Inlays and Onlays
- Inlays are used to fill cavities in molars or premolars.
- They are an alternative to direct restorations.
- Inlays cover the pits and fissures of a tooth.
- They are mainly used for the chewing surface between the cusps.
- Inlays can be made from gold, porcelain, or ceramic materials.
- Inlays have a fine line of contact, minimizing recurrent decay.
- Inlays have no limitations in material choice.
- Inlays are superior in resistance to occlusal forces and protection against recurrent decay.
- Long-term studies show no significantly lower failure rates for ceramic or composite inlays compared to direct fillings.
- Inlays are indirect restorations without cuspal coverage.
- They are used when amalgam or composite restorations are inadequate.
- Inlays are fabricated outside of the mouth.
- They can be made from gold or porcelain.
- Inlays can be made in a dental laboratory or using CAD/CAM dentistry.
- Inlays/onlays are indicated when teeth are weakened and extensively restored.
- Inlays are used for repeated breach in the integrity of a direct filling.
- Inlays are used when placement of direct restoration is challenging.
- Onlays are used to protect weakened tooth structure without additional removal of tooth tissue.
- Onlays can be used if there is minimal contour of remaining coronal tooth tissue.
- Poor oral hygiene is a contraindication for providing inlays and onlays.
- Plaque and active caries should be managed before providing indirect restorations.
- Caries risk should be reduced to prevent recurrent caries around the restoration.
- Subsequent caries can be caused by plaque retentive features or poor bonding.
- Contraindications may result in failure of the restoration.
- Parafunctional habits and heavy occlusal forces are contraindications for inlays and onlays.
- Evidence shows greater failure of onlays and inlays in molars than premolars.
- Porcelain fracture is the most common cause of failure.
- Avoiding heavy occlusal forces can ensure longevity.
- Cuspal coverage onlays should use porcelain instead of composite.
- Indirect restorations are contraindicated in patients under 16.
- Large pulp chamber and wide dentinal tubules increase stress on the pulp.
- Risk of nerve supply damage during cavity preparation.
- Unfavorable margins due to continued eruption and skeletal development.
- Waiting until full cooperation is advantageous.
- Patients need to cope with dental impressions for indirect restorations.
- Digital impression systems can help patients who can't withstand conventional impressions.
- Digital impressions provide highly accurate models and eliminate patient discomfort.
- However, these systems are not widely available in dental practices.
- Extensive caries or tooth surface loss may require full coverage extra coronal restorations.
- Direct restorations like composite may be beneficial for small restorations.
- Inlays require elimination of undercuts, so direct restorations preserve tooth structure and avoid laboratory costs.
- Tooth preparation aims to preserve more tooth tissue compared to crown preparation.
- Preparation of opposing cavity walls should avoid undercuts for optimum retention.
- All-ceramic restorations allow slightly over-tapered cavity shapes.
- Gold restorations require parallel walls for retention.
- Two appointments required for preparation and cementation, with a provisional restoration in the meantime.
- Indirect restorative technique involves taking an impression and using CAD-CAM technology.
- CAD-CAM allows for one-visit provision of indirect restorations.
- Lost wax technique using Type 1 or Type 2 inlay wax can be used for cast metal/ceramic restorations.
- Inlay wax is chosen for its brittleness to identify and remove undercuts.
- Lost wax technique involves embedding the wax pattern into investment material for casting.

Casting Methods
- Metal can be melted using gas and compressed air, gas and oxygen, or electric arc.
- Casting methods include steam pressure or a centrifugal system.
- Porosity can occur due to uncompensated alloy contraction and absorption of mold gases.
- Possible casting faults include subsurface nodules, ridges, fins, roughness, and foreign bodies.
- Gold can be used to produce inlays and onlays, with oxides removed by ultrasonic bath.

Slip Casting Technique
- Applicable only to sintered alumina core porcelain.
- Sub-structure made of alumina powder and modeling fluid is built on a special die.
- Sintering the die with the sub-structure absorbs the fluid and tightens the alumina powder.
- Lanthanum aluminosilicate glass powder is painted on the outer surface of the sub-structure.
- Zirconium oxide can be applied for further strengthening.

Direct Restorative Technique
- No impression of tooth preparation required.
- Tooth preparation is coated with separating material like glycerin.
- Composite restoration is built directly on the preparation, taking the shape of the cavity.
- Restoration is light-cured in the tooth and then removed for further light-curing.
- Only applicable when composite is used as the restorative material.

Materials and Benefits
- Ceramic inlays produced via indirect restorative techniques have similar longevity.
- Study by Rippe et al. supports this finding.
- Longevity of ceramic inlays is comparable regardless of the production method.
- No specific statistics or numbers provided.
- Indirect restorative techniques contribute to the longevity of ceramic inlays.
- Gold has high strength and ductility, making it ideal for withstanding masticatory forces.
- Ceramic offers more aesthetic restoration color and high wear resistance.
- Unreinforced ceramic has reduced strength and higher fracture risk.
- Composite provides great aesthetics and can be easily repaired or modified.
- Metal-ceramic inlays have lower fracture resistance compared to all-ceramic inlays.
- Inlays and onlays improve the sturdiness and wear of teeth.
- Super curing enhances the durability of inlays.
- Close to parallel walls and