonding on the shear bond strength of a composite resin orthodontic adhesive.

One of the problems clinicians face during treatment is bracket failure. This is usually the result either of the patients accidentally applying inappropriate forces to the bracket or of a poor bonding technique. As a result, a significant number of teeth have to be rebonded in a busy orthodontic practice. The purpose of this study was to evaluate the effect of repeated bonding on the shear bond strength of orthodontic brackets. Fifteen freshly extracted human molars were collected and stored in a solution of 0.1% (wt/vol) thymol. The teeth were cleaned, polished, and etched with a 37% phosphoric acid gel. The brackets were bonded with the adhesive and light cured for 20 seconds. The teeth were sequentially bonded and debonded 3 times with the same composite orthodontic adhesive. At each time, all 15 teeth were debonded within a half hour after bonding to simulate the clinical condition at which a newly bonded bracket is attached to the arch wire. The results of the analysis of variance comparing the shear bond strength at the 3 debonding attempts indicated the presence of no significant differences among the 3 groups (P = .104). However, when the overall change in shear bond strength within each tooth was evaluated between debonding sequences 1 and 3, 10 teeth had a significant (P = .001) decrease (mean +/- SD, -4.6+/-2.5 MPa) in bond strength, whereas 5 teeth had a significant (P = .02) increase (mean +/- SD, 2.8+/-1.6 MPa). The present findings indicated that in general, the highest values for shear bond strength were obtained after the initial bonding. Rebonded teeth have significantly lower and inconsistent shear bond strength; ie, bond strength may further decrease or increase after the second debonding, and the changes in bond strength may be related to the changes in the morphologic characteristics of the etched enamel surface as a result of the presence of adhesive remnants.

Effect of antimicrobial monomer-containing adhesive on shear bond strength of orthodontic brackets.

A new antibacterial and fluoride-releasing bonding system consists of a self-etching primer that contains an antibacterial monomer and a bonding agent that contains sodium fluoride. This study was to determine the effect of using this new adhesive on the shear bond strength of orthodontic brackets. Forty molar teeth were randomly divided into two groups. Group 1 consisted of 20 teeth that were etched for 15 seconds with 35% phosphoric acid, washed with a water spray for 10 seconds, and dried to a chalky white appearance, and the sealant was applied to the etched surface. The precoated brackets were placed on the teeth and light cured. Group 2 consisted of 20 teeth that were etched with 35% phosphoric acid for 15 seconds as suggested by the manufacturer when bonding to intact enamel. The teeth were washed with a water spray for 10 seconds and dried to a chalky white appearance, and the primer containing antibacterial monomer was applied to the etched surface, left for 20 seconds, and sprayed with a mild airstream. The adhesive was applied to each tooth, and the precoated bracket was placed and light cured. There were no significant differences (P = .220) in the shear bond strengths of the two groups. The mean shear bond strength for the antibacterial fluoride-releasing adhesive was 11.7 +/- 5.6 MPa and for the control was 9.6 +/- 5.0 MPa. The use of an antibacterial fluoride-releasing adhesive system did not affect the shear bond strength of the orthodontic brackets within the first half hour after initial bonding.

Comparison of bonding time and shear bond strength between a conventional and a new integrated bonding system.

Conventional adhesive systems use 3 different agents, an enamel conditioner, a primer solution, and an adhesive resin during the bonding of orthodontic brackets to enamel. A characteristic of some new bonding systems is that they combine the conditioning and priming agents into a single application as well as precoat the bracket with the adhesive in an attempt to save time during the bonding procedure. This study compared the total bonding time and shear bond strength (SBS) of 2 bracket-bonding systems: (1) an integrated system that incorporates a self-etching primer and precoated brackets and (2) a conventional system in which the etchant and primer are applied separately and the adhesive applied to the bracket by the clinician. The results of the SBS and the total bonding time comparisons (t = 3.451) of the 2 adhesive systems showed a significant difference (P = .0001). The mean SBS was 9.4+/-3.7 MPa for the new bonding system and 6.2+/-4.4 MPa for the conventional system. The mean total bonding time was 36.5 s/tooth for the new system and 46.7 s/tooth for the conventional system. The clinician has to decide whether the increase in bond strength, the decrease in the total bonding time, and the steps saved during the bonding procedure with the new bonding system balance the increased cost incurred.

The effect of porcelain surface conditioning on bonding orthodontic brackets.

The purpose of this study was to evaluate the effects of a new self-etching primer/ adhesive used to enhance the shear strength of orthodontic brackets bonded to porcelain surfaces. Forty-five porcelain maxillary central incisor teeth were used in the study. The teeth were divided randomly into three groups: group I (control), the porcelain teeth were etched with 37% phosphoric acid followed by a sealant and the brackets were bonded with a composite adhesive; group II, the porcelain teeth were microetched and hydrofluoric acid and silane applied and metal brackets were then bonded with the composite adhesive; and group III, the porcelain teeth were etched with phosphoric acid and a self-etching primer/adhesive applied before bonding. Brackets precoated with the adhesive were used on all three groups of teeth. All teeth were stored for 24 hours at 37 degrees C before debonding. The results of the analysis of variance (F = 10.7) indicated that there was a significant difference (P = .001) between the three groups. The mean shear bond strengths of conventional bonding using a 37% phosphoric acid and sealant was 4.4 +/- 2.7 MPa, whereas that of microetching followed by the application of hydrofluoric acid and silane was 11.2 +/- 4.7 MPa, and for the new self-etching primer/adhesive it was 10.3 +/- 5.3 MPa. The last two groups had the highest bond strength values and were not significantly different from each other.

Effects of Modifying the Adhesive Composition on the Bond Strength of Orthodontic Brackets

In an attempt to save chair time during bonding, metal brackets have been precoated with the adhesive material. Although the adhesive used on the precoated brackets is basically similar in composition to that used for bonding uncoated brackets, there are differences in the percentages of the various ingredients incorporated in the material. These changes are intended to enhance specific clinical properties. The purpose of this study was to determine whether modifications in the composition of the adhesives, used on precoated and uncoated metal brackets, affect their shear bond strengths during the first half hour after bonding. This is the time span when the initial arch wires are ligated. Sixty freshly extracted human molars were bonded with three different compositions of the same basic adhesive. The teeth were mounted in phenolic rings. An occlusogingival load was applied to the brackets producing a shear force at the bracket-tooth interface utilizing a Zwick Universal Test Machine. Analysis of variance was used to compare the three adhesives. Significance was predetermined at < or =.05 level of confidence. The present findings indicated that the shear bond strengths of the various modifications of the adhesive used on two different precoated metal brackets were not significantly different (F-ratio = .729 and P = .407) from those obtained with the conventional adhesive used on uncoated brackets. The mean values for the shear bond strengths of the two precoated brackets were: APC = 5.1+/-1.7 MPa and APC II = 4.9+/-2.1 MPa. The shear bond strength for the conventional adhesive used on the uncoated brackets was = 5.7+/-2.4 MPa. All bracket/adhesive combinations tested provided clinically acceptable shear bond forces within the first 30 minutes after initial bonding.

Enamel Cracks and Ceramic Bracket Failure during Debonding In Vitro

OBJECTIVE To test the null hypothesis that no difference in bracket failure characteristics is noted when use of a new ceramic bracket debonding instrument is compared with the use of conventional pliers. MATERIALS AND METHODS Thirty maxillary premolars were randomly assigned to one of two groups. In group 1, Clarity collapsible ceramic brackets (3M Unitek, Monrovia, Calif) were debonded with the use of conventional Utility/Weingart (3M Unitek, Monrovia, Calif) pliers. In group 2, Clarity brackets were debonded with a new Debonding Instrument (3M Unitek). For all teeth, the same bracket bonding system was used. Following debonding, teeth and brackets were examined under 10x magnification for assessment of bracket failure (fracture) and of residual adhesive on the enamel surface. Enamel surfaces were visualized with transillumination prior to bonding and after removal of the residual adhesive, so the effect of the debonding forces could be determined. RESULTS The results of Adhesive Remnant Index comparisons indicated that a statistically significant difference (chi2 = 8.73; P = .013) in bond failure patterns was apparent when the two groups were compared. Brackets debonded with the new instrument showed a greater tendency for the adhesive to be removed from the tooth during debonding. CONCLUSIONS The hypothesis is rejected. Although the incidence of enamel damage following debonding was similar in the two groups, the use of the new Debonding Instrument decreased the incidence of bracket fracture.