6. Modern methods of

6. Modern methods of carious cavities preparation for composite materials placement. Conventional method of carious cavity preparation. Technology of micro-preparation (art-technique), tunnel preparation and others.

In recent times the term “Minimal Intervention Dentistry” has been used to describe a new approach to the treatment of the disease of caries. It is widely acknowledged that this is a bacterial disease and must be treated as such. The pattern of attack of the carious lesion and its progress through the enamel and dentine has been understood for many years and has tended to dictate the treatment methods used. However, the purely surgical approach to caries control, as taught by GV Black, is now recognised as being far too destructive to be used as the first line of defense. It is highly inefficient because it does not eliminate the cause of the disease and at the same time it leads to a continuing process of replacement dentistry where in the cavity just gets larger, the restoration is subjected to an increasingly heavy load and the tooth gets weaker.

Minimal intervention means that there should be greater emphasis upon education and direction of the patient towards self care with the intention of preventing or healing the disease in the first place and eliminating, or minimising, the need for surgical intervention. In fact it is possible to heal and remineralise a lesion providing it has not progressed to the stage of surface cavitation. It is not suggested that this approach is any easier than traditional surgery but it is far more conservative of tooth structure and offers the possibility of far greater longevity for the dentition in general. It also means that it is unacceptable to sacrifice natural tooth structure through the preparation of relatively large architecturally designed cavities on the assumption that this will, in any way, prevent further disease.

The knowledge required for the adoption of this new philosophy has been accumulating for a number of years and the principles have been utilised in enough practices to suggest that they are sound. There have been many articles in the scientific literature over the last 20 years suggesting greater emphasis on preventive measures and modified cavity designs and there are now at least three text books covering the subject in some detail. There is no doubt that the old concept of “extension for prevention” should, at this point, be discarded but it is acknowledged that there is a need for further investigation into the cavity designs now being proposed to take its place. It must not be assumed that, just because the cavities are smaller, that they are easier to prepare.

It is understood that no restorative material can be regarded as permanent, and that there may well be further breakdown of either tooth structure or restoration. Once the integrity of a tooth crown has been breached by caries followed by preparation of a cavity the remaining tooth structure will be weakened and subject to further breakdown. With each replacement, the cycle is likely to move faster to the next stage of breakdown and replacement. Significantly, any alteration to the occlusal anatomy of a tooth, through placement of a restoration, may lead to changes in occlusal harmony. Even a minor change in occlusal anatomy can lead to the introduction of increased stress on remaining cusp inclines or movement of opposing teeth leading to the development of deflective inclines and to functionally opening contacts. Any or all of these changes may speed the decline of the occlusion and may lead to periodontal problems as well. It is logical, therefore, to retain as much of the original tooth crown as possible and deal with a lesion in a very conservative manner.

The cavity designs suggested by Black required geometric precision with sharp line angles, flat floors and removal of all signs of demineralised tooth structure. Minimal intervention suggests remineralisation of any enamel margin that is not yet cavitated as well as remineralisation of the lesion floor to avoid irritation of the pulp. Demineralised enamel around the margin of the lesion will be restored during the stabilisation phase of treatment aimed at elimination of the disease through the application of fluoride and CPP-ACP. The floor of the lesion will be remineralised through the placement of a glass-ionomer foundation for the restoration and this, at the same time, will seal the margins against microleakage.

Preparation of a cavity may therefore be very conservative indeed. The ultimate aim will be simply to restore the surface of the crown of the tooth to prevent further accumulation of plaque on to or in to any roughness or cavitation that has arisen from the caries process. Access to the lesion should therefore be very conservative and undertaken with care. Open only as far as necessary to allow clear vision in to the lesion. Clean the walls of the lesion sufficient to provide a clean dentine surface around the full periphery so that there can be an ion exchange adhesion between the tooth structure and the glass-ionomer base. Demineralised dentine can remain on the floor providing there is sufficient strength in the glass-ionomer to withstand occlusal load. Both clear vision and a tactile sense are valuable in limiting the depth and extent of the preparation and to thus maintain the maximum strength in the remaining tooth crown.

 

The following discussion of the proposed classification is included to clarify the significance of the minimal intervention approach to the treatment of a caries lesion. There is a basic problem within the concept of the original GV Black classification because it identifies the position of a lesion and prescribes a cavity design regardless of the size and extent of the lesion. This means that there will be a standard amount of tooth structure removed whether it is involved with the disease or not. The result is that the cavity prepared for the initial lesion is often larger than it needs to be and subsequent replacements will therefore be larger still. The GV Black classification does not make allowance for this progression and it is therefore difficult for the profession to gain proper recognition for the increasing complexity posed by preparation and restoration of the enlarging lesion. This problem is taken into account with the proposed new classification, to the advantage of both the patient and the profession.

The concept of minimal intervention cavity designs should not be difficult to accept and visualise as a replacement for the traditional GV Black classification. After all, the latter is a classification of cavities wherein the cavity design is specified for each lesion. However, the understanding of the disease process and the materials used to repair the lesions have both changed considerably in recent years and it is quite apparent that an infectious disease cannot be cured by surgery alone.

Therefore, if minimal intervention is to be adopted as a philosophy, there is a need for an entirely new classification that will identify both the position of a lesion on the exposed crown of a tooth and the extent to which it has progressed. It is neither necessary nor desirable to specify any particular design for the cavity that may have to be prepared. It is important to be able to identify a lesion before it becomes cavitated so that it can be subjected to treatment by remineralisation and subsequently kept under observation until healed.

However, it is accepted that, following loss of surface integrity and cavitation, there will be a need for surgical intervention simply to eliminate surface cavitation and prevent further plaque accumulation. At the same time the restorative material must be able to properly seal the margins against microleakage so that remaining bacterial infection within the cavity will be isolated and further invasions will be prevented. This means that glass-ionomer is the primary material of choice and it can be laminated with a resin composite if required. The result will be stasis within the lesion with the potential for remineralisation. Thus the cavity design, and the material used to repair it, should be dictated solely by the position and extent of the lesion rather than any pre-ordained geometric cavity design.

Cavity Preparation Techniques

At the time of the development of the GV Black classification radiographs had yet to be developed so a cavity was already moderately extensive before it was detected. Rotary cutting instruments had just been introduced and these were used in conjunction with hand instruments for cavity preparation. The resultant cavity was expected to be of a very precise design with flat floors, sharp internal line angles and precisely positioned walls. Dovetails and other retentive details were based upon the carpenter’s principles and retention of tooth structure was of secondary importance. Undermined enamel had to be removed because it was regarded as weak and subject to fracture during restoration placement or subsequent occlusal stress and margins had to be placed in so-called “caries free areas”. Hand instruments were mandatory to complete the cavity to ensure the achievement of the required precision.

The concept of minimal intervention is based upon very early detection of a lesion with surgical treatment undertaken only if surface cavitation has occurred. In view of the potential for remineralisation and the presence of adhesive restorative materials, as much natural tooth structure as possible should be retained, leading to minimal further damage to the tooth. This is logical on the grounds that no restorative material is the equivalent of enamel and dentine in aesthetics or function and the more tooth structure removed the weaker the remainder. The principles of carpentry no longer apply, hand instruments have been largely abandoned and methods for surgical treatment of the carious lesion have been refined. It is suggested that cavity preparation is even more demanding than previously in as much as preservation of remaining tooth structure is of the greatest significance. Extension through the entire fissure system on the occlusal surface is undesirable because areas that are not extensively involved in the caries lesion can be sealed with glass-ionomer. Inclusion of the occlusal fissure in the design for restoration of a proximal lesion is often not necessary. Maintenance of the entire ring of enamel around the crown of a tooth is desirable even though there is a proximal lesion below the contact area. Areas of demineralised enamel that are still smooth can be remineralised and/or sealed with glass-ionomer.

Techniques for the preparation of cavities of limited extent have been modified considerably in recent years. The rotary cutting instruments have now reached a very sophisticated level of precision using burs made of mild steel, tungsten carbide or diamonds of various grit size. There has also been progress in alternate methods of removing tooth structure such as lasers and air abrasion and each of these techniques deserves some consideration.

Probably the greatest risk with the use of rotating instruments is the removal of more tooth structure that necessary. The higher the speed of rotation the lighter the tactile sense and the more tooth structure can be removed inadvertently. It is particularly dangerous to use an air- rotor handpiece at ultra high speed to try to refine the out line of a cavity design because of the speed of removal of tooth structure. Obviously, the larger the cavity the weaker the remaining tooth and one of the prime objects of minimal intervention dentistry will be promptly lost.

It is suggested that ultra-high speed should be used only for removal of old restorations and for gross reduction of tooth structure in the initial stages of the preparation of cavities.

Intermediate high speed is a very useful speed group because there is a fine tactile sense available while at the same time reduction of tooth structure is carried out promptly. At 100,000rpm. a small cavity can be accessed readily with minimum vibration or discomfort and maximum control over depth of penetration and extension. Using a fine diamond bur at 30 – 60,000rpm. it is possible to place a fine bevel on the enamel margin with great precision. A small round mild steel bur, rotating at about 2- 5000rpm, is the preferred instrument for removal of infected dentine around the margin of the newly accessed lesion with the object of exposing the sound dentine that will be required for proper adhesion and sealing of the cavity. It is interesting to note that infected dentine will not show a pain response to a bur or hand instrument so there is ofteo need to use local anaesthesia and pain can be used as a control for cavity extension.

 

NON-SURGICAL MANAGEMENT OF DENTAL CARIES

 ART-technique

The knowledge that progression of caries is dependent upon a continual supply of substrate has been utilised in the concept of stepwise excavation. If the supply of sugar substrate is stopped, the bacteria are no longer able to metabolise and their numbers reduce and the activity of the lesion slows.

For grossly carious cavities, stepwise excavation may be used. Caries is removed in two steps, 6–12 months apart. At the first visit access is gained, caries is removed from the periphery only and soft caries is left on the cavity floor. The cavity is lined with calcium hydroxide and restored with glass ionomer. It is important to achieve a good seal with the glass ionomer. At the subsequent visit, on reentry into the cavity the dentine is found to be harder and drier with fewer microorganisms present. Thereafter, the material can be removed and the cavity restored with a longer-term material, such as composite or amalgam.

The separation of the bacteria from the oral cavity results in the lesion hardening and a reduction in the number of bacteria to levels which do not maintain lesion progression. The hardening of the lesion means that no re-entry is necessary and it is no longer necessary to remove the contaminated areas overlying the pulp. This preserves the pulp integrity and prolongs the life of the tooth. This technique was first suggested in the 1960s but has gained favour following more recent research (Bjorndal and Thylstrup, 1998).

 Preparation of carious cavities by ART-technique.

Atraumatic restorative treatment (ART – method), is suggested by Professor Taco Pilot (Netherlands). This technique envisages no preparation by burs (only necrectomy with excavator). After necrectomy, the carious cavities are filled with materials with anti-carious action (glassionomer cement, compomers). If the treatment is conducted in the initial stages of caries, it allows you to completely stop the progression of caries. Indulgent restorative treatment envisage minimum of pain. This technique can be used at all stages of development of deciduous teeth in children with increased nervous excitability.

 

Carisolv

Chemomechanical removal is an alternative technique for removing caries. It involves the use of a chemical solution which softens carious dentine, thus allowing easy removal. Local analgesia is not usually required. Sodium hypochlorite dissolves organic material. This property is used in the formulation called Carisolv (MediTeam, Goteburg, Sweden). The material is presented in a blue gel formulation and applied on to the surface of a carious dentine lesion. The hypochlorite, given sufficient time, partially breaks down the organic material and kills the bacteria, rendering the lesion caries free. The gel is placed over the carious lesion (Fig. 1).

After 10–20 minutes the gel is washed away and the cavity can be restored with an adhesive material. It has the advantage of being a painless procedure, but although a bur is no longer needed to remove carious dentine, one is still needed to access the lesion. A bur is used to remove enamel or dentine to gain access to the body of the lesion.

                                       

 

Clinical situations where this technique may be preferred include:

■ Root caries.

■ Cervical caries.

■ Cavitated carious lesions.

■ In needle-phobic patients.

■ Where local analgesia is contraindicated.

■ In countries where there is a limited availability of rotary instrumentation.

Studies have shown that the technique is successful in removing caries but it has not become a common clinical procedure in general practice. It has perhaps a greater application for atraumatic restorative treatment (ART) in underdeveloped third world countries because of the minimal requirement of rotary instrumentation.

 

Heal Ozone – designed by famous German company KaVo. The device generates ozone, which with a special handpiece and silicone cap is given on the work surface of the tooth (Fig. 2).

Ozone – one of the most highly active oxidants. Caries treatment with ozone is based on the fact that at a certain concentration and exposure time of ozone kills cariogenic bacteria  without affecting healthy cells.

 

 

 

 

Laser cutting of hard tissues

Laser stands for Light Amplification by Stimulated Emission of Radiation. In essence, a dental laser is a medical device that generates a precise beam of concentrated light energy. A laser’s characteristics are based upon the absorption rates of its wavelength in hard or soft tissue and in other dental materials. Certain wavelengths have an affinity for red pigmented structures which makes them particularly effective for use in the oral cavity in relation to soft tissues while other wavelengths have been found to be effective on hard tissues.

 

Patient discomfort can be reduced with lasers and the need for local anaesthesia is reduced but not completely eliminated. Some procedures can be completed in less time thaormal but the lack of any tactile sense means that accuracy and precision may be compromised particularly in relation to cavity preparation in hard tissues and in areas of difficult access.

 

 

 

A laser’s wavelength determines many of its properties and capabilities because different wavelengths are absorbed by tissue at varying rates. Specific wavelengths can enable greater precision and accuracy and at the same time minimise the potential risk of lateral tissue damage. There are lasers available in varying wavelengths ranging from the Argon Laser, with a wavelength varying from 488nm to 514nm, to the Carbon Dioxide Laser with a wavelength of about 10,600nm.

Currently the one of choice for cavity preparation is the Er:YAG [Erbium Yttrium Aluminium Garnet] Laser with a wavelength of 2940nm. This wavelength is highly absorbed in water so it is useful for the selective removal of caries and for actual cavity designs in limited situations.

 

 

The laser itself is generated within the machine then guided via a series of gold mirrors along the handpiece to emit from the tip within a water jet. It is the energy released through the water that does the cutting and guidance is achieved through a red guide light. Both the power and the pulse rate of the laser are variable and the type of tissue being removed can be detected through the sound of the pulse. Progress of tooth removal can be monitored, particularly with the use of magnification, and the resultant cavity floor and walls are sufficiently rough to accept adhesion with resin without etching. It would seem at this time that the laser is most useful for smaller lesions where access is simple and in many cases local anaesthesia is not required.

		Fig. (left)  A decision was made to restore this tooth with a direct, acid-etch composite resin veneer   Fig. (right)  Er:YAG 2,940 nm laser used to remove existing composite filling and to laser etch the labial surface
		Fig. (left)  Finished restoration   Fig. (right)  For interstitial access, a dulled metal matrix can be used to prevent laser damage to the adjacent tooth surface
		Fig.  Er:YAG laser ablation of occlusal enamel and cross-section to show depth of penetration

 

Preparation of larger cavities can be tedious and time consuming with little gain from the patient point of view. It must be noted that, even though the Er:YAG laser is designed for cutting hard tissue it will also cut soft tissue and therefore care is required to avoid damaging the surrounding periodontium. Rubber dam application is desirable for all applications on hard tooth structure. The main limitation in the application of a laser for cavity preparation is the lack of tactile sense and therefore the difficulty of limiting penetration in to sound dentine. The laser cuts hard tissue more rapidly and efficiently that softer tissues such as demineralised dentine on the floor of a cavity. Its greatest value then is in entering a lesion but it is probably more accurate to define the cavity limits using a conventional rotating bur.

It is unquestioned that the patient avoidance of restorative dentistry is based upon the perceived association of such procedures with pain. Local anaesthetic drugs and techniques can address the demands on delivery of care, but the emergence of many innovative mechanical and chemical modalities for tooth cavity preparation and caries control during the last 15 years bears testimony to a desire to fi nd a clinically acceptable replacement to the dental turbine. This is not just a cosmetic exercise, as the risks of pulpal temperature rise and iatrogenic healthy tooth tissue damage, together with the sensory effects of sound and vibration associated with the dental turbine, have been investigated and acknowledged for many years. With this in mind, it is of little comfort that the rates of tissue ablation with rotary instrumentation remain faster than the alternatives. The wide application of current commercially-available laser wavelengths that have been shown to be safe within correct power parameters, endorses their incorporation into the armamentarium of the restorative and surgical dentist. With the rapidly-growing concept of early intervention of caries, together with the general move away from direct metal restorative material and an embracing of ‘non-classical’ micro-retentive tooth cavities, there is a strong argument that laser-assisted cavity preparation, caries control and bonding techniques will find growing acceptance.

Air Abrasion

Air abrasion, also called kinetic cavity preparation, particle beam or kinetic abrasion technology, uses the kinetic energy of microfine (20-50 micron diameter) particles of alumina (aluminium oxide – Al2O3) in a high pressure air stream to remove tooth structure by brittle micro- fracture. The failure of brittle materials during air abrasion occurs by a process of crack creation, extension, and erosion.

When the abrasive particles impact such a surface, the depression grows, and radial and lateral cracks are generated in the area. The cracks ultimately join together to isolate and remove a piece of the material. The alumina particles are delivered intra-orally using a handpiece with contra-angle or sickle configuration, fitted with a nozzle through which the particle beam is directed on to the tooth. Alternative powders that can be used for air abrasion include sodium bicarbonate, urea, and dolomite. It should be regarded as an adjunct to, but not a universal replacement for rotary instruments. The main indications include the preparation of minimal access through enamel for occlusal lesions on posterior teeth as well as limited debridement of dentine lesions without local anaesthesia. However, it must be noted that large areas of softened infected dentine are not hard and brittle so it has limited ability to undergo brittle fracture.

Therefore, these areas cannot be cut efficiently with air abrasion and alternate techniques are recommended. There are now several suppliers of air abrasion technology and a range of equipment is available. Quite complex units with advanced features such as supersonic handpieces, which increase particle velocity and thus cutting speed, are available. Pulsing of the particle stream through the cyclical operation of valves is possible and air desiccation and particle agitation can be incorporated to prevent clumping and blockages of the powder.

Microprocessor control of air pressure is available and the particle parameters can be varied. With more complex equipment, a remote control unit, small enough to fit into the palm of a hand, provides control of the basic parameters of the instrument, allowing fingertip control without having to move away from the patient. The energy delivered by the abrasive particles is directly related to the airflow and the particle size. Doubling the particle size from 27 to 50 microns multiplies the mass, and thus the kinetic energy, by a factor of eight. While this will accelerate tooth removal it will lead to more discomfort for the patient, particularly during the cutting of dentine, although the relationship between energy and discomfort is not linear. In addition, there may be an increase in dehydration which is often interpreted as a cold sensation. There is, therefore, an inherent trade-off between increasing cutting power (energy) and the level of patient comfort i.e. the annoyance factor.

In practice, this means that a range of particle sizes should be employed beginning with 34 microns for cutting enamel and moving to 27 microns for removing caries. Note also that air abrasion will not effectively remove the smear layer from dentine, but rather creates one. Acid etching should be used to remove the smear layer prior to bonding of resins to dentine. It must be recognized that there are both advantages and disadvantages arising from the use of this equipment for cavity preparation. There is a reduced need for local anaesthesia as well as a reduction in the “annoyance factor” for the patient. However, the use of rubber dam is strongly recommended to help control the distribution and inhalation of the dust. Both conventional intra-oral high velocity evacuation and additional extra-oral high performance vacuum systems are required. The extra-oral system removes the small amount of dust, approximately 10%, which escapes the intra-oral evacuation system, and also provides filtration of the air in the room. In terms of personal protective equipment, a mask is considered adequate protection but both staff and patient must wear eye protection because alumina particles may cause mechanical injury to eyes. The main limitation in the use of air abrasion is the lack of control in the depth of penetration in to hard healthy tooth structure. While it may be of value for entering a lesion there is a complete lack of tactile sense and it is ofteecessary to revert to a rotary cutting instrument to define the limits of the cavity.

 

Some of the situations where the air abrasion has particularly proved a boon include:

1.                Removal of superficial enamel defects – these are much easier with the air abrasives since they result in removal of less tooth structure than the drill.[8]

2.                Air abrasion is an excellent tool for detection of pit and fissure caries – when clinical, radiographic, and patient risk factors make pit and fissure caries suspect, air abrasion can be used to remove the organic debris and determine if caries is present. Use of burs for this procedure would remove far more sound enamel than the few micrometers removed with air abrasion.

In the event of the operator not locating any carious lesions, the area can easily be sealed using a pit and fissure sealant.

If caries is limited to enamel, then a sealant or flowable resin-based composite can be placed.

If caries penetrates into dentin, then the preventive restoration can be used with a heavily filled resin in deep or wide areas subjected to forces of mastication. Sealant material may be used to cover non-carious pits and fissures.

Additionally, caries detector dyes may also be used in conjunction with air abrasives to detect incipient lesion and treat them appropriately.

3.                Air abrasion can also be used for the removal of pit and fissure surface stain on enamel before placement of a resin-based composite restoration or porcelain veneers.

 

  Teeth where the caries is restricted only to a small section of the tooth can also be prepared using air abrasives for conservation of sound tooth structure. Box-preparations for Class II cavities can also be prepared.

  Surface preparation of abfractions and abrasions – air abrasion breaks the glaze of the highly polished surface that is not suitable for bonding and produces a highly textured surface that is excellent for the wet dentin-bonding technique.

  Removal of existing restorations – the particles of the air abrasives can be used at higher pressures for removal of old amalgam restorations for replacing them or for removal and repair of composites, glass ionomers, and porcelain restorations.

 

  The use of local anesthesia while working in dentin may be avoided because of their cooling action through high pressure air.

 

SURGICAL MANAGEMENT OF DENTAL CARIES

Ultraconservative caries removal

This technique involves preparing the tooth minimally by cutting a 1 mm bevel in the sound enamel surrounding the cavitated lesion. No further preparation is carried out and the tooth is restored with acid-etch retained composites and fissure sealant. This technique has been used successfully to arrest occlusal caries (Ricketts, 2001).

Conventional methods of carious dentine removal

Access is the surgical term used to describe the procedure for gaining clearance to see and surgically remove caries. This generally involves cutting sufficient enamel and dentine away with burs to provide sufficient access to the caries. High-speed burs are used to remove enamel to expose the softer dentine that is then removed either by high- or slow-speed burs. These burs remove softened dentine along the EDJ to leave a hard, clean dentine  surface. It is particularly important to remove soft caries along the EDJ. Hard dentine contains inconsequential numbers of bacteria preventing lesion progression. Softer dentine contains higher quantities of bacteria which have the potential to continue the tissue destruction. Removal of softened dentine along the EDJ and the placement of  a subsequent restoration arrest the caries process. The need to remove all pulpal caries is not as imperative as that along the EDJ. A balance needs to be achieved by removing sufficient caries to prevent progression and yet conserve the pulp’s vitality. Provided the soft dentine that appears wet is removed, the vitality of the pulp should be protected.

Occlusal restoration

The technique for an occlusal restoration is as follows:

■ Check the occlusion: use articulating paper to mark the occlusal stops (where the upper and lower teeth occlude together). These should be preserved if at all possible during cavity preparation.

 ■ Consider local analgesia.

■ Shade selection.

■ Isolation: again, ideally a rubber dam should be placed but where this is not possible, cotton wool rolls or dry guards and suction must be used.

■ Cavity preparation: open into the area of caries using a small round or pear-shaped diamond or tungsten carbide bur in the high-speed handpiece. Enough enamel should be removed to give access to the caries in dentine. This caries is then removed with a round stainless steel or tungsten carbide bur in a slow-speed handpiece. It may be necessary to use the high-speed handpiece again if the caries is extensive and more enamel has to be removed to gain access to the carious dentine. Caries should be removed from the enamel–dentine junction first. Check that all the soft dentine has been removed by running a sharp probe along the enamel–dentine junction. Only when this area is clear should caries removal from the floor of the cavity be carried out, either with a round bur in the slow-speed handpiece or with an excavator. When the caries removal stage is complete, the cavity should be reassessed. For cavities that are to be restored with resin composite, it is not necessary to remove unsupported and undermined enamel.

■ Lining: the choice of lining depends on the depth of the cavity. In minimal cavities no lining will be necessary; in medium depth cavities a lining is indicated and this may be achieved using a resin-modified glass ionomer. In very deep cavities a sub-lining of calcium hydroxide should be placed.

■ Dental adhesive: this technique depends on the dental adhesive system being used (see above).

■ Filling the cavity: composite resin should be placed in small increments of less than 2 mm in depth and each increment fully cured. Ideally each increment should touch the minimum number of walls possible to reduce the effects of polymerisation shrinkage.

■ Shaping the occlusal surface: the final increments should be shaped to mimic the shape of the occlusal surface of the tooth. Following final curing, check all the margins with a probe to look for deficiencies or ledges.

■ Polishing: once the rubber dam has been removed  the occlusion should be checked by asking the patient whether the restoration feels high or not and by using articulating paper. Any high spots should be adjusted and the restoration polished (see section on polishing).

Treatment of posterior proximal lesions

Caries on the proximal surfaces of posterior teeth occurs because plaque can collect cervical to the contact area, resulting in a stagnation area (or plaque trap). The diagnosis of proximal caries requires careful clinical examination of the marginal ridges; this area may appear darker or more opaque than surrounding tooth tissue.

Bitewing radiographs are essential for the diagnosis and assessment of posterior proximal lesions. If the lesion is confined to enamel, as assessed radiographically, then it may be possible to arrest, or even reverse, the progress of the caries. Appropriate dietary advice and interdental cleaning instruction should be given and fluoride, either as an operator-applied varnish or in toothpaste, should be used.

If the lesion has cavitated and spread into dentine then operative intervention will normally be necessary to restore the surface integrity of the tooth. Access to caries on the posterior proximal surfaces may be gained in a number of ways:

■ Through the marginal ridge from the occlusal aspect. The most common technique to gain access to the caries is through the marginal ridge from the occlusal surface of the tooth and this technique will be described in detail.

■ From the occlusal surface (tunnel preparation), preserving the marginal ridge (Fig. 3). The tunnel preparation is difficult to execute unless there is a pre-existing occlusal restoration which is removed and access to the proximal caries can be gained from the occlusal cavity, without removing the marginal ridge. This technique is not suitable if there is extensive proximal caries as the marginal ridge will collapse. The main difference between this method is that during preparation contact point is preserved, access to the carious cavity is created from the occlusal surface like a tunnel. This method helps to preserve the most of unmodified tissue. This preparation is recommended to be carried out with turbine handpieces, round-shaped burs with the simultaneous cooling of water.

■ From the buccal (or lingual) aspect. This technique is only suitable where there is no risk of marginal ridge collapse and in situations where resin composite can be used as the restorative material.

■ Directly, if the adjacent tooth is absent.

 

 

Technique for posterior proximal restorations through the marginal ridge

■ Local analgesia is usually required.

■ Check occlusion and mark occlusal stops with articulating paper.

■ Ensure effective isolation.

■ Protect adjacent teeth: some operators like to place a matrix band on the adjacent tooth to prevent damage of this tooth during preparation of the box component of the cavity. This is no guarantee that the tooth will not be damaged and care should always be taken in the preparation of proximal cavities to protect the adjacent tooth.

■ Gaining access: access is gained through the marginal ridge using a pear-shaped diamond or tungsten carbide bur in a high-speed handpiece. Start slightly away from the marginal ridge and direct the bur downwards and towards the contact area. The bur should drop down into the caries. Try to leave a thin wall of proximal enamel to protect the adjacent tooth. This can be removed subsequently with gingival margin trimmers. This creates a shape described as a box but it should not be square: it should have round internal line angles and should be wider cervically than occlusally. If there is also occlusal caries then the cavity should be extended into the occlusal fissure (Fig. 4). If there is no occlusal caries then the cavity does not need to extend into the fissure (Fig. 5).

 

■ Caries removal: caries should be removed with a round stainless steel or tungsten carbide bur in the slow-speed handpiece. Remove the caries from the enamel dentine junction first before moving to the axial wall (and pulpal floor if the cavity has been extended into the occlusal fissure). An excavator may also be used to remove soft dentine caries. This should result in a cavity that clears the contact area cervically and is wider cervically than occlusally.

■ Retentive features: additional retentive features are only necessary if amalgam is to be used as the restorative material. If the cavity has extended into the occlusal fissure then this will act as a key or dovetail to retain the amalgam and prevent its displacement. If there is no occlusal key and amalgam is to be used, then small grooves should be cut at the junctions between the axial wall and the buccal and lingual walls.

■ Lining: if the cavity is suitably deep to require lining then this should be placed on the pulpal floor and on the axial wall (Fig. 6).

 

■ Matrix band: a matrix band is placed to help retain the restorative material during placement, to give shape to the proximal surface of the restoration and to allow close adaptation of the restorative material to the cavity. The band should be closely adapted to the cervical margin and should be burnished against the adjacent tooth to help formation of a good contact. There are many types of matrix bands and holders, but commonly used ones are:

Ø     Siqveland: this system uses a straight band and the holder and band are removed from the tooth simultaneously. This can sometimes result in removal of part of the newly packed amalgam.

Ø     Tofflemire: this system has the advantage that the holder is removed before the band and this may  prevent removal of the restoration with the band.

Ø     Circumferential: a number of systems exist that have no retainer/holder. The band is tightened by  a spring mechanism.

Ø     Ivory: this has a holder which engages into a selection of holes in a metal band. The metal band replaces only one proximal wall and therefore  cannot be used for cavities involving both proximal walls.

■ Wedge: the next stage is to place a wedge at the cervical margin of the band, normally from the buccal aspect. The wedge has several functions:

Ø     It separates the teeth slightly so that when the matrix band is removed there is no space between the adjacent teeth and a tight contact is formed. Wooden wedges swell slightly by absorbing moisture in the mouth so are preferable to plastic wedges.

Ø     It prevents excess material at the cervical area of the cavity forming a ledge.

Ø     It shapes the band at the cervical margin of the tooth.

Ø     It can help retain the band in place.

■ Material placement (amalgam): once the amalgam has been mixed, it starts to set so the operator must work quickly to pack and carve the restoration. The amalgam is transferred in increments from the amalgam carrier to the deepest area of cavity – usually the base of the box. It is condensed first with the wider end of the amalgam condenser and then with the narrower end. It is important to condense the amalgam well to adapt the material to the cavity walls and to reduce porosity. Place the next increment, condense and  continue until the cavity is over-filled. The cavity is over-filled to allow removal of the weak, mercury-rich (γ2) layer that is at the surface of a well-condensed amalgam. Run a straight probe around the inside surface of the matrix band to remove gross excess of amalgam and to start to shape the marginal ridge. Carefully remove the wedge, matrix retainer and band. Check the cervical margin for excess amalgam with a straight probe and remove any excess, either with the probe or an amalgam carving instrument, such as a ½ Hollenbach. Use an instrument designed for carving as it will cut through the amalgam, rather than smearing it (as would be the result if a flat plastic were used).

Using the tooth as a guide, rest the blade of the carver against the tooth and carve through the amalgam to recreate the cuspal shapes of the tooth. Check that the marginal ridge is a similar height to that of the adjacent tooth. Check the occlusion by asking the patient to close gently on the restoration. Listen for the sound of the teeth coming together and any impact on the amalgam. Look for any high spots and adjust. Should the amalgam fracture at this stage, it is better to remove the partially set material and start again, rather than try to add to the fractured amalgam.

■ Material placement (resin composite): dental adhesive should be applied to all the surfaces and margins of the cavity. The first increment of restorative material may be placed either at the base of the box or to form the proximal wall. Light cure for the recommended time, then place the next increment, ensuring that this increment only touches either the buccal or lingual wall but not both. Light cure and continue with incremental packing and curing. Carefully shape the marginal ridge by running a straight probe round the inside of the matrix band and finally recreate the cusp shapes to give the correct occlusal contour. Remove the wedge, matrix holder and band and check cervically for excess material. Check the occlusion by asking the patient and by the use of articulating paper. Shape and polish as required.

Treatment of anterior proximal lesions

Caries occurs on the anterior proximal surfaces owing to the accumulation of plaque gingival to the contact area (Fig. 7). Detection of these lesions is by direct vision or by transillumination: reflected light in the mouth mirror.

The technique for treatment of these lesions is as  follows:

■ Gaining access: access to the lesion should be from the palatal or lingual aspect if at all possible, as this will allow preservation of the labial enamel. A small round diamond in the high-speed handpiece is used to drop into the caries.

■ Removal of caries: a round bur in the slow-speed handpiece is used to remove the caries, trying to  preserve the labial enamel. Additional preparation to create a retentive cavity will probably not be necessary as the shape of the carious lesion will result in an undercut cavity. With adhesive restorations, an undercut cavity is unnecessary and amalgam restorations are contraindicated in anterior proximal cavities primarily because of their poor appearance.

■ Lining: a lining should be placed as required. Beware that calcium hydroxide lining materials are opaque and can look unsightly through thin labial enamel.

■ Matrix: a clear cellulose matrix strip should be placed before use of the dental adhesive to prevent bonding the adjacent teeth together. The strip should be placed so that it is cervical to the gingival margin of the cavity.

■ Dental adhesive: apply the adhesive to the cavity and the cavity margins.

■ Material placement: place the resin composite in the cavity in small increments and light cure. After the final increment has been placed, pull the matrix band tight cervically to prevent formation of a ledge, and light cure.

■ Finishing: check the occlusion as before and finish as required.

Treatment of incisal edge lesions

Incisal edge lesions are the result of trauma, failure of a proximal restoration or extensive proximal caries.

The technique for treatment of incisal edge lesions is as follows:

■ Access: access to the lesion is not normally difficult;  the difficulty is creating good bonding potential. A labial bevel or chamfer will increase the area of tooth tissue for bonding and will improve the appearance of the final restoration as it will allow the composite to merge gradually with the tooth, rather than having a butt joint. Palatally, a small shoulder will increase the strength of the restoration in this area of occlusal loading. The lack of cavity walls has the advantage of reduced stress from polymerisation shrinkage.

■ Lining: in trauma cases, direct or indirect pulp capping with setting calcium hydroxide may be necessary.

■ Composite placement: composite can be built up free-hand or by using a matrix. To achieve optimal appearance, composites of different opacity, such as ‘dentine’, ‘body’, ‘enamel’ and translucent, should be built up in incremental layers. The types of available matrices are:

Ø  Custom-made: an impression of the palatal aspect of an intact tooth can be used to aid formation of this aspect of the final restoration. To achieve an intact tooth, a temporary restoration can be placed, or a laboratory wax-up used.

Ø  Preformed: the main types used are clear cellulose strips, incisal corners and complete crown forms.

■ Shaping and finishing: the adjacent teeth may be used as a guide to the shape of the final restoration. Care should be takeot to damage the remaining tooth  tissue in the polishing of incisal edge restorations when it may be difficult to distinguish between tooth and restoration.

Treatment of cervical lesions

Lesions occur on the smooth, cervical surfaces owing to enamel and root caries, erosion and abrasion. The method of treatment is as follows:

■ Access: this is not normally difficult unless the lesion is on the lingual surface of a molar tooth. The amount of cavity preparation depends on the cause of the lesion: abrasion and erosion lesions may only require the cutting of a bevel and cleaning of the cavity with a pumice and water paste, whereas carious cavities may require access with a high-speed round diamond bur and caries removal with an excavator or round stainless steel slow-speed bur.

■ Material placement: resin composite is generally the material of choice for such restorations but amalgam may be placed in posterior teeth; in difficult, subgingival cavities glass ionomer-based materials may be used. Glass ionomers should be protected with either varnish or an unfilled resin for the first few days after placement to protect them from moisture contamination. The material may be shaped free-hand or with a matrix.

Preparation of carious cavities for modern composite materials placement.

Preparation of carious cavities is usually done very carefully, with complete removal of all softened tissue of enamel and dentin.

One of the advantages of light-hardening composite materials is the ability of sparing preparation, when it is not required to form box-like cavities, and there is no need to create ledges and grooves to increase retention of material.

For opposite, it is recommended to smooth sharp angles of the carious cavity and make round form of the carious cavity, because in these areas it can be threaten of the filling material abruption during its polymerization, if the elasticity of the applied adhesive systems is not high enough. Complete removal of pigmented areas of dental hard tissue is preferable, pigmented areas may delay the light during the polymerization and lead to incomplete hardening of the material in these areas. However, you must create enamel bevel at an angle of 45⁰, around the edge of the cavity to increase the adhesion and to mask the  line of  transition “enamel–composite material”. It is recommended to prepare hard dental tissues with the help of turbine handpieces, with the obligatory cooling – of the burs  with a cold water. This prevents possible overheating of the pulp, dental hard tissues and untimely worn of burs.

 

Initial view of carious cavity                               Carious cavity after preparation

Enamel after etching (white, porous)               Restored carious cavity with composite material

 

It is apparent from the foregoing that caries is now recognised as a disease and therefore a revised approach to its treatment and prevention is required from that suggested by GV Black. His approach was necessarily limited by both knowledge and equipment but at the present state of science, the profession must adopt an entirely new set of principals.

Having decided that caries is essentially a disease of bacterial origin then it is mandatory that we think in terms of early recognition of its presence in the mouth, followed by elimination of the active disease, prior to undertaking moves to repair the damage that it has caused. In undertaking repair it is imperative that remaining tooth structure be preserved and protected as far as possible. Remineralisation is possible on any surface that remains smooth and not cavitated so repair or replacement of damaged tooth structure should aim at redevelopment of a smooth surface only, thus eliminating the potential for further plaque accumulation. Modern methods for removal of diseased tooth structure should be used primarily to enhance patient comfort but at the same time undue loss of sound tooth structure must be avoided. Whilst precise geometric cavity designs are no longer to be contemplated any sacrifice of sound tooth structure is to be deprecated. Good visibility and a high level of tactile sense are useful tools in limiting the extent of surgical removal of tooth structure. 

 

Information was prepared by Levkiv M.O.