An ex vivo study of self-, light-, and dual-cured composites for orthodontic bonding

Influence of surface treatments on bond strength of metal and ceramic brackets to a novel CAD/CAM hybrid ceramic material

This study evaluated the effect of four different surface treatments methods on the shear bond strength (SBS) of ceramic and metal brackets to Vita Enamic (VE) CAD/CAM hybrid ceramic. A total of 240 plates (10 mm × 10 mm × 3 mm) were cut from VE ceramic blocks and divided into two groups. In each group, four subgroups were prepared by hydrofluoric acid (HF); phosphoric acid (H3PO4); diamond ceramic grinding bur; and silica coating using CoJet system (CJ). Maxillary central incisor metal (Victory Series) and ceramic (Clarity) brackets were bonded with light-cure composite and then stored in artificial saliva for 1 week and thermocycled. The SBS test was performed, and the failure types were classified with adhesive remnant index scores. Surface morphology of the ceramic was characterized after treatment using a scanning electron microscope. Data were analyzed using two-way ANOVA, Tukey HSD test, and Weibull analysis. SBS was significantly affected by the type of bracket and by type of treatment (P < 0.001). Specimens treated with CJ presented with significantly higher SBS compared to other groups (P < 0.05). Improvements in SBS values (MPa) were found in the following order: CJ > HF > Bur > H3PO4. Ceramic bracket showed higher SBS compared to metal bracket. Adhesive failures between the ceramic and composite resin were the predominant mode of failure in all groups. Surface treatment of VE CAD/CAM hybrid ceramic with silica coating enhanced the adhesion with ceramic and metal brackets.

Comparison of Shear Bond Strength and Estimation of Adhesive Remnant Index between Light-cure Composite and Dual-cure Composite: An in vitro Study

Aims and objectives: To measure and compare the shear bond strength and adhesive remnant index of light-cure composite. (Enlight, Ormco.) and dual-cure composite (Phase II dual cure, Reliance Ortho).

Materials and methods: Sixty extracted human premolar teeth were divided into two groups: group I (blue): conventional light cure composite resin. (Enlight, Ormco.) and group II (green): dual cure composite resin. (Phase II dual cure, Reliance Ortho.) with 30 teeth in each group. These samples were tested on the universal testing machine to measure the shear bond strength.

Results: Student t-test showed that the mean shear bond strength of the conventional light cure group (8.54 MPa - 10.42 MPa) was significantly lower than dual cure group (10.45 MPa -12.17 MPa).

Conclusion: These findings indicate that the shear bond strength of dual-cure composite resin (Phase II dual cure, Reliance Ortho) is comparatively higher than conventional light-cure composite resin (Enlight, Ormco). In the majority of the samples, adhesive remnant index (ARI) scores were 4 and 5 in both the groups whereas score 1 is attained by the least number of samples in both the groups.

How to cite this article: Verma G, Trehan M, Sharma S. Comparison of Shear Bond Strength and Estimation of Adhesive Remnant Index between Light-cure Composite and Dual-cure Composite: An in vitro Study. Int J Clin Pediatr Dent 2013;6(3):166-170.

Effect of Activation Mode on Shear Bond Strength of Metallic Brackets

The aim of this study was to evaluate the shear bond strength (SBS) of metallic orthodontic brackets bonded to bovine teeth using light-activated or chemically activated composite resins. One hundred and twenty bovine mandibular incisors were divided into 6 groups (n=20), according to the bonding materials: Transbond XT (T); Enforce Dual (ED); Enforce chemical (EC); Enforce Light-activated (EL); Concise Orthodontic (C); and RelyX Unicem Capsule (UN). Metallic brackets were positioned and firmly bonded to the teeth. Light-activation for T, ED, EL and UN was carried out with four exposures on each side of the bracket with 20 s total exposure times using XL2500 (3M ESPE). EC and C were chemically cured. Next, all specimens were stored in deionized water at 37 °C for 24 h. The shear bond strength was carried out at a crosshead speed of 1.0 mm/min. Data were subjected to one-way ANOVA and Tukey's test (α=0.05). The adhesive remnant index (ARI) was evaluated at 8× magnification. C (17.72±4.45) presented significantly higher SBS means (in MPa) than the other groups (p<0.05), followed by EC (11.97±5.77) and ED (10.57±1.32). EL (5.39±1.06) and UN (4.32±1.98) showed the lowest SBS means, while T (9.09±2.56) showed intermediate values. For ARI, there was a predominance of score 0 for EC, C and UN, and score 3 for T, ED and EL. In conclusion, the activation mode influenced the SBS.

Effect of debonding force direction on orthodontic shear bond strength

INTRODUCTION

The aim of this study was to determine the influence of debonding force direction in shear bond strength testing of orthodontic brackets in vitro.

METHODS

One hundred fifty extracted bovine permanent mandibular incisors were randomly divided into 5 groups of 30 specimens each. Before bonding with a composite adhesive, enamel surfaces were etched with 37% phosphoric acid for 30 seconds. Teeth were bonded with mesh-based stainless steel orthodontic brackets. Shear bond strength was measured with a universal testing machine. Debonding forces were directed either parallel to the bracket base (group B), toward the enamel surface (group A: 15 degrees), or away from the enamel surface (group C: 15 degrees; group D: 30 degrees; group E: 45 degrees).

RESULTS

Shear bond strength measurements were as follows: 22.90 (SD, 1.72) MPa (group A), 17.90 (SD, 2.63) MPa (group B), 12.99 (SD, 1.71) MPa (group C), 7.93 (SD, 1.14) MPa (group D), and 6.65 (SD, 1.14) MPa (group E). Analysis of variance indicated that shear bond strengths were significantly different between the groups investigated. Mean adhesive remnant index scores ranged between 1.60 in group B and 2.13 in group D.

CONCLUSIONS

Shear bond strength measurements were significantly influenced by the direction of the debonding force, indicating the need for control and standardization of this testing parameter in orthodontic shear bond strength testing.

Influence of cross-head speed in orthodontic bond strength testing

OBJECTIVE

The aim of this study was to investigate the influence of cross-head speed on debonding force of orthodontic brackets.

METHODS

One hundred and twenty extracted permanent bovine mandibular incisors were randomly divided into 4 groups of 30 specimens each. Teeth were bonded with stainless steel orthodontic brackets. Enamel surfaces were etched with 37% phosphoric acid for 30 seconds and bonded with a composite adhesive. Debonding force measurements were performed with a universal testing machine Zwicki Z 2.5 (Zwick, Germany). Cross-head speeds of the four groups were: 0.1 mm s-1 (group A), 0.5 mm s-1 (group B), 1.0 mm s-1 (group C), 5.0 mm s-1 (group D).

RESULTS

Mean debonding force measurements were as follows: 215.35 (39.09) N (group A), 231.79 (48.62) N (group B), 236.64 (39.26) N (group C), 224.95 (34.67) N (group D). Analysis of variance indicated that there were no significant differences in debonding forces between the groups investigated. The adhesive remnant index showed a median value of 2.0 for all groups.

SIGNIFICANCE

Cross-head speed variation between 0.1 and 5 mm min-1 does not seem to influence debonding force measurements or failure mode of brackets bonded to enamel with a composite adhesive.

Plasma arc versus halogen light-curing of adhesive-precoated orthodontic brackets: A 12-month clinical study of bond failures

The purpose of this randomized clinical trial was to evaluate the performance of adhesive-precoated brackets cured with 2 different light-curing units (conventional halogen light and plasma arc light). Thirty patients treated with fixed appliances were included in the investigation. Each patient's mouth was divided by the split-mouth design into 4 quadrants. In 15 randomly selected patients, the maxillary left and mandibular right quadrants were cured with the halogen light, and the remaining quadrants were cured with the plasma arc light. In the other 15 patients, the quadrants were inverted. A total of 600 adhesive precoated stainless steel brackets were examined: 300 were cured with a conventional halogen light for 20 seconds, and the others were cured with the plasma arc light for 5 seconds. The number, cause, and date of bracket failures were recorded for each light-curing unit over 12 months. Statistical analysis was performed with the Fisher exact test, Kaplan-Meier survival estimates, and the log-rank test. No statistically significant differences in bond failure rates were found between the adhesive-precoated brackets cured with the halogen light and those cured with the plasma arc light; neither were any significant differences in performance found with each light-curing unit between the maxillary and mandibular arches. Plasma arc lights can be considered an advantageous alternative to conventional light curing, because they enable the clinician to reduce the curing time of adhesive-precoated orthodontic brackets without significantly affecting their bond failure rate.

In vivo evaluation of a moisture-activated orthodontic adhesive: a comparative clinical trial

OBJECTIVES

To evaluate and compare the clinical performance of a water-activated, ethyl-cyanoacrylate adhesive to a conventional composite resin. The null hypothesis tested was that there was no difference in bracket survival distribution, over a period of orthodontic treatment, for brackets bonded with either bonding agent.

DESIGN

Single center randomized controlled clinical study.

SETTING AND SAMPLE POPULATION

Twenty-five consecutive patients (15 females and 10 males) were selected and treated with fixed appliances in a university postgraduate orthodontic clinic. All teeth, but the molars, were bonded with twin stainless steel brackets (n = 429) using a split-mouth technique and random allocation of the two adhesives.

OUTCOME MEASURE

Bond failure rates during a period of 9 months were estimated for each adhesive system and the corresponding bracket survival curves were plotted using the Kaplan-Meier product-limit estimate. Bracket survival distributions with respect to adhesive material, tooth location, investigator, and bond failure interface were then compared by means of a log-rank test. Bond failure interface was determined using the Adhesive Remnant Index (ARI).

RESULTS

The water-activated bonding material recorded a significantly higher bond failure (22.4%) than the composite resin (5.1%). There were also statistically significant differences in bracket survival distributions between the two adhesives (log-rank test: p < 0.001). Premolars exhibited higher bond failure rates than incisors and canines (p < 0001). The predominant mode of failure was within the bonding material.

CONCLUSION

Further investigations focused on the improvement of the physical and mechanical properties of the water-activated bonding system are needed to make it a reliable alternative adhesive for the direct bonding of orthodontic brackets.

The relationship between acid-etch patterns and bond survival in vivo

The aim of this study was to investigate the relationship between acid-etch quality and bond survival in vivo. The subjects were 29 orthodontic patients. High-resolution silicone impressions were taken of the buccal tooth surfaces after etching for 30 seconds with 37% phosphoric acid. The impressions were replicated in epoxy resin and examined under high magnification in a scanning electron microscope. A 4-point classification system and histometric techniques were used to evaluate etch patterns on the enamel surfaces where orthodontic brackets were to be bonded. After impressions were made, all teeth (including first molars) were bonded with 0.022-in Andrews' prescription brackets ("A" Company, San Diego, Calif) and Right-On composite (TP Orthodontics, Leeds, England). The first date of bond failure for each tooth was recorded; it varied from 1 to 806 days. An ideal etch pattern was found on less than 5% of the orthodontic bonding area; type C pattern (pitted enamel surface) occupied the greatest area. Overall, the failure rate was 55.8% over 26 months; the greatest failure rate occurred in first molars. Multiple regression analysis revealed a positive and statistically significant relationship between the area occupied by ideal etch type and the length of survival of the bond (P <.001).

An ex vivo study to investigate bond strengths of different tooth types

This study aimed to identify the presence and pattern of differences in ex vivo shear bond strength between tooth types when bonding orthodontic brackets using Right-On, and took the form of a prospective laboratory study of bond strength on different tooth types, at the Newcastle University Dental School Materials Science Laboratory, 1997-1999. Ex vivo bond strength testing was undertaken using the technique described by Fox et al. (BJO 18, 125-130, 1991) on a total of 120 extracted incisor, canine, and premolar teeth of each dental arch. Analysis was by one-way ANOVA with Tukey's pairwise comparisons, and by Weibull Analysis. Shear stress to failure (measured in MPa) was recorded on Instron 5567 universal testing machine. Significant differences in mean bond strength existed between different tooth-type series. Canine (upper 12.3, lower 12.1) and premolar (upper 11.9, lower 10.9) teeth exhibited higher strengths than incisors (upper 6.9, lower 9.0). The results of this study confirm that ex vivo bond strength is not uniform across all teeth.

A new multipurpose dental adhesive for orthodontic use: an in vitro bond-strength study

The purpose of this study was to evaluate the compatibility of a new dental adhesive, High-Q-Bond (HQB) adhesive, for the bonding of orthodontic brackets by determining its bond strength and the mode of bond failure after debonding. Eighty extracted human premolars were divided into 4 groups, 20 in each group. In groups 1 and 2, stainless steel brackets were bonded to etched enamel with HQB and Right-On adhesives respectively. In groups 3 and 4, the same adhesives were used to bond stainless-steel brackets to roughened, old amalgam restorations prepared in the teeth. After 72 hours of incubation in saline solution at 37 degrees C, debonding was performed with a shearing force. The force at bond failure was recorded, and the mode of bond failure was examined. Results showed that when bonding to enamel, both the HQB and the Right-On material achieved adequate bond strength, and no significant difference was found between the two. However, after debonding, the HQB material left no adhesive on the enamel, whereas the Right-On material left significant amounts of adhesive on the enamel. When bonding to amalgam, the HQB material had a significantly higher shear bond strength than did the Right-On adhesive. It is suggested that HQB can be applied for orthodontic use, but further clinical studies are required to evaluate its efficacy.

Notching of orthodontic bonding resin to facilitate ceramic bracket debond--an ex vivo investigation

This ex vivo study assessed the potential of introducing a notch in the bond layer, as a means of facilitating the removal of ceramic brackets. Sixty extracted premolar teeth were divided into three groups of 20 teeth and bonded with Intrigue brackets using Concise chemically-cured adhesive. The bonding technique was modified with groups 1 and 2 by introducing a notch in the bond layer. Group 1 was notched from the gingival aspect, group 2 from the occlusal, and group 3 served as a control. The brackets were removed by applying a shear load from the gingival aspect using an Instron universal testing machine. The mean force to debond was calculated for each group. The results showed that introducing a notch significantly reduced the mean and maximal debond forces. This was confirmed with Weibull analysis with the notched specimens having a higher probability of failure at any force. In addition, ceramic bracket fracture was eliminated. Notching the bonding resin may be helpful in facilitating the removal of ceramic brackets.

Orthodontic adhesives and bond strength testing

A bracket bond failure is a frustrating occurrence in orthodontic practice. Because the location of the bond failure may indicate the probable cause, it is important to understand the significance of "bond strength" in a clinical application. Bonding in orthodontics can be studied using controlled clinical models or in vitro using simulated clinical models or more fundamental, isolated substrate models, in which bonding of an adhesive to tooth structure or a bracket is studied independently. With numerous adhesives and orthodontic band and bracket materials available as well as other orthodontic substrates besides enamel, such as esthetic ceramic restorations, in vitro models play an important role in characterizing the bonding potential of new systems. This article reviews bonding of orthodontic brackets and bands using various orthodontic adhesives to dental substrates from the perspective of bond strength and its measurement.

Review of dental materials citations: Part B, July to December 1995

OBJECTIVE

A lag of many months occurs between journal issue publication and updates to electronic databases. The objective of this literature analysis was to identify and categorize all of the dental materials citations in biomedical journals that were published from July 1995 through December 1995.

METHODS

Seventeen primary and 51 secondary journals were searched using their tables of contents to detect and record dental materials publications from July to December of 1995. Those journals that were typically rich in dental materials articles were classified as primary ones. Citations were categorized into 17 topics and divided into subsections. The review excluded case reports, most literature related primarily to dental implants, and most articles on biomedical materials used outside of the field of general dentistry.

RESULTS

The greatest number of citations was related to topics of dentin bonding and resin-based restorative filling materials (composites and glass ionomers). There was no major change in the number of dental materials publications per year reported from 1993 (n = 786) to 1995 (n = 751).

SIGNIFICANCE

This citation list provides a comprehensive resource for use by academicians and researchers to bridge the gap between initial publication and access to electronic searching methods for major databases.