Indirect Tooth Colored Restorations PDF

Indirect tooth colored restorations Indirect restorations are types of restorations that are made on a replica of the prepared tooth in a dental laboratory or by using computer- aided design /computer- assisted manufacturing (CAD/CAM) either chairside or in the dental laboratory. Inlay: int...

Indirect tooth colored restorations Indirect restorations are types of restorations that are made on a replica of the prepared tooth in a dental laboratory or by using computer- aided design /computer- assisted manufacturing (CAD/CAM) either chairside or in the dental laboratory. Inlay: intra-coronal restoration made outside of a tooth to correspond to the form of the prepared cavity, which is retained by adhesive means. Onlay: a partial-coverage restoration that restores one or more cusps and adjoining occlusal surface and is retained by adhesive means. Occlusal overlay: a partial-coverage restoration that restores the whole occlusal surface and is retained by adhesive means. Occlusal veneer: an occlusal ceramic shell to cover the occlusal table without axial cavity preparation. Endocrowns are intra pulpal overlays that have an adjunctive retention from the pulp chamber of root canal treated molars. Vonlay: a partial-coverage restoration that restores the whole occlusal surface, extended to the buccal surface and is retained by adhesive means. Indications: 1. Extensively damaged teeth: where the direct restorations cannot restore contour, contact and occlusion properly. (Difficulty in obtaining an acceptable contour, contact point and occlusion on a directly placed restoration. This usually occurred with restoring large Class I and II defects or replacement of large compromised existing restorations, especially those that are wide facio-lingually or require cusp coverage). 2. Uncooperative patient who can not be subjected to prolonged chair side time. 3. Deeply seated sub-gingival cavities, where proper finishing and polishing of direct restorations is difficult. N.B. indirect esthetic restorations are considered contraindicated in cases with deep subgingival margins if the moisture can not be controlled. In such cases deep marginal elevation and/ or crown lengthening could be options to expose the gingival margins. Re-evaluation of the case should be then performed to decide whether to select direct or indirect restorations based on the other factors. 4. Solving of occlusal problems such as severe attrition with decreased |Page1  vertical dimension. 5. Correction of esthetic derangement, such as excessive discoloration caused by fluorosis or tetracycline. 6. Lack of accessibility. 7. Solving some problems of direct restorations. Contraindications: 1. Para functional occlusal forces: Ceramic restorations can fracture when they lack sufficient thickness or are subjected to excessive occlusal stress, as in patients who have bruxing or clenching habits. N.B. Heavy wear facets or a lack of occlusal enamel are good indicators of bruxing and clenching habits. 2. Inability to maintain a dry field: adhesive techniques require near perfect moisture control to ensure successful long-term clinical results. 3. Very poor oral hygiene. 4. Deep subgingival preparations: Although this is not an absolute contraindication, preparations with deep subgingival margins generally should be avoided. These margins are difficult to record with an elastomeric or even a digital impression and are difficult to evaluate and finish. Additionally, dentin bond strength at gingival floors are not particularly good, so bonding to enamel margins is greatly preferred, especially along gingival margins of proximal boxes. Supragingival margins facilitate impression making, definitive restoration placement, and detection of secondary caries. subgingival restorations are associated with higher levels of gingival bleeding, attachment loss, and gingival recession than supragingival restorations. Therefore, in all cases where rubber dam cannot be adequately placed, surgical crown lengthening or orthodontic extrusion should be considered. Otherwise, traditionally cemented restorations are preferable to the use of adhesive procedures. 4. Insufficient or poor quality of the remaining tooth structure available for bonding, example; insufficient enamel margins, hypoplastic or demineralized enamel. Advantages: Indirect tooth-colored restorations have the following additional advantages over direct restorations: 1. Improved physical properties: A wide variety of high strength tooth-colored restorative materials, including, laboratory-processed and computer-milled ceramics can be used with indirect techniques. Also, laboratory-processed composite resin restorations have higher physical and mechanical properties than direct composite resin. |Page2 2. Wear resistance: Indirect Ceramic and composite resin restorations are more wear resistant than direct composite restorations, an especially important factor when restoring large occlusal areas of posterior teeth. 3. Indirect composite resin restorations have less 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-colored restoration, and stresses are reduced because little resin cement is used during cementation. 4. Support of remaining tooth structure: Teeth weakened by caries, trauma, or preparation can be strengthened by adhesively bonding indirect tooth-colored restorations. The reduced polymerization shrinkage stress associated with the indirect technique also is desirable when restoring such weakened teeth. 5. 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. 6. Biocompatibility and good tissue response: Ceramics are considered chemically inert materials with excellent biocompatibility and soft tissue response. However, the pulpal biocompatibility of the indirect techniques is related more to the resin cements than to the ceramic materials used. 7. 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. 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 intra-orally 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. With weaker ceramic materials, fractures can occur even during try-in and bonding procedures. |Page3  5. 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. Classifications of indirect restorations: I. According to the material of construction: a. Metallic b. Non-metallic (Cermaic & Resin composite) II. According to the technique of fabrication: a. Indirect fabrication of indirect restoration: the restoration is entirely fabricated, adjusted and finished on the model and then recemented intra-orally. b. Indirect-direct fabrication of indirect restoration: the restoration is fabricated on the model, but checked and verified intra-orally for checking the fitting and the marginal accuracy. If any corrections are required the restoration has to be readjusted on the model before heat treatment finishing and polishing procedures. c. Direct fabrication of indirect restoration: the restoration is fabricated intra-orally inside the prepared cavity and then transferred to the laboratory for heat treatments and finishing prior to its cementation. Guidelines for indirect tooth colored cavity preparation 1. The patient is anesthetized and the area is isolated, preferably using a rubber dam. 2. The compromised restoration (if present) is completely removed, and all caries is excavated. During preparation, stains on the external walls, such as those often left by corrosion products of old amalgam restorations, should be removed. Such stains could appear as black or gray lines at the margin after cementation. (This does not apply to stained but non-carious dentin on pulpal and axial walls that should be left). 3. Preparations for indirect tooth-colored inlays and onlays are designed to provide adequate thickness for the restorative material and a passive insertion pattern. ✓ The occlusal portion of the preparation should be 2 mm deep. ✓ Many failures of ceramic inlays and onlays can be attributed to insufficient thickness resulting from insufficient occlusal reduction. ✓ Most ceramic systems require that any isthmus be at least 2 mm wide to decrease the possibility of fracture of the restoration. |Page4 5. All line and point angles, internal and external, should be rounded to avoid stress concentrations in the restoration and tooth, reducing the potential for fractures. 6. All margins should be well defined and CSA should have a 90-degree butt joint angle to ensure marginal strength of the restoration. 7. The carbide bur or diamond used for tooth preparation should be a tapered instrument that creates occlusally divergent facial and lingual walls, which allows for passive insertion and removal of the restoration. The junction of the sides and tip of the cutting instrument should have a rounded design to avoid creating sharp, stress-inducing internal angles in the preparation. 8. Degree of divergence should be increased than that was prepared for indirect metal restorations, because the tooth-colored restoration is adhesively bonded and because only light pressure is applied during try-in and bonding. Also, resistance and retention form are required to help preserve the adhesive interface, so excessive divergence must be avoided. 9. Throughout preparation, the cutting instruments used to develop vertical walls are oriented to a single path of draw, usually the long axis of the tooth crown. 10. The facial and lingual walls should be extended to sound tooth structure and should go around the cusps in smooth curves. 11. Ideally, there should be no undercuts that would prevent the insertion or removal of the restoration. Small undercuts, if present, can be blocked out using a flowable composite resin. 12. The pulpal floor should be smooth and relatively flat. After removal of extensive caries or previous restorative material from any internal wall, the floor is restored to more nearly ideal form with flowable resin composite. 13. The facial, lingual, and gingival margins of the proximal boxes should be extended to clear the adjacent tooth by at least 0.5 mm. These clearances provide adequate access to the margins for the impression and for finishing and polishing instruments. 14. The gingival margin should be extended as minimally as possible because margins in enamel are greatly preferred for bonding and because deep gingival margins are difficult to impress and to isolate properly during bonding. 15. A cusp usually should be capped if the extension is two-thirds or greater than the distance from any primary groove to the cusp tip. |Page5  16. If the cusps must be capped, they should be reduced by 2 mm and should have a 90-degree cavo-surface angle. Immediate dentin sealing (IDS) Immediate dentin sealing (IDS) is a strategy in which a dentin bonding agent is applied to freshly cut dentin and polymerized before making an impression. The gold standard technique is the “etch-and-rinse” systems. Self-etch and universal adhesive systems can also be used. In the case of unfilled adhesive, a supplementary layer of flowable resin is recommended. Immediate dentin sealing should be followed by air blocking and pumicing prior to physical impression taking, this step is important to get rid of the oxygen inhibiting layer in case of delayed inlay cementation. Merits of the IDS technique: 1. Freshly-cut, contaminant-free dentin provides the optimum substrate for bonding. While, the bond strength is inferior in case of delayed cementation to contaminated dentin. Resulting in increased bond strength and retention, especially for tapered teeth with short clinical crowns and minimum removal of tooth tissue. 2. IDS and delayed restoration placement permit maturation of the dentin bond in an environment free of occlusal forces and overlaying composite shrinkage. 3. IDS reduce fluid and bacterial penetration. 4. Patient comfort during provisionalization. 5. Less need for anesthesia at the cementation appointment. 6. Reduced post-cementation sensitivity. Cavity optimization IDS can be immediately followed by the placement of regular or flowable composite in order to block out eventual undercuts and/or build up deep cavities, reducing restoration thickness and ensuring the light-cured polymerization of the luting agent. Finally, enamel margins are usually refinished before final impression to remove excess adhesive resin and provide ideal taper |Page6 Merits of cavity optimization: 1. Blocking undercuts instead of cutting them away. 2. Pulp protection. 3. Dentinal sealing. 4. Elevate the preparation floor. 5. Optimize the preparation geometry. Impression and model fabrication Tooth-colored inlay or onlay systems require an elastomeric or Stone cast optical impression of the prepared tooth and the adjacent teeth and interocclusal records, which allow the restoration to be fabricated on a Flexible model working cast in the laboratory. CAD/CAM Three options can be used for model generation; a. Regular impression and stone model: single use, rigid and liable to fracture or distortion with less predictable precision. b. Flexible model technique: elastomeric impression and polyvinyl-siloxane model (Grandioso inlay system); is an elastic, frequently used model with better precision. c. Chairside CAD/CAM systems: optical impression, digital model, designing software connected to a milling unit; the system allows excellent precision with minimal fabrication time and effort. Stone Cast Preparation: ✓ Steps for fabrication: 1. Once the die stone is set, the cast should be mounted and sectioned in preparation for the inlay fabrication. Care should be taken when the cast is sectioned, So, that the gingival contacts remain intact; this should be done even at the expense of the adjacent tooth. 2. The impression can be poured a second time if an additional cast is desired to better evaluate the proximal contact area and the path of draw. ✓ Inlay Fabrication: 3. The preparation margins are outlined with a red pencil. 4. A separating medium is applied to the internal surface of the die as well as to the surrounding and opposing teeth. One or two drops are placed into the cavity preparation and spread over the tooth so that each margin is well coated. The separating medium is then dried with a gentle air stream. 5. The composite resin of the correct shade is built up in two layers if shading of dentin and enamel is desired. Proximal and occlusal anatomy should be developed at this stage. |Page7  6. Light curing should then be completed; each surface is irradiated for 40 seconds. After light curing, the inlay is removed from the die. ✓ Heat Treatment: 7. The resin inlay is heat treated under vacuum in an oven for 15 minutes at 100 ̊C in a heat-curing oven. ✓ Finishing and polishing: 8. After heat treatment, the inlay is carved on the die with fine diamonds and mounted abrasive stones. 9. The inlay is then polished with composite polishing paste on a buff wheel. ✓ Characterization: 10. The inlay is thoroughly cleaned ultrasonically in a water bath. 11. It can then be characterized by applying one of the resin-based colorants to the surface of the inlay. 12. This characterizing stain is applied to pits and fissures with a brush. The stain is then light cured for 40 seconds. The Flexible Model Technique: Steps for fabrication: 1. The technique starts by making a polyvinyl siloxane impression of the preparation. 2. After the impression is made, a silicone-releasing agent is sprayed onto this impression. 3. A heavy-bodied polyvinyl-siloxane is now placed into the impression to make the flexible-working model by injection dye material into the preparation impression. 4. The rubber base material is allowed to set for the manufacturer’s recommended time and the impressions are separated. The use of the silicone releasing agent facilitates separation, if this agent was not used the two silicone impression materials would bond together. 5. The resin inlay is now fabricated by layering composite onto polyvinylsiloxane cast and light cured between layers. Try-in composite inlay or onlay on tooth for checking contour and contact (i.e. adjusting by adding increments of composite resin if deficient). CAD/CAM workflow: CAD/CAM fabricated indirect composites shows better accuracy and improved physical and mechanical properties. Composite resin blocks used for CAD/CAM system are manufactured under high controlled conditions that provide improved physical properties for the material. |Page8  Generation of a chairside CAD/CAM restoration begins after the dentist prepares the tooth and uses a scanning device to collect information about the shape of the preparation and its relationship with the surrounding structures. This step is termed optical impression. The system projects an image of the preparation and surrounding structures on a monitor, allowing the dentist or the auxiliary personnel to use the CAD portion of the system to design the restoration. The operator must input or confirm some of the restoration design such as the position of the gingival margins. After the restoration has been designed, the computer directs a milling device (CAM portion of the system) that mills the restoration out of a block of high-quality ceramic or composite in minutes. The restoration is removed from the milling device and is ready for try in, any needed adjustment, bonding, and polishing. The major disadvantages of chairside CAD/CAM systems are the high initial cost and the need for special training. Clinical studies have reported good results on the longevity of CAD/CAM ceramic restorations. Cavity provisionalization The teeth are protected with temporary eugenol-free restorations after impression making till the cementation time. Cementation procedure Cementation is the most critical step and involves the application of both the adhesive system and resin cement. Bonding composite restorations to tooth structure involves the dentin/adhesive-cement interface and the restorations/cement interface. Each step of the clinical and laboratory procedures has an impact on the esthetic results and longevity of indirect restorations. Successful adhesion depends on proper treatment of the internal surfaces of the restoration as well as the dentinal surface. Resin cement and dental tissue treatments Resin cements are now the most commonly used cements for all ceramic restorations. The choice of the resin cementation system for adhesive cementation is critical. They are divided into three categories according to the mode of adhesion of the cement; a. Total etch resin cement: |Page9  The total etch involves etching enamel and dentin with 36-37% phosphoric acid on the tooth surface followed by the application of dentin bonding agent which is available as a single bottle system. They have high bond strengths to the dentin. Care has to be taken not to dry the tooth surface completely as some amount of moisture should be there in the dentinal surface to ensure optimal bonding. It is then followed by cementation with resin cements. These cements require more number of steps for bonding and thus they are very technique sensitive. Indications for total etch cements are esthetic demand, anterior teeth where isolation is easy, low strength restoration such as veneers and preparations in the enamel. b. Self-etch resin cements: To reduce the number of operative steps and to simplify the clinical procedures, self-etching adhesive systems, which do not require a separate acid-etching step, have been introduced. The self-etch resin cements contains acidic monomers and phosphate as etchant combined with the primer. Common acidic monomers used are 10- MDP, 4-META (4- methacryloyloxyethy trimellitate anhydride) and GPDM (glycerol phosphate dimethacrylate). They are used when the preparation is deep in dentin to avoid the possibility of chemical irritation. Having less bond strength compared to the etch and rinse resin cements. c. Self-adhesive resin cements: The self-adhesive resins may be considered an alternative for luting indirect composite restorations onto non-pretreated dentin surfaces, even if bond strengths are lower than etch-and-rinse systems. Self- adhesive resin cements or universal adhesive cements are the newest among resin cements. They do not require pre-treatment of the dentin. They do not use any adhesive system thus reducing the clinical steps and technique sensitivity. They have multifunctional methacrylates which react with the hydroxyapatite of the tooth (adding chemical bonding potentials between the cement and the tooth tissues). Selective enamel etching is recommended to ensure better marginal integrity of the restoration. Resin cements are further classified based on the mode of curing into; a. Self-cure resin cements. b. Dual cure resin cements: For cementing deep inlays and onlays with few walls remaining. The cements used mostly are dual cured. Dual-cured resin cements have the advantages of controlled working time and adequate polymerization in areas that are inaccessible to light. | P a g e 10  c. Light cure resin cements: Light-cured resin cements have the clinical advantages of longer working time and better color stability. Used for thin ceramic restorations like labial veneers. N.B. sealed and optimized dentin has to be air-abraded with intra-oral air abrasion device (aluminum-oxide particles) prior to cementation, while unsealed dentin does not require this step. Ceramic cementation procedures Different lines of the ceramic materials were introduced for the construction of indirect restoration ex: a. Ceramics built on refractory casts b. Casted ceramics c. Pressed ceramics which offered better physical properties and marginal accuracy compared to the castable ceramics. d. Machined (milled) ceramics which showed excellency in precision in addition to the easy manipulation. The machined glass ceramics are the most commonly used nowadays. Glass ceramics surface treatment These ceramics contain feldspar, silicon and aluminium oxides. It is biocompatible, resistant to abrasion and compressive forces. Though it is highly esthetic it has low strength and toughness when compared to other types of ceramics. To overcome the low bond strength, adhesive cementation should be performed to increase the restoration’s resistance to fracture. 1. Ceramic etching: etching of the ceramic surface is done with a solution of hydrofluoric acid in concentrations of about 5 and 10 % for approximately 1 minute. Objective of ceramic etching: a. Provide increased surface area and provide micro mechanical retention. b. Cause selective dissolution of the glassy phase of the ceramic and makes it porous. This porous surface forms hydroxyl groups on the surface of the ceramic that aids in chemical adhesion to the resin cements via the silane coupling agents. 2. Ceramic silanization: Silanes are hybrid inorganic-organo- functional monomers that are chemically bifunctional. i.e. non- hydrolysable groups such as methacrylate and alkoxy hydrolysable groups. When reactive silanes are applied over the etched ceramic surface, the hydrolysable alkoxy groups of the silanes react with the hydroxyl groups of the ceramic exposed through etching and non-hydrolysable | P a g e 11  organic groups reacts with unset resin cement. Silane is applied for 1 minute and air dried. Indirect Composite surface treatments Composite surface treatments are necessary for adhesion of indirect composite restorations. 1. Resin composite etching: The internal surfaces of indirect composite restorations should be air abraded with aluminium oxide, using a sandblasting device (mechanical etching). Sandblasting of the composite surfaces has been recommended as a predictable means for enhancing the retention between resin cements and indirect composite restorations. This allows for micro-porosity creation and increased surface area of the resin composite for better micro-mechanical interlocking with the resin cement. Tribochemical coating, forms a silica-modified surface as a result of air abrasion with silicon dioxide (SiO2)-coated aluminium oxide particles. The surface becomes chemically reactive to the resin by means of silane coupling agents. 2.Composite silanization: Silane coupling agents have been also suggested by many researches as adhesion promoters between different resin phases. Key Elements for successful indirect resin composite restoration 1. The cavity design should be restricted to the initial defect. 2. Use of visible light cured resin liner to block the undercuts. 3. Roughening of the inlay fitting surface and application of bonding agent. 4. Selective bonding through acid etching of the margins. 5. Use low viscosity dual cure resin composite cement. 6. Complete seating of the inlay with continuous finger pressure followed by light curing from every surface for 40 sec. 7. Non-destructive finishing removing the excess luting cement. 8. Regular check-up and proper maintenance of the inlay. 9. Use of resin composite material specified for inlays fabrication. https://youtu.be/mgU_nE3XJwA Head of Conservative and Restorative Department D.Mai Mamdouh | P a g e 12