Laser Light-Curing Unit Key Element in Deep Composite Restoration

Alireza Sadr, DDS, PhD

A patient presented with an old and failing amalgam restoration on a first molar that showed signs of dentin cracking. The patient was anesthetized, rubber dam isolation was achieved, and the amalgam and any secondary decay was removed and dentin cracks prepared. A sectional matrix was placed, and a deep gingival proximal margin was formed. Because an attempt was made to remove any crack as deeply as possible supragingivally in the mesial box, the gingival margin was at least 6-mm deep from the top of the matrix. The proximal margin was bonded and sealed using a multistep adhesive system, and circumferential walls and a marginal ridge were formed using a universal hybrid composite in a single step after bonding. Light-curing was accomplished with a laser light-curing unit (Monet^®, CAO Group, Inc., caogroup.com). Because of the depth of the preparation, an ultra-high molecular weight polyethylene continuous fiber material was used to bridge the pulpal floor cracks, mitigate stresses, and reinforce the composite. Proximal and buccolingual walls were created with composite, and a polyethylene fiber mesh was wetted with a bonding agent and placed over the tooth with a thin layer of the hybrid composite. Close adaptation of the fiber material against the cracked dentin was achieved, the fiber-reinforced composite was light-cured, and a final occlusal layer of the hybrid composite was placed and light-cured.

Key Takeaways

Dental light-curing units have evolved to improve the degree of polymerization that can be achieved in deep preparations. Unlike light from other sources, laser light is collimated, which means that all of the rays are parallel to each other-an important characteristic, as the light beam does not diverge over longer distances in the way that light from an LED source does.

The Monet laser light-curing unit, in unpublished optical coherence tomography experiments by the author, demonstrated effective curing of a 4-mm deep composite restoration from as far away from the surface as 8 mm in 3 seconds, and the restorations exhibited less debonding than those cured by a standard LED light-curing unit for 20 seconds. The Monet demonstrated the capability to cure composite restorations to their depth, regardless of its distance from them.

In this case, the Monet laser light-curing unit helped ensure a predictable bond and complete polymerization of the adhesive and composite that were placed to create a proximal wall and marginal ridge as well as the fiber-reinforced composite that was placed in the deepest part of the preparation. The consistent energy delivered by this light-curing unit is a "game changer" not only for thick increments of bulk-fill composites but also for thinner increments of light-cure resins and base materials used in deeper preparations.

About the Author
Alireza Sadr, DDS, PhD
Associate Professor and Vice Chair, Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, Washington

Figures and Images

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Figure 1

Fig 1. Occlusal view of first molar after removal of a failing mesial-occlusal-lingual amalgam restoration that was showing signs of dentin cracks. Complete elimination of such cracks can be challenging.

Figure 2

Fig 2. The Monet laser curing light that was used to polymerize the materials in this case (CLEARFIL™ SE BOND 2 adhesive system and CLEARFIL MAJESTY™ ES-2 Universal universal hybrid composite, Kuraray Noritake) has a head design that fits into tight molar spaces and facilitates the light-curing process in 3 seconds.

Figure 3

Fig 3. After the creation of the proximal and buccolingual walls with composite, a polyethylene fiber mesh (Ribbond® Ultra THM, Ribbond) was cut to the desired length, wetted with a solvent-free bonding agent, and placed over the tooth with a thin layer of the composite.

Figure 4

Fig 4. Occlusal view of the fiber-reinforced composite after it was closely adapted (ie, laminated) to the cracked dentin and light-cured using the Monet laser curing light.

Figure 5

Fig 5. Occlusal view of the final layer of the hybrid composite, which was placed and cured at once using the laser curing light. The accelerated curing time provided by the Monet laser curing light significantly saves chairtime, particularly for multistep procedures, such as the one presented in this case, that involve meticulous bonding and fiber lamination to complete the restoration.