Indirect Midterm (copy)

principles of tooth preparation

principles of tooth preparation

• preservation of remaining sound tooth structure

• tooth reduction to provide necessary space for bulk of restorative material

• geometry of preparation to provide retention and resistance

• margins of tooth and restoration must maintain their integrity

• periodontal health after restoration must be maintained

path of insertion (poi)

• allows for restoration to be placed/removed in the long axis of the tooth

• proper poi and planes of reduction provides space for material

occlusal reduction

should follow cuspal inclines for tooth preservation while providing space for the material

retention

prevents removal of the restoration along the poi or long axis of the tooth preparation

resistance

prevents dislodgment of the restoration by forces directed in an apical or oblique direction and prevents any movement of the restoration under occlusal forces

the essential element of retention is….

two opposing vertical surfaces on the same tooth

• can be external (extracoronal restoration walls) or internal (walls of proximal box)

the two opposing external (extracoronal) walls in a prep must gradually _____ in an occlusal direction

converge

the two opposing internal (intracoronal) walls must gradually ______ in an occlusal direction

diverge

the inclination of each wall of 3-5 degrees will result in a taper of the preparation of ____ degrees

6-10

the _____ the surface area, the greater the retention

greater

preparation margins must be well supported at how many degrees?

greater than or equal to 90 degrees

bur for breaking interproximal

859 010

chamfer bur

856 014

rounded shoulder bur

856 016

sharp 90 internal bur (also used for occlusal reduction)

6847 014

end cutting bur

10839 014

tooth areas reduction for crowns

cvc cast metal dimensions

1. buccal gingival axial: 0.65 mm (0.5-1.0)

2. mid axial reduction: 1.0 (0.8-1.3)

3. lingual gingival axial: 0.65 (0.5-1.0)

4. occlusal reduction: 1.5 (1.0-1.75)

all ceramic monolithic zirconia

1. buccal gingival axial: 0.65 mm (0.5-1.0)

2. mid axial reduction: 1.0 mm (0.8-1.3)

3. lingual gingival axial: 0.65 (0.5-1.0)

4. occlusal reduction: 1.5(1.0-1.75)

all ceramic layered zirconia (pfz)

1. buccal gingival axial: 1.0 mm (0.5-1.0)

2. mid axial reduction: 1.3 mm (1.0-1.4)

3. lingual gingival axial: 1.0 (0.8-1.1)

4. occlusal reduction: 2.0 mm (1.5-2.5)

metal ceramic (pfm)

1. buccal gingival axial: 1.3 mm (1.0-1.5)

2. mid axial reduction: 1.5 mm (1.3-2.0)

3. lingual gingival axial: 0.65 (0.5-1.0)

4. occlusal reduction: 2.0 mm (1.5-2.5)

most conservative crown prep is…

cvc cast metal

outline requirements

• supragingival margin placement

• including caries and defects

• separation from adjacent teeth

• preservation of adjacent teeth and peridontium

internal requirements

• removing caries

• buildup when necessary

• path of insertion and draw

• preservation of tooth structure planes of reduction

• remove enough tooth structure based on restorative type of material

retention requirements

• height of the vertical axial walls of the preparation

• proper taper convergence angle

• free of undercuts

marginal finish

• margins configuration and angulation for the type of material

• margins well supported terminate on sound tooth structure

• finish line identifiable, continuous, clear, regular

• free of debris

outline should terminate…

supragingival at 0.65 mm (range 0.1-1.0)

clinical outline determining factors

• Caries, Access, Defects, Existing resorations, margins Terminate on sound tooth structure

• preparation wall height

• esthetic factors

• biological width considerations

• proper separation from adjacent teeth

separation from adjacent tooth should be…

greater than or equal to 0.5mm at the gingival margin

POI usually follows the…

long axis of the tooth and parallel to the adjacent proximal contacts

poi of the maxillary teeth is…

slightly buccal

axis of the bur should be ____ to the long axis of the poi

parallel

on mandibular posterior teeth, the side of the bur touches at the height of contour which is the ______ of the lingual surface

middle third

connecting grooves should be at the ____ poi & the _____ of the bur should not be changed

same; angulation

at the correct poi, the mid axial reduction will be ________ the gingivial axial reduction

more than

breaking interproximal contact

• follow the same poi

• follow the gingival scallop, curve around the papilla

• protect adjacent teeth

• maintain a thin layer in contact with adjacent to avoid damage

• look for supragingival margin and gingival separation

proximal axial wall reduction

• do not change angulation of the bur

• only half, no more than 2/3 of the bur diameter

• gingiva axial reduction of 0.65

• pay attention to line angles for proper reduction and taper

marginal finish for a cast metal crown (cvc)

chamfer (1.3 diameter at the tip)

marginal finish for a monolithic zirconia crown

shoulder 90 with round internal

mandibular molar occlusal reduction

• gauging grooves follow the b/l inclination at the proper depth

• remove tooth structure between the grooves

  • removal of tooth structure should be uniform

functional cusps (stamp cusps

• buccal cusps of mandibular posterior teeth

  • lingual (palatal) cusps of maxillary posterior teeth

non-functional cusps

• lingual cusps of mandibular posterior teeth

• buccal cusps of maxillary posterior teeth

for functional cusps, which planes are part of the occlusion?

2nd and 3rd planes

functional cusp 2nd and 3rd planes

• must preserve at least 3.0mm of 1st axial wall height

• 2nd plane should be a gradual transition from the 1st plane

• 3rd plane should be a gradual transition from the 2nd plane

• place 2nd and 3rd from line angle to line angle ONLY

purpose of 2nd and 3rd planes

provide space for restorative materjal and will move back the cusp tips in line with the adjacent teeth and the opposing fossa

non-functional cusp 2nd plane

• must preserve at least 3.0-4.0 mm of 1st axial wall height

• 2nd plane should be a gradual transition from the 1st lpane to bring the cusp tips in line with the adjacent teeth

• place 2nd plane from line angle to line angle only

non-functional cusps have how many planes?

2 planes

if the walls are overtapered, do you still need cusp planes?

no

rounding off sharp occlusal line angles is _____ as 2nd or 3rd cusp planes

not the same

occlusal clearance

the space measured against the opposing teeth (measuring instrument must follow the angulation of the cusp)

how do you measure occlusal clearance on lingual cusps?

bite registration

retention prevents…

removal of the restoration along the poi or the long axis of the tooth preparation

resistance prevents…

dislodgement of the restoration by forces directed in an apical or oblique direction and prevents any movement of the restoration under occlusal forces

indirect cemented restorations ____ have proper retention and resistance form

MUST

• luting cement will not add retention to the crown

CAD/CAM indirect bonded restorations _____ need retention form

DO NOT

• only need proper resistance form to ensure the onlay will stay in position during try-in and bonding

the longer the wall, the ____ the retention

better

ideal taper is?

6 degrees convergance

larger teeth have _____ surface area

more

______ finish is better than _______

diamond; carbide

secondary retentive features include…

grooves, boxes, countersink

when do you place secondary retentive grooves?

• on a wall 90 degrees to the shortest or overtapered wall

• on a wall with proper hright, poi, and taper

• on the longest part of the wall

finish line

• the peripheral extension of a tooth preparation

• the terminal portion of the prepared tooth

• should be clear, continuous, and free of irregularities

margin

• the outer edge of a restoration

• should be well supported and terminates on sound tooth structure

• margin angulation is based on the type of preparation

shoulder bevel

indicated for metal margins only

pfm porcelain margin

shoulder 90 degrees with sharp internal (“butt joint”)

knife edge

• usually contraindicated because it is not good for gingival health

• limited indications for metal margins

provisional

• fixed or removable prosthesis

• designed to enhance esthetics, stabilization, and/or function for a limited period of time, after which is to be replaced by a definitive prosthesis

• assist in determining the therapeutic effectiveness, form, and function of the planned definitive prosthesis

when do we need a provisional

• transitional restoration

• if missing teeth

• evaluation of proposed treatment plan

do provisionals influence the final result?

yes, it must have the exact same parameters as the final restoration

functions of a provisional

• occlusal function

• pulpal function

• maintain periodontal health

• positional stability

• esthetics

• template for a final restoration

occlusal function

• fixes poor esthetics

• reestablish function

  • mastication

  • speece

pulpal protection

• replaces removal of tooth structure

  • exposure of dentin

  • exposure of dentinal tubules

    • contamination of tubules by bacteria

    • increased sensitivity

intra arch stability

includes the variation in tooth position within an arch

inter arch stability

includes the variation in tooth position within 2 different arches

a hyper occluded provisional causes…

• patient discomfort

  • occlusal trauma

  • tmj issues

• tooth movement

  • extrusion of adjacent teeth

  • intrusion of prepared tooth (rarely)

a hypo occluded provisional causes…

• tooth movement

  • extrusion of antagonist teeth

  • extrusion of prepared tooth

open proximal contact causes…

• food impaction

  • patient discomfort

• tooth movement

  • of the prepared tooth

  • of the adjacent tooth

tight proximal contact causes…

• tooth movement

  • of either the prepared tooth or adjacent teeth

    • then creates an open contact with definitive restoration

the provisional allows us to…

• evaluate multiple aspects of the proposed design

  • can change and modify before we move to the final restoration

how long should a provisional last for?

2 weeks

for long term provisionals, what do we need to look out for?

• wear of the provisional resulting in tooth movement

• discoloration of the restorations

• breakage of the restorations

• marginal leakage, leading to caries, sensitivity, pulpal problems

provisionals should be evaluated at least ONCE every month

spend ____ time on provisional and ____ time on the final restoration

more; less

• modifications of the provisional are easy, reversible, and low cost

phonetics & their relationship with provisionals

phonetics affect speech due to the relationship of the teeth to soft tissues

characteristics of a provisional material

• high strength and wear resistance

• ease of manipulation

• dimension stability

• polishability

• color stability

• non-irritating

• poor thermal conductivity

• easy to modify/repair

• cost

• biocompatability

types of prefabricated provisionals

• aluminum shells

• acrylic shells

• celluloid crown forms

• polycarbonate crowns

• stainless steel crowns

• iso-form crowns

types of custom made crowns

• composite resins

• acrylic resins

composition of acrylic resins

• liquid

  • (mma) monomer

  • hydroquinonenone; tertiary amine (initiator)

• powder

  • (pmma) polymer

  • benzoyl peroxide (activator)

advantages of acrylic resins

• good physical properties

• good esthetics

• ease of manipulation

• easily repaired

• low cost

disadvantages of acrylic resins

• exothermic reaction

• polymerization shrinkage

• setting time: 6-9 min

• excessive free monomer

  • can cause allergy

• unpleasant odor

conventional acrylic resins are…

powder/liquid “jet”

acrylic resins for cad/cam

• pmma is industrially processed

  • higher polymerization

  • fewer voids

  • filler particles

• milled

• can be monochromatic or multilayered

to increase the strength of long term provisionals we can…

• cure in a pressure pot to decrease porosity (crack propagation)

• reinforce with fiber

• reinforce with metal

to avoid discoloration for long term provisionals we can…

• cure in a pressure pot to decrease porosity (crack propagation)

• high polish

• use surface sealing materials like BisCover LV

types of composite resins are…

• bisacryl

• light cure resin

composition of bisacryl

• resin

  • dimethylacrylate polymer

  • bisGMA

• filler

  • zirconia silica

  • fumed silica

  • silane

  • pigments

advantages of bisacryl

• low heat

• minimal pulp irritation

• low polymerization shrinkage

• high tensile strength

• color stability

• minimal odor

• polishability

disadvantages of bisacryl

• brittle

• thick oxygen inhibited layer

• limited shades

• no possibility of layering

• difficult to repair

• “one time” provisional

• expensive

light cure resin composition

• triad vlc

  • pmma, urethane dimethacrylate

  • microfine silica

  • camphorquinone

  • amine

• fermit, fermit n, telio

  • polyester urethane dimethylacrylate

  • silica

  • ethilriglycomethacrylate

advantages of light cure resin

• direct technique

• low curing heat

• low polymerization shrinkage

• no mixing

• ease of use and repair

• low odor

• no cement required

disadvantages of light cure resin

• low strength and wear resistance

• plastic after setting

• cannot be polished

• radiolucent

• does not prevent movement of teeth

• water absorption

• not long term

• high cost