ALL CERAMIC RESTORATIONS dr shabeel pn ALL CERAMIC RESTORATIONS

Complete ceramic crown Should have relatively even thickness circumferentially About 1 to 1.5mm thickness needed to create esthetically pleasing restoration

Excellent translucency Good tissue response Advantage Superior esthetic Excellent translucency Good tissue response Conservative reduction of facial surface Appearance of restoration influenced by color of luting agent Disadvantage Reduced strength of restoration Significant tooth reduction Difficulty in obtaining well fitting margin Not effective as retainer for fixed prosthesis Wear observed on functional surface of natural tooth

When more concervative restoration can be used Indication Areas with high esthetic requirement Tooth should be relatively intact with sufficient coronal structure to support the restoration particularly incisal area Centric contact must be in an area where porcelain is supported by tooth structure contraindication When more concervative restoration can be used If occlusal load is unfavourable Contra

Preparation Armamentarium Narrow round tipped tapered diamond Football shaped diamond Finishing stones and carbide Mirrors and periodontal probe Explorer chisels hatchets handpiece

Facial reduction Placing depth orientation groove One depth groove in middle of facial wall and one each in the mesiofacial and distofacial trancitional line angle Depth is 0.8mm to allow finishing Cervical component parallel to path of placement and incisal component parallel to original contour of the tooth Reduction is performed on half at a time

Lingual reduction Football shaped diamond Selected path of placement has been transferred from cervical wall of facial preparation Place depth groove in middle of cingulum wall Margin should follow free gingival crest Should not extent too far subgingivally

Chamfer preparation and finishing 1mm wide smooth continuous and free of any irregularity A 90 degee cavosurface angle is optimal Objective is to direct stress parallel to path of placement A sloping shoulder result unfavourable loading of porcelain Round any remaining sharp line angle to prevent wedging action

Strengthening mechanism of dental ceramic Fabrication defect Created during processing Consist of voids porosity microcrack Surface crack Induced by machining Flaw effectively determines the fracture resistance of restoration

Crystalline reinforcement Introduction of high proportion of crystalline phase A crystalline phase with greater thermal expansion coefficient produce tangential compressive stress near crystal matrix interphase Such tangential stress tends to divert the crack around particle

Chemical strengthening Relies on the exchange of small alkali ions for larger ion bellow the strain point of ceramic This techniqe is diffusion driven and its kinetic are limited by time temperature and ionic radius of exchanging ions

Stress induced transformation Zirconia is monoclinic at room temperature and tetragonal at 1170 degree Stress triggers transformation from tetragonal to monoclinic zirconia This leads to strengthening as a result of increase in grain volume in the vicinity of the crack up

Glazing Addition of surface glaze The principle is formation of low expansion surface layer at a high temperature Self glazing consist of an additional firing in air after original firing without application of a low expansion glaze

Prevention of stress corrosion Baked on metal foil may reduce fracture incidence by reducing moisture exposure to internal surface of ceramic Coating are used also used to reduce stress corrosion of glass ceramic

Selection of all ceramic system Fracture resistance Promising result if the restoration are confined to lower stress anterior teeth Esthetic A knowledge of available ceramic system is needed Marginal adaptation of system is important Translucency of adjacent teeth and discoloration must considered

A more opaque high strength core ceramic system like inceram or procera are not good choice for highly translucent teeth Abrasiveness Potential for abration of opposing tooth particularly in patient with parafunctional habit Low abration material should be concidered

All ceramic partial fixed prosthesis Inceram alumina for anterior fdp Lithium disilicate heatpressed ceramic empress 2 cad cam procera system are also suitable for anterior fdp

All ceramic foundation restoration All ceramic is used as foundation restoration for endodontically treated teeth to overcome esthetic problem associated with metal post and core system

Resin bonded ceramic Performance of all ceramic restoration has been enhanced by use of resin bonding

Half moon fracture of crown is common form of failure it occure in Teeth with edge to edge occlusion When opposing tooth occlude cervical fifth of lingual surface Teeth with short crown Teeth with overshortened preparation