Lesson 8 & 9 Flashcards by Love Dog

Q

metal-ceramic restoration, otherwise known as _____

A

PFM restoration (porcelain fused to metal)

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Q

one of the least conservative of tooth structures:

______ because incisal and occlusal surfaces are
always subjected to forces

A

thicker metal

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Q

one of the least conservative of tooth structures:

_______ maximum for incisal and _____ for molars

A

2 mm, 1.5 mm

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Q

porcelain fuse at temperatures of ____ and gold alloys melt
at this temperature

A

960 C

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Q

gold alloys melt
at this temperature

A

960 C

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Q

is a major consideration in the
fabrication of metal ceramic restoration

A

special alloy

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Q

FACTORS IN TOOTH PREPARATION

A

Biologic
Mechanical
Esthetic

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Q

Conservation of tooth structure

A. Biologic
B. Mechanical
C. Esthetic

A

A

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Q

Avoidance of overcontouring

A. Biologic
B. Mechanical
C. Esthetic

A

A

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Q

Supragingival margins

A. Biologic
B. Mechanical
C. Esthetic

A

A

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Q

Harmonious occlusion

A. Biologic
B. Mechanical
C. Esthetic

A

A

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Q

Protection againts tooth fracture

A. Biologic
B. Mechanical
C. Esthetic

A

A

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Q

Retention form, resistance form, deformation

A. Biologic
B. Mechanical
C. Esthetic

A

B

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Q

Minimum display of metal

A. Biologic
B. Mechanical
C. Esthetic

A

C

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Q

Maximum thickness of porcelain

A. Biologic
B. Mechanical
C. Esthetic

A

C

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Q

Porcelain occlusal surfaces, subgingival margins

A. Biologic
B. Mechanical
C. Esthetic

A

C

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Q

→ teeth that require complete coverage

→ gingival involvement
→ in conjunction with post & crown

A

METAL-CERAMIC CROWN PREPARATION

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Q

can be modified for cingulum & occlusal restorations

A

METAL-CERAMIC CROWN PREPARATION

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Q

→ if all-ceramic crown is contraindicated

o not efficacious for long spans

A

METAL-CERAMIC CROWN PREPARATION

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Q

CONTRAINDICATIONS

large pulp chamber

intact buccal wall

presence of active caries

→ untreated periodontal disease
→ when more conservative retainer is technically feasible

A

METAL-CERAMIC CROWN PREPARATION

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Q

ADVANTAGES

→ strength of cast metal with the esthetics of ceramics
→ retentive qualities are excellent
→ easy correction of axial form
→ preparation is much less demanding than for partial-coverage
retainers

A

METAL-CERAMIC CROWN PREPARATION

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Q

DISADVANTAGES
→ requires significant tooth reduction
→ difficulty obtaining accurate occlusion in glazed porcelain → shade selection can be difficult
→ inferior esthetics in comparison with all-ceramic crown
→ subject to brittle fracture
→ increases potential for periodontal disease
→ many procedural steps are required

A

METAL-CERAMIC CROWN PREPARATION

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Q

RECOMMENDED PREPARATION for
ANTERIOR:

Labially

A

1.5 mm

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Q

RECOMMENDED PREPARATION for
ANTERIOR:

Incisally

A

2 mm

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STEP-BY-STEP PROCEDURE FOR METAL-CERAMIC TOOTH PREPARATION

(1) Depth Grooves (2) Incisal (Occlusal) Reduction (3) Labial (Buccal) Reduction (4) Proximal Cut (5) Lingual Reduction (6) Finishing (7) Smoothing and Finishing

DEPTH GROOVES place (3) depth grooves:

o center of facial surface o one each in mesiofacial and distofacial line angles

DEPTH GROOVES placed in (2) planes:

Cervical Portion Incisal (Occlusal) Portion

parallels the long axis of the tooth

Cervical Portion (DEPTH GROOVES)

follows the normal facial contour (1.8 mm)

Incisal (Occlusal) Portion (DEPTH GROOVES)

FACIAL REDUCTION facial reduction in the _____ & ____

cervical and incisal planes

determines the path of placement of the completed restoration

Cervical Plane (FACIAL REDUCTION)

provides the space needed for the porcelain veneer

Incisal (Occlusal) Plane FACIAL REDUCTION

achieve the necessary. ____ mm clearance on the incisal depth grooves

2 mm

place three depth grooves (1.8 mm deep) in the incisal edge of an anterior tooth A. Anterior Tooth B. Posterior Tooth

A

clearance must be a minimum of 2 mm; cusp inclines 1.5 to 2 mm of clearance in intercuspal tapered A. Anterior Tooth B. Posterior Tooth

B

allow 2 mm of clearance for adequate material thickness to allow translucency in the completed restoration

INCISAL (OCCLUSAL) REDUCTION

in posterior teeth: o may still be restorable with less reduction because esthetics is not as critical

INCISAL (OCCLUSAL) REDUCTION

caution: o excessive occlusal reduction will shorten the axial preparation walls and thus is a common cause of inadequacies in retention and resistance form in the completed preparation o loss of retention form can be especially problematic on anterior teeth (on which, because of tooth form, most of the retention is derived from the proximal walls)

INCISAL (OCCLUSAL) REDUCTION

→ use a tapered, round-ended diamond bur → 1.2 - 1.5 mm of reduction for translucency in the restoration → greater thickness of alloy at incisal area than any other tooth surface → bur position at 45 degrees linguo-incisally → reduce half of the incisla area at a time → reduce one cusp at a time

INCISAL (OCCLUSAL) REDUCTION

FACIAL REDUCTION two plane reduction: Cervical Plane- Incisal Plane -

1.0 mm; 1⁄3, 1.3 mm; 2⁄3

→ 0.5 mm apical to crest of free gingiva → reduce with the bur in oblique position → tenon system

FACIAL REDUCTION

→ recommended: o 6 degree taper between opposing axial walls → shoulder margin at 1 mm thick → parallel walls with another abutment → avoid hitting adjacent tooth → shoulder margin below the contact point → use flat-end diamond bur

PROXIMAL CUT OR REDUCTION

Size of Linguofacial Wall Reduction: Chamfer Margin Supragingival

0.5 mm

Size of Linguofacial Wall Reduction: Axial Wall Height

1.5 mm

Size of Lingual Fossa Reduction: Centric Contacts on Metal

1 mm thickness

Size of Linguo-axial Wall: Height for path of placement and anti-rotation

1.5 mm

Size of Linguo-axial Wall: Use round-ended tapered diamond bur and submerge halfway into the tooth structure to create chamfer margin Size of the width?

0.5 - 0.6 mm width

Size of Linguo-axial Wall: Use flame-shaped or football shaped diamond bur in preparing the lingual surface of anterior teeth

1 mm thickness

The margin must provide distinct resistance to vertical displacement of the tip of a periodontal probe or an explorer and it must be smooth and continuous circumferentially.

FINISHING LINE

FINISHING LINE shoulder finish line should be_______ degrees

90-120

FINISHING LINE use ___ in remaining unsupported enamel

chisel

FINISHING LINE _____ finish line in lingual

chamfer

FINISHING LINE avoid “ ____” of the chamfer margin

lipping

FINISHING LINE → controlled tissue displacement can be helpful when the margin is finished with a _____ or another rotary instrument → avoid undercuts → round-off internal line angles, incisal and occlusal margins → taper and parallelism

fine-grit diamond

(1) Platinum foil matrix adapted to a die (2) Hot pressing/heat-pressed (3) Sip-casting (4) Milling

TECHNIQUES IN FABRICATION FOR ALL-CERAMIC RESTORATIONS

ZIRCONIA another name

SINTERING-MILLING

E-MAX another name

HEAT-PRESSED

→ three times stronger than porcelain

ZIRCONIA (SINTERING-MILLING)

→ can withstand wear and tear without chipping → tolerate forces of mastication and bruxism → less stress and damage on opposing pieces

ZIRCONIA (SINTERING-MILLING)

made from lithium disilicate ceramic

E-MAX

ideal for crowns

E-MAX (HEAT-PRESSED)

→ more translucent compared to zirconia → 10-15 years (fracture)

E-MAX (HEAT-PRESSED)

→ high esthetic requirement → considerable proximal or facial caries → incisal edge reasonably intact o to support the restoration, particularly in the incisal area, where porcelain thickness must not exceed 2 mm o otherwise, the brittle material will fail → endodontically treated teeth with posts and cores → favorable distribution of occlusal load because of the relative weakness of the restoration

INDICATIONS for ALL-CERAMIC CROWN PREPARATION

→ when a more conservative restoration can be used → when superior strength is warranted and metal-ceramic crown is more appropriate → extensive caries → insufficient coronal tooth structure for support → thin teeth facio-lingually → unfavorable distribution of occlusal load → bruxism → teeth with short clinical crowns o they do not offer adequate support for all-ceramic crowns

CONTRAINDICATIONS for ALL-CERAMIC CROWN PREPARATION

→ esthetically unsurpassed; excellent translucency → good tissue response even for subgingival margins → slightly more conservative of facial wall than metal-ceramic restorations

ADVANTAGES in ALL-CERAMIC CROWN PREPARATION

→ reduced strength in comparison with metal-ceramic crown proper preparation extremely crucial → among least conservative preparations → brittle nature of material → can be used only as single restoration

DISADVANTAGES in ALL-CERAMIC CROWN PREPARATION

centric contacts are best confined to the middle third of the lingual surface

ALL-CERAMIC CROWN OCCLUSION

achieved by restricting the taper of proximal walls

Retention Form

wing-type preparation offers more resistance than wingless counterpart (crown length)

Resistance Form

should exhibit two plane reduction

Esthetic Zone

cervical plane is 1⁄3 of preparation height

Anteriors

Shoulder margin degree?

90-120 degree (hatchet/chisel)

Premolars and Molars cervical and occlusal plane often ______ each other in height

approximate

____ should be avoided as it often leads to overreduction

Undercut

should be avoided because this may lead to pulpal exposure

Excessive Convergence

0.5 mm; should be smooth and continuous and provide distinct resistance to vertical displacement

Chamfer Margin

must be smooth and continuous circumferentially

Finishing Margin

Line Angles and Internal Line Angles should be _____

rounded

True or false all-ceramic restoration are most esthetically pleasing because of the absence of underlying metals to block light transmission and it resembles natural tooth better in terms of color and translucency

True

chief disadvantage is fracture susceptibility but lessened by use of resin-bonded technique and higher strength ceramics

ALL-CERAMIC RESTORATIONS

one of the least conservative of tooth structures: ____ mm maximum for incisal and _____ mm for molars

2 mm, 1.5 mm