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Bulk Fill Composites

Opus Bulk Fill APS and Opus Bulk Fill Flow APS composites: effectiveness and time saving at the service of odontology
Author: Prof. Dr. Marcos Barceleiro

There is a trend, in current dentistry, of simplifying and accelerating clinical procedures, which has been followed by the manufacturers of materials. That demand is reinforced by patients and professionals who want to have faster procedures without compromising quality.

Such simplification has been noticed in several specialties. More specifically in restorative and esthetic dentistry. Two groups of materials have been undergoing the greatest modifications, aiming at simplifying and accelerating procedures – adhesive systems and composites. It is widely publicized that the new universal self-etching adhesive systems with the 10-MDP monomer such as Ambar Universal APS have chemical characteristics that allow the professional to carry out adhesive procedures in a simplified way and get excellent results in the laboratorial tests1 and in clinical follow up studies.

However, composites in general had not been following that evolution, and one of the main problems related to that group of materials, known for the tension generated by the polymerization shrinkage, still made the direct restorative techniques, with the use of small increments with no more than 2mm of thickness, the most recommended and the most frequently carried out technique by dental professionals. That technique, besides making restorations take a long time to be complete, would also bring two more inherent risks: the risk of creating bubbles on the inside of the restoration (which may cause mechanical problems for the restoration), and a greater risk of contamination between each increment.

Although that is a very current discussion, the problem is old and several attempts to develop a material that could be used without those risks have been tried in the last years. Some of those attempts even proved to be reasonable in initial lab tests3, however, the clinical evaluations4 that followed through did not show the same favorable results and many ideas were discarded.

Nevertheless, in the last decade, new composites with low shrinkage rates after polymerization known as the bulk fill composites (Opus Bulk Fill APS and Opus Bulk Fill Flow APS) were made available in the market. These composites seem to be effective in allowing dentists to carry out direct restorations without the need to use the layering technique, that is, with the use of increments of up to 5mm, which, many times, allows for restorations in one single increment. As they are usually more translucent, to provide correct photopolymerization of the deepest areas of those larger increments, those new materials do not show the appropriate esthetics for anterior teeth involving esthetic veneers. Thus, bulk fill composites (Opus Bulk Fill APS and Opus Bulk Fill Flow APS) are recommended only for restorations on posterior teeth (all faces) or anterior teeth when there is no esthetic implication.

Basically, there are two types of bulk fill composites available in the market: the low viscosity bulk fill composites (Opus Bulk Fill Flow APS), known as bulk fill flow composites, and the medium viscosity bulk fill composites (similar consistency of most of the composites), known as regular bulk fill composites (Opus Bulk Fill APS). The bulk fill flow composites (Opus Bulk Fill Flow APS) show inferior mechanical strength, and, therefore, when used in cavities that involve the occlusal face, must be covered on that face by a traditional composite or by a regular bulk fill composite. The regular bulk fill composites (Opus Bulk Fill APS) can be used for the complete filling of cavities where they are used.

In both cases, the manufacturers found different ways to decrease the polymerization shrinkage rate. Some manufacturers promote changes in the organic matrix of the composite, with the incorporation of new monomers which promote less shrinkage during polymerization. Others promote changes in the composition, quantity, and average size of the load particles, with the same objective. However, recent studies5 have already demonstrated that the key for the success of all bulk fill type composites is the capacity to photopolymerize the deeper layers (beyond the traditional 2mm).

That is why most of bulk fill composites are more translucent. They allow for the light to penetrate deeper, thus allowing for the adequate photopolymerization of the deepest layers.
It is in that area that the FGM bulk fill composites Opus Bulk Fill APS (regular) and Opus Bulk Fill Flow APS (flow) stand out in a positive way. They have, in their formula, a new FGM-patented photoinitiator, the APS, which has proven to promote a greater polymerization conversion and allow for the photopolymerization of deeper portions of increments.

As we are dealing with something new, some questions have arisen as the use of those materials became more and more common in the clinics. The first of those fears was related to the risk of post-operative sensitivity, since the use of larger increments would promote the realization of restorations with greater risk of tension on the cuspids (which happened with the traditional composites and was known to be one of the possible causes of post-operative sensitivity). However, several studies7, 8 have already demonstrated that the risk of post-operative sensitivity when a restoration is done with the use of bulk fill composites (Opus Bulk Fill APS and Opus Bulk Fill Flow APS) is the same of a traditional composite. Another fear was related to the durability of the restorations done with those new materials. Likewise, there are already clinical studies showing the reliability and durability of the restorations carried out with those new materials.

A piece of information that is of critical clinical importance and that completely justifies the use of those materials for direct restorations is the economy of time when they are used. For requiring a smaller number of operatory steps, with the possibility of being carried out many times with one single increment (cavities that are less than 5mm deep), restorations with those materials can be completed 70% faster when compared to restorations done using the incremental technique.

The time-saving advantage can promote a significant increase in the productive capacity of the dental office (in terms of number of restorations done throughout a day) or, in another analysis, can promote a considerable reduction in costs involved in a direct restoration (since a shorter clinical time means lower costs for a dental office).
In conclusion, bulk fill composites are recommended for direct restoration in class I occlusal, class II and class V cavities, being the two last ones in the case of no esthetic implications. And, thinking of a summarized clinical step-by-step guidance, they should be used in the following way:

Bulk fill flow composite (Opus Bulk Fill Flow APS):
After the use of the adhesive system, this composite may be inserted in increments of up to 4mm, provided that at least 1mm is left free close to the occlusal face of the teeth. Once inserted, this composite must be photopolymerized adequately for at least 20 seconds, with equipment with minimum potency of 450mW/cm2 with wavelength of 400-500nm. Then, the occlusal portion of the restoration must be finalized with a traditional composite, by means of the incremental technique or by a regular bulk fill composite, which can be used in one single increment that must also be photopolymerized for at least 40 seconds. After the finalization of the restoration, the absolute isolation must be removed, the occlusion must be checked, and the finishing must be done and the restoration can be polished.

Regular bulk fill composite (Opus Bulk Fill APS):
After the use of the adhesive system, this composite can be inserted in increments of up to 5mm and they can fill up the whole cavity if that is the case. Once inserted, the sculpting may be carried out and the composite must then be adequately photopolymerized (for at least 40 seconds, with photopolymerizing equipment with emissions close to 1,000 mW/cm2). After the finalization of the restoration, the absolute isolation must be removed, the occlusion must be checked and the finishing must be carried out. Then the restoration can be polished.