Prosthodontics-Tooth Preparation for full veneer PDF

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Prostho Lecture FULL VENEER CROWN 1. Complete Cast Crown or Full Metal Crown often used on single posterior teeth as retainer for an FPD. Indications: a. Extensive destruction from caries or trauma b. Endodontically treated teeth c. Existing restoration d. Necessity for maximum retention and strengt...

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Prostho Lecture

FULL VENEER CROWN 1. Complete Cast Crown or Full Metal Crown - often used on single posterior teeth as retainer for an FPD. - Indications: a. Extensive destruction from caries or trauma b. Endodontically treated teeth c. Existing restoration d. Necessity for maximum retention and strength e. To provide contours to receive a removable appliance f. Recontouring of axial surfaces (minor corrections of malinclination) g. Correction of occlusal plane. - Contraindications a. Less than maximum retention necessary b. Esthetics - Advantages: a. Strong b. High retentive qualities - Disadvantages: a. Removal of large amount of tooth structure b. Adverse effect on tissue c. Vitality testing not readily feasible d. Display of metal 2. Metal-Ceramic Crown - consists of a complete-coverage cast metal crown that is veneered/covered with a layer of fused porcelain to mimic the appearance of a natural tooth. - Indications: a. a. Esthetics b. If porcelain jacket crown is contraindicated c. Gingival involvement - Contraindications: a. Large pulp chamber b. Intact buccal wall c. When more conservative retainer is technically feasible - Advantage: a. Superior esthetics as compared to cast gold restoration. - Disadvantages: a. Removal of substantial tooth structure b. Subject to fracture because porcelain is brittle c. Difficult to obtain accurate occlusion in glazed porcelain d. Shade selection can be difficult e. Inferior esthetics compared to porcelain jacket crown f. Expensive

3. All Ceramic Crown - resembles natural tooth structure in terms of color and translucency. - Indications: a. High esthetic requirement b. Considerable proximal caries c. Incisal edge reasonably intact d. Endodontically treated teeth with post and cores e. Favorable distribution of occlusal load - Contraindications: a. When superior strength is needed and metal-ceramic crown more appropriate b. Significant caries with insufficient coronal tooth structure for support c. Thin teeth faciolingually d. Unfavorable distribution of occlusal load - Advantages: a. Esthetically unsurpassed b. Good tissue response even for subgingival margins c. Slightly more conservative of facial wall - Disadvantages: a. Reduced strength compared to metal-ceramic b. Proper preparation is extremely critical c. Among least conservative preparations d. Brittle nature of material e. Can be used as single restoration only f. More expensive ●

Zirconia crowns - are made of zirconia or zirconium oxide, and are very tough and durable in nature. Since such crowns have several advantages over traditional metal and porcelain dental implants. - Advantages: a. Natural look: Zirconia crowns can be translucent enough to blend with other teeth and give a natural look. What’s more, if bonded to the teeth rather than being cemented with conventional dental cement, these crowns won’t display a black line at the gum line. b. Strength: Where porcelain crowns are prone to chipping, zirconia crowns are almost indestructible. In fact, these crowns can be up to five times stronger as compared to their porcelain/metal counterparts. c. Durability: Unlike crowns of other materials that may typically last for around 10 years or so, those made of zirconia are likely to last a lifetime. d. Less sacrifice of healthy teeth: Since zirconia crowns can offer superior strength in less volume than crowns made of other materials, they can be made to fit even when not much space is available for porcelain build up.

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e. Biocompatible: Zirconia is completely compatible with the human body. Since it is inert, and the body does not reject zirconia, you need not worry about facing allergies or unfavorable reactions. f. Corrosion resistant: Zirconia crowns are resistant to corrosion, which adds to their longevity factor. g. Less labor-intensive: Since more of the present tooth is retained, nominal preparation is required for fitting these crowns as compared to metal or porcelain crowns. h. Cost-effective: Zirconia crowns are considerably cheaper than porcelain crowns, and cost almost the same as gold based metal-porcelain crowns. However, the long list of benefits that they bring to the table make them more cost-effective than crowns made of other materials. Disadvantages: a. Abrasive effect: The toughness of zirconia crowns can have an abrasive quality, which causes friction against the root of the affected tooth as well as with other teeth. b. Decay under the crown: Though these crowns are meant to last a lifetime, the decay underneath the crown may cause them to loosen and fall.

Gold - Gold has been used for a long time in dentistry and for good reason. All gold restorations are alloys, meaning that the gold is mixed with other metals to give it added strength. Pure gold would simply be too soft to be usable in the mouth. The best gold restorations are a high-noble alloy, meaning that at least 60% of the crown is made up of gold and other precious metals like platinum, palladium, and silver that are noted for their low-reactivity with human tissue and resistance to corrosion and oxidation. Advantages: - Extremely durable and long lasting Gentle on opposing teeth Strong even when thin, allowing for more conservative tooth preparation and the preservation of more healthy tooth structure Cementation process is less sensitive for many patients than porcelain bonding techniques. Classification of Alloys for Fixed Prosthodontics (Revised American Dental Association) - The American Dental Association revised the classification system for alloys for fixed prosthodontics; and now includes a fourth group, which comprises titanium and titanium alloys. The classifications are based solely on gold, noble metal, or titanium content. Hundreds of dental alloys are commercially available, and appropriate testing is necessary to characterize the properties, safety, and efficacy. High-Noble Alloys: - The high-noble alloys are gold based and contain a minimum of 60% by weight of noble elements; at least 40% is gold. - There are three systems in this class: a. gold-platinum-palladium (Au-Pt-Pd), b. gold-palladium-silver (Au-Pd-Ag), c. gold-palladium (Au-Pd), in the historical -order of their development.

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Noble Alloys: - Noble Alloys have a minimum of 25% by weight of noble metal, with no requirement for gold percentage, and are palladium based. - There are three alloy systems in this class: a. palladium silver (Pd-Ag) b. palladium-copper-gallium (Pd-Cu-Ga) c. palladium-gallium (Pd-Ga), in the historical order of their development. TItanium and Titanium alloy - They have been studied as potential dental alloys. Advantages include excellent biocompatibility and corrosion resistance, which results from the previously noted presence of a thin, adherent, passivating surface layer of titanium dioxide (TiO2). - The low density (4.5 g/cm3) of titanium, in comparison with that of gold or palladium, also results in lighter restorations that are potentially less expensive. Predominantly Base Metal Alloys: - These alloys (sometimes termed non precious) as having less than 25% by weight of noble metal with no requirement for gold. Of these alloys. Most used for fixed prosthodontics are nickel-chromium (Ni-Cr) alloys, but some Cobalt-Chromium (Co-Cr) alloys have been formulated for porcelain application.

PARTIAL VENEER CROWNS - A type of crown that partially covers or veneers the clinical crown. Usually the involved surfaces are the proximal, occlusal and incisal except for laminate veneers wherein the labial, incisal and proximal surfaces are involved. - Types of partial veneers: ● Posterior teeth: 1. Three-quarter crown Restores the occlusal surface and three of the four axial surfaces not including the facial. 2. Modified three quarter crown 3. Seven-eighths crown - They are extensions of the three quarter crown to include a major portion of the facial surface. They are generally indicated for maxillary premolar and molars. Where the mesial surface is sound, but distal surface is extensively damaged by caries. - Indications: a. Sturdy clinical crown of average length or longer b. Intact buccal surface not in need of contour modification and well supported by sound tooth structure c. No conflict between axial relationship of tooth and proposed path of withdrawal of FPD. - Contraindications: a. Short teeth b. High caries index c. Extensive d. Destruction e. Poor alignment f. Bulbous teeth g. Thin teeth - Advantages: a. Conservative of tooth structure b. Easy access to margins c. Less gingival involvement than with complete cast crown d. Verification of seating simple e. Electric vitality test feasible - Disadvantages: a. Slightly less retentive than complete cast crown b. Limited adjustment of path of withdrawal c. Some display of metal ● Anterior teeth: 1. Three-quarter crown - Indications: a. Sturdy clinical crown of average length or longer

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Intact labial surface that is not in need of contour modification and that is supported with sound tooth structure. c. No discrepancy between axial relationship of tooth and proposed path of withdrawal of FPD - Contraindications: a. Short teeth b. Non vital teeth c. High caries index d. Extensive destruction e. Poor alignment with path of withdrawal of FPD f. Cervical caries g. Bulbous teeth h. Thin teeth - Advantages: a. Conservation of tooth structure b. Easy access to margins for finishing (dentist) and cleaning (patient) c. Less gingival involvement than with complete cast crown d. Easy escape of cement and good seating e. Easy verification of complete seating f. Electric vitality test feasible - Disadvantages: a. Slightly less retentive than complete cast crown b. Limited adjustment of path of insertion c. Some display of metal d. Not indicated on non vital teeth 2. Pinledge - Indication: a. Undamaged anterior teeth in caries- free mouth b. A high esthetic requirement c. Where proximal grooves are impossible to prepare d. To alter the lingual contour of max. anterior teeth or to alter occlusion e. Anterior splinting f. To alter the lingual contour of max. anterior teeth or to alter occlusion - Contraindications: a. Large pulps b. Thin teeth c. Non vital teeth d. Carious involvement e. Problems with proposed path of withdrawal of FPD

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Advantages: a. Minimal tooth reduction. b. Minimal margin length c. Minimum gingival involvement. d. Optimum access for margin finishing and hygiene e. Adequate retention f. Excellent esthetics - Disadvantages: a. Less retentive than complete coverage b. Alignment can prove difficult c. Technically demanding d. Not usable on non vital teeth 3. Laminated veneer - When porcelain laminate veneers are properly prepared, produced, and finished, an increase of the crevicular fluid decreases the plaque index, and one can see the healthy tissue around the biologically integrated porcelain laminate veneers. - Indication: a. Discoloration (e.g. dental fluorosis or mottled enamel/Tetracycline stain) b. Diastema closure and lengthening of crown cervicoincisally/widening mesiodistally. c. Fracture involving proximoincisal surface. d. Masking tooth defects ex. Peg shaped incisors e. lengthening of crown cervicoincisally for esthetics - Contraindications: a. High caries index b. Poor plaque control c. Extensive existing large restorations or endodontically treated with little remaining tooth structure. d. Tooth wear due to BRUXISM e. Short teeth f. Teeth with insufficient or inadequate enamel for sufficient retention (ex. Severe abrasion) g. Patients with oral habits causing excessive stress on the restoration(ex. nail biting/pencil biting) - Advantages: a. Superior esthetics b. Wear and stain resistant c. Excellent long durability –abrasion resistant / color-stable, excellent resistance to fluid retention. d. Inherent porcelain strength – exhibits excellent compressive, tensile and shear strength

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e. Minimal tooth reduction – 0.3-0.5 mm only 0.5mm only f. Soft tissue compatibility – biocompatible w/ soft tissues Disadvantages: a. Increased tooth contour b. Expensive c. Time – multiple visits are required d. Fragility – during try-in and cementation e. Lack of repair ability – difficult, if not impossible, to repair. f. Difficulty in color matching g. Irreversibility – unlike bleaching, requires teeth reduction. h. Inability to trial cement the restoration

1. When there is a need for maximum strength and retention all metal crown is the

best choice. In all metal crown there is more reduction needed than the porcelain fused to metal crown. The first statement is correct and the second statement is incorrect

2. All ceramic crown gives the excellent esthetic values. It is contrainidcated when there is in close contact with the natural teeth. Both statements are correct 3. Both the seven-eight crown and three-quarter crown are contraindicated for teeth

that are bulbous and endodontically treated. Both of them have a gingival margin called shoulder type. The first statement is correct and the second statement is incorrect 4. The labial reduction in PFM is 0.5mm to 1.5mm while in laminates is 0.5 to

1.0mm. PFM have chamfer gingival margin labially like in the laminates. Both statements are incorrect 5. Crown that have difficulty in shade selectiion or shade matching. Laminate and

PFM. porcelain fused to metal crowN and laminates 6. The following are advantages of full veneer crown over partial veneer crown. More retentive and Can be indicated for both vital and non vital tooth 7. The following are contraindication for the PFM crown EXCEPT. Accurate occlusion in glazed porcelain is difficult to obtain 8. In a seven eight crown the MESIOBUCCAL surface is uncover with metal,

9. Porcelain fused to metal crown has an inferior esthetics in comparison with all-ceramic crown. 10. All ceramic crown has reduced strength in comparison with metal-ceramic crown.

1. The present of TERTIARY DENTIN reduces dentin permeability

2. 3. 4. 5.

Periodontal ligament is attached into the CEMENTUM DENTIN is the main bulk of the tooth During oral prophylaxis, a thin layer of CEMENTUM is removed. RESORPTION is the common complication that occurs when there is an excessive load exerted in fixed prosthesis. 6. PERIODONTAL LIGAMENTS act as shock absorber. 7. The objectives of treatment planning are CORRECTION OF EXISTING DISEASE, PREVENTION OF FURTHER DISEASE, RESTORATION OF FUNCTION, IMPROVEMENT OF APPEARANCE. 8. PATIENT'S HEALTH EDUCATION is the first treatment procedure.

9. Receded gums recover once the cause of trauma is removed. FALSE

Prosthodontics Lecture

Module 4 Lesson 1: Principle of Tooth Preparation The principles of tooth preparation may be divided into Three Broad Categories: 1. Biological considerations- which affects the health of the oral tissue. 2. Mechanical considerations- which affects the integrity and durability of the restoration. 3. Esthetic considerations- which affects the appearance of the patient. The design of the preparation for a cast restoration and execution of that design are governed by Five Principles: 1. Preservation of the tooth structure: - In addition to replacing the lost tooth structure, a restoration must preserve remaining tooth structure. - In some cases may require that limited amounts of sound tooth structure be removed to prevent subsequent uncontrolled loss of larger quantities of tooth structure. - Know the correct amount of reduction on each tooth surface to avoid over reduction which results to: a. Reduce retention b. Reduce resistance c. Increase hypersensitivity d. Pulp inflammation and necrosis e. Tooth fracture 2. Retention and Resistance: - Retention: Prevents the removal of the restoration along the path of insertion or long axis of the tooth preparation. - Resistance: Prevents dislodging of the restoration by forces directed in apical or oblique direction and prevents any movement of the restoration under occlusal force. a. Taper - Axial walls must taper slightly to permit the restoration to sit, i.e. 2 opposing external walls must gradually converge or 2 opposing internal surfaces must diverge occlusally. ● The more nearly parallel the opposing walls of a preparation, the greater the retention but the parallel walls are impossible to create in the mouth without producing undercuts. ● The greater surface area of a preparation the greater its retention, therefore, preparation on larger teeth are more retentive than on small teeth. - If parallel, forces resisted by the tooth preparation. - If tapered, forces transmitted through the porcelain due to insufficient support from the preparation. - The greater the surface area, the more retentive.

b. Freedom of displacement (Path of withdrawal) - Limiting the freedom of displacement from torquing/twisting forces in a horizontal plane increases the resistance of restoration. c. Length - Occlusogingival length is an important factor in bothe retention and resistance. - Longer preparation will have more surface area, therefore, more retentive. d. Substitution of internal features - The basic unit of retention for a cemented restoration is 2 opposing axial walls with a minimal taper. - Internal features such as grooves, box form, and pinhole are interchangeable and can be substituted for an axial wall or for each other. - Substitution is important, since conditions often preclude making an ideal preparation. e. Path of insertion - An imaginary line along which the restoration will be placed onto or removed from the preparation. - Preparation must be viewed with one eye closed. - For the preparation to be surveyed in the mouth, where direct vision is rarely possible, a mouth mirror is used, it is held at an angle approximately ½ inch above the preparation and the image is viewed with one eye. 3. Structural durability: - A restoration must contain a bulk of material that is adequate to withstand the forces of occlusion. This bulk must be confined to the space created by the tooth preparation. Only in this way can the occlusion on the restoration be harmonious and the axial contours normal, preventing periodontal problems around the restoration. a. Occlusal reduction: - One of the most important features for providing adequate bulk of material and strength to the restoration is occlusal clearance. - Inadequate clearance makes restoration weaker, inadequate reduction under the anatomic grooves of the occlusal surface will not provide adequate space to allow good functional morphology. - Occlusal reduction should reproduce basic inclined planes rather than being cut as one flat plane. b. Functional cusp bevel - Wide bevel on the lingual inclines of max. lingual cusps and the buccal inclines of mand. buccal cusps provide space for an adequate bulk of metal in an area of heavy occlusal contact.

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Bevels have been advocated as a means of diminishing marginal discrepancy. They resist fracture and chipping. - Functional cusps are the cusps who are in contact with the opposing tooth. c. Axial reduction - Plays an important role in securing space for an adequate thickness of restorative material. - On the cusp bevel convergence buccolingually should be observed. - And on the occlusal table which is the internal walls should be diverging. 4. Marginal Integrity - Margins should be adapted to the cavosurface line of the preparation. The configuration of the prepared finish line dictates the shape and bulk of restorative material in the margin of the restoration. - It can also affect both marginal adaptation and the degree of seating of the restoration. - CFL should not be too thick nor too thin. - Advantages (a), Disadvantages (d) and Indications (i) of different margin designs: 1. Feather edge: a- conservative of tooth structure d- does not provide sufficient bulk i- not recommended 2. Chiseled edge a- conservative of tooth structure d- location of tooth margin difficult to control i- occasionally on tilted teeth 3. Bevel a- removes unsupported enamel, allows finishing of metal d- extend preparation into...