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

Orthodontic bonding in special circumstances

This clinical paper provides an in-depth exploration of advanced techniques for bonding orthodontic attachments under special circumstances. Challenges arise when bonding brackets to non-enamel surfaces, such as dental restorations, and in conditions such as amelogenesis imperfecta, which affect enamel integrity. Distinct approaches required for bonding to different restorative materials, including glassy ceramics, zirconia, resin composites and metals, are outlined. Moreover, we describe strategies to manage bonding in conditions including amelogenesis imperfecta, hypodontia and microdontia in a multidisciplinary context.

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.

Cellulose Nanocrystal/Poly(ethylene glycol) Composite as an Iridescent Coating on Polymer Substrates: Structure-Color and Interface Adhesion

The broad utility as an environmentally friendly and colorful coating of cellulose nanocrystal (CNC) was limited by its instability of coloration, brittleness, and lack of adhesion to a hydrophobic surface. In the present work, a neutral polymer, poly(ethylene glycol) (PEG) was introduced into CNC coatings through evaporation-induced self-assembly (EISA) on polymer matrices. The structure-color and mechanical properties of the composite coating or coating film were characterized by UV-vis spectroscopy, polarized light microscopy (PLM), scanning electron microscopy (SEM), wide-angle X-ray diffraction (WXRD), and tensile tests. Results showed that the reflective wavelength of the iridescent CNCs could be finely tuned by incorporation of PEG with varied loadings from 2.5 to 50 wt %, although the high loading content of PEG would produce some side effects because of the severe microphase separation. Second, PEG played an effective plasticizer to improve the ductility or flexibility of the CNC coating or coating film. Furthermore, as a compatibilizer, PEG could effectively and tremendously enhance the adhesion strength between CNCs and neutral polymer matrices without destroying the chiral nematic mesophases of CNCs. Environmentally friendly CNC/PEG composites with tunable iridescence, good flexibility, and high bonding strength to hydrophobic polymer matrices are expected to be promising candidates in the modern green paint industry.

Comparison of shear bond strength of orthodontic brackets using various zirconia primers

Objective

The aim of this study was to compare the shear bond strength (SBS) of orthodontic brackets bonded to zirconia surfaces using three different zirconia primers and one silane primer, and subjected to thermocycling.

Methods

We designed 10 experimental groups following the surface treatment and thermocycling. The surface was treated with one of the following method: no-primer (NP), Porcelain Conditioner (PC), Z-PRIME Plus (ZP), Monobond Plus (MP) and Zirconia Liner Premium (ZL) (n=20). Then each group was subdivided to non-thermocycled and thermocycled groups (NPT, PC, ZPT, MPT, ZLT) (n=10). Orthodontic brackets were bonded to the specimens using Transbond™ XT Paste and light cured for 15 s at 1,100 mW/cm². The SBS was measured at a 1 mm/min crosshead speed. The failure mode was assessed by examination with a stereomicroscope and the amount of bonding resin remaining on the zirconia surface was scored using the modified adhesive remnant index (ARI).

Results

The SBS of all experimental groups decreased after thermocycling. Before thermocycling, the SBS was ZL, ZP ≥ MP ≥ PC > NP but after thermocycling, the SBS was ZLT ≥ MPT ≥ ZPT > PCT = NPT (p > 0.05). For the ARI score, both of the groups lacking primer (NP and NPT) displayed adhesive failure modes, but the groups with zirconia primers (ZP, ZPT, MP, MPT, ZL, and ZLT) were associated with mixed failure modes.

Conclusions

Surface treatment with a zirconia primer increases the SBS relative to no-primer or silane primer application between orthodontic brackets and zirconia prostheses.