indirect.docx

\- Direct tooth restorations have successfully performed and maintained their role for restoration of small to moderate defects. However, in certain circumstances where **optimum occlusion**, **proximal contour** and **marginal adaptation** are [difficult to achieve,] indirect restorations offer the...

\- Direct tooth restorations have successfully performed and maintained their role for restoration of small to moderate defects. However, in certain circumstances where **optimum occlusion**, **proximal contour** and **marginal adaptation** are [difficult to achieve,] indirect restorations offer the solution. Important definitions: ---------------------- - **Inlays:** are indirect restorations which involve the occlusal and proximal surface(s) of posterior tooth - **Onlays:** are indirect restorations which cap one cusp - **Overlay:** are indirect restorations which cap all cusps **- Indirect restorations are made from either:** - **Metallic restorations:** (Cast Gold Restorations or Base Metal Alloys) - **Non-metallic restorations (tooth-colored restorations):** (Ceramic or post cured resin composite) **Cast Gold Restorations** ========================== **- Cast gold inlay** is a precise metallic duplicate for the prepared cavity which is fabricated outside the oral cavity and cemented in place in one piece in order to restore the lost tooth structure 1- Advantages of cast gold restoration: --------------------------------------- 2- Disadvantages of cast gold restoration: ------------------------------------------ 3- Indications for cast gold restorations: ------------------------------------------ Extensive tooth involvement, including: Correction of occlusion or when teeth suffer from wear, attrition or erosion or for diastema closure. Adjunct to perio-therapy. Fixed or removable prostheses abutments. As a restoration for cases that requires saving of clinic chair-time, since most of the work can be completed in the lab. 4- Contraindications for cast gold restorations: ------------------------------------------------ High Plaque and high Caries risk patients Where other permanent direct restorations are indicated for tooth conservation. Developing or Deciduous Teeth. Compromised Patient. Esthetically sensitive areas. 5- Design of cavity preparation: -------------------------------- ### Outline form: \- **Internal cavity walls** must be uniformly tapered occlusally (slight occlusal divergence with a degree of taper 3-5o for each wall). This will result in a cavity that has **wider external outline** form than the **internal outline form** which is needed for the **seating** of any restoration fabricated outside patient mouth **- Cavo-surface margin** should be **beveled**; such bevel must be proportional to the cavity depth. This means that it should **not exceed one fourth of the cavity wall**. This allows for **burnishing** of the metal alloy **to bring the margins of the alloy in contact with enamel** and **prevent exposure of cement line** **- Gingival seat Cavo-surface margin** should be trimmed with GMT creating short bevel (30 degree and 0.5-1mm width). This enhances the seating ability of final restoration at this area \- \- All internal line angles must be well defined but not sharp. \- In case of class II cavity inaddition to primary flares that are regularly made with direct restoration to free the contact their is a secondary flares Primary flares: which are made to free the contact are accompanied with secondary flares. Secondary flares: are created on proximal walls (facial and lingual walls). **[Secondary flare is necessary for several reasons:]** o Extends the margins into the embrasures, making these margins more self-cleansable and more accessible to finishing procedures during the inlay insertion appointment. o Creates obtuse angled marginal tooth structure (140-150 degree). **Resistance and retention form:** \- Cast gold restorations have **high strength properties**; thus, giving the restoration bulk is not a prime request as for brittle direct restorative materials. However, care must be given not to subject thin sections to direct occlusal forces that **causing plastic deformation** of the materials which will lead to open margins \- **Tooth resistance includes:** the walls should be parallel or perpendicular to force direction and should follow the enamel rods directions, having rounded but definite line angles and making the cavity outlines follow the sweeping curves. \- Restoration resistance on the other side is not a crucial issue as compared to direct brittle restorative material due to the inherent strength property of this material. \- Axial retention could be encountered mainly by friction of opposing walls. This governed by the degree of wall tapering, length, roughness, and cement type. Increasing the degree of tapering or occlusal divergence will decrease the frictional retention **Ceramic Restorations** ======================== 1. Advantages over metallic restorations: ----------------------------------------- Color blending with adjacent tooth structure could be well established enhancing aesthetic. In addition, this color match is durable. A ceramic restoration will accumulate low plaque on its surface. They offer lower thermal diffusivity which decreases the thermal irritation to the tooth. Through bonding, they offer increase in the fracture resistance of the restored tooth. 2. Disadvantages: ----------------- Technique sensitive, whereas much time and attention are required to be given when these restorations are fabricated and placed. The probability of unbonded restoration to fracture during the try-in phase. Number of appointments and laboratory fee is an added factor during treatment plan. Potential of wearing of opposing tooth, however newer versions of ceramics are less abrasive. In ceramics with surface stain, occlusal adjustment results in the loss of the surface colorants. 3. Indications: --------------- Extensive tooth involvement with undermined or weak enamel. Where metal allergy is a factor. The restoration of teeth in an arch opposed by already present porcelain restorations. Teeth where it is difficult to develop retention form. 4. Contraindications: --------------------- Evidence of para-functional habits and aggressive wear of the dentition. Patients with gold restorations in opposing teeth. The problems of maintaining a dry field. 5. Preparation design requirements: ----------------------------------- \- Some differences in the cavity design should be encountered that are necessary to overcome the inherent weakness of these restorative materials. **[These differences include:]** - Keeping a homogenous thickness of the material is of prime concern; the floor should have an even depth of 1.5-2.5mm. - The cavity walls should be slightly more divergent from the pulpal floor toward the enamel surface. - There is no need for frictional fit as required for metallic cast restorations. - The occlusal cavo-surface margin of the preparation should not be beveled. - All internal line angles must be rounded. This is achieved by performing the preparation with a specially designed tapered cylinder that has a flat **Indirect resin composite restorations** ========================================= \- Inlays and onlays made of resin composite are fabricated either intraorally (direct) or on a cast (indirect) or intra-orally and then adjusted on a cast (direct/indirect). After polymerization, the restoration is bonded in place with a resin luting cement. 1. Advantages over direct resin composite restorations: ------------------------------------------------------- Less polymerization shrinkage; since compensation for shrinkage occurs through curing the material outside of the mouth. Better control of contact area and contours. Better marginal adaptation especially in the most critical areas such as proximal gingival seat. Increased strength properties of the resin composite because of the post curing process. Post-curing can be done by post-cure unit specially made for this purpose, under heat with and without curing light or curing box. 2. Advantages over ceramics are: -------------------------------- Reduced or no lab fee if done in clinic. Ready repairability of material intraorally. Possibility of occlusal surface adjustment. Easy removal if replacement becomes necessary. More user-friendly in clinic and lab. 3. Disadvantages compared to direct resin composite are: -------------------------------------------------------- To obtain flared cavity walls, more tooth structure is required to be removed. Reliable chemical bonding does not occur between the restoration and the resin cement, as the inner surface has relatively few unreacted methacrylate groups. 4. Disadvantages compared to ceramics are: ------------------------------------------ Adhesion of resin cement is more reliable to ceramic restoration than resin composite ones. Although some onlay ceramics cause wear of opposing enamel, they also provide long-term occlusal stability, which resin composite may not provide. 5. Cavity design for indirect resin composite restoration: ---------------------------------------------------------- \- It is the same as that described for ceramic restorations. 6. Fabrication of the indirect resin composite restoration: ----------------------------------------------------------- **- Indirect Technique:** \- This technique employs an impression of the prepared tooth and fabricate the inlay on a die. The indirect inlay technique can be performed as either a one-visit or two-visit method. The one- visit method involves making an impression material and pouring the impression with a fast-setting material \- For **direct-indirect technique**, the inlay is fabricated directly on the tooth preparation, after a lubricant application, in the mouth and then the inlay is removed and cured in a curing oven \- **During direct fabrication,** a rubber dam is recommended to be used to avoid saliva and hemorrhagic contamination