Discuss the advantages and disadvantages of indirect restorative materials.

Common indirect dental restorations include crowns, bridges, veneers, dentures, inlays and onlays. Direct tooth restorations are those that can be done in one procedure in one dentist office visit.
Advantages
1. Improved physical properties: A wide variety of high-strength tooth-coloured restorative materials, including laboratory-processed and computer-milled ceramics, can be used with indirect techniques. These have better physical properties than direct composite materials because they are fabricated under relatively ideal laboratory conditions. For CAD/CAM restorations, although some are fabricated chairside, the materials themselves are manufactured under nearly ideal industrial conditions.
2. Variety of materials and techniques: Indirect tooth-coloured restorations can be fabricated with ceramics using traditional laboratory processes or using chairside or laboratory CAD/CAM methods.
3. Wear resistance: Ceramic restorations are more wear resistant than direct composite restorations, an especially important factor when restoring large occlusal areas of posterior teeth.
4. Reduced polymerization shrinkage: Polymerization shrinkage and its resulting stresses are a major shortcoming of direct composite restorations. With indirect techniques, the bulk of the preparation is filled with the indirect tooth-coloured restoration, and stresses are reduced because little resin cement is used during cementation. Although shrinkage of resin materials in thin bonded layers can produce relatively high stress, clinical studies indicate ceramic inlays and onlays have better marginal adaptation, anatomic form, colour match, and overall survival rates than do direct composite restorations.
5. Support of remaining tooth structure: Teeth weakened by caries, trauma, or preparation can be strengthened by adhesively bonding indirect tooth-coloured restorations. The reduced polymerization shrinkage stress associated with the indirect technique also is desirable when restoring such weakened teeth.
6. More precise control of contours and contacts: Indirect techniques usually provide better contours (especially proximal contours) and occlusal contacts than do direct restorations because of the improved access and visibility outside the mouth.
7. Biocompatibility and good tissue response: Ceramics are considered chemically inert materials with excellent biocompatibility and soft tissue response. The pulpal biocompatibility of the indirect techniques is related more to the resin cements than to the ceramic materials used.
8. Increased auxiliary support: Most indirect techniques allow the fabrication of the restoration to be delegated totally or partially to the dental laboratory. Such delegation allows for more efficient use of the dentist’s time.
Disadvantages
1. Increased cost and time: Most indirect techniques, except for chairside CAD/CAM methods, require two patient appointments plus fabrication of a provisional restoration. These factors, along with laboratory fees, contribute to the higher cost of indirect restorations in comparison with direct restorations. Although indirect tooth-coloured inlays and onlays are more expensive than amalgam or direct composite restorations, they are usually less costly than more invasive aesthetic alternatives such as all-ceramic or porcelain-fused-to-metal (PFM) crowns.
2. Technique sensitivity: Restorations made using indirect techniques require a high level of operator skill. A devotion to excellence is necessary during preparation, impression, try-in, bonding, and finishing the restoration.
3. Difficult try-in and delivery: Indirect composite restorations can be polished intraorally using the same instruments and materials used to polish direct composites, although access to some marginal areas can be difficult. Ceramics are more difficult to polish because of potential resin-filled marginal gaps and the hardness of the ceramic surfaces.
4. Brittleness of ceramics: A ceramic restoration can fracture if the preparation does not provide adequate thickness to resist occlusal forces or if the restoration is not appropriately supported by the resin cement and the preparation. With weaker ceramic materials, fractures can occur even during try-in and bonding procedures.
5. Wear of opposing dentition and restorations: Some ceramic materials can cause excessive wear of opposing enamel or restorations. Improvements in materials have reduced this problem, but ceramics, particularly if rough and unpolished, can wear opposing teeth and restorations.
6. Short clinical track record: Compared with traditional methods such as cast gold or even amalgam restorations, bonded indirect tooth-coloured restorations have a relatively short record of clinical service. They have become popular only in recent years, and relatively few controlled clinical trials are available, although these are increasing in number.
7. Low potential for repair: When a partial fracture occurs in a ceramic inlay or onlay, repair is usually not a definitive treatment. The actual procedure (mechanical roughening, etching with hydrofluoric [HF] acid, and application of a silane coupling agent before restoring with adhesive and composite) is relatively simple. However, because many ceramic inlays and onlays are indicated in areas where occlusal wear, aesthetics, and fracture resistance are important, composite repairs frequently are not appropriate or successful.

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Discuss the advantages and disadvantages of indirect restorative materials.

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