Presentation 10.pptx the metal ceramic crown preparation

Fixed prosthodontics

1. THE METAL CERAMIC CROWN PREPARATION SUBMITTED TO: DR.FAHAD PREPARED BY: KAMLA KHAN

2. WHAT IS METAL CERAMIC RESTORATION? .The restoration consists of a complete coverage of a cast metal crown or a substructure that is veneered with a layer of fused porcelain(a translucent ceramic) to mimic the appearance of a natural tooth.The aim is to merge the excellent strength of metal and good esthetics of porcelin to get desired result.

3. INDICATIONS: The metal ceramic crown is indicated on teeth that required complete coverage and for which significant esthetic demands are placed. Preferred choice for posteriortooth replacement due to great strength. Used for single tooth restoration where underlying tooth structure is compromised due to decay or fracture and can be used when one or more teeth have to be replaced.

4. CONTRAINDICATIONS: Some patients may have allergies to metals. Patients with parafunctional habits like teeth grinding or clenching may put accessive stress on restoration. Patient with active caries or untreated periodontal disease. In young patients with large pulp chambers ,the PFM crown is contraindicated due to high risk of pulp exposure.

5. ADVANTAGES: The restoration combines a good strength of cast metal with the aesthetics of all ceramic crowns. The underlying principle is to reinforce a brittle, more cosmetically pleasing material through support derived from a stronger substructure metal. Retentive qualities are excellent because all axial walls are included in the preparation. Easily withstand the occlusal load on posterior teeth.

6. DISADVANTAGES: The preparation for a metal ceramic crown requires significant tooth reduction to provide sufficient space for the restorative materials. To achieve better esthetics ,the facial margin of an anterior restoration is often placed subgingivally which increases the potential for periodontal disease. In comparison with an all ceramic restoration, the metal ceramic crown may have slightly inferior esthetics, but it can be used in high stress bearing areas.

7. TOOTH PREPARATION: ARMAMENTARIUM: The instruments needed to prepare teeth for a metal ceramic crown include, Round tipped rotary diamonds for bulk reduction and finishing. Football shape diamond for lingual reduction on anterior teeth. Flat ended tapered diamond for shoulder preparation. Finishing stones. Explorer and periodontal probe.

8. STEPS OF CROWN PREPARATION The preparation involves five major steps Guiding grooves Incisal or occlusal reduction Labial or buccal reduction Axial reduction of proximal and lingual surfaces Final finishing of all prepared surfaces.

9. Guiding grooves Place 3 depth grooves one in the centre of facial surface and one each in the approximate locations of mesiofacial and distofacial line angles. Perform facial reduction cervically and incisally. The grooves should be 1.3mm deep.

10. INCISAL OR OCCLUSAL REDUCTION Place 3 grooves about 1.8mm deep in incisal edge of anterior tooth. This provide the needed reduction of 2mm with finishing. This will allow for adequate material thickness. Anterior teeth incisal reduction= 2mm Posterior teeth occlusal reduction=1.5mm

11. LABIAL OR BUCCAL REDUCTION .For pleasing esthetics an anterior tooth should be reduced by atleast 1.2mm on its labial surface,although 1.5mm is preferable size. .The resting shoulder approximately 1mm wide and extend well into proximal embrasure when viewed from incisal view. .Supragingival margin is preferred in posterior teeth and subgingival in anterior teeth because of esthetic concern.

12. AXIAL (PROXIMAL AND LINGUAL) Reduce the proximoaxial and linguoaxial surfaces, these walls slightly converge from cervical to incisal. A taper of 6 degree is measured as the angle between opposing walls. Lingual surface is reduces by 1mm. The proximal contacts are reduced and a 0.5mm width of lingual chamfer is created.

13. FINISHING Margins must be smooth,glass like finish and continuous circumferentially. Line angles should be rounded. A shoulder with 90 degree cavosurface is recommended which gives proper support to porcelin.

14. References Contemporary Fixed Prosthodontics : . Rosenstiel . Land . Fujimoto Video : Metal ceramic Crown Preparation " for dental students"

15. THANK YOU