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Operative Chapter 5 Reading
Terms in this set (81)
The mechanical alteration of a defective, injured, or diseased tooth so that placement of restorative material re-established normal form and function (including esthetic corrections)
require specific wall forms, depths and marginal forms because of the properties of restorative material
usually composite restorations that require only the removal of the defect without specific uniform depths, wall design, etc.
Concepts for Tooth Prep
1. All unsupported enamel is (normally) removed.
2. The fault, defect or caries is removed
3. The remaining tooth structure is left as strong as possible
4. the underlying pulpal tissue is protected
5. the restorative material is retained in a strong, esthetic and functional manner
Fractures or missing tooth structure
Compromised function or pain
Restore form or function
(special positioning, etc)
Caries control treatment plan
Initial treatment plan, may be especially needed for high risk patients
Amalgam restoration requires a prep that ensures what?
1. retention of material
2. strength of material (bulk thickness and marginal edge)
Indirect castmetal restoration requires a prep that:
1. provides draw to provide seating of the restoration
2. has a beveled cavosurface configuration
3. that retains the casting by the degree of parallelism of the prepared walls
Original lesion on the tooth
1. in enamel pits and fissures
2. on enamel smooth surfaces
3. on root surfaces
Where do caries tend to form?
Less often on lobes
More often in pits and fissures
If in dentin, it spreads at the DEJ
Smooth Surface Caries
Originates on an area of enamel that is habitually unclean and often covered by plaque. Cone in Enamel to Cone in Dentin
When caries spreads along the DEJ and then extends backwards into the enamel
When caries cone in enamel is as large or larger than cone in dentin
caries that remains in a tooth prep either by accident or on purpose
NOT ACCEPTABLE if left at DEJ or on prepared enamel wall.
occurs at junction of restoration and tooth and can progress under the restoration
The first evidence of caries activity on enamel, this is REVERSIBLE!!!
"White spot lesion"
Does NOT extend into dentin
This is IRREVERSIBLE
The enamel surface is broken and usually the lesion goes into the dentin
Disease that rapidly damages the tooth
Slow, may be arrested after several active phases.
"Extension for Prevention"
GV Black believed that restoration should be extended to prevent recurrent caries.
We do NOT believe this anymore.
removal of a shallow fissure or pit in enamel to crease a smooth self-cleansing surface.
Used for preventative, no longer used
Affected vs Infected Dentin
Affected: no bacteria, collagen matrix is intact, is remineralizable and should be preserved
Infected: bacteria present, collagen is irreversibly denatured. Not remineralizable and must be removed.
tooth surface loss resulting from forces of friction between teeth and external objects
wear or loss of tooth surface by chemico-mechanical action (acids, etc)
mechanical wear of incisal or occlusal surface due to tooth-tooth contacts
microfractures at cervical area as tooth flexes under loads
Fractures can be...
1. Incomplete, not involving pulp ("greenstick")
2. Complete, not involving pulp (restoration indicated)
3. Fracture involving pulp
Severe pain, either root canal or extraction
4. Non-hereditary enamel hypoplasia
Ameloblasts injured during development
enamel is defective in form or calcification (hereditary)
only dentin is defective, and so enamel is weakly attached and lost early (hereditary)
involves ONE surface
Involves TWO surfaces
Involves THREE or MORE surfaces
does not extend to tooth surface
parallel to long axis of tooth
perpendicalar to long axis of tooth
occlusal of the pulp
prepared surface that extends to external tooth surface
prepared wall that is horizonal and perpendicular to the occlusal forces that are directed occlusogingivally
(pulpal and gingival floors)
portion of prepared external wall consisting of dentin
this is where mechanical retention features may be located
angle of tooth structure formed by the junction of a prepared wall and the external surface of the tooth
strongest enamel margin
1. formed by full-length enamel rods whose inner ends are on sound dentin, and
2. these rods are buttressed onthe preparation side by progressively shorter rods whose outer ends have been cut off but whose inner ends are on sound dentin.
intracoronal tooth prep
has internal and external prep walls, much of the crown is not involved
extracoronal tooth prep
results from removal of most of the enamel
Class I Prep
pit and fissure preps
1. on occulusal surface of molars and premolars
2. occlusal 2/3 of the facial and lingual surfaces of molars
3. lingual surface of maxillary incisors
Class II Prep
proximal surface of posterior teeth
Class III Prep
proximal surface of anterior teeth that do NOT involve the incisal angle
Class IV Prep
proximal surface of anterior teeth that DO involve the incisal edge
Class V Prep
gingival third of facial or lingual surface of all teeth
Class VI Prep
on the incisal edges of anterior teeth
on the occlusal cusp tips of posterior teeth
Initial Tooth Preparation
1. Outline form and initial depth
2. Primary resistance form
3. Primary retention form
4. Convenience form
Final Tooth Prep
5. Removal of any remaning infected dentin or old restorative material
6. pulp protection
7. secondary resistance and retention forms
8. finishing external walls
9. cleaning, inspecting and desensitizing
Start prep when?
After you isolate the tooth! Dry, dry, dry!
placing preparation margins in positions they will occupy in the final prep
preparing an initial depth of 0.2 to 0.5 mm pulpally of the DEJ position
Principles of Outline form
1. all unsupported or weak enamel should be removed
2. all faults should be included
3. all margins should be placed in a position to allow finishing of the margins of the restoration
Features of a proper outline form
1. preserve cuspal strength
2. preserve marginal ridge strength
3. minimize faciolingual extensions
4. connecting two close defects
5. restrict the depth of the prepartion into the dentin
Primary resistance form
the shape and placement of the prep walls that best enable the remaining tooth structure and restoration to withstand (without fracture) masticatory forces.
(relatively horizonal gingival and pulpal floorrs)
Principles of primary resistance form
1. use a box shape with a horizontal floor
2. restrict the extension of the external walls to keep a strong cusp
3. Have slight rounding of internal line angles to reduce stress
4. reduce and cover weak cusps
5. provide thickness of restorative material to prevent its fracture
6. bond the material to the tooth structure when appropriate
When to reduce cusps?
Possible: when the outline form has extended half the distance from a primary groove to a cusp tip.
Usually: when the outline form has extended 2/3 the distance from a primary groove to a cusp tip.
What determines the resistance form?
Amount of tooth structure remaining
type of restorative material being used
Features of resistance form:
1. relatively horizontal floors
2. box-like shape
3. inclusion of weakened tooth structure
4. preservation of cusps and marginal ridges
5. rounded internal line angle
6. adequate thickness of restorative materials
7. reduction of cusps for capping when indicated
Primary retention form
the form or shape of the conventional prep that prevents displacement or removal of the restoraion by tipping or lifting forces (for non-bonded restorations)
(usually retention and resistance forms are done at the same time)
Primary retention form principles
Varies depending on material
Need walls that converge occlusally for Class I & II
Need walls that diverge occlusally for Class III & V
You can increase the amount of enamel you edge to increase the bond strength
form that provides for adequate observation, accessibility and ease of operation in prepping and restoring a tooth.
Final tooth prep
remove any remaining enamel pit or fissure, infected dentin or old restorative material.
You may want to leave affected dentin.
May be different color, but it won't be soft
What if there is a small amount of carious material in a prepped pulpal or axial wall?
Just remove this little part and leave a small rounded, concave area in the wall.
How to remove harder, heavily discolored dentin?
Spoon excavators, round steel burs at very low speed, or round carbid burs at high speeds
placement of liners and bases to protect pulp from the restorative material, heat from the rotary instruments and forces coming through dentin
Liners for pulp
resin modified glass ionomer
Bases for pulp
zinc oxide (eugenol)
Secondary resistance/retention forms
vertically oriented retention grooves.
vertically oriented retention grooves for Class III & V in amalgam
Finishing External Walls, why?
1. create optimal marginal junction
2. afford a smooth marginal junction
3. provide maximal strenght of tooth and restorative material
What to consider when finishing external walls?
1. direction of enamel rods
2. support of enamel rods at DEJ
3. type of restorative material being used
4. location of margin
5. degree of smoothness or roughness desired
Features of external walls
1. cavosurface angle
2. degree of smoothness or roughness of wall
Beveling External Walls
A prep technique for some materials
1. produces a stronger enamel margin
2. permits a marginal seal in undersized casting
3. provides marginal metal that is more easily burnished
4. assists in adapting the gingival margins of castings
(usually for larger restorations with increased retention needs)
What does excessive drying cause?
Odontoblasts to be aspirated into dentinal tubules
What do we leave in composite preps?
A smear layer that we then etch
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