25/09/2024

5 types of composites resins for your dental procedure

In restorative dentistry, resin composites – or simply resins (or composite resins) – have been the most versatile materials since their commercial launch in the early 1970s.

Together with bonding techniques, these materials revolutionised restorative concepts and techniques, in which aesthetics and preservation of healthy tooth structure have gained progressive prominence until they are considered key points today, when restorative bases prioritise minimal invasion relevant to the case, adhesion as the key to marginal integrity, retention and stability of the restoration and aesthetics through the optical effects of the resins.

Among the noted developments, we highlight significant improvements in mechanical properties, wear resistance, gloss and polish, reduction of polymerization shrinkage, reduction of fluid and mass sorption with different degrees of opacity, as well as resins that, with a degree of chemical sophistication – such as Bulk Fill and unichromatic resins – offer solutions with simple resolution and less clinical time within their indications.

We will continue to discuss objectively the five types of current resins and their peculiarities:

Conventional resins

They are resins of normal consistency, moldable and capable of being sculpted, indicated for anterior, posterior and indirect use (provided that an additional polymerization cycle is carried out).

They have different colors, according to the classic ceramic scale, and even different degrees of opacity, such as:

Opaque: used to opacify an undesirable substrate;
Dentins: of medium opacity, serve as dentin substitutes and promote the chromatic appearance of the restoration and masking of interfaces;
Chromatic Enamels: of low opacity (medium to high translucency), normally they should not be used in thicknesses much greater than 0.5 mm to avoid their translucency generating a greyish color of the restoration (reduction of value/luminosity), even when the correct color has been selected;
Translucent or Achromatic Enamels: high translucency materials, for when it is necessary to highlight opalescent aspects on the incisal edges;
Value Resins: materials that increase value without offering opacity. They are used in complex stratifications;
Body Resins: intermediate opacity resins for simple cases and without the need for great optical effects.

These materials should generally be used in thicknesses of up to 2 mm (depth of polymerization), and each increment should be photoactivated on average for a period between 20 and 40 seconds, depending on the color, opacity and type of photoactivating device.

Regarding restorative techniques or strategies, we have:

Single or Body stratification: in which only one Body mass (medium opacity is used) requires a maximum thickness of 1.5 mm in anterior teeth (otherwise the restoration will be greyish due to the lack of opacity of the material) and in substrates of favourable colour. The aesthetic result is normally satisfactory in small and medium cavities, since the use of a single mass of medium opacity limits the optical effects of the material. Using the incremental technique can be a good option for posterior teeth;
Double stratification: when we normally use the association of Enamel and Dentin masses, whose interaction of masses of different degrees of opacity/translucency can more faithfully reproduce the optical effects of the double layer of dentin and dental enamel. In the case of composites resins, it is important that the enamel thickness remains between 0.5 mm and, at most, 0.7 mm (depending on its degree of translucency), so that excessive translucency reduces the luminosity of the restoration, leaving it slightly greyish. The most commonly used and versatile technique for both anterior and posterior teeth;
Complex stratification: a technique used in large anterior reconstructions or even in some simpler ones, but with cases that present notable evidence of mamelons, incisal translucency and incisal opalescence. Or, even when there is an unfavorable substrate that needs to be neutralized or a large absence of wall (extensive class IV), conditions that require the use of an opaque effect composites resin to be then covered by a mass of dentin in the restorative process. To be successful in this technique, it is necessary to have a deep knowledge of the passage of light through the different composites resin masses and the optical effects that each of them offers.

FGM Conventional Composites Resins: Vittra APS and Opallis

Flow Resins

Resins with a more fluid consistency and injected into cavities without the sculptable appearance of conventional resins. These are materials that have evolved and currently have two subcategories:

Conventional Flow resins: they emerged in the mid-1990s. They have a low filler level (35% to 50%), low mechanical properties, high shrinkage and polymerization stress. They are indicated for linings up to 2 mm thick and microcavities without occlusal stress;

• High-filler Flow resins: they are the evolution of conventional Flow resins, having a filler level in the range of 70% and, therefore, better properties. They have the same indications as conventional Flow resins and indications in some injectable techniques.

Flow FGM Resins: Opus Bulk Fill Flow APS and Opallis Flow

There are opaque Flow resins for use in small thicknesses that can be used occasionally as an alternative to conventional opaque resins. With the increase in interest and evolution of the category, so-called “injectable” resins have emerged, which are Flow resins with a high percentage of filler with a consistency that is a little less fluid and more thixotropic (intermediate thixotropy), between conventional and Flow resins, possessing physical properties closer to conventional resins.

Resinas Bulk Fill

These are resins that were developed with a greater polymerization depth (4 to 5 mm) and lower polymerization tension and contraction, facilitating and speeding up the restoration of posterior teeth with greater increments.

On the other hand, they are a little more translucent than Body resins and can, in some cases, generate a slight graying of the restoration, which is not normally critical in posterior teeth.

In cases of darkened or pigmented substrates, a thin layer of opacifying resin can be used.

Bulk Fill resins are available in two consistencies:

Bulk Fill Flow: resins for dentin bases or substitutes, ideal for filling areas that are difficult to compact, such as proximal boxes, undercut cusps and internal angles;
Restorative Bulk Fill: resins that support occlusal loads. They can be used alone in posterior restorations or associated with Bulk Flow resins.

Among the Bulk Fill techniques, we can highlight:

Bulk & Body: technique in which we use a Bulk Flow base and cover the occlusal portion with a conventional Body or Enamel/Dentin resin. Indicated to obtain the time and convenience gains of Bulk Fill and the aesthetics of conventional resins, generally in larger posterior cavities with greater visibility;
Restorative Bulk Fill: technique in which we fill with increments of up to 4 to 5 mm in depth and sculpt the restoration, removing the excess. Indicated for simple cavities, such as Class I, since the perfect filling of proximal boxes with this technique is challenging;
Bulk & Bulk: when we associate a Bulk Fill Flow base and place a layer of restorative Bulk Fill resin on top. This technique can be used in all cases, especially in Class II cavities, ensuring the best filling without failures in difficult-to-access areas. It presents a considerable time gain even compared to the Bulk & Body technique.

Bulk Fill FGM Resins: Opus Bulk Fill APS and Opus Bulk Fill Flow APS

Unichromatic resins

These are resins with a special characteristic of chromatic reflection of the surrounding cavity walls. This means that with a universal syringe in terms of colour (unichromatic), all the scales are reproduced – a true chameleon effect.

This makes the colour selection stage unnecessary. For best results, we need good substrates (in terms of colour) or that these, in case of pigmentation, are neutralised by the previous application of opaque and a dentin. These materials make life much easier for the clinician and, by matching the colour of the teeth, they would continue to have a good colour similarity even when teeth restored with these materials are bleached.

Conventional unichromatic resins are indicated in incremental techniques for posterior and anterior teeth (small and medium cavities), thin veneers on good substrates or as body enamel on chromatic dentin (double stratification).

For best translucent adhesive results without yellowing effect, Ambar APS and Ambar APS Universal adhesives should be used together with this material, to further enhance the chameleon effect.

FGM Unichromatic Resin: Vittra APS Unique

Bisacrylic Composite Resins

They are intermediate materials – in properties and aesthetics – between acrylic resins and resinous composites, available in injectable consistency, in self-mixing systems of the base with catalyst. That is, normally by chemical polymerization.

FGM bisacrylic composite resin: Primmaart

Its main indications are as provisional restorations of partial or fixed unitary prostheses and laminated veneers or as a mock-up (simulation of the final result) for veneers and occlusal changes/reconstructions.