DENTAL INLAY

DENTAL INLAY Dental inlays are used to repair decaying teeth that do not require extensive bridgework, or to replace older metal fillings. It is similar to a filling and lies inside the cusp tips of the tooth. They are custom-made to fit the prepared cavity and are then cemented into place. Most dental inlays are composed of porcelain, though some can be made from gold or composite resin. Patients that desire a natural smile often request porcelain inlays in lieu of metal fillings, since they are highly undetectable.

In addition, inlays last up to thirty years, which is significantly longer than any other type of filling. Due to their longevity and durability, the placement of inlays often prevents the need for further dental work at a later time. Another important aspect of inlays is the fact that they can strengthen teeth up to seventy percent, which often prevents future tooth breakage or loss. Inlay is an indirect restoration which is fabricated in the lab and can be cemented to the prepared cavity.

There are two types of inlays: Direct inlays are made in the dental office. They are placed in one visit. Indirect inlays are made in a laboratory. Two visits are needed to place them. The type your dentist will use depends on how much of the tooth is left.

DIRECT VS INDIRECT RESTORATION In direct filling the material is taken in plastic state into the prepared cavity where it hardens. In indirect restoration the hardened filling is cemented into the prepared cavity

DIFFERENCE

AMALGAM RESTORATION

INLAY PREPARATION

Advantages of inlay Better physical properties Clinical longevity Easier to carve a large restoration to normal occlusion and ideal contacts Easy to make guide planes for removable prosthesis Easy to alter the occlusion Aesthetic restoration

Disadvantages of inlay Costlier than direct restoration(Gold inlays cost 4-5 times that of a silver amalgam) Two visits for the patient Microleakage, dependent on cement

Types Gold inlay Porcelain inlay Composite inlay

GOLD INLAY ADVANTAGES a) Co efficient of thermal expansion and wear resistance similar to natural tooth b) gold is relatively stable and inert in our bodies. c) Gold does not corrode & is highly polishable d) Strong even in thin section, can be burnished for close adaptation e) Clinical longevity

GOLD INLAY DISADVANTAGES a) Costly(not in long run) b) Not aesthetic

Gold inlay

Indications 1. When the cavity width does not exceed 1/3rd the intercuspal distance. 2. In case of extensive proximal caries involving the buccal and lingual line angles of the tooth. 3. In situations where the proximal margins are extending subgingivally. This is because well polished gold alloys are compatible with the periodontium. 4. Whenever there is need to establish ideal contact, contours and embrasures. The mesiodistal dimension of cast gold inlays can be extended to establish good contact. 5. In a grossly carious tooth where one or more but not all cusps need coverage. 6. In patients with good oral hygiene and low caries incidence. 7. When there are other gold castings present in the mouth.

Contraindications for Gold Inlays 1. Gold inlays are used as an abutment for a fixed or a removable prosthesis. In these situations the gold inlays are not strong enough retainer. 2. They are contraindicated in post endodontic restorations as they can wedge and fracture the remaining tooth structure. 3. In young permanent tooth gold inlays are avoided as there are increased chances of iatrogenic pulp exposure. 4. in patients with high plaque and caries incidence. Gold inlays should be avoided as there may be a greater tendency for recurrent caries. 5. When the adjacent or opposing teeth have dissimilar metallic restorations cast gold inlays should be avoided in order to prevent galvanism. 6. When cost is major factor for the patient, gold inlays are not indicated. 7. Gold inlays are not preferred in case of grossly destroyed teeth with weak cusps.

PORCELAIN INLAY

Part of tooth destroyed by a cavity

Step 1. The cavity is removed with a drill and the site is prepared.

Step 2. The preparation has a diverging shape towards the opening.

Step 3. A lab fabricates a porcelain inlay, which exactly replicates the lost tooth structure.

Step 4. The inlay is cemented into place and becomes indistinguishable from the rest of the tooth. It is extremely strong and durable.

Advantages Highly esthetic. Acceptable marginal fit. Conservation of tooth structure. Less occlusal wear. Highly technique sensitive. Low thermal conductivity. Low coefficient of thermal expansion. Biocompatibility.

Disadvantages High cost. Need for special and laboratory equipment. Fabrication and cementation processes are highly technique sensitive. Ceramic inlays are brittle and can fracture during try in or cementation. The increased hardness of ceramics can wear the opposing teeth.

Indications .High esthetic demands. 2. Replace moderate to large existing restoration. 3. Fractured tooth/restoration. Moderate to large primary caries. Patients with good oral hygiene. When there is no excessive attrition. Where access and isolation are easy. When there is no excessive undercuts in the preparation.

Contraindications: Unable to isolate the field. 2. Parafunctional habits like clenching, bruxism, excessive wear. 3. Patients with poor oral hygiene. In case with minimal tooth loss. When there is inadequate enamel left for bonding. When there are marked undercuts in the cavity preparation.

COMPOSITE INLAY This is an alternative to gold or all ceramic inlays and onlays. They still perform the same function, namely that of treating a damaged or decayed tooth and are considered a stronger and more appealing option than a normal filling.

ADVANTAGESHigh esthetics. Better control of the contact areas. Excellent marginal adaptation. Reduced or no laboratory fee if done in office. Ready reparability of material intraorally. Compensation for complete polymerization shrinkage by curing the material outside the mouth. Increased composite resin strength because of the heat curing process.

DISADVANTAGES 1. Wear faster. 2. Less stable. 3. Higher cost time. 4. Difficult to modify extrinsic color chair side. 5. More tooth reduction to create path of insertion.

Indication of composite inlay Replacement of large amalgam restorations. Replacement of direct resin composite restorations in premolar and molar. Large caries. Esthetics.

Contraindication of composite inlay Heavy occlusal forces. Inability to maintain dry operative field. Deep subgingival preparations.

CONTRAINDICATIONS Cracked teeth (onlay) Wide isthmus/deep pulpal (onlay)

Techniques Two techniques Direct technique(difficult and tiring for both the patient and the operator) Indirect technique (easier for both and gives better result)

DIRECT TECHNIQUE Where inlay wax is inserted into the prepared cavity, carved, contacts made and taken out of the cavity. the lab procedure than follow

Direct technique

INDIRECT TECHNIQUE Where an impression of the prepared cavity is taken and all other procedures are followed on the model in the lab.

Indirect technique

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CEMENT LUTE Cement lute is the weakest part of inlay restoration Zinc phosphate cement and glass ionomer cements have been used for luting Presently non dissolving resin based luting agents are used but again the shrinkage

Controversies Inlays crack teeth ( careful selection) Inlays are expensive ( are they?) Inlays are not esthetic (careful cutting plus tooth colored inlays) Must place bevel at occlusal and proximal

PREPARATION Outline form Resistance form Retention form Remove any undercuts Finish the walls

Outline form A straight cut tapering fissure bur is used Caries is removed from all around Any existing restoration should be removed Occlusally divergent walls (upto10 degrees) Sharp internal angles

Outline form Occlusal dovetail Butt joint at occlusal The proximal flare must take the margin into the respective embrasures clearing the adjacent teeth

Resistance form Minimum depth is 2mm all around Proximal box should be at least 1-1.5mm deeper Flat pulpal floor

Resistance form If cusps are weak go for onlay preparation Onlay-an inlay that covers the cusp of the tooth Cuspal reduction-parallel to the slope Reduction should not be less than 0.5mm depending on the material, occlusion, working or non working cusp All the cusps should be out of occlusion in all excursions

Retention form Retention is based on nearly parallel walls Up to 10 degree occlusal divergence is allowed for ease of impression taking and placement of the final restoration There should be no undercut in the final preparation

Finish the walls A 60 degree gingival bevel is given by using a gingival margin trimmer It allows proper seal of the restoration in this area Paint the final outline to provide a more pleasing outline of the final restoration

All of the following are advantages of gold inlay excepta) The co efficient of thermal expansion and wear resistance is similar to natural tooth b) Its relatively stable and inert in our bodies. c) Gold does not corrode d) A single visit procedure for the patient.

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