The effects of primer precuring on the shear bond strength between gold alloy surfaces and metal brackets

Shear bond strength of orthodontic brackets bonded with primer-incorporated orthodontic adhesives and unpolymerized 3-dimensional printing materials on 3-dimensional-printed crowns

INTRODUCTION

The use of 3-dimensional (3D) printing techniques in fabricating crowns has increased the demand for bracket bonding onto these surfaces. The objective was to evaluate the shear bond strength (SBS) of orthodontic brackets bonded onto 3D-printed crowns using primer-incorporated orthodontic adhesives and 3D printing materials as orthodontic adhesives.

METHODS

A total of 160 crowns were printed with two 3D printing materials, DentaTOOTH (Asiga, Sydney, Australia) (group A) and NextDent C&B Micro Filled Hybrid (3D Systems, Soesterberg, Netherlands) (group N). Each group was randomly divided into 4 adhesive subgroups (n = 20): Transbond XT (for groups A [ATX] and N [NTX]; 3M Unitek, Monrovia, Calif), Ortho Connect (for groups A [AOC] and N [NOC]; GC Corporation., Tokyo, Japan), Orthomite LC (for groups A [AOM] and N [NOM]; Sun Medical, Co Ltd, Moriyama, Shiga, Japan), and unpolymerized liquid state of 3D printing resin (for groups A [AA] and N [NN]). SBS was measured with a universal testing machine at a crosshead speed of 0.5 mm/min. The adhesive remnant index and the mode of failure were analyzed under the microscope. Statistical analysis was performed at a significance level of α = 0.05.

RESULTS

When used as adhesives (AA and NN), 3D printing materials showed no statistically significant difference in SBS compared with Transbond XT (ATX and NTX, respectively). In group N, NN showed a significantly higher SBS than primer-incorporated orthodontic adhesives (NOC and NOM; P <0.001). Adhesive failures were only observed in primer-incorporated orthodontic adhesives (AOC, NOC, AOM, and NOM).

CONCLUSIONS

Primer-incorporated orthodontic adhesives, as well as unpolymerized 3D printing materials employed as orthodontic adhesives on 3D-printed crowns, exhibited comparable bonding strength to Transbond XT without surface modification. Despite variations in adhesive-related factors, all measurements stayed within clinically acceptable ranges, highlighting the potential of these materials for orthodontic bonding on 3D-printed crowns, simplifying clinical procedures without compromising bond strength.

Evaluation of the Curing of the Primer on Shear Bond Strength of Orthodontic Brackets: An Original Research

Background

The aim of this study was to evaluate the effect of separately curing the unfilled resin for increased bond strength of the orthodontic brackets as the literature shows both studies that support and contradict this aspect.

Methodology

The sample consisted of 120 specimens randomly grouped into four of 30. The tooth was cleaned of tissue and debris and stored in a distilled water solution until the procedures of bonding. The surface of the enamel was conditioned with pumice, and acrylic blocks were designed for the tooth to be mounted onto them. The buccal surfaces of all the teeth were prepared by etching the enamel with 37% phosphoric acid for a time period of 30 seconds and washed for 20 seconds under running water. Stainless steel brackets (Victory Series™ MBT, 0.022 Slot) were used for all the samples in the study, and the bonding procedure was conducted on the same day for all the groups. The artificial saliva was used for the storage of samples for 24 h after bonding, and shear bond strength testing was conducted using an Instron machine in shear or peel mode at a crosshead speed.

Results

The highest mean bond strength calculated was for the conventional technique (17.45 mpa), while it was the lowest for no primer adhesive (11.21 mpa). Group IV had a greater distribution of ARI scores than groups I, II, and III.

Conclusion

Group IV achieved the highest bond strength when compared to other groups, with an ARI score of 3. Group III had less bond strength, likely due to incomplete curing of the primer due to insufficient exposure to light. Transbond XT can be used without primer, making bonding, debonding, and cleaning procedures easy and less time-consuming.

Shear strength of metal brackets using LED lamps with different wavelengths: An in vitro comparative study

AIM

To evaluate the shear strength of Orthocem and BracePaste polymerizable cement light-cured with light-emitting diode (LED) units with different wavelengths (Bluephase N) with their high power, low power, and soft start programs in the bonding of metal brackets.

MATERIALS AND METHODS

In vitro experimental research was performed. Mini Roth 0.022 metal brackets (Roth Orthometric brackets) were used. The adhesives were placed on the metal brackets with Orthocem and BracePaste resin cement. To compare the average strengths, the analysis of variance (ANOVA) test was used (P < 0.05).

RESULTS

The average shear strength was better with Bracepaste polymerizable cement compared to Orthocem cement in all its high power, low power, and soft star programs; the highest was Bracepaste with soft start of 26.52 MPa, and the lowest was Orthocem with soft start of 13.92 MPa. When evaluating the differences, it was found that these were statistically significant in all groups (P < 0.05).

CONCLUSIONS

Differences were found in the shear strength of light-curing Orthocem and Bracepaste light-curing cement cured with LED units with different wavelengths in bonding metal brackets to the tooth in vitro.

Influence of Primer Pre-curing and Co-curing on Shear Bond Strength of Orthodontic Brackets Using Three Light-cure Adhesive Systems: An In Vitro Study

AIM

This study aimed to evaluate the shear bond strength (SBS) of orthodontic brackets with primer pre-curing and co-curing using three light cure adhesive systems.

MATERIALS AND METHODS

In this in vitro study, 102 extracted premolar teeth mounted on self-cure acrylic resin blocks were separated into six groups based on primer pre-curing and co-curing with each group receiving stainless steel orthodontic premolar brackets bonded to the buccal surfaces. The following adhesives were used: Transbond XT (3M Unitek, CA, USA), Orthofix (Anabond Stedman, India), and Enlight (Ormco, India). In the groups with pre-curing, the primer was pre-cured for 20 seconds while in the groups with co-curing, the primer and adhesive were cured together. Shear bond strength tests and Adhesive Remnant Index (ARI) were assessed followed by an scanning electron microscope (SEM) view (×3000) of the enamel surface after debonding. Statistical analysis was done using a one-way analysis of variance (ANOVA) test.

RESULTS

The descriptive statistics in the pre-cured groups showed a statistically significant difference. The highest mean SBS was observed for group I, i.e., Transbond XT with primer pre-curing (20.56 ± 3.22 MPa). The lowest mean SBS was for group IV, i.e., Orthofix with primer co-curing (7.57 + 0.49 MPa). The results of ANOVA revealed a significant difference among the groups. The ARI scoring and the SEM analysis also confirmed this finding.

CONCLUSION

Shear bond strength of orthodontic brackets with primer pre-curing showed a better bond strength than brackets with co-curing. The ARI data suggested that the majority of bracket failure happened at the resin-bracket interface. Scanning electron microscope analysis also confirmed the ARI and SBS findings.

CLINICAL SIGNIFICANCE

During the bonding of orthodontic brackets, the primer can be co-cured where the primer and adhesive resin are cured simultaneously or pre-cured where the primer is cured separately. Most orthodontic clinicians to save time co-cure primer. Both these methods affect the SBS of brackets.

Orthodontic Bonding: Review of the Literature

BACKGROUND

Patients seeking orthodontic treatment are increasing, and clinicians often have to place brackets on various surfaces aside from enamel. It is crucial to know what materials or instruments are required to bond brackets to each surface.

OBJECTIVE

This study aims to serve as a clinical guideline for the safest and most effective approaches taken to condition various surfaces for bonding to orthodontic brackets and provide background knowledge on the subject.

MATERIALS AND METHODS

PubMed and EBSCO databases were searched, along with the use of Google Scholar search engine, to obtain relevant articles published in English in peer-reviewed journals, from 1955 to 2020. Keywords used were Shear bond strength; Orthodontic bracket; Base design; Etching; Sandblasting; Laser; Conditioning; Enamel; Ceramic; Porcelain; Gold; Amalgam; Composite.

CONCLUSION

Even though orthophosphoric acid is the most widely used enamel conditioning agent, laser etching should be considered to avoid enamel decalcification. Hydrofluoric acid is the current standard for ceramic conditioning; however, its use intraorally should be minimized due to its toxicity. Orthophosphoric acid, CoJet-Sand air abrasion, and laser etching are viable alternatives for conditioning ceramic. Monobond Etch & Prime is toxic and should not be used intraorally. Composite can be conditioned by bur roughening, and the use of ceramic brackets is recommended. Amalgam and gold surfaces can be conditioned adequately by air abrasion. Despite the claims of many authors, the maximum shear forces that orthodontic brackets are subjected to are not 6-8 mega pascal (MPa). Further investigation is required in that regard. More in vivo studies need to be performed to confirm the in vitro results.

Orthodontic bracket bonding to glazed full-contour zirconia

Objectives

This study evaluated the effects of different surface conditioning methods on the bond strength of orthodontic brackets to glazed full-zirconia surfaces.

Materials and Methods

Glazed zirconia (except for the control, Zirkonzahn Prettau) disc surfaces were pre-treated: PO (control), polishing; BR, bur roughening; PP, cleaning with a prophy cup and pumice; HF, hydrofluoric acid etching; AA, air abrasion with aluminum oxide; CJ, CoJet-Sand. The surfaces were examined using profilometry, scanning electron microscopy, and electron dispersive spectroscopy. A zirconia primer (Z-Prime Plus, Z) or a silane primer (Monobond-S, S) was then applied to the surfaces, yielding 7 groups (PO-Z, BR-Z, PP-S, HF-S, AA-S, AA-Z, and CJ-S). Metal bracket-bonded specimens were stored in water for 24 hr at 37℃, and thermocycled for 1,000 cycles. Their bond strengths were measured using the wire loop method (n = 10).

Results

Except for BR, the surface pre-treatments failed to expose the zirconia substructure. A significant difference in bond strengths was found between AA-Z (4.60 ± 1.08 MPa) and all other groups (13.38 ± 2.57 - 15.78 ± 2.39 MPa, p < 0.05). For AA-Z, most of the adhesive remained on the bracket.

Conclusions

For bracket bonding to glazed zirconia, a simple application of silane to the cleaned surface is recommended. A zirconia primer should be used only when the zirconia substructure is definitely exposed.

Effect of silica coating on bond strength between a gold alloy and metal bracket bonded with chemically cured resin

OBJECTIVE

The purpose of this study was to evaluate the effects of three different surface conditioning methods on the shear bond strength (SBS) of metal brackets bonded directly to gold alloy with chemically cured resin.

METHODS

Two hundred ten type III gold alloy specimens were randomly divided into six groups according to the combination of three different surface conditioning methods (aluminum oxide sandblasting only, application of a metal primer after aluminum oxide sandblasting, silica coating and silanation) and thermocycling (with thermocycling, without thermocycling). After performing surface conditioning of specimens in accordance with each experimental condition, metal brackets were bonded to all specimens using a chemically cured resin. The SBS was measured at the moment of bracket debonding, and the resin remnants on the specimen surface were evaluated using the adhesive remnant index.

RESULTS

Application of metal primer after aluminum oxide sandblasting yielded a higher bond strength than that with aluminum oxide sandblasting alone (p < 0.001), and silica coating and silanation yielded a higher bond strength than that with metal primer after aluminum oxide sandblasting (p < 0.001). There was no significant change in SBS after thermocycling in all groups.

CONCLUSIONS

With silica coating and silanation, clinically satisfactory bond strength can be attained when metal brackets are directly bonded to gold alloys using a chemically cured resin.

Effects of silanation time on shear bond strength between a gold alloy surface and metal bracket

Objective

We aimed to investigate the effects of silanation time on the shear bond strength (SBS) of metal brackets on gold alloy in a silicoating procedure and compare the SBS of metal brackets on gold alloy and enamel.

Methods

Type III gold alloy plates were sandblasted with 30-µm silicon dioxide. Excess particles were removed with gentle air after silica coating, and silane was applied. Maxillary central-incisor metal brackets were bonded to each conditioned alloy surface with a light curing resin adhesive for 1 s, 30 s, 60 s, or 120 s after applying silane. The brackets were also bonded to 36 upper central incisors with the same adhesive. All samples were cured for 40 s with a light emitting diode curing light. The SBS was tested after 1 h and after 24 h. The adhesive remnant index (ARI) of the samples was also compared.

Results

The 60-s and 120-s silanation time groups showed a higher SBS than the other groups (p < 0.05). Samples tested after 24 h showed a significantly higher SBS than did the samples tested after 1 h (p < 0.05). The 1-s group showed higher ARI scores. The one-way analysis of variance and Student-Newman-Keuls test showed that the SBS values of the 60-s and 120-s silanation time groups were not significantly different from the SBS values of enamel.

Conclusions

Adequate silanation time is required to produce sufficient bond strength during silicoating.