Preparation.docx

1. M4 TENTANG PREPARASI Preparation Site 1 – Size 0 (1.0): A pit or fissure on any tooth or an erosion lesion on an incisal edge that is regarded as suspicious and must be recorded and kept under obervation. It is virtually impossible to completely clean a fissure system once a tooth has erupted into the oral environment. In many cases it will be desirable to mechanically clean the fissure even though this involves a limited sacrifice of some enamel. There is a variety of methods to achieve this with minimal reduction of tooth structure. These variations are discussed in Chapter 8 and include a very fine tapered diamond bur, a small tungsten carbide bur, a laser or air abrasion. Whichever preparation method is applied, preservation of natural tooth structure is of paramount importance, along with long‐term adhesion of the restorative material. A diamond or tungsten carbide bur offers the simplest and most effective method mainly because the operator retains some degree of both visual and tactile sense and is therefore less likely to over‐extend the preparation. As the preparation is primarily in enamel, local anaesthesia is not generally required. The tungsten carbide bur with a short head is less desirable because it is easy to lose sight of the head and therefore lose control of the depth of penetration. Having gained access to a carious area, it is only necessary to develop clean walls around the lesion to ensure proper adhesion. Leave the floor untouched even though it may be demineralized. Once it is sealed and isolated, it will remineralize and heal [1].

Site 1 – Size 2, designated 1.2 Preparation This may be a new cavity in which caries has progressed some distance before the patient presented for treatment. Generally only one part of the fissure system will be involved and remaining fissures can be sealed without further exploration [2] with either glass‐ionomer cement or composite resin (Figures 7.7–7.10). Remove any old restorations using a tungsten carbide bur at ultra‐high speed under water spray, taking care not to extend the cavity any further than necessary. A tapered or parallel sided diamond cylinder at intermediate high speed under air/ water spray is then preferred to explore the extent of the problem. Small round burs can be used to remove remaining caries from the walls but removal of all affected dentine from the floor is contraindicated. Occlusal enamel should be retained, even though it is unsupported, providing the margins are sound and there are no microcracks [3]. A base of glass‐ionomer cement will provide considerable support and reinforcement to undermined enamel.

Site 1 – Size 3, designated 1.3 When the cavity reaches this size, there will be extensive undermining or breakdown of at least one cusp with the possibility of a split developing at the base [4]. It may be a new lesion involving almost the entire dentine of the crown or it may be an old restoration which has become recurrent [5] (Figures 7.11–7.14). Preparation Tungsten carbide burs should be used at ultra‐high speed under air/water spray to remove any old remaining restorative material, then use a small diamond cylinder to open the enamel to determine

the extent of the problem. Round burs can be used periphery to ensure a sound ion exchange adhesion. Be careful not to remove all affected dentine on the floor of the cavity to avoid the problems arising from pulp exposure. If it is a new cavity, resulting from active caries, it may be desirable to carry out an indirect pulp capping, as described in Chapter 12. Open the cavity with a small diamond cylinder, only as far as required, to gain access to the infected dentine. Clean the walls around the entire periphery using a round bur of appropriate size to ensure that the margin is placed entirely in sound enamel and dentine. This is essential to achieve a complete seal. Leave affected dentine on the floor because it may remineralize and it is better, at this time, not to irritate the pulp any more than essential. Place an indirect pulp cap material over a near exposure if required. If the patient is highly caries‐active, it may be desirable to place a temporary restoration to allow the pulp to heal. Seal the cavity with glass‐ionomer cement for a minimum of three weeks and then reassess the cavity design when preparing the final restoration. At that stage, carefully check all remaining cusps to determine the need to protect them from occlusal load. If a cusp has a column of sound dentine providing adequate support for the enamel, and there is more than one half of the medial facing cuspal incline still present, it can remain standing without protection. If a cusp is undermined, and the medial cuspal incline is subject to occlusal load, it requires protection, or it will develop a split at the base. The cusp will need to be bevelled outwards to reduce load during lateral excursions regardless of the restorative material. If amalgam is the material of choice, it may be necessary to include retentive elements in the cavity design such as grooves and ditches placed in the remaining sound dentine to ensure that the restoration is soundly locked in. If the adhesive materials are to be used, the cusp still requires to be bevelled and the restorative material will need to be well constructed to take the load and relieve the cusp.

Site 1 – Size 4, designated 1.4 Preparation This will be an extensive cavity and at this size there will have been a further breakdown with complete loss of one or more cusps and full restoration with a plastic restorative material will be complex. Amalgam could be used for a reasonably satisfactory restoration but generally an indirect extra‐coronal restoration such as a full or three‐quarter crown will be required subsequently to completely restore coronal anatomy, occlusion and proximal contacts preparation should be carried out as described above for a cavity classified as Site 1, Size 3. Old restorative material is best removed using tungsten carbide burs at ultra‐high speed under air/water spray. Use a diamond cylinder at intermediate high speed to enter enamel, and round burs to remove the infected dentine. Make sure the walls are clean enough to accept the ion exchange adhesion but leave affected dentine on the floor to avoid undue irritation to the pulp. Develop auxiliary retention with a small tapered steel fissure bur in remaining dentine where available. If the caries rate is high, it may be desirable to carry out the indirect pulp‐cap technique as described above.

2. M4 TENTANG INSTRUMEN RESTORASI DAN PREPARASI Rotary Cutting Instruments Selection of burs In general, rotary cutting instruments will remove tooth structure either by chipping it away or else by grinding [1, 2]. There are essentially three types of bur designed for cavity preparation although

there are many variations for polishing, contouring, etc. This discussion will be confined to those related to preparation of caries lesions only. Steel burs These were originally used when rotary cutting instruments were developed well over one hundred years ago [3]. Initially only foot drills were available with speeds of about 50–500 rpm. Electric motors followed, allowing speeds up to 5000 rpm and they remain valuable for the removal of caries and the development of retentive elements in dentine. Each bur generally has eight blades and some of them have a positive rake angle to facilitate the cutting of the dentine or the removal of caries (Figure 8.3). This, however, makes them relatively fragile and subject to chipping along the leading edge and they should not be expected to have a long life in normal practice. In fact, single use is recommended. The use of an air/water spray during cutting with steel burs will increase efficiency but it is not essential. Generally the shanks are designed for latch‐type handpieces but some manufacturers now make friction grip handpiece heads to hold these burs and these help to maintain concentricity and thereby reduce vibration. Any bur rotating at low speeds will deliver a rather high annoyance factor to the patient and a good tactile sense is essential for the operator to avoid over‐cutting. Burs must always be in good condition and visibility must be excellent at all times. Tungsten carbide burs Following the development of higher speed motors and handpieces there was a need to provide stronger burs to withstand the heavier stresses involved and to lengthen their useful life. Tungsten carbide burs were designed almost exclusively for friction grip handpieces because concentricity is essential and they only cut efficiently at greatly increased speeds (Figure 8.4). In fact they do not begin to reach effective cutting capacity until 100,000 rpm, and are best used at speeds beyond 300,000rpm. The efficiency of these instruments for removing particles of enamel or dentine depends on the number of blades, the rake angle of the blades and other variations in the design. Blades which twist around the shank of the bur will remove debris more readily and blades which are cross‐cut are more efficient still. Burs with eight blades or fewer are designed for rough or gross cutting and the greater the number of blades, the finer the surface and the smoother the cut. Tungsten carbide burs with 30 blades or more are used for polishing. The usual bur has six blades and a negative rake angle to provide better support for the cutting edge. For the same reason many have a radial clearance as well. They cut metal and dentine well but are prone to produce microcracks in enamel, thus weakening the cavosurface margin. It is essential that tungsten carbide burs be used at speeds above 100,000 rpm. Air/water spray is mandatory for the removal of debris and temperature control and they must be mounted in a friction grip cartridge for concentricity. Probably only a new bur will be truly concentric because any loss of a blade, or even a section of a blade, will alter the balance so that only every third or fourth blade will actually contact the tooth. This means that the clinical life is generally quite short. The annoyance factor with a new bur at high linear surface speed is very low but a lack of concentricity will be immediately discernible to the patient. Diamond burs or stones Diamond burs will grind away tooth structure and they are available in a range of particle size from about 150 micron (μ) down to 5μ. Diamonds with a particle size of 150μ are extremely coarse with a high annoyance factor so the regular 80μ particles are the usual selection for basic cavity preparation. Finer diamonds with particle sizes in the 25μ range are recommended for finishing all

margins where adhesive restorative materials are to be placed, while polishing procedures can be carried out with particles down to 5μ. In recent times there have been considerable improvements in the methods of embedding the diamond particles in the metal of the bur head so they last longer and there is a far better distribution of particle size. The particles are attached to the shank of the bur through either a galvanic metal bond or a sintering process and the quality and efficiency of the bur are dependent upon the efficiency of attachment of the particles to the bur head as well as the clearance of the shavings. Air/water spray is mandatory to enhance clearance and to control heat development, which will be greater as the particle size reduces and clearance is slowed down. Diamond burs will cut efficiently over a wide range of speeds, although logically the annoyance factor will be least with the finer grain size if lower speeds are to be utilized.

3. M4 TENTANG BAHAN RESTORASI Glass-Ionomer Restorative Materials Advantages Glass-ionomers are water-based cements that are stable in the oral environment. They are bioactive, so they are capable of exchanging calcium, strontium, fluoride and phosphate ions with tooth structure to develop and maintain an intimate physico-chemical union. They are of low solubility when used properly. The materials contain fluoride which is released into the surrounding tooth structure after placement. There is a strong fluoride release initially that reduces over the first two months. Release has been shown still to be present over at least seven years [2]. The fluoride content can be continually recharged from topical applications from many sources including toothpaste and professionally applied fluids or gels. As a result, the material appears to have a strong resistance to the development of recurrent caries at the interface with the tooth structure. The intimacy of the bond to enamel and dentine promotes remineralization of both, and there is an inhibitory effect from the fluoride release on bacteria in the biofilm. The acid content of the glassionomer cement allows surface etching and adhesion to both dentine and enamel. The bond is weaker than the bond of modern composite resins to enamel, but the material performs well clinically, in terms of adhesion. The intimate and strong bond to dentine seals well, preventing fluid flow through the dentine tubules, thereby reducing or eliminating post-operative sensitivity. Glassionomer restorative cements have an acceptable degree of translucency and colour matching. Also, because of their adhesive properties, there is no need to modify the cavity design to develop mechanical interlocks for retention, so they are very conservative of natural tooth structure. The restorative cements are available in both a light-activated form, also known as resin-modified or dual cure, as well as the original chemically activated or auto-cure system [3]. The dualcure mechanism was developed through the addition of resins, including HEMA and photoinitiators. The main advantage with these is improved resistance to water contamination immediately after light initiation. The original acid/base reaction, which allows the development of adhesion to the tooth, and is therefore the key to the glass-ionomer system, is still present but is protected by the umbrella-like presence of the dual-cure resins. Dual-cure resins have been shown to decrease, but not negate, the fluoride release of the glass-ionomer system. They have an elastic modulus similar to dentine and as such are ideal for the restoration of both carious and non-carious cervical lesions. Disadvantages The main limitation with a glass-ionomer cement is a relatively low fracture and abrasion resistance. It cannot be used alone to withstand heavy occlusal load but will last well if supported by

surrounding tooth structure. Glass-ionomer restoratives are therefore not suitable to rebuild marginal ridges or incisal corners [4]. Solubility is low and improves over time due to the long-term setting mechanism, but early exposure to water contamination will result in loss of physical properties. Effective surface sealing with a resin-based coating immediately after placement and the initial set will overcome this risk. On occasions, translucency in some chemically activated or autocure materials may not be sufficient for colour matching, and lamination with composite resin may be required for a satisfactory aesthetic result. The creation of enduring glass-ionomer cement restorations requires a careful clinical technique, particularly relative to moisture control both during and after placement. Good moisture control using a rubber dam increases the chances of clinical success; at the time of placement, dentine should be moist, but should not be frankly wet or contaminated with saliva. Effective surface sealing with a bonding resin or similar material immediately after initial set has proven to be very beneficial for the development of good aesthetics and long-term surface integrity. A further important caution is that, as a water-based material, glassionomer cements remain at risk of dehydration if aggressively dried, particularly in the early hours after placement. They may also dehydrate and suffer surface disintegration over time in patients with very low saliva flow. For those with Sjögren’s Syndrome, or similar salivary incompetence, it may be necessary to confine the use of glass-ionomers to replacement of lost dentine and to laminate over it with a resin-based material.

Resin-Based Composite Advantages Resin-based composite restorations can have excellent aesthetics and can be built in multiple layers and shades. When the resin composite is placed incrementally, and properly lightactivated at each stage, variation in both colour and translucency can be incorporated, and anatomical form reproduced reasonably accurately. Significant development has been carried out in recent years on the filler particles incorporated within the resin and there is considerable variation between the products on the market [5]. Physical properties and translucency will be affected by the filler particle size and filler particle loading. This affects the material’s ability to be shaped and manipulated as well as the material’s ability to retain a smooth polished surface [6]. Properly placed, the physical properties of resin composite are sufficient to withstand moderate occlusal load throughout the mouth and the wear factor of the more heavily filled composites is sufficient for these restorations [7]. Relative to ceramic restorations, resin composite is inexpensive, but it has a potentially shorter potential lifespan [8, 9]. It is relatively simple to develop a micro-mechanical union between enamel and composite resins through applying an acidic etchant for a brief period. This is the strongest adhesion available in the oral cavity. Bonding to dentine is more difficult due both to dentinal fluid and a high collagen content, so different strategies must be used to achieve adhesion to that tissue. Modern dentine bonding agents require that the dentine be maintained moist, avoiding desication and therefore reducing the risk of post-operative sensitivity that can be severe. Dentine bonding agents utilize strategies that promote adhesion to the collagen in dentine through the addition of hydroxyethyl methacrylate (HEMA) in a hydrophilic carrier, such as ethanol or acetone, to facilitate its movement into the moist tubule. Disadvantages Placement techniques are extremely technique-sensitive and require a high degree of clinical skill. Alhough dentine bonding requires moist dentine, the bonding agent must not be applied in a frankly

wet or saliva-soaked environment. Resin composites, like all polymerizing plastics, contract during setting. The process of shrinkage has the net effect of producing stress at the adhesive interface and, if improperly placed, can pull the composite resin away from the cavity margins. This will lead to microleakage with the risk of pulpal inflammation and death. Careful incremental placement of the material will control the direction of shrinkage and minimize the total amount to within range of 1– 2%. However, this may still be sufficient to place considerable stress on the bond of the restoration to both the tooth structure and a cement base [10]. Improper placement of resin composites can allow fluid movement through the margins leading to post-operative sensitivity.

Amalgam Advantages Over many years, particularly in small restorations, amalgam has been shown to have a very satisfactory history of longevity. It is relatively easy to handle through standardized methods and placement techniques have become very routine. Amalgam is tolerant of less than ideal placement techniques, although over-contour, particularly in relation to the gingival tissues, can pose a challenge through plaque retention. Properly placed, amalgam has physical properties which are sufficient to withstand normal occlusal stresses. It is a very economical material and therefore costeffective. Following placement, it will corrode quite rapidly in the oral environment and the corrosion products will seal the margins against microleakage within the first few days after placement [12]. This, therefore, makes it highly resistant to recurrent caries [13]. Disadvantages The main disadvantage of amalgam is that it is aesthetically undesirable. The material itself is initially silver then declining to a dull grey in colour. As it corrodes, it darkens in itself and may also release metallic ions into the surrounding dentine, leading to a blue or grey discoloration in the remaining tooth structure. Corrosion is therefore both an advantage and a disadvantage. In modern formulations with a high copper content, the corrosion potential has been reduced sufficiently to minimize the colour disadvantages although there is still enough corrosion product available to seal the margins against microleakage. A second disadvantage is that it is generally necessary to extend the cavity beyond the initial caries lesion to allow for correct retention of the restoration. Historically, it was recommended that the margins of amalgam restorations be placed in areas where they could be regularly cleaned of dental plaque. This is no longer considered necessary, allowing smaller and less destructive restorations. However, even if the lesion is small, it is necessary to develop mechanical interlocking retention. This may lead to sacrifice of otherwise sound tooth structure so there is a minimum cavity outline regardless of the extent of the initial lesion. For restoration of the more extensive lesion, amalgam can be regarded as having very desirable physical properties although it does require a degree of skill in re-creating the anatomy of the original crown.