From Volume 39, Issue 9, November 2012 | Pages 630-636
A number of modern materials are available which allow placement of highly aesthetic anterior restorations. However, some systems are complex and technique sensitive. The authors describe a layering technique for the provision of direct aesthetic anterior composite restorations suitable for a general practice setting.
Resin composite provides the most aesthetic direct restorative material for restoring teeth. Composites offer the opportunity for minimal preparation compared to more destructive indirect alternatives. Some composite materials are specifically intended to be used to build layered restorations, eg Miris (Coltène/Whaledent, AG, Feldwiesenstrasse 20, 9450 Altstätten, Switzerland), Ceram X Duo (Dentsply, York, PA, USA), Enamel HFO (Micerium SpA, 16036 Avegno (Ge) Italy). Such composite systems differ from other composites in that they have different characteristics between the enamel and dentine composite shades.
Composite resins are available with a range of optical characteristics, having a range of translucencies and colours. Whilst in certain situations it may be feasible to create an adequate appearance by using a single composite shade, composite systems intended for layered restorations are composed of distinct enamel and dentine shades. The difference between the enamel and dentine composite is marked with a high opacity and chroma for dentine shades and high translucency and low chroma for enamel (Tables 1 and 2).
| Hue | The basic colour, eg red/yellow/blue |
| Value | The brightness of the colour |
| Chroma | The amount of hue in a colour, eg dark vs light blue |
| Vita Classic Shade | Hue |
|---|---|
| A | Red-brown |
| B | Red-yellow |
| C | Grey |
| D | Red-grey |
Such composite systems allow aesthetically superior restorations to be created provided that each shade is used in the correct position and quantity. Errors in the quantity or position of each shade can result in poor results. Excessive enamel composite tends to lead to restorations that are too translucent and greyish in appearance. Excess dentine composite leads to a restoration that is too yellow and opaque in appearance. Achieving restorations that are optimally aesthetic can be technique sensitive, but rewarding with practice. Some previous guidelines on building layered composite restorations have been complex and included suggestions to mix several shades and materials of varying consistency. Below is a description of a relatively simple layering technique that can lead to optimally aesthetic restorations.
Composite can potentially be used for a variety of restorations, in anterior and posterior teeth. Wear and strength properties of the material are now adequate for acceptable longevity of restorations, in the majority of situations. In addition to standard cavity preparations, direct composite can also be used in a number of situations where indirect restorations have typically been employed. Such indications include:
The use of composite in preference to indirect restorations in such circumstances has a number of advantages:
Direct composite veneers are particularly useful in young patients in preference to porcelain, if gingival maturation is not complete. This is because margins for direct composite veneers can be blended into natural tooth structure better than indirect veneers, meaning that supragingival margins are not visibly apparent as they often are with indirect veneers.1
Composite is also increasingly being used in the treatment of toothwear, for optimal aesthetics and maximum conservation of tooth structure. By layering such restorations appearance can be optimized.
There is not a great deal of research into the longevity of anterior composite restorations. A study investigating the treatment provided in general practice by VDPs and their trainers found a 4.5 year mean survival of composite restorations, but this did not distinguish between posterior and anterior restorations.5 Other research by the same author found a 4.7–7.4 year mean survival age, but again this includes posterior restorations.6 A review article in 2006 found that 5-year survival rate of Class III and V composite restorations is 60–80%.7 This paper noted that Class IV composite restorations have a higher, but unquantified, failure rate; particularly in traumatically injured teeth. This was attributed to increased stresses during occlusal function.
Good oral hygiene and periodontal health should be established prior to restoration placement. Poor gingival health will increase the risk of surface contamination via blood or crevicular fluid, leading to reduced bond strength and increased microleakage.
Prior to placing composite restorations, it is helpful to record the desired shade at the start of the appointment while the natural tooth structure is hydrated. Dehydration of tooth tissue causes an 82% reduction in translucency;8 therefore, the tooth will appear lighter and more opaque if allowed to dry out.
The hue of a tooth progressively reduces from cervical to incisal aspects, and from inside to the outside of a tooth.9 Correspondingly, a more opaque composite should be used in the cervical third and inner portion of the tooth.
It is useful to observe the contour and texture of the tooth (or teeth) to be restored and the adjacent dentition. For complex layering or special effects, it may be useful to take a pre-operative photograph of the contralateral or adjacent teeth for reference during the procedure, if the reference teeth are to be covered by rubber dam.
Polishing teeth to be restored using a slurry of pumice is helpful to remove the salivary pellicle, plaque and surface debris, ensuring that the tooth surface is not contaminated in any way that may interfere with bonding. Removal of old restorations is required to improve bond strength.
After polishing, some form of preparation is usually required. At the margins of preparations a bevel may be useful to help blend the composite into the remaining tooth structure to help disguise the edge of the restoration. Preparation at the margins of the intended restoration can also expose a larger surface area for bonding and there is evidence to suggest that the bond to prepared enamel is improved compared to unprepared enamel.10,11
Moisture control may be satisfactorily obtained in anterior regions via isolation with cotton wool rolls and use of a saliva ejector. However, rubber dam may be necessary, particularly for posterior teeth and, on occasion, lower anterior teeth.
Use of an appropriate dentine bonding agent is mandatory, paying close attention to the manufacturers' directions for use, to ensure that maximal bond strengths are achieved. Dentine should be dry but not desiccated for optimal bond strength; although it is essential that the surface is free from contamination, eg by saliva, blood, crevicular fluid, handpiece oil.12 Desiccation of the dentinal surface tends to flatten the collagen network left after etching, reducing penetration of the bonding agent and leading to absence of a hybrid layer.13 However, excessive moisture leads to increased microleakage14 and poor bond strength. The use of cotton wool pledgets to blot the surface has a risk of leaving fibres on the dentine surface to interfere with bonding (although this would achieve the correct level of drying); so the surface should be gently dried using the 3-in-1 syringe.
There is evidence that rubbing the bonding agent into the dentinal surface improves bond strength and allows time for the bond to permeate.15
The light-curing unit should be well maintained, and the curing tip free from debris and scratches, in order to ensure maximum output (Figure 1). A reduced output will decrease the depth of composite cured.16 It is recommended that the bulb is changed every 3–6 months for conventional light-curing units.17
Composite resin can be pre-warmed to increase its flow18 and therefore improve ease of placement. This may be done by placing the compule in a warm place or by the use of a specially-designed composite warmer (Figure 2). Warming hybrid composites to 54 °C prior to placement has been shown to reduce microleakage,19 and results in more complete curing.20 It should be borne in mind that this completeness of curing could lead to increased residual stress21 and therefore shrinkage,20 so it may be prudent to place smaller increments.
In order to help with the placement of resin, a palatal silicone matrix (or index) is a useful tool.
The matrix can be created in a number of ways:
The matrix may be fabricated chairside, using silicone putty, or in the laboratory, using for example Memosil (Heraeus Kulzer, Newbury, Berks); a clear silicone material (Figures 3b and c).22
The palatal matrix allows the operator to place the first increment against it, providing a guide to placing the correct thickness of material. Once the palatal wall has been completed, this initial increment acts as a guide to the positioning of subsequent increments. Figure 4 shows the placement of composite restorations on the central incisors of the case in Figures 3 a–c. The canines and lateral incisors have already been restored. The pre-existing restorations were retained as a base, having been slightly reduced.
Layering may be done with dentine palatally followed by enamel labially and incisally (2-layer technique), or with enamel palatally, dentine centrally, followed by enamel labially (3-layer technique). The principle of the 3-layer technique is to mimic the position of natural dentine and enamel within a tooth and has hence been termed ‘the natural layering concept’.23 The argument for two layers is that restorations are viewed from labially and hence there is no need for enamel shade on the palatal aspect of the restoration.
In the authors' experience, it is easier and quicker to provide 3-layer restorations rather than 2-layer. By placing the initial enamel shade on the palatal aspect, the increment can be built-up to the full incisal length of the tooth, including the incisal edge, providing a guide to the placement of further increments without the further need for the palatal matrix. The use of clear matrix strips interdentally will allow contact point formation whilst preventing bonding to the adjacent teeth.
Special effect shades such as brown, white and opalescent blue resins can be incorporated into restorations to help blend them into the surrounding natural dentition (Figure 5). Such effect resins can greatly enhance the appearance of restorations, helping to form a seamless transition at restoration margins. Crack-lines, areas of localized hypomineralization and fissure patterns can all be incorporated to enhance the final appearance and disguise the restoration (Figure 6 a–h). However, incorrect placement or over-use of effects can have a detrimental effect on the restoration (Figure 7).
Attempts should be made during resin placement to attain, as far as possible, the desired shape of the final restoration. Should gross adjustment be required, it is best achieved through the use of diamond burs or stones. Contouring the restoration to mimic the adjacent teeth is important in creating an aesthetic restoration. Both the form of the tooth and the patterns of light reflection from the surface should be taken into account and reproduced as far as possible. Appropriate labial contour (which may involve multiple planes) and mamelons can be created. This may be done using finishing burs.
Use of carbide burs for fine finishing is not recommended as, despite providing a smoother surface than diamond burs,24 they have an adverse effect on the restoration marginal integrity.25 Both types of bur provide a poorer marginal integrity than the use of a grit paper. Finishing and polishing can be initiated with the use of abrasive discs, eg Sof-lex™discs (3M ESPE, St Paul, Minn, USA) and rubber points (Diatech Charleston, SC 29413), or Enhance polishing points, cups or discs (Denstply, York, PA, USA), (Figures 4 j–l).
Final polishing can be completed using polishing brushes, eg Occlubrush (Hawe Neos-Kerr, Via Strecce 4, 6934 Bioggio, Switzerland) or diamond/polishing paste, eg Prisma Gloss (Dentsply, York, Pa, USA) (Figure 8).
The range of indications for direct composite restorations is increasing as materials improve. When reconciling the conservation of tooth tissue with the desired outcome of treatment, direct composite is increasingly the option of choice ahead of indirect restorations.
