Cavity Base Materials PDF

CAVITY BASE MATERIALS ASSIST.PROF.DR. ÖZGÜ KARADAĞLIOĞLU   A dental base is material that is placed on the floor of the cavity preparation in a relatively What is a thick layer. Its purpose is to protect the pulp by providing thermal insulation due to de...

CAVITY BASE MATERIALS ASSIST.PROF.DR. ÖZGÜ KARADAĞLIOĞLU   A dental base is material that is placed on the floor of the cavity preparation in a relatively What is a thick layer. Its purpose is to protect the pulp by providing thermal insulation due to dental temperature changes and absorbing occlusal base? forces. It can also be used to line out undercut areas for indirect restorations such as gold or composite inlays.  Even there are several types of basematerials, nowadays they use mostly zinc phosphate cement and glass ionomer cement.   It should be bacteriostatic/bactericidal. It means that it prevents from increase of bacteria. Which  It shouldn’t be toxic. It should not cause damage to hard and soft structures properties  It should hermetically cover the cavity to should have prevent microleakage, the development of secondary caries or postoperative sensitivity. the cavity  The cavity base is often expected to form a base thermally insulating barrier to protect the pulp from sudden intolerable changes in materials? temperature. thermally insulating cavity lining is particularly required when a metallic filling, such as amalgam is used. However, if the remaining dentin thickness is more than 2 mm, using only a cavity liner is sufficient.  Cavity base materials may be required to form a protective barrier against potential chemical irritants present in some filling materials. Phosphoric acid in silicate materials, and acrylic monomers in some resin-based materials, are two such potential irritants and their monomers shouldn’t reach the pulp due to their irritant nature.  It should protect the pulp from electrical and galvanic currents. Restorations made of different metals in the mouth create a current as saliva acts as a conductor. This current is called galvanic current and is harmful to the pulp.  It must be resistant to chewing pressures. During the restoration, when an incompletely hardened base material is removed, the restoration will come into contact with the tooth and establish a relationship with the pulp. Again, in cases of breakage and cracking, the sealing feature is impaired.  It should be radiopaque. Thus, its borders can be determined on radiographs.  It must provide adhesion to the permanent filling material placed on it and the tooth.  It should have sufficient working time and harden quickly at mouth temperature.  POWDER Zinc oxide Magnesium oxide Bismuth oxide, silica Zinc Phosphate Cement  LIQUID  Ortho-phosphoric acid  Water  When the alkaline zinc oxide powder is incorporated in the acidic liquid an exothermic acid-base reaction ensues.  It is acidic (pH: 3.5) when first mixed, and this property decreases within 1 hour.  Provides complete neutralization in 24 hours  Since its surface breaks and wears out very quickly, it is easily exposed to plaque accumulation. For this reason, it is not preferred as a temporary filling.   It hardens suddenly.  It provides sufficient ADVANTAGE clinical resistance even at S a low powder/liquid ratio.  It can be easily manipulated.   Pulpal irritation  Lack of antibacterial action DISADVANTAGES  Brittleness  Lack of adhesion  Solubility in oral fluids   Temporary sealing of cavities in permanent teeth,  Sealing of cavities in deciduous teeth that are close to falling out,  In cavities of both deciduous and permanent teeth, as a base material, it ensures the permanent filling sits INDICATION on a solid foundation and plays a role in stress distribution. S  Used in the bonding of orthodontic bands,  In the bonding of crowns, bridges, and inlays,  It is used in the restoration of decayed teeth prior to crown-bridge fabrication (also in the correction of block-out retentions).   It is contraindicated for teeth with little dentin tissue under the cavity, that is, teeth with deep caries. The orthophosphoric acid it contains is irritating to the CONTRAINDICATIO pulp. However, it is suitable for use if a pulp-friendly material NS is applied underneath.  If it is to be used as a temporary filling material, it may be irritating to the gums in cases where the cavity extends below the gums.   P/L ratio is according to manufacturer instruction. Usually for cavity lining putty like consistency; while for the luting more fluid mix required to have adequate flow.  Low P/L……. high acidity and week mix ……….irritation to pulp.  High P/L………….. thick mix …………..decrease setting time…….insufficient working time.  Powder is divided into increments that vary in size. The Manipulatio powder must be added to the liquid in very small increments. Cement must be spatulated slowly over a wide area of a cool, dry, thick glass slab to dissipate the n heat so we have good working time and delay the set slightly, more powder incorporation will increase strength.  To prevent adhesion to the spatula, the spatula may be dipped in powder.  It should first be applied as a small piece to the cavity, and the occlusal wall and axial wall should be coated with cement. No cement residue should be left on the walls and steps.  Working time is 2-3 minutes.  The key considerations for mixing are summarized as follows: 1.The glass slab and spatula must be clean. 2.The glass slab should not be warm. 3.The mixing should proceed from powder to liquid. 4.The powder should not be added to the liquid all at once, as this allows the desired consistency to be achieved. 5.The cap of the cement liquid should be immediately closed. The cavity should be clean and dry, and the cement should be placed in the cavity using dry and clean instruments.  Powder Fluoroaluminasilicat e glass Aluminium oxide Glass Calcium fluoride Aluminium fluoride Ionomer Cilicium oxide Cement  Liquid  Polyacrylic acid  Tartaric acid  Taconic acid  distilled water   GIC is classified based on application as follows: Type I - Luting cement used for cementation of Classificatio crowns and bridges Type II - Restorative cement used for aesthetic n of GIC fillings Type III – GIC used as liners and bases Type 1 (luting) Type 3 (pit and fissure sealant) Type 2 (filling)  Their adhesion to the teeth is achieved partly mechanically and partly chemically, and they have fluoride- release properties.  If the distance to the pulp is less than 0.5 mm, it is necessary to protect the dentin surface with a calcium hydroxide primer made of glass ionomer material.  Chemical bonding to the tooth structure Caries preventive action ADVANTAGE Thermal compatibility with S tooth structure Mild pulp response Tooth-colored restorative material  Poor mechanical properties, eg, low compressive strength, low abrasion resistance, and fracture resistance, make its use restricted to low stress- bearing areas DISADVANTAG Poor esthetics due to lack of ES translucency Moisture sensitive while setting  The longevity of glass ionomer cement restorations is affected by occlusal forces, porosities in set cement, desiccation or water absorption during initial setting, and use of the mixed cement after the loss of gloss. Furthermore, larger GIC particles decrease the wear rate; the cement's solubility depends on the amount of cement at the margins.   In high-caries-risk patients due to the fluoride release.  Restorations of decidious teeth  Root caries  Cervical erosion and abrasion  Restoration of class III INDICATION and class V carious lesions, and tunnel S restorations, and may also be combined with resin composite in the laminate or ‘sandwich' technique.  luting of indirect restorations (metal and metal-ceramic) post and core and orthodontic bands and brackets   The powder and liquid are used in the proportions recommended by the manufacturer. The powder is divided into two equal increments. MANIPULATIO  The liquid is dispensed later to prevent increased viscosity by water loss on N environmental exposure.  Powder and liquid should be mixed immediately within 20-30 seconds.  Application time is 2-3 minutes.  1.Cleaning: A pumice slurry should be applied to the tooth surface using a prophy cup. 2.Conditioning of tooth: after rinsing and drying the tooth, 10% polyacrylic acid is applied for 10 seconds to increase the surface energy and wettability of the tooth, which improves chemical bonding. 3.Placement of restoration: the mixed GIC is carried to the cavity with the help of a cement carrier and adapted using a condenser. Care is necessary to avoid the cement sticking RESTORATIO to the spatula as it is hard to remove. To prevent adhesion to the spatula, the spatula may be dipped in alcohol. N 4.Protection of the cement: the setting cement should be covered by a matrix band during the initial setting and by varnish, cocoa butter, or vaseline after the initial set because GIC is moisture sensitive during the first 24 hours of setting. 5.Finishing and polishing: initial finishing includes the removal of gross excess with a sharp hand instrument. Final finishing is done after 24 hours.   Hybrid ionomer or resin-modified glass ionomer cement was developed by the addition of resins (bisphenol A-glycidyl RESIN dimethacrylate or urethane MODIFIED dimethacrylate) and photoinitiators to the GIC conventional glass ionomer.  It is a hybrid material between traditional glass ionomer cement and resin composite.  Composition of Resin-modified Glass Ionomer Cement Powder: fluoroaluminosilicate glass, light, and chemical initiators Liquid: aqueous solution of polyacrylic acid and 10% 2-HEMA   Hybrid ionomers are set by a dual-reaction curing mechanism consisting of acid-base and polymerization reactions. When the liquid and powder are mixed, the polymerization reaction starts with chemical or light-mediated Setting initiation. This set resin protects the ongoing acid-base setting reaction in the cement matrix Reaction from moisture contamination. This phenomenon is known as the "umbrella effect," reducing the early moisture sensitivity of GIC and providing greater initial strength. The slowly proceeding acid-base reaction determines the final strength.   Polyacrylic acid molecules are large so it is difficult for them to penetrate the dentinal tubules.  It is biocompatible  The hybrid ionomer bonds chemically to the tooth structure. However, the ionic activity is reduced due to the presence of resin. This results in a lesser bonding tendency.  The fluoride release is slightly lesser than conventional GIC. ADVANTAGE The formation of complex fluoride derivatives in a reaction with polyacrylic acid influences the release of fluoride. It may also be affected by the type and amount of the resin used. The initial S pH of the hybrid ionomer (pH=3.5) is higher than conventional GIC (pH=2), which reduces pulp irritation.  Wear resistance, fracture toughness, flexural, and diametral tensile strength of hybrid ionomer are superior to conventional GIC, whereas compressive strength is inferior. The translucency of the hybrid ionomer is superior to conventional GIC. It exhibits a slight tendency for shrinkage due to the polymerization of the resin component.  It has easy manipulation and a long working time.   Mechanical durability is lower DISADVANTAGE than composite S  Aesthetics are less than composite  Class V restorations due to reduced moisture sensitivity Restoration of non- carious cervical lesions INDICATION Class I and II restorations in S primary teeth A liner or base under composite restorations (sandwich technique)   It is polymerized by light. Incremental layering techniques can be applied to reduce MANIPULATIO polymerization shrinkage. N  Although polishing can be done immediately, it is more appropriate to wait 24 hours.