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
In dentistry, inlays and onlays are used to fill cavities, and then cemented in place in the tooth. This is an alternative to a direct restoration, made out of composite, amalgam or glass ionomer, that is built up within the mouth.
| Inlays and onlays | |
|---|---|
| ICD-9-CM | 23.3 |
| MeSH | D007284 |
Inlays and onlays are used in molars or premolars, when the tooth has experienced too much damage to support a basic filling, but not so much damage that a crown is necessary. The key comparison between them is the amount and part of the tooth that they cover. An inlay will incorporate the pits and fissures of a tooth, mainly encompassing the chewing surface between the cusps. An onlay will involve one or more cusps being covered. If all cusps and the entire surface of the tooth is covered this is then known as a crown.
Historically inlays and onlays will have been made from gold and this material is still commonly used today. Alternative materials such as porcelain were first described being used for inlays back in 1857. Due to its tooth like colour, porcelain provides better aesthetic value for the patient. In more recent years, inlays and onlays have increasingly been made out of ceramic materials. In 1985, the first ceramic inlay created by a chair-side CAD-CAM device was used for a patient. More recently, in 2000, the CEREC 3 was introduced. This allows for inlays and onlays to be created and fitted all within one appointment. Furthermore, no impression taking is needed due to the 3D scanning capabilities of the machine.
