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The restorative dental treatment possibilities available to practicing dentists have grown immensely over the past few decades. Considerable progress has been made in the development of composites. Problems which were encountered with earlier materials, for example, polymerization shrinkage, excessive wear and lack of shade stability have been resolved in the meantime.2,9 The current developments of a number of manufacturers are focused on further improving the biocompatibility of their products.2,8
At the same time, the development of ceramics for inlays, onlays and partial crowns has been exceptionally dynamic.1,8,13 Modern glass-ceramics together with adhesive cementation techniques achieve long-lasting and highly aesthetic results.
Laboratory techniques and chairside treatment methods are available for fabricating dental restorations.8 CEREC, for example, has evolved from a system reserved for computer enthusiasts to one that is suitable for the general dental practitioner. It can be used to repair most of the damage that commonly occurs in natural teeth in only one appointment.3,15 Statistical examinations which have been conducted over a period of more than 18 years confirm the clinical reliability of CEREC inlays, which corresponds to that of cast gold inlays.14
There are a series of components that are common to both techniques, which dental professionals have to master. For example, they need a good command of the rubber dam11,12 and the adhesive techniques.5,8 Furthermore, they must be able to faithfully recreate the static and dynamic occlusion in the intraoral environment.
The modern and indication-oriented filling technique involving composites and ceramic inlays allows long-lasting and highly aesthetic restorations to be produced, which are also minimally invasive in many cases.6–8,10
The following practical report shows the results that can be achieved by experienced practitioners using both techniques in the posterior region.
In our practice we use composite resins from the Tetric family of products to fill posterior teeth. According to the information of the manufacturer, Tetric EvoCeram (Fig. 1) is a nano-hybrid composite that can be used for many different indications. It is composed of fillers, pigments and monomers of three different types of nano-particles. As a result, the material demonstrates very low polymerization shrinkage among other significant features. Its wear resistance has been improved compared with that of its predecessor TetricCeram. Dental professionals appreciate its ease of use. The material is easy to apply and can be polished to a high gloss finish.16
The flowable version of Tetric EvoCeram is called Tetric EvoFlow. The material shows outstanding wetting behaviour in the cavity. The application of an initial thin layer in the proximal box or on the gingival shoulder in cervical fillings levels out all irregularities. This layer enhances the marginal integrity of fillings.6
In our practice we have been using the CEREC 3-D system for chairside applications for many years. The latest hard and software of the system allows cavities to be restored immediately with precision ceramic restorations. Experienced dental professionals can incorporate information about the bite situation into the construction process. The milling machine with its diamond cutting instruments is capable of reproducing the finest details.
Since 1998, we have been using the leucite-reinforced glass-ceramics from Ivoclar Vivadent. Up to autumn of 2006 we used ProCAD. In the meantime, the successor product IPS Empress CAD (Fig. 2) has become available. Glass-ceramics have exceptional aesthetic properties. The three-point bending strength of IPS Empress CAD has been increased compared with the predecessor product, without compromising its polishing properties. It is now at 160 MPa. As a result, outstanding long-term clinical results are produced in conjunction with adhesive cementation.
The shade spectrum is based on that of the Chromascop as well as the VITA A-D shade guides. The material is supplied in blanks demonstrating high (HT) and low (LT) translucency. HT-blanks exhibit a low chroma and enamel-like fluorescence. Because of their natural-looking ’chameleon effect’, they are recommended for smaller restorations. In contrast, the LT blocks demonstrate a higher chroma and dentin-like fluorescence. Therefore, they are indicated for larger restorations. In addition, multicoloured blocks have also been developed for IPS Empress CAD. They imitate the natural colour transition (chroma) of the tooth. The incisal area demonstrates lifelike translucency and fluorescence. The chroma and opacity of the material increase within the body of the tooth. These multi-coloured blocks are used to fabricate partial and full crowns.
As mentioned at the beginning, both techniques have certain characteristics in common, which are decisive for the success of the treatment.
Figs. 1–3: Tetric EvoCeram is available in syringes and Cavifils (Fig. 1). IPS Empress CAD is supplied in different levels of translucency. As a result, it is possible to adjust the materials to the different light-optical properties of teeth taking advantage of the chameleon effect (Fig. 2). OptraDam is placed in a flash (Fig. 3).
Even though it was invented more than 140 ago, the rubber dam is neglected in most practices. Nevertheless, absolute isolation is decisive for the success of the adhesive technique. The newly developed OptraDam (Fig.3) from Ivoclar Vivadent AG is a revolutionary isolation product, which does not require the use of clamps. The tension in the rubber is created by the special design of the dam which is inserted in the mucolabial fold (Fig. 4). As a result, the assistant cannot make any mistakes in punching the holes. OptraDam is placed in just a few seconds.12 The rubber dam can be additionally secured in situ with waxed dental floss.
To date, we prefer to use a rather conservative approach to adhesion. Even though many new dentin adhesives have appeared on the market in the past 15 years (some of which have already disappeared again), we like to use Syntac and Heliobond (Fig. 5). In adhesive procedures, several bottles always mean more effectiveness.4 Meanwhile, the ceramic is etched with hydrofluoric acid and conditioned with Monobond-S. Subsequently, Heliobond is applied to the restoration as well as the cavity walls. We use Variolink II for the adhesive cementation of ceramic inlays in very deep and large cavities. In shallower lesions, however, we prefer to use the ultrasound technique in conjunction with Tetric Evo-Ceram. This method allows excess material to be removed with ease using dental floss.
We believe that it is very important to coat the filling or the cement margin of ceramic restorations with glycerine gel (e.g. LiquidStrip) before light curing. This prevents an inhibited layer from forming, which improves the physico-mechanical properties of the composite. Simultaneously, discoloration is prevented.
Intraoral finishing and polishing of the composite fillings and CEREC inlays also demonstrate certain parallels. We usually remove excess with flame-shaped (occlusal) and delicate pointed fine diamonds (proximal). In addition, diamond strips can be used. Subsequently, the static and dynamic occlusion is checked. Flexible discs of different grit sizes are used to pre-polish the restorations. An outstanding high gloss finish is achieved with different rubber polishers. Finally, the restorations are polished with diamond paste.
Figs. 4 & 5: OptraDam in situ. Clamps are not required (Fig. 4). Syntac and Heliobond have been clinically proven for effective enamel and dentin bonding for more than a decade (Fig. 5).
Composite resin filling placed with Tetric EvoCeram
The 22-year-old female patient presented to our practice with complaints in the second quadrant. In the examination, carious lesions were found in teeth 24, 25, 26 and 27. Tooth 26 had been restored with a resin composite filling, which was no longer serviceable (Figs. 6 & 7). Pieces of the filling had broken off and deep secondary caries had developed.
Figs. 6–9: Status in the upper jaw of our patient at the beginning of the treatment. Unserviceable composite fillings are clearly visible (Figs. 6 & 7). OptraDam was placed after preparation. Waxed dental floss was looped around the tooth necks to secure the rubber sheet (Fig. 8). Tetric EvoCeram was first applied to tooth 25. In order to faithfully recreate the contacts, matrices were placed and secured with wedges. An initial layer of Tetric EvoFlow was applied to the proximal shoulder of tooth 26 (Fig. 9).
The teeth were prepared under local anaesthetic. In tooth 26 in particular, the carious tissue had to be removed from areas close to the pulp with an excavator. A rubber dam was placed immediately following this step. OptraDam was used, as it dispenses with the need for clamps. Waxed dental floss was used to closely adapt the rubber dam to the individual teeth (Fig. 8). Once complete isolation from any disturbing influences had been achieved, a calcium hydroxide preparation was applied to tooth 26. Subsequently, the dentin structure of the tooth was conditioned with AdheSE. Furthermore, a thin layer of Tetric EvoFlow was applied over the calcium hydroxide in tooth 26 and cured. In order to properly reconstruct the contacts, a matrix was initially placed only around tooth 25. Syntac and Heliobond were used for bonding purposes. Next, four increments of Tetric EvoCeram were placed and cured. Once this had been accomplished, matrices were placed around tooth 24 and 26 (Fig. 9). The metal matrices called OptraMatrix have proven to be very effective in creating anatomically correct contacts. They feature selectively thinned proximal areas. Because of the crowded conditions in the mouth of the patient, transparent acrylic matrices from the Adapt Sectional Matrix System were used. These anatomically-shaped matrices were held in place with wedges. Subsequently, Tetric EvoCeram was again placed in small increments and cured. The contacts were created with the help of the OptraContact instrument, while the surfaces were contoured with the OptraSculpt instrument. Before the restorations were light cured, a coating of glycerine gel (Liquid-Strip) was applied. Following light curing, the surfaces were finished with fine-grit diamonds. Further finishing was conducted with rotating Opti-Discs. OptraPol rubber polishers were used to polish the restorations to a high-gloss finish (Figs. 10 & 11). Next, the teeth were treated with the fluoridation agent called Bifluorid.
Figs. 10–12: Highly aesthetic restoration of teeth 24–27 (Fig. 10). Even from the lateral aspect, no transitions between the tooth structure and the composite are visible (Fig. 11). The view of the upper jaw shows only very small carious lesions (Fig. 12).
We were highly satisfied with the result. At the recall appointment, the patient no longer had any complaints. The function and aesthetics of the teeth were restored. We were also very pleased with the tight proximal contacts.
Inlay/Partial crown fabricated with the CEREC 3D System and IPS Empress CAD
The 39-year-old male patient presented to our clinic with the request to completely restore his dentition. The teeth showed various carious lesions. We were surprised to find that pronounced secondary caries had developed under the gold inlays, which were around 10 years old, even though the patient practiced good dental and oral hygiene (Figs. 12–14).
Figs. 13–15: The caries in the lower jaw were removed gradually (Fig. 13). Teeth 15–18 before preparation (Fig. 14). During preparation, the extensiveness of the undermining caries lesions became evident. The vestibular wall of tooth # 16 had to be suitably prepared for the restorative procedure. Wedges were placed to stabilize the rubber dam in the embrasures (Fig. 15).
After having removed the old fillings in the lower jaw, we decided to proceed gradually with the removal of the caries to give the pulp-dentin system enough time to regenerate. After an interval of about eight weeks the restorative work was done at four different appointments, one for each quadrant. CEREC inlays and partial crowns were made chairside at these appointments. Each tooth which required restorative work was fully treated in one appointment. Therefore, it was unnecessary to fabricate temporaries. We used both the IPS Empress CAD HT and LT blocks to produce the inlays. The partial crowns were fabricated with the multi-coloured blocks. It took two to three-and-a-half hours to restore each quadrant.
The treatment procedure followed the familiar protocol of the chairside CEREC technique (Figs. 15–17). First, all the teeth requiring treatment in one quadrant were prepared. The teeth were prepared for inlays according to the corresponding guidelines. Particular attention was paid to ensuring the stability of the edges. Thinly tapering enamel areas and spring edges were contraindicated.1 However, undermining areas in dentin were left untouched, as they would be automatically blocked out in the CAD/CAM process and sealed with luting composite during the placement of the restoration.
Fig. 16–18: The inlays in tooth 14 and 17 were correctly positioned with the ultrasound placement technique. Because of the thickness of the ceramic partial crown for tooth 16 (more than 4 mm), this restoration was placed with Variolink II. Wedges and matrices protected the proximal areas from excess resin composite (Fig. 16). In the second quadrant, large lesions were also found under the gold inlays. Partial crowns were fabricated chairside (Fig. 17). Teeth 14–18 after completion of the restorations: 14: Inlay mod, 15: Composite, 16: Partial crown; 17: Inlay mod, 18: Composite (Fig. 18).
A ceramic thickness of less than 1 mm in the isthmus is considered to be very critical. Despite adhesive cementation, the thickness of the ceramic should not fall below this value.
Depending on the size of the lesion, the difference between inlay and partial crown preparation is almost negligible. Thin oral or vestibular walls are reduced by about 1.5 to 2 mm at an angle of 90º. In the process, soft rounded transitions should be prepared in the enamel and dentin areas to accommodate the ceramic (Fig. 17). The joint between the natural tooth structure and the restoration in the aesthetically sensitive vestibular region should not be visible or perceptible with a probe after adhesive cementation.
In very deep cavities, a calcium hydroxide material is used on areas near the pulp. This material is covered with glass ionomer cement. Recently, we have preferred to cover the material with a flowable resin composite following the corresponding dentin bonding as previously described.
In the case at hand, the registration of the static occlusion followed. We used StoneBite for this purpose. The record was taken intraorally in the form of an ’antagonist’ image with the CEREC camera. Following the removal of the bite record, the cavity had to be coated with powder again. Subsequently, pictures of the preparation were taken. The restorations were created one after the other and immediately finished.
At the try-in we make sure that the restorations fit impeccably and we check the contacts. If shading with glazing is planned, the static and dynamic occlusion is ground in at this stage. In most cases, however, excellent results are achieved by simply polishing the restorations intraorally. Only the contact areas are extraorally polished to a high gloss finish with rubber polishers. The occlusion is adjusted after adhesive cementation.
The correct selection of the cementation composite shade can further enhance the aesthetic appearance of CEREC restorations. For this purpose we use the water-soluble Variolink II Try-In pastes. We generally seat restorations with a rubber dam in place. We use the ultrasound technique and Tetric EvoCeram for shallower restorations. Proximal excess is removed with waxed dental floss.
When Variolink II is used to cement restorations, matrices and small wedges are necessary. After adequate light polymerization, the restorations are finished and polished.
For the first step, we use the flexible Opti-Discs. A high-gloss finish is achieved with OptraFine. It is also possible to finish fine fissures in this way.
Fig. 19–21: Teeth 24–28 after completion of the treatment: 24: Composite, 25: Inlay mod, 26 and 27: Partial crown, 28: Composite (Fig. 19). Lateral view after the treatment (Figs. 20 & 21).
The patient was highly satisfied with the functional and aesthetic results achieved in the restorative procedure (Figs. 18–23). A balanced occlusion was restored. The gingiva recovered after only a few days. We were particularly impressed by the irritation-free gingival-dental margin, even in areas that were in immediate contact with the ceramic restorations.
Figs. 22 & 23: Highly aesthetic results after the treatment of the posterior teeth in the upper and lower jaw using the CEREC System.
Both of the described methods are suitable for fabricating exceptional posterior restorations of a very high aesthetic standard, which satisfy both patients and dental professionals. A single tooth restoration requires between 30 min (composite resin) and 90 min (glazed ceramic) to fabricate. If several adjacent teeth are treated at the same time, the working procedure becomes more efficient. Longitudinal studies on composite restorations in posterior teeth, which have been conducted over the past 15 years show that these fillings have a survival rate that is comparable to those made of amalgam. Today, these restorations are indicated for Class I and Class II lesions (including the replacement of individual cusps). The contraindications include the inability to ensure proper isolation as well as clinically relevant allergies against components of the composites or adhesives used. Composites and all-ceramics should be used with caution in patients who grind their teeth (bruxism), lack occlusal support or practice inadequate oral hygiene.
Comprehensive long-term studies on inlays and partial crowns made with the CEREC method have shown a clinical survival rate of these all-ceramic restorations of up to 18 years. The clinical success rate of 90 percent after 10 years is comparable to that of cast fillings, which are considered to be the ‘gold standard.’
When we discuss the different treatment options that are available with our patients, the anticipated size of the lesion usually determines whether we will use a composite resin or CEREC restoration. We prefer to use composite resins to restore small and shallow cavities that involve only one surface. Deep cavities that involve several surfaces are restored with CEREC restorations. This includes teeth in which delicate cusps and walls which would be unstable in the long term have to be overlayed. Of course, financial aspects are also given consideration when we plan the individual cases. Despite the higher costs, many patients choose quality ceramic solutions.
Editorial note: This article was originally published in Cosmetic Dentistry Vol. 2, Issue 1, 2008 and is published here with the kind permission of Ivoclar Vivadent.
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