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Light-curing

Light-curing
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User's Guide to the key factors for selecting the right curing device Clinical relevance of light-curing systems Requirements of clinicians Compatibility with dental materials Light intensity Radiometry All about light probes Modern batteries last longer Ergonomics & design Quality vs. cost Checklist Bluephase® Style – The smallest LED for every use A quick guide to achieving optimum light-curing results Glossary of most commonly used terms in photopolymerization Literature

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Clinical relevance of light-curing More than just a “necessary evil” What is the first thing you think of at the mention of the following questions relating to possible problems in your dayto-day work: ➡ ➡ ➡ How often and for what reasons do postoperative sensitivities occur in your patients? When did you last replace a filling because of premature loss? What are the reasons for retention loss in high-quality ceramic restorations? Do these questions remind you of your curing light? Curing lights are the number one source of error in the processing of light-cured dental materials...

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Questions from the (dental) practice As the proverb says, ‘The chain is only as strong as its weakest link’. Similarly, light-curing materials only perform as intended by their manufacturer if they receive the required amount of light energy and appropriate blue-violet wavelengths for polymerizing them [1]. There are a number of questions that clinicians should answer before they decide on a curing light, for instance: ➡ ➡ ➡ ➡ ➡ “What light intensity is required?” “What spectral emission range is required for the materials I use in my practice?” “What is the ideal light-curing technique?”...

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Sufficient curing, the main objective of the treatment Fig.: The top surface appears to be correctly cured (green) in both the entirely cured (left) and the insufﬁciently cured restoration. The risk presented by insufﬁcient polymerization (grey) in deep areas of the restorations cannot be identiﬁed from the surface. Sufficient curing is the prime concern of polymerization. A restoration made of light-curing materials will only be a longterm success if it is sufficiently cured. Insufficient polymerization has been shown to have the potential to cause a number of adverse consequences: ➡ ➡ ➡ ➡...

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Compatibility with dental materials The various photoinitiators To convert a monomer into a polymer, photoinitiators are required. The photoinitiators decompose into radicals when irradiated with light and cause the monomers to polymerize. Camphorquinone is the most commonly used initiator. Camphorquinone absorbs light in the wavelength range between approx. 390 and 510 nm and displays a yellow colour, which is the complementary colour to blue light. Unfortunately, the yellow colour of champhorquinone affects the shade of the cured restoration [28]. Although the initiator almost completely...

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Wavelength range Photoinitiator: camphorquinone Photoinitiator: acyl phosphine oxide, e.g. Lucirin TPO LED curing light of the 2nd generation with monowave LED Bluephase® Style with Polywave® LED Source: R&D Ivoclar Vivadent AG, Schaan, 2014 The ability of a curing light to cure all dental materials and photoinitiator systems essentially depends on the spectral emission of the curing light. Given their broadband emission spectrum, halogen lights were able to activate the entire range of initiators without any problems. Conventional secondgeneration LED lights are not automatically suitable...

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Different materials different requirements Composite curing Fig.: Tetric EvoCeram® Bulk Fill and Tetric EvoFlow® Bulk Fill Dental composite curing is the most important indication of curing lights. The quality of the composite cure can be determined by investigating certain properties of the cured material. Composites undergo changes in hardness, flexural strength and elasticity in the course of the polymerization process. The depth of cure is directly related to the irradiance of the curing light. Spectroscopic measurement systems such as infrared spectroscopy, are useful in determining...

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Curing through ceramic materials Inappropriate curing of adhesives results in a weakened shear bond strength of the adhesive bond on enamel and dentin. Camphorquinone is often used as a photoinitiator in lightcured adhesive systems. However, camphorquinone is subject to progressive changes over time in highly acidic formulations. This presents a problem in self-etch adhesives in particular. This issue is often circumvented by adding large quantities of camphorquinone or by using an acid-resistant initiator system such as acyl phosphine oxide (e.g. Lucirin TPO). It is therefore advisable to...

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Removal of excess material Curing of fissure sealants Until recently, processing adhesive luting composites was considered difficult because of the inconvenient removal of excess material. Modern luting composites (e.g. Variolink Esthetic) are designed for easy clean-up because they allow the excess material to be pre-cured to an ideal consistency with a short burst of light and then removed with a scaler. The fissure sealants available on the market are predominantly filled or unfilled one- or two-component systems. [73]. They are mostly based on methacrylate (e.g. Bis-GMA). A distinction...

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Wavelength range Conventional LED units of the 2nd generation Broadband LED units of the 3rd generation, e.g. Bluephase Style Relative intensity In order to safely use the dental materials in their practice, operators should be furnished with a “negative” list of all the incompatible materials by the manufacturers of conventional LED lights. However, such lists are often not to hand or they are incomplete. Using a curing device that emits light in a broadband spectrum is therefore the only way to ensure that a reliable cure is achieved. Relative intensity Relative intensity Acyl phosphine...

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