Provisional Restoration

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    21-Apr-2015

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<p>;-=,- Q-=,- = ;~- ;-=,- Q-=,- = ;~-PROVISIONALRESTORATIONS RESTORATIONS Provisional crown or fixed partial denture is a restoration applied to the prepared tooth temporarily to protect it and to keep the patient comfortable during fabrication of the permanent restoration. It influences the ultimate success of the final restoration. The ultimate success of the final restoration. The word provisional means established for the time being, pending a permanent arrangement (temporary) Functions of provisional restoration : -- Protection - Positional stability - Esthetics - Esthetics- Mastication -Protection :-The provisional restoration protects the pulp, the periodontiumand the prepared tooth. It protects the pulp from thermal and chemical irritation caused by foods, drinks and dental plaque.It protects the peridontiumfrom injury by food impaction due to loss of contact and gingival recession due to loss of to loss of contact and gingival recession due to loss of normal buccal and lingual contours.Protects the integrity of the prepared tooth from fracture or abrasion due to chewing of hard food on unprotected preparation margins. This is particularly true with partial coverage designs in which the margin of the preparation is close to the occlusal surface and could be damaged during chewing. -Positional stability: - To maintain the tooth position and prevent mesial, distal drift or over eruption which will change the relation with the surrounding teeth. teeth. To maintain the gingival tissue contour, prevent gingival hyperplasia or gingival recession. -Mastication: To maintain the function of the prepared teeth and enables the patient to use them in mastication satisfactorily. -Esthetic:- To restore and maintain esthetic especially in the visible edentulous areas.Ideal requirements:- An optimum provisional restoration must satisfy many interrelated factors which can be classified as biological, mechanical and esthetic requirements esthetic requirementsI -Biological requirements :-- Pulp Protection - Periodontal health-Tooth position. -Tooth Protection against fracture. -Tooth Protection against fracture.PROVISIONAL RESTORATIONS REQUIREMENTS Biological PULPAL PROTECTION Thermal changes or agression agression Microleakage POSITIONAL STABILITY Extrusion or lateral drifting OCCLUSAL FUNCTION Patient comfort Muskuloskeletal stability PROVISIONAL RESTORATIONS PROVISIONAL RESTORATIONS REQUIREMENTS CLEANSABLE Maintain gingival health MARGINAL INTEGRITY MARGINAL INTEGRITY Not impinging gingival tissue Tissue proliferation Recession Hemorrhage Vertical or Horizontal overhanging marginII- Mechanical requirements :-The restoration should be strong enough to withstand occlusal forces without fracture.-It should be retentive to avoid displacement- Easy removal for reuse without being - Easy removal for reuse without being damagedIII- Esthetic requirements : The restorations especially those for anterior teeth should have -Natural tooth color and contour.-Natural translucency -Natural translucency -Colour stability Materials and procedures :-Ideal requirements of Provisional restoration materials: -Ease of handling, adequate working time, easy moldability and rapid setting time.-Biocompatibility non toxic, non allergic, non exothermic.-Dimensional stability during solidification. -Dimensional stability during solidification.-Ease of contouring and polishing. -Adequate strength and abrasion resistance.-Good appearance, color control and color stable.-Ease of adding to repair or correct.-Chemical compatibility with provisional luting cements. Available materials: -The materials can be divided into four resin groups . Polymethyl methacrylate ( Jet , Duralay ) . Poly (ethyl, vinyl or isopropyl) methacrylate. (Unifast L.c, Trim, Snap) (Unifast L.c, Trim, Snap) . Microfilled composite resin (Protemp).. Light cured microfilled urethane dimethacrylate (Triade)The light cured materials have two advantages:--The ingredients are mixed by the manufacture so show little porosity. so show little porosity.-Working time is unlimited. Single provisional crown may be custom made or preformedResin Cellulose acetate Polycarbonate Metal Aluminum (anatomic)Aluminum shell Tin silver (anatomic)Nickel chromium (anatomic) These preformed crown forms are commercially available; they can not satisfy the requirement of a provisional restoration, so they must be lined with autopolymerizing so they must be lined with autopolymerizing resin. They are available in a variety of tooth types and sizes.PROVISIONAL RESTORATIONS TYPES PREFABRICATED (crowns) Aluminum cylinders Anatomical metal crown forms Clear celluloid shells Tooth coloured polycarbonate Tooth coloured polycarbonate crown forms CUSTOM (crowns or fixed partial dentures) Material (variety of resins) Technique (direct or indirect)-Polycarbonate crown: Suitable for anterior teeth as it is constructed from a color stable resin, but available in only one shade, this can be modified to a limited extent by the shade of the lining resin. They extent by the shade of the lining resin. They are supplied in incisor, canine and premolar tooth type.Steps:-*Measure the mesiodistal width of the crown using the mold guide provided with the kit and select the shell having the same width or slightly larger width, and place it on the prepared tooth.*Mark the crown height on the shell which is equal to the incisocervical height required for the completed crown using a incisocervical height required for the completed crown using a pencil. *The excess gingival length is trimmed away with an acrylic bur following the curvature of the prepared cavosurface margin.*Try the shortened shell on the prepared tooth and adjust it if required until it becomes properly positioned without forceful gingival contact.*Apply a uniform thin coat of petrolatum to the prepared tooth and adjacent tissues (or on the fast set plaster cast) *Mix the auto polymerizing resin with the proper shade, fill the shell and place it over the prepared tooth using the adjacent teeth as a guide for complete seating.*Immediately remove any marginal excess and when the rubbery stage is of polymerization reached ( after min ) rock the stage is of polymerization reached ( after min ) rock the crown faciolingually to loosen it then remove it to avoid its difficult removal if complete polymerization taken place in the mouth .*Put it in warm water to polymerize ( min) then adjust the margins, contour it if required, adjust the occlusion and polish it to be ready for cementation. -Cellulose acetate: * Available for all teeth types and sizes*Made from thin (.-.) transparent shell.* Provide mold to form P.R.*Does not bond chemically or mechanically to the resin.* The shade depends on the lining resin. * The shade depends on the lining resin.*After the polymerization the crown is peeled off*Usually need addition to reestablishing the proximal contact*Less esthetic than poly carbonate crown*It is less expensiveSteps The crown form is selected and adjusted as polycarbonate crown but the margin can be cut with scissors. Fill the crown with resin as described before, Fill the crown with resin as described before, but there is no bond between then so it should be removed from the set material and the contact area need addition after that to get proper contact. -Aluminum / crowns and Tin-silver: -Suitable for posterior teeth Aluminum crown may beanatomically shaped or non anatomical shells resembling tincans which are the least expensive form, but they requiremodification and lining with acrylic resin to achieveacceptable fit, good occlusal and axial surfaces .They are acceptable fit, good occlusal and axial surfaces .They arefabricated from soft material, this softening cause rapid wearof the crown, So used as a temporary coverage for short timeonly.Steps:-*Measure the mesiodistal width of the crown space and select a suitable shell.*Measure the occlusocervical height and trim the shell cervically using a pair of scissors. the shell cervically using a pair of scissors. Sharp edges left by the cutting should be smothered with green stone. *Put the trimmed shell over the prepared tooth, if any gingival blanches is observed, the shell should be trimmed further. *After marginal adjustment, ask the patient to occlude, the soft aluminum will deform until normal intercuspation is reached. Contouring pliers can be used to make small size modifications. modifications. *Apply petroleum to the prepared tooth and adjacent tissues, mix self cure resin and fill the shell when it reaches the correct stage.*Put the shell over the tooth, instruct the patient to close and immediately remove the marginal excess. *Remove it from the mouth at the rubber stage (after min) loosen the crown and remove it. Allow it to completely polymerize in warm water then finish the margins, adjust the occlusion and polish it. margins, adjust the occlusion and polish it.*If the contact area is deficient, resin can be added to correct it after grinding of metal in the contact area to allow resin to resin bond. *Polish, clean and cement the restoration.-Nickel-chromium crowns: -Used mainly for deciduous teeth without lining with resin. They are trimmed and adapted with contouring pliers and cemented with high strength cement. They are longer-term strength cement. They are longer-term provisional restoration due to their hardness.Custom made provisional single crown:May be constructed by Indirector ordirectmethod using resin material.I- Custom made indirect provisional restoration : In this technique the provisional is constructed outside the mouth so it has the following advantages over the direct technique: -There is no contact of free monomer with the -There is no contact of free monomer with the prepared tooth or gingiva, which might cause tissue damage, allergic reaction or sensitization. -The prepared tooth is not subjected to heat created from the exothermic reaction of resin which might cause irreversible pulp damage. The marginal fit of indirectly constructed provisional is better due to its complete polymerization undisturbed on the stone cast, while the direct construction necessitate the removal of the restoration from the mouth while it is in the rubber stage before complete polymerization to avoid its locking into the undercuts. Polymerization outside locking into the undercuts. Polymerization outside the mouth without a supporting form will result in distortion and improper fit.. -The indirect technique reduced the chair time and can be carried out by a well trained assistant; this minimizes the disturuption in the office schedule and earns the patients appreciation.Steps:*The study cast is constructed from alginate impression before preparation.*If the tooth or teeth to be restored has any obvious defect, it should be corrected on the study cast with red utility wax.* Fill all the embrasures with wax or putty to eliminate undercuts.*Construct the rubber base index for the tooth to be prepared or *Construct the rubber base index for the tooth to be prepared or the index may be constructed from the patient mouth if the tooth or teeth are intact. *Upon completion of the preparations, make alginate impression for them and pour it in fast-setting plaster.* After setting, trim the cast so that it includes only one toothon either side of the prepared tooth. *Try-in the index to verify its fit on the fast setting stone cast, coat the cast with separating medium.* Mix the temporary acrylic resin in a dappen dish and put some on the protected areas of the cast, such as interproximal spaces and in grooves and boxes.*As the resin begins to lose its surface gloss and become slightly dull, fill the index, place it over the cast and wrap rubber dull, fill the index, place it over the cast and wrap rubber bands around them, taking care of proper alignment. *Excessive force can over seat the cast resulting in provisional restoration with thin occlusal surface. Also uneven force can torque the cast to any side resulting in deficient provisional restoration. Put them in pressure pot if available or warm water to accelerate polymerization (hot water causes boiling of the monomer porosity).*The restoration is then removed from the cast, if it is not easily removed from the cast; break the cast with a heavy laboratory knife. *The provisional restoration is then finished using acrylic burs, sand paper discs with different grits. Finally the restoration is polished with pumice, rag wheel and rubber cups to be ready for cementation. II- Custom made direct provisional restoration : The rubber index filled with the acrylic resin is seated on the prepared teeth directly in the patients mouth, so this technique has significant disadvantages as: *potential tissue trauma from the big amount of polymerizing resin (pulp, gingiva) *Poor marginal fit.Therefore, the routine use of directly formed provisional restoration is not recommendedFABRICATING PUTTY MATRIXFABRICATING PROVISIONALFABRICATING PROVISIONALFABRICATING PROVISIONALFABRICATING PROVISIONALFABRICATING PROVISIONALFABRICATING PROVISIONALFABRICATING PROVISIONALFABRICATING PROVISIONALFABRICATING PROVISIONALCementation : The primary function of provisional luting agent is to provide a seal, preventing marginal leakage and pulp irritation. The luting agent should not provide retention and resistance should not provide retention and resistance against occlusal and lateral forces because it is of low strengthIdeal properties of provisional luting agent.- Provide seal against leakage and oral fluid.- Of adequate strength.- Low solubility.- Chemical compatibility with provisional polymer. -Ease of manipulation. -Ease of manipulation.- Adequate working time and short setting time.- Compatibility with definitive luting agent and has anobtunding effect on the pulp. - Ease of removal of excess. Procedures :- Lubricate the external surface of the restoration with petrolatum to facilitate removal of excess cement. Mix the two pasts and apply a small quantity just occlusal to the cavosurface margins avoid filling the crown with cement because it will provide hydraulic crown with cement because it will provide hydraulic pressure and will force excess material in the sulcus. Seat the restoration and allow the cement to set them remove the excess from the gingival crevice with an explorer and from interproximal spaces by dental floss.Thank you Thank you</p>