March 1, 2011
by Joseph Sabbagh, DDS, MSc, PhD, FICD and Philip Souhaid (DDS, MSc, FICD)
For many years, dentists have been looking for the ideal restorative composite material. To date, this material has not been found so much so that a plethora of composite materials is currently available on the market and the research in this field is increasing. Developed 50 years ago, thanks to the work of Michael Buonocore (that introduced the etching concept) and Raphael Bowen (Bis-GMA resin), resin composite restorations have changed the face of dentistry. Everyday, millions of composite restorations are placed worldwide, in different types of cavities, using different bonding systems.
Meanwhile, hundreds of papers are published monthly, reporting the results of studies, mostly in vitro, of different dental materials. It is obvious that what dentists care about is the information or interpretation they can get from such a mass of data that is helpful for them in their daily practice. Many papers providing recommendations for composite selection and clinical guidelines were published (Jordan and Suzuki, 1992; Douglas, 1996; Burke et al., 2002 a,b).
Because of the considerable progress in adhesive technology and resin-based materials, the concept of aesthetic dentistry has changed. Resin composites are widely used in our daily practice to answer the increasing aesthetic demand of our patients. No matter how nice the shape and the shade are; a good restoration does not last long without a good adhesive. A bonding layer applied on the walls of the cavity ensures the retention of the composite to the tooth structure. But it has been shown that the bonding process is technique sensitive and involves different steps (moisture control, etching, rinsing, drying, bonding application, etc.). In order to simplify and shorten the procedure and thus minimize the risk of errors, self etch adhesives were developed, followed by self-adhesive resin cement. So, it was expected that self-adhesive restorative composites would follow shortly.
VertiseTM Flow is the first self-adhering light-cured resin composite used for direct restorations. Its formulation incorporates the OptiBond® adhesion technology eliminating the different steps of etching, rinsing, priming and bonding. Consequently the application procedure is really shortened and made easier, and can be applied in different clinical situations for paediatric and conventional dentistry.
This paper will overview, through well-documented clinical cases, the new generation of self-adhering composite, as well as its indications and the most important steps of using it.
EVOLUTION OF ADHESIVE SYSTEMS
Developed in the early sixties, dental adhesives went through numerous developments and became a large family, involving a lot of technology and know how. Bonding is mainly performed on enamel and dentin that have different compositions and mineral ratios. If bonding on enamel is more predictable, and secured, it is not the case on dentine where bonding is more difficult and sensitive.
The first three generations are not used any more, and were considered mild conditioners rather than real adhesives as having low adhesion. First generation of dentin adhesives (Cervident from SS White) involved more of a chelation between a comonomer (NPG-GMA; N-phenylglycine-glycidyl methacrylate adduct) and tooth surface, generating chemical bonds of resin to dentinal calcium (Sturdevant). Second generations of dentin adhesives (Clearfil Bond System F from Kuraray and Bondlite from Kerr) were relying more on polar interaction between negatively charged phosphate groups in the resin and the positively charged calcium in the smear layer (Retief and Denys, 1989). Bond strength was still very weak and values ranged only between 1-5 MPa.
Third generation of adhesives (Scotchbond 2 from 3M), while preserving the smear layer, were designed to modify it (slight demineralization of the underlying intertubular dentine surface) and allow penetration of acidic monomers such as Phenyl-P or PENTA (Dipentaerythritol penta-acrylate monophosphate).
The three main components of those systems are the acid etch, the primer and the bonding. Application of the acid etch will remove the smear layer and demineralize the dentine, opening thus the dentine tubules. The role of the primer is to enhance the surface wettability of dentin and facilitate the penetration of adhesive monomers into the dentine tubules and demineralized dentin, forming a resin dentin interdiffusion zone known as “hybrid layer”.
The etching, the primer and the bonding can be applied either separately (fourth generation), or simultaneously (6th, and 7th generations). For the fourth and fifth generations, known also as total etch, the acid etch (usually phosphoric acid 37%) is rinsed thoroughly after 20 seconds. Then, the primer and the bonding are applied separately or together.
The sixth and seventh generations are known as self etch adhesives. They do not use phosphoric acid, but contain acidic monomers that simultaneously condition and prime enamel and dentine. Self-etch adhesives can be categorized in two groups, two bottles or one bottle where all the components are mixed together (seventh generation). For the 6th generation, the etching and the primer are applied together (in the same bottle) and the bonding alone (Clearfil SE (Kuraray). There is another type of 6th generation adhesive that has two components which need to be mixed prior to its application (Prompt L-POP (3M-ESPE)). As for the 7th generation, the three components (etchant, primer and adhesive) are combined into a single bottle (e.g. OptiBond® All-In-One (Kerr); G-Bond (GC)).
Another major difference of the self-etch is that their pH is higherthan the phosphoric acid (0,1). It varies between 1,0 and 2,5 resulting in two subgroups: mild and strong self-etch adhesives.
COMPLEXITY OF THE BONDIG PROCESS
Achieving a successful and durable bonding procedure involves many steps, is technique sensitive and time consuming. Usually, dental manufacturers include in every adhesive kit a leaflet explaining the instructions for use. Most of the time, dentists don’t read it and consequently don’t follow the steps precisely, or application time. Deviation from these procedures leads to incomplete resin penetration and results in both reduced bond strength and micro- or nanoleakages (Dal Bianco et al., 2006). Clinically this may cause post-operative sensitivity after composite placement. Depending on the type of adhesive system used, application duration may take 36 up to 115 seconds. The number of steps may also vary from 5 to 12, according to manufacturer’s instructions and number of bottles (Van Landuyt, 2008).
Another parameter of paramount importance is the field isolation of cavities. The use of rubber dam, although highly recommended, is seldom used by dentists (10% usage rate). The external humidity may adversely affect the bonding process if the isolation is not adequately ensured.
Pedodontists on the other hand, have to face another problem related to the behaviour of their young patients, often not enough cooperation. They need to apply the product in a minimum time, and if possible shorten the duration of the procedure.
Taking into account all of the following, dental manufacturers concentrated their efforts to offer a bonding procedure that involves less time, and can be achieved with less steps, thus decreasing the risk of errors.
Many studies have been conducted regarding the stability of those systems (Van Landuyt et al., 2005). Their shelf life is shorter compared to the total etch systems, and their stability is questionable, as the different components may undergo phase separation and show the formation of droplets (Van Luydt et al., 2007).
Last but not least, solvent evaporation is a major problem encountered with adhesive systems. Depending on the type of solvent; water, alcohol or
acetone based adhesives systems show variable sensitivity to temperature, and to evaporation. This will affect product stability and uniformity.
a. Composition and properties
The first generation of flowable composites was introduced in 1996 nearly in the same period as packable composites. They both belong to the hybrid category of composites. In fact, flowable composites have been available for years as cements for veneers and crowns. The main difference is that flowable composites offer a full range of Vita shades for ease of use with other restoratives (Albers, 2002).
The low viscosity of flowable composites can be obtained either by decreasing the percentage of fillers or modifying the resin monomers (Sabbagh J, 2004).
Flowable composites gained popularity, and became an important material in restorative and cosmetic dentistry with various clinical indications. Moreover, the same manufacturer can have more than one flowable product. Soon after, this consistency extended to other categories of resin-based materials, such as ormocers (organically-modified ceramics; ex; Admira-Flow from Voco) and compomers (Dyract-Flow from Dentsply).
Today, a wide range of flowable composites with different percentages of fillers (50% to 70% by weight) are available, and can be classified in low, medium or high viscosity.
Their lower filler loading results in greater polymerization shrinkage and lower mechanical properties compared to other hybrid composites (Labella et al., 1999). Because of their low modulus of elasticity they can be suggested for class V restorations, to absorb the stress concentrated on the cervical region.
b. Clinical applications
Flowable composites are suggested by manufacturers for various indications (pit and fissure sealant, repair of marginal defects, liners in deep cavities etc). Huge differences are observed in the viscosity and flow characteristics of flowable resin composites that can have a potential influence on their clinical behaviour during handling and thus on their clinical indications (Beun et al, 2008).
They were used without any clinical proven background until a few clinical trials were published (Gagliani et al., 2002; Perry et al., 2003; Burgess et al., 2003 Dukic W, Glavina D, 2007). However, manufacturers claim many advantages for these new materials. Their low moduli of elasticity and increased flow capacity might provide more contraction stress relaxation and could reduce the frequency of marginal microleakage and possible de-bonding. The high viscosity of packable composites increases the potential of voids formation and lack of adaptation (Combe et al., 1999). Consequently some authors advised their use as liners in class I and II cavities, especially under packable composites to improve their adaptation but the results were not always in accordance (Estafan et al., 2000; Jain and Belcher, 2000; Chuang et al., 2001). At two weeks, the use of flowable composite did not decrease postoperative sensitivity and marginal discoloration was absent for all restorations (Perdigao et al, 2004).
A very thin layer (small drop) of flowable composite is applied as a cavity liner in the bottom of class II cavities, before placing the hybrid resin composite. Due to their consistency and properties, flowable composite must not be carved or handled with dental instruments (spatula or condenser) as this will cause void inclusion and stickiness to the instrument. They should rather be thinned and painted on the floor of the cavity using a microbrush.
This will enhance the adaptation of the packable composite, eliminate the risk of having voids, and close the irregularities. Moreover the thixotropy of the cavity will be modified, and the risk of composite sticking to the instrument during cavity filling will be solved.
Low viscosity flowable composites can be used as pit and fissure sealant. According to a recent clinical study, the use of flowable composites as sealing materials is equal to other materials for fissure sealing at 24 months (Dukic and Clavina, 2007).
Flowable composite are also used as restorative material, such as for class V cavities. Usually, a medium or high viscosity is preferred.
VertiseTM Flow is the first self-adhering resin composite from Kerr, which includes in its formulation the OptiBond® technology. It is the logical continuum in the chain of product development aiming towards simplification and ease of application. The bonding mechanism with tooth structure is a chemical bonding achieved via the GPDM (Glycerophosphate dimethacrylate) between phosphate functional groups of GPDM Monomers and calcium ions of enamel and dentine.
By including the bonding in its formulation, VertiseTM Flow eliminates the additional steps of etching/priming/bonding, otherwise necessary to bond a resin composite to dentin and enamel.
VertiseTM Flow composite offers high bond strength, high mechanical strength, and other physical attributes comparable to traditional flowable composites. VertiseTM Flow composite has numerous indications: small Class I and base/liner for Class I and II restorations, in pediatric dentistry, as pit and fissure sealant or preventive resin restoration. Additional indications include repair of enamel defects, repair of porcelain restoration, repair of composite restoration, blocking of undercut.
VertiseTM Flow composite is available in nine different shades that covers all the indications. It is a biocompatible and radiopaque product that can bond well to many different substrates including enamel, dentin, porcelain, metals, amalgam and composite.
This product has been under third party in-vitro and in vivo investigations for almost two years. The first clinical study was conducted on 40 class I restorations at the university of Siena, Italy (Vichi et al, 2010). At the 18-month recall, the 40 restorations were re-evaluated. Out of the 40 restorations made with VertiseTM Flow self-adhering material, only 3 showed Bravo score and 1 Charlie score for marginal discoloration and integrity. All other parameters showed Alfa scores. No post-op sensitivity was recorded at any of the recalls. Further clinical investigations are ongoing, and the results are to be published very soon.
CLINICAL CASES USING VERTISETM FLOW
As mentioned previously, VertiseTM Flow has numerous clinical indications, summarized in two main applications; restorative material for small class I or cavity liner for class I and class II that avoid the use and application of an adhesive.
The following three cases will overview the different clinical applications, emphasizing the key steps that will ensure an optimal use of VertiseTM Flow.
The first case is a 25-year- old man showing (small) starting caries on left lower first molar and premolars (Fig. 1). Since the caries do not extend proximally, rubber dam is placed prior to cavity preparation, ensuring more comfort for the patient and the dentist. According to minimal invasive concept, small round burs are used for cavity preparation (Fig. 2). Then the cavities are washed thoroughly with water spray and air dry at maximum air pressure for 5 seconds. The only situation where etching is applied for 15 seconds prior to VertiseTM Flow, is on unprepared enamel (for instance pit and fissure sealant). This will enhance and facilitate the bonding mechanism process. Whenever possible, prep (bevel) all margins prior to application of VertiseTM Flow. Shade selection is made before rubber dam placement. Then a small drop of VertiseTM Flow is dispensed onto each of the prepared cavi
ty with the provided dispensing tip (Fig. 3[e1]). A bendable brush is used to spread and paint actively for 20 seconds the first increment of VertiseTM Flow acting as a thin adhesive layer (< 0.5 mm). It is of paramount importance to respect this step, and brush the first increment using some pressure before polymerizing it for 20 seconds using an adequate light curing device (LED or halogen) (Fig. 4). Additional increments of VertiseTM Flow are placed and polymerized. Excess of material around margins is removed with the brush if necessary. The delivering tip and the brush are single use. According to the manufacturer, if using dark shades such as universal opaque (UO) or A3.5, polymerization time is extended to 40 seconds per layer. Figure 5 shows a postoperative view of the final restorations. Then the occlusion is checked and the composite is finished and polished using fine diamond burs and silicone autoabrasive cups (Hi-LusterPLUS and Occlubrush®). Figure 6 shows the restorations after 13 months.
The slight shade mismatch seen in some restorations may be explained by the fact that the initial versions of VertiseTM Flow were available in only two shades (A2 and A3, 5).
Class II restorations with VertiseTM Flow as Total Preparation Liner.
A 24-year-old woman presented complaining of a broken amalgam on tooth 46 and occluso-mesial decay on tooth 47 (Fig. 7). After delivering anaesthesia to the patient, the broken amalgam was removed under copious irrigation and the cavities were prepared and the decay removed using a round metallic bur. The cavities were isolated using OptiDamTM and SuperMat® matrix was applied on tooth 46 (Fig. 8). Herculite® XRVTM Ultra composite was used for restoring the cavity after applying a thin layer of VertiseTM Flow using the provided application brush. Then a stainless steel sectional matrix and a separator are applied on the second lower molar to ensure an adequate contour and a tight contact point (Fig. 9). A very thin layer of VertiseTM Flow (<0,5 mm) was applied in the bottom of the cavity and brushed and painted actively for 20 seconds (Figs. 10 & 11) to obtain a uniform layer. Excess material around margins are removed using a clean brush and the VertiseTM Flow is light cured for 20 seconds. Different increments of Herculite® XRVTM Ultra (dentine A3 and enamel A3) are used to build up the restoration. The first deep increments applied to the gingival margins are light cured for 40 sec, to ensure an adequate conversion rate. The thickness of each increment should not be more than 2mm. Light cure each increment according to manufacturer’s recommendation. Figure 12 shows the final restorations before rubber dam removal and finishing and polishing.
This case shows a 20-year-old man presenting for a full arch restoration of teeth 35 with an occluso distal decay, and teeth 36 and 37 with small class I caries. Figures 13 & 14 show respectively radiographic and clinical preoperative views of the case. After cavity preparation, the teeth are isolated using a rubber dam (OptiDamTM) applied on the left lower arch (Fig. 15). VertiseTM Flow was used as described previously for restoring the 36 and 37, and as a cavity liner in tooth 35 under the composite. Figure 16 shows the restorations before rubber dam removal and composite finishing and polishing and Figure 17 shows the postoperative restorations after one month.
VERTISETM FLOW AND PEDIATRIC DENTISTRY
Another very interesting and very promising indication of VertiseTM Flow is pediatric dentistry. Over several decades, dentistry has experienced many scientific advances in prevention and restorative dentistry. Regarding pediatric dentistry, efforts have been focused on non-invasive treatments to reduce patient’s caries risk by using the most advanced adhesive and composite products. These changes have allowed more efficient oral health management for children. The three basic components of any preventive program for children must include: fluoride therapy, oral hygiene instructions and pits and fissure sealants. Many recent studies have investigated the use of flowable composites as a replacement of sealants, thus ensuring more retention on primary and permanent teeth (Corona et al., 2005, Asselin et al., 2009 and AAPD, 2009).
The use of VertiseTM Flow will give the patient at least the same protection as with flowable composites used with self-etch adhesives with the main advantage of time reduction during placement. Moreover, this product will enhance all the programs of prevention and specially the primary dental health programs by using it as the main component of any preventive resin restoration (PRR). Another interesting application of VertiseTM Flow in pediatric dentistry is to use it as a liner in deep cavities of primary and especially young permanent teeth. It will replace the glass-ionomers that are usually used because it ensures more retention and adhesion to the composite.
Impact on Daily Practice and Future Perspectives
The easy application, the time saving (approximately 2 min per cavity) and wide spectrum of applications will make it a mandatory product in our dental armamentarium for daily practice. From a clinical perspective, at 13 months the product works perfectly with excellent retention and aesthetics and does not show any sensitivity or secondary caries.
Long-term clinical studies must continue to ensure and investigate bonding durability and microleakage in restorative and pediatric dentistry.
However, some important issues must be kept in mind to ensure a successful use and application of VertiseTM Flow:
– Refrigerate the material upon reception, and allow it to reach room temperature 30 minutes prior to use.
VertiseTM Flow is considered as a new category of resin-based restorative materials.
– The first layer must be thin (<0.5mm), and must be painted for 15-20 seconds, before polymerization. OH
Dr. Joseph Sabbagh is Assistant Professor, Dpt of Restorative and aesthetic dentistry, Lebanese University-Beirut-Lebanon.
Dr. Philip Souhaid is Professor, Ortho-paediatric dentistry, Dental College International.
Oral Health welcomes this original article
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