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cavity preparation for composite Flashcards

1
Q

What is the definition o conservative approach?

A
  • minimally invasive approach that focus on detecting, diagnosing &
    removing only damaged structure, preserving the remaining healthy
    tooth structure and emphasizing the concepts of prevention and
    remineralization during restorative procedure
  • it refers to all procedures carried out to preserve the integrity of teeth and the masticatory system
  • prevention is the theme applied nowadays in operative dentistry rather than extension for prevention.
  • the concept of “sealing for prevention”; e.g., using pit and fissure sealants
  • Black’s statement: “The day is surely coming when we will be engaged in practicing preventive, rather than reparative dentistry”
  • the classic cavity preparation has been modified into what is known as “adhesive cavity design”
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2
Q

What are the advantages of conservative adhesive cavity design?

A
  • preservation of healthy tooth structure
  • decreased irritation of dentin-pulp complex and investing tissues
  • decreased fractured tooth and/or the restorations
  • decreased displayed area of the restorations
  • easier, quicker and standardized procedures
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3
Q

What are the steps of cavity preparation?

A
  • obtaining of the outline form
  • obtaining of the resistance and retention forms
  • obtaining of the required convenience form
  • removal of the remaining carious dentin
  • finishing of the cavity walls and margins
  • performing the toilet of the cavity
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4
Q

What is cavity outline?

A
  • shape of boundaries of the completed cavity
  • the external outline describes the external marginal boundaries
  • the internal outline describes the shape of the internal form of the preparation
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5
Q

What is the aim of obtaining outline form?

A

place the margins of cavities in sound enamel at areas not carious and less stress-bearing

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6
Q

What are the most important factors that govern the extension of the outline of the cavity?

A

carious lesion and convenience of prepared cavity to be easily seen, approached and restored

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7
Q

What is the cavity outline limited to?

A

defective enamel and dentin

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8
Q

What are the essentials of outline form in composite cavity preparation?

A
  • all carious enamel and dentin must be included in the outline
  • all pits and fissures which are deeper than 1/3 the enamel thickness should NOT be included in the outline (but rather sealed with pit & fissure sealant or treated with enameloplasty)
  • all weak or undermined enamel must be eliminated and included in the outline
  • adjacent cavities, approaching to each other should ONLY be joined when the intervening tooth structures are carious, undermined, weak (less than 1mm) and if crossed by a fissure (sealed with pit & fissure sealant/ enameloplasty) this is specially considered with oblique and transverse ridges
  • all severely weakened cusps and ridges that are subjected to occlusal
    forces must be reduced and included in the outline to be protected with appropriate restoration (cusp capping)
  • the outline form must be in the form of harmonious sweeping curves to avoid stress concentration
    and provide better esthetic
  • the cavo-surface angle given correct angulation according to
    the location of the margin, composite CSA is 90degrees ( butt Joint) in margins subjected to direct force + gingival margins and beveled in margins not subjected to direct force (ex. labial)
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9
Q

What is undermined enamel?

A

enamel not supported by sound dentin

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10
Q

What is pits and fissure sealing?

A
  • indicated in case of deep grooves liable to food stagnation and difficult to clean in recently erupted permanent molars
  • using pit and fissure sealing instead of preparing them to be included in the outline has preserved sound tooth structures
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11
Q

What is the definition of preventive resin restorations?

A

a preparation that eliminates the carious lesion only and restore it with a resin composite material with sealing of the remaining non-carious pits and fissures by pit & fissure sealant

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12
Q

What is simple box preparation?

A
  • small proximal lesion without including occlusal fissures
  • outline form is rounded for resin composite
  • with resin composite, retention is based on the micro-mechanical bonding
  • if there is sound occlusal fissure + proximal Caries –> simple box preparation + fissure sealant to prevent any stagnation area
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13
Q

What is resistance form?

A

design features in the cavity preparation which allows both tooth and restoration to resist the functional stresses of mastication without fracture

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14
Q

How is resistance form obtained for walls and floor?

A
  • walls: according to enamel rod direction, parallel to direction of enamel rods
  • floor: smooth and according to direction of the force, might not be even according to caries extension & removal.
  • proper depth and width to provide bulk of the restoration
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15
Q

What is the minimum sufficient bulk for composite?

A

1-1.5mm

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16
Q

What does bonding to tooth structures do?

A

reinforce the remaining weak tooth structure provided that it is not too weak, thin or undermined which need reduction and coverage with strong restorative material

17
Q

Why do line and point angles have to be rounded?

A

to increase the wettability and adaptation of the viscous resin composite and is done by using suitable burs as round bur & burs
with rounded end (330, 245, 246, etc.)

18
Q

What determines CSA?

A

according to the site of the margin

19
Q

What should be down to the CSA if at non-stress bearing area (as labial surface)?

A

bevel

20
Q

What should be down to the CSA if at stress bearing area (as occlusal of posterior teeth)?

A

butt joint (90 degrees)

21
Q

What should be down to the CSA if at gingival margin?

A

butt joint (90 degrees)

22
Q

What is retention form?

A
  • design features in the cavity which enables it to retain the restoration securely in function and prevent its displacement
  • it is provided with micromechanical means of retention (bondodontics)
  • no macro-mechanical means of retention are needed
23
Q

What is the correlation between resistance and retention?

A

bonding to tooth structure reinforce the remaining weak tooth structure,
provided that it is not too weak, by mono-block concept due to absence of wedging action by the restoration

24
Q

What is th definition of convenience form?

A
  • features in the prepared cavity making it more conveniently seen,
    approached and/or restored
  • just to improve the visibility & approach to the cavity during preparation & restoration
25
Q

What are examples of precise tools?

A
  • micro-sized burs: help prepare smaller sized, more conservative
    cavities
  • magnification (dental loupes and microscopes): improve vision for
    minute defects to allow for precise preparation for small defects without additional overcutting for vision
  • visibility (fiber-optic handpieces & loupes with auxiliary light): Increase visibility and illumination
  • restorative material: new restorative materials that can treat
    defective lesions without the need of excessive cutting of tooth structure (ex. pit and fissure sealants)
26
Q

What are loupes?

A
  • similar in appearance to eyeglasses % allow a
    magnification in the range of 2x-5x.
  • they are sometimes associated with lighting by single spot halogen or fiberoptic lamps
  • recently xenon lamps are used
27
Q

What are microscopes?

A
  • allow a magnification in the range of 10x-25x
  • the majority of procedures are undergone with range of 10x-12x
  • frequent adjustments wall mounted or ceiling mounted
28
Q

What happens during removal of remaining carious dentn?

A
  • providing sound dentin is very critical to achieve successful and durable bonding to it
  • many tools are used to discriminate between sound and carious dentin and the simplest way is using caries detection dyes (CDD)
  • in posterior teeth, discolored sound dentin can be left as it doesn’t affect esthetic while in anterior teeth, discolored sound dentin must be removed or masked
    by opaquer to avoid esthetic impairment
29
Q

What are the concepts of caries removal and excavation?

A
  • complete caries excavation
  • stepwise excavation
  • partial caries removal
30
Q

What is complete caries excavation concept?

A
  • conventional strategy set by G.V. Black
  • involves removal of soft demineralized dentine (soft infected dentin) and (firm affected dentin) before placing the restoration
  • this tissue is heavily infected with bacteria and is removed using a drill
    or sharp spoon like instruments (excavators), in order to stop the decay (carious) process
31
Q

What is stepwise excavation concept?

A
  • involves the removal of carious tissue in stages
  • removal of peripheral demineralized dentin and the superficial parts of the necrotic and demineralized central dentine
  • leaving the softened and wet tissue on the pulp wall
  • base of the cavity is lined and then sealed with long temporary restoration for 2-12 months
  • re-entry to put final restoration
32
Q

What is partial caries removal concept?

A
  • conservative approach strategy
  • this technique is based on the concept that the carious process is
    guided by caries activity in the biofilm, therefore, this process could be stopped simply by sealing the cavity
  • after partial excavation, the base of the cavity may be lined with calcium hydroxide (although this is not essential) and the cavity is filled with a permanent restorative material, with no re-entry in the cavity
33
Q

What is done in finishing of cavity walls and margins?

A
  • finishing of the enamel margin is a very crucial step to eliminate the
    microcracked enamel margin due to the cutting procedure
  • if the microcracks are left unfinished –> propagation of the cracks at the margin –>leaky margin
  • beveled cavo-surface angle: to a 45° short bevel
34
Q

What are the advantages of CSA 45 degree bevel?

A
  • increases the surface area and surface energy of enamel
  • exposes the ends of enamel rods rather than the sides –> more retentive etching pattern with micro- and macro-pores in enamel
  • gradual color degradation between tooth and restoration = improve esthetics
35
Q

What is the width of bevel?

A
  • usually 1 -1.5 mm
  • width could be increased based on the retention requirements, e.g. in
    fractured class IV where the etched enamel will be the main retentive mode
36
Q

When is bevel contraindicated?

A
  • stress-bearing areas, e.g. in occlusal surface of posterior teeth to avoid chipping of composite in such areas
  • gingival wall to avoid chipping of thin enamel at the margin
37
Q

What is the toilet of the cavity composed of?

A
  • includes the removal of any debris, dentin chips, bacteria, providing a
    clean dry cavity and conditioning the cavity surface to receive and retain the restoration
  • before application of resin composite the tooth structures (enamel & dentin) must be treated to provide strong bonding between them.
  • different adhesive approaches are now available to provide accepted and durable bonding to tooth structure
38
Q

What is the most recommended protocol for adhesive approaches?

A

selective etch technique

39
Q

What are the name of some adhesive approaches?

A
  • etch and rinse approach
  • self-etch approach
  • glass ionomer approach
  • selective etch technique

operative (6 decks)

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