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•
Stop work and report the incident to the dentist immediately.•
Put on full PPE.•
Globules of mercury or particles of amalgam must be smeared with a mercury absorbent paste from the mercury spillage kit (see Figure 4.27).•
This consists of equal parts of calcium hydroxide and flours of sulphur mixed into a paste with water.•
It should be left to dry and then removed with a wet disposable towel and placed in the storage container.•
Risk assess the incident to determine if protocols require amendment.•
Larger spillages still require the evacuation of the premises, the sealing of the area and the involvement of Environmental Health to remove the contamination as a specialist procedure.•
The Health and Safety Executive will be notified under RIDDOR, so that an investigation can be carried out to determine if the practice procedure needs to be changed to prevent a recurrence of the spillage.445
type of dual-cure composite material has been developed, which can be set at the margins by a curing light and then will set chemically beneath the metallic restoration.
Light-cure system
Unlike chemical-cure composites, which cannot set until two components are mixed together, light-cure materials (e.g. Filtek, Solitaire, Helioseal) have introduced an ideal setting system. A single component contains the resin binder, filler and a special catalyst which is only activated when exposed to a very bright light. The spot of intensely bright blue light activates the catalyst and makes the material set in less than a minute. No mixing is required. The unique advantage of this system is that the dentist has more control over the setting time of the restoration, although the material will eventually begin to harden under the influence of the overhead dental light.
The single component of light-cure composites enables manufacturers to supply their product in multidose dispensing syringes, or single dose capsules called compoules (Figure 15.24) with an injector gun (Figure 15.25), thereby allowing the dentist to inject the filling directly into a prepared cavity. The dentist then has as much time as necessary to adapt, contour and trim the filling
Figure 15.24 Composite compoule.
Figure 15.25 Compoule in gun.
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material before commanding it to set. In this way, the time-consuming removal of excess material which has set rock-hard can be avoided.
Just a thin layer of composite is needed to fill a shallow cavity and this only requires one appli- cation of the curing light. In larger cavities this would only cure the surface layer as the light cannot penetrate layers thicker than 2 mm. In order to obtain full curing in such cases, the composite is inserted in a thin layer, then light-cured before adding another thin layer and light-curing again.
This sequence is repeated incrementally until the cavity is completely filled with fully cured composite (Figure 15.26). One way of saving time in such cases is to partially fill a large cavity with a thick layer of lining material, followed by a surface layer of composite which can be cured in one application of the light. The usual lining material for this purpose is glass ionomer cement which is described later.
There are so many different brands of composite materials, and so many different types of curing lights, that it is essential to strictly follow manufacturers’ instructions for the curing time, light bulb life, and care and maintenance of this equipment. A simple test of the curing light’s effectiveness is to cure a small measured portion of composite on a glass block or mixing pad and then check that it has set hard throughout its full thickness.
Composite restoration procedure
The procedure for the placement of a composite restoration is described below, along with a table of the additional instruments, equipment and materials that may be required for the procedure.
•
All dental personnel and the patient wear the correct PPE throughout the procedure, especially orange-tinted safety glasses to counteract the blue curing light.•
All caries is removed from the cavity, without breaching the pulp chamber.•
Moisture control techniques are used so that the cavity remains dry; this may involve the placement of a rubber dam.•
Adequate soft tissue retraction is applied, without causing trauma to the soft tissues.•
Calcium hydroxide lining, or glass ionomer base, is placed to protect the pulp if required.•
Transparent matrix strip is placed interdentally if required, to separate the tooth from its neighbours (Figure 15.27).•
Cavity edges are chemically roughened by being coated with acid etchant for about 15 sec–this is 33% phosphoric acid (see Figure 4.28).
Curing lamp
Wedge-shaped increments of composite material
Figure 15.26 Composite curing technique.
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•
Microscopically, this roughens the enamel surface by dissolving the interprismatic substance and leaving the prisms projecting from the tooth surface.•
This is thoroughly and carefully washed off and collected by the high-speed suction, and the cavity is wiped dry.•
Dentine primer may be placed at this point.•
Resin bond is wiped over the etched enamel and cured for about 10 sec.•
This adheres to the prisms and provides tags for the composite to stick to when placed.•
Shade is determined and the composite material is pumped into the cavity in increments of 2 mm, and cured with the curing light.•
The cavity is gradually fully filled and cured, while the matrix strip is adapted tightly to avoid any overhangs.•
Restoration is finished using a variety of finishing strips (Figure 15.28) and/or finishing burs (see Figure 15.12).•
Occlusion is checked using articulating paper and adjusted as necessary.A summary of the materials and instruments involved is shown in Table 15.5 and the advantages and disadvantages of composite restoratives over others are shown in Table 15.6.
Figure 15.27 Transparent matrix strip.
Figure 15.28 Finishing strip.
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Table 15.6 The advantages and disadvantages of composite restoratives
Advantages Disadvantages
Excellent aesthetics with a wide range of
shade choice Technique sensitive
Adhesive to tooth, using acid etch and
bond Longer procedure than for amalgam
restoration Little marginal leakage occurs, due to
their adhesion to enamel More expensive material than amalgam Sufficient strength in smaller posterior
restorations Not as strong and hard-wearing as amalgam
in posterior teeth Usually only require lining of calcium
hydroxide Possible safety issue with resin bond
Indirect inlay technique possible for larger
restorations Can only use glass ionomer as a base, as
composites react with other bases Fast set with curing light Acid etchant can burn soft tissues if used
carelessly Available in premixed compoules for easy
insertion into cavity Safety issue with curing light causing eye damage; orange-tinted safety shield must always be used
Table 15.5 Composite restoration procedure: materials and instruments
Item Function
Liner or base
material To protect the pulp from chemical shock
Calcium hydroxide lining, and glass ionomer base in deep cavities
Matrix system Transparent matrix strips, to allow curing of the composite through it
Various holder systems available, or held in place manually Plastic instruments To place the composite and remove excess before curing
Various designs available, the most common one being a flat plastic instrument
Ceramic-tipped instruments to avoid sticking of the material to the instrument are available
Finishing
instruments To ensure no overhangs are left and that the surface of the restoration is smooth
Various items used – specially shaped plastic instruments, abrasive strips, polishing discs, polishing burs of various designs
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Safe handling and usage of composite
Great care is required when using the acid etch liquid or gel during the placement of a composite restoration, to prevent soft tissue damage to the patient or the dental team. It consists of a 33%
concentration of phosphoric acid, and this is more than sufficient to cause acid burns and permanent scarring of the patient’s soft tissues, including their facial skin.
Also, the blue curing light used to fast-set the restoration can cause damage to the retina of the eyes if looked at directly, so the patient must wear correctly tinted safety glasses during treatment (orange tinted are best). An orange-tinted protective shield should also be held over the fibre- optic end of the light during use, to prevent the dental team from having to look at the light without eye protection too.
Other uses of composite materials
These materials have a variety of other uses besides tooth restoration, the most usual of which are discussed below.
Restoration of fractured incisors
Before acid etching techniques were introduced, the most satisfactory way of restoring fractured incisors was by fitting a porcelain jacket crown. Unfortunately, this is unsuitable for children as the pulp chambers of immature teeth are too large and crown preparation may cause pulp damage.
This, together with the fact that incisor fractures most commonly occur during childhood, meant that some other form of temporary crown had to be used – and these were of relatively poor appearance.
Composite filling materials and acid etching have transformed the treatment of fractured incisors. Small fractures in children and adults can be permanently restored in this way. Although porcelain jacket crowns may remain the best treatment for extensive fractures, acid-etched restorations provide children with a satisfactory alternative until such time as the tooth, and the patient, are ready for a more suitable restoration.
Enamel margins are acid etched and lined with a bonding agent. A hybrid composite filling material is applied in a clear plastic crown form, such as an Odus pella crown form (Figure 15.29).
When it has set, any excess is trimmed off and the restoration is polished where necessary.
Figure 15.29 Odus pella crown form.
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The acid etch/composite filling technique is also used for building up malformed or misshapen teeth to improve their appearance; for the direct bonding of orthodontic brackets, porcelain veneers and small bridges (see later); and for the construction of temporary splints. The latter are involved in stabilising loosened teeth due to trauma or periodontal disease, and are made by bonding a length of wire or fibre-glass tape to the loose tooth and its neighbours with a light-cure composite.
Fissure sealing
As mentioned in Chapter 13, fissure sealing is used as a caries prevention measure. Occlusal fis- sures and buccal pits are natural stagnation areas where caries commonly occurs. If these fissures can be filled soon after eruption of a permanent posterior tooth, the occlusal surface and buccal pit should then stay free of caries.
The advent of new materials, such as composites and glass ionomer cements, allows fissure sealing to be done with minimal (if any) cavity preparation, because they are adhesive to the tooth structure itself. Retention is obtained by acid etching the fissures or pits. Whichever material is used, any existing caries is removed and the cavity is filled at the same time as the sound fissures.
It is hoped that in the vast majority of cases, the procedure is carried out as a preventive measure on a caries-free tooth anyway, rather than as a treatment for existing disease.
The application of fissure sealants should be done as soon as possible after eruption but requires a completely dry occlusal surface. This is difficult to achieve in young children but may be over- come by applying a fluoride varnish (e.g. Duraphat) as a temporary seal, until a child is co-opera- tive enough to permit the attainment of a dry field for sufficient time.
Unfilled resins
All the composite filling materials described so far consist of a resin binder incorporating an inert inorganic filler. They are accordingly called filled resins. A catalyst makes the resin set, while the filler remains unchanged throughout. This gives the unset material its paste consistency and the set filling its hardness and durability.
Thus it is only the resin and catalyst which are actually involved in the setting process. Several brands of composite make use of this fact by providing a liquid base containing just the resin without a filler. This is called an unfilled resin and sets in the same way as all the others by using the same catalyst. These unfilled resins (e.g. Delton, Helioseal) are available in chemical-cure or light-cure brands.
The advantage of an unfilled resin is its liquid consistency. Both resin and catalyst are liquids and the mixture can be easily flowed over acid-etched enamel, into fissures or mixed with a filled resin paste to give any desired consistency. Unfilled resins are accordingly used as fissure sealants (although coloured materials are also available), and for surface glazing.
Dentine bonding agents
Although acid etching can satisfactorily bond older composite materials to enamel, it cannot bond them to dentine. Small undercuts are therefore required for adequate retention of some composite restorations.
A new group of dental materials are now available which can bond composites to dentine and enamel. There is such a bewildering range of products available, with such a confusing pattern of instructions for use that no consensus on the ideal type of product seems to have been achieved.
However, the simplest product would be one that is a single-component, one-stage application to
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enamel and dentine, without any need to keep the prepared tooth dry. Some light-cured products that approach these ideals are already available, e.g. Optibond Solo Plus, Solobond M. The material used will be an individual choice by the dentist, based on previous experience and knowledge of dental materials.
Glass ionomer cements
Glass ionomers are tooth-coloured restorative materials that are adhesive to all the hard tissues of the teeth, so they tend to be used in situations when little natural retention of the restoration is available, especially in class V cavities. They are composed of a powdered glass-like mixture of aluminosilicate particles and polyacrylic acid mixed with water (Figure 15.30), and although they have a range of shades available, their aesthetics are inferior to composites.
Various other forms are available, such as mixed with silver to produce a harder wearing posterior restoration, mixed with composite (as a compomer) to achieve a restoration with the advantages of both materials, or mixed with other metals (as cermets) for use in tooth core build-ups (for example, Vitremer).
Some products set chemically, others by exposure to the blue curing light as for composites.
Glass ionomer restoration procedure
The procedure for the placement of a glass ionomer restoration is described below. Additional instruments, equipment and materials that may be required for the procedure are shown in Table 15.7.
•
All dental personnel and the patient must wear the correct PPE throughout the procedure, especially orange-tinted safety glasses if a light cure material is to be used.•
All caries is removed from the cavity, without breaching the pulp chamber.•
Moisture control techniques are used so that the cavity remains dry; this may involve the placement of a rubber dam.•
Adequate soft tissue retraction is applied, without causing trauma to the soft tissues.•
Calcium hydroxide lining is placed in deep cavities; this is not necessary in shallower cavities.Figure 15.30 Glass ionomer cement material.
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•
The cavity has a ‘conditioner’ applied, which increases the adhesion of the material to the tooth and improves the marginal seal – the conditioner is either polyacrylic acid or tannic acid.•
This is washed off after about 20 sec and collected by the high-speed suction, then the cavity is dried.•
Shade is determined and the material is carefully apportioned (using the scoop provided) and mixed, ideally using a waxed paper pad and plastic spatula to do so (Figure 15.31).•
The aluminosilicate particles of the powder are very abrasive, and tend to score glass blocks and some metal spatulas during mixing, so these items should be avoided.•
Some materials are presented in capsules which are mixed in a conventional amalgamator and then light cured, once placed (Figure 15.32).•
Material is placed into the cavity and allowed to achieve its initial set, or is light-cured.•
Cervical foil matrix is used when restoring class V abrasion cavities, to produce a smooth surface (Figure 15.33).Table 15.7 Additional instruments, equipment and materials that may be required for the glass ionomer restoration procedure
Item Function
Liner Calcium hydroxide, if any is required, to protect the pulp from the acrylic acid
Plastic instruments To place the glass ionomer and remove any excess material Cervical matrix Foil coated and preshaped for use when restoring class V
abrasion cavities
Cannot be used if the glass ionomer is a light-cured type of material
Finishing materials Varnish or unfilled resin, wiped over the restoration surface to prevent moisture
Contamination
Figure 15.31 Glass ionomer powder, scoop and liquid.
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•
Excess material is carefully removed, without touching its surface as this will produce a chalky appearance – glass ionomer materials cannot be ‘finished’ immediately after placement as other permanent restorations can, unless they are a light-cure type.•
Surface is coated with varnish or unfilled resin while fully setting, to prevent moisture contamination.The advantages and disadvantages of glass ionomer restoratives over others are shown in Table 15.8.
Other uses of glass ionomer materials
Glass ionomer cement has many different uses which depend on two outstanding properties.
•
It releases fluoride and thereby prevents the recurrence of caries in and around the cavity, making it the ideal restorative material in deciduous teeth and especially younger children, where poor co-operation may prevent full caries removal.Figure 15.32 Glass ionomer capsule.
Figure 15.33 Glass ionomer class V matrix system.
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•
It chemically bonds directly to enamel, dentine and cementum without acid etching, so that adhesion is excellent and undercuts are not essential for retention of the material in the cavity, therefore making it suitable for the following uses.○ Unprepared deciduous cavities.
○ Prepared deciduous cavities, where the reduced strength of the material is irrelevant as the teeth will be shed anyway.
○ Fissure sealing.
○ Cavity base.
○ Luting cement for fixed restorations and orthodontic bands.
○ Dentine substitute where excessive loss of tooth substance has occurred, avoiding the use of pinned amalgam restorations.
○ Core build-ups.