low shrink posterior restorative ls system adhesive

Technical Product Profile

Filtek™ LSLow Shrink Posterior Restorative

LS System AdhesiveSelf-Etch Primer & Bond

Table of ContentsIntroductIon ............................................................................................................... 1

History ............................................................................................................................. 1

Rationale ......................................................................................................................... 3

overvIew of MaterIals ........................................................................................... 4

Filtek™ LS Low Shrink Posterior Restorative ................................................................ 4Chemistry of Resin System ........................................................................................ 4Ring-Opening Polymerization.................................................................................... 5Initiator System .......................................................................................................... 6Filler Technology ....................................................................................................... 6

LS System Adhesive Self-Etch Primer and Bond ............................................................ 7Chemical Background ................................................................................................ 7LS System Adhesive Self-Etch Primer ...................................................................... 8LS System Adhesive Bond ......................................................................................... 9

test results ............................................................................................................... 10

Polymerization Shrinkage ............................................................................................. 10

Polymerization Stress .................................................................................................... 12

Cusp Displacement ....................................................................................................... 15

Adhesion ........................................................................................................................ 16

Marginal Quality of the Restoration ............................................................................. 17

Wear .............................................................................................................................. 18

Flexural Fatigue Limit .................................................................................................. 18

Compressive Strength and Flexural Strength ............................................................... 19

Flexural Modulus .......................................................................................................... 19

Fracture Toughness (KIC) ............................................................................................. 20

Depth of Cure ................................................................................................................ 20

Ambient Light Stability ................................................................................................. 21

Water Sorption and Exogenic Staining ......................................................................... 22

Clinical Studies ............................................................................................................ 22

3M esPe aPPlIcatIon test .................................................................................... 23

clInIcal case ............................................................................................................ 24

Clinical Application of the Filtek™ LS System ............................................................. 24

technIque GuIde ...................................................................................................... 26

Filtek™ LS Low Shrink Posterior Restorative .............................................................. 26

LS System Adhesive Self-Etch Primer and Bond .......................................................... 26

IndIcatIons ............................................................................................... 27

shades ........................................................................................................................... 27

coMPosItIon ............................................................................................................... 27

questIons and answers ...................................................................................... 28

suMMary ....................................................................................................................... 33

lIterature.................................................................................................................... 34

technIcal data .......................................................................................................... 36

table of contents

IntroductionFiltek™ LS Low Shrink Posterior Restorative and LS System Adhesive Self-Etch Primer and Bond is a complete system for Class I and II direct posterior restorations.

Filtek LS restorative is offered in 4 radiopaque shades (A2, A3, B2, C2) with one opacity. This restorative is based on a new resin chemistry – silorane technology – which has achieved the lowest shrinkage currently available. The reduced shrinkage leads to greatly reduced polymerization stress.

Filtek LS Posterior Restorative is used with LS System Adhesive. The dedicated adhesive is an advanced self-etching formulation delivered in vials. The formulation of LS System Adhesive specifically fits the chemistry of the Filtek LS restorative.

The specially-adapted LS adhesive and the reduced shrinkage of the Filtek LS composite lead

to restorations with excellent marginal integrity.

HistoryComposite materials have been used in dental practices to restore teeth since 3M first introduced a composite to the dental market in 1964. Composites consist of fillers embedded in a chemically-reactive organic resin matrix. Fillers are typically inorganic materials like glass or quartz which are generally functionalized on the surface (silanization), enabling chemical linkage to the resin matrix.

The early materials were chemically-cured, two-component systems. These tooth-colored materials provided better esthetics than amalgam. However, much had to be learned about the chemical and physical properties that were required to withstand the aggressive oral environment. High shrinkage, high wear, color changes and lack of bonding to tooth surfaces

were the issues associated with these early materials.

Significant improvements have been made since then (Table 1). On the one hand, adhesive systems have been developed that adhere well not only to enamel, but even to moist dentin. On the other hand, composites have been made stronger, with higher wear resistance and color stability. And, both composites and adhesives have been modified to be curable on demand by exposure to light.

1

1901 Synthesis and polymerization of methyl methacrylate

1930 Use of PMMA as denture base resin (Germany)

1944 First acrylic filling material

1951 Addition of inorganic fillers (non-bonded) to direct filling materials (Knock and Glenn)

1955 Investigation of epoxy resins as direct filling materials

1955 Acid-etch technique introduced (Buonocore)

1958 Dimethacrylates (Bis-GMA) and silanized inorganic filler investigated as direct filling material (Bowen)

1964 Bis-GMA composites marketed

1968 Development of polymeric coatings on fillers (Dental Fillings Ltd)

1973 UV-cured dimethacrylate composite resins

1977 Visible light-cured dimethacrylate composite resins

2007 Introduction of Filtek™ LS System to the market

IntroductIon

Table 1: History of major developments in composite resins (From 1901 – 2007)

Improvements on the composite side were achieved, to a great extent, by optimizing the fillers – while the chemistry behind the organic resin matrix remained essentially the same since the pioneering work of R. L. Bowen in the 1960s. Practically all composites employ dimethacrylates such as TEGDMA, Bis-GMA or UDMA, which are radically polymerized as the primary resin (Fig. 1).

It is striking, that during these decades of improvement, polymerization shrinkage was only incrementally reduced to a somewhat lower level. Reducing the polymerization shrinkage of composite materials without compromising physical and handling properties remained the major challenge for material scientists.

Shrinkage is one of the major drawbacks of composite materials. Shrinkage results in a built-in polymerization stress which challenges the tooth/composite interface. To achieve long-term marginal integrity of restorations, technically-perfect bonding to enamel and dentin with high bond strength is necessary to counteract the shrinkage and polymerization stress.

Polymerization shrinkage is an intrinsic property of the resin matrix. Upon curing, the single resin molecules move towards each other and are linked by chemical bonds to form a polymer network. This reaction leads to a significant volume contraction.

To date, the main strategy to reduce shrinkage focused on increasing the filler load, thereby reducing the proportion of the methacrylate resin (Fig. 2). Since the shrinkage is caused by the resin, the lower the proportion of resin in a composite, the lower the shrinkage will be. However, the shrinkage intrinsic to the methacrylate resin has remained a major challenge. Therefore, exchanging the resin seems the most promising pathway to solve the shrinkage problem.

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SiloraneMethacrylate

60 65 70 75 80 85 90 95 100

Figure 2: Simulated dependency of the volumetric shrinkage of composites on the filler content in weight percent plotted for typical methacrylate-based resins and the silorane resin

Source: 3M ESPE internal data

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IntroductIon

Figure 1: Methacrylate resin chemistry

It’s time to face the next challenge: the fundamental improvement of the resin matrix by advancing beyond the current methacrylate resin systems.

Filtek™ LS Low Shrink Posterior Restorative resin is based on silorane chemistry and does not contain methacrylates. The silorane ring-opening monomers provide for low polymerization shrinkage.

The new silorane platform provides a fundamental solution to the long-standing customer need for low shrinkage.

RationalePolymerization shrinkage and the resulting shrinkage stress, lead to microleakage which is among the major factors for composite material failures in the oral environment. Moreover, shrinkage stress can lead to tooth deformation, enamel cracks and stress-induced post-operative sensitivity (Fig. 3).

Materials which remain dimensionally stable upon polymerization, coupled with an advanced bonding to the enamel and dentin, will markedly enhance the stability of the restoration under functional stress.

Filtek LS Low Shrink Posterior Restorative is designed to minimize shrinkage and polymerization stress.

3

Figure 3: Clinical challenges associated with high shrinkage and polymerization stress

IntroductIon

Filler 76%

Initiator 0.9%Stabilizer 0.13%

Pigments 0.005%

Siloraneresin 23%

Figure 5: Composition of Filtek™ LS Low Shrink Posterior Restorative

4

Overview of MaterialsFiltek™ LS Low Shrink Posterior RestorativeChemistry of the Resin System The development of dental restorative composites began in the late 1940s. Since then many technological developments have significantly improved the clinical performance of dental resin composites. However, the common chemical basis for all restorative composites remained the radical polymerization of methacrylates or acrylates. The low-shrinking Filtek LS restorative is based on the new ring-opening silorane chemistry.

Siloranes are a totally new class of compounds for the use in dentistry. The name silorane derives from its chemical building blocks siloxanes and oxiranes (Fig. 4).

Siloxanes are well known in industrial applications for their distinct hydrophobicity. By incorporating the siloxanes into the dental silorane resin, this property was transferred to the Filtek LS composite.

Oxiranes have been used for a very long time in many technical fields, especially where high forces and a challenging physical environment are expected, such as in the manufacture of sports equipment like tennis rackets or skis, or in the automotive and aviation industries and many more. The oxirane polymers are known for their low shrinkage and the outstanding stability toward many physical and chemophysical forces and influences.

The combination of the two chemical building blocks of siloxanes and oxiranes provides the biocompatible, hydrophobic and low-shrinking silorane base of Filtek LS Low Shrink Posterior Restorative. This innovative resin matrix represents the major difference of Filtek LS restorative compared to conventional methacrylates. Also, the initiating system and the filler were adapted in order to provide the best performance of the new technology (Fig. 5).

overvIew of MaterIals

Figure 4: Silorane chemistry

Ring-Opening Polymerization The polymerization process of Filtek LS restorative occurs via a cationic ring-opening reaction which results in a lower polymerization contraction, compared to the methacrylate-based resins which polymerize via a radical addition reaction of their double bonds.

The ring-opening step in the polymerization of the silorane resin significantly reduces the amount of polymerization shrinkage which occurs in the curing process. The reduced amount of shrinkage is illustrated schematically in Fig. 6. During the polymerization process, molecules have to approach their “neighbors” to form chemical bonds. This process results in a loss of volume, namely polymerization shrinkage. In contrast to the linear-reactive groups of methacrylates, the ring-opening chemistry of the siloranes starts with the cleavage and opening of the ring systems. This process gains space and counteracts the loss of volume which occurs in the subsequent step, when the chemical bonds are formed. In total, the ring-opening polymerization process yields a reduced volumetric shrinkage.

Besides shrinkage, another parameter of paramount importance to the performance of a restorative material is polymerization stress. Polymerization stress is generated when composites are cured in the bonded state and the polymerization shrinkage develops forces within the cavity walls. The rigid tooth structure will withstand this force to a certain degree, however, these tensions can lead to marginal gaps or to damage of healthy tooth structure by its deformation. These forces or tensions are summarized under the term “polymerization stress.”

From the restorative material perspective, polymerization stress is mainly determined by three factors: 1) the polymerization shrinkage, 2) the internal flowability of the material, and 3) the polymerization kinetics (polymerization speed). A highly-shrinking material with a small, internal flowability and very fast curing speed in the first few seconds, will exhibit the highest polymerization stress.

Silorane technology was developed to minimize shrinkage, and is thus also predestined for low stress development. Moreover, the kinetics of the initiation and polymerization of the Filtek LS resin were optimized to provide very low polymerization stress, as will be shown in the Test Result chapter.

5


Figure 6: Reactive sites of silorane and methacrylates and corresponding shrinkage reduction upon polymerization

1 <1% volumetric shrinkage tested by bonded disc method

Initiator System One component of the initiating system is camphorquinone, which matches the light spectrum of conventional dental polymerization light sources. 3M™ ESPE™ Filtek™ LS Low Shrink Posterior Restorative can be cured with halogen, as well as LED devices.

Further components of the initiating system are iodonium salts and electron donors, which generate the reactive cationic species that start the ring-opening polymerization process (Fig. 7).

The initiating system of Filtek LS restorative was tailored so that the resulting polymerization kinetics leads to a minimized polymerization stress. A unique property of the three-component initiating system is that a “critical mass” of initiating reactive cationic species has to be generated to start the polymerization. This threshold behavior brings one major advantage: it allows the practitioner to work longer under full operatory light than with any conventional methacrylate-based composite.

While developing low stress and being stable against ambient light, the curing times for 2.5 mm increments of Filtek LS restorative could be kept at a level comparable to conventional composites:

Halogen light devices Exposure time

Wave length spectrum 400-500 nm Output 500–1400 mW/cm2,

40 sec, standard mode

LED light devices Exposure time

Wave length spectrum 430-480 nm Output 500-1000 mW/cm2, 40 sec, standard mode Output 1000-1500 mW/cm2, 20 sec, standard mode (e.g., Elipar™ FreeLight 2, manufactured by 3M ESPE)

However, the threshold behavior of the Filtek LS restorative initiator system requires a minimum curing time of 20 seconds, which can not be compensated by higher intensities. Very high intensity light sources like plasma arc lamps and lasers do not allow sufficiently-long curing times due to heating of the tooth. Therefore, plasma arc lamps, lasers and other light sources with very high intensities are contraindicated to be used with Filtek LS restorative.

Filler Technology Filtek LS restorative is filled with a combination of fine quartz particles and radiopaque yttrium fluoride. From the filler side, Filtek LS restorative is to be classified as a microhybrid composite. The quartz surface is modified with a silane layer which was specifically matched to the silorane technology in order to provide the proper interface of the filler to the resin for long-term, excellent mechanical properties (Fig. 8).

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Figure 7: Initiation chemistry for silorane

Figure 8: Filler-size distribution of Filtek™ LS Low Shrink Posterior Restorative


LS System Adhesive Chemical Background Recently, self-etch adhesives have gained increasing popularity among dentists. Their success is mainly based on their ease of use, low technique sensitivity and ability to reduce post-operative sensitivity as compared to total-etch adhesives.

LS System Adhesive Self-Etch Primer and Bond is a new member of the 3M ESPE family of successful self-etch adhesive materials. LS System Adhesive has been specially designed to provide strong and long-lasting bonding of Filtek LS Low Shrink Posterior Restorative to enamel and dentin, providing the basis for excellent marginal integrity of the restorations.

The extraordinary low shrinkage and polymerization stress of Filtek LS restorative have been achieved by developing the new silorane resin system. Curing of this resin system involves chemical mechanisms different from conventional methacrylate-based composites. From a scientific standpoint, it is obvious that a new adhesive is needed. Adhesives currently available on the market have been developed for traditional methacrylate materials and will, therefore, lead to insufficient results in combination with Filtek LS restorative.

Due to its siloxane backbone, the silorane resin is more hydrophobic than conventional methacrylate resins, so it results in reduced water uptake and related phenomena, as described in the Test Results section. That means this adhesive has to bridge a larger difference between the hydrophilic tooth substrate and the hydrophobic silorane material as compared to conventional methacrylate materials. Therefore, LS System Adhesive has been designed as a two-step adhesive (Fig. 9):

• LSSystemAdhesiveSelf-EtchPrimer is rather hydrophilic, and ensures strong and durable adhesion to the tooth.

• LSSystemAdhesiveBond is optimized for wetting and adhering to the hydrophobic Filtek LS Posterior Restorative.

LSSystem Adhesive

Primer

LSSystem Adhesive

Bond

HydrophobicHydrophilic

Tooth Filtek™ LS

Figure 9: Different regimes of hydrophilicity/ hydrophobicity at the interface between the tooth and Filtek™ LS Low Shrink Posterior Restorative

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LS System Adhesive Self-Etch Primer In principle, self-adhesion is generated by acidic monomers that etch dental substrates and thus create a retention pattern for micromechanical interlocking of the cured adhesive with the tooth. Furthermore, they provide chemical bonding to the calcium-containing hydroxyapatite of the mineralized tissue. Most of today’s self-etch adhesives contain phosphorylated methacrylates as acidic monomers; some contain carboxylic acid functionalized monomers, or a combination of both.

LS System Adhesive Self-Etch Primer contains phosphorylated methacrylates, as well as the Vitrebond™ copolymer with its carboxylic acid functionality used in many 3M™ ESPE™ resin-modified glass ionomers, and adhesives for adhesion to enamel and dentin. Furthermore, comonomers like BisGMA and HEMA, a solvent system consisting of water and ethanol for wetting and penetrating the dental substrates, and a photoinitiator system based on camphorquinone for thorough and fast curing are included. A silane-treated silica filler with a primary particle size of about 7 nm has been added for improving the mechanical strength and film-forming properties of LS System Adhesive Self-Etch Primer. This filler is very finely dispersed in order to prevent settling.

Special attention has been devoted to providing a stable formulation that combines acidic monomers and the water/ethanol solvent system. Refrigeration is required in order to prevent loss of ethanol or water by evaporation.

With a pH of about 2.7, LS System Adhesive Self-Etch Primer provides rather mild etching and demineralization of the tooth structure, yet strong and durable bonding through its nanoetching pattern, as well as chemical bonding to the hydroxyapatite. If LS System Adhesive is to be applied to uncut enamel, a separate etching of the unprepared tooth structure is recommended. It is not required to etch prepared enamel but it may be done if desirable.

On dentin, well-defined resin tags are visible and penetration of the dentin structure by LS System Adhesive Self-Etch Primer (Fig. 10).

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Figure 10: SEM micrograph of the composite/adhesive/ dentin interface after consecutive etching with hydrochloric acid and sodium hypochlorite solution


LS System Adhesive Bond LS System Adhesive Bond is also based on methacrylate chemistry. As a main component, it contains a unique 3M™ ESPE™ hydrophobic bifunctional monomer in order to match the hydrophobic silorane resin. An immediate result of this feature is the easy adaptation of Filtek™ LS Low Shrink Posterior Restorative on cured LS System Adhesive Bond. Other components include acidic monomers that initiate the ring-opening cationic cure of Filtek LS restorative, thus providing chemical bonding to Filtek LS (Fig. 11). The photoinitiator system is based on camphorquinone.

Figure 11: Mechanism of chemical bonding between LS System Adhesive Bond and Filtek™ LS Low Shrink Posterior Restorative

Acidic Monomerof LS System

Adhesive Bond

Curingof Adhesive Application

and Curingof Filtek™ LSRestorative

Chemical BondBetween Adhesive

and Composite

OxiraneGroup

LS System Adhesive Bond contains a silane-treated silica filler that not only improves the mechanical strength of the material, but also allows for carefully adjusted viscosity properties. LS System Adhesive Bond may appear very viscous at first glance – you may have to flick it to the tip of the vial in order to dispense it. However, once you apply it with the brush or air-thin it, the viscosity drops by several orders of magnitude (Fig. 12), and it can be very easily dispersed as an even, uniform film. This phenomenon is called shear thinning. The benefits are obvious: it does not drop from the brush; and you can direct it with the air stream where you want it to be and it stays there – especially on the cavity walls and preparation margins – and it does not pool. With LS System Adhesive Bond, the resulting film thickness is in the range of other two-step self-etch adhesives, despite the apparently higher viscosity.

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Figure 12: Viscosity of LS System Adhesive Bond at low shear and under application conditions. Application and air thinning reduces the viscosity by several orders of magnitude, thus allowing for formation of an even and homogeneous film


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Test ResultsFiltek™ LS Low Shrink Posterior Restorative has been tested extensively, both in-house as well as at renowned universities worldwide – and many results have been published in peer-reviewed journals. In this evaluation care was taken to address the most important quality parameters for composite restorations.

Polymerization ShrinkagePolymerization shrinkage is still a major concern. Prof. Swift and co-workers stated only recently that “although composites are now the material of choice for most restorations, their polymerization shrinkage remains a problem. The contraction stress associated with this shrinkage can cause debonding at the composite/tooth interface and can contribute to post-operative sensitivities, enamel fracture, recurrent caries marginal staining and eventually failure of the restoration.” (Yamazaki, Bedran, Russo, Pereira and Swift, 2006)

Filtek LS restorative has been developed to minimize polymerization shrinkage and polymerization stress, while providing a high-performance bond to the tooth. Extensive testing of polymerization shrinkage has been conducted which shows Filtek LS restorative to have a significantly lower shrinkage than all methacrylate composites tested, irrespective of the method employed (Fig. 13, Fig. 14, Fig. 15).

Most common measurements for polymerization shrinkage are the bonded-disc method, also referred to as Watts method (Watts & Cash 1991), and the Archimedes method which was recently developed into a German Standard (DIN 13907/2005). The bonded-disc method results in lower shrinkage values since only the linear shrinkage of a bonded composite disc is measured and then converted into % of volume. Whereas the Archimedes method measures the actual shrinkage in volume according to the buoyant force principle. However, both methods show a high correlation (Weinmann et al., 2005).

The bonded-disc method revealed shrinkage values for Filtek LS restorative of 0.9 % (Fig. 13), while the polymerization shrinkage is about 1% when measured with the Archimedes method (Fig. 14).

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Figure 13: Polymerization shrinkage (bonded-disc method) of Filtek™ LS Low Shrink Posterior Restorative and methacrylate composites


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test results

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Figure 14: Polymerization shrinkage (Archimedes method) of Filtek™ LS Low Shrink Posterior Restorative and methacrylate composites


A third method to determine volumetric shrinkage is employing video imaging to determine dimensional changes. The so-called AccuVol method (J. Burgess, U.S.A.) results in a value of 0.66 % volumetric shrinkage for Filtek LS (Fig. 15) and confirms Filtek LS restorative to be the lowest shrinking material among all composites tested.

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Figure 15: Polymerization shrinkage (AccuVol method) of Filtek™ LS Low Shrink Posterior Restorative and methacrylate composite

Source: J. Burgess, U.S.A.

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test results

Polymerization StressPolymerization stress builds up during polymerization as a consequence of polymerization shrinkage when the gel point is reached, and further contraction cannot be compensated for by additional flow of the material.

Filtek™ LS Low Shrink Posterior Restorative develops a very low polymerization stress compared to methacrylate composites, with all methods employed (Fig. 16, Fig. 17, Fig. 18).

A wide range of shrinkage-stress data are available for a tensilometer method developed at ACTA (University of Amsterdam). Here a composite sample is luted between a glass and a metal plate. The metal plate is attached to a load cell. While the composite is cured through the glass plate, the height of the composite sample is held constant by the testing device. The force needed to keep the height constant is recorded.

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Filtek™ LSTetric® CeramSpectrum® TPH® QuiXX™ Filtek™ Z250 Filtek™ Supreme

Figure 16: Polymerization stress (Tensilometer method) of Filtek™ LS Low Shrink Posterior Restorative compared to several methacrylate composites

Source: Dr. DeGee and Prof. Feilzer, University of Amsterdam (ACTA)

Watts et al. (2003) developed a method to determine the photopolymerization shrinkage-stress kinetics in resin composites with the Bioman device. Filtek LS restorative shows significantly lower polymerization stress than the methacrylate composites tested (Fig. 17).

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Figure 17: Polymerization stress (Bioman method) of Filtek™ LS Low Shrink Posterior Restorative and methacrylate composites

Source: Prof. Watts, University of Manchester

test results

Another method for the evaluation of shrinkage stress was performed by Prof. Ernst (University of Mainz) by means of a photoelastic investigation. Composite specimens were bonded in Araldit plates and cured with a halogen curing light. The strain forces induced by the polymerization shrinkage of the composites into the Araldit plate can be visualized as isochromatic rings in a polarizing microscope. The polymerization stress was calculated from the diameter of the first order isochromatic rings, at 4 minutes and again at 24 hours after exposure.

The results reveal that Filtek LS restorative generated the lowest polymerization stress among all composites tested (Fig. 18). Additionally, all methacrylate-based materials continued to build up stress: the values measured after 24 hours are always higher than after 5 minutes. Filtek LS restorative was the only material which maintained the same low-stress value observed after 5 minutes and did not continue to build up stress (Ernst et al. 2004).

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Figure 18: Polymerization stress determined by photoelastic investigations

Source: Prof. Ernst, University of Mainz

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test results

The correlation between polymerization shrinkage and polymerization stress can be seen in Fig. 20, which shows the unique position of Filtek LS restorative made possible through silorane technology.

The low stress development of Filtek™ LS Low Shrink Posterior Restorative can be visualized by Finite Element Analysis. Dr. Versluis (University of Minnesota) simulated the spatial distribution and the intensity of polymerization stress compared to a low-shrink methacrylate (Fig. 19). Note that the Filtek LS restoration shows an absence of “gray” high-stress areas where enamel cracks and leakage in the margin can occur.

Figure 19: Finite Element Analysis of Polymerization Stress

Source: Dr. Versluis, University of Minnesota

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test results

Figure 20: Correlation between polymerization shrinkage and polymerization stress of Filtek™ LS Low Shrink Posterior Restorative and methacrylate composites (Shrinkage method: Bonded disc method; Stress method: Bioman)

Source: Prof. Watts, University of Manchester

Cusp DisplacementA clinical implication of high polymerization stress and polymerization shrinkage is cusp displacement, which can result in the damage of healthy tooth structure (e.g., enamel cracks) and strain-induced hypersensitivities. Prof. Bouillaguet (University of Geneva) showed that Filtek LS Low Shrink Posterior Restorative generates a much lower cusp displacement compared to methacrylate-based composites (Bouillaguet et al. 2006, Fig. 21).

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Time (sec)0 50 100 150 200

Filtek™ LSTetric® FlowPremise™ Tetric® Ceram QuiXX™

8

Figure 21: Time resolved cusp displacement of teeth with Filtek™ LS and methacrylate composites placed in Class II MOD cavities. [Electronic speckle pattern interferometry (ESPI)]

Source: Prof. Bouillaguet, University of Geneva

15

test results

Figure 22: Tensile bond strength of the Filtek™ LS System and methacrylate systems

Source: Prof. Powers, University of Michigan

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Figure 23: Shear bond strength of the Filtek™ LS System and methacrylate systems


Prof. Fischer (University of Zurich) investigated the durability of the adhesive interface by thermocycling and subsequent determination of shear bond strength. Filtek LS System showed a significantly higher bond strength after thermocycling compared to a leading methacrylate system (Fig. 24).

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Filtek Silorane/Silorane Adhesive

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35

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ond

Str

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TC

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Tetric EvoCeram®/AdheSE®

Filtek™ LS/LS Adhesive

Dentin Enamel Dentin Enamel

Figure 24: Bond strength after thermocycling of Filtek™ LS System as compared to a leading methacrylate system

Source: Prof. Fischer, University of Zurich

16

AdhesionAdhesion with sufficient high-bond strength is a key factor determining the seal of a filling and the stabilization of the restored tooth. To ensure optimal linkage of Filtek™ LS Low Shrink Posterior Restorative to the tooth, a dedicated LS System Adhesive has been developed.

Bond strength of the LS System Adhesive in combination with Filtek LS restorative was evaluated with the widely-used tensile bond test where load is applied perpendicular to the tooth surface, and shear bond testing where load is applied parallel to the tooth surface. Prof. Powers (University of Michigan) determined tensile bond strengths to enamel and dentin for the Filtek LS System to be higher than a variety of clinically successful bonding systems (Fig. 22).

Similarly, shear bond strength of LS System Adhesive revealed bond strength values similar to or better than current adhesive systems (Fig. 23).

test results

17

Marginal Quality of the Restoration Due to the low shrinkage and low polymerization stress of the Filtek LS Restorative System, a smaller portion of the bond strength has to be invested to counteract forces resulting from shrinkage. Thus, more effective bond strength remains to counteract mastication forces and forces resulting from temperature changes. The low polymerization shrinkage of Filtek LS restorative, in combination with the excellent bond strength, leads to excellent marginal integrity of the restoration (Fig. 25).

Filtek LS Restorations were challenged in a chewing-simulation test device which combined 450,000 cycles of loading with 50 N per load and thermocycling for 1,550 cycles between 5°C and 55°C. The results showed that Filtek LS System provides better marginal integrity before and after chewing simulation, as compared to leading methacrylate systems (Fig. 26).

100

80

60

40

20

0Tetric EvoCeram®/

AdheSE®

QuiXX™/Xeno® III

Filtek™ LS/LS SystemAdhesive

% C

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us M

arg

in (E

nam

el a

nd D

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BeforeChewing

AfterChewing

BeforeChewing

AfterChewing

BeforeChewing

AfterChewing

Figure 26: Marginal integrity of the Filtek™ LS System as compared to leading methacrylate systems


Conventional composite: adhesive and shrinkage forces work in strong opposition.

The Filtek™ LS System ensures marginal quality due to reduced shrinkage forces combined with excellent adhesive force values.

Polymerization stress

Bond strength

Polymerization stress

Bond strength

Figure 25: Bond strength and polymerization stress act in opposite directions

test results

WearThe wear rate of Filtek™ LS Low Shrink Posterior Restorative was determined in a three-body abrasion test according to the ACTA method. In this test, a sample wheel filled with composites (Body 1) is rotated against a structured stainless steel wheel (Body 2) in a millet suspension (Body 3). As the stainless steel wheel is narrower than the sample wheel, it leaves an abrasion mark on the samples, the depth of which can be determined by means of a profilometer. The deeper the abrasion mark, the less resistant the material is to wear. The three-body wear of Filtek LS restorative corresponds to that of the clinically-tried and proven composites (Fig. 27).

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Figure 27: Three-body wear for Filtek™ LS Low Shrink Posterior Restorative and methacrylate composite


18

Flexural Fatigue LimitRestoration fracture due to material fatigue is one of the main reasons for failure of direct restorations. To obtain insight into the fatigue behavior of the Filtek LS restorative its flexural fatigue limit was determined and compared with conventional methacrylate composites. In this test 10,000 cycles of 3-point loading were applied with the frequency of 2 Hz, which is the upper limit of chewing frequency, under wet conditions and a constant temperature of 35°C. Several tests were done for each material, increasing the stress compared to the previous test if a material did not fail, and decreasing the stress if the material broke under loading. This procedure is referred to as the staircase approach.

The flexural fatigue limit of Filtek LS restorative under wet conditions reaches top level, indicating a long-term durability of Filtek LS restorative under clinical conditions (Fig. 28).

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80

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CeramFiltek™ Z250 SureFil® Prodigy®

Condensable®Solitaire® 2 Filtek™ LS

She

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Figure 28: Flexural fatigue limit of Filtek™ LS Low Shrink Posterior Restorative and methacrylate composites

Source: Prof. Braem, University of Antwerp

test results

19

Compressive Strength and Flexural StrengthA high compressive strength and a high flexural strength of the restoration material protects from fractures and stabilizes the tooth at the same time, especially when used in posterior restorations. The compressive strength of Filtek LS restorative was determinded by increasing the load on specimens of 3x3x5 mm until fracture. Flexural strength was determined using the a three-point bending test. In this test the material is fixed at two points and stress is applied to a third point until fracture. During the test, compressive forces built up on the upper side and tensile forces at the lower side.

Both the compressive strength and flexural strength of Filtek LS restorative rank within the range of clinically proven composites and are substantially above the ISO 4049 limit of 80 MPa (flexural strength) (Fig. 29).

500

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Flexural Strength

Figure 29: Compressive strength and flexural strength of Filtek™ LS Low Shrink Posterior Restorative and methacrylate composites


Flexural ModulusThe flexural modulus defines the rigidity of a material and is determined on the basis of the same experimental set-up as flexural strength. There are no standard values indicating how high the flexural modulus of a restoration material should be. If the flexural modulus is too high, the material is more brittle and filling fractures are more likely. If the flexural modulus is too low, the tooth would not be provided with adequate stability. The flexural modulus of Filtek LS restorative ranks within the range of clinically-proven composites (Fig. 30).

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20000

15000

10000

5000

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Figure 30: Flexural modulus of Filtek™ LS Low Shrink Posterior Restorative and methacrylate composites


test results

20

Fracture Toughness (KIC)Fracture toughness is a measure of the resistance of a material to crack formation. A notch is sawed into rod-shaped test bodies, which are then pulled apart with increasing energy until the notch propagates as a crack and the specimen breaks. The fracture toughness of Filtek™ LS Low Shrink Posterior Restorative is in the range of clinically proven methacrylate composites (Fig. 31).

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Figure 31: Fracture toughness of Filtek™ LS Low Shrink Posterior Restorative and methacrylate composites

Source: Prof. Kunzelmann, University of Munich

Depth of CureThe depth of cure was determined by a scratch test in accordance with ISO 4049:1999. For the test, composite cylinders are light cured in a brass mold. After polymerization, the brass mold is removed and the non-polymerized soft composite is scraped off with a spatula. The height of the remaining composite cylinder is measured. On the basis of these measurements Filtek LS restorative may be placed in increments of up to 2.5 mm (Fig. 32).

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(mm

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Tetri

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Filte

k™ L

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Figure 32: Depth of cure in metal molds according to ISO 4049:1999

Source: Dr. Ilie, University of Munich

test results

21

Ambient Light StabilityAmbient light stability contributes to the convenience of handling of a composite material. The ambient light stability of Filtek LS restorative was evaluated according to ISO 4049, which requires stability of a composite to be at least 60 seconds at 8000 Lux illumination (Fig. 33).

The silorane technology of Filtek LS restorative offers the dentist up to 9 minutes to place and shape the restoration under operatory light illumination.

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Figure 33: Ambient light stability of Filtek™ LS Low Shrink Posterior Restorative and methacrylate composite at 8000 Lux (Method based on ISO 4049)


test results

22

Clinical StudiesProf. Ernst, Johannes Gutenberg University of Mainz, Germany

Filtek LS restorative is being studied in Class II restorations with an experimental adhesive, together with QuiXfil posterior restorative and Xeno III adhesive, in a split-mouth design. 102 restorations were placed in 46 patients. At baseline and at one year, the restorations were evaluated according to the Ryge/CDA criteria. After one year, all restorations showed clinically excellent and acceptable results. No Charlie or Delta scores were documented (Schattenberg et al. 2007).

Prof. Eliasson, University of Iceland

In this study the clinical performance of Filtek LS restorative is being tested with an experimental adhesive system, and is compared to Tetric Ceram and a self-etching adhesive, AdheSE. At least one pair of restorations was placed in each patient according to research protocol. At one year, 53 restoration pairs in 31 patients were examined using the modified Ryge/CDA scale. No Charlie and Delta scores were seen. Color match was unchanged. One Tetric Ceram restoration was removed because of sensitivity. At one year, both materials appeared to be clinically acceptable and comparable.

Water Sorption and Exogenic StainingThe water sorption of composite restorations leads to swelling and possibly reduction in material properties – and it also facilitates exogenic discoloration. Filtek™ LS Low Shrink Posterior Restorative was compared to methacrylate systems regarding water uptake according to ISO 4049 and its tendency to acquire staining in a coffee-stain test. In the course of this test specimens are immersed in a coffee solution over extended periods of time and the resulting discoloration is expressed as a Delta E-value (Fig. 34).

Water sorption for Filtek LS restorative is very low due to the hydrophobicity of the silorane matrix, which results in a very low tendency for exogenic staining.

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5

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2

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0

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Water uptake (µg/mm3) ISO 4049

Filtek™ LS

CeramX™

Venus™

Grandio®

Premise™

TetricEvoCeram® Estelite®

Sigma

1510 20

Figure 34: Water uptake (ISO 4049) and exogenic staining (coffee-stain test) Delta-E values of Filtek™ LS Low Shrink Posterior Restorative and methacrylate composites


test results

23

3M ESPE Application TestTo evaluate the handling of the Filtek LS system, an in-vivo application test with 43 general practitioners in five European countries was conducted.

Dentists were asked to rate several handling criteria of the Filtek™ LS Low Shrink Posterior Restorative. On a 5-point scale, rating 1 stands for an excellent performance and rating 5 for a poor performance (Fig. 35).

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Excellent

Poor

With over 1,100 fillings placed during the 6-week trial period, this application test confirmed the convenient handling of Filtek LS restorative.

In a second in vivo application test, 1,145 fillings were placed by 43 general practitioners in Germany. No cases of post-operative sensitivity were reported. 86% stated they were satisfied with the overall handling of the Filtek LS System, and 84% found the system easy to use.

3M esPe aPPlIcatIon test

Figure 35: General practitioners rate the handling characteristics of Filtek™ LS Low Shrink Posterior Restorative


24

Clinical Case

Clinical Application of Filtek™ LS SystemThe direct restorative filling with the Filtek LS System requires no special technique. It works just like state-of-the-art composite/adhesive systems with one substantial improvement. Due to its greatly reduced sensitivity to ambient light, Filtek™ LS Low Shrink Posterior Restorative can be placed, shaped and modeled under full operatory light illumination for as long as 9 minutes.

The case shown is typical: A Class II composite filling had to be replaced due to the occurrence of secondary caries after marginal gap formation.

Initial situation Shade selection Prepared cavity with rubber dam, wedge and matrix after removal of old filling and excavation of secondary caries.

Application of LS System Adhesive Self-Etch Primer

Application of LS System Adhesive Self-Etch Primer for 15 seconds with black microbrush, followed by gentle air dispersion and 10 seconds of light curing.

Application of LS System Adhesive Bond

Application of LS System Adhesive Bond with green microbrush, followed by gentle air dispersion and 10 seconds of light curing.

clInIcal case

25

Application of Filtek LS Low Shrink Posterior Restorative

Placement and shaping of Filtek™ LS Low Shrink Posterior Restorative under full operatory light conditions.

20 seconds light curing (Elipar™ FreeLight 2).

Finishing and Polishing (Sof-Lex™). Final Filtek™ LS Low Shrink Posterior Restorative filling after rehydration of the teeth.

clInIcal case

26

Technique GuideFiltek™ LS Low Shrink Posterior Restorative

LS System Adhesive Self-Etch Primer and Bond

technIque GuIde

Filtek™ Silorane Low Shrink Posterior Restorative Niedrig schrumpfendes Seitenzahn-Füllungsmaterial

Silorane System Adhesive Self-Etch Primer and Bond Selbstätzender Primer und Bond

Use only as a system!

1 2

3 4

5 6

7 8

9 10

3M ESPE Filtek Silorane

Made in U.S.A. by 3M ESPE Dental Products St. Paul, MN 55144-1000

EC REP 3M ESPE AG Dental Products D-82229 Seefeld – Germany

Silorane System Adhesive

Made in Germany by 3M ESPE AG Dental Products D-82229 Seefeld - Germany

3M, ESPE and Filtek are trademarks of 3M or 3M ESPE AG. © 3M 2007 All rights reserved. 44-0007-4505-7

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1 2

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5 6

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1 2

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10 11 127 8

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27

IndicationsFiltek™ LS Low Shrink Posterior Restorative, together with LS System Adhesive Self-Etch Primer and Bond, is a system for direct, posterior restorative filling. It can be used for the following posterior restorations:

•ClassI •ClassII

Filtek LS restorative and LS system adhesive may be used together with glass ionomer cements or resin-modified glass ionomer cements, as cavity liners or bases.

Composites and compomers (including flowable composites and compomers), which are bonded to the tooth substance using an adhesive, may not be used as a liner or base under a Filtek LS filling.

ShadesFiltek LS posterior restorative is offered in the shades A2, A3, B2 and C2. All shades are radiopaque.

CompositionFiltek LS Low Shrink Posterior Restorative:

•Siloraneresin • Initiatingsystem:camphorquinone,iodoniumsalt,electrondonor •Quartzfiller •Yttriumfluoride •Stabilizers •Pigments

LS System Adhesive Self-Etch Primer:

•Phosphorylatedmethacrylates •Vitrebond™ copolymer •BisGMA •HEMA •Water •Ethanol •Silane-treatedsilicafiller • Initiators •Stabilizers

LS System Adhesive Bond:

•Hydrophobicdimethacrylate •Phosphorylatedmethacrylates •TEGDMA •Silane-treatedsilicafiller • Initiators •Stabilizers

IndIcatIons, shades and coMPosItIon

28

Questions and Answers

• What is the difference between Filtek™ LS Low Shrink Posterior Restorative and conventional composites currently on the market?

Conventional composites utilize methacrylate resins. Filtek LS restorative is based on new silorane resin technology. Because of this new resin technology, a dedicated adhesive, 3M™ ESPE™ LS System Adhesive Self-Etch Primer and Bond is required. Together they are referred to as the Filtek™ LS System

• Has this “new” silorane chemistry been thoroughly tested?

Yes, the Filtek LS System has been thoroughly tested throughout the development process by dentists and academics world wide. Beyond tests needed to comply with regulatory requirements, numerous additional studies were completed. The data show that the Filtek LS System performs well in both in vitro and in vivo studies.

• For what indications can I use the Filtek LS System?

Filtek LS restorative and LS System Adhesive form a system for direct posterior filling procedures: Class I and II.

• Do I need any special moisture-control precautions when placing fillings with the Filtek LS System?

No. The same isolation techniques are used for the Filtek LS System as any other conventional composite/adhesive system. Rubber dam is recommended, but not mandatory.

• Do I need to prepare the cavity in a special way for Filtek LS System restorations?

No. Filtek LS restorative/LS System Adhesive has to follow the usual guidelines for adhesive restorations; i.e., minimal invasive treatment, no special undercuts and beveled margins as needed.

questIons and answers

29


• Why do I need a dedicated adhesive?

Conventional dental adhesives on the market today were developed for methacrylate-based filling materials. The Filtek LS System is based on a completely new resin system, so a new adhesive is needed to provide optimum system performance.

• Can I use Filtek LS restorative with other adhesives than LS System Adhesive?

No. The use of a different adhesive will lead to inadequate bond strength between the adhesive and the restorative. The longevity of the restoration may be jeopardized.

• Can the LS System adhesive be used with conventional methacrylate composites?

No. LS System Adhesive has been designed for the use with Filtek LS Low Shrink Posterior Restorative only. The use of LS System Adhesive with a conventional composite will lead to inadequate bond strength between the adhesive and the restorative. The longevity of the restoration may be jeopardized.

• Why did 3M ESPE make LS System Adhesive a 6th generation adhesive?

Self-etch adhesives are known for their reduced risk of post-op sensitivity compared to total-etch systems. A major goal of silorane technology is to reduce shrinkage and polymerization stress, which can lead to a reduction in the risk of post-operative sensitivity. Coupling a self-etch adhesive with this low-shrink restorative will maximize this benefit.

• What happens if I separately etch enamel and/or dentin before applying the LS System Adhesive?

On dentin and prepared enamel, the self-etching LS System Adhesive needs no additional etching step. However, a separate etch will not reduce the bond strength.

30

• Should I etch uncut enamel before bonding?

Yes. Due to the mild etching of 3M™ ESPE™ LS System Adhesive, it is recommended to use a phosphoric acid etch on uncut enamel prior to application of LS System Adhesive.

• Can I wet my instrument with LS System Adhesive for placing and modeling of Filtek™ LS Low Shrink Posterior Restorative?

No. Using an adhesive to lubricate an instrument for placing Filtek LS restorative is not recommended.

• Can I use the Filtek LS System in a “sandwich” technique with GIC/RMGIC as a base or liner?

Yes. Filtek LS restorative and LS System Adhesive may be used together with glass ionomer or resin-modified glass ionomer liners or bases that do not require a separate adhesive.

• Can I use Filtek LS restorative as a base filling and cover it with a methacrylate composite?

No. Filtek LS restorative should not be used as a base under a conventional composite. Filtek LS restorative requires use of LS System Adhesive dedicated adhesive system. LS System Adhesive is not compatible with conventional methacrylates.

• Can I use a flowable composite as a liner?

No. Flowable composites and compomers should not be used as liners under a Filtek LS System filling. These materials require use of a conventional dental adhesive. Traditional dental adhesives are not compatible with the Filtek LS Low Shrink Posterior Restorative. If a liner is desired, a GI or RMGI such as Vitrebond™ or Vitrebond™ Plus Light Cure Glass Ionomer Liner/Base is recommended.


31


• Can Filtek LS restorative fillings be repaired with a conventional methacrylate composite system?

Yes, conventional adhesives can be used to bond methacrylate composites to cured Filtek LS restorative. Of course, Filtek LS restorative can also be repaired using the Filtek LS System adhesive and restorative.

• Why does Filtek LS restorative contain a quartz filler?

The silorane resin is compatible with the surface chemistry of quartz. In addition, the refractive indices of quartz filler and the silorane resin match, which provides for a clinically acceptable opacity. Radiopacity is provided by the addition of yttrium fluoride.

• What is the particle size of the quartz filler?

The average particle size of the quartz is 0.47 µm with a particle size range of .04 to 1.7µm.

• Can I use a “bulk placement” technique with Filtek LS restorative? What is the depth of cure?

No. Filtek LS restorative has to be placed incrementally. Increment depth should be 2.5 mm or less.

• Do I need to dim the operatory light during placement of Filtek LS restorative?

No, Filtek LS restorative allows up to 9 minutes of working time under full operatory light conditions.

32

• Can I use high-power curing lights, such as plasma arc lamps or lasers, for curing Filtek™ LS Low Shrink Posterior Restorative?

No. In the case of silorane chemistry, both the light intensity and a minimum light exposure time are critical to polymerize the restorative. This minimum exposure time would cause too much heat generation when using a plasma arc or laser.

• What’s the difference between shrinkage and stress?

Shrinkage is the process of volumetric contraction upon curing of the composite. Stress is the force that the shrinking composite exerts on the surrounding tooth structure.

• If I carefully layer my methacrylate composite, don’t I compensate for the shrinkage?

The layering technique does compensate for shrinkage to a certain degree. However, even when applying a sophisticated layering technique, methacrylate composites will produce a significantly higher polymerization stress compared to the low-shrink and low-stress optimized Filtek™ LS Low Shrink Posterior Restorative System.


33

Summary

Managing polymerization shrinkage, especially in the posterior region, is one of the most pressing challenges that is still not fully addressed with state-of-the-art composite filling materials. Over the last ten years several attempts were made to gain a low-shrinking material, but today still the vast majority of composites on the market show volume shrinkage values in the range of 2-3%.

3M™ ESPE™ Filtek™ LS Low Shrink Posterior Restorative is part of a revolutionary new filling system that will herald a new era in restorative dentistry. In contrast to conventional, methacrylate-based composites, Filtek LS restorative is polymerized in a ring-opening polymerization reaction. Filtek LS restorative is characterized by the lowest polymerization shrinkage on the market. Featuring a polymerization shrinkage of less than 1% also contributed greatly in reduction of polymerization stress. Lower polymerization stresses potentially reduce the risk of post-operative sensitivity, cusp deflection and, therefore, enamel cracks.

Furthermore, low polymerization shrinkage and stress, in combination with excellent adhesive properties of the 3M™ ESPE™ LS System Adhesive Self-Etch Primer and Bond, result in an excellent marginal integrity of Filtek LS System restorations.

The LS System Adhesive is a dedicated adhesive leveraging 3M ESPE̓s long-term experience on self-etch adhesives. The composition of LS System Adhesive especially addresses the technological needs of adhesive bonding of the new Filtek LS restorative resin to enamel and dentin.

Filtek LS restorative and LS System Adhesive represent the next generation of restorative filling materials, combining esthetics and mechanical properties you know for conventional hybrid composites with low polymerization shrinkage due to a revolutionary new resin system. The system is well proven by scientific researchers all over the world, confirming the mechanical strength and convenient clinical handling of the Filtek LS System.

suMMary

34

Literature

BraemM.J.,DavidsonC.J.,LambrechtsP.,VanherleG.(1994),Invitroflexuralfatiguelimits of dental composites. J Biomed Mater Res 28:1397-402.

Braga R. R. and Ferracane J. L. (2004), “Alternatives in Polymerization contraction stress management.” Crit Rev Oral Biol Med 15:176-78.

Bouillaguet S., Gamba J., Forchelet J., Krejci I., Wataha J. C. (2006), Dynamics of composite polymerization mediates the development of cuspal strain. Dent Mater 22:896-902.

Braga R. R. and Ferracane J. L. (2004), Alternatives in Polymerization Contraction Stress Management. Crit Rev Oral Biol Med 15(3):176-184.

Brandenbusch M., Meyer G. R., Canbek K., Willershausen B., Ernst C. P. (2007), One year performance of an innovative silorane posterior composite. IADR 2007, Abstract #1581.

Cook W. D., Beech D. R., Tyas M. J. (1985), Structure and properties of methacrylate based dental restorative materials. Biomaterials 6:362-368.

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Technical DataFiltek™ LS Low Shrink Posterior Restorative

Property Resin Matrix Siloranes

Filler Quartz and Yttrium fluoride

Filler Load by Weight (%) 76%

Average Particle Size (µm) 0.47

Curing Time (seconds) Halogen light devices:

Output 500 – 1400 mW/cm2, 40 sec, standard mode

LED light devices:



Increment Thickness (mm) 2.5

Volumetric Shrinkage (Bonded disc method) 0.9%

Fracture Toughness (K1C) 1.6

Flexural Fatigue Limit (MPa) 77

Compressive Strength (MPa) 394

Flexural Strength (MPa) 123

Flexural Modulus (GPa) 9.6

In vitro Wear (3-body wear in µm/cycles) 65/200,000

Number of Shades 4

technIcal data

3M, ESPE, Adper, Elipar, Filtek, L-Pop, Prompt, Sof-Lex, Vitrebond and Z100 are trademarks of 3M or 3M ESPE. Used under license in Canada. AdheSE, Aelite, Alert, APX, Charisma, CeramX, Clearfil, Definite, ELS, Estelite, EsthetX, EvoCeram, Futurabond NR, Glacier, Gradia, Grandio, Heliomolar, Herculite, Herculite XRV, iBond, InTen-S, Miris, Optibond, Point 4, Premise, Prime & Bond NT, Prodigy, Prodigy Condensable, QuiXX, Renamel, Saremco ELS, Solitaire, Spectrum, Spectrum TPH, SureFil, Tetric, Tetric EvoCeram, TPH, TPH3, Venus, Xeno and XtraFil are not trademarks of 3M.

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low shrink posterior restorative ls system adhesive

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