Flowable Injection Technique. What to do to avoid air bubbles in composite restorations?

Article by Dr. Michał Jaczewski

COMPOSITE RESTORATIONS IN DENTISTRY

Composite restoration is the most common procedure performed by the dentist. There are many restorative techniques and a variety of restorative materials used in dentistry. Regardless of the type of material, the method of restoration and where it is applied, common issue is air bubbles in or at the surface of the composite layers. The composite restoration should be homogeneous to ensure the tightness of the filling and its durability. Repairing bubble defects is tedious and sometimes requires the replacement of the filling or part of it. Depending on the type of composite (flowable or paste composite) and/or the placement technique, the amount of defects may vary, but there are several causing factors.

MATERIAL CHOICE

In the Flowable Injection Technique, we use flowable composites, which obviously flow easily but are also sensitive to incorrect application. The first cause of forming air bubbles is the homogeneity of the material itself. Bubbles can be incorporated in the syringe at the manufacturing stage or during use. By using premium products, we can be sure that the highest quality material is supplied, and that the structure and design of the syringe allows for proper operation to reduce the formation of air bubbles within the material.

IMPORTANCE OF SYRINGE DESIGN 

CLEARFIL MAJESTY™ ES Flow composite is designed to prevent the formation of air bubbles during dispensing. The special design of the syringe and plunger limit the possibility of dripping as well as backflow of the material during or after dispensing.

A unique safety feature inside the syringe is the special O-ring construction which prevents the material from flowing after pressure is released and at the same takes care for minimal retraction but avoiding the plunger from retracting too much.

RETRACTION OF PLUNGER

Another cause of air bubble formation is the incorporation of air into the syringe by deliberate retraction of the plunger. If the practitioner or ancillary staff have a habit of retracting the plunger after administering the composite, they may cause air to enter the syringe. During a following use the air will more than likely show up in the restoration as an air void.

IMPORTANCE OF PRESSURE ON THE INDEX

In the Flowable Injection Technique, we use a silicone index in which we apply the material to build up the tooth. The index should fit tightly to the tooth and should not move or being moved during injection. If it does air bubbles may show up. Pressing and then releasing the index will cause a suctioning effect and pull the composite away from the tooth as well as from the index. To avoid defects, constant pressure on the index should be maintained from the moment the material is injected until polymerisation.

Various modifications of the silicone index can be used to limit its mobility and reduce the risk of uncontrolled pressure on the tooth. Such an example is the index made on the interlip ("one yes one no") model, which provides a very high degree of stability as well as working safety.

WIDTH OF THE INJECTION HOLE

Another cause for getting air in the restoration is the width of the injection hole. If the hole is too tight, the index can be moved by the application tip during insertion or application. To avoid this problem, the hole could be widened to allow free insertion as well as manipulation of the tip during injection. A wider opening also allows any air to escape during dispensing. Most important , however, is to apply the material at continuous pressure and avoiding pulling out and reinserting the tip into the index. This may result in a non-uniform composite layer.

Would you like to know more about Flowable Injection Technique? Read the insightful and inspirational interview with Dr. Michal Jachzewski.

Dentist:

MICHAL JACZEWSKI

Michał Jaczewski graduated from Wroclaw Medical University in 2006 and today runs his private practice in the city of Legnica, Poland. He specializes in minimally invasive dentistry and digital dentistry and is the founder of the Biofunctional School of Occlusion. Here he lectures and runs workshops with focus on full comprehensive patient treatments.

• 2024. gada 13. febr.

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