Does surface priming increase the bond strength of orthodontic brackets? An experimental study

OBJECTIVE

To evaluate the effects of metal primer II (MP II) on the shear bond strength (SBS) of orthodontic brackets bonded to teeth and bis-acryl composite provisional material (Bis-Acryl).

MATERIAL AND METHODS

Twenty extracted human premolars specimens and 20 premolar shaped Bis-Acryl specimens were obtained and randomly divided into two surface groups. The first group consisted of human premolars (T) bonded to brackets in the conventional way while in the second (T-MP) MP II was applied on the bracket base before bonding. Similarly, one group of provisional material (PM) was prepared according to conventional treatment and another with the application of MP-II metal bonder (PM-MP). In all cases Ortho-brackets (Victory Series, 3 M) were bonded employing Transbond XT resin cement. Then the brackets were debonded under shear and the results were statistically analyzed by two-way analysis of variance and Holm Sidak at α = .05. The debonded surfaces of all specimens were examined by light microscopy and the Adhesive Remnant Index (ARI) was recorded.

RESULTS

The SBS results exhibited significant differences er (p < .001). For both the T and TM the application of MP-II increased the SBS compared to respective control groups (p < .001). The T-C group was found inferior compared to PM-C (p < .001) and the same is true for the comparison between T-MP and PM-MP (p < .001). ARI indexes demonstrated that the tooth groups were characterized by a predominantly adhesive failure at the resin-dentin interface. In contrast, the control group for provisional crowns (PM-C) showed a predominantly cohesive failure mode, which moved to predominantly adhesive after the application of MP II.

CONCLUSION

The application of MP II enhances the SBS on both, human enamel and provisional crown materials.

Evaluation of shear bond strength of orthodontic adhesives with integrated primer: A comparative study

Objectives:

The study aimed to compare the shear bond strength (SBS) of three orthodontic adhesives with integrated primer, with those of self-etching and conventional bonding adhesives.

Material and Methods:

One hundred extracted premolars were randomly allocated to five groups. Brackets were bonded using three adhesives with integrated primer (GC Ortho Connect™, Biofix, and Orthocem). A group of brackets was bonded with the conventional bonding procedure (Transbond XT) and one group was bonded with a self-etching primer (Transbond™ Plus). All samples were subjected to thermal aging (5000 cycles: At 5°C and 55°C media). The compressive strength test was performed and the maximum load when the bracket detached was recorded. The amount of residual adhesive (ARI) remaining on the tooth surface was assessed visually.

Results:

Significantly higher SBS values were recorded with the conventional technique (14.01 ± 5.79 megapascals [MPa]), compared to other groups except for GC Ortho Connect™ (11.86 ± 3.83 MPa). There was no significant difference between the self-etching group and the groups containing integrated primer samples. However, one of the adhesives with integrated primer presented SBS values near-slightly below the limit considered clinically successful (7.65 ± 3.71 MPa). The ARI scores varied between adhesive groups; GC Ortho Connect™ and the self-etching primer samples showed statistically significantly higher scores compared to the three other groups.

Conclusion:

Clinically successful bonding values were achieved with two out of three different adhesives with integrated primer. One of the adhesives with integrated primer provided a similar SBS value to the tri-step conventional bonding procedure. ARI scores varied independently from SBS values.

Effect of self-etch primer application on the bond failure rate of a mandibular bonded lingual retainer

BACKGROUND

The aim of this study was to examine the effect of self-etch primer (SEP) application on the bond failure rate of a mandibular bonded lingual retainer over 24 months.

METHODS

The average age of the 86 individuals included in this study was 17 years 4 months. After the removal of the orthodontic appliances, the lingual retainers, which were made of six-stranded stainless steel wire, were bent and bonded onto the lingual surface of all mandibular anterior teeth. The study was performed using a split-mouth design. In the study group, the SEP was administered to the teeth's lingual surfaces. In the control group, they were etched using 37% phosphoric etchant liquid gel. After etching, the primer was applied. The adhesive resin was applied and the retainer was fitted. The patients were re-evaluated over 24 months. The first bond failures and the amount of adhesive remaining on the tooth were recorded as the adhesive remnant index (ARI) scores. The chi-square test was used to compare the bond failure rates (P = 0.231) and ARI scores between the groups (P = 0.162). The survival rates of the retainers were estimated using the Kaplan-Meier test (P = 0.237). The significance level was P < 0.05.

RESULTS

The bond failure rates, ARI scores, and survival rates did not differ significantly between the groups.

CONCLUSIONS

The results of this study demonstrated that an SEP can be used successfully in mandibular lingual retainer bonding. In situations where saliva isolation is difficult, bonding a fixed lingual retainer with SEP is recommended.

Impact of temperature changes to the adhesion strength of molar tubes: an in vitro study

Background

The main purpose of this was to determine study adhesion strength of molar tubes bonding with a composite adhesive after exposure to a sudden change in temperature (thermal cycles).

Methods

The study sample consisted of 40 recently extracted human first permanent molars, which were randomly divided into two groups of 20: group 1 was the experimental group (affected by thermal cycles), and group 2 was the control group. Molar tubes were bonded with a light-cure tube adhesive. The experimental group teeth were dipped 2,000 times in saline at 5 °C and at 55 °C. The control group were immersed in 37 °C saline. Molar tubes for both groups were removed with an adapted Mecmesim Multitesters 2.5—I, and the data were recorded with EMPEROR software. ANOVA was used to calculate and compare the results.

Results

In the experimental group of the teeth, the maximum force was obtained at 94.2 N and the lowest force was 19.69 N. In the control group of the teeth, the maximum force was obtained at 159.1 N and the lowest force was 28.1 N. In the experimental group, the mean debonding force (59.12 N) was statically significantly smaller than in the control group (79.88 N), p = 0.0345. The forces in the control group were by 1.35 times greater than those in the experimental group.

Conclusions

The forces of the adhesion of molar tubes to the tooth surface were reduced after exposure to a sudden change in temperature (thermal cycles). The results were significantly different between the experimental group and the control group.

Siloranes-Suitability of a Novel Adhesive for Orthodontic Bracket Bonding

Recently, an epoxy-based resin-Filtek Silorane-has been proposed for restorative fillings. It was the aim of the investigation to evaluate the suitability of this novel resin for orthodontic bracket bonding on unground enamel. Shear bond strength was measured for two adhesives-Filtek Silorane, Transbond XT-in combination with steel, ceramic and polymer brackets. For Filtek Silorane etching was performed with the Silorane self-etching primer, as well as phosphoric acid. The Transbond XT samples were etched with phosphoric acid only and served as the control group. All samples were thermo-cycled (1000×, 5-55 °C). Shear testing was carried out with an Instron 3344. In addition, ARI scores were evaluated. The Shear bond strength showed a weak adhesion of Filtek Silorane to unprepared enamel, either with the self-etching primer or the conventional etching (0.87-4.28 MPa). The Shear bond strength of the control group was significantly higher (7.6-16.5 MPa). The ARI scores showed a clear failure at the enamel-adhesive interface for all Filtek Silorane samples. For the combination of Transbond XT and different brackets the failure was found at the adhesive-bracket interface. The novel epoxy-based resin Filtek Silorane is not appropriate for bracket bonding to unprepared enamel.

Rheological and Mechanical Properties of Resin-Based Materials Applied in Dental Restorations

Resin-based materials have been prevalent for dental restorations over the past few decades and have been widely used for a variety of direct and indirect procedures. Typically, resin-based dental materials are required to be flowable or moldable before setting and can provide adequate mechanical strength after setting. The setting method may include, but is not limited to, light-curing, self-curing or heating. In this review, based on different indications of resin-based dental materials (e.g., dental filling composite, dental bonding agent, resin luting cement), their rheological and mechanical properties were reviewed. Viscous and flexible properties were focused on for materials before setting, while elastic properties and mechanical strength were focused on for materials after setting. At the same time, the factors that may affect their rheological and mechanical properties were discussed. It is anticipated that the insightful information and prospections of this study will be useful to the future development and fabrication of resin-based dental restorative materials.

Effects of enamel deproteinization with different application times on the shear bond strength of a self-etching primer: An in vitro study

OBJECTIVE

The aim of this in vitro study was to evaluate the effects of enamel deproteinization on the shear bond strength of a self-etching primer Transbond Plus™(TBP), with different application times of sodium hypochlorite (NaOCl 5.25%), primarily and secondarily on the adhesive remnant index score.

MATERIALS AND METHODS

One hundred twenty-five freshly extracted human premolars were randomly and blindly divided into five groups according to the enamel surface preparation, as follows (n=25): group 1(control): Etching with 37% phosphoric acid for 15seconds+Bonding; group 2 (control): TBP™ without NaOCl, group 3: 60seconds NaOCl+TBP™, group 4: 30seconds NaOCl+TBP™, group 5: 15seconds NaOCl+TBP™. The same composite resin was used (Transbond XT™) to bond the orthodontic metal brackets. After the immersion of the teeth in distilled water at 37°C for 24hours the shear bond strength was measured using the universal testing machine and the adhesive remnant index score (ARI) was evaluated under an optical microscope (25×).

RESULTS

The mean SBS values (inMPa) of the groups were respectively: group 1: 13.03±5.36; group 2: 12.28±3.06; group 3: 12.38±4.55; group 4: 12.98±5.76; and group 5: 11.73±5.67. Enamel deproteinization increased the SBS for groups 3 and 4, but no statistically significant difference was found between the five groups (P=0.883). Group 1 showed the highest ARI scores, with 52% of the teeth retaining all the adhesive (score 3). However, for all the other groups, scores 0 and 1 were predominant, with less than half of the adhesive or no adhesive at all remaining on the teeth.

CONCLUSIONS

Enamel deproteinization with sodium hypochlorite (5.25%) and the variation of its application time has no effect on the SBS of the self-etching primer Transbond Plus ™.

Effects of Bonding Agents on Metal-Ceramic Bond Strength of Co-Cr Alloys Fabricated by Selective Laser Melting

Bonding agents have been developed to improve bond strength between ceramic and Co-Cr metal. The aim of this study was to investigate the influence of two bonding agents on bond strength of Co-Cr metal fabricated by selective laser melting (SLM). Bond strength was determined by a three-point bending test, and the interfaces of the metal and ceramic, before and after the bending test, were observed by optical microscopy and scanning electron microscopy (SEM) to determine the thickness of the oxide layer and amount of ceramic remaining. To analyze the elemental composition of the bonding agents and fractured surfaces, energy dispersive X-ray spectroscopy (EDS) was used. Co-Cr specimens with bonding agent showed significantly higher bond strength than Co-Cr specimens without bonding agents. The fractured surfaces of most specimens showed mixed failure, but failure mode varied according to bonding agent and fabrication type. Specimens from groups treated with bonding agents had significantly higher remaining ceramic fractions on fractured Co-Cr alloys than specimens from groups that did not receive bonding agent. Mass amounts of silicone (Si) and titanium (Ti) on the fractured alloy surfaces were also different among specimens according to method of fabrication and presence of bonding agent. Together, the results suggest that application of bonding agent to 3D printed Co-Cr metal increases bond strength with ceramics.

In Vitro Study of Shear Bond Strength in Direct and Indirect Bonding with Three Types of Adhesive Systems

This study aimed to compare the shear bond strength (SBS) and adhesive remaining index (ARI) using one conventional and two novel adhesive systems with clinical step reduction and direct and indirect bonding. A sample of 72 human premolars were divided into six groups of 12 samples. The first three groups (G1, G2, G3) were bonded with a direct technique, while the remaining groups (G4, G5, G6) were bonded by the indirect technique. Groups G1 and G4 used conventional acid-etching primer composite (XT); groups G2 and G5 used self-etching bonding (BO), and groups G3 and G6 had an acid-etching treatment followed by a self-adhesive composite (OC). All groups were exposed to thermocycling. Shear bond strength was analyzed with a universal test machine, and the ARI was examined with 4× magnification. The results showed statistically significant differences between the three adhesive systems. The highest strength values were observed in the XT group G1 (13.54 ± 4 MPa), while the lowest were shown in the BO G2 samples (5.05 ± 2 MPa). There was no significant difference between the direct or indirect bonding techniques on the three compared groups. The type of primer and bonding material significantly influenced the SBS. Values with self-etching bonding were below the minimum recommended for clinical use (5.9-7.8 MPa). There was no difference between indirect and direct bonding techniques. The lowest ARI scores (0-1) were observed in both self-etching and BO groups. Further clinical studies are needed to compare in vivo results.

Effect of Fluoride Releasing Bonding Materials on Shear Bond Strength of Orthodontic Brackets

Objective

The aim of the present study was to compare the shear bond strength (SBS) of three different fluoride-releasing bonding agents with a conventional adhesive system.

Methods

Eighty-four extracted human premolar teeth were separated into four groups and embedded in acrylic molds consisting of 21 teeth in each group. Brackets were bonded with Transbond XT in group 1, Clearfil SE Protect Bond in group 2, LED Proseal in group 3, and Opalseal in group 4. After bracket bonding, the teeth were thermocycled 1000 times. SBS test was performed, and Adhesive Remnant Index (ARI) scores of the groups were assessed.

Results

One-way analysis of variance test was used to compare the significant differences between the groups. Chi-square and Fisher's exact tests were used to evaluate ARI scores. The Opalseal group showed the highest bond strength, but there was no statistically significant difference between the groups in SBS values (p=0.067). The results of ARI scores were statistically significant.

Conclusions

All bonding materials used in the study showed clinically sufficient bond strengths.

Debonding characteristics of orthodontic brackets subjected to intraoral stresses under different adhesive regimes: An in-vitro study

AIM

To evaluate the effect of simulated intraoral hydraulic, thermal, and mechanical stresses on the debonding characteristics of orthodontic brackets under different adhesive regimes.

MATERIALS AND METHODS

Groups of pre-coated (G1) and non-coated (G2) orthodontic metal brackets were bonded onto the buccal surfaces of 96 premolars using etch-and-rinse (SG1, n = 24) and self-etch (SG2, n = 24) primers. Twelve specimens (C1) from each subgroup were subjected to early debonding resistance tests, while the other twelve (C2) were used to test delayed debonding resistance after exposure to conditions simulating intraoral hydraulic, thermal, and mechanical stresses. The debonding resistance of the brackets was evaluated using a universal testing machine and the debonding patterns were micro-visualized to determine the adhesive remnant indexes of subgroups of specimens.

RESULTS

Within each group, the etch-and-rinse primer (SG1) resulted in higher debonding resistance than self-etch primers (SG2) (p < 0.05), while there was no difference between non-stressed and stressed specimens (p > 0.05). Within each category of test specimens, there was no difference between pre-coated (G1) and non-coated (G2) brackets (p > 0.05). The tested specimens in all categories showed comparable adhesive remnant indexes. However, higher percentages of favorable scores (0 and 1) were obtained for all stressed specimens.

CONCLUSIONS

Short-term cumulative intraoral stresses have no adverse effect on the debonding values of either pre-coated or non-coated brackets when either etch-and-rinse or self-etch primer is used for bonding. Exposure of the bonded brackets to different types of stress reflects favorable debonding patterns.

Effect of 0.12% chlorhexidine and zinc nanoparticles on the microshear bond strength of dentin with a fifth-generation adhesive

Objective:

In this study, we compared the effects of 0.12% chlorhexidine (CHX) and nano zinc oxide (NZO) on the microshear bond strength of dentin with a fifth-generation adhesive after acid etching.

Materials and Methods:

Forty molar teeth were randomly divided into four main groups based on dentin surface treatment technique (a) control (single bond 2); (b) NZO; (c) CHX; and (d) NZO + CHX. In each group, half of the samples underwent thermocycling, with no thermocycling in the other half. Then, failure mode was evaluated under a stereomicroscope. Statistical analysis was performed using t-test, two-way ANOVA, and Chi-squared test.

Results:

The mean microshear bond strength of the groups without thermocycling was more than that of the groups with thermocycling, but there were no statistically significant differences between the groups with and without thermocycling in pair-wise comparisons.

Conclusion:

Pretreatment with NZO and CHX separately and simultaneously had no effect on the microshear bond strength of a fifth-generation adhesive.

Shear bond strength of composite resin to resin-modified glass ionomer cement using 2-hydroxyethyl methacrylate-based and 2-hydroxyethyl methacrylate-free adhesive system

Background:

Sandwich technique combines the properties of both composite resin and glass ionomer cement to make the most of the physical and esthetic properties of each material. Bonding agents improve the wettability of GIC surface and improves the bond between composite resin and GIC. The aim of this study was to evaluate and compare shear bond strength of composite resin to resin modified glass ionomer cement using HEMA-based and HEMA-free adhesive systems. An in vitro study.

Materials and Methods:

Total 30 disc-shaped samples were prepared with resin modified glass ionomer cement (RMGIC). Samples were divided into three groups, each group containing 10 samples. Group I (n=10): Nano-hybrid composite resin (NHCR) was bonded to RMGIC without any adhesive system. Group II (n=10): NHCR was bonded to RMGIC using hydroxyethylmethacrylate (HEMA)-based adhesive system. Group III (n=10): NHCR was bonded to RMGIC using HEMA-free adhesive system. The shear bond strength was tested using Universal testing Machine and the results were calculated using one way ANOVA and Post-Hoc test.

Results:

Maximum shear bond strength was recorded in group III where HEMA-free adhesive used with a mean value of 6.13±1.859 MPa followed by group II where HEMA-based adhesive used with mean value of 4.38±1.533 MPa. The control group showed least shear bond strength.

Conclusion:

Application of HEMA-free adhesive (OptiBond All-In-One) resulted in greater shear bond strength between RMGIC and composite resin than HEMA-based adhesive (Single bond Universal Adhesive).

In vitro comparison of frictional forces of a new polycrystalline ceramic bracket versus metal-insert ceramic bracket before and after aging

OBJECTIVE

The purpose of this study was to compare the friction of two types of polycrystalline ceramic brackets before and after aging.

METHODS

A total of 60 second-upper right premolar brackets were divided into two groups: Clarity™ Advanced (3M Unitek, Monrovia, CA) and Clarity™ (3M Unitek). All brackets had a nominal 0.022-in slot size and a McLaughlin Bennett Travesi (MBT) prescription. Each bracket was submitted to a friction test, using the YL01 UTM universal testing machine (YLE GMBH, Germany) before and after thermocycling. All tests were carried out in the presence of artificial saliva, using .019×.025-in. rectangular stainless steel (SS) archwires (3M Unitek). Bracket slot surfaces were observed under an optical microscope (Olympus CX41, Tokyo, Japan) before and after aging.

RESULTS

Before aging, the Clarity Advanced group showed significantly lower friction than the Clarity group (P=0.011). After aging, the friction of the Clarity Advanced bracket decreased significantly (P<0.001), whereas the friction of the Clarity bracket increased significantly (P<0.001). The microscopic qualitative evaluation showed that the slot surfaces of all aged Clarity brackets revealed important pit corrosion when compared with the original brackets.

CONCLUSIONS

The new Clarity Advanced ceramic bracket shows good physical friction properties due to the various modifications added by the manufacturers.

Shear bond strength of a flash-free orthodontic adhesive system after thermal aging procedure

Background

The aim of this study was to compare the shear bond strength (SBS) of a flash-free and precoated orthodontic adhesive with a compomer orthodontic adhesive before and after thermocycling. The adhesive remnant index (ARI) was also determined for both adhesives.

Material and Methods

The adhesive remnant index (ARI) was also determined for both adhesives. Material and Methods: A total of 120 human premolars were randomly divided into two groups (n=60) according to the orthodontic adhesive used: APC Flash-Free Adhesive Coated Appliance System (APC FF) or Transbond PLUS Color Change Adhesive (TP), as control. A SBS test was performed and ARI value for each specimen was also assessed. Results were analyzed by two-way ANOVA and Tukey's Chi-square test (p<0.05).

Results

SBS values were significantly influenced by thermocycling (p<0.01). Neither the orthodontic adhesive nor the interaction between adhesive and thermocycling statistically affected SBS results (p>0.05).

Conclusions

APC FF and TP showed similar bond strength results. Thermocycling induced a significant decrease in SBS values for the two adhesives tested, without differences between 10,000 and 20,000 thermal cycles. Moreover, APC FF left less adhesive remnants on the enamel compared to TP. Key words:APC Flash-Free, APC cement, aging, orthodontics, resin cements.

A comparative assessment of bracket survival and adhesive removal time using flash-free or conventional adhesive for orthodontic bracket bonding: A split-mouth randomized controlled clinical trial

OBJECTIVES

To compare bracket survival and adhesive removal time between a flash-free and a conventional adhesive for orthodontic bracket bonding.

MATERIALS AND METHODS

Forty-five consecutive patients had their maxillary incisors, canines, and premolars bonded with ceramic brackets using a flash-free adhesive (APC Flash-Free Adhesive, 3M Unitek, Monrovia, Calif) on one side and a conventional adhesive (APCII Adhesive, 3M Unitek) on the other side. The side allocation was randomized. Bracket failure was recorded at 4-week intervals. The adhesive remnant index (ARI) was scored on debond and adhesive removal timed to the nearest second. The primary outcome was adhesive removal time per quadrant. Secondary outcomes were bracket failure rate, time to first-time failure of a bracket, and ARI score on debond. Paired t-tests were used to compare adhesive removal times and ARI scores between the adhesives with P < .05 considered statistically significant.

RESULTS

Bracket failure rates were 4.3% for the flash-free adhesive and 1.9% for the conventional adhesive, with mean times to first-time failure of 31 weeks for the flash-free adhesive and 42 weeks for the conventional adhesive; neither failure rates nor times to first failure were significantly different. Although the flash-free adhesive left significantly more adhesive on the tooth surface after debonding, the adhesive removal times were 22.2% shorter than with the conventional adhesive.

CONCLUSIONS

Bracket survival with the flash-free adhesive was equivalent to the conventional adhesive when ceramic brackets were bonded. Adhesive removal was significantly faster when using the flash-free adhesive, which may result in time savings of more than 20% compared with the conventional adhesive.

Shear bond strength of ceramic and metallic orthodontic brackets bonded with self-etching primer and conventional bonding adhesives

Introduction

Adult patients typically require high-quality orthodontic treatment for ceramic brackets, but some clinicians remain concerned about the bond strength of these brackets. Therefore, the aim of this study was to determine the shear bond strength and de-bonding characteristics of metallic and ceramic brackets bonded with two types of bonding agents.

Methods

In an experimental study done in 2013 in Babol, Iran, 120 extracted human maxillary premolar teeth were randomly divided into four groups as follows: HM group: metallic bracket/conventional bonding agent; SM group: metallic bracket/Transbond self-etching primer; HC group: ceramic bracket/conventional bonding agent; SC group: ceramic bracket/Transbond self-etching primer. Twenty-four hours after thermocycling (1000 cycle, 5 °C–55 °C), the shear bond strength values were measured. The amount of resin remaining on the tooth surface (adhesive remnant index: ARI) was determined under a stereomicroscope. Enamel detachment index was evaluated under a scanning electron microscope. To perform statistical analysis, ANOVA, Kruskal–Wallis, and Tukey post-hoc tests were applied. The level of significance was set at p <0.05.

Results

The mean shear bond strength values (MPa ± SD) were group HM=12.59, group SM=11.15, group HC=7.7, and group SC=7.41. Bond strength differences between groups HM and SM (p=0.063) and between HC and SC (p=0.091) were not statistically significant. There were significant differences between HM and HC and between SM and SC groups (p < 0.05). Insignificant differences were found in ARI among all groups.

Conclusion

Our findings indicated that the metallic brackets had higher bond strengths in comparison with ceramic brackets. In addition, self-etching primer was able to produce fewer bonds compared with the conventional technique. Many samples showed the bracket-adhesive interface failure or failure inside the adhesive.

Microshear Bond Strength of OptiBond All-in-One Self-adhesive Agent to Er:YAG Laser Treated Enamel After Thermocycling and Water Storage

Introduction: This study aimed to compare the microshear bond strength of composite to enamel treated with Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser using a self-etch one step bonding agent. Methods: Seventy-six enamel surfaces were prepared from 38 sound human third molar teeth. Specimens were randomly divided into four groups of 18. The enamel surface in half the specimens was irradiated with Er:YAG laser. One extra specimen from each group was evaluated under a scanning electron microscope (SEM). Composite micro-cylinders were bonded to the specimen surfaces using OptiBond All-In-One (OB) adhesive agent and stored in distilled water for 24 hours. Half the specimens were thermocycled (2000 cycles) and stored in distilled water at 37°C for three months (TW). The microshear bond strength of composite to enamel was measured using a universal testing machine at a crosshead speed of 1 mm/min. The fractured surfaces were evaluated under a stereomicroscope at ×40 magnification to determine the mode of failure. Data were analyzed using repeated measures analysis of variance (ANOVA) and t test. Results: The mean values (±standard deviation) were 17.96 ± 2.92 MPa in OB group, 22.29 ± 4.25 MPa in laser + OB group, 18.11 ± 3.52 MPa in laser + OB + TW group and 9.42 ± 2.47 MPa in OB + TW group. Repeated measures ANOVA showed that laser irradiation increased the microshear bond strength (P < 0.001). Bond strength decreased when the samples were thermocycled and stored for three months (P < 0.001). The interaction effect of water storage and laser treatment on bond strength was significant (P < 0.05). Conclusion: Enamel surface preparation with Er:YAG laser is recommended to enhance the durability of the bond of self-etch bonding systems to enamel.

Comparison of enamel-bracket bond strength using direct- and indirect-bonding techniques with a self-etching ion releasing S-PRG filler

This in vitro study compared the shear bond strength (SBS) and adhesive remnant index (ARI) of two systems for bonding orthodontic brackets to enamel. The first system involved a self-etching primer (Beauty Ortho Bond, BO) containing surface pre-reacted glass filler. The second involved a primer applied with phosphoric acid etching (Transbond XT, TX). Ninety-six extracted human premolars were divided into eight groups: Group I (TX/direct bonding), Group II (TX/indirect bonding), Group III (BO/direct bonding), and Group IV (BO/indirect bonding). Groups V-VIII were identical to Groups I-IV, respectively, but were also subjected to 1,500 thermal cycles between 5 and 55°C. ARI was scored by binocular microscopy. SBS was analyzed by three-way ANOVA and the Bonferroni test. ARI was analyzed by the chi-squared test. The BO groups showed lower SBS and ARI results than the TX groups. SBS was significantly influenced by the primer material, bonding technique, and thermal cycling.

Shear bond strength of orthodontic brackets to enamel after application of a caries infiltrant

OBJECTIVE

To examine differences in the shear bond strength of orthodontic brackets on differently mineralized enamel surfaces after applying a caries infiltrant or conventional adhesive.

MATERIALS AND METHODS

A total of 320 bovine incisors were assigned to eight pretreated groups, and the shear force required for debonding was recorded. Residual adhesive was evaluated by light microscopy using the adhesive remnant index. Statistical analysis included Kolmogorov-Smirnov, analysis of variance (ANOVA), and Scheffé tests.

RESULTS

The highest bond strength (18.8 ± 4.4 MPa) was obtained after use of the caries infiltrant. More residual adhesive and fewer enamel defects were observed on infiltrated enamel surfaces. Brackets on demineralized enamel produced multiple enamel defects.

CONCLUSIONS

Acceptable bond strengths were obtained with all material combinations. A caries-infiltrant applied before bracket fixation has a protective effect, especially on demineralized enamel.

In vitro evaluation of microleakage under ceramic and metal brackets bonded with LED and plasma arc curing

AIM

The aim of the present study was to evaluate these two high intensity light curing units regarding microleakage beneath metal and ceramic brackets.

MATERIALS AND METHODS

A total of 60 freshly extracted human premolar teeth were randomly divided into four groups of 15 samples; group I: Metal bracket + LED cured, group II: Ceramic bracket + LED cured, group III: Metal bracket + plasma arc cured, group IV: Ceramic bracket + plasma arc cured. After photopolymerization, the teeth were immersed in water and thermocycled (500 cycles between 5 and 55). Specimens were further sealed with nail varnish and stained with 5% basic fuchsin for 24 hours. All of the teeth were sectioned with two parallel longitudinal occlusogingival cuts and examined under a stereomicroscope. The microleakage was measured with a digital caliper and scored from 0 to 3 for marginal microleakage at the bracket-adhesive and adhesive-enamel interfaces from both the occlusal and gingival margins.

RESULTS

Microleakage was detected in all groups. The plasma arc cured group showed less microleakage than light emitting diode (LED) cured in all samples at the enamel-adhesive interface at the gingival margin (ceramic brackets, p = 0.009 and metal brackets, p = 0.005). The plasma arc cured samples showed less microleakage than LED cured in metal brackets at the adhesive-brackets interface at the occlusal margin (p = 0.033). While curing with an LED unit, ceramic brackets displayed significantly less microleakage than metal ones at the gingival margin of adhesive-enamel interface (p = 0.013). The gingival margin in all groups exhibited higher microleakage compared with those observed in occlusal sides in all sample groups (p < 0.001).

CONCLUSION

1. LED units cause more microleakage than plasma arc units. 2. In all groups the microleakage at the gingival margin is greater than the occlusal margin.

CLINICAL SIGNIFICANCE

The microleakage formation permits the passage of bacteria and oral fluids initiating white spot lesions beneath the bracket base.